Clinical assessment of peripheral perfusion to predict postoperative complications after major abdominal surgery early: a prospective observational study in adults

Low postoperative mitochondrial oxygen tension is an early marker of acute kidney injury after cardiac surgery: A prospective observational study

BACKGROUND

Dissociation between the micro- and macrocirculation as well as the lack of specificity of current markers to signal impaired tissue oxygenation complicate the timely diagnosis and treatment of tissue hypoperfusion to prevent acute kidney injury (AKI) after cardiac surgery. The newly developed non-invasive technique to measure the mitochondrial oxygenation (mitoPO2) is currently the most downstream bedside marker of tissue oxygenation. The aim was to investigate mitoPO2 as an early marker of postoperative development of AKI.

METHODS

In a prospective observational study, postoperative mitochondrial oxygen tension was measured to detect AKI (defined by KDIGO) in patients undergoing cardiac surgery.

RESULTS

Of 50 included patients, 44 patients had analyzable mitoPO2 signal. 5 patients developed AKI. MitoPO2 at ICU admission was 16(13.8-24.6)mmHg in patients who developed AKI vs 63.4(37.5-77.9) mmHg in patients without AKI (p < 0.001). MitoPO2 predicted AKI (ROC 0.95 (0.89-1.0) with an optimal cut-off value of 30 mmHg (OR 4.4, CI 2.8-6.0, p < 0.001). Also, longer period of time under the mitoPO2 threshold predicted AKI with an AUROC of 0.91(0.80-1.00). In all patients, a decreased mitoPO2 occurred 4 h earlier than an clinically relevant increase in serum lactate. Other markers of tissue hypoperfusion, did not differ between patients with and without AKI.

CONCLUSIONS

A mitoPO2 value below 30 mmHg at ICU admission as well as the duration below this threshold indicate the development of AKI in cardiac surgery patients, occurring earlier than an increase in lactate above the normal range.

Research Progress on the Measurement Methods and Clinical Significance of Capillary Refill Time

The monitoring of peripheral circulation, as indicated by the capillary refill time, is a sensitive and accurate method of assessing the microcirculatory status of the body. It is a widely used tool for the evaluation of critically ill patients, the guidance of therapeutic interventions, and the assessment of prognosis. In recent years, there has been a growing emphasis on microcirculation monitoring which has led to an increased focus on capillary refill time. The International Sepsis Guidelines, the American Academy of Pediatrics, the World Health Organization, and the American Heart Association all recommend its inclusion in the evaluation of the system in question. Furthermore, the methodology for its measurement has evolved from a traditional manual approach to semiautomatic and fully automatic techniques. This article presents a comprehensive overview of the current research on the measurement of capillary refill time, with a particular focus on its clinical significance. The aim is to provide a valuable reference for clinicians and researchers and further advance the development and application of microcirculation monitoring technology.

Application of microcirculatory indicators in predicting the prognosis of patients with septic shock

Objective

The aim of this study is to investigate the predictive value of indicators associated with microcirculation, capillary refill time (CRT), perfusion index (PI), and mottling score, on the prognosis of patients with septic shock.

Method

A retrospective clinical study was conducted encompassing 78 patients diagnosed with septic shock and admitted to the Department of Critical Care Medicine at our hospital from January 2019 to January 2022. The study collated the clinical data of these patients, focusing on macrocirculatory hemodynamic parameters and microcirculatory indices. The parameters of interest were recorded at 0, 6, 24, and 48 h post-admission, including heart rate, mean arterial pressure (MAP), venous-to-arterial carbon dioxide partial pressure difference, superior vena cava oxygen saturation, lactic acid (LAC), CRT, PI, and mottling score. The enrolled patients were stratified into two cohorts based on the 28-day mortality rate: a survival group and a mortality group. A non-parametric statistical test was employed to compare the CRT, PI, and mottling score between the two groups. Furthermore, the predictive value of these microcirculatory indicators for mortality in septic shock patients was assessed using receiver operating characteristic (ROC) curve analysis. This methodology allowed for the evaluation of the prognostic accuracy of CRT, PI, and mottling score as indicators for mortality in the context of septic shock.

Results

The vasoactive drug dose, PI, LAC, mottling score, and CRT upon admission in the survival group were significantly better than those in the mortality group at hour 6 of treatment, hour 24 of treatment, and hour 48 of treatment (P < 0.05). The predictive value of the three microcirculatory indicators at various time points was highest for the Perfusion Index (PI) at 48 h of treatment, the mottling score at 24 h of treatment, and the Capillary Refill Time (CRT) upon admission. The Area Under the Curve (AUC) for PI at 48 h of treatment was 0.941 (0.885-0.996), with a sensitivity of 90.9 % and a specificity of 94.1 %. For the mottling score at 24 h of treatment, the AUC was 0.889 (0.805-0.972), with a sensitivity of 82.4 % and a specificity of 88.6 %. The AUC for CRT upon admission was 0.872 (0.788-0.956), with a sensitivity of 91.2 % and a specificity of 77.3 %. Among the three indicators: PI, mottling score, and CRT, PI at hour 48 of treatment had the highest predictive value for the prognosis of patients with septic shock.

Conclusion

Microcirculatory indicators have specific predictive value for the prognosis of patients with septic shock.

Construction and validation of a clinical prediction model for sepsis using peripheral perfusion index to predict in-hospital and 28-day mortality risk

Sepsis is a clinical syndrome caused by infection, leading to organ dysfunction due to a dysregulated host response. In recent years, its high mortality rate has made it a significant cause of death and disability worldwide. The pathophysiological process of sepsis is related to the body's dysregulated response to infection, with microcirculatory changes serving as early warning signals that guide clinical treatment. The Peripheral Perfusion Index (PI), as an indicator of peripheral microcirculation, can effectively evaluate patient prognosis. This study aims to develop two new prediction models using PI and other common clinical indicators to assess the mortality risk of sepsis patients during hospitalization and within 28 days post-ICU admission. This retrospective study analyzed data from sepsis patients treated in the Intensive Care Unit of Peking Union Medical College Hospital between December 2019 and June 2023, ultimately including 645 patients. LASSO regression and logistic regression analyses were used to select predictive factors from 35 clinical indicators, and two clinical prediction models were constructed to predict in-hospital mortality and 28-day mortality. The models' performance was then evaluated using ROC curve, calibration curve, and decision curve analyses. The two prediction models performed excellently in distinguishing patient mortality risk. The AUC for the in-hospital mortality prediction model was 0.82 in the training set and 0.73 in the validation set; for the 28-day mortality prediction model, the AUC was 0.79 in the training set and 0.73 in the validation set. The calibration curves closely aligned with the ideal line, indicating consistency between predicted and actual outcomes. Decision curve analysis also demonstrated high net benefits for the clinical utility of both models. The study shows that these two prediction models not only perform excellently statistically but also hold high practical value in clinical applications. The models can help physicians accurately assess the mortality risk of sepsis patients, providing a scientific basis for personalized treatment.

Perspectives for capillary refill time in clinical practice for sepsis

BACKGROUND

Capillary refill time (CRT) is defined as the time taken for color to return to an external capillary bed after pressure is applied to cause blanching. Recent studies demonstrated the benefits of CRT in guiding fluid therapy for sepsis. However, lack of consistency among physicians in how to perform and interpret CRT has led to a low interobserver agreement for this assessment tool, which prevents its availability in sepsis clinical settings.

OBJECTIVE

To give physicians a concise overview of CRT and explore recent evidence on its reliability and value in the management of sepsis.

RESEARCH DESIGN

A narrative review.

RESULTS

This narrative review summarizes the factors affecting CRT values, for example, age, sex, temperature, light, observation techniques, work experience, training level and differences in CRT measurement methods. The methods of reducing the variability of CRT are synthesized. Based on studies with highly reproducible CRT measurements and an excellent inter-rater concordance, we recommend the standardized CRT assessment method. The threshold of normal CRT values is discussed. The application of CRT in different phases of sepsis management is summarized.

CONCLUSIONS

Recent data confirm the value of CRT in critically ill patients. CRT should be detected by trained physicians using standardized methods and reducing the effect of ambient-related factors. Its association with severe infection, microcirculation, tissue perfusion response, organ dysfunction and adverse outcomes makes this approach a very attractive tool in sepsis. Further studies should confirm its value in the management of sepsis.

IMPLICATIONS FOR CLINICAL PRACTICE

As a simple assessment, CRT deserves more attention even though it has not been widely applied at the bedside. CRT could provide nursing staff with patient's microcirculatory status, which may help to develop individualized nursing plans and improve the patient's care quality and treatment outcomes.

Early peripheral perfusion monitoring in septic shock

Septic shock is a frequent critical clinical condition and a leading cause of death in critically ill individuals. However, it is challenging to identify affected patients early. In this article, we discuss new perspectives on the methods and uses of peripheral perfusion monitoring, considering the concept of a dysregulated response. Physical examination, and visual and ultrasonographic techniques are used to measure peripheral microcirculatory blood flow to reflect tissue perfusion. Compared with other monitoring techniques, peripheral perfusion monitoring has the benefits of low invasiveness and good repeatability, and allows for quick therapeutic judgments, which have significant practical relevance. Peripheral perfusion monitoring is an effective tool to detect early signs of septic shock, autonomic dysfunction, and organ damage. This method can also be used to evaluate treatment effectiveness, direct fluid resuscitation and the use of vasoactive medications, and monitor vascular reactivity, microcirculatory disorders, and endothelial cell damage. Recent introductions of novel peripheral perfusion monitoring methods, new knowledge of peripheral perfusion kinetics, and multimodal peripheral perfusion evaluation methods have occurred. To investigate new knowledge and therapeutic implications, we examined the methodological attributes and mechanisms of peripheral perfusion monitoring, in this study.

Peripheral perfusion index of pulse oximetry in adult patients: a narrative review

The peripheral perfusion index (PI) is derived from pulse oximetry and is defined as the ratio of the pulse wave of the pulsatile portion (arteries) to the non-pulsatile portion (venous and other tissues). A growing number of clinical studies have supported the use of PI in various clinical scenarios, such as guiding hemodynamic management and serving as an indicator of outcome and organ function. In this review, we will introduce and discuss this traditional but neglected indicator of the peripheral microcirculatory perfusion. Further clinical trials are required to clarify the normal and critical values of PI for different monitoring devices in various clinical conditions, to establish different standards of PI-guided strategies, and to determine the effect of PI-guided therapy on outcome.

The Use of the Perfusion Index to Predict Post-Induction Hypotension in Patients Undergoing General Anesthesia: A Systematic Review and Meta-Analysis

Post-induction hypotension (PIH) is a common and potentially serious complication of general anesthesia. This meta-analysis (Prospero registration number: CRD42024566321) aimed to evaluate the predictive efficacy of the perfusion index (PI) for PIH in patients undergoing general anesthesia. A comprehensive literature search was performed using multiple electronic databases (Google Scholar, EMBASE, Cochrane Library, and MEDLINE). Studies involving adult patients undergoing general anesthesia, with the PI measured before anesthesia induction and reporting PIH incidence, were included. The primary outcome was the diagnostic accuracy of the PI in predicting the probability of PIH. The secondary outcome was the pooled PIH incidence. Eight studies with 678 patients were included. The pooled incidence of PIH was 44.8% (95% confidence interval [CI]: 29.9%-60.8%). The combined sensitivity and specificity of the PI for predicting PIH were 0.84 (95% CI: 0.65-0.94) and 0.82 (95% CI: 0.70-0.90), respectively. The summary receiver operating characteristic (sROC) analysis revealed an area under curve of 0.89 (95% CI: 0.86-0.92). The Deek's funnel plot asymmetry test indicated no significant publication bias. The PI demonstrates high predictive efficacy for PIH in patients undergoing general anesthesia, indicating that it can be a valuable tool for identifying those at risk of PIH.

Peripheral perfusion index stratifies risk in patients with intraoperative anemia: A multicentre cohort study

STUDY OBJECTIVE

Evidence for red blood cell (RBC) transfusion thresholds in the intraoperative setting is limited, and current perioperative recommendations may not correspond with individual intraoperative physiological demands. Hemodynamics relevant for the decision to transfuse may include peripheral perfusion index (PPI). The objective of this prospective study was to assess the associations of PPI and hemoglobin levels with the risk of postoperative morbidity and mortality.

DESIGN

Multicenter cohort study.

SETTING

Bispebjerg and Hvidovre University Hospitals, Copenhagen, Denmark.

PATIENTS

We included 741 patients who underwent acute high risk abdominal surgery or hip fracture surgery.

INTERVENTIONS

No interventions were carried out.

MEASUREMENTS

Principal values collected included measurements of peripheral perfusion index and hemoglobin values.

METHODS

The study was conducted using prospectively obtained data on adults who underwent emergency high-risk surgery. Subjects were categorized into high vs. low subgroups stratified by pre-defined PPI levels (PPI: > 1.5 vs. < 1.5) and Hb levels (Hb: > 9.7 g/dL vs. < 9.7 g/dL). The study assessed mortality and severe postoperative complications within 90 days.

MAIN RESULTS

We included 741 patients. 90-day mortality was 21% (n = 154), frequency of severe postoperative complications was 31% (n = 231). Patients with both low PPI and low Hb had the highest adjusted odds ratio for both 90-day severe postoperative complications (2.95, [1.62-5.45]) and 90-day mortality (3.13, [1.45-7.11]). A comparison of patients with low PPI and low Hb to those with high PPI and low Hb detected significantly higher 90-day mortality risk in the low PPI and low Hb group (OR 8.6, [1.57-162.10]).

CONCLUSION

High PPI in acute surgical patients who also presents with anemia was associated with a significantly better outcome when compared with patients with both low PPI and anemia. PPI should therefore be further investigated as a potential parameter to guide intraoperative RBC transfusion therapy.

Pulsatile flow increases METTL14-induced m 6 A modification and attenuates septic cardiomyopathy: an experimental study

INTRODUCTION

Septic cardiomyopathy is a sepsis-mediated cardiovascular complication with severe microcirculatory malperfusion. Emerging evidence has highlighted the protective effects of pulsatile flow in case of microcirculatory disturbance, yet the underlying mechanisms are still elusive. The objective of this study was to investigate the mechanisms of N 6 -methyladenosine (m 6 A) modification in the alleviation of septic cardiomyopathy associated with extracorporeal membrane oxygenation (ECMO)-generated pulsatile flow.

METHODS

Rat model with septic cardiomyopathy was established and was supported under ECMO either with pulsatile or non-pulsatile flow. Peripheral perfusion index (PPI) and cardiac function parameters were measured using ultrasonography. Dot blot assay was applied to examine the m 6 A level, while qRT-PCR, Western blot, immunofluorescence, and immunohistochemistry were used to measure the expressions of related genes. RNA immunoprecipitation assay was performed to validate the interaction between molecules.

RESULTS

The ECMO-generated pulsatile flow significantly elevates microcirculatory PPI, improves myocardial function, protects the endothelium, and prolongs survival in rat models with septic cardiomyopathy. The pulsatile flow mediates the METTL14-mediated m 6 A modification to zonula occludens-1 (ZO-1) mRNA (messenger RNA), which stabilizes the ZO-1 mRNA depending on the presence of YTHDF2. The pulsatile flow suppresses the PI3K-Akt signaling pathway, of which the downstream molecule Foxo1, a negative transcription factor of METTL14, binds to the METTL14 promoter and inhibits the METTL14-induced m 6 A modification.

CONCLUSION

The ECMO-generated pulsatile flow increases METTL14-induced m 6 A modification in ZO-1 and attenuates the progression of septic cardiomyopathy, suggesting that pulsatility might be a new therapeutic strategy in septic cardiomyopathy by alleviating microcirculatory disturbance.

Association between peripheral perfusion index and postoperative acute kidney injury in major noncardiac surgery patients receiving continuous vasopressors: a post hoc exploratory analysis of the VEGA-1 trial

BACKGROUND

The peripheral perfusion index is the ratio of pulsatile to nonpulsatile static blood flow obtained by photoplethysmography and reflects peripheral tissue perfusion. We investigated the association between intraoperative perfusion index and postoperative acute kidney injury in patients undergoing major noncardiac surgery and receiving continuous vasopressor infusions.

METHODS

In this exploratory post hoc analysis of a pragmatic, cluster-randomised, multicentre trial, we obtained areas and cumulative times under various thresholds of perfusion index and investigated their association with acute kidney injury in multivariable logistic regression analyses. In secondary analyses, we investigated the association of time-weighted average perfusion index with acute kidney injury. The 30-day mortality was a secondary outcome.

RESULTS

Of 2534 cases included, 8.9% developed postoperative acute kidney injury. Areas and cumulative times under a perfusion index of 3% and 2% were associated with an increased risk of acute kidney injury; the strongest association was observed for area under a perfusion index of 1% (adjusted odds ratio [aOR] 1.32, 95% confidence interval [CI] 1.00-1.74, P=0.050, per 100%∗min increase). Additionally, time-weighted average perfusion index was associated with acute kidney injury (aOR 0.82, 95% CI 0.74-0.91, P<0.001) and 30-day mortality (aOR 0.68, 95% CI 0.49-0.95, P=0.024).

CONCLUSIONS

Larger areas and longer cumulative times under thresholds of perfusion index and lower time-weighted average perfusion index were associated with postoperative acute kidney injury in patients undergoing major noncardiac surgery and receiving continuous vasopressor infusions.

CLINICAL TRIAL REGISTRATION

NCT04789330.

Prognostic value of capillary refill time in adult patients: a systematic review with meta-analysis

PURPOSE

Acute circulatory failure leads to tissue hypoperfusion. Capillary refill time (CRT) has been widely studied, but its predictive value remains debated. We conducted a meta-analysis to assess the ability of CRT to predict death or adverse events in a context at risk or confirmed acute circulatory failure in adults.

METHOD

MEDLINE, EMBASE, and Google scholar databases were screened for relevant studies. The pooled area under the ROC curve (AUC ROC), sensitivity, specificity, threshold, and diagnostic odds ratio using a random-effects model were determined. The primary analysis was the ability of abnormal CRT to predict death in patients with acute circulatory failure. Secondary analysis included the ability of CRT to predict death or adverse events in patients at risk or with confirmed acute circulatory failure, the comparison with lactate, and the identification of explanatory factors associated with better accuracy.

RESULTS

A total of 60,656 patients in 23 studies were included. Concerning the primary analysis, the pooled AUC ROC of 13 studies was 0.66 (95%CI [0.59; 0.76]), and pooled sensitivity was 54% (95%CI [43; 64]). The pooled specificity was 72% (95%CI [55; 84]). The pooled diagnostic odds ratio was 3.4 (95%CI [1.4; 8.3]). Concerning the secondary analysis, the pooled AUC ROC of 23 studies was 0.69 (95%CI [0.65; 0.74]). The prognostic value of CRT compared to lactate was not significantly different. High-quality CRT was associated with a greater accuracy.

CONCLUSION

CRT poorly predicted death and adverse events in patients at risk or established acute circulatory failure. Its accuracy is greater when high-quality CRT measurement is performed.

Mottling in Septic Shock: Ethnicity and Skin Color Matter

BACKGROUND

Skin mottling as a clinical perfusion marker in septic shock is significantly associated with severity and outcome in white-skinned population and its validity as a clinical sign in dark-skinned population is not known. The objectives of this study were to evaluate mottling in septic shock in the Indian ethnic population who has different skin color as compared to the white-skinned population and to assess mottling as an outcome predictor with capillary refill time (CRT) and other biochemical parameters which are the established clinical markers of perfusion in septic shock.

MATERIALS AND METHODS

We conducted a prospective observational study of patients with skin color categories 21-34 on the von Luschan scale or Fitzprick type IV-VI who had septic shock needing a high dose of norepinephrine ≥0.2 μg/kg/min after fluid optimization. The study was conducted in a mixed medical-surgical ICU over 12 months. Two blinded experts (a Dermatologist and a plastic surgeon) independently classified the skin type, validated the occurrence of mottling, and scored mottling in our patients. We recorded the demographics, hemodynamic variables, and mottling score and observed the incidence of mottling and its correlation with predictors of the severity of septic shock. We also compared CRT, arterial lactate, central venous oxygen saturation, and venoarterial PCO2 gap with occurrence of mottling in septic shock patients.

RESULTS

We included 108 patients with age 61 ± 16 years. Mean Sequential Organ Failure Assessment (SOFA) and Acute Physiology and Chronic Health Evaluation (APACHE) II scores at enrolment were 10.3-21.9, respectively. Incidence of mottling was 20.3% (22/108). CRT >3 seconds was observed in 50.9% (55/108). Development of mottling was significantly associated with 90-day mortality; 20/22 (90.9%) patients died in the mottling group versus 58/86 (65.1%) in the non-mottling group (p = 0.028). Capillary refill time >3 seconds did not corelate with mortality; 40/55 (72.7%) Patients with CRT >3 seconds died versus 32/53 (60.4%) patients died in CRT ≤3 seconds group. Occurrence of mottling could predict mortality; positive predictive value of 90.9% which was comparable to positive predictive value of lactate levels >4 mmol/L, i.e., 94.1%.

CONCLUSION

The incidence of mottling in septic shock is much less in patients of Indian ethnicity with brown skin color than in white-skinned population. Occurrence of mottling and not delayed CRT, is a better predictor of outcome in this setting.

HOW TO CITE THIS ARTICLE

Jog SA, Narasimhan VL, Rajhans PA, Akole PV, Pawar B, Bhurke B, et al. Mottling in Septic Shock: Ethnicity and Skin Color Matter. Indian J Crit Care Med 2023;27(12):902-909.

"The peripheral perfusion index discriminates haemodynamic responses to induction of general anaesthesia"

Induction of general anaesthesia is often accompanied by hypotension. Standard haemodynamic monitoring during anaesthesia relies on intermittent blood pressure and heart rate. Continuous monitoring systemic blood pressure requires invasive or advanced modalities creating a barrier for obtaining important information of the circulation. The Peripheral Perfusion Index (PPI) is obtained non-invasively and continuously by standard photoplethysmography. We hypothesized that different patterns of changes in systemic haemodynamics during induction of general anaesthesia would be reflected in the PPI. Continuous values of PPI, stroke volume (SV), cardiac output (CO), and mean arterial pressure (MAP) were evaluated in 107 patients by either minimally invasive or non-invasive means in a mixed population of surgical patients. 2 min after induction of general anaesthesia relative changes of SV, CO, and MAP was compared to the relative changes of PPI. After induction total cohort mean(± st.dev.) MAP, SV, and CO decreased to 65(± 16)%, 74(± 18)%, and 63(± 16)% of baseline values. In the 38 patients where PPI decreased MAP was 57(± 14)%, SV was 63(± 18)%, and CO was 55(± 18)% of baseline values 2 min after induction. In the 69 patients where PPI increased the corresponding values were MAP 70(± 15)%, SV 80(± 16)%, and CO 68(± 17)% (all differences: p < 0,001). During induction of general anaesthesia changes in PPI discriminated between the degrees of reduction in blood pressure and algorithm derived cardiac stroke volume and -output. As such, the PPI has potential to be a simple and non-invasive indicator of the degree of post-induction haemodynamic changes.

The effect of goal-directed hemodynamic therapy on clinical outcomes in patients undergoing radical cystectomy: a randomized controlled trial

BACKGROUND

This study investigated the effects of intraoperative goal-directed hemodynamic therapy (GDHT) on postoperative outcomes in patients undergoing open radical cystectomy.

METHODS

This prospective, single-center, randomized controlled trial included 82 patients scheduled for open radical cystectomy between September 2018 and November 2021. The GDHT group (n = 39) received the stroke volume index- and cardiac index-based hemodynamic management using advanced hemodynamic monitoring, while the control group (n = 36) received the standard care under the discretion of attending anesthesiologists during surgery. The primary outcome was the incidence of a composite of in-hospital postoperative complications during hospital stays.

RESULTS

A total of 75 patients were included in the final analysis. There was no significant difference in the incidence of in-hospital postoperative complications (28/39 [71.8%] vs. 30/36 [83.3%], risk difference [95% CI], -0.12 [-0.30 to 0.07], P = 0.359) between the groups. The amounts of intraoperative fluid administered were similar between the groups (2700 [2175-3250] vs. 2900 [1950-3700] ml, median difference [95% CI] -200 [-875 to 825], P = 0.714). The secondary outcomes, including the incidence of seven major postoperative complications, duration of hospital stay, duration of intensive care unit stay, and grade of complications, were comparable between the two groups. Trends in postoperative estimated glomerular filtration rate, serum creatinine, and C-reactive protein did not differ significantly between the two groups.

CONCLUSIONS

Intraoperative GDHT did not reduce the incidence of postoperative in-hospital complications during the hospital stay in patients who underwent open radical cystectomy.

TRIAL REGISTRATION

This study was registered at http://www.

CLINICALTRIALS

gov (Registration number: NCT03505112; date of registration: 23/04/2018).

Associations between clinical interventions and transcutaneous blood gas values in postoperative patients

PURPOSE

Postoperative monitoring of circulation and respiration is pivotal to guide intervention strategies and ensure patient outcomes. Transcutaneous blood gas monitoring (TCM) may allow for noninvasive assessment of changes in cardiopulmonary function after surgery, including a more direct assessment of local micro-perfusion and metabolism. To form the basis for studies assessing the clinical impact of TCM complication detection and goal-directed-therapy, we examined the association between clinical interventions in the postoperative period and changes in transcutaneous blood gasses.

METHODS

Two-hundred adult patients who have had major surgery were enrolled prospectively and monitored with transcutaneous blood gas measurements (oxygen (TcPO2) and carbon dioxide (TcPCO2)) for 2 h in the post anaesthesia care unit, with recording of all clinical interventions. The primary outcome was changes in TcPO2, secondarily TcPCO2, from 5 min before a clinical intervention versus 5 min after, analysed with paired t-test.

RESULTS

Data from 190 patients with 686 interventions were analysed. During clinical interventions, a mean change in TcPO2 of 0.99 mmHg (95% CI-1.79-0.2, p = 0.015) and TcPCO2 of-0.67 mmHg (95% CI 0.36-0.98, p < 0.001) was detected.

CONCLUSION

Clinical interventions resulted in significant changes in transcutaneous oxygen and carbon dioxide. These findings suggest future studies to assess the clinical value of changes in transcutaneous PO2 and PCO2 in a postoperative setting.

TRIAL REGISTRY

Clinical trial number: NCT04735380.

CLINICAL TRIAL REGISTRY

https://clinicaltrials.gov/ct2/show/NCT04735380.

Initial 24-h perfusion index of ICU admission is associated with acute kidney injury in perioperative critically ill patients: A retrospective cohort analysis

BACKGROUND

The relationship between perfusion index (PI) and organ dysfunction in patients in the intensive care unit (ICU) is not clear. This study aimed to explore the relationship between PI and renal function in the perioperative critical care setting and evaluate the predictive efficiency of PI on patients with acute kidney injury (AKI) in the ICU.

METHODS

This retrospective analysis involved 12,979 patients who had undergone an operation and were admitted to the ICU in Peking Union Medical College Hospital from January 2014 to December 2019. The distribution of average PI in the first 24 h after ICU admission and its correlation with AKI was calculated by Cox regression. Receiver operating characteristic (ROC) curves were generated to compare the ability of PI, mean arterial pressure (MAP), creatinine, blood urea nitrogen (BUN), and central venous pressure (CVP) to discriminate AKI in the first 48 h in all perioperative critically ill patients.

RESULTS

Average PI in the first 24 h served as an independent protective factor of AKI (Odds ratio [OR]=0.786, 95% confidence interval [CI]: 0.704-0.873, P <0.0001). With a decrease in PI by one unit, the incidence of AKI increased 1.74 times. Among the variables explored for the prediction of AKI (PI, MAP, creatine, BUN, and CVP), PI yielded the highest area under the ROC curve, with a sensitivity of 64.34% and specificity of 70.14%. A cut-off value of PI ≤2.12 could be used to predict AKI according to the Youden index. Moreover, patients in the low PI group (PI ≤2.12) exhibited a marked creatine elevation at 24-48 h with a slower decrease compared with those in the high PI group (PI >2.12).

CONCLUSIONS

As a local blood flow indicator, the initial 24-h average PI for perioperative critically ill patients can predict AKI during their first 120 h in the ICU.

Physiological stress level and screening for malnutrition as preoperative predictors of postoperative complications in pancreatic surgery: a retrospective study

BACKGROUND

Assessment of 'physiological stress levels' and 'nutritional status' before surgery is important for predicting complications and indirect interventions on the pancreas. The aim of this study was to determine neutrophil-lymphocyte ratio (NLR) and nutritional risk index (NRI) indicators before surgery to predict 90-day complications and mortality in a cohort of patients with complicated chronic pancreatitis and cancer of the head of the pancreas.

METHODS

We evaluated preoperative levels of NLR and NRI among 225 subjects treated at different centres located in three countries. Short-term outcomes included length of hospital stay, postoperative complications, and mortality at 90 days and were appreciated based on NLR and NRI. The level of physiological stress was divided according by the formulas: neutrophil-lymphocyte ratio (NLR) = (neutrophil count, %)/(lymphocyte count, %). The nutritional state of the patients was divided according to the INR: NRI = (1.519 × serum albumin, g/L) + (41.7 × present weight, kg / usual weight, kg)].

RESULTS

All patients were operated. An analysis of the operations performed in three institutions demonstrated mortality in chronic pancreatitis and pancreatic pseudocysts in 1.4%, in chronic pancreatitis and the presence of an inflammatory mass mainly in the pancreatic head in 1.2%, and in cancer of the pancreatic head in 5.9%. The mean preoperative NLR was normal in 33.8% of the patients, the mild physiologic stress level was 54.7%, and the moderate was 11.5% before surgery. 10.2% of patients had a normal nutritional status, 20% had mild, 19.6% had moderate, and 50.2% had severe malnutrition. In a univariate analysis, at the cutoff of NLR ≥ 9.5 (AUC = 0.803) and the cutoff of NRI ≤ 98.5 (AUC = 0.801), increasing the risk of complications was observed (hazard ratio, 2.01; 95% CI, 1.247-3.250, p = 0.006), but at the cutoff of NRI ≤ 83.55 (AUC = 0.81), we observed a survival difference in operated patients (hazard ratio, 2.15; 95% CI, 1.334-3.477, p = 0.0025).

CONCLUSIONS

Our study demonstrated that NLR and NRI were predictors of postoperative complications, but only NRI was a predictor of 90-day mortality in patients after surgery.

Cohort profile of PLUTO: a perioperative biobank focusing on prediction and early diagnosis of postoperative complications

PURPOSE

Although elective surgery is generally safe, some procedures remain associated with an increased risk of complications. Improved preoperative risk stratification and earlier recognition of these complications may ameliorate postoperative recovery and improve long-term outcomes. The perioperative longitudinal study of complications and long-term outcomes (PLUTO) cohort aims to establish a comprehensive biorepository that will facilitate research in this field. In this profile paper, we will discuss its design rationale and opportunities for future studies.

PARTICIPANTS

Patients undergoing elective intermediate to high-risk non-cardiac surgery are eligible for enrolment. For the first seven postoperative days, participants are subjected to daily bedside visits by dedicated observers, who adjudicate clinical events and perform non-invasive physiological measurements (including handheld spirometry and single-channel electroencephalography). Blood samples and microbiome specimens are collected at preselected time points. Primary study outcomes are the postoperative occurrence of nosocomial infections, major adverse cardiac events, pulmonary complications, acute kidney injury and delirium/acute encephalopathy. Secondary outcomes include mortality and quality of life, as well as the long-term occurrence of psychopathology, cognitive dysfunction and chronic pain.

FINDINGS TO DATE

Enrolment of the first participant occurred early 2020. During the inception phase of the project (first 2 years), 431 patients were eligible of whom 297 patients consented to participate (69%). Observed event rate was 42% overall, with the most frequent complication being infection.

FUTURE PLANS

The main purpose of the PLUTO biorepository is to provide a framework for research in the field of perioperative medicine and anaesthesiology, by storing high-quality clinical data and biomaterials for future studies. In addition, PLUTO aims to establish a logistical platform for conducting embedded clinical trials.

TRIAL REGISTRATION NUMBER

NCT05331118.

Evaluation of Postoperative Warming Care Protocol for Thermal Comfort and Temperature Management Immediately After Surgery: Nonrandomized Controlled Trial

PURPOSE

This study aimed to determine the effects of a warming care protocol (WCM) on temperature control and thermal comfort perception in hypothermia following major abdominal surgery.

DESIGN

A prospective nonrandomized controlled trial.

METHODS

A total of 54 patients undergoing major abdominal surgery were assigned to receive routine care (control group, 27 patients) or the WCM (intervention group, 27 patients). The body temperature (core and peripheral) was measured, and physical symptoms were monitored every hour for 4 hours after arriving at the ward and then every 4 hours for up to 12 hours.

FINDINGS

The temperature gap, calculated as the difference between the core and skin temperatures, was similar between the control and intervention groups at the end of surgery. However, the temperature gap in the intervention group decreased within 3 hours after arrival at the ward and remained lower than that in the control group. The visual analog scale score for postoperative thermal discomfort was significantly lower in the intervention group than in the control group, indicating achievement of higher comfort with the warming intervention.

CONCLUSIONS

Patients were warmed using active warming methods under the WCM, which in turn increased the thermal comfort perception with the body temperature. Postoperative patients often require warming care for thermal comfort, which may be improved by proper observation and management within 1 to 2 hours postoperatively. Our results indicate that nurses could effectively warm the patient to maintain normal body temperature following surgery not only to improve thermal comfort, but also to prevent shivering and possibly various postoperative complications.

Hemodynamics and cutaneous microcirculation during induction of general anesthesia with and without esketamine

OBJECTIVE

Currently, there are limited data on the effect of macrocirculatory hemodynamic changes on human microcirculation, especially during the induction of general anesthesia (GA).

METHODS

We performed a non-randomized observational trial on patients receiving GA for elective surgery. In the control group (CG), for GA induction sufentanil, propofol, and rocuronium was administered. Patients assigned to the esketamine group (EG) received additional esketamine for GA induction. Invasive blood pressure (IBP) and pulse contour cardiac output (CO) measurement were performed continuously. Microcirculation was assessed using cutaneous Laser Doppler Flowmetry (forehead and sternum LDF), peripheral and central Capillary Refill Time (pCRT, cCRT), as well as brachial temperature gradient (Tskin-diff) at baseline, 5, 10 and 15 minutes after induction of GA.

RESULTS

42 patients were included in the analysis (CG n = 22, EG n = 20). pCRT, cCRT, Tskin-diff, forehead and sternum LDF decreased following GA induction in both groups. IBP and CO were significantly more stable in esketamine group. However, the changes in the microcirculatory parameters were not significantly different between the groups.

CONCLUSIONS

The addition of esketamine for GA induction warranted better hemodynamic stability for the first five minutes, but had no significant effect on any of the cutaneous microcirculatory parameters measured.

[Possibilities of tissue perfusion assessment in abdominal surgery: integration into the intraoperative system of safety control points]

OBJECTIVE

To evaluate the possibility of integrating tissue perfusion assessment techniques (ICG perfusion and imaging photoplethysmography - iPPG) into the system of intraoperative control points of laparoscopic interventions with a reconstructive component.

MATERIALS AND METHODS

Quantitative assessment of ICG fluorescence and iPPG were used during 8 laparoscopically assisted interventions: gastrectomy for gastric cancer (total - 2 and distal - 1) and colorectal resections (left-sided colorectal resections - 4 and right hemicolectomy - 1).

RESULTS

Four stages are presented for the assessment of tissue perfusion: initial assessment, before intestine transection, before anastomosis formation, and evaluation of anastomosis. From the point of view of the significance of clinical decision-making, the «before intestine transection» stage is of great importance, due to the ease of transferring the resection level to the optimal tissue perfusion zone.

CONCLUSION

Integration of tissue perfusion assessment techniques into the system of intraoperative checkpoints is possible and promising.

Comparison of Bedside and Video-Based Capillary Refill Time Assessment in Children

OBJECTIVES

Capillary refill time (CRT) to assess peripheral perfusion in children with suspected shock may be subject to poor reproducibility. Our objectives were to compare video-based and bedside CRT assessment using a standardized protocol and evaluate interrater and intrarater consistency of video-based CRT (VB-CRT) assessment. We hypothesized that measurement errors associated with raters would be low for both standardized bedside CRT and VB-CRT as well as VB-CRT across raters.

METHODS

Ninety-nine children (aged 1-12 y) had 5 consecutive bedside CRT assessments by an experienced critical care clinician following a standardized protocol. Each CRT assessment was video recorded on a black background. Thirty video clips (10 with bedside CRT < 1 s, 10 with CRT 1-2 s, and 10 with CRT > 2 s) were randomly selected and presented to 10 clinicians twice in randomized order. They were instructed to push a button when they visualized release of compression and completion of a capillary refill. The correlation and absolute difference between bedside and VB-CRT were assessed. Consistency across raters and within each rater was analyzed using the intraclass correlation coefficient (ICC). A Generalizability study was performed to evaluate sources of variation.

RESULTS

We found moderate agreement between bedside and VB-CRT observations (r = 0.65; P < 0.001). The VB-CRT values were shorter by 0.17 s (95% confidence interval, 0.09-0.25; P < 0.001) on average compared with bedside CRT. There was moderate agreement in VB-CRT across raters (ICC = 0.61). Consistency of repeated VB-CRT within each rater was moderate (ICC = 0.71). Generalizability study revealed the source of largest variance was from individual patient video clips (57%), followed by interaction of the VB-CRT reviewer and patient video clip (10.7%).

CONCLUSIONS

Bedside and VB-CRT observations showed moderate consistency. Using video-based assessment, moderate consistency was also observed across raters and within each rater. Further investigation to standardize and automate CRT measurement is warranted.

Kinetics of capillary refill time after fluid challenge

Background

Capillary refill time (CRT) is a valuable tool for triage and to guide resuscitation. However, little is known about CRT kinetics after fluid infusion.

Methods

We conducted a prospective observational study in a tertiary teaching hospital. First, we analyzed the intra-observer variability of CRT. Next, we monitored fingertip CRT in sepsis patients during volume expansion within the first 24 h of ICU admission. Fingertip CRT was measured every 2 min during 30 min following crystalloid infusion (500 mL over 15 min).

Results

First, the accuracy of repetitive fingertip CRT measurements was evaluated on 40 critically ill patients. Reproducibility was excellent, with an intra-class correlation coefficient of 99.5% (CI 95% [99.3, 99.8]). A CRT variation larger than 0.2 s was considered as significant. Next, variations of CRT during volume expansion were evaluated on 29 septic patients; median SOFA score was 7 [5–9], median SAPS II was 57 [45–72], and ICU mortality rate was 24%. Twenty-three patients were responders as defined by a CRT decrease  > 0.2 s at 30 min after volume expansion, and 6 were non-responders. Among responders, we observed that fingertip CRT quickly improved with a significant decrease at 6–8 min after start of crystalloid infusion, the maximal improvement being observed after 10–12 min (−0.7 [−0.3;−0.9] s) and maintained at 30 min. CRT variations significantly correlated with baseline CRT measurements (R = 0.39, P = 0.05).

Conclusions

CRT quickly improved during volume expansion with a significant decrease 6–8 min after start of fluid infusion and a maximal drop at 10–12 min.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01049-x.

Peripheral tissue hypoperfusion predicts post intubation hemodynamic instability

Background

Tracheal intubation and invasive mechanical ventilation initiation is a procedure at high risk for arterial hypotension in intensive care unit. However, little is known about the relationship between pre-existing peripheral microvascular alteration and post-intubation hemodynamic instability (PIHI).

Methods

Prospective observational monocenter study conducted in an 18-bed medical ICU. Consecutive patients requiring tracheal intubation were eligible for the study. Global hemodynamic parameters (blood pressure, heart rate, cardiac function) and tissue perfusion parameters (arterial lactate, mottling score, capillary refill time [CRT], toe-to-room gradient temperature) were recorded before, 5 min and 2 h after tracheal intubation (TI). Post intubation hemodynamic instability (PIHI) was defined as any hemodynamic event requiring therapeutic intervention.

Results

During 1 year, 120 patients were included, mainly male (59%) with a median age of 68 [57–77]. The median SOFA score and SAPS II were 6 [4–9] and 47 [37–63], respectively. The main indications for tracheal intubation were hypoxemia (51%), hypercapnia (13%), and coma (29%). In addition, 48% of patients had sepsis and 16% septic shock. Fifty-one (42%) patients develop PIHI. Univariate analysis identified several baseline factors associated with PIHI, including norepinephrine prior to TI, sepsis, tachycardia, fever, higher SOFA and high SAPSII score, mottling score ≥ 3, high lactate level and prolonged knee CRT. By contrast, mean arterial pressure, baseline cardiac index, and ejection fraction were not different between PIHI and No-PIHI groups. After adjustment on potential confounders, the mottling score was associated with a higher risk for PIHI (adjusted OR: 1.84 [1.21–2.82] per 1 point increased; p = 0.005). Among both global haemodynamics and tissue perfusion parameters, baseline mottling score was the best predictor of PIHI (AUC: 0.72 (CI 95% [0.62–0.81]).

Conclusions

In non-selected critically ill patients requiring invasive mechanical ventilation, tissue hypoperfusion parameters, especially the mottling score, could be helpful to predict PIHI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01043-3.

Capillary refill time for the management of acute circulatory failure: a survey among pediatric and adult intensivists

INTRODUCTION

Recent studies have shown the prognostic value of capillary refill time (CRT) and suggested that resuscitation management guided by CRT may reduce morbidity and mortality in patients with septic shock. However, little is known about the current use of CRT in routine clinical practice. This study aimed to assess the modalities of CRT use among French adult and pediatric intensivists.

METHODS

A cross-sectional survey exploring CRT practices in acute circulatory failure was performed. The targeted population was French adult and pediatric intensivists (SFAR and GFRUP networks). An individual invitation letter including a survey of 32 questions was emailed twice. Descriptive and analytical statistics were performed.

RESULTS

Among the 6071 physicians who received the letter, 418 (7%) completed the survey. Among all respondents, 82% reported using CRT in routine clinical practice, mainly to diagnose acute circulatory failure, but 45% did not think CRT had any prognostic value. Perfusion goal-directed therapy based on CRT was viewed as likely to improve patient outcome by 37% of respondents. The measurement of CRT was not standardized as the use of a chronometer was rare (3%) and the average of multiple measurements rarely performed (46%). Compared to adult intensivists, pediatric intensivists used CRT more frequently (99% versus 76%) and were more confident in its diagnostic value and its ability to guide treatment.

CONCLUSION

CRT measurement is widely used by intensivists in patients with acute circulatory failure but most often in a non-standardized way. This may lead to a misunderstanding of CRT reliability and clinical usefulness.

Intraoperative visualization and quantitative assessment of tissue perfusion by imaging photoplethysmography: comparison with ICG fluorescence angiography

Intraoperative monitoring of tissue perfusion is of great importance for optimizing surgery and reducing postoperative complications. To date, there is no standard procedure for assessing blood circulation in routine clinical practice. Over the past decade, indocyanine green (ICG) fluorescence angiography is most commonly used for intraoperative perfusion evaluation. Imaging photoplethysmography (iPPG) potentially enables contactless assessment of the blood supply to organs. However, no strong evidence of this potential has been provided so far. Here we report results of a comparative assessment of tissue perfusion obtained using custom-made iPPG and commercial ICG-fluorescence systems during eight different gastrointestinal surgeries. Both systems allow mapping the blood-supply distribution over organs. It was demonstrated for the first time that the quantitative assessment of blood perfusion by iPPG is in good agreement with that obtained by ICG-fluorescence imaging in all surgical cases under study. iPPG can become an objective quantitative monitoring system for tissue perfusion in the operating room due to its simplicity, low cost and no need for any agent injections.

Imaging PPG for In Vivo Human Tissue Perfusion Assessment during Surgery

Surgical excision is the golden standard for treatment of intestinal tumors. In this surgical procedure, inadequate perfusion of the anastomosis can lead to postoperative complications, such as anastomotic leakages. Imaging photoplethysmography (iPPG) can potentially provide objective and real-time feedback of the perfusion status of tissues. This feasibility study aims to evaluate an iPPG acquisition system during intestinal surgeries to detect the perfusion levels of the microvasculature tissue bed in different perfusion conditions. This feasibility study assesses three patients that underwent resection of a portion of the small intestine. Data was acquired from fully perfused, non-perfused and anastomosis parts of the intestine during different phases of the surgical procedure. Strategies for limiting motion and noise during acquisition were implemented. iPPG perfusion maps were successfully extracted from the intestine microvasculature, demonstrating that iPPG can be successfully used for detecting perturbations and perfusion changes in intestinal tissues during surgery. This study provides proof of concept for iPPG to detect changes in organ perfusion levels.

Hyperspectral imaging for perioperative monitoring of microcirculatory tissue oxygenation and tissue water content in pancreatic surgery - an observational clinical pilot study

BACKGROUND

Hyperspectral imaging (HSI) could provide extended haemodynamic monitoring of perioperative tissue oxygenation and tissue water content to visualize effects of haemodynamic therapy and surgical trauma. The objective of this study was to assess the capacity of HSI to monitor skin microcirculation and possible relations to perioperative organ dysfunction in patients undergoing pancreatic surgery.

METHODS

The hyperspectral imaging TIVITA® Tissue System was used to evaluate superficial tissue oxygenation (StO2), deeper layer tissue oxygenation (near-infrared perfusion index (NPI)), haemoglobin distribution (tissue haemoglobin index (THI)) and tissue water content (tissue water index (TWI)) in 25 patients undergoing pancreatic surgery. HSI parameters were measured before induction of anaesthesia (t1), after induction of anaesthesia (t2), postoperatively before anaesthesia emergence (t3), 6 h after emergence of anaesthesia (t4) and three times daily (08:00, 14:00, 20:00 ± 1 h) at the palm and the fingertips until the second postoperative day (t5-t10). Primary outcome was the correlation of HSI with perioperative organ dysfunction assessed with the perioperative change of SOFA score.

RESULTS

Two hundred and fifty HSI measurements were performed in 25 patients. Anaesthetic induction led to a significant increase of tissue oxygenation parameters StO2 and NPI (t1-t2). StO2 and NPI decreased significantly from t2 until the end of surgery (t3). THI of the palm showed a strong correlation with haemoglobin levels preoperatively (t2: r = 0.83, p < 0.001) and 6 h postoperatively (t4: r = 0.71, p = 0.001) but not before anaesthesia emergence (t3: r = 0.35, p = 0.10). TWI of the palm and the fingertip rose significantly between pre- and postoperative measurements (t2-t3). Higher blood loss, syndecan level and duration of surgery were associated with a higher increase of TWI. The perioperative change of HSI parameters (∆t1-t3) did not correlate with the perioperative change of the SOFA score.

CONCLUSION

This is the first study using HSI skin measurements to visualize tissue oxygenation and tissue water content in patients undergoing pancreatic surgery. HSI was able to measure short-term changes of tissue oxygenation during anaesthetic induction and pre- to postoperatively. TWI indicated a perioperative increase of tissue water content. Perioperative use of HSI could be a useful extension of haemodynamic monitoring to assess the microcirculatory response during haemodynamic therapy and major surgery.

TRIAL REGISTRATION

German Clinical Trial Register, DRKS00017313 on 5 June 2019.

Assessment of Tissue Perfusion Using the Peripheral Perfusion Index and Lactate Clearance in Shock in Pediatric Patients

BACKGROUND

Pediatric shock has a high mortality rate because many of the early clinical signs are subtle and have poor sensitivity and specificity. Pediatric shock was categorized either: compensated with normal blood pressure, poor skin perfusion (CRT >2 s, mottled, cool peripheries, peripheral cyanosis), weak peripheral pulse, age specific tachycardia, tachypnoea, and oliguria or decompensated with hypotension (SBP < 70 + (2× age in years) mm Hg and decreased mental status. The perfusion index is a non-invasive method for assessing peripheral perfusion and may be a useful marker for identifying shock early in pediatric patients.

OBJECTIVE

This prospective cohort study (November 2019 to August 2020) evaluated whether the perfusion index, lactate, and/or lactate clearance could predict mortality among pediatric shock patients.

METHODS

Fifty children (68% male) with shock underwent assessments at presentation to the emergency room to evaluate their heart rate, blood pressure, capillary refill time, central venous pressure, perfusion index, cardiac index, systemic vascular resistance, central venous oxygen saturation, and lactate clearance.

RESULTS

The perfusion index range was 0.03 to 2.2 and ≤0.18 as the cut-off for mortality prediction providing 74% sensitivity and 78% specificity. The serum lactate concentration range was 0 to 16 mmol/L and >5.7 mmol/L as the cut-off for mortality prediction provided 70% sensitivity and 96% specificity at presentation to the emergency room. The lactate clearance range was 3% to 75% and >10% as the cut-off for survival prediction after resuscitation and at 6 h later.

CONCLUSION

Perfusion index (PI), lactate, and lactate clearance provided comparable sensitivity and specificity for predicting outcomes among pediatric patients with shock Therefore, we suggest that the PI is an inexpensive, rapid, and non-invasive tool that can be used to predict illness severity and mortality in busy pediatric intensive care units and emergency departments. This tool may guide better patient triage and an earlier diagnosis of shock in this setting.

Plethysmographic Peripheral Perfusion Index: Could It Be a New Vital Sign?

The plethysmographic peripheral perfusion index (PPI) is a very useful parameter with various emerging utilities in medical practice. The PPI represents the ratio between pulsatile and non-pulsatile portions in peripheral circulation and is mainly affected by two main determinants: cardiac output and balance between sympathetic and parasympathetic nervous systems. The PPI decreases in cases of sympathetic predominance and/or low cardiac output states; therefore, it is a useful predictor of patient outcomes in critical care units. The PPI could be a surrogate for cardiac output in tests for fluid responsiveness, as an objective measure of pain especially in un-cooperative patients, and as a predictor of successful weaning from mechanical ventilation. The PPI is simple to measure, easy to interpret, and has continuously displayed variables, making it a convenient parameter for detecting the adequacy of blood flow and sympathetic-parasympathetic balance.

Measurement of capillary refill time with a handheld prototype device: a comparative validation study in healthy volunteers

Validity and reproducibility of clinical capillary refill time (CRT) measurement depend on many factors in daily routine practice. We conducted a prospective validation study of an automatized handheld prototype device providing standardized CRT assessment (DiCART™) in 20 healthy volunteers. Three different methods of CRT measurement were compared before and during dynamic circulatory changes induced by venous and arterial occlusion tests at both upper and lower limb levels: CRT_CLIN corresponding to basic clinical assessment and considered as the reference method; CRT_VIDEO corresponding to off-line videos reviewed by investigators recorded by DiCART™; and CRT_DiCART corresponding to on-line videos analysed by a built-in proprietary mathematical algorithm included in DiCART™. Five subjects were excluded because of a DiCART™ dysfunction. ROC_AUC to detect arterial occlusion test changes at the upper limb level were 1.00 (95%CI 1.00; 1.00), 0.96 (95%CI 0.88; 1.00), and 0.92 (95%CI 0.79; 1.00) for CRT_CLIN, CRT_VIDEO, and CRT_DiCART, respectively. Precision of CRT_CLIN and CRT_VIDEO were significantly better than CRT_DiCART (0.18 and 0.20 vs. 0.28; P < 0.05). Percentages of error were 76% and 87% for CRT_VIDEO and CRT_DiCART, respectively. DiCART™ had an excellent discrimination to detect major changes in CRT induced by arterial ischemia. However, the perfectible precision, the poor agreement with clinical assessment and numerous device dysfunctions give leads to the development of a further version of the prototype before promoting its use in clinical practice.Trial registration clinicaltrial.gov. Identifier: NCT04538612.

Association of the intraoperative peripheral perfusion index with postoperative morbidity and mortality in acute surgical patients: a retrospective observational multicentre cohort study

Background

We hypothesised that in acute high-risk surgical patients, a lower intraoperative peripheral perfusion index (PPI) would indicate a higher risk of postoperative complications and mortality.

Methods

This retrospective observational study included 1338 acute high-risk surgical patients from November 2017 until October 2018 at two University Hospitals in Denmark. Intraoperative PPI was the primary exposure variable and the primary outcome was severe postoperative complications defined as a Clavien–Dindo Class ≥III or death, within 30 days.

Results

intraoperative PPI was associated with severe postoperative complications or death: odds ratio (OR) 1.12 (95% confidence interval [CI] 1.05–1.19; P<0.001), with an association of intraoperative mean PPI ≤0.5 and PPI ≤1.5 with the primary outcome: OR 1.79 (95% CI 1.09–2.91; P=0.02) and OR 1.65 (95% CI 1.20–2.27; P=0.002), respectively. Each 15-min increase in intraoperative time spend with low PPI was associated with the primary outcome (per 15 min with PPI ≤0.5: OR 1.11 (95% CI 1.05–1.17; P<0.001) and with PPI ≤1.5: OR 1.06 (95% CI 1.02–1.09; P=0.002)). Thirty-day mortality in patients with PPI ≤0.5 was 19% vs 10% for PPI >0.5, P=0.003. If PPI was ≤1.5, 30-day mortality was 16% vs 8% in patients with a PPI >1.5 (P<0.001). In contrast, intraoperative mean MAP ≤65 mm Hg was not significantly associated with severe postoperative complications or death (OR 1.21 [95% CI 0.92–1.58; P=0.2]).

Conclusions

Low intraoperative PPI was associated with severe postoperative complications or death in acute high-risk surgical patients. To guide intraoperative haemodynamic management, the PPI should be further investigated.

Standardized capillary refill time and relation to clinical parameters in hospitalized dogs

OBJECTIVE

To assess the relationship between various physical and clinicopathologic parameters and the capillary refill time (CRT) using a standard method; to evaluate the influence of emergency room (ER) versus ICU hospital location on CRT; and to identify latent subgroups among the CRT distribution.

DESIGN

Prospective, observational study.

SETTING

University teaching hospital.

ANIMALS

Client-owned dogs in the ER (n = 40) and ICU (n = 71).

INTERVENTIONS

The CRT was defined as the duration required for the oral mucosa of the upper lip to return to its original color after blanching for 4 seconds. The CRT was recorded in seconds to the 10ths place by a single observer using an automated recording device.

MEASUREMENTS AND MAIN RESULTS

Median CRT for all dogs was 1.1 seconds (ER, 1.2 s; ICU, 1.1 s; P = 1.000). The CRT was significantly associated with rectal temperature (P = 0.004), systolic blood pressure (P = 0.028), body weight (P = 0.031), mucous membrane color (P = 0.007), skin turgor (P = 0.039), and acute patient physiologic and laboratory evaluation mentation score (P = 0.019) for all dogs. The CRT was related to a greater number of variables in the ER than in the ICU patient population. In general, the total population of dogs had CRTs belonging to 1 of 2 groups: either ≤1.2 or ≥1.7 seconds. A statistically significant association was found between body weight CRT ≥1.3 seconds (P = 0.02).

CONCLUSIONS

A CRT following blanching for 4 seconds may provide insight into the hydration status and hemodynamic stability of canine patients. Further research into its clinical application is warranted.

Clinical use of peripheral perfusion parameters in septic shock

PURPOSE OF REVIEW

Current goals of resuscitation in septic shock are mainly a fixed volume of fluids and vasopressors to correct hypotension and improve tissue perfusion indicated by decreasing lactate levels.

RECENT FINDINGS

Abnormal peripheral perfusion by objective and subjective parameters are associated with increased mortality in various phases of the treatment of critically ill patients including patients with septic shock. Ongoing resuscitation in septic shock patients with normal peripheral perfusion is not associated with improved outcome, rather with increased mortality. Mitigation of fluid resuscitation by using parameters of peripheral perfusion in septic shock seems to be safe.

SUMMARY

Septic shock patients with normal peripheral perfusion represent a different clinical phenotype of patients that might benefit from limited resuscitation efforts. Parameters of peripheral perfusion could be used to guide the individualization of patients with septic shock.

Risk Factors and Outcomes for Postoperative Ileus After Small Intestinal Fistula Excision in Patients With Diffuse Extensive Abdominal Adhesions

Purpose: The study aimed to investigate the risk factors for postoperative ileus (POI) after small intestinal fistula excision (SIFE) in patients with diffuse extensive abdominal adhesions. Methods: From October 2010 to December 2019, we enrolled patients who underwent SIFE and had diffuse extensive abdominal adhesions. Patients were divided into the POI group and the non-POI group according to its occurrence. We then investigated and analyzed the clinical characteristics of both groups. Result: A total of 247 patients were enrolled into the study. There were 100 patients in the POI group, and 147 patients in the non-POI group. A multi-variable logistic regression analysis revealed that blood loss during SIFE (OR = 1.001; 95% CI: 1.000-1.259; P = 0.012), postoperative lactate(OR = 1.212; 95% CI: 1.001-1.304; P = 0.015), grade V abdominal adhesions (OR = 2.518; 95% CI: 1.814-3.44; P = 0.024), and time for recovery of lactate <2 mmol/L (OR = 2.079; 95% CI: 1.599-3.616; P = 0.026) were associated with POI. Moreover, POI was also associated with prolonged postoperative stay in the hospital (HR = 3.291; 95% CI: 2.511-4.172; P = 0.014). Conclusion: Blood loss during operation, grade V abdominal adhesions, positive fluid balance within 48 h of operation, and time for recovery of lactate were the risk factors for POI after SIFE in patients with diffuse extensive abdominal adhesions.

Advances in the Approaches Using Peripheral Perfusion for Monitoring Hemodynamic Status

Measures of peripheral perfusion can be used to assess the hemodynamic status of critically ill patients. By monitoring peripheral perfusion status, clinicians can promptly initiate life-saving therapy and reduce the likelihood of shock-associated death. Historically, abnormal perfusion has been indicated by the observation of pale, cold, and clammy skin with increased capillary refill time. The utility of these assessments has been debated given that clinicians may vary in their clinical interpretation of body temperature and refill time. Considering these constraints, current sepsis bundles suggest the need to revise resuscitation guidelines. New technologies have been developed to calculate capillary refill time in the hopes of identifying a new gold standard for clinical care. These devices measure either light reflected at the surface of the fingertip (reflected light), or light transmitted through the inside of the fingertip (transmitted light). These new technologies may enable clinicians to monitor peripheral perfusion status more accurately and may increase the potential for ubiquitous hemodynamic monitoring across different clinical settings. This review will summarize the different methods available for peripheral perfusion monitoring and will discuss the advantages and disadvantages of each approach.

Supervised Machine Learning Applied to Automate Flash and Prolonged Capillary Refill Detection by Pulse Oximetry

Objective

Develop an automated approach to detect flash (<1.0 s) or prolonged (>2.0 s) capillary refill time (CRT) that correlates with clinician judgment by applying several supervised machine learning (ML) techniques to pulse oximeter plethysmography data.

Materials and Methods

Data was collected in the Pediatric Intensive Care Unit (ICU), Cardiac ICU, Progressive Care Unit, and Operating Suites in a large academic children’s hospital. Ninety-nine children and 30 adults were enrolled in testing and validation cohorts, respectively. Patients had 5 paired CRT measurements by a modified pulse oximeter device and a clinician, generating 485 waveform pairs for model training. Supervised ML models using gradient boosting (XGBoost), logistic regression (LR), and support vector machines (SVMs) were developed to detect flash (<1 s) or prolonged CRT (≥2 s) using clinician CRT assessment as the reference standard. Models were compared using Area Under the Receiver Operating Curve (AUC) and precision-recall curve (positive predictive value vs. sensitivity) analysis. The best performing model was externally validated with 90 measurement pairs from adult patients. Feature importance analysis was performed to identify key waveform characteristics.

Results

For flash CRT, XGBoost had a greater mean AUC (0.79, 95% CI 0.75–0.83) than logistic regression (0.77, 0.71–0.82) and SVM (0.72, 0.67–0.76) models. For prolonged CRT, XGBoost had a greater mean AUC (0.77, 0.72–0.82) than logistic regression (0.73, 0.68–0.78) and SVM (0.75, 0.70–0.79) models. Pairwise testing showed statistically significant improved performance comparing XGBoost and SVM; all other pairwise model comparisons did not reach statistical significance. XGBoost showed good external validation with AUC of 0.88. Feature importance analysis of XGBoost identified distinct key waveform characteristics for flash and prolonged CRT, respectively.

Conclusion

Novel application of supervised ML to pulse oximeter waveforms yielded multiple effective models to identify flash and prolonged CRT, using clinician judgment as the reference standard.

Tweet

Supervised machine learning applied to pulse oximeter waveform features predicts flash or prolonged capillary refill.

Association of remote imaging photoplethysmography and cutaneous perfusion in volunteers

Remote imaging photoplethysmography (iPPG) senses the cardiac pulse in outer skin layers and is responsive to mean arterial pressure and pulse pressure in critically ill patients. Whether iPPG is sufficiently sensitive to monitor cutaneous perfusion is not known. This study aimed at determining the response of iPPG to changes in cutaneous perfusion measured by  Laser speckle imaging (LSI). Thirty-seven volunteers were engaged in a cognitive test known to evoke autonomic nervous activity and a Heat test. Simultaneous measurements of iPPG and LSI were taken at baseline and during cutaneous perfusion challenges. A perfusion index (PI) was calculated to assess iPPG signal strength. The response of iPPG to the challenges and its relation to LSI were determined. PI of iPPG significantly increased in response to autonomic nervous stimuli and to the Heat test by 5.8% (p = 0.005) and 11.1% (p < 0.001), respectively. PI was associated with LSI measures of cutaneous perfusion throughout experiments (p < 0.001). iPPG responses to study task correlated with those of LSI (r = 0.62, p < 0.001) and were comparable among subjects. iPPG is sensitive to autonomic nervous activity in volunteers and is closely associated with cutaneous perfusion.

The critical care literature 2019

An emergency physician (EP) is often the first health care provider to evaluate, resuscitate, and manage a critically ill patient. In recent years, the annual hours of critical care delivered in emergency departments across the United States has steadily increased. From 2006 to 2014, emergency department (ED) visits for critically ill patients increased approximately 80%. In addition to seeing more critically ill patients, EPs are often tasked with providing critical care long beyond the initial resuscitation period. In fact, more than 50% of ED patients that require admission to the ICU remain in the ED for more than 6 h. Prolonged ED wait times for critically ill patients to be transferred to the ICU is associated with increased hospital, 30-day, and 90-day mortality. It is during these early hours of critical illness, while the patient is in the ED, where lives can be saved or lost. Therefore, it is important for the EP to be knowledgeable about recent developments in resuscitation and critical care medicine. This review summarizes important articles published in 2019 pertaining to the resuscitation and care of select critically ill patients. We chose these articles based on our opinion of the importance of the study findings and their application to emergency medicine. The following topics are covered: sepsis, rapid sequence intubation, mechanical ventilation, neurocritical care, post-cardiac arrest care, and ED-based ICUs.

Remote Photoplethysmographic Assessment of the Peripheral Circulation in Critical Care Patients Recovering From Cardiac Surgery

PURPOSE

Camera-based photoplethysmography (cbPPG) remotely detects the volume pulse of cardiac ejection in the peripheral circulation. The cbPPG signal is sourced from the cutaneous microcirculation, yields a 2-dimensional intensity map, and is therefore an interesting monitoring technique. In this study, we investigated whether cbPPG is in general sufficiently sensitive to discern hemodynamic conditions.

METHODS

cbPPG recordings of 70 patients recovering from cardiac surgery were analyzed. Photoplethysmograms were processed offline and the optical pulse power (OPP) of cardiac ejection was calculated. Hemodynamic data, image intensity, and patient movements were recorded synchronously. The effects of hemodynamic parameters and measurement conditions on the patient's individual OPP variability and their actual OPP values were calculated in mixed-effects regression models.

RESULTS

Mean arterial pressure (MAP), pulse pressure (PP), heart rate (HR), and central venous pressure (CVP) significantly explained the individual OPP variability. PP had the highest explanatory power (19.9%). Averaged OPP significantly increased with PP and MAP (P < 0.001, respectively) and decreased with higher HR (P = 0.024). CVP had a 2-directional, nonsignificant effect on averaged OPP. Image intensity and patient movements did significantly affect OPP. After adjustment for hemodynamic covariables and measurement conditions, the effect of PP and HR remained unchanged, whereas that of MAP vanished.

CONCLUSION

cbPPG is sensitive to hemodynamic parameters in critical care patients. It is a potential application for monitoring the peripheral circulation. Its value in a clinical setting has to be determined.

Peripheral perfusion index predicting prolonged ICU stay earlier and better than lactate in surgical patients: an observational study

Background

Peripheral perfusion index (PPI) is an indicator reflecting perfusion. Patients undergoing long time surgeries are more prone to hypoperfusion and increased lactate. Few studies focusing on investigating the association between PPI and surgical patients’ prognoses. We performed this study to find it out.

Methods

From January 2019 to September 2019, we retrospected all surgical patients who were transferred to ICU, Xinyang Central hospital, Henan province, China. Inclusive criteria: age ≥ 18 years old; surgical length ≥ 120 min. Exclusive criteria: died in ICU; discharging against medical advice; existing diseases affecting blood flow of upper limbs, for example, vascular thrombus in arms; severe liver dysfunction.

We defined “prolonged ICU stay” as patients with their length of ICU stay longer than 48 h. According to the definition, patients were divided into two groups: “prolonged group” (PG) and “non-prolong group” (nPG). Baseline characteristics, surgical and therapeutic information, ICU LOS, SOFA and APACHE II were collected. Besides we gathered data of following parameters at 3 time points (T0: ICU admission; T1: 6 h after admission; T2: 12 h after admission): mean artery pressure (MAP), lactate, heart rate (HR), PPI and body temperature. Data were compared between the 2 groups. Multivariable binary logistic regression and ROC (receiver operating characteristic) curves were performed to find the association between perfusion indictors and ICU LOS.

Results

Eventually, 168 patients were included, 65 in PG and 103 in nPG. Compared to nPG, patients in PG had higher blood lactate and lower PPI. PPI showed significant difference between two groups earlier than lactate (T₀ vs T₁). The value of PPI at two time points was lower in PG than nPG(T0: 1.09 ± 0.33 vs 1.41 ± 0.45, p = 0.001; T1: 1.08 ± 0.37 vs 1.49 ± 0.41, p < 0.001).

Increased lactate_T1(OR 3.216; 95% CI 1.253–8.254, P = 0.015) and decreased PPI_T1 (OR 0.070; 95% CI 0.016–0.307, P < 0.001) were independently associated with prolonged ICU stay. The area under ROC of the PPI_T1 for predicting ICU stay> 48 h was 0.772, and the cutoff value for PPI_T1 was 1.35, with 83.3% sensitivity and 73.8% specificity.

Conclusions

PPI and blood lactate at T₁(6 h after ICU admission) are associated with ICU LOS in surgical patient. Compared to lactate, PPI indicates hypoperfusion earlier and more accurate in predicting prolonged ICU stay.

Study protocol for an exploratory interventional study investigating the feasibility of video-based non-contact physiological monitoring in healthy volunteers by Mapping Of Lower Limb skIn pErfusion (MOLLIE)

INTRODUCTION

Skin perfusion varies in response to changes in the circulatory status. Blood flow to skin is reduced during haemodynamic collapse secondary to peripheral vasoconstriction, whereas increased skin perfusion is frequently observed when haemodynamics improve with resuscitation. These changes in perfusion may be monitored using non-contact image-based methods. Previous camera-derived physiological measurements have focused on accurate vital signs monitoring and extraction of physiological signals from environmental noise. One of the biggest challenges of camera-derived monitoring is artefacts from motion, which limits our understanding of what parameters may be derived from skin. In this study, we use phenylephrine and glyceryl trinitrate (GTN) to cause vasoconstriction and vasodilation in stationary healthy volunteers to describe directional changes in skin perfusion pattern.

METHODS AND ANALYSIS

We aim to recruit 30 healthy volunteers who will undergo protocolised infusions of phenylephrine and GTN, followed by the monitored and timed release of a thigh tourniquet. The experimental timeline will be identical for all participants. Measurements of traditionally used haemodynamic markers (heart rate, blood pressure and stroke volume) and camera-derived measurements will be taken concurrently throughout the experimental period. The parameters of interest from the image data are skin colour and pattern, skin surface temperature, pulsatile signal detected at the skin surface and skin perfusion index.

ETHICS AND DISSEMINATION

This study was reviewed and approved by the Oxford University Research and Ethics Committee and Clinical Trials and Research Governance teams (R63796/RE001). The results of this study will be presented at scientific conferences and published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ISRCTN10417167.

Capillary refill time as part of an early warning score for rapid response team activation is an independent predictor of outcomes

BACKGROUND

Capillary refill time (CRT) is easy, quick to perform and when prolonged in critical illness, correlates with progression of organ failure and mortality. It is utilized in our hospital's early warning score (EWS) as one of 11 parameters. We sought to define CRT's value in predicting patient outcomes, compared to the remaining EWS elements.

METHODS

Five-year prospective observational study of 6480 consecutive Rapid Response Team (RRT) patients. CRT measured at the index finger was considered prolonged if time to previous-color return was >3 s. We analyzed the odds ratio of normal vs prolonged-CRT, compared to the other EWS variables, to individual and combined outcomes of mortality, cardiac arrest and higher-level of care transfer.

RESULTS

Twenty-percent (N = 1329) of RRT-patients had prolonged-CRT (vs normal-CRT), were twice as likely to die (36% vs 17.8%, p < .001), more likely to experience the combined outcome (72.1% vs 54.2%, p < .001) and had longer hospital length of stays, 15.3 (SD 0.3) vs 13.5 days (SD 0.5) (p < .001). Multivariable logistic regression for mortality ranked CRT second to hypoxia among all 11 variables evaluated (p < 001).

CONCLUSIONS

This is the first time CRT has been evaluated in RRT patients. Its measurement is easy to perform and proves useful as an assessment of adult patients at-risk for clinical decline. Its prolongation in our population was an independent predictor of mortality and the combined outcome. This study and others suggest that CRT should be considered further as a fundamental assessment of patients at-risk for clinical decline.