Association between muscular tissue desaturation and acute kidney injury in older patients undergoing major abdominal surgery: a prospective cohort study

PURPOSE

Present study was designed to investigate the association between muscular tissue desaturation and acute kidney injury (AKI) in older patients undergoing major abdominal surgery.

METHOD

A total of 253 patients (≥ 65 years old) who underwent abdominal surgery with expected duration ≥ 2 h were enrolled. Muscular tissue oxygen saturation (SmtO2) was monitored at quadriceps and bilateral flanks during surgery. Muscular desaturation was defined as SmtO2 < 90% baseline lasting for > 60 s. The primary outcome was the incidence of AKI within postoperative 7 days. The association between muscular desaturation and AKI was analyzed by multivariable logistic regression model. The secondary outcomes indicated the other complications within postoperative 30 days.

RESULTS

Among 236 patients, 44 (18.6%) of them developed AKI. The incidence of muscular desaturation at quadriceps was 28.8% (68/236). Patients with muscular desaturation had higher incidence of AKI than those without desaturation (27.9% [19/68], vs. 14.9% [25/168], P = 0.020). After adjustment of confounders, multivariable analysis showed that muscular desaturation at quadriceps was significantly associated with an increased risk of AKI (OR = 2.84, 95% CI 1.21-6.67, P = 0.016). Muscular desaturations at left and right flank were also associated with an increased risk of AKI (OR = 6.38, 95% CI 1.78-22.89, P = 0.004; OR = 8.90, 95% CI 1.42-45.63; P = 0.019, respectively). Furthermore, patients with muscular desaturation may have a higher risk of pulmonary complications, sepsis and stroke at 30-day follow-up.

CONCLUSION

Muscular desaturation was associated with postoperative AKI in older patients undergoing major abdominal surgery which may serve as a predictor of AKI.

Respiratory Monitoring During Mechanical Ventilation: The Present and the Future

The increased application of mechanical ventilation, the recognition of its harms and the interest in individualization raised the need for an effective monitoring. An increasing number of monitoring tools and modalities were introduced over the past 2 decades with growing insight into asynchrony, lung and chest wall mechanics, respiratory effort and drive. They should be used in a complementary rather than a standalone way. A sound strategy can guide a reduction in adverse effects like ventilator-induced lung injury, ventilator-induced diaphragm dysfunction, patient-ventilator asynchrony and helps early weaning from the ventilator. However, the diversity, complexity, lack of expertise, and associated cost make formulating the appropriate monitoring strategy a challenge for clinicians. Most often, a big amount of data is fed to the clinicians making interpretation difficult. Therefore, it is fundamental for intensivists to be aware of the principle, advantages, and limits of each tool. This analytic review includes a simplified narrative of the commonly used basic and advanced respiratory monitors along with their limits and future prospective.

Muscular tissue desaturation and pneumonia in patients receiving lung cancer surgery: a cohort study

BACKGROUND

Post-operative pneumonia (POP) is a common complication of lung cancer surgery, and muscular tissue oxygenation is a root cause of post-operative complications. However, the association between muscular tissue desaturation and POP in patients receiving lung cancer surgery has not been specifically studied. This study aimed to investigate the potential use of intra-operative muscular tissue desaturation as a predictor of POP in patients undergoing lung cancer surgery.

METHODS

This cohort study enrolled patients (≥55 years) who had undergone lobectomy with one-lung ventilation. Muscular tissue oxygen saturation (SmtO 2 ) was monitored in the forearm (over the brachioradialis muscle) and upper thigh (over the quadriceps) using a tissue oximeter. The minimum SmtO 2 was the lowest intra-operative measurement at any time point. Muscular tissue desaturation was defined as a minimum baseline SmtO 2 of <80% for >15 s. The area under or above the threshold was the product of the magnitude and time of desaturation. The primary outcome was the association between intra-operative muscular tissue desaturation and POP within seven post-operative days using multivariable logistic regression. The secondary outcome was the correlation between SmtO 2 in the forearm and that in the thigh.

RESULTS

We enrolled 174 patients. The overall incidence of muscular desaturation (defined as SmtO 2 < 80% in the forearm at baseline) was approximately 47.1% (82/174). The patients with muscular desaturation had a higher incidence of pneumonia than those without desaturation (28.0% [23/82] vs. 12.0% [11/92]; P  = 0.008). The multivariable analysis revealed that muscular desaturation was associated with an increased risk of pneumonia (odds ratio: 2.995, 95% confidence interval: 1.080-8.310, P  = 0.035) after adjusting for age, American Society of Anesthesiologists status, Assess Respiratory Risk in Surgical Patients in Catalonia score, smoking, use of peripheral nerve block, propofol, and study center.

CONCLUSION

Muscular tissue desaturation, defined as a baseline SmtO 2 < 80% in the forearm, may be associated with an increased risk of POP.

TRIAL REGISTRATION

No. ChiCTR-ROC-17012627.

Agreement of somatic and renal near-infrared spectroscopy with reference blood samples during a controlled hypoxia sequence: a healthy volunteer study

Purpose: O3® Regional Oximetry (Masimo Corporation, California, USA) is validated for cerebral oximetry. We aimed to assess agreement of somatic and renal near-infrared spectroscopy with reference blood samples. Methods: O3 sensors were placed bilaterally on the quadriceps and flank of 26 healthy volunteers. A stepped, controlled hypoxia sequence was performed by adding a mixture of nitrogen and room air to the breathing circuit. O3-derived oxygen saturation values were obtained at baseline and at six decremental saturation levels (5% steps). Blood samples (radial artery, iliac vein (somatic reference) and renal vein) were obtained at each step. Reference values were calculated as: 0.7 × venous saturation + 0.3 × arterial saturation. The agreement between O3-derived values with blood reference values was assessed by calculating root-mean-square error accuracy and Bland-Altman plots. Results: The root-mean-square error accuracy was 6.0% between quadriceps oxygen saturation and somatic reference values. The mean bias was 0.8%, with limits of agreement from -7.7 to 9.3%. These were 5.1% and 0.6% (-8.3 to 9.5%) for flank oxygen saturation and somatic reference values, respectively, and 7.7% and -4.9% (-15.0 to 5.2%) for flank oxygen saturation and renal reference values. The kidney depth was 3.1 ± 0.9 cm below the skin. Conclusion: O3 regional oximetry can be used on the quadriceps and flank to monitor somatic saturation, yet has a saturation-level dependent bias. O3-derived values obtained at the flank underestimated renal reference values. Additionally, it is unlikely that the flank sensors did directly measure renal tissue. Trial registration: Clinicaltrials.gov (NCT04584788): registered October 6th, 2020.

Which Predictor, SctO2 or SstO2, Is more Sensitive for Postoperative Cognitive Dysfunction in Spine Surgery: A Prospective Observational Study?

OBJECTIVE

Patients undergoing spinal surgery in the prone position may experience venous stasis, often resulting in edema in dependent areas of the body, including the head, and increased postoperative cognitive dysfunction (POCD). Not only does POCD present challenges for post-operative care and recovery, it can also cause permanent damage to the patient's brain and increase mortality and social costs. We aimed to clarify the incidence of POCD in patients with hypertension after prone spine surgery and to further determine the association between intraoperative somatic tissue oxygen saturation (SstO2)/cerebral tissue oxygen saturation (SctO2) and POCD.

METHODS

Patients with hypertension scheduled for open prone spine surgery from January 2020 to April 2021 were included in this single-center, prospective, observational study. SctO2 and SstO2 were monitored by near-infrared spectroscopy continuously throughout the surgery. The primary outcome was POCD assessed using the Mini-Mental Status Examination (MMSE). The association of SstO2 and SctO2 with POCD was evaluated with unadjusted analyses and multivariable logistic regression.

RESULTS

One hundred and one of 112 identified patients were included, 28 (27.8%) of whom developed POCD. None of the investigated SctO2 indices were predictive of POCD. However, the patients with POCD had greater decreases in intraoperative absolute SstO2 and relative SstO2 than the patients without POCD (P = 0.037, P = 0.036). Moreover, three SstO2 indices were associated with POCD, including a greater absolute SstO2 decrease (P = 0.021), a greater relative SstO2 decrease (P = 0.032), and a drop below 90% of the baseline SstO2 (P = 0.002), independent of ASA III status, preoperative platelets and postoperative sepsis. In addition, there was no correlation between intraoperative SctO2 and intraoperative SstO2 or between their respective absolute declines.

CONCLUSION

Twenty-eight (27.7%) of 101 patients developed POCD in patients with hypertension undergoing prone spine surgery, and intraoperative SstO2 is associated with POCD, whereas SctO2 shows no association with POCD. This study may initially provide a valuable new approach to the prevention of POCD in this population.

Association between tissue oxygenation and myocardial injury in patients undergoing major spine surgery: a prospective cohort study

OBJECTIVE

To describe the association between intraoperative tissue oxygenation and postoperative troponin elevation in patients undergoing major spine surgery. We hypothesised that a decrease in intraoperative skeletal muscle tissue oxygenation (SmO₂) was associated with the peak postoperative cardiac troponin value.

DESIGN

This is a prospective cohort study.

SETTING

Single-centre, University of California San Francisco Medical Center.

PARTICIPANTS

Seventy adult patients undergoing major elective spine surgery.

PRIMARY AND SECONDARY OUTCOME MEASURES

High-sensitivity troponin T (hsTnT) was measured in plasma preoperatively and on the first and second day after surgery to assess the primary outcome of peak postoperative hsTnT. Secondary outcomes included MINS and intensive care unit (ICU) admission within 30 days. Skeletal cerebral tissue oxygenation and SmO₂ was measured continuously with near-infrared spectroscopy during surgery. The primary exposure variable was time-weighted area under the curve (TW AUC) for SmO₂.

RESULTS

Mean age was 65 (33-85) years and 59% were female. No significant association was found between TW AUC for SmO₂ and peak hsTnT (Spearman's correlation, r_s=0.17, p=0.16). A total of 28 (40%) patients had MINS. ICU admission occurred in 14 (40%) in lower vs 25 (71%) in upper half of patients based on TW AUC for SmO₂, p=0.008.

CONCLUSIONS

Decrease in SmO₂ was not a statistically significant predictor for peak troponin value following major spine surgery but is a potential predictor for other postoperative complications.

TRIAL REGISTRATION NUMBER

NCT03518372.

Renal tissue desaturation and acute kidney injury in infant cardiac surgery: a prospective propensity score-matched cohort study

BACKGROUND

Previous studies on the association between renal tissue desaturation and acute kidney injury (AKI) in infant cardiac surgery are limited by small sample sizes and inconsistent results. This prospective study aimed to determine the association between renal desaturation and AKI in infants undergoing surgical repair of an isolated ventricular septal defect (VSD).

METHODS

Infants undergoing VSD repair involving cardiopulmonary bypass participated in this prospective cohort study. The exposure of interest was renal tissue desaturation, defined as at least 20% decrease in saturation from baseline for at least 60 consecutive seconds. Intraoperative care was not guided by renal oxygenation, as the anaesthesiologists were blinded to the monitor. The outcome was AKI arising within postoperative Days 1-3. The primary analysis was based on propensity score-matched infants with and without intraoperative renal desaturation.

RESULTS

Intraoperative renal desaturation was detected in 38 of 242 infants using near-infrared spectroscopy. This group of infants was matched with 114 infants without intraoperative renal saturation after propensity score matching. Acute kidney injury occurred in 47% (18/38) and 27% (31/114) of infants with or without renal desaturation, respectively. Infants with renal desaturation had higher odds of developing AKI than infants without renal desaturation based on conditional logistic regression (odds ratio 2.79; 95% confidence interval: 1.21-6.44; P=0.016). The cumulative time of renal desaturation correlated moderately with the ratio of postoperative peak creatinine to preoperative baseline creatinine (r=0.51; P<0.001).

CONCLUSIONS

Intraoperative renal desaturation is associated with increased odds of developing AKI after surgical repair of an isolated VSD involving cardiopulmonary bypass in infants.

CLINICAL TRIAL REGISTRATION

NCT03941015.

Association Between Cerebral Desaturation and Postoperative Delirium in Thoracotomy With One-Lung Ventilation: A Prospective Cohort Study

BACKGROUND

The association between cerebral desaturation and postoperative delirium in thoracotomy with one-lung ventilation (OLV) has not been specifically studied.

METHODS

A prospective observational study performed in thoracic surgical patients. Cerebral tissue oxygen saturation (Scto2) was monitored on the left and right foreheads using a near-infrared spectroscopy oximeter. Baseline Scto2 was measured with patients awake and breathing room air. The minimum Scto2 was the lowest measurement at any time during surgery. Cerebral desaturation and hypersaturation were an episode of Scto2 below and above a given threshold for ≥15 seconds during surgery, respectively. The thresholds based on relative changes by referring to the baseline measurement were <80%, <85%, <90%, <95%, and <100% baseline for desaturation and >105%, >110%, >115%, and >120% baseline for hypersaturation. The thresholds based on absolute values were <50%, <55%, <60%, <65%, and <70% for desaturation and >75%, >80%, >85%, and >90% for hypersaturation. The given area under the threshold (AUT)/area above the threshold (AAT) was analyzed. Delirium was assessed until postoperative day 5. The primary analysis was the association between the minimum Scto2 and delirium using multivariable logistic regression controlled for confounders (age, OLV time, use of midazolam, occurrence of hypotension, and severity of pain). The secondary analysis was the association between cerebral desaturation/hypersaturation and delirium, and between the AUT/AAT and delirium using multivariable logistic regression controlled for the same confounders. Multiple testing was corrected using the Holm-Bonferroni method. We additionally monitored somatic tissue oxygen saturation on the forearm and upper thigh.

RESULTS

Delirium occurred in 35 (20%) of 175 patients (65 ± 6 years old). The minimum left or right Scto2 was not associated with delirium. Cerebral desaturation defined by <90% baseline for left Scto2 (odds ratio [OR], 5.82; 95% confidence interval [CI], 2.12-19.2; corrected P =.008) and <85% baseline for right Scto2 (OR, 4.27; 95% CI, 1.77-11.0; corrected P =.01) was associated with an increased risk of delirium. Cerebral desaturation defined by other thresholds, cerebral hypersaturation, the AUT/AAT, and somatic desaturation and hypersaturation were all not associated with delirium.

CONCLUSIONS

Cerebral desaturation defined by <90% baseline for left Scto2 and <85% baseline for right Scto2, but not the minimum Scto2, may be associated with an increased risk of postthoracotomy delirium. The validity of these thresholds needs to be tested by randomized controlled trials.

A novel predictive model of intraoperative blood loss in patients undergoing elective lumbar surgery for degenerative pathologies

BACKGROUND CONTEXT

Intraoperative blood loss (IOBL) is unavoidable during surgery; however, high IOBL is associated with increased morbidity and increased risk for requiring allogenic blood transfusion, itself associated with poorer outcomes.

PURPOSE

Here we sought to develop and validate a predictive calculator for IOBL that could be used by surgeons to estimate likely blood loss.

STUDY DESIGN/SETTING

Retrospective cohort.

PATIENT SAMPLE

Series of consecutive patients who underwent elective lumbar spine surgery for degenerative pathologies over a 27-month period at a single tertiary care center.

OUTCOME MEASURES

Primary outcome was IOBL. Secondary outcome was the occurrence of "major intraoperative bleeding," defined as IOBL exceeding 1 L.

METHODS

Charts of included patients were reviewed for medical comorbidities, preoperative laboratory data, surgical plan, and anesthesia records. Univariate linear regressions were performed to find significant predictors of IOBL, which were then subjected to a multivariate analysis to identify the final model. Model training was performed using 70% of the included cohort and external validation was performed using 30% of the cohort. Results of the model were deployed as a freely available online calculator.

RESULTS

We identified 1,281 patients who met inclusion/exclusion criteria. Mean age was 60±15 years, mean Charlson Comorbidity score was 1.1±1.6, and 51.8% were male. There were no significant differences between the training and validation cohorts with regard to any of the demographic variables or intraoperative variables; tranexamic acid use and surgical invasiveness were also similar in both cohorts. Multivariate analysis identified body mass index (βₙ=7.14; 95% confidence interval [3.15, 11.13]; p<.001), surgical invasiveness (βₙ=29.18; [24.62, 33.74]; p<.001), tranexamic acid use (βₙ=-0.093; [-0.171, -0.014]; p=.02), and surgical duration (βₙ=2.13; [1.75, 2.51]; p<.001) as significant predictors of IOBL. The model had an overall fit of r=0.693 in the validation cohort. Construction of a receiver-operating curve for predicting major IOBL showed a C-statistic of 0.895 within the validation cohort.

CONCLUSION

Here we identify and validate a model for predicting IOBL in patients undergoing lumbar spine surgery. The model was a moderately strong predictor of absolute IOBL and was demonstrated to predict the occurrence of major IOBL with a high degree of accuracy. We propose it may have future utility when counseling patients about surgical morbidity and the probability of requiring transfusion.

Discussion: can upper extremity (deltoid) near infrared spectroscopy be used to assess cerebral tissue bed saturation on femorally cannulated veno-arterial extracorporeal membrane oxygenation patients?

Continuous cerebral tissue saturation monitoring with near infrared spectroscopy may help clinicians identify cerebral desaturation early; however, patients have reported discomfort from near infrared spectroscopy monitoring pads on the forehead. This study aims to compare upper extremity near infrared spectroscopy monitoring to cerebral near infrared spectroscopy monitoring to assess its viability as a surrogate for cerebral saturation. A retrospective analysis of 10 femorally cannulated veno-arterial extracorporeal membrane oxygenation patients was performed comparing left (L) and right (R) upper extremity (deltoid) near infrared spectroscopy monitoring to cerebral near infrared spectroscopy monitoring (n = 20 data sets, 10 left and 10 right) and right radial blood gasses. Deltoid and cerebral near infrared spectroscopy values were recorded every 15 minutes for at least 24 hours when possible, were plotted on scatter grams, and were analyzed using Pearson product-moment coefficient (r). Based on the concept of covariance, a moderate-good relationship r = 0.50-0.75 was noted in 10% (n = 2) of the study group. A fair relationship r = 0.25-0.50 was noted in 50% (n = 10), and little or no relationship was noted in 40% (n = 8). None of the study group displayed a good to excellent relationship (r = 0.75 or above). In addition, coefficient of multiple determination for multiple regression R² was calculated and strong fit of the regression line was not noted. Although cerebral near infrared spectroscopy monitoring has been extremely helpful in identifying low cerebral tissue saturation on veno-arterial extracorporeal membrane oxygenation patients, the use of upper extremity (peripheral deltoid) tissue monitoring does not provide adequate correlation and should not be used as a surrogate to cerebral monitoring.

Muscular Tissue Oxygen Saturation and Posthysterectomy Nausea and Vomiting

Background

Suboptimal tissue perfusion and oxygenation during surgery may be responsible for postoperative nausea and vomiting in some patients. This trial tested the hypothesis that muscular tissue oxygen saturation–guided intraoperative care reduces postoperative nausea and vomiting.

Methods

This multicenter, pragmatic, patient- and assessor-blinded randomized controlled (1:1 ratio) trial was conducted from September 2018 to June 2019 at six teaching hospitals in four different cities in China. Nonsmoking women, 18 to 65 yr old, and having elective laparoscopic surgery involving hysterectomy (n = 800) were randomly assigned to receive either intraoperative muscular tissue oxygen saturation–guided care or usual care. The goal was to maintain muscular tissue oxygen saturation, measured at flank and on forearm, greater than baseline or 70%, whichever was higher. The primary outcome was 24-h postoperative nausea and vomiting. Secondary outcomes included nausea severity, quality of recovery, and 30-day morbidity and mortality.

Results

Of the 800 randomized patients (median age, 50 yr [range, 27 to 65]), 799 were assessed for the primary outcome. The below-goal muscular tissue oxygen saturation area under the curve was significantly smaller in patients receiving muscular tissue oxygen saturation–guided care (n = 400) than in those receiving usual care (n = 399; flank, 50 vs. 140% · min, P &lt; 0.001; forearm, 53 vs. 245% · min, P &lt; 0.001). The incidences of 24-h postoperative nausea and vomiting were 32% (127 of 400) in the muscular tissue oxygen saturation–guided care group and 36% (142 of 399) in the usual care group, which were not significantly different (risk ratio, 0.89; 95% CI, 0.73 to 1.08; P = 0.251). There were no significant between-group differences for secondary outcomes. No harm was observed throughout the study.

Conclusions

In a relatively young and healthy female patient population, personalized, goal-directed, muscular tissue oxygen saturation–guided intraoperative care is effective in treating decreased muscular tissue oxygen saturation but does not reduce the incidence of 24-h posthysterectomy nausea and vomiting.

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Electroencephalography and Brain Oxygenation Monitoring in the Perioperative Period

Maintaining brain function and integrity is a pivotal part of anesthesiological practice. The present overview aims to describe the current role of the 2 most frequently used monitoring methods for evaluation brain function in the perioperative period, ie, electroencephalography (EEG) and brain oxygenation monitoring. Available evidence suggests that EEG-derived parameters give additional information about depth of anesthesia for optimizing anesthetic titration. The effects on reduction of drug consumption or recovery time are heterogeneous, but most studies show a reduction of recovery times if anesthesia is titrated along processed EEG. It has been hypothesized that future EEG-derived indices will allow a better understanding of the neurophysiological principles of anesthetic-induced alteration of consciousness instead of the probabilistic approach most often used nowadays.Brain oxygenation can be either measured directly in brain parenchyma via a surgical burr hole, estimated from the venous outflow of the brain via a catheter in the jugular bulb, or assessed noninvasively by near-infrared spectroscopy. The latter method has increasingly been accepted clinically due to its ease of use and increasing evidence that near-infrared spectroscopy-derived cerebral oxygen saturation levels are associated with neurological and/or general perioperative complications and increased mortality. Furthermore, a goal-directed strategy aiming to avoid cerebral desaturations might help to reduce these complications. Recent evidence points out that this technology may additionally be used to assess autoregulation of cerebral blood flow and thereby help to titrate arterial blood pressure to the individual needs and for bedside diagnosis of disturbed autoregulation.

The effects of ventilation on left-to-right shunt and regional cerebral oxygen saturation: a self-controlled trial

BACKGROUND

Increase of pulmonary vascular resistance (PVR) is an efficient method of modulating pulmonary and systemic blood flows (Qp/Qs) for patients with left-to-right (L-R) shunt, and is also closely associated with insufficient oxygen exchange for pulmonary hypoperfusion. So that it might be a preferred regime of maintaining arterial partial pressure of carbon dioxide tension (PaCO₂) within an optimal boundary via ventilation management in congenital heart disease (CHD) patients for the inconvenient measure of the PVR and Qp/Qs. However, the appropriate range of PaCO₂ and patient-specific mechanical ventilation settings remain controversial for CHD children with L-R shunt.

METHODS

Thirty-one pediatric patients with L-R shunt, 1-6 yr of age, were included in this observation study. Patients were ventilated with tidal volume (V_T) of 10, 8 and 6 ml/kg in sequence, and 15 min stabilization period for individual V_T. The velocity time integral (VTI) of L-R shunt, pulmonary artery (PA) and descending aorta (DA) were measured with transesophageal echocardiography (TEE) after an initial 15 min stabilization period for each V_T, with arterial blood gas analysis. Near-infrared spectroscopy sensor were positioned on the surface of the bilateral temporal artery to monitor the change in regional cerebral oxygen saturation (rScO₂).

RESULTS

PaCO₂ was 31.51 ± 0.65 mmHg at V_T 10 ml/kg vs. 37.15 ± 0.75 mmHg at V_T 8 ml/kg (P < 0.03), with 44.24 ± 0.99 mmHg at V_T 6 ml/kg significantly higher than 37.15 ± 0.75 mmHg at V_T 8 ml/kg. However, PaO₂ at a V_T of 6 ml/kg was lower than that at a V_T of 10 ml/kg (P = 0.05). Meanwhile, 72% (22/31) patients had PaCO₂ in the range of 40-50 mmHg at V_T 6 ml/kg. VTI of L-R shunt and PA at V_T 6 ml/kg were lower than that at V_T of 8 and 10 ml/kg (P < 0.05). rScO₂ at a V_T of 6 ml/kg was higher than that at a V_T of 8 and 10 ml/kg (P < 0.05), with a significantly correlation between rScO₂ and PaCO₂ (r = 0.53). VTI of PA in patients with defect diameter > 10 mm was higher that that in patients with defect diameter ≤ 10 mm.

CONCLUSIONS

Maintaining PaCO₂ in the boundary of 40-50 mmHg with V_T 6 ml/kg might be a feasible ventilation regime to achieve better oxygenation for patients with L-R shunt. Continue raising PaCO₂ should be careful.

TRAIL REGISTRATION

Clinical Trial Registry of China (http://www.chictr.org.cn) identifier: ChiCTR-OOC-17011338 , prospectively registered on May 9, 2017.

Intraoperative physiological ranges associated with improved outcomes after major spine surgery: an observational study

OBJECTIVE

There is inadequate information about the values of many intraoperative physiological measurements that are associated with improved outcomes after surgery. The purpose of this observational study is to investigate the optimal physiological ranges during major spine surgery.

SETTING

A teaching hospital in the USA.

PARTICIPANTS

A convenience sample of 102 patients receiving major posterior spine surgery with multilevel spinal fusion in a prone position.

METHODS

Physiological variables, including but not limited to mean arterial pressure (MAP) and cerebral and somatic tissue oxygen saturation (SctO₂/SstO₂), were recorded. The results of these measurements were associated with length of hospital stay and composite complication data and were analysed based on thresholds (ie, a cut-off value for optimal and suboptimal physiology) and the area under the curve (AUC) values. The AUC values were measured as the area enclosed by the actual tracing and the threshold. The outcomes were dichotomised into above-average and below-average (ie, improved) categories.

RESULTS

Analyses based on thresholds identified the following variables associated with above-average outcomes: MAP <60 mm Hg, temperature <35°C, heart rate >90 beats per minute (bpm), SctO₂ <60% and SstO₂ >80%. Analyses based on AUC values identified the following as associated with above-average outcomes: MAP <70 and >100 mm Hg, temperature <36°C, heart rate >90 bpm, tidal volume (based on ideal body weight)<6 mL/kg, tidal volume (based on actual body weight) >10 mL/kg and peak airway pressure <15 cmH₂O.

CONCLUSION

The following physiological ranges are associated with improved outcomes (ie, shorter hospitalisation and fewer complications) during major spine surgery: MAP of 70-100 mm Hg, temperature ≥36°C, heart rate <90 bpm, tidal volume based on ideal body weight >6 mL/kg, SctO₂ >60% and SstO₂ <80%.

Tourniquet-induced tissue hypoxia characterized by near-infrared spectroscopy during ankle surgery: an observational study

BACKGROUND

Pneumatic tourniquet inflation during extremity surgery leads to profound and prolonged tissue ischemia. Its effect on tissue oxygenation is inadequately studied.

METHODS

Patients undergoing elective ankle surgery with tourniquet application participated in this observational cohort study. Somatic and cerebral tissue oxygen saturation (SstO₂ and SctO₂) were monitored using tissue near-infrared spectroscopy. Oxygenation was monitored distally (SstO₂-distal) and proximally to the tourniquet, on the contralateral leg, and the forehead (a total of 4 tissue beds). Tissue oxygenation at different time points was compared. The magnitude, duration, and load (product of magnitude and duration) of tissue desaturation during tourniquet inflation were correlated with tissue resaturation and hypersaturation after tourniquet deflation.

RESULTS

Data of 26 patients were analyzed. The tourniquet inflation time was 120 ± 31 mins. Following a rapid desaturation from 77 ± 8% pre-inflation to 38 ± 20% 10 mins post-inflation, SstO₂-distal slowly and continuously desaturated and reach the nadir (16 ± 11%) toward the end of inflation. After deflation, SstO₂-distal rapidly resaturated from 16 ± 11% to 91 ± 5% (i.e., hypersaturation); SstO₂ monitored proximally to the tourniquet and on contralateral leg had significant but small desaturation (~ 2-3%, p <  0.001); in contrast, SctO₂ remained stable. The desaturation load had a significant correlation with resaturation magnitude (p <  0.001); while the desaturation duration had a significant correlation with hypersaturation magnitude (p = 0.04).

CONCLUSIONS

Tissue dys-oxygenation following tourniquet application can be reliably monitored using tissue oximetry. Its outcome significance remains to be determined.

Muscular tissue oxygen saturation during robotic hysterectomy and postoperative nausea and vomiting: exploring the potential therapeutic thresholds

The relationship between muscular tissue oxygen saturation (SmtO₂) during surgery and postoperative nausea and vomiting (PONV) remains to be determined. Patients undergoing robotic hysterectomy participated in this prospective cohort study. SmtO₂ of the brachioradialis muscle in the forearm was continuously monitored during surgery. Thresholds based on relative changes or absolute values were systematically assigned. The relationship between thresholds and PONV was investigated based on threshold analysis (i.e., exceeding or not exceeding a threshold), area under the curve analysis (i.e., the size of the area enclosed by the SmtO₂ trace and threshold), and multivariable analysis by accounting for recognized PONV risk factors. PONV occurred in 35 of 106 patients (33%). Based on the multivariable analysis, the SmtO₂ threshold of 20% above baseline correlated with less PONV (OR 0.39; 95% CI 0.16-0.93; p = 0.034), and the following values correlated with more PONV: 5% below baseline (OR 2.37; 95% CI 1.26-4.45; p = 0.007), 20% below baseline (OR 16.08; 95% CI 3.05-84.73; p = 0.001), < 70% (OR 2.86; 95% CI 1.17-6.99; p = 0.021) and < 60% (OR 6.55; 95% CI 1.11-38.53; p = 0.038). Our study suggests that a potential therapeutic goal for PONV prophylaxis may be to maintain SmtO₂ at > 70% and above baseline.