Peri-operative oxygen consumption revisited: An observational study in elderly patients undergoing major abdominal surgery

Personalized intraoperative arterial pressure management and mitochondrial oxygen tension in patients having major non-cardiac surgery: a pilot substudy of the IMPROVE trial

The "Cellular Oxygen METabolism" (COMET) system (Photonics Healthcare, Utrecht, The Netherlands) non-invasively measures mitochondrial oxygen tension (mitoPO2) in the skin. The effects of general anesthesia and major non-cardiac surgery on mitoPO2 remain unknown. In this pre-planned pilot substudy of the "Intraoperative blood pressure Management based on the individual blood PRessure profile: impact on postOperatiVE organ function" (IMPROVE) trial, we measured mitoPO2 from induction of general anesthesia until the end of surgery in 19 major non-cardiac surgery patients (10 assigned to personalized and 9 to routine intraoperative arterial pressure management). In the overall cohort, the median (25th to 75th percentile) preoperative awake mitoPO2 was 63 (53 to 82) mmHg and mitoPO2 after induction of general anesthesia was 42 (35 to 59) mmHg. The intraoperative average mitoPO2 was 39 (30 to 50) mmHg. Thirteen patients (68%) had intraoperative mitoPO2 values below 20 mmHg and the median percentage of surgical time with mitoPO2 < 20 mmHg was 17 (0 to 31)%. MitoPO2 was weakly correlated with mean arterial pressure (repeated measures correlation (rrm(n); rrm(984) = 0.26, 95% confidence interval 0.20 to 0.32; P < 0.001), but not meaningfully with heart rate (rrm(984) = -0.05, 95% confidence interval -0.11 to 0.01; P = 0.117). There was no important difference in intraoperative average mitoPO2 between patients assigned to personalized or to routine intraoperative arterial pressure management (P = 0.653). MitoPO2 under general anesthesia was about a quarter lower than preoperative awake mitoPO2, substantially fluctuated during major non-cardiac surgery, and transiently decreased below 20 mmHg in about two-thirds of the patients. Personalized - compared to routine - intraoperative arterial pressure management did not increase intraoperative mitoPO2. Whether intraoperative decreases in mitoPO2 are clinically meaningful warrants further investigation.

Changes in oxygen supply-demand balance during induction of general anesthesia: an exploratory study using remimazolam

PURPOSE

This study was performed to evaluate the changes in oxygen supply-demand balance during induction of general anesthesia using an indirect calorimeter capable of measuring oxygen consumption (VO2) and carbon dioxide production (VCO2).

METHODS

This study included patients scheduled for surgery in whom remimazolam was administered as a general anesthetic. VO2 and VCO2 were measured at different intervals: upon awakening (T1), 15 min after tracheal intubation (T2), and 1 h after T2 (T3). Oxygen delivery (DO2) was calculated simultaneously with these measurements. VO2 was ascertained using an indirect calorimeter and further calculated using vital signs, among other factors. DO2 was derived from cardiac output and arterial blood gas analysis performed with an arterial pressure-based cardiac output measurement system.

RESULTS

VO2, VCO2, and DO2 decreased significantly from T1 to T2 and T3 [VO2/body surface area (BSA) (ml/min/m2): T1, 130 (122-146); T2, 107 (83-139); T3, 97 (93-121); p = 0.011], [VCO2/BSA (ml/min/m2): T1, 115 (105-129); T2, 90 (71-107); T3, 81 (69-101); p = 0.011], [DO2/BSA (ml/min/m2): T1, 467 (395-582); T2, 347 (286-392); T3, 382 (238-414); p = 0.0020]. Among the study subjects, a subset exhibited minimal reduction in VCO2. Although the respiratory frequency was titrated on the basis of end-tidal CO2 levels, there was no significant difference between the groups.

CONCLUSION

General anesthetic induction with remimazolam decreased VO2, VCO2, and DO2.

Transitions from Aerobic to Anaerobic Metabolism and Oxygen Debt during Elective Major and Emergency Non-Cardiac Surgery

INTRODUCTION

Intraoperative hemodynamic and metabolic optimization of both the high-risk surgical patients and critically ill patients remains challenging. Reductions in oxygen delivery or increases in oxygen consumption can initiate complex cellular processes precipitating oxygen debt (OXD).

METHODS

This study tested the hypothesis that intraoperative changes in sublingual microcirculatory flow reflect clinically relevant transitions from aerobic to anaerobic metabolism (TRANAM). We included patients undergoing elective major and emergency non-cardiac surgery. Macro- and microcirculatory variables, oxygen extraction, and transitions of metabolism were assessed in both cohorts.

RESULTS

In the elective group, OXD was progressively increased over time, with an estimated 2.24 unit increase every 30 min (adjusted p < 0.001). Also, OXD was negatively correlated with central venous pressure (ρ = -0.247, adjusted p = 0.006) and positively correlated with stroke volume variation (ρ = 0.185, adjusted p = 0.041). However, it was not significantly correlated with sublingual microcirculation variables. In the emergency surgery group, OXD increased during the first two intraoperative hours and then gradually decreased until the end of surgery. In that cohort, OXD was positively correlated with diastolic arterial pressure (ρ = 0.338, adjpatients and the critically ill patients remains challengingsted p = 0.015). Also, OXD was negatively correlated with cardiac index (ρ = -0.352, adjusted p = 0.003), Consensus Proportion of Perfused Vessels (PPV) (ρ = -0.438, adjusted p < 0.001), and Consensus PPV (small) (ρ = -0.434, adjusted p < 0.001).

CONCLUSIONS

TRANAM were evident in both the elective major and emergency non-cardiac surgery cohorts independent of underlying alterations in the sublingual microcirculation.

Perioperative estimations of oxygen consumption from LiDCO™plus-derived cardiac output and Ca-cvO2 difference: Relationship with measurements by indirect calorimetry in elderly patients undergoing major abdominal surgery

BACKGROUND

Feasible estimations of perioperative changes in oxygen consumption (VO2) could enable larger studies of its role in postoperative outcomes. Current methods, either by reverse Fick calculations using pulmonary artery catheterisation or metabolic by breathing gas analysis, are often deemed too invasive or technically requiring. In addition, reverse Fick calculations report generally lower values of oxygen consumption.

METHODS

We investigated the relationship between perioperative estimations of VO2 (EVO2), from LiDCO™plus-derived (LiDCO Ltd, Cambridge, UK) cardiac output and arterial-central venous oxygen content difference (Ca-cvO2), with indirect calorimetry (GVO2) by QuarkRMR (COSMED srl. Italy), using data collected 2017-2018 during a prospective observational study on perioperative oxygen transport in 20 patients >65 years during epidural and general anaesthesia for open pancreatic or liver resection surgery. Eighty-five simultaneous intra- and postoperative measurements at different perioperative stages were analysed for prediction, parallelity and by traditional agreement assessment.

RESULTS

Unadjusted bias between GVO2 and EVO2 indexed for body surface area was 26 (95% CI 20 to 32) with limits of agreement (1.96SD) of -32 to 85 ml min-1m-2. Correlation adjusted for the bias was moderate, intraclass coefficient(A,1) 0.51(95% CI 0.34 to 0.65) [F (84,84) = 3.07, P<0.001]. There was an overall association between GVO2 and EVO2, in a random coefficient model [GVO2 = 73(95% CI 62 to 83) + 0.45(95% CI 0.29 to 0.61) EVO2 ml min-1m-2, P<0.0001]. GVO2 and EVO2 changed in parallel intra- and postoperatively when normalised to their respective overall means.

CONCLUSION

Based on this data, estimations from LiDCO™plus-derived cardiac output and Ca-cvO2 are not reliable as a surrogate for perioperative VO2. Results were in line with previous studies comparing Fick-based and metabolic measurements but limited by variability of data and possible underpowering. The parallelity at different perioperative stages and the prediction model can provide useful guidance and methodological tools for future studies on similar methods in larger samples.

Intraoperative Oxygen Consumption and Postoperative Immune Response in Colorectal Oncological Surgery: A Prospective, Monocentric Pilot Study

Surgical resection is the key treatment for colorectal cancer, but the extent of surgical trauma has been implied as a key factor for the oncologic outcome. The immune stress response to surgical trauma generates a cascade of immunological events implying neutrophils' perioperative change generating NETosis, N killer decrease, and platelets' activation that may influence postoperative surgical outcome, tumor cell growth, and future oncogenesis. The present study aimed to investigate the correlation between intraoperative oxygen consumption (VO2) and the dynamic variation of neutrophils, lymphocytes, and platelets in the perioperative period to identify an intraoperative tool that could predict the postoperative immune response. Twenty-six colorectal oncological surgical patients were enrolled in an observational, prospective, monocentric study, over 18 months. Serum neutrophils, lymphocytes, and thrombocytes values were collected in the preoperative period and on the third postoperative day, oxygen consumption was measured and recorded every 15 min during surgery using indirect calorimetry. We compared oxygen consumption measurements registered 30 min after induction of anesthesia (VO2a) and the first value registered after abdominal wall closure (VO2b) to perioperative variation of absolute neutrophils (VNC), lymphocytes (VLC), and platelets (VPC) count. Our results proved a significant correlation between VO2 variation and neutrophils' perioperative dynamic assessed by VNC (correlation coefficient = 0.547, p < 0.01, 95% confidence interval (CI) =0.175, 0.783). We also noticed a correlation between VPC and VO2 (correlation coefficient = -0.603, p < 0.01, 95% CI = -0.815, -0.248). No correlation could be shown between VO2 and VLC variation (p = 0.39). In conclusion, intraoperative VO2 variation measured by indirect calorimetry correlates well with perioperative neutrophils and platelets count dynamic variations and can be used as an early prognosis marker of postoperative immune response and surgical outcome in colorectal oncological surgery.

The microcirculation in perioperative medicine: a narrative review

The microcirculation describes the network of the smallest vessels in our cardiovascular system. On a microcirculatory level, oxygen delivery is determined by the flow of oxygen-carrying red blood cells in a given single capillary (capillary red blood cell flow) and the density of the capillary network in a given tissue volume (capillary vessel density). Handheld vital videomicroscopy enables visualisation of the capillary bed on the surface of organs and tissues but currently is only used for research. Measurements are generally possible on all organ surfaces but are most often performed in the sublingual area. In patients presenting for elective surgery, the sublingual microcirculation is usually intact and functional. Induction of general anaesthesia slightly decreases capillary red blood cell flow and increases capillary vessel density. During elective, even major, noncardiac surgery, the sublingual microcirculation is preserved and remains functional, presumably because elective noncardiac surgery is scheduled trauma and haemodynamic alterations are immediately treated by anaesthesiologists, usually restoring the macrocirculation before the microcirculation is substantially impaired. Additionally, surgery is regional trauma and thus likely causes regional, rather than systemic, impairment of the microcirculation. Whether or not the sublingual microcirculation is impaired after noncardiac surgery remains a subject of ongoing research. Similarly, it remains unclear if cardiac surgery, especially with cardiopulmonary bypass, impairs the sublingual microcirculation. The effects of therapeutic interventions specifically targeting the microcirculation remain to be elucidated and tested. Future research should focus on further improving microcirculation monitoring methods and investigating how regional microcirculation monitoring can inform clinical decision-making and treatment.

Energy Expenditure Under General Anesthesia: An Observational Study Using Indirect Calorimetry in Patients Having Noncardiac Surgery

BACKGROUND

Perioperative hemodynamic management aims to optimize organ perfusion pressure and blood flow-assuming this ensures that oxygen delivery meets cellular metabolic needs. Cellular metabolic needs are reflected by energy expenditure. A better understanding of energy expenditure under general anesthesia could help tailor perioperative hemodynamic management to actual demands. We thus sought to assess energy expenditure under general anesthesia. Our primary hypothesis was that energy expenditure under general anesthesia is lower than preoperative awake resting energy expenditure.

METHODS

We conducted an observational study on patients having elective noncardiac surgery at the University Medical Center Hamburg-Eppendorf (Germany) between September 2019 and March 2020. We assessed preoperative awake resting energy expenditure, energy expenditure under general anesthesia, and energy expenditure after surgery using indirect calorimetry. We compared energy expenditure under general anesthesia at incision to preoperative awake resting energy expenditure using a Wilcoxon signed-rank test for paired measurements.

RESULTS

We analyzed 60 patients. Median (95% confidence interval [CI]) preoperative awake resting energy expenditure was 953 (95% CI, 906-962) kcal d -1 m -2 . Median energy expenditure under general anesthesia was 680 (95% CI, 642-711) kcal d -1 m -2 -and thus 263 (95% CI, 223-307) kcal d -1 m -2 or 27% (95% CI, 23%-30%) lower than preoperative awake resting energy expenditure ( P < .001).

CONCLUSIONS

Median energy expenditure under general anesthesia is about one-quarter lower than preoperative awake resting energy expenditure in patients having noncardiac surgery.

Associations of systemic oxygen consumption with age and body temperature under general anesthesia: retrospective cohort study

BACKGROUND

Body temperature (BT) is thought to have associations with oxygen consumption (VO2). However, there have been few studies in which the association between systemic VO2 and BT in humans was investigated in a wide range of BTs. The aims of this study were 1) to determine the association between VO2 and age and 2) to determine the association between VO2 and BT.

METHODS

This study was a retrospective study of patients who underwent surgery under general anesthesia at a tertiary teaching hospital. VO2 was measured by the Dräger Perseus A500 anesthesia workstation (Dräger Medical, Lubeck, Germany). The associations of VO2 with age and BT were examined using spline regression and multivariable regression analysis with a random effect.

RESULTS

A total of 7,567 cases were included in this study. A linear spline with one knot shows that VO2 was reduced by 2.1 ml/kg/min with one year of age (p < 0.001) among patients less than 18 years of age and that there was no significant change in VO2 among patients 18 years of age or older (estimate: 0.014 ml/kg/min, p = 0.08). VO2 in all bands of BT < 36.0 °C was not significantly different from VO2 in BT >  = 36 °C and < 36.5 °C. Multivariable linear regression analysis showed that compared with VO2 in BT >  = 36 °C and < 36.5 °C as a reference, VO2 levels were significantly higher by 0.57 ml/kg/min in BT >  = 36.5 °C and < 37 °C (p < 0.001), by 1.8 ml/kg/min in BT >  = 37 °C and < 37.5 °C (p < 0.001), by 3.6 ml/kg/min in BT >  = 37.5 °C and < 38 °C (p < 0.001), by 4.9 ml/kg/min in BT >  = 38 °C and < 38.5 °C (p < 0.001), and by 5.7 ml/kg/min in BT >  = 38.5 °C (p < 0.001). The associations between VO2 and BT were significantly different among categorized age groups (p = 0.03).

CONCLUSIONS

VO2 increases in parallel with increase in body temperature in a hyperthermic state but remains constant in a hypothermic state. Neonates and infants, who have high VO2, may have a large systemic organ response in VO2 to change in BT.

Influence of Anesthetics on Cardiac Index and Metabolic Outcomes in Mitral and Aortic Valve Replacement in Adults: A Randomized Clinical Study

Background

Cardiac index (CI) and metabolic response to surgery are important indicators of the course of the intraoperative period.

Objectives

This study aimed to determine the effect of sevoflurane, isoflurane, and propofol on CI and metabolic outcomes during aortic and mitral valve replacement in adults.

Methods

In this single-center prospective randomized controlled clinical study, a total of 75 patients were randomly assigned into 3 groups according to the type of anesthesia: The propofol group (n = 25), the sevoflurane group (n = 25), and the isoflurane group (n = 25). Cardiac stroke volume (SV) was determined by intraesophageal echocardiography (SV = end-diastolic volume - end-systolic volume). Cardiac output (CO) and CI were calculated according to the formulas. Oxygen consumption during surgery = CI × arteriovenous difference. Indirect calorimetry was used to determine energy expenditure during anesthesia using a spirometry device.

Results

The use of anesthetics did not change CI. Cardiac index decreased from 3 to 2.9 L/min/m2 in the propofol group, increased from 3.1 to 3.2 L/min/m2 in the sevoflurane group, and decreased from 2.9 to 2.7 L/min/m2 in the isoflurane group. Compared to inhaled anesthetics, propofol significantly reduced VO2 from 179.1 to 135.7 mL/min/m2. Propofol reduced energy expenditure from 1483.7 to 1333.5 kcal.

Conclusions

Volatile anesthetics, propofol has practically no effect on CI in an uncomplicated surgery. Anesthesia with propofol is associated with lower VO2 and better oxygen delivery to tissues. Energy consumption during propofol anesthesia decreases.

Physiological relationship between cardiorespiratory fitness and fitness for surgery: a narrative review

Epidemiological evidence has highlighted a strong relationship between cardiorespiratory fitness and surgical outcomes; specifically, fitter patients possess heightened resilience to withstand the surgical stress response. This narrative review draws on exercise and surgical physiology research to discuss and hypothesise the potential mechanisms by which higher fitness affords perioperative benefit. A higher fitness, as indicated by higher peak rate of oxygen consumption and ability to sustain metabolic homeostasis (i.e. higher anaerobic threshold) is beneficial postoperatively when metabolic demands are increased. However, the associated adaptations with higher fitness, and the related participation in regular exercise or physical activity, might also underpin the observed perioperative benefit through a process of hormesis, a protective adaptive response to the moderate and intermittent stress of exercise. Potential mediators discussed include greater antioxidant capacity, metabolic flexibility, glycaemic control, lean body mass, and improved mood.

The use of a vascular occlusion test combined with near-infrared spectroscopy in perioperative care: a systematic review

In the perioperative phase oxygen delivery and consumption can be influenced by different factors, i.e. type of surgery, anesthetic and cardiovascular drugs, or fluids. By combining near-infrared spectroscopy (NIRS) monitoring of regional tissue oxygen saturation (StO₂) with an ischemic provocation test, the vascular occlusion test (VOT), local tissue oxygen consumption and vascular reactivity at the microcirculatory level can be assessed. This systematic review aims to give an overview of the clinical information that VOT-derived NIRS values can provide in the perioperative period. After performing a systematic literature search, we included 29 articles. It was not possible to perform a meta-analysis because of the lack of comparable data and the observational nature of the majority of the included articles. We have clustered the found articles in two groups: non-cardiac surgery and cardiac surgery. We found that VOT-derived NIRS values show a wide variability and are influenced by the effects of anesthetics, cardiovascular drugs, fluids, and by the type of surgery. Additionally, deviations in VOT-derived NIRS values are also associated with adverse patients' outcomes, such as postoperative complications, prolonged mechanical ventilation and prolonged hospital length of stay. However, given the variability in VOT-derived NIRS values, clinical applicability remains elusive. Future clinical interventional trials might provide additional insight into the potential of VOT associated with NIRS to optimize perioperative care by targeting specific interventions to optimize the function of the microvasculature.

Perioperative risk assessment - focus on functional capacity

PURPOSE OF REVIEW

This review examines how functional capacity informs preoperative risk stratification, as well as strengths and limitations of options for estimating functional capacity.

RECENT FINDINGS

Functional capacity (or cardiopulmonary fitness) overlaps with other important characteristics, including muscular strength, balance, and frailty. Poor functional capacity is associated with postoperative morbidity, especially noncardiovascular complications. Both patient interviews and exercise tests are used to assess functional capacity. The usual approach of an unstructured patient interview does not predict outcomes. Structured interviews that incorporate validated questionnaires (Duke Activity Status Index) or standardized questions about physical activity (ability to climb stairs) do predict moderate-or-severe complications and cardiovascular complications. Among exercise tests, cardiopulmonary exercise testing (CPET) has shown the most consistent association with risks of complications. Other tests (6-min walk test, incremental shuttle walk test, stair climbing) might predict complications, but still require further high-quality evaluation.

SUMMARY

A straightforward way to better assess functional capacity is a structured interview with validated questionnaires or standardized questions about physical activities. Functional capacity can also be assessed by exercise tests, with the strongest evidence supporting CPET. Although some simpler exercise tests have shown promise, more research remains needed to better define their role in preoperative evaluation.