Effect of opioid-free versus opioid-based strategies during multimodal anaesthesia on postoperative morphine consumption after bariatric surgery: a randomised double-blind clinical trial.

Background: The efficacy and safety of opioid-free anaesthesia during bariatric surgery remain debated, particularly when administering multimodal analgesia. As multimodal analgesia has become the standard of care in many centres, we aimed to determine if such a strategy coupled with either dexmedetomidine (opioid-free anaesthesia) or remifentanil with a morphine transition (opioid-based anaesthesia), would reduce postoperative morphine requirements and opioid-related adverse events. Methods: In this prospective double-blind study, 172 class III obese patients having laparoscopic gastric bypass surgery were randomly allocated to receive either sevoflurane-dexmedetomidine anaesthesia with a continuous infusion of lidocaine and ketamine (opioid-free group) or sevoflurane-remifentanil anaesthesia with a morphine transition (opioid-based group). Both groups received at anaesthesia induction a bolus of magnesium, lidocaine, ketamine, paracetamol, diclofenac, and dexamethasone. The primary outcome was 24-h postoperative morphine consumption. Secondary outcomes included postoperative quality of recovery (QoR40), incidence of hypoxaemia, bradycardia, and postoperative nausea and vomiting (PONV). Results: Eighty-six patients were recruited in each group (predominantly women, 70% had obstructive sleep apnoea). There was no significant difference in postoperative morphine consumption (median [inter-quartile range]: 16 [13-26] vs 15 [10-24] mg, P=0.183). The QoR40 up to postoperative day 30 did not differ between groups, but PONV was less frequent in the opioid-free group (37% vs 59%, P=0.005). Hypoxaemia and bradycardia were not different between groups. Conclusions: During bariatric surgery, a multimodal opioid-free anaesthesia technique did not decrease postoperative morphine consumption when compared with a multimodal opioid-based strategy. Quality of recovery did not differ between groups although the incidence of PONV was less in the opioid-free group. Clinical trial registration: NCT05004519.

Control of mean arterial pressure using a closed-loop system for norepinephrine infusion in severe brain injury patients: the COMAT randomized controlled trial.

Brain injury patients require precise blood pressure (BP) management to maintain cerebral perfusion pressure (CPP) and avoid intracranial hypertension. Nurses have many tasks and norepinephrine titration has been shown to be suboptimal. This can lead to limited BP control in patients that are in critical need of cerebral perfusion optimization. We have designed a closed-loop vasopressor (CLV) system capable of maintaining mean arterial pressure (MAP) in a narrow range and we aimed to assess its performance when treating severe brain injury patients. Within the first 48 h of intensive care unit (ICU) admission, 18 patients with a severe brain injury underwent either CLV or manual norepinephrine titration. In both groups, the objective was to maintain MAP in target (within ± 5 mmHg of a predefined target MAP) to achieve optimal CPP. Fluid administration was standardized in the two groups. The primary objective was the percentage of time patients were in target. Secondary outcomes included time spent over and under target. Over the four-hour study period, the mean percentage of time with MAP in target was greater in the CLV group than in the control group (95.8 ± 2.2% vs. 42.5 ± 27.0%, p < 0.001). Severe undershooting, defined as MAP < 10 mmHg of target value was lower in the CLV group (0.2 ± 0.3% vs. 7.4 ± 14.2%, p < 0.001) as was severe overshooting defined as MAP > 10 mmHg of target (0.0 ± 0.0% vs. 22.0 ± 29.0%, p < 0.001). The CLV system can maintain MAP in target better than nurses caring for severe brain injury patients.

Closed-loop anesthesia: foundations and applications in contemporary perioperative medicine.

A closed-loop automatically controls a variable using the principle of feedback. Automation within anesthesia typically aims to improve the stability of a controlled variable and reduce workload associated with simple repetitive tasks. This approach attempts to limit errors due to distractions or fatigue while simultaneously increasing compliance to evidence based perioperative protocols. The ultimate goal is to use these advantages over manual care to improve patient outcome. For more than twenty years, clinical studies in anesthesia have demonstrated the superiority of closed-loop systems compared to manual control for stabilizing a single variable, reducing practitioner workload, and safely administering therapies. This research has focused on various closed-loops that coupled inputs and outputs such as the processed electroencephalogram with propofol, blood pressure with vasopressors, and dynamic predictors of fluid responsiveness with fluid therapy. Recently, multiple simultaneous independent closed-loop systems have been tested in practice and one study has demonstrated a clinical benefit on postoperative cognitive dysfunction. Despite their advantages, these tools still require that a well-trained practitioner maintains situation awareness, understands how closed-loop systems react to each variable, and is ready to retake control if the closed-loop systems fail. In the future, multiple input multiple output closed-loop systems will control anesthetic, fluid and vasopressor titration and may perhaps integrate other key systems, such as the anesthesia machine. Human supervision will nonetheless always be indispensable as situation awareness, communication, and prediction of events remain irreplaceable human factors.

Perioperative Fluid and Vasopressor Therapy in 2050: From Experimental Medicine to Personalization Through Automation.

Intravenous (IV) fluids and vasopressor agents are key components of hemodynamic management. Since their introduction, their use in the perioperative setting has continued to evolve, and we are now on the brink of automated administration. IV fluid therapy was first described in Scotland during the 1832 cholera epidemic, when pioneers in medicine saved critically ill patients dying from hypovolemic shock. However, widespread use of IV fluids only began in the 20th century. Epinephrine was discovered and purified in the United States at the end of the 19th century, but its short half-life limited its implementation into patient care. Advances in venous access, including the introduction of the central venous catheter, and the ability to administer continuous infusions of fluids and vasopressors rather than just boluses, facilitated the use of fluids and adrenergic agents. With the advent of advanced hemodynamic monitoring, most notably the pulmonary artery catheter, the role of fluids and vasopressors in the maintenance of tissue oxygenation through adequate cardiac output and perfusion pressure became more clearly established, and hemodynamic goals could be established to better titrate fluid and vasopressor therapy. Less invasive hemodynamic monitoring techniques, using echography, pulse contour analysis, and heart-lung interactions, have facilitated hemodynamic monitoring at the bedside. Most recently, advances have been made in closed-loop fluid and vasopressor therapy, which apply computer assistance to interpret hemodynamic variables and therapy. Development and increased use of artificial intelligence will likely represent a major step toward fully automated hemodynamic management in the perioperative environment in the near future. In this narrative review, we discuss the key events in experimental medicine that have led to the current status of fluid and vasopressor therapies and describe the potential benefits that future automation has to offer.

Closing the loop: automation in anesthesiology is coming.

Anesthesiology and intensive care medicine provide fertile ground for innovation in automation, but to date we have only achieved preliminary studies in closed-loop intravenous drug administration. Anesthesiologists have yet to implement these tools on a large scale despite clear evidence that they outperform manual titration. Closed-loops continuously assess a predefined variable as input into a controller and then attempt to establish equilibrium by administering a treatment as output. The aim is to decrease the error between the closed-loop controller's input and output. In this editorial we consider the available intravenous anesthesia closed-loop systems, try to clarify why they have not yet been implemented on a large scale, see what they offer, and propose the future steps towards automation in anesthesia.

The Urethral Perfusion Index During Off-Pump Coronary Artery Bypass Surgery: An Observational Study.

OBJECTIVES: The IKORUS system (Vygon, Écouen, France) allows continuous monitoring of the urethral perfusion index (uPI) using a photoplethysmographic sensor mounted near the base of the balloon of a dedicated urinary catheter. We aimed to test the hypothesis that the uPI decreases during off-pump coronary artery bypass (OPCAB) surgery and to investigate the relationship between the uPI and macrocirculatory variables. DESIGN: Prospective observational study. SETTING: University Medical Center Hamburg-Eppendorf, Hamburg, Germany. PARTICIPANTS: Twenty patients having OPCAB surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The primary endpoint was changes in the uPI during OPCAB surgery. We additionally investigated associations between the uPI and cardiac output, mean arterial pressure, heart rate, and point-of-care variables. Twenty patients with 24,137 uPI measurements were included. Overall, there was a high interindividual variability in the uPI. Compared with the preparation phase (during which the median [interquartile range] uPI was 7.7 [5.6-12.0]), the uPI decreased by 14% (95% CI 13%-15%) during the bypass grafting phase, by 35% (95% CI 34%-36%) during the cardiac positioning phase, and by 7% (95% CI 6%-9%) during hemostasis. There was no clinically important association between uPI and either cardiac output, mean arterial pressure, or heart rate. CONCLUSIONS: The uPI decreases during OPCAB surgery, specifically during the cardiac positioning phase. There was no clinically important association between uPI and either cardiac output, mean arterial pressure, or heart rate. It, therefore, remains to be determined whether intraoperative uPI decreases are clinically important, reflect alterations in intra-abdominal tissue perfusion that are not reflected by systemic macrohemodynamics, and can help clinicians guide therapeutic interventions.

Tight control of mean arterial pressure using a closed loop system for norepinephrine infusion after high-risk abdominal surgery: a randomized controlled trial.

Intensive care unit (ICU) nurses frequently manually titrate norepinephrine to maintain a predefined mean arterial pressure (MAP) target after high-risk surgery. However, achieving this task is often suboptimal. We have developed a closed-loop vasopressor (CLV) controller to better maintain MAP within a narrow range. After ethical committee approval, fifty-three patients admitted to the ICU following high-risk abdominal surgery were randomized to CLV or manual norepinephrine titration. In both groups, the aim was to maintain MAP in the predefined target of 80-90 mmHg. Fluid administration was standardized in the two groups using an advanced hemodynamic monitoring device. The primary outcome of our study was the percentage of time patients were in the MAP target. Over the 2-hour study period, the percentage of time with MAP in target was greater in the CLV group than in the control group (median: IQR25-75: 80 [68-88]% vs. 42 [22-65]%), difference 37.2, 95% CI (23.0-49.2); p < 0.001). Percentage time with MAP under 80 mmHg (1 [0-5]% vs. 26 [16-75]%, p < 0.001) and MAP under 65 mmHg (0 [0-0]% vs. 0 [0-4]%, p = 0.017) were both lower in the CLV group than in the control group. The percentage of time with a MAP > 90 mmHg was not statistically different between groups. In patients admitted to the ICU after high-risk abdominal surgery, closed-loop control of norepinephrine infusion better maintained a MAP target of 80 to 90 mmHg and significantly decreased postoperative hypotensive when compared to manual norepinephrine titration.

Intraoperative blood pressure: could less be more?

Retrospective observational studies have reported a significant association between intraoperative hypotension and postoperative morbidity. However, association does not imply causation, and whether preventing intraoperative hypotension can improve patient outcome remains to be demonstrated. In this issue of the British Journal of Anaesthesia, D'Amico and colleagues meta-analysed 10 prospective randomised trials comparing low (≤60 mm Hg) and higher mean arterial pressure targets during anaesthesia and surgery. They did not observe an increase in postoperative morbidity and mortality in the low target group. In contrast, they reported a statistically significant (but not clinically relevant) reduction in postoperative cardiac arrhythmia and hospital length of stay when targeting mean arterial pressure ≤60 mm Hg. These findings suggest that during most surgical cases, intraoperative hypotension is a marker of the severity, frailty, or both rather than a mediator of postoperative complications.

Physiological Modeling of Hemodynamic Responses to Sodium Nitroprusside.

BACKGROUND: Computational modeling of physiology has become a routine element in the development, evaluation, and safety testing of many types of medical devices. Members of the Food and Drug Administration have recently published a manuscript detailing the development, validation, and sensitivity testing of a computational model for blood volume, cardiac stroke volume, and blood pressure, noting that such a model might be useful in the development of closed-loop fluid administration systems. In the present study, we have expanded on this model to include the pharmacologic effect of sodium nitroprusside and calibrated the model against our previous experimental animal model data. METHODS: Beginning with the model elements in the original publication, we added six new parameters to control the effect of sodium nitroprusside: two for the onset time and clearance rates, two for the stroke volume effect (which includes venodilation as a "hidden" element), and two for the direct effect on arterial blood pressure. Using this new model, we then calibrated the predictive performance against previously collected animal study data using nitroprusside infusions to simulate shock with the primary emphasis on MAP. Root-mean-squared error (RMSE) was calculated, and the performance was compared to the performance of the model in the original study. RESULTS: RMSE of model-predicted MAP to actual MAP was lower than that reported in the original model, but higher for SV and CO. The individually fit models showed lower RMSE than using the population average values for parameters, suggesting the fitting process was effective in identifying improved parameters. Use of partially fit models after removal of the lowest variance population parameters showed a very minor decrement in improvement over the fully fit models. CONCLUSION: The new model added the clinical effects of SNP and was successfully calibrated against experimental data with an RMSE of <10% for mean arterial pressure. Model-predicted MAP showed an error similar to that seen in the original base model when using fluid shifts, heart rate, and drug dose as model inputs.

Diagnostic accuracy of the peripheral venous pressure variation induced by an alveolar recruitment maneuver to predict fluid responsiveness during high-risk abdominal surgery.

BACKGROUND: In patients undergoing high-risk surgery, it is recommended to titrate fluid administration using stroke volume or a dynamic variable of fluid responsiveness (FR). However, this strategy usually requires the use of a hemodynamic monitor and/or an arterial catheter. Recently, it has been shown that variations of central venous pressure (ΔCVP) during an alveolar recruitment maneuver (ARM) can predict FR and that there is a correlation between CVP and peripheral venous pressure (PVP). This prospective study tested the hypothesis that variations of PVP (ΔPVP) induced by an ARM could predict FR. METHODS: We studied 60 consecutive patients scheduled for high-risk abdominal surgery, excluding those with preoperative cardiac arrhythmias or right ventricular dysfunction. All patients had a peripheral venous catheter, a central venous catheter and a radial arterial catheter linked to a pulse contour monitoring device. PVP was always measured via an 18-gauge catheter inserted at the antecubital fossa. Then an ARM consisting of a standardized gas insufflation to reach a plateau of 30 cmH2O for 30 s was performed before skin incision. Invasive mean arterial pressure (MAP), pulse pressure, heart rate, CVP, PVP, pulse pressure variation (PPV), and stroke volume index (SVI) were recorded before ARM (T1), at the end of ARM (T2), before volume expansion (T3), and one minute after volume expansion (T4). Receiver-operating curves (ROC) analysis with the corresponding grey zone approach were performed to assess the ability of ∆PVP (index test) to predict FR, defined as an ≥ 10% increase in SVI following the administration of a 4 ml/kg balanced crystalloid solution over 5 min. RESULTS: ∆PVP during ARM predicted FR with an area under the ROC curve of 0.76 (95%CI, 0.63 to 0.86). The optimal threshold determined by the Youden Index was a ∆PVP value of 5 mmHg (95%CI, 4 to 6) with a sensitivity of 66% (95%CI, 47 to 81) and a specificity of 82% (95%CI, 63 to 94). The AUC's for predicting FR were not different between ΔPVP, ΔCVP, and PPV. CONCLUSION: During high-risk abdominal surgery, ∆PVP induced by an ARM can moderately predict FR. Nevertheless, other hemodynamic variables did not perform better.

Guidelines on perioperative optimization protocol for the adult patient 2023.

OBJECTIVE: The French Society of Anesthesiology and Intensive Care Medicine [Société Française d'Anesthésie et de Réanimation (SFAR)] aimed at providing guidelines for the implementation of perioperative optimization programs. DESIGN: A consensus committee of 29 experts from the SFAR was convened. A formal conflict-of-interest policy was developed at the outset of the process and enforced throughout. The entire guidelines process was conducted independently of any industry funding. The authors were advised to follow the principles of the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system to guide assessment of quality of evidence. METHODS: Four fields were defined: 1) Generalities on perioperative optimization programs; 2) Preoperative measures; 3) Intraoperative measures and; 4) Postoperative measures. For each field, the objective of the recommendations was to answer a number of questions formulated according to the PICO model (population, intervention, comparison, and outcomes). Based on these questions, an extensive bibliographic search was carried out using predefined keywords according to PRISMA guidelines and analyzed using the GRADE® methodology. The recommendations were formulated according to the GRADE® methodology and then voted on by all the experts according to the GRADE grid method. As the GRADE® methodology could have been fully applied for the vast majority of questions, the recommendations were formulated using a "formalized expert recommendations" format. RESULTS: The experts' work on synthesis and application of the GRADE® method resulted in 30 recommendations. Among the formalized recommendations, 19 were found to have a high level of evidence (GRADE 1±) and ten a low level of evidence (GRADE 2±). For one recommendation, the GRADE methodology could not be fully applied, resulting in an expert opinion. Two questions did not find any response in the literature. After two rounds of rating and several amendments, strong agreement was reached for all the recommendations. CONCLUSIONS: Strong agreement among the experts was obtained to provide 30 recommendations for the elaboration and/or implementation of perioperative optimization programs in the highest number of surgical fields.

Perioperative clinical practice in liver transplantation: a cross-sectional survey.

PURPOSE: The objective of this study was to describe some components of the perioperative practice in liver transplantation as reported by clinicians. METHODS: We conducted a cross-sectional clinical practice survey using an online instrument containing questions on selected themes related to the perioperative care of liver transplant recipients. We sent email invitations to Canadian anesthesiologists, Canadian surgeons, and French anesthesiologists specialized in liver transplantation. We used five-point Likert-type scales (from "never" to "always") and numerical or categorical answers. Results are presented as medians or proportions. RESULTS: We obtained answers from 130 participants (estimated response rate of 71% in Canada and 26% in France). Respondents reported rarely using transesophageal echocardiography routinely but often using it for hemodynamic instability, often using an intraoperative goal-directed hemodynamic management strategy, and never using a phlebotomy (medians from ordinal scales). Fifty-nine percent of respondents reported using a restrictive fluid management strategy to manage hemodynamic instability during the dissection phase. Forty-two percent and 15% of respondents reported using viscoelastic tests to guide intraoperative and postoperative transfusions, respectively. Fifty-four percent of respondents reported not pre-emptively treating preoperative coagulations disturbances, and 91% reported treating them intraoperatively only when bleeding was significant. Most respondents (48-64%) did not have an opinion on the maximal graft ischemic times. Forty-seven percent of respondents reported that a piggyback technique was the preferred vena cava anastomosis approach. CONCLUSION: Different interventions were reported to be used regarding most components of perioperative care in liver transplantation. Our results suggest that significant equipoise exists on the optimal perioperative management of this population.

RéSUMé: OBJECTIF: L'objectif de cette étude était de décrire certaines composantes de la pratique périopératoire en transplantation hépatique telles que rapportées par les cliniciens. MéTHODE: Nous avons mené un sondage transversal sur la pratique clinique à l'aide d'un instrument en ligne comportant des questions sur des thèmes sélectionnés liés aux soins périopératoires des receveurs de greffe du foie. Nous avons envoyé des invitations par courriel à des anesthésiologistes canadiens, des chirurgiens canadiens et des anesthésiologistes français spécialisés en transplantation hépatique. Nous avons utilisé des échelles de type Likert à cinq points (de « jamais ¼ à « toujours ¼) et des réponses numériques ou catégorielles. Les résultats sont présentés sous forme de médianes ou de proportions. RéSULTATS: Nous avons obtenu des réponses de 130 participants (taux de réponse estimé à 71 % au Canada et à 26 % en France). Les répondants ont déclaré utiliser rarement l'échocardiographie transœsophagienne de routine, mais l'utiliser fréquemment pour l'instabilité hémodynamique, souvent en utilisant une stratégie de prise en charge hémodynamique peropératoire axée sur les objectifs, et jamais en utilisant une phlébotomie (médianes des échelles ordinales). Cinquante-neuf pour cent des répondants ont déclaré utiliser une stratégie restrictive de gestion liquidienne pour prendre en charge l'instabilité hémodynamique pendant la phase de dissection. Quarante-deux pour cent et 15 % des répondants ont déclaré utiliser des tests viscoélastiques pour guider les transfusions peropératoires et postopératoires, respectivement. Cinquante-quatre pour cent des répondants ont déclaré ne pas traiter préventivement les troubles préopératoires de la coagulation, et 91 % ont déclaré les traiter en peropératoire uniquement lorsque les saignements étaient importants. La plupart des répondants (48-64 %) n'avaient pas d'opinion sur les temps ischémiques maximaux du greffon. Quarante-sept pour cent des répondants ont déclaré qu'une technique de 'piggyback' (anastomose latéroterminale) était l'approche préférée pour l'anastomose de la veine cave. CONCLUSION: Différentes interventions ont été signalées pour la plupart des composantes des soins périopératoires dans la transplantation hépatique. Nos résultats suggèrent qu'il existe une incertitude significative concernant la prise en charge périopératoire optimale de cette population.

Arterial Lactate Concentration at the End of Liver Transplantation is Independently Associated With One-Year Mortality.

BACKGROUND: Liver transplant patients who develop hyperlactatemia are at increased risk of postoperative morbidity and short-term mortality, but there are few data on longer-term outcomes. We therefore investigated if arterial lactate concentration obtained immediately after surgery, at the time of admission to the intensive care unit (ICU), was associated with 1-year mortality. METHODS: In this retrospective cohort study, all patients who underwent liver transplant surgery from a deceased donor between September 2013 and December 2019 were screened for inclusion. Patients who underwent combined transplantation surgery and those with a history of previous liver transplantation (ie, redo surgery) were not included. Logistic regression modeling included univariate and multivariate analyses. Receiver operating characteristic curves and areas under the curves were calculated. Lactate thresholds and association with outcome were analyzed for specificity, sensitivity, and Youden's index. RESULTS: Of 226 patients included, 18.4% died within 1 year of liver transplantation. Immediate postoperative lactate concentration was independently associated with 1-year mortality with an adjusted odds ratio of 1.35 (95% CI 1.16-1.59; P < .001) per mmol/L increase in lactate and an area under the curve of 0.80 (95% CI 0.72-0.87; P < .001). A lactate concentration of 2.25 mmol/L (cutoff determined using Youden's index) was associated with increased 1-year mortality with a sensitivity of 0.71 and a specificity of 0.72. CONCLUSIONS: Increased arterial lactate concentration on admission to the intensive care unit immediately after orthotopic liver transplantation is independently associated with increased 1-year mortality.

Non-invasive measurement of digital plethysmographic variability index to predict fluid responsiveness in mechanically ventilated children: A systematic review and meta-analysis of diagnostic test accuracy studies.

BACKGROUND: To date, the use of the plethysmographic variability index (PVI) has not been recommended to guide fluid management in the paediatric surgical population. This systematic review and meta-analysis aimed to summarise available evidence about the diagnostic accuracy of digital PVI to predict fluid responsiveness in mechanically ventilated children. METHODS: We searched the Pubmed, Embase and Web of Science databases, from inception to January 2022, to identify all relevant studies that investigated the ability of the PVI recorded at the finger to predict fluid responsiveness in mechanically ventilated children. Using a random-effects model, we calculated pooled values of diagnostic odds ratio, sensitivity, and specificity of PVI to predict the response to fluid challenge. RESULTS: Eight studies met the inclusion criteria with a total of 283 patients and 360 fluid challenges. All the studies were carried out in a surgical setting. The area under the summary receiver operating characteristic curve of PVI to predict fluid responsiveness was 0.82. The pooled sensitivity, specificity, and diagnostic odds ratio of PVI for the overall population were 72.4% [95% CI: 65.3-78.7], 65.9% [58.5-72.8], and 9.26 [5.31-16.16], respectively. CONCLUSION: Our results suggest that digital PVI is a reliable predictor for fluid responsiveness in mechanically ventilated children in the perioperative setting. The diagnostic performance of digital PVI reported in our work for discrimination between responders and non-responders to the fluid challenge was however not as high as previously reported in the adult population.

Sensitivity Analysis of a Mathematical Model Simulating the Post-Hepatectomy Hemodynamics Response.

Recently a lumped-parameter model of the cardiovascular system was proposed to simulate the hemodynamics response to partial hepatectomy and evaluate the risk of portal hypertension (PHT) due to this surgery. Model parameters are tuned based on each patient data. This work focuses on a global sensitivity analysis (SA) study of such model to better understand the main drivers of the clinical outputs of interest. The analysis suggests which parameters should be considered patient-specific and which can be assumed constant without losing in accuracy in the predictions. While performing the SA, model outputs need to be constrained to physiological ranges. An innovative approach exploits the features of the polynomial chaos expansion method to reduce the overall computational cost. The computed results give new insights on how to improve the calibration of some model parameters. Moreover the final parameter distributions enable the creation of a virtual population available for future works. Although this work is focused on partial hepatectomy, the pipeline can be applied to other cardiovascular hemodynamics models to gain insights for patient-specific parameterization and to define a physiologically relevant virtual population.

Preoperative Fibrinogen Level and Bleeding in Liver Transplantation for End-stage Liver Disease: A Cohort Study.

BACKGROUND: Liver transplantation is a high-risk surgery associated with important perioperative bleeding and transfusion needs. Uncertainties remain on the association between preoperative fibrinogen level and bleeding in this population. METHODS: We conducted a cohort study that included all consecutive adult patients undergoing a liver transplantation for end-stage liver disease in 1 center. We analyzed the association between the preoperative fibrinogen level and bleeding-related outcomes. Our primary outcome was intraoperative blood loss, and our secondary outcomes were estimated perioperative blood loss, intraoperative and perioperative red blood cell transfusions, reinterventions for bleeding and 1-y graft and patient survival. We estimated linear regression models and marginal risk models adjusted for all important potential confounders. We used restricted cubic splines to explore potential nonlinear associations and reported dose-response curves. RESULTS: We included 613 patients. We observed that a lower fibrinogen level was associated with a higher intraoperative blood loss, a higher estimated perioperative blood loss and a higher risk of intraoperative and perioperative red blood cell transfusions (nonlinear effects). Based on an exploratory analysis of the dose-response curves, these effects were observed below a threshold value of 3 g/L for these outcomes. We did not observe any association between preoperative fibrinogen level and reinterventions, 1-y graft survival or 1-y patient survival. CONCLUSIONS: This study suggests that a lower fibrinogen level is associated with bleeding in liver transplantation. The present results may help improving the selection of patients for further studies on preoperative fibrinogen administration in liver transplant recipients with end-stage liver disease.

Smartphone-Based versus Non-Invasive Automatic Oscillometric Brachial Cuff Blood Pressure Measurements: A Prospective Method Comparison Volunteer Study.

Introduction: Mobile health diagnostics have demonstrated effectiveness in detecting and managing chronic diseases. This method comparison study aims to assess the accuracy and precision of the previously evaluated OptiBP™ technology over a four-week study period. This device uses optical signals recorded by placing a patient's fingertip on a smartphone's camera to estimate blood pressure (BP). Methods: In adult participants without cardiac arrhythmias and minimal interarm blood pressure difference (systolic arterial pressure (SAP) < 15 mmHg or diastolic arterial pressure (DAP) < 10 mmHg), three pairs of 30 s BP measurements with the OptiBP™ (test method) were simultaneously compared using three pairs of measurements with the non-invasive oscillometric brachial cuff (reference method) on the opposite arm over a period of four consecutive weeks at a rate of two measurements per week (one in the morning and one in the afternoon). The agreement of BP values between the two technologies was analyzed using Bland-Altman and error grid analyses. The performance of the smartphone application was investigated using the International Organization for Standardization (ISO) definitions, which require the bias ± standard deviation (SD) between two technologies to be lower than 5 ± 8 mmHg. Results: Among the 65 eligible volunteers, 53 participants had adequate OptiBP™ BP values. In 12 patients, no OptiBP™ BP could be measured due to inadequate signals. Only nine participants had known chronic arterial hypertension and 76% of those patients were treated. The mean bias ± SD between both technologies was -1.4 mmHg ± 10.1 mmHg for systolic arterial pressure (SAP), 0.2 mmHg ± 6.5 mmHg for diastolic arterial pressure (DAP) and -0.5 mmHg ± 6.9 mmHg for mean arterial pressure (MAP). Error grid analyses indicated that 100% of the pairs of BP measurements were located in zones A (no risk) and B (low risk). Conclusions: In a cohort of volunteers, we observed an acceptable agreement between BP values obtained with the OptiBPTM and those obtained with the reference method over a four-week period. The OptiBPTM fulfills the ISO standards for MAP and DAP (but not SAP). The error grid analyses showed that 100% measurements were located in risk zones A and B. Despite the need for some technological improvements, this application may become an important tool to measure BP in the future.

Intraoperative measurement of the respiratory exchange ratio predicts postoperative complications after liver transplantation.

BACKGROUND: During surgery, any mismatch between oxygen delivery (DO2) and consumption (VO2) can promote the development of postoperative complications. The respiratory exchange ratio (RER), defined as the ratio of carbon dioxide (CO2) production (VCO2) to VO2, may be a useful noninvasive tool for detecting inadequate DO2. The primary objective of this study was to test the hypothesis that RER measured during liver transplantation may predict postoperative morbidity. Secondary objectives were to assess the ability of other variables used to assess the DO2/VO2 relationship, including arterial lactate, mixed venous oxygen saturation, and veno-arterial difference in the partial pressure of carbon dioxide (VAPCO2gap), to predict postoperative complications. METHODS: This retrospective study included consecutive adult patients who underwent liver transplantation for end stage liver disease from June 27th, 2020, to September 5th, 2021. Patients with acute liver failure were excluded. All patients were routinely equipped with a pulmonary artery catheter. The primary analysis was a receiver operating characteristic (ROC) curve constructed to investigate the discriminative ability of the mean RER measured during surgery to predict postoperative complications. RER was calculated at five standardized time points during the surgery, at the same time as measurement of blood lactate levels and arterial and mixed venous blood gases, which were compared as a secondary analysis. RESULTS: Of the 115 patients included, 57 developed at least one postoperative complication. The mean RER (median [25-75] percentiles) during surgery was significantly higher in patients with complications than in those without (1.04[0.96-1.12] vs 0.88[0.84-0.94]; p < 0.001). The area under the ROC curve was 0.87 (95%CI: 0.80-0.93; p < 0.001) with a RER value (Youden index) of 0.92 giving a sensitivity of 91% and a specificity of 74% for predicting the occurrence of postoperative complications. The RER outperformed all other measured variables assessing the DO2/VO2 relationship (arterial lactate, SvO2, and VAPCO2gap) in predicting postoperative complications. CONCLUSION: During liver transplantation, the RER can reliably predict postoperative complications. Implementing this measure intraoperatively may provide a warning for physicians of impending complications and justify more aggressive optimization of oxygen delivery. Further studies are required to determine whether correcting the RER is feasible and could reduce the incidence of complications.

Systolic Arterial Pressure Control Using an Automated Closed-Loop System for Vasopressor Infusion during Intermediate-to-High-Risk Surgery: A Feasibility Study.

Introduction: Vasopressor infusions are essential in treating and preventing intraoperative hypotension. Closed-loop vasopressor therapy outperforms clinicians when the target is set at a mean arterial pressure (MAP) baseline, but little is known on the performance metrics of closed-loop vasopressor infusions when systolic arterial pressure (SAP) is the controlled variable. Methods: Patients undergoing intermediate- to high-risk abdominal surgery were included in this prospective cohort feasibility study. All patients received norepinephrine infusion through a computer controlled closed-loop system that targeted SAP at 130 mmHg. The primary objective was to determine the percent of case time in hypotension or under target defined as SAP below 10% of the target (SAP < 117 mmHg). Secondary objectives were the percent of case time "above target" (SAP > 10% of the target or >143 mmHg) and "in target" (within 10% of the SAP target or SAP between 117 and 143 mmHg). Results: A total of 12 patients were included. The closed-loop system infused norepinephrine for a median of 94.6% (25−75th percentile: 90.0−98.0%) of case time. The percentage of case time in hypotension or under target was only 1.8% (0.9−3.6%). The percentages of case time "above target" and "in target" were 4.7% (3.2−7.5%) and 92.4% (90.1−96.3%), respectively. Conclusions: This closed-loop vasopressor system minimizes intraoperative hypotension and maintains SAP within 10% of the target range for >90% of the case time in patients undergoing intermediate- to high-risk abdominal surgery.