Comparison of differences in cohort (forwards) and case control (backwards) methodological approaches for validation of the Hypotension Prediction Index.

BACKGROUND: The Hypotension Prediction Index (the index) software is a machine learning algorithm that detects physiological changes that may lead to hypotension. The original validation used a case control (backwards) analysis that has been suggested to be biased. We therefore conducted a cohort (forwards) analysis and compared this to the original validation technique. METHODS: We conducted a retrospective analysis of data from previously reported studies. All data were analysed identically with 2 different methodologies and receiver operating characteristic curves (ROC) constructed. Both backwards and forwards analyses were performed to examine differences in area under the ROC for HPI and other haemodynamic variables to predict a MAP < 65mmHg for at least 1 minute 5, 10 and 15 minutes in advance. RESULTS: Two thousand and twenty-two patients were included in the analysis, yielding 4,152,124 measurements taken at 20 second intervals. The area-under-the-curve for the index predicting hypotension analysed by backward and forward methodologies respectively was 0.957 (95% CI, 0.947-0.964) vs 0.923 (95% CI, 0.912-0.933) 5 minutes in advance, 0.933 (95% CI, 0.924-0.942) vs 0.923 (95% CI, 0.911-0.933) 10 minutes in advance , and 0.929 (95% CI, 0.918-0.938) vs. 0.926 (95% CI, 0.914-0.937) 15 minutes in advance. No other variable had an area-under-the-curve > 0.7 except for MAP. Area-under-the-curve using forward analysis for MAP predicting hypotension 5, 10, and 15 minutes in advance was 0.932 (95% CI, 0.920-0.940), 0.929 (95% CI, 0.918-0.938), and 0.932 (95% CI, 0.921-0.940). The R 2 for the variation in the index due to MAP was 0.77. CONCLUSION: Using an updated methodology, we found the utility of the HPI index to predict future hypotensive events is high, with an area under the receiver-operating-characteristics curve similar to that of the original validation method.

The effect of liver surgery and fluid strategy on renin activity and aldosterone and anti-diuretic hormone levels: a secondary analysis of the GALILEO trial.

BACKGROUND: It is unknown whether liver surgery leads to increased RAAS activity and anti-diuretic hormone (ADH) levels and subsequent fluid accumulation. Furthermore, it is unknown whether the peri-operative fluid strategy changes this effect. METHODS: This is a pre-planned post hoc analysis of a randomised controlled trial which compared restrictive (n = 20) versus liberal fluid strategy (n = 20) in patients undergoing liver surgery. Primary outcomes for the current study were the difference in hormone levels after anaesthesia induction and after liver resection. Fluid overload was defined as a ≥10% increase in weight. RESULTS: Renin activity (6 [2.1-15.5] vs. 12 [4.6-33.5]) and ADH levels (6.0 [1.7-16.3] vs. 3.8 [1.6-14.7]) did not differ significantly before and after resection. However, aldosterone levels were significantly higher after resection (0.30 [0.17-0.49] vs. 0.69 [0.31-1.21] ). Renin activity and aldosterone levels did not differ between the groups. ADH was significantly higher in the restrictive strategy group (1.6 [1.1-2.1] vs 5.9 [3.8-16.0]). No differences in hormone levels were found in patients with and without fluid overload. DISCUSSION: Aldosterone levels increased after liver surgery but renin activity and ADH levels did not. ADH levels were higher in the restrictive group. Development of post-operative fluid overload was not associated with RAAS activity or ADH levels.

Can volume-reduced plasma products prevent transfusion-associated circulatory overload in a two-hit animal model?

BACKGROUND AND OBJECTIVES: Transfusion-associated circulatory overload (TACO) is a pulmonary transfusion complication and a leading cause of transfusion-related morbidity and mortality. Volume overload and rising hydrostatic pressure as a consequence of transfusion are seen as the central pathway leading to TACO. A possible preventative measure for TACO could be the use of low-volume blood products like volume-reduced lyophilized plasma. We hypothesize that volume-reduced lyophilized plasma decreases circulatory overload leading to a reduced pulmonary capillary pressure and can therefore be an effective strategy to prevent TACO. MATERIALS AND METHODS: A validated two-hit animal model in rats with heart failure was used. Animals were randomized to receive 4 units of either solvent-detergent pooled plasma (SDP) as control, standard volume lyophilized plasma (LP-S) or hyperoncotic volume-reduced lyophilized plasma (LP-VR). The primary outcome was the difference between pre-transfusion and post-transfusion left ventricular end-diastolic pressure (ΔLVEDP). Secondary outcomes included markers for acute lung injury. RESULTS: LVEDP increased in all randomization groups following transfusion. The greatest elevation was seen in the group receiving LP-VR (+11.9 mmHg [5.9-15.6]), but there were no significant differences when compared to groups receiving either LP-S (+6.3 mmHg [2.9-13.4], p = 0.29) or SDP (+7.7 mmHg [4.5-10.5], p = 0.55). There were no significant differences in markers for acute lung injury, such as pulmonary wet/dry weight ratios, lung histopathology scores or PaO2 /FiO2 ratio between the three groups. CONCLUSION: Transfusion with hyperoncotic volume-reduced plasma did not attenuate circulatory overload compared to standard volume plasma and was therefore not an effective preventative strategy for TACO in this rat model.

Dynamic cerebral autoregulation during step-wise increases in blood pressure during anaesthesia: A nonrandomised interventional trial.

BACKGROUND: Classically, cerebral autoregulation (CA) entails cerebral blood flow (CBF) remaining constant by cerebrovascular tone adapting to fluctuations in mean arterial pressure (MAP) between ∼60 and ∼150 mmHg. However, this is not an on-off mechanism; previous work has suggested that vasomotor tone is proportionally related to CA function. During propofol-based anaesthesia, there is cerebrovascular vasoconstriction, and static CA remains intact. Sevoflurane-based anaesthesia induces cerebral vasodilation and attenuates CA dose-dependently. It is unclear how this translates to dynamic CA across a range of blood pressures in the autoregulatory range. OBJECTIVE: The aim of this study was to quantify the effect of step-wise increases in MAP between 60 and 100 mmHg, using phenylephrine, on dynamic CA during propofol- and sevoflurane-based anaesthesia. DESIGN: A nonrandomised interventional trial. SETTING: Single centre enrolment started on 11 January 2019 and ended on 23 September 2019. PATIENTS: We studied American Society of Anesthesiologists (ASA) I/II patients undergoing noncardiothoracic, nonneurosurgical and nonlaparoscopic surgery under general anaesthesia. INTERVENTION: In this study, cerebrovascular tone was manipulated in the autoregulatory range by increasing MAP step-wise using phenylephrine in patients receiving either propofol- or sevoflurane-based anaesthesia. MAP and mean middle cerebral artery blood velocity (MCA Vmean ) were measured in ASA I and II patients, anaesthetised with either propofol ( n  = 26) or sevoflurane ( n  = 28), during 10 mmHg step-wise increments of MAP between 60 and 100 mmHg. Static CA was determined by plotting 2-min averaged MCA Vmean versus MAP. Dynamic CA was determined using transfer function analysis and expressed as the phase lead (°) between MAP and MCA Vmean oscillations, created with positive pressure ventilation with a frequency of 6 min -1 . MAIN OUTCOMES: The primary outcome of this study was the response of dynamic CA during step-wise increases in MAP during propofol- and sevoflurane-based anaesthesia. RESULTS: MAP levels achieved per step-wise increments were comparable between anaesthesia regiment (63 ±â€Š3, 72 ±â€Š2, 80 ±â€Š2, 90 ±â€Š2, 100 ±â€Š3 mmHg, and 61 ±â€Š4, 71 ±â€Š2, 80 ±â€Š2, 89 ±â€Š2, 98 ±â€Š4 mmHg for propofol and sevoflurane, respectively). MCA Vmean increased more during step-wise MAP increments for sevoflurane compared to propofol ( P ≤0.001). Dynamic CA improved during propofol (0.73° mmHg -1 , 95% CI 0.51 to 0.95; P  ≤ 0.001)) and less pronounced during sevoflurane-based anaesthesia (0.21°â€ŠmmHg -1 (95% CI 0.01 to 0.42, P  = 0.04). CONCLUSIONS: During general anaesthesia, dynamic CA is dependent on MAP, also within the autoregulatory range. This phenomenon was more pronounced during propofol anaesthesia than during sevoflurane. TRIAL REGISTRATION: NCT03816072 ( https://clinicaltrials.gov/ct2/show/NCT03816072 ).

Autologous red blood cell transfusion does not result in a more profound increase in pulmonary capillary wedge pressure compared to saline in critically ill patients: A randomized crossover trial.

BACKGROUND AND OBJECTIVES: Transfusion-associated circulatory overload (TACO) is a major cause of severe transfusion-related morbidity. Transfusion of red blood cells (RBCs) has been shown to induce hydrostatic pressure overload. It is unclear which product-specific factors contribute. We set out to determine the effect of autologous RBC transfusion versus saline on pulmonary capillary wedge pressure (PCWP) change. MATERIALS AND METHODS: In a randomized crossover trial, patients who had undergone coronary bypass surgery were allocated to treatment post-operatively in the intensive care unit with either an initial 300 ml autologous RBC transfusion (salvaged during surgery) or 300 ml saline infusion first, followed by the other. Primary outcome was the difference in PCWP change. Secondary outcome measures were the difference in extra-vascular lung water index (EVLWI) and pulmonary vascular permeability index (PVPI). RESULTS: Change in PCWP was not higher after autologous RBC transfusion compared to saline (ΔPCWP 0.3 ± 0.4 vs. 0.1 ± 0.4 mmHg). ΔEVLWI and ΔPVPI were significantly decreased after autologous RBC transfusion compared to saline (ΔEVLWI -1.6 ± 0.6 vs. 0.2 ± 0.4, p = 0.02; ΔPVPI -0.3 ± 0.1 vs. 0.0 ± 0.1, p = 0.01). Haemodynamic variables and colloid osmotic pressure were not different for autologous RBC transfusion versus saline. CONCLUSION: Transfusion of autologous RBCs did not result in a more profound increase in PCWP compared to saline. RBC transfusion resulted in a decrease of EVLWI and PVPI compared to saline. Our data suggest that transfusing autologous RBCs may lead to less pulmonary oedema compared to saline. Future studies with allogeneic RBCs are needed to investigate other factors that may mediate the increase of PCWP, resulting in TACO.

Differential effects of speed and volume on transfusion-associated circulatory overload: A randomized study in rats.

BACKGROUND AND OBJECTIVES: Transfusion-associated circulatory overload (TACO) is the primary cause of transfusion-related mortality. Speed and volume of transfusion are major risk factors. The aim of this study was to investigate the interaction of red blood cell (RBC) transfusion speed and volume on the development of TACO. MATERIALS AND METHODS: A validated model for TACO in anaemic Lewis rats with an acute myocardial infarction was used. The effect on pulmonary hydrostatic pressure of one, two or four units of packed RBCs transfused in either 30 or 60 min was evaluated (3.3-26.6 ml·kg-1 ·hr-1 ). Pulmonary capillary pressure was measured as left ventricular end-diastolic pressure (LVEDP). Cardiac stress biomarkers atrial natriuretic-peptide (ANP) and N-terminal pro-brain natriuretic peptide (NT-proBNP) were measured 1-h post-transfusion. RESULTS: Thirty animals were included (n = 5 per group). Transfusion of RBCs increased LVEDP in a volume-dependent manner (ΔLVEDP [mmHg]: -0.95, +0.50, +6.26, p < 0.001). Fast transfusion increased overall ΔLVEDP by +3.5 mmHg and up to +11.8 mmHg in the four units' group (p = 0.016). Doubling transfusion speed increased ΔLVEDP more than doubling volume in the larger volume groups. No difference in ANP or NT-proBNP were seen in high transfusion volume or groups. CONCLUSION: Transfusion volume dose-dependently increased LVEDP, with speed of transfusion rapidly elevating LVEDP at higher transfusion volumes. ANP and NT-proBNP were not impacted by transfusion volume or speed in this model. TACO is seen as purely volume overload, however, this study emphasizes that limiting transfusion speed, as a modifiable risk factor, might aid in preventing TACO.

Performance of a machine-learning algorithm to predict hypotension in mechanically ventilated patients with COVID-19 admitted to the intensive care unit: a cohort study.

The Hypotension Prediction Index (HPI) is a commercially available machine-learning algorithm that provides warnings for impending hypotension, based on real-time arterial waveform analysis. The HPI was developed with arterial waveform data of surgical and intensive care unit (ICU) patients, but has never been externally validated in the latter group. In this study, we evaluated diagnostic ability of the HPI with invasively collected arterial blood pressure data in 41 patients with COVID-19 admitted to the ICU for mechanical ventilation. Predictive ability was evaluated at HPI thresholds from 0 to 100, at incremental intervals of 5. After exceeding the studied threshold, the next 20 min were screened for positive (mean arterial pressure (MAP) < 65 mmHg for at least 1 min) or negative (absence of MAP < 65 mmHg for at least 1 min) events. Subsequently, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and time to event were determined for every threshold. Almost all patients (93%) experienced at least one hypotensive event. Median number of events was 21 [7-54] and time spent in hypotension was 114 min [20-303]. The optimal threshold was 90, with a sensitivity of 0.91 (95% confidence interval 0.81-0.98), specificity of 0.87 (0.81-0.92), PPV of 0.69 (0.61-0.77), NPV of 0.99 (0.97-1.00), and median time to event of 3.93 min (3.72-4.15). Discrimination ability of the HPI was excellent, with an area under the curve of 0.95 (0.93-0.97). This validation study shows that the HPI correctly predicts hypotension in mechanically ventilated COVID-19 patients in the ICU, and provides a basis for future studies to assess whether hypotension can be reduced in ICU patients using this algorithm.

Effect of Hypotension Prediction Index-guided intraoperative haemodynamic care on depth and duration of postoperative hypotension: a sub-study of the Hypotension Prediction trial.

BACKGROUND: Intraoperative and postoperative hypotension are associated with morbidity and mortality. The Hypotension Prediction (HYPE) trial showed that the Hypotension Prediction Index (HPI) reduced the depth and duration of intraoperative hypotension (IOH), without excess use of intravenous fluid, vasopressor, and/or inotropic therapies. We hypothesised that intraoperative HPI-guided haemodynamic care would reduce the severity of postoperative hypotension in the PACU. METHODS: This was a sub-study of the HYPE study, in which 60 adults undergoing elective noncardiac surgery were allocated randomly to intraoperative HPI-guided or standard haemodynamic care. Blood pressure was measured using a radial intra-arterial catheter, which was connected to a FloTracIQ sensor. Hypotension was defined as MAP <65 mm Hg, and a hypotensive event was defined as MAP <65 mm Hg for at least 1 min. The primary outcome was the time-weighted average (TWA) of postoperative hypotension. Secondary outcomes were absolute incidence, area under threshold for hypotension, and percentage of time spent with MAP <65 mm Hg. RESULTS: Overall, 54/60 (90%) subjects (age 64 (8) yr; 44% female) completed the protocol, owing to failure of the FloTracIQ device in 6/60 (10%) patients. Intraoperative HPI-guided care was used in 28 subjects; 26 subjects were randomised to the control group. Postoperative hypotension occurred in 37/54 (68%) subjects. HPI-guided care did not reduce the median duration (TWA) of postoperative hypotension (adjusted median difference, vs standard of care: 0.118; 95% confidence interval [CI], 0-0.332; P=0.112). HPI-guidance reduced the percentage of time with MAP <65 mm Hg by 4.9% (adjusted median difference: -4.9; 95% CI, -11.7 to -0.01; P=0.046). CONCLUSIONS: Intraoperative HPI-guided haemodynamic care did not reduce the TWA of postoperative hypotension.

Clinical performance of a machine-learning algorithm to predict intra-operative hypotension with noninvasive arterial pressure waveforms: A cohort study.

BACKGROUND: Intra-operative hypotension is associated with adverse postoperative outcomes. A machine-learning-derived algorithm developed to predict hypotension based on arterial blood pressure (ABP) waveforms significantly reduced intra-operative hypotension. The algorithm calculates the likelihood of hypotension occurring within minutes, expressed as the Hypotension Prediction Index (HPI) which ranges from 0 to 100. Currently, HPI is only available for patients monitored with invasive ABP, which is restricted to high-risk procedures and patients. In this study, the performance of HPI, employing noninvasive continuous ABP measurements, is assessed. OBJECTIVES: The first aim was to compare the performance of the HPI algorithm, using noninvasive versus invasive ABP measurements, at a mathematically optimal HPI alarm threshold (Youden index). The second aim was to assess the performance of the algorithm using a HPI alarm threshold of 85 that is currently used in clinical trials. Hypotension was defined as a mean arterial pressure (MAP) below 65 mmHg for at least 1 min. The predictive performance of the algorithm at different HPI alarm thresholds (75 and 95) was studied. DESIGN: Observational cohort study. SETTING: Tertiary academic medical centre. PATIENTS: Five hundred and seven adult patients undergoing general surgery. RESULTS: The performance of the algorithm with invasive and noninvasive ABP input was similar. A HPI alarm threshold of 85 showed a median [IQR] time from alarm to hypotension of 2.7 [1.0 to 7.0] min with a sensitivity of 92.7 (95% confidence interval [CI], 91.2 to 94.3), specificity of 87.6 (95% CI, 86.2 to 89.0), positive predictive value of 79.9 (95% CI, 77.7 to 82.1) and negative predictive value of 95.8 (95% CI, 94.9 to 96.7). A HPI alarm threshold of 75 provided a lower positive predictive value but a prolonged time from prediction to actual hypotension. CONCLUSION: This study demonstrated that the algorithm can be employed using continuous noninvasive ABP waveforms. This opens up the potential to predict and prevent hypotension in a larger patient population. TRIAL REGISTRATION: Clinical trials registration number NCT03533205.

Goal-directed fluid therapy vs. low central venous pressure during major open liver resections (GALILEO): a surgeon- and patient-blinded randomized controlled trial.

BACKGROUND: Low central venous pressure (low-CVP) is the clinical standard for fluid therapy during major liver surgery. Although goal-directed fluid therapy (GDFT) has been associated with reduced morbidity and mortality in major abdominal surgery, concerns remain on blood loss when applying GDFT in liver surgery. This randomized trial compared outcomes of low-CVP and GDFT during major liver resections. METHODS: In this surgeon- and patient-blinded RCT, patients undergoing major open liver resections (≥3 segments) were randomized between low-CVP (n = 20) or GDFT (n = 20). Primary outcome was intraoperative blood loss. Secondary outcomes included the quality of the surgical field (VAS scale 0 (worst)-100 (best)) and major morbidity (≥grade 3 Clavien-Dindo). RESULTS: During surgery, CVP was 3 ± 2 mmHg in the low-CVP group vs. 7 ± 3 mmHg in the GDFT group (P < 0.001). Blood loss (1425 vs. 1275 mL; P = 0.640) and the rate of major morbidity (40% vs. 50%, P = 0.751), did not differ between low-CVP and GDFT, respectively. The quality of the surgical field was comparable between groups (low-CVP 83% vs. GDFT 80%, P = 0.955). CONCLUSION: In major open liver resections, GDFT was not associated with differences in intraoperative blood loss, major morbidity or quality of the surgical field, compared to low-CVP. Larger RCTs are needed to confirm this finding. Registration number: NTR5821 (www.trialregister.nl).

Colloid osmotic pressure of contemporary and novel transfusion products.

BACKGROUND AND OBJECTIVES: Colloid osmotic pressure (COP) is a principal determinant of intravascular fluid homeostasis and a pillar of fluid therapy and transfusion. Transfusion-associated circulatory overload (TACO) is a leading complication of transfusion, and COP could be responsible for recruiting additional fluid. Study objective was to measure COP of blood products as well as investigate the effects of product concentration and storage lesion on COP. MATERIALS AND METHODS: Three units of each product were sampled longitudinally. COP was measured directly as well as the determinants thereof albumin and total protein. Conventional blood products, that is red blood cell (RBC), fresh-frozen plasma (FFP) and platelet concentrates (PLTs), were compared with their concentrated counterparts: volume-reduced RBCs, hyperconcentrated PLTs, and fully and partially reconstituted lyophilized plasma (prLP). Fresh and maximally stored products were measured to determine changes in protein and COP. We calculated potential volume load (PVL) to estimate volume recruited using albumin's water binding per product. RESULTS: Colloid osmotic pressure varies widely between conventional products (RBCs, 1·9; PLTs, 7·5; and FFP, 20·1 mmHg); however, all are hypooncotic compared with human plasma COP (25·4 mmHg). Storage lesion did not increase COP. Concentrating RBCs and PLTs did not increase COP; only prLP showed a supraphysiological COP of 47·3 mm Hg. The PVL of concentrated products was lower than conventional products. CONCLUSION: Colloid osmotic pressure of conventional products was low. Therefore, third-space fluid recruitment is an unlikely mechanism in TACO. Concentrated products had a lower calculated fluid load and may prevent TACO. Finally, storage did not significantly increase oncotic pressure of blood products.

Effect of a Machine Learning-Derived Early Warning System for Intraoperative Hypotension vs Standard Care on Depth and Duration of Intraoperative Hypotension During Elective Noncardiac Surgery: The HYPE Randomized Clinical Trial.

Importance: Intraoperative hypotension is associated with increased morbidity and mortality. A machine learning-derived early warning system to predict hypotension shortly before it occurs has been developed and validated. Objective: To test whether the clinical application of the early warning system in combination with a hemodynamic diagnostic guidance and treatment protocol reduces intraoperative hypotension. Design, Setting, and Participants: Preliminary unblinded randomized clinical trial performed in a tertiary center in Amsterdam, the Netherlands, among adult patients scheduled for elective noncardiac surgery under general anesthesia and an indication for continuous invasive blood pressure monitoring, who were enrolled between May 2018 and March 2019. Hypotension was defined as a mean arterial pressure (MAP) below 65 mm Hg for at least 1 minute. Interventions: Patients were randomly assigned to receive either the early warning system (n = 34) or standard care (n = 34), with a goal MAP of at least 65 mm Hg in both groups. Main Outcomes and Measures: The primary outcome was time-weighted average of hypotension during surgery, with a unit of measure of millimeters of mercury. This was calculated as the depth of hypotension below a MAP of 65 mm Hg (in millimeters of mercury) × time spent below a MAP of 65 mm Hg (in minutes) divided by total duration of operation (in minutes). Results: Among 68 randomized patients, 60 (88%) completed the trial (median age, 64 [interquartile range {IQR}, 57-70] years; 26 [43%] women). The median length of surgery was 256 minutes (IQR, 213-430 minutes). The median time-weighted average of hypotension was 0.10 mm Hg (IQR, 0.01-0.43 mm Hg) in the intervention group vs 0.44 mm Hg (IQR, 0.23-0.72 mm Hg) in the control group, for a median difference of 0.38 mm Hg (95% CI, 0.14-0.43 mm Hg; P = .001). The median time of hypotension per patient was 8.0 minutes (IQR, 1.33-26.00 minutes) in the intervention group vs 32.7 minutes (IQR, 11.5-59.7 minutes) in the control group, for a median difference of 16.7 minutes (95% CI, 7.7-31.0 minutes; P < .001). In the intervention group, 0 serious adverse events resulting in death occurred vs 2 (7%) in the control group. Conclusions and Relevance: In this single-center preliminary study of patients undergoing elective noncardiac surgery, the use of a machine learning-derived early warning system compared with standard care resulted in less intraoperative hypotension. Further research with larger study populations in diverse settings is needed to understand the effect on additional patient outcomes and to fully assess safety and generalizability. Trial Registration: ClinicalTrials.gov Identifier: NCT03376347.

Preperitoneal or Subcutaneous Wound Catheters as Alternative for Epidural Analgesia in Abdominal Surgery: A Systematic Review and Meta-analysis.

OBJECTIVE: To assess whether the location of wound catheters (ie, preperitoneal vs. subcutaneous) impacts outcomes, when compared with alternatives such as epidural analgesia. BACKGROUND: Continuous wound infiltration is an alternative for epidural analgesia in abdominal surgery but studies have shown conflicting results. This difference could be explained by different efficacy of preperitoneal versus subcutaneous placement of the infiltrative catheters. METHODS: A systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines until April 3, 2017. Primary endpoints were pain scores in rest and when moving at 24 hours postoperatively. Secondary endpoints included postoperative pain scores at 12 and 48 hours, functional recovery, pain treatment-related complications, and patient satisfaction. RESULTS: After screening 2283 studies, 29 randomized controlled trials (RCTs) with 2059 patients were included. Methodological quality of these RCTs ranged from moderate to high. In the one direct comparison (60 patients), preperitoneal catheters led to better pain control than subcutaneous catheters. Superiority of preperitoneal compared with subcutaneous placement was confirmed indirectly in placebo-controlled RCTs. Preperitoneal wound catheters provided comparable pain control compared with active controls, such as epidural analgesia. Recovery parameters, opioid consumption, incidence of hypotension, and patient satisfaction seemed to be in favor of preperitoneal wound catheters compared with active alternatives, as well as placebo. CONCLUSION: Continuous wound infiltration with preperitoneal wound catheters is an effective pain modality in abdominal surgery. Pain control is as effective as epidural analgesia, but could be favored based upon recovery parameters and patient satisfaction.

Transfusion-associated circulatory overload-a systematic review of diagnostic biomarkers.

BACKGROUND: Transfusion-associated circulatory overload (TACO) is the leading cause of transfusion-related major morbidity and mortality. Diagnosing TACO is difficult because there are no pathognomonic signs and symptoms. TACO biomarkers may aid in diagnosis, decrease time to treatment, and differentiate from other causes of posttransfusion dyspnea such a transfusion-related acute lung injury. STUDY DESIGN AND METHODS: A systematic review of literature was performed in EMBASE, PubMed, the TRIP Database, and the Cochrane Library, from inception to June 2018. All articles discussing diagnostic markers for TACO were included. Non-English articles or conference abstracts were excluded. RESULTS: Twenty articles discussing biomarkers for TACO were included. The majority investigated B-type natriuretic peptide (BNP) and the N-terminal prohormone cleavage fragment of BNP (NT-proBNP), markers of hydrostatic pressure that can be determined within 1 hour. The data indicate that a post/pretransfusion NT-proBNP ratio > 1.5 can aid in the diagnosis of TACO. Posttransfusion levels of BNP less than 300 or NT-proBNP less than 2000 pg/mL, drawn within 24 hours of the reaction, make TACO unlikely. Cut-off levels that exclude TACO are currently unclear. In critically ill patients, the specificity of natriuretic peptides for circulatory overload is poor. Other biomarkers, such as cytokine profiles, cannot discriminate between TACO and transfusion-related acute lung injury. CONCLUSION: Currently, BNP and NT-proBNP are the primary diagnostic biomarkers researched for TACO. An NT-proBNP ratio greater than 1.5 is supportive of TACO, and low levels of BNP or NT-proBNP can exclude TACO. However, they are unreliable in critically ill patients. Other biomarkers, including cytokines and pulmonary edema fluid-to-serum protein ratio have not yet been sufficiently investigated for clinical use.

Volume incompliance and transfusion are essential for transfusion-associated circulatory overload: a novel animal model.

BACKGROUND: Transfusion-associated circulatory overload (TACO) is the predominant complication of transfusion resulting in death. The pathophysiology is poorly understood, but inability to manage volume is associated with TACO, and observational data suggest it is different from simple cardiac overload due to fluids. We developed a two-hit TACO animal model to assess the role of volume incompliance ("first-hit") and studied whether volume overload ("second-hit") by red blood cell (RBC) transfusion is different compared to fluids (Ringer's lactate [RL]). MATERIALS AND METHODS: Male adult Lewis rats were stratified into a control group (no intervention) or a first hit: either myocardial infarction (MI) or acute kidney injury (AKI). Animals were randomized to a second hit of either RBC transfusion or an equal volume of RL. A clinically relevant difference was defined as an increase in left ventricular end-diastolic pressure (ΔLVEDP) of +4.0 mm Hg between the RBC and RL groups. RESULTS: In control animals (without first hit) LVEDP was not different between infusion groups (Δ + 1.6 mm Hg). LVEDP increased significantly more after RBCs compared to RL in animals with MI (Δ7.4 mm Hg) and AKI (Δ + 5.4 mm Hg), respectively. Volume-incompliant rats matched clinical TACO criteria in 92% of transfused versus 25% of RL-infused animals, with a greater increase in heart rate and significantly higher blood pressure. CONCLUSION: To our knowledge, this is the first animal model for TACO, showing that a combination of volume incompliance and transfusion is essential for development of circulatory overload. This model allows for further testing of mechanistic factors as well as therapeutic approaches.

On-demand versus continuous rocuronium infusion for deep neuromuscular relaxation in patients undergoing thoraco-laparoscopic esophagectomy: a randomized-controlled clinical trial (DEPTH).

PURPOSE: Deep neuromuscular blockade (NMB) can improve surgical conditions and possibly pain after low-risk laparoscopic surgery. We hypothesized that targeting a deep level of NMB by a continuous compared with an on-demand infusion of rocuronium could improve surgical conditions in patients undergoing thoraco-laparoscopic esophagectomy. METHODS: In this single-centre, randomized-controlled, double-blind trial, patients received either a continuous infusion of rocuronium 0.6 mg·kg-1·hr-1 (intervention) or NaCl 0.9% (control). Both surgeon and anesthesiologist were blinded to group assignment and the train-of-four measurements. Open-label rocuronium was given if requested (i.e., on-demand) by the surgeon. At the end of surgery, sugammadex was given if necessary to reverse the NMB. The primary outcome was the quality of surgical conditions during the abdominal phase of the operation as measured by the surgical rating scale (SRS). Secondary outcomes included the thoracic SRS, number of on-demand boluses, intraoperative surgical events, pain scores (up to 12 hr postoperatively), and duration of surgery. RESULTS: The median [interquartile range] abdominal SRS was not different between the intervention (4 [4-5]) and control (4 [4-5]) groups (median difference, 0; 95% confidence interval, 0 to 0; P = 0.45). The thoracic SRS was 4 [4-4] in both groups (P = 0.23). The median number of rocuronium bolus requests was higher in the control group compared with the intervention group (3 [3-6] vs 1 [0-2], respectively; P < 0.01). There were no between-group differences in intraoperative surgical events (P = 0.05), pain scores (overall P > 0.05), or duration of surgery (P = 0.95). CONCLUSIONS: Continuous rocuronium infusion did not improve surgical conditions when boluses of rocuronium were available on-demand. No major benefits in other outcomes were seen. TRIAL REGISTRATION: EUDRACT (2014-002147-18); registered 19 May, 2014 and clinicaltrials.gov (NCT02320734); registered 18 December, 2014.

Intraoperative Incident Dark Field Imaging of the Human Peritoneal Microcirculation.

BACKGROUND/AIMS: This study describes the peritoneal microcirculation, compares quantitative parameters and angioarchitecture to the standard of sublingual microcirculatory assessment, and determines the practical feasibility of this method. METHODS: Incident dark field imaging was performed of the peritoneum and sublingually to determine angioarchitecture, total and perfused vessel density (TVD and PVD), the proportion of perfused vessels (PPV), the microvascular flow index (MFI) and image acquisition time. RESULTS: Peritoneal angioarchitecture was characterized by a quadrangular network of longitudinally oriented capillaries, often flanked by fat cells. Differences between peritoneal and sublingual microcirculation were observed with regard to TVD (peritoneum 12 mm/mm2 [95% CI 10-14] vs. sublingual 23 mm/mm2 [95% CI 21-25]; p < 0.0001), PVD (peritoneum 11 mm/mm2 [95% CI 9-13] vs. sublingual 23 mm/mm2 [95% CI 21-25]; p < 0.0001), PPV (peritoneum 88% [95% CI 79-97] vs. sublingual 99% [95% CI 99-100]; p = 0.014), and MFI (peritoneum 3 [IQR 2.3-3.0] vs. sublingual 3 [IQR 3.0-3.0]; p = 0.012). There was no difference in image acquisition time (peritoneum 2: 34 min [95% CI 1: 49-3: 19] vs. sublingual 2: 38 [95% CI 1: 37-3: 32]; p = 0.916). CONCLUSION: The peritoneal microcirculation was characterized by a low capillary density and a distinctive angioarchitecture. The possibility of peri-toneal microcirculatory assessment offers promise for the study of peritoneal (patho-)physiology and (monitoring or detection of) associated diseases.

Incidence, risk factors, and outcome of transfusion-associated circulatory overload in a mixed intensive care unit population: a nested case-control study.

BACKGROUND: The objective of this study was to determine the incidence, risk factors, and outcome of transfusion-associated circulatory overload (TACO) in a cohort of mixed intensive care unit patients and to compare risk factors with those for cardiac overload in the absence of transfusion. STUDY DESIGN AND METHODS: In a retrospective cohort study, patients who developed TACO were compared using multivariate analysis of two control groups: patients without pulmonary deterioration who received transfusion and patients who developed circulatory overload in the absence of transfusion. RESULTS: TACO was diagnosed in 66 of 1140 patients who received transfusions (5.8%). A total of 585 control transfusion recipients and 76 control patients who developed circulatory overload also were identified. Risk factors were the referring specialties cardiology (odds ratio [OR], 13.6; 95% confidence interval [CI], 5.1-35.7; p ≤ 0.001) and cardiothoracic surgery (OR, 8.8; 95% CI, 3.7-20.7; p ≤ 0.001), history of cardiac failure (OR, 2.4; 95% CI, 1.2-4.6; p = 0.01), continuous veno-venous hemofiltration (OR, 3.2; 95% CI, 1.2-8.9; p = 0.03), and degree of positive fluid balance (OR, 1.15; 95% CI, 1.07-1.24; p ≤ 0.001), which was associated less with the onset of TACO compared with circulatory overload (OR, 0.89; 95% CI, 0.82-0.97; p = 0.005). Patients in the TACO group had a longer length of stay in the intensive care unit compared with the transfusion and circulatory overload controls groups (median, 7.2 vs. 4.3 vs. 4.4 days; p = 0.001 vs. p = 0.008). CONCLUSIONS: The incidence of TACO is high in a mixed intensive care unit population. The risk factors identified for TACO are cardiac failure, renal failure, and degree of positive fluid balance. A positive fluid balance may be less essential in the onset of TACO than in the onset of circulatory overload in the absence of transfusion.