Comparison of calibrated and uncalibrated arterial pressure-based cardiac output monitors during orthotopic liver transplantation

An overview of unresolved issues in the perioperative management of liver transplant patients

Over the past decade, the field of solid organ transplantation has undergone significant changes, with some of the most notable advancements occurring in liver transplantation. Recent years have seen substantial progress in preoperative patient optimization protocols, anesthesia monitoring, coagulation management, and fluid management, among other areas. These improvements have led to excellent perioperative outcomes for all surgical patients, including those undergoing liver transplantation. In the last few decades, there have been numerous publications in the field of liver transplantation, but controversies related to perioperative management of liver transplant recipients persist. In this review article, we address the unresolved issues surrounding the anesthetic management of patients scheduled for liver transplantation.

What is the optimal anesthetic monitoring regarding immediate and short-term outcomes after liver transplantation?-A systematic review of the literature and expert panel recommendations

BACKGROUND

Liver transplant centers vary in approach to intraoperative vascular accesses, monitoring of cardiac function and temperature management. Evidence is limited regarding impact of selected modalities on postoperative outcomes.

OBJECTIVES

To review the literature and provide expert panel recommendations on optimal intraoperative arterial blood pressure (BP), central venous pressure (CVP), and vascular accesses, monitoring of cardiac function and intraoperative temperature management regarding immediate and short-term outcomes after orthotopic liver transplant (OLT).

METHODS

Systematic review following PRISMA guidelines and recommendations using the GRADE approach derived from an international expert panel. Recommendations made for: (1) Vascular accesses, arterial BP and CVP monitoring, (2) cardiac function monitoring, and (3) Intraoperative temperature management (CRD42021239908).

RESULTS

Of 2619 articles screened 16 were included. Studies were small, retrospective, and observational. Vascular access studies demonstrated low rates of insertion complications. TEE studies demonstrated low rates of esophageal hemorrhage. One study found lower hospital-LOS and 30-day mortality in patients monitored with both PAC and TEE. Other monitoring studies were heterogenous in design and outcomes. Temperature studies showed increased blood transfusion and ventilation times in hypothermic groups.

CONCLUSIONS

Recommendations were made for; routine arterial and CVP monitoring as a minimum standard of practice, consideration of discrepancy between peripheral and central arterial BP in patients with hemodynamic instability and high vasopressor requirements, and routine use of high flow cannulae while monitoring for extravasation and hematoma formation. Availability and expertise in PAC and/or TEE monitoring is strongly recommended particularly in hemodynamic instability, portopulmonary HT and/or cardiac dysfunction. TEE use is recommended as an acceptable risk in patients with treated esophageal varices and is an effective diagnostic tool for emergency cardiovascular collapse. Maintenance of intraoperative normothermia is strongly recommended.

The cardiac output optimisation following liver transplant (COLT) trial: a feasibility randomised controlled trial

BACKGROUND

Perioperative goal directed fluid therapy (GDFT) has been shown to reduce postoperative complications following major surgery; this intervention has not been formally evaluated in the setting of liver transplantation.

METHODS

We conducted a prospective trial of GDFT following liver transplantation randomising patients with liver cirrhosis to either 12 h of GDFT using non-invasive cardiac output monitoring or standard care (SC). The primary outcome was feasibility. Secondary outcomes included survival, postoperative complications (Clavien-Dindo), quality of life (by EQ-5D-5L) and resource use. Trial specific follow up occurred at 90 and 180 days after surgery.

RESULTS

The study was feasible. Of 224 eligible patients, 122 were approached, 114 consented to participate and 60 were enrolled into the trial. The mean (SD) volume of IV crystalloid administered to the GDFT group during the 12-h study period was 3968 (2073) ml for the GDFT group and 2510 (1026) ml for the SC group. As regards secondary outcomes there was no difference in survival or overall complication rates. There was no significant difference in quality of life scores and resource use between the groups.

CONCLUSION

A randomised study of GDFT following liver transplantation is feasible. A post-trial stakeholder meeting supported proceeding with a full multi-centre trial.

Noninvasive assessment of Cardiac Index using impedance cardiography during liver transplantation surgery: a comparison with pulmonary artery thermodilution

BACKGROUND

Liver transplantation (LT) is a high-risk surgery associated with significant hemodynamic changes requiring advanced hemodynamic monitoring. Pulmonary Artery Catheter (PAC) is still considered as a gold-standard for Cardiac Index (CI) measurement during LT despite association with an increased risk of complications. Noninvasive impedance cardiography (ICG) could be an interesting alternative tool for CI monitoring. The aim of this study was to compare the precision and trending ability of ICG versus PAC methods during LT.

METHODS

Patients undergoing LT were prospectively included. CI was measured with PAC and ICG at 4 time points (T1: before surgical incision, T2: during anhepatic phase, T3: after portal reperfusion, T4: during wound closure). Bias and percentage error (PE) between CI measured with PAC and ICG were analyzed with the Bland-Altman method for repeated measurements. Trending ability was studied with 4-quadrant and polar plots and correlation coefficient.

RESULTS

We included 43 patients with 156 measures. Mean bias was -0.95 L.min-1.m-2, SD±1.07, limits of agreement -3.73 to 1.83 L.min-1.m-2 and PE 58%. There was a significant increase in bias during LT (P<0.001). Assessment of trending ability displayed a concordance rate of 72% on the 4-quadrant plot and a mean angular bias of -8.4° (SD±28°) and radial limits of agreement ±55° on the polar plot.

CONCLUSIONS

CI measurements using ICG exhibited a low precision and a poor trending ability when compared to thermodilution method during LT. Consequently, ICG is not an adequate hemodynamic tool to monitor CI during LT.

Predictive values of pulse pressure variation and stroke volume variation for fluid responsiveness in patients with pneumoperitoneum

Animal studies suggest that dynamic predictors remain useful in patients with pneumoperitoneum, but human data is conflicting. Our aim was to determine predictive values of pulse pressure variation (PPV) and stroke volume variation (SVV) in patients with pneumoperitoneum using LiDCORapid™ haemodynamic monitor. Standardised fluid challenges of colloid were administered to patients undergoing laparoscopic procedures, one fluid challenge per patient. Intra-abdominal pressure was automatically held at 12 mmHg. Fluid responsiveness was defined as an increase in nominal stroke index (nSI) ≥ 10%. Linear regression was used to assess the ability of PPV and SVV to track the changes of nSI and logistic regression and area under the receiver operating curve (AUROC) to assess the predictive value of PPV and SVV for fluid responsiveness. Threshold values for PPV and SVV were obtained using the "gray zone" approach. A p < 0.05 was considered as statistically significant. 56 patients were included in analysis. 41 patients (73%) responded to fluids. Both PPV and SVV tracked changes in nSI (Spearman correlation coefficients 0.34 for PPV and 0.53 for SVV). Odds ratio for fluid responsiveness for PPV was 1.163 (95% CI 1.01-1.34) and for SVV 1.341 (95% CI 1.10-1.63). PPV achieved an AUROC of 0.674 (95% CI 0.518-0.830) and SVV 0.80 (95% CI 0.668-0.932). The gray zone of PPV ranged between 6.5 and 20.5% and that of SVV between 7.5 and 13%. During pneumoperitoneum, as measured by LiDCORapid™, PPV and SVV can predict fluid responsiveness, however their sensitivity is lower than the one reported in conditions without pneumoperitoneum. Trial registry number: (with the Australian New Zealand Clinical Trials Registry): ACTRN12612000456853.

The photoplethysmographic amplitude to pulse pressure ratio can track sudden changes in vascular compliance and resistance during liver graft reperfusion: A beat-to-beat analysis

During liver transplantation, the thermodilution cardiac output (CO) technique cannot respond to sudden hemodynamic changes associated with postreperfusion syndrome. Photoplethysmography (PPG) can reflect changes in intravascular volume and thus can be used to assess vasomotor tone and arterial stiffness on the pressure-volume relation. We investigated whether a beat-to-beat analysis of the arterial pressure-PPG relationship can estimate dynamic changes in vascular characteristics immediately after liver graft reperfusion.In 10 recipients, arterial blood pressure and PPG waveforms recorded simultaneously were analyzed from the beginning of fall to nadir in systolic blood pressure immediately after reperfusion. On a beat-to-beat basis, we compared the ratio of the amplitude of PPG to arterial pulse pressure (PPGamp/PP, as relative vascular compliance) to total peripheral resistance (TPR) and Windkessel compliance (Cwk) obtained from the Modelflow CO algorithm.Following graft reperfusion, PPGamp/PP and Cwk increased (median 41.5%; P = .005 and 42.0%; P < .001, respectively), whereas TPR decreased (median -46.4%; P < .001). Beat-to-beat PPGamp/PP was negatively correlated with TPR (median r = -0.80 [95% CI -0.85 to -0.76] on linear regression and r = 0.84 [95% CI 0.73-0.92] on curvilinear regression), and was positively correlated with Cwk (median r = 0.86 [95% CI 0.81-0.91] on linear regression and r = 0.88 [95% CI 0.75-0.96] on curvilinear regression).Our results suggest that relative compliance, obtained from beat-to-beat analysis of PPG and arterial pressure waveforms, can track abrupt changes in vascular characteristics associated with postreperfusion syndrome. This simple index would contribute to differential diagnoses of sudden hypotension.

Cardiac Output Assessed by the Fourth-Generation Arterial Waveform Analysis System Is Unreliable in Liver Transplant Recipients

BACKGROUND

Liver transplant recipients often have violent hemodynamic fluctuation during surgery that may be related to perioperative and postoperative morbidity. Because there are some considerations for the risk of the pulmonary arterial catheter (PAC), the conventional invasive device for cardiac output (CO) measurement, a reliable and minimally invasive alternative is required. We validated the reliability of CO measurements with the use of a minimally invasive FloTrac system with the latest fourth-generation algorithm in liver transplant recipients.

METHODS

Forty liver transplant recipients without atrial fibrillation, valvular pathology, or intracardiac shunt were recruited in this prospective, observational study. CO values measured by use of PAC with continuous thermodilution method (COTh) and FloTrac devices (COFT) were collected simultaneously throughout the operation for reliability validation.

RESULTS

Four hundred pairs of CO data points were collected in total. The linear regression analysis showed a high correlation coefficient (73%, P < .001). However, the percent error between COTh and COFT was 42.2%, which is worse than the established interchangeability criterion of 30%. The concordance rates were calculated at 89% and 59% by 4-quadrant plot and polar plot analysis, respectively. Neither met the preset validation criteria (>92% for the 4-quadrant plot and >90% for polar plot analyses).

CONCLUSIONS

Our study demonstrates that the CO measurements in liver transplant recipients by the latest FloTrac system and the PAC do not meet the recognized interchangeability criterion. Although the result showed improvement in linear regression analysis, it failed to display a qualified trending ability.

Evaluation of New Calibrated Pulse-Wave Analysis (VolumeViewTM/EV1000TM) for Cardiac Output Monitoring Undergoing Living Donor Liver Transplantation

Background

Intrapulmonary thermodilution technique using a pulmonary artery catheter is widely used for measuring cardiac output (CO) in patients undergoing liver transplantation. However, its invasiveness and associated complications have led to an interest in less invasive modalities. Thus, we aimed to evaluate whether the new calibrated pulse-wave analysis method monitoring (VolumeView^TM/EV1000^TM) is interchangeable with intrapulmonary thermodilution technique.

Methods

Twenty-eight patients undergoing living donor liver transplantation were enrolled in this prospective observational study. COs were recorded automatically by the two devices and compared simultaneously at 10-minute intervals. The agreement of absolute CO values and the tracking ability of CO changes trends were compared. A Bland-Altman analysis with percentage errors and concordance rate for trend analysis using both a 4-quadrant plot and a polar plot were performed on the data.

Results

A total of 375 paired datasets from 25 patients were included in analysis. COs measured by intrapulmonary thermodilution ranged from 3.8–13.7 L/min. The mean CO difference between the two techniques was 0.57 L/min, and the 95% limits of agreement were -0.98 L/min to 2.12 L/min with a percentage error of 42.3%. The percentage errors in the dissection, anhepatic, and reperfusion phase were 30.5%, 31.7%, and 27.4%, respectively. The concordance rate between the two techniques was 78.4%.

Conclusion

The calibrated pulse-wave analysis and intrapulmonary thermodilution failed to show acceptable interchangeability in terms of both estimating CO and tracking CO changes during living donor liver transplantation.

Agreement in hemodynamic monitoring during orthotopic liver transplantation: a comparison of FloTrac/Vigileo at two monitoring sites with pulmonary artery catheter thermodilution

To study agreement in cardiac index (CI), systemic vascular resistance index (Systemic VRI) and stroke volume variation (SV variation) between the FloTrac/Vigileo at radial and femoral arterial cannulation sites, and pulmonary artery catheter (PAC) thermodilution, in patients undergoing orthotopic liver transplantation. A prospective observational study of 25 adult patients with liver failure. Radial and femoral arteries were cannulated with standardised FloTrac/Vigileo arterial transducer kits and a PAC was inserted. CI, SV variation and Systemic VRI were measured four times (30 min after induction of anesthesia, 30 min after portal vein clamping, 30 min after graft reperfusion, 30 min after commencement of bile duct anastomosis). The bias, precision, limits of agreement (LOA) and percentage errors were calculated using Bland-Altman statistics to compare measurements from radial and femoral arterial cannulation sites and PAC thermodilution. Neither radial nor femoral CI achieved acceptable agreement with PAC CI [radial to PAC bias (SD) 1.17 (1.49) L/min/m², percentage error 64.40 %], [femoral to PAC bias (SD) -0.71 (1.81) L/min/m², percentage error 74.20 %]. Agreement between radial and femoral sites for CI [mean difference (SD) -0.43 (1.51) L/min/m², percentage error 70.40 %] and Systemic VRI [mean difference (SD) 0.03 (4.17) LOA ±8.17 mmHg min m²/L] were also unacceptable. Agreement in SV variation between radial and femoral measurement sites approached a clinically acceptable threshold [mean difference (SD) 0.68 (2.44) %), LOA ±4.78 %]. FloTrac/Vigileo CI cannot substitute for PAC thermodilution CI, regardless of measurement site. SV variation measurements may be interchangeable between radial and femoral sites for determining fluid responsiveness.

Agreement in hemodynamic monitoring during orthotopic liver transplantation: a comparison of FloTrac/Vigileo at two monitoring sites with pulmonary artery catheter thermodilution

To study agreement in cardiac index (CI), systemic vascular resistance index (Systemic VRI) and stroke volume variation (SV variation) between the FloTrac/Vigileo at radial and femoral arterial cannulation sites, and pulmonary artery catheter (PAC) thermodilution, in patients undergoing orthotopic liver transplantation. A prospective observational study of 25 adult patients with liver failure. Radial and femoral arteries were cannulated with standardised FloTrac/Vigileo arterial transducer kits and a PAC was inserted. CI, SV variation and Systemic VRI were measured four times (30 min after induction of anesthesia, 30 min after portal vein clamping, 30 min after graft reperfusion, 30 min after commencement of bile duct anastomosis). The bias, precision, limits of agreement (LOA) and percentage errors were calculated using Bland-Altman statistics to compare measurements from radial and femoral arterial cannulation sites and PAC thermodilution. Neither radial nor femoral CI achieved acceptable agreement with PAC CI [radial to PAC bias (SD) 1.17 (1.49) L/min/m², percentage error 64.40 %], [femoral to PAC bias (SD) -0.71 (1.81) L/min/m², percentage error 74.20 %]. Agreement between radial and femoral sites for CI [mean difference (SD) -0.43 (1.51) L/min/m², percentage error 70.40 %] and Systemic VRI [mean difference (SD) 0.03 (4.17) LOA ±8.17 mmHg min m²/L] were also unacceptable. Agreement in SV variation between radial and femoral measurement sites approached a clinically acceptable threshold [mean difference (SD) 0.68 (2.44) %), LOA ±4.78 %]. FloTrac/Vigileo CI cannot substitute for PAC thermodilution CI, regardless of measurement site. SV variation measurements may be interchangeable between radial and femoral sites for determining fluid responsiveness.

Minimally invasive monitoring

Although use of the classic pulmonary artery catheter has declined, several techniques have emerged to estimate cardiac output. Arterial pressure waveform analysis computes cardiac output from the arterial pressure curve. The method of estimating cardiac output for these devices depends on whether they need to be calibrated by an independent measure of cardiac output. Some newer devices have been developed to estimate cardiac output from an arterial curve obtained noninvasively with photoplethysmography, allowing a noninvasive beat-by-beat estimation of cardiac output. This article describes the different devices that perform pressure waveform analysis.

Bioreactance Is Not Interchangeable with Thermodilution for Measuring Cardiac Output during Adult Liver Transplantation

Background

Thermodilution technique using a pulmonary artery catheter is widely used for the assessment of cardiac output (CO) in patients undergoing liver transplantation. However, the unclearness of the risk-benefit ratio of this method has led to an interest in less invasive modalities. Thus, we evaluated whether noninvasive bioreactance CO monitoring is interchangeable with thermodilution technique.

Methods

Nineteen recipients undergoing adult-to-adult living donor liver transplantation were enrolled in this prospective observational study. COs were recorded automatically by the two devices and compared simultaneously at 3-minute intervals. The Bland–Altman plot was used to evaluate the agreement between bioreactance and thermodilution. Clinically acceptable agreement was defined as a percentage error of limits of agreement <30%. The four quadrant plot was used to evaluate concordance between bioreactance and thermodilution. Clinically acceptable concordance was defined as a concordance rate >92%.

Results

A total of 2640 datasets were collected. The mean CO difference between the two techniques was 0.9 l/min, and the 95% limits of agreement were -3.5 l/min and 5.4 l/min with a percentage error of 53.9%. The percentage errors in the dissection, anhepatic, and reperfusion phase were 50.6%, 56.1%, and 53.5%, respectively. The concordance rate between the two techniques was 54.8%.

Conclusion

Bioreactance and thermodilution failed to show acceptable interchangeability in terms of both estimating CO and tracking CO changes in patients undergoing liver transplantation. Thus, the use of bioreactance as an alternative CO monitoring to thermodilution, in spite of its noninvasiveness, would be hard to recommend in these surgical patients.

Accuracy of Vigileo/Flotrac monitoring system in morbidly obese patients

PURPOSE

Our goal was to assess the accuracy of measuring cardiac output (CO) by the FloTrac/Vigileo (CO(V)) device in comparison with thermodilution technique through pulmonary artery catheterization (PAC(TD)) in morbidly obese patients.

MATERIAL AND METHODS

Cardiac output in 8 morbidly obese patients was assessed twice at upright and lying position breathing ambient air. At least 4 consecutive CO measurements with 10 mL of ice-cold saline injections were performed each time. Simultaneous CO measurements were recorded with both single-bolus thermodilution and CO(V).

RESULTS

One hundred thirty-two CO data pairs were collected. The overall mean single-bolus thermodilution 6.2 ± 1.1 L/min was lower than the overall mean CO(V) 7.8 ± 1.6 L/min (P < .001). Lin concordance coefficient indicated that overall agreement between PAC(TD) and CO(V) was poor, 0.29. Lin concordance coefficient in sitting position was 0.29, 95% confidence interval (0.17-0.40) and in lying position was 0.30, 95% confidence interval (0.15-0.44). The Bland-Altman plot analysis showed systematically higher values from CO(V) in comparison with PAC(TD). These differences increased in presence of high CO measurements. In 3 of 8 patients, the percentage error was lower than 20%, whereas in the other 5, it was higher than 20%. Of these 5, in 2 cases, the percentage error was greater than 50%.

CONCLUSION

Data obtained using CO(V) vs PAC(TD) measurements showed poor correlation. The results were not interchangeable.

Inter-device differences in monitoring for goal-directed fluid therapy

PURPOSE

Goal-directed fluid therapy is an integral component of many Enhanced Recovery After Surgery (ERAS) protocols currently in use. The perioperative clinician is faced with a myriad of devices promising to deliver relevant physiologic data to better guide fluid therapy. The goal of this review is to provide concise information to enable the clinician to make an informed decision when choosing a device to guide goal-directed fluid therapy.

PRINCIPAL FINDINGS

The focus of many devices used for advanced hemodynamic monitoring is on providing measurements of cardiac output, while other, more recent, devices include estimates of fluid responsiveness based on dynamic indices that better predict an individual's response to a fluid bolus. Currently available technologies include the pulmonary artery catheter, esophageal Doppler, arterial waveform analysis, photoplethysmography, venous oxygen saturation, as well as bioimpedance and bioreactance. The underlying mechanistic principles for each device are presented as well as their performance in clinical trials relevant for goal-directed therapy in ERAS.

CONCLUSIONS

The ERAS protocols typically involve a multipronged regimen to facilitate early recovery after surgery. Optimizing perioperative fluid therapy is a key component of these efforts. While no technology is without limitations, the majority of the currently available literature suggests esophageal Doppler and arterial waveform analysis to be the most desirable choices to guide fluid administration. Their performance is dependent, in part, on the interpretation of dynamic changes resulting from intrathoracic pressure fluctuations encountered during mechanical ventilation. Evolving practice patterns, such as low tidal volume ventilation as well as the necessity to guide fluid therapy in spontaneously breathing patients, will require further investigation.

Arterial waveform analysis

The bedside measurement of continuous arterial pressure values from waveform analysis has been routinely available via indwelling arterial catheterization for >50 years. Invasive blood pressure monitoring has been utilized in critically ill patients, in both the operating room and critical care units, to facilitate rapid diagnoses of cardiovascular insufficiency and monitor response to treatments aimed at correcting abnormalities before the consequences of either hypo- or hypertension are seen. Minimally invasive techniques to estimate cardiac output (CO) have gained increased appeal. This has led to the increased interest in arterial waveform analysis to provide this important information, as it is measured continuously in many operating rooms and intensive care units. Arterial waveform analysis also allows for the calculation of many so-called derived parameters intrinsically created by this pulse pressure profile. These include estimates of left ventricular stroke volume (SV), CO, vascular resistance, and during positive-pressure breathing, SV variation, and pulse pressure variation. This article focuses on the principles of arterial waveform analysis and their determinants, components of the arterial system, and arterial pulse contour. It will also address the advantage of measuring real-time CO by the arterial waveform and the benefits to measuring SV variation. Arterial waveform analysis has gained a large interest in the overall assessment and management of the critically ill and those at a risk of hemodynamic deterioration.

Semi-invasive measurement of cardiac output based on pulse contour: a review and analysis

PURPOSE

The aim of this review was to provide a meta-analysis of all five of the most popular systems for arterial pulse contour analysis compared with pulmonary artery thermodilution, the established reference method for measuring cardiac output (CO). The five investigated systems are FloTrac/Vigileo(®), PiCCO(®), LiDCO/PulseCO(®), PRAM/MostCare(®), and Modelflow.

SOURCE

In a comprehensive literature search through MEDLINE(®), Web of Knowledge (v.5.11), and Google Scholar, we identified prospective studies and reviews that compared the pulse contour approach with the reference method (n = 316). Data extracted from the 93 selected studies included range and mean cardiac output, bias, percentage error, software versions, and study population. We performed a pooled weighted analysis of their precision in determining CO in various patient groups and clinical settings.

PRINCIPAL FINDINGS

Results of the majority of studies indicate that the five investigated systems show acceptable accuracy during hemodynamically stable conditions. Forty-three studies provided adequate data for a pooled weighted analysis and resulted in a mean (SD) total pooled bias of -0.28 (1.25) L·min(-1), percentage error of 40%, and a correlation coefficient of r = 0.71. In hemodynamically unstable patients (n = 8), we found a higher percentage error (45%) and bias of -0.54 (1.64) L·min(-1).

CONCLUSION

During hemodynamic instability, CO measurement based on continuous arterial pulse contour analysis shows only limited agreement with intermittent bolus thermodilution. The calibrated systems seem to deliver more accurate measurements than the auto-calibrated or the non-calibrated systems. For reliable use of these semi-invasive systems, especially for critical therapeutic decisions during hemodynamic disorders, both a strategy for hemodynamic optimization and further technological improvements are necessary.

Systematic review of uncalibrated arterial pressure waveform analysis to determine cardiac output and stroke volume variation

The FloTrac/Vigileo™, introduced in 2005, uses arterial pressure waveform analysis to calculate cardiac output (CO) and stroke volume variation (SVV) without external calibration. The aim of this systematic review is to evaluate the performance of the system. Sixty-five full manuscripts on validation of CO measurements in humans, published in English, were retrieved; these included 2234 patients and 44,592 observations.

RESULTS

have been analysed according to underlying patient conditions, that is, general critical illness and surgery as normodynamic conditions, cardiac and (post)cardiac surgery as hypodynamic conditions, and liver surgery and sepsis as hyperdynamic conditions, and subsequently released software versions. Eight studies compared SVV with other dynamic indices. CO, bias, precision, %error, correlation, and concordance differed among underlying conditions, subsequent software versions, and their interactions, suggesting increasing accuracy and precision, particularly in hypo- and normodynamic conditions. The bias and the trending capacity remain dependent on (changes in) vascular tone with most recent software. The SVV only moderately agreed with other dynamic indices, although it was helpful in predicting fluid responsiveness in 85% of studies addressing this. Since its introduction, the performance of uncalibrated FloTrac/Vigileo™ has improved particularly in hypo- and normodynamic conditions. A %error at or below 30% with most recent software allows sufficiently accurate and precise CO measurements and trending for routine clinical use in normo- and hypodynamic conditions, in the absence of large changes in vascular tone. The SVV may usefully supplement these measurements.

Perioperative goal-directed hemodynamic therapy based on radial arterial pulse pressure variation and continuous cardiac index trending reduces postoperative complications after major abdominal surgery: a multi-center, prospective, randomized study

Introduction

Several single-center studies and meta-analyses have shown that perioperative goal-directed therapy may significantly improve outcomes in general surgical patients. We hypothesized that using a treatment algorithm based on pulse pressure variation, cardiac index trending by radial artery pulse contour analysis, and mean arterial pressure in a study group (SG), would result in reduced complications, reduced length of hospital stay and quicker return of bowel movement postoperatively in abdominal surgical patients, when compared to a control group (CG).

Methods

160 patients undergoing elective major abdominal surgery were randomized to the SG (79 patients) or to the CG (81 patients). In the SG hemodynamic therapy was guided by pulse pressure variation, cardiac index trending and mean arterial pressure. In the CG hemodynamic therapy was performed at the discretion of the treating anesthesiologist. Outcome data were recorded up to 28 days postoperatively.

Results

The total number of complications was significantly lower in the SG (72 vs. 52 complications, p = 0.038). In particular, infection complications were significantly reduced (SG: 13 vs. CG: 26 complications, p = 0.023). There were no significant differences between the two groups for return of bowel movement (SG: 3 vs. CG: 2 days postoperatively, p = 0.316), duration of post anesthesia care unit stay (SG: 180 vs. CG: 180 minutes, p = 0.516) or length of hospital stay (SG: 11 vs. CG: 10 days, p = 0.929).

Conclusions

This multi-center study demonstrates that hemodynamic goal-directed therapy using pulse pressure variation, cardiac index trending and mean arterial pressure as the key parameters leads to a decrease in postoperative complications in patients undergoing major abdominal surgery.

Trial registration

ClinicalTrial.gov, NCT01401283.

Stroke volume optimization in elective bowel surgery: a comparison between pulse power wave analysis (LiDCOrapid) and oesophageal Doppler (CardioQ)

BACKGROUND

Goal-directed fluid therapy improves outcome in major surgery. We evaluated a new device (LiDCOrapid) against our standard oesophageal Doppler method (ODM) for stroke volume (SV) optimization during colorectal surgery.

METHODS

This was an observational study in 20 patients undergoing major colorectal surgery within a fast-track protocol. We compared SV values measured simultaneously by LiDCOrapid and ODM before and after 86 fluid challenges. We also evaluated the LiDCOrapid dynamic indices SV variation (SVV) and pulse pressure variation (PPV) as predictors for volume responsiveness, defined as an increase in SV ≥ 10% after 200 ml of colloid.

RESULTS

SV increased ≥ 10% after 27 out of 86 fluid challenges. For 172 paired SV values, the overall correlation was r=0.39, and bias (limits of agreement) -28 (-91-35) ml, percentage error 70%. The ability of LiDCOrapid to track changes in SV was weak with a concordance rate of 80%, and a sensitivity and specificity of 48% and 81%, respectively, to detect a positive fluid challenge. The area under the curve values (with 95% confidence intervals) for SVV and PPV were 0.72 (0.60-0.83) and 0.66 (0.52-0.79), respectively, indicating low predictive capacity in these setting.

CONCLUSIONS

LiDCOrapid and ODM devices are not interchangeable. We cannot recommend that the LiDCOrapid replace the standard Doppler method until further device-specific outcome studies on volume optimization are available. The dynamic indices SVV and PPV add little value to a fluid optimization protocol, and should not replace SV measurements with a validated technique.

Liver transplantation: Advances and perioperative care

Liver transplantation is one of the treatments for many-life threatening liver diseases. Numerous advances in liver transplant surgery, anaesthesia and perioperative care have allowed for an increasing number of these procedures. The purpose of this review is to consider some of the important advances in perioperative care of liver transplant patients such as pre-operative evaluation, intraoperative monitoring and management and early extubation. A PubMed and EMBASE search of terms “Anaesthesia” and “Liver Transplantation” were performed with filters of articles in “English”, “Adult” and relevant recent publications of randomised control trial, editorial, systemic review and non-systemic review were selected and synthesized according to the author's personal and professional perspective in the field of liver transplantation and anaesthesia. The article outlines strategies in organ preservation, training and transplant database for further research.

Arterial waveform analysis in anesthesia and critical care

PURPOSE OF REVIEW

In this review, we describe the basic principles of arterial waveform analysis (AWA) to assess cardiac output (CO) and cardiac preload. The validity of commercially based hemodynamic monitoring systems is discussed, together with their clinical applications and limitations.

RECENT FINDINGS

Currently, three devices (the FloTrac system, PiCCO monitor, and LiDCO system) are available for measurement of AWA-based CO. In addition, dynamic preload parameters such as stroke volume variation (SVV) and pulse pressure variation (PPV) are determined, which may be useful to predict fluid responsiveness in mechanically ventilated patients.

SUMMARY

AWA provides a less invasive and easy-to-use alternative for CO measurement. The validity of AWA devices has been verified in a variety of patients and circumstances, but their performance is compromised in the presence of hemodynamic instability, cardiac arrhythmias, or other factors disturbing the arterial pressure waveform. The definitive role of dynamic preload parameters like SVV and PPV is a matter of research. Large trials in which the value of early goal-directed therapy using this technology is studied in relation to outcome are urgently needed.

Cardiac output assessed by invasive and minimally invasive techniques

Cardiac output (CO) measurement has long been considered essential to the assessment and guidance of therapeutic decisions in critically ill patients and for patients undergoing certain high-risk surgeries. Despite controversies, complications and inherent errors in measurement, pulmonary artery catheter (PAC) continuous and intermittent bolus techniques of CO measurement continue to be the gold standard. Newer techniques provide less invasive alternatives; however, currently available monitors are unable to provide central circulation pressures or true mixed venous saturations. Esophageal Doppler and pulse contour monitors can predict fluid responsiveness and have been shown to decrease postoperative morbidity. Many minimally invasive techniques continue to suffer from decreased accuracy and reliability under periods of hemodynamic instability, and so few have reached the level of interchangeability with the PAC.

Evaluation of a new software version of the FloTrac/Vigileo (version 3.02) and a comparison with previous data in cirrhotic patients undergoing liver transplant surgery

BACKGROUND

Reliable cardiac output monitoring is particularly useful in the cirrhotic patient undergoing liver transplant surgery, because cirrhosis of the liver is associated with a vasodilated and high output state, known as cirrhotic cardiomyopathy, that challenges the reliability of pulse contour cardiac output technology. The contractility of the ventricle in cirrhosis is impaired, which is tolerated even though the ejection fraction and cardiac output are elevated because of the low peripheral resistance. However, during surgery the cirrhotic patient can decompensate because of the physiological changes and stress of surgery. Recently, we showed that the FloTrac/Vigileo™ failed to perform in cirrhotic patients undergoing transplant surgery. In response, the company upgraded their software. Therefore, we have assessed the accuracy and reliability of this new third-generation (version 3.02) FloTrac/Vigileo algorithm software in the same setting.

METHODS

The cardiac index was measured simultaneously by single-bolus thermodilution (CI(TD)), using a pulmonary artery catheter, and pulse contour analysis, using the FloTrac/Vigileo (CI(V)). Readings were made at 10 time points during and after liver transplant surgery in 21 patients. Comparisons with data from our 2009 study, which used second-generation (version 01.10) software, were also made.

RESULTS

Our new data show that version 3.02 software significantly reduced the adverse effect on pulse contour cardiac output reading bias in low peripheral resistance states, and thus improves the overall precision and trending ability of the system. Regression analysis between CI(TD) and CI(V) showed that the correlation was moderate (r =0.67, 95% confidence interval, 0.40 to 0.86). The Bland and Altman analysis showed that bias was 0.4 L.min(-1) · m(-2), and the percentage error was 52% (95% confidence interval, 49% to 55%). Trending ability of the new software also was improved but was still well below the current benchmarks.

CONCLUSION

The new software (version 3.02) provided substantial improvements over the previous versions with better overall precision and trending ability. Further algorithm refinements will increase this technology's reliability to be extensively used in the highly complex setting of cirrhotic patients undergoing liver transplantation.