Perioperative fluid and volume management: physiological basis, tools and strategies

Fluid balance, change in serum creatinine and urine output as markers of acute kidney injury post cardiac surgery: an observational study

Background

Acute kidney injury (AKI) is defined as oliguria or rise in serum creatinine but oliguria alone as a diagnostic criterion may over-diagnose AKI.

Objectives

Given the association between fluid overload and AKI, we aimed to determine if positive fluid balance can complement the known parameters in assessing outcomes of AKI.

Design

Prospective observational study.

Setting

Teaching hospital in Vancouver, Canada.

Patients

111 consecutive patients undergoing elective cardiac surgery from January to April 2012.

Measurements

Outcomes of cardiac surgery intensive care unit (CSICU) and hospital length of stay (LOS) in relation to fluid balance, urine output and serum creatinine.

Methods

All fluid input and output was recorded for 72 hours post-operatively. Positive fluid balance was defined as >6.5 cc/kg. Daily serum creatinine and hourly urine output were recorded and patients were defined as having AKI according to the AKIN criteria.

Results

Of the patients who were oliguric, those with fluid overload trended towards longer LOS than those without fluid overload [CSICU LOS: 62 and 39 hours (unadjusted p-value 0.02, adjusted p-value 0.58); hospital LOS: 13 and 9 days (unadjusted p-value: 0.05, adjusted p-value: 0.16)]. Patients with oliguria who were fluid overloaded had similar LOS to patients with overt AKI (change in serum creatinine ≥ 26.5 µmol/L), [CSICU LOS: 62 and 69 hours (adjusted p value: 0.32) and hospital LOS: 13 and 14 days (adjusted p value: 0.19)]. Patients with oliguria regardless of fluid balance had longer CSICU LOS (adjusted p value: 0.001) and patients who were fluid overloaded in the absence of AKI had longer hospital LOS (adjusted p value: 0.02).

Limitations

Single centre, small sample, LOS as outcome.

Conclusions

Oliguria and positive fluid balance is associated with a trend towards longer LOS as compared to oliguria alone. Fluid balance may therefore be a useful marker of AKI, in addition to urine output and serum creatinine.

Understanding Off-Label Use and Reference Blood Flows in Modern Membrane Oxygenators

This editorial will address two issues that are still a source of global controversy and confusion in present day perfusion practice. Membrane oxygenators are designed and tested to a set of stringent flow standards prior to their release from every manufacturer. But how well do we know the iatrogenic consequences of pushing these devices beyond their maximum rated limits? In addition, how well do we know the meaning of the term 'AAMI Reference Flow' as it relates to the Manufacturers Maximum Rated Flow?

Perioperative blood management

Perioperative anaemia and allogenic blood transfusion (ABT) are known to increase the risk of adverse clinical outcomes. The quality, cost and availability of blood components are also major limitations with regard to ABT. Perioperative patient blood management (PBM) strategies should be aimed at minimizing and improving utilization of blood components. The goals of PBM are adequate preoperative evaluation and optimization of haemoglobin and bleeding parameters, techniques to minimize blood loss, blood conservation technologies and use of transfusion guidelines with targeted therapy. Attention to these details can help in cost reduction and improved patient outcome.

Anaesthetic management of renal transplant surgery in patients of dilated cardiomyopathy with ejection fraction less than 40%

Cardiovascular disease (CVD) is an important comorbidity of chronic kidney disease, and reducing cardiovascular events in this population is an important goal for the clinicians who care for chronic kidney disease patients. The high risk for CVD in transplant recipients is in part explained by the high prevalence of conventional CVD risk factors (e.g., diabetes, hypertension, and dyslipidemia) in this patient population. Current transplant success allows recipients with previous contraindications to transplant to have access to this procedure with more frequency and safety. Herein we provide a series of eight patients with dilated cardiomyopathy with poor ejection fraction posted for live donor renal transplantation which was successfully performed under regional anesthesia with sedation.

Early-phase changes of extravascular lung water index as a prognostic indicator in acute respiratory distress syndrome patients

Background

The features of early-phase acute respiratory distress syndrome (ARDS) are leakage of fluid into the extravascular space and impairment of its reabsorption, resulting in extravascular lung water (EVLW) accumulation. The current study aimed to identify how the initial EVLW values and their change were associated with mortality.

Methods

This was a post hoc analysis of the PiCCO Pulmonary Edema Study, a multicenter prospective cohort study that included 23 institutions. Single-indicator transpulmonary thermodilution-derived EVLW index (EVLWi) and conventional prognostic factors were prospectively collected over 48 h after enrollment. Associations between 28-day mortality and each variable including initial (on day 0), mean, maximum, and Δ (subtracting day 2 from day 0) EVLWi were evaluated.

Results

We evaluated 192 ARDS patients (median age, 69 years (quartile, 24 years); Sequential Organ Failure Assessment (SOFA) score on admission, 10 (5); all-cause 28-day mortality, 31%). Although no significant differences were found in initial, mean, or maximum EVLWi, Δ-EVLWi was significantly higher (i.e., more reduction in EVLWi) in survivors than in non-survivors (3.0 vs. −0.3 mL/kg, p = 0.006). Age, maximum, and Δ-SOFA scores and Δ-EVLW were the independent predictors for survival according to the Cox proportional hazard model. Patients with Δ-EVLWi > 2.8 had a significantly higher incidence of survival than those with Δ-EVLWi ≤ 2.8 (log-rank test, χ² = 7.08, p = 0.008).

Conclusions

Decrease in EVLWi during the first 48 h of ARDS may be associated with 28-day survival. Serial EVLWi measurements may be useful for understanding the pathophysiologic conditions in ARDS patients. A large multination confirmative trial is required.

Guiding principles of fluid and volume therapy

Fluid therapy is a core concept in the management of perioperative and critically ill patients for maintenance of intravascular volume and organ perfusion. Recent evidence regarding the vascular barrier and its role in terms of vascular leakage has led to a new concept for fluid administration. The choice of fluid used should be based on the fluid composition and the underlying pathophysiology of the patient. Avoidance of both hypo- and hypervolaemia is essential when treating circulatory failure. In daily practice, the assessment of individual thresholds in order to optimize cardiac preload and avoid hypovolaemia or deleterious fluid overload remains a challenge. Liberal versus restrictive fluid management has been challenged by recent evidence, and the ideal approach appears to be goal-directed fluid therapy.

Comparison of low molecular weight hydroxyethyl starch and human albumin as priming solutions in children undergoing cardiac surgery

Human albumin is the conventional cardiopulmonary bypass circuit primer. However, it has high manufacturing costs. Crystalloid and colloid solutions have been developed as alternatives, including a new generation of non-ionic hydroxyethyl starch (HES). The efficacy of hydroxyethyl starch with a 130 molecular weight and substitution degree of 0.4 (hydroxyethyl starch 130/0.4) was compared with human albumin for use in cardiopulmonary bypass surgery in American Society of Anesthesiologists’ grade I-II pediatric congenital heart disease patients. Efficacy was evaluated by comparing perioperative hemodynamic parameters, including plasma colloid osmotic pressure, renal function, blood loss, allogeneic blood volumes and plasma volume substitution. The hydroxyethyl starch group exhibited significantly higher preoperative colloid osmotic pressure (p <0.01) and significantly lower operative renal function and postoperative allogeneic blood volumes than the human albumin group. No significant differences were observed in serum creatinine, glucose, hematocrit or lactic acid levels (p>0.05). Our results indicate that hydroxyethyl starch may be a viable alternative to human albumin in pediatric patients undergoing relatively simple cardiopulmonary bypass surgeries.

A systematic review of goal directed fluid therapy: rating of evidence for goals and monitoring methods

PURPOSE

To review the literature on goal directed fluid therapy and evaluate the quality of evidence for each combination of goal and monitoring method.

MATERIALS AND METHODS

A search of major digital databases and hand search of references was conducted. All studies assessing the clinical utility of a specific fluid therapy goal or set of goals using any monitoring method were included. Data was extracted using a pre-determined pro forma and papers were evaluated using GRADE principles to assess evidence quality.

RESULTS

Eighty-one papers met the inclusion criteria, investigating 31 goals and 22 methods for monitoring fluid therapy in 13052 patients. In total there were 118 different goal/method combinations. Goals with high evidence quality were central venous lactate and stroke volume index. Goals with moderate quality evidence were sublingual microcirculation flow, the oxygen extraction ratio, cardiac index, cardiac output, and SVC collapsibility index.

CONCLUSIONS

This review has highlighted the plethora of goals and methods for monitoring fluid therapy. Strikingly, there is scant high quality evidence, in particular for non-invasive G/M combinations in non-operative and non-intensive care settings. There is an urgent need to address this research gap, which will be helped by methodologies to compare utility of G/M combinations.

In vitro effects of three formulations of hydroxyethyl starch solutions on coagulation and platelet function in horses

OBJECTIVE

To investigate the in vitro effects of 3 hydroxyethyl starch (HES) solutions on viscoelastic coagulation testing and platelet function in horses.

SAMPLE

Blood samples collected from 7 healthy adult horses.

PROCEDURES

Blood samples were diluted with various crystalloid and HES solutions to approximate the dilution of blood in vivo that occurs with administration of a 10 and 20 mL/kg fluid bolus to a horse (1:8 and 1:4 dilutions, respectively). Diluted samples were analyzed through optical platelet aggregometry, platelet function analysis, thromboelastography, and dynamic viscoelastic coagulometry. Colloid osmotic pressure and concentrations of von Willebrand factor and factor VIII:C were also determined for each sample.

RESULTS

For all HES products, at both dilutions, the colloid osmotic pressure was significantly higher than that in the respective carrier solutions. At the 1:4 dilution, nearly all HES solutions resulted in significant alterations in platelet function as measured via the platelet function analyzer and dynamic viscoelastic coagulometer. Significant decreases in platelet aggregation and factor concentrations were also evident. Fewer HES-associated changes were identified at the 1:8 dilutions.

CONCLUSIONS AND CLINICAL RELEVANCE

Dilution of blood samples with all HES solutions resulted in changes in viscoelastic coagulation and platelet function that did not appear to be attributable to dilution alone. In vivo evaluations are necessary to understand the clinical impact of these in vitro changes.

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.

The role of transesophageal echocardiography in the intraoperative period

The goal of hemodynamic monitoring and management during major surgery is to guarantee adequate organ perfusion, a major prerequisite for adequate tissue oxygenation and thus, end-organ function. Further, hemodynamic monitoring should serve to prevent, detect, and to effectively guide treatment of potentially life-threatening hemodynamic events, such as severe hypovolemia due to hemorrhage, or cardiac failure. The ideal monitoring device does not exist, but some conditions must be met: it should be easy and operator-independently to use; it should provide adequate, reproducible information in real time. In this review we discuss in particular the role of intraoperative use of transesophageal echocardiography (TOE). Although TOE has gained special relevance in cardiac surgery, its role in major non cardiac surgery is still to be determined. We particularly focus on its ability to provide measurements of cardiac output (CO), and its role to guide fluid therapy. Within the last decade, concepts oriented on optimizing stroke volume and cardiac output mainly by fluid administration and guided by continuous monitoring of cardiac output or so called functional parameters of cardiac preload gained particular attention. Although they are potentially linked to an increased amount of fluid infusion, recent data give evidence that such pre-emptive concepts of hemodynamic optimization result in a decrease in morbidity and mortality. As TOE allows a real time direct visualization of cardiac structures, other potentially important advantages of its use also outside the cardiac surgery operation room can be postulated, namely the ability to evaluate the anatomical and functional integrity of the left and the right heart chambers. Finally, a practical approach to TOE monitoring is presented, based on a local experience.

Goal-directed fluid therapy using stroke volume variation does not result in pulmonary fluid overload in thoracic surgery requiring one-lung ventilation

Background. Goal-directed fluid therapy (GDT) guided by functional parameters of preload, such as stroke volume variation (SVV), seems to optimize hemodynamics and possibly improves clinical outcome. However, this strategy is believed to be rather fluid aggressive, and, furthermore, during surgery requiring thoracotomy, the ability of SVV to predict volume responsiveness has raised some controversy. So far it is not known whether GDT is associated with pulmonary fluid overload and a deleterious reduction in pulmonary function in thoracic surgery requiring one-lung-ventilation (OLV). Therefore, we assessed the perioperative course of extravascular lung water index (EVLWI) and p_aO₂/F_iO₂-ratio during and after thoracic surgery requiring lateral thoracotomy and OLV to evaluate the hypothesis that fluid therapy guided by SVV results in pulmonary fluid overload. Methods. A total of 27 patients (group T) were enrolled in this prospective study with 11 patients undergoing lung surgery (group L) and 16 patients undergoing esophagectomy (group E). Goal-directed fluid management was guided by SVV (SVV < 10%). Measurements were performed directly after induction of anesthesia (baseline—BL), 15 minutes after implementation OLV (OLVimpl15), and 15 minutes after termination of OLV (OLVterm15). In addition, postoperative measurements were performed at 6 (6postop), 12 (12postop), and 24 (24postop) hours after surgery. EVLWI was measured at all predefined steps. The p_aO₂/F_iO₂-ratio was determined at each point during mechanical ventilation (group L: BL-OLVterm15; group E: BL-24postop). Results. In all patients (group T), there was no significant change (P > 0.05) in EVLWI during the observation period (BL: 7.8 ± 2.5, 24postop: 8.1 ± 2.4 mL/kg). A subgroup analysis for group L and group E also did not reveal significant changes of EVLWI. The p_aO₂/F_iO₂-ratio decreased significantly during the observation period (group L: BL: 462 ± 140, OLVterm15: 338 ± 112 mmHg; group E: BL: 389 ± 101, 24postop: 303 ± 74 mmHg) but remained >300 mmHg except during OLV. Conclusions. SVV-guided fluid management in thoracic surgery requiring lateral thoracotomy and one-lung ventilation does not result in pulmonary fluid overload. Although oxygenation was reduced, pulmonary function remained within a clinically acceptable range.

Pragmatic fluid optimization in high-risk surgery patients: when pragmatism dilutes the benefits

There is increasing evidence that hemodynamic optimization by fluid loading, particularly when performed in the early phase of surgery, is beneficial in high-risk surgery patients: it leads to a reduction in postoperative complications and even to improved long-term outcome. However, it is also true that goal- directed strategies of fluid optimization focusing on cardiac output optimization have not been applied in the clinical routine of many institutions. Reasons are manifold: disbelief in the level of evidence and on the accuracy and practicability of the required monitoring systems, and economics. The FOCCUS trial examined perioperative fluid optimization with a very basic approach: a standardized volume load with 25 ml/kg crystalloids over 6 hours immediately prior to scheduled surgery in high-risk patients. The hypothesis was that this intervention would lead to a compensation of preoperative fluid deficit caused by overnight fasting, and would result in improved perioperative fluid homeostasis with less postoperative complications and earlier hospital discharge. However, the primary study endpoints did not improve significantly. This observation points towards the facts that: firstly, the differentiation between interstitial fluid deficit caused by fasting and intravascular volume loss due to acute blood loss must be recognized in treatment strategies; secondly, the type of fluid replacement may play an important role; and thirdly, protocolized treatment strategies should also always be tailored to suit the patients' individual needs in every individual clinical situation.