Pulmonary artery catheter versus pulse contour analysis: a prospective epidemiological study

Perioperative Fluid Management and Volume Assessment

Fluid therapy is an integral component of perioperative care and helps maintain or restore effective circulating blood volume. The principal goal of fluid management is to optimize cardiac preload, maximize stroke volume, and maintain adequate organ perfusion. Accurate assessment of volume status and volume responsiveness is necessary for appropriate and judicious utilization of fluid therapy. To accomplish this, static and dynamic indicators of fluid responsiveness have been widely studied. This review discusses the overarching goals of perioperative fluid management, reviews the physiology and parameters used to assess fluid responsiveness, and provides evidence-based recommendations on intraoperative fluid management.

The microvascular endothelial glycocalyx: An additional piece of the puzzle in veterinary medicine

The endothelial glycocalyx (eGlx) is a critically important structure lining the luminal surface of endothelial cells. There is increasing evidence, in human patients and animal models, for its crucial role in the maintenance of health. Moreover, its damage is associated with the pathogenesis of multiple disease states. This review provides readers with an overview of the eGlx; summarising its structure, essential functions, and evidence for its role in disease. We highlight the lack of studies regarding the eGlx in cats and dogs, particularly in naturally occurring diseases. Importantly, we discuss techniques to aid its study, which can be applied to veterinary species. Finally, we present targeted therapies aimed at preserving, and in some cases, restoring damaged eGlx.

Intra-operative anaesthetic management of older patients undergoing liver surgery

Older patients represent a growing proportion of the general surgical caseload. This includes those undergoing liver resection, with figures rising faster than the rate of population ageing. The physiology of ageing leads to changes in all body systems which may render the provision of safe anaesthesia more challenging than in younger patients. Anaesthesia for liver surgery has specific principles, largely aimed at reducing venous bleeding from the liver, and those related to complex major surgery. This review explores the principles of anaesthesia for liver resection and describes how they may require modification in the older patient. The traditional approach of low central venous pressure anaesthesia in order to reduce bleeding may need to be altered in the presence of a cardiovascular system less able to tolerate hypotension and hypoperfusion. These changes in physiology should also lower the threshold for invasive monitoring. The provision of effective analgesia perioperatively should be tailored to minimise the surgical stress response and opiate use. Careful consideration of general principles of intra-operative care for older patients, such as positioning, drug dosing, avoidance of excessively deep anaesthesia, and maintenance of normothermia are also important given the prolonged, complex nature of liver surgery. This individualised approach, with careful attention to changes in physiology allows liver resections to be undertaken in older patients without increases in mortality.

Fluid Status After Cardiac Surgery Assessed by Bioelectrical Impedance Vector Analysis and the Effects of Extracorporeal Circulation

OBJECTIVE

Hydration status after cardiac surgery can be difficult to assess, often requiring invasive measurements. Bioelectrical impedance vector analysis (BIVA) is based on patterns of resistance (R) and reactance (Xc), corrected by height, and has been used in various clinical scenarios to determine body composition and monitor its changes over time. The purpose of the present study was to apply this method in cardiac surgery patients to assess the variation in hydration status and to compare its changes according to the use of extracorporeal circulation.

DESIGN

Single-center, observational, prospective study including patients older than 18 years undergoing elective or urgent cardiac surgery.

SETTING

Intensive cardiac care unit of a tertiary center in a metropolitan area.

PARTICIPANTS

The study comprised 76 patients with a median age of 60 years and mostly undergoing coronary artery bypass grafting (CABG) (n = 47 [61.8%]) with extracorporeal circulation (n = 54 [73%]).

INTERVENTIONS

Bioimpedance was measured with a standard tetrapolar single-frequency bioimpedance meter using a standardized procedure and plotted in an R-Xc graph.

MEASUREMENTS AND MAIN RESULTS

The study demonstrated an increase in total body water immediately after surgery that was sustained until producing hyperhydration 24 hours later. Off-pump CABG was associated with a normal hydration status after surgery, whereas on-pump CABG produced a significant increase in total body water.

CONCLUSIONS

Fluid status assessment with BIVA in cardiac surgery showed an increase in total body water up to 24 hours after surgery. Off-pump surgery prevented overhydration, which partially could explain the reduction in some of the postoperative complications. BIVA could serve as a useful method for monitoring fluid status in the setting of goal-directed therapy to assist in maintaining euvolemia in cardiac surgical patients.

Heart Dysfunction in Sepsis

Cardiac involvement during sepsis frequently occurs. A series of molecules induces a set of changes at the cellular level that result in the malfunction of the myocardium. The understanding of these molecular alterations has simultaneously promoted the implementation of diagnostic strategies that are much more precise and allowed the advance of the therapeutics. The heart is a vital organ for survival. Its well-being ensures the adequate supply of essential elements for organs and tissues.

Risk factors for noninvasive ventilation failure in patients with acute cardiogenic pulmonary edema: A prospective, observational cohort study

PURPOSE

We identified risk factors for noninvasive ventilation (NIV) failure in patients with acute cardiogenic pulmonary edema (ACPE).

MATERIALS AND METHODS

We conducted an observational cohort study over a 3-year period in a 28-bed emergency intensive care unit (EICU) and prospectively included all consecutive patients in whom NIV was attempted as initial ventilatory support for ACPE. The primary outcome variables were NIV failure rate and risk factors for NIV failure.

RESULTS

Among the 118 patients in the study, NIV failed for 44 (37.3%) patients. Risk factors for NIV failure were Killip class IV (odds ratio [OR], 28.56; 95% confidence interval [CI], 2.17-375.73; p=0.011), left ventricular ejection fraction (LVEF) <30% (OR, 9.54; 95% CI, 1.01-90.55; p=0.050) and B-type natriuretic peptide (BNP) ≥3350pg/mL (OR, 39.63; 95% CI, 3.92-400.79; p=0.002) at baseline, and fluid balance ≥400mL within 24h after ACPE (OR, 13.19; 95% CI, 1.18-147.70; p=0.036).

CONCLUSIONS

NIV failure occurred in 37.3% of ACPE patients in a real-world EICU. When patients had Killip class IV, a lower LVEF, a higher BNP, and a more positive fluid balance within 24h after ACPE, the risk of failure was higher. TRIAL REGISTRATION CLINICALTRIALS.

GOV IDENTIFIER

NCT02653365.

A retrospective review of fluid balance control in CRRT

INTRODUCTION

An effect of severe acute kidney injury (AKI) is the development of oliguria and subsequent retention of fluid. Recent studies have reported an association between fluid overload and increased mortality in critically ill patients. Achieving fluid balance control through haemofiltration is an important part of dialysis dose delivery in continuous renal replacement therapy (CRRT).

AIMS

(1) Compare the prescribed dose with the delivered dose of dialysis and haemofiltration for CRRT. (2) Identify how interruptions and delays in treatment delivery impact on fluid balance management.

METHOD

A retrospective cohort study was undertaken of daily fluid balance and fluid removal for patients who required CRRT. Each observation chart and prescription order for every treatment day was reviewed. Each patient was exposed to the same treatment mode, predilutional continuous veno-venous haemodiafiltration (CVVHDf). A comparison was made of fluid balance control delivered to the patient over 24h against the dose of fluid removal prescribed.

RESULTS

The observation charts of 46 consecutive patients were reviewed for total of 288 treatment days. Median number of days patients received CRRT was 5 (range 1-31). Median circuit life was 16h (range 0-66). Fluid removal targets did not occur in 75 (26%) treatment days. Median daily fluid removal shortfall was 300mL (range 25-3800mL). Mean number of daily treatment interruptions 1.25, SD±0.49. The most frequent cause of treatment downtime was circuit clotting (45%). Mean length of treatment down time was 3.71, SD±4.36h excluding delays attributed to assessment of renal function.

CONCLUSION

In over a quarter of treatment days prescribed fluid removal was not achieved. Frequency of interruptions and delays in resumption of treatment compromised fluid balance control. Daily targets for fluid removal which are not achieved contribute to fluid overload and may compromise the outcome of patients who require CRRT.

Hemodynamic assessment in the contemporary intensive care unit: a review of circulatory monitoring devices

The assessment of the circulating volume and efficiency of tissue perfusion is necessary in the management of critically ill patients. The controversy surrounding pulmonary artery catheterization has led to a new wave of minimally invasive hemodynamic monitoring technologies, including echocardiographic and Doppler imaging, pulse wave analysis, and bioimpedance. This article reviews the principles, advantages, and limitations of these technologies and the clinical contexts in which they may be clinically useful.

The fluid management of adults with severe malaria

Fluid resuscitation has long been considered a key intervention in the treatment of adults with severe falciparum malaria. Profound hypovolemia is common in these patients and has the potential to exacerbate the acidosis and acute kidney injury that are independent predictors of death. However, new microvascular imaging techniques have shown that disease severity correlates more strongly with obstruction of the microcirculation by parasitized erythrocytes - a process termed sequestration. Fluid loading has little effect on sequestration and increases the risk of complications, particularly pulmonary edema, a condition that can develop suddenly and unpredictably and that is frequently fatal in this population. Accordingly, even if a patient is clinically hypovolemic, if there is an adequate blood pressure and urine output, there may be little advantage in infusing intravenous fluid beyond a maintenance rate of 1 to 2 mL/kg per hour. The optimal agent for fluid resuscitation remains uncertain; significant anemia requires blood transfusion, but colloid solutions may be associated with harm and should be avoided. The preferred crystalloid is unclear, although the use of balanced solutions requires investigation. There are fewer data to guide the fluid management of severe vivax and knowlesi malaria, although a similar conservative strategy would appear prudent.

Passive leg raising as an indicator of fluid responsiveness in patients with severe sepsis

BACKGROUND

In the management of critically ill patients, the assessment of volume responsiveness and the decision to administer a fluid bolus constitute a common dilemma for physicians. Static indices of cardiac preload are poor predictors of volume responsiveness. Passive leg raising (PLR) mimics an endogenous volume expansion (VE) that can be used to predict fluid responsiveness. This study was to assess the changes in stroke volume index (SVI) induced by PLR as an indicator of fluid responsiveness in mechanically ventilated patients with severe sepsis.

METHODS

This was a prospective study. Thirty-two mechanically ventilated patients with severe sepsis were admitted for VE in ICU of the First Affiliated Hospital, Zhejiang University School of Medicine and Ningbo Medical Treatment Center Lihuili Hospital from May 2010 to December 2011. Patients with non-sinus rhythm or arrhythmia, parturients, and amputation of the lower limbs were excluded. Measurements of SVI were obtained in a semi-recumbent position (baseline) and during PLR by the technique of pulse indicator continuous cardiac output (PiCCO) system prior to VE. Measurements were repeated after VE (500 mL 6% hydroxyethyl starch infusion within 30 minutes) to classify patients as either volume responders or non-responders based on their changes in stroke volume index (ΔSVI) over 15%. Heart rate (HR), systolic artery blood pressure (ABPs), diastolic artery blood pressure (ABPd), mean arterial blood pressure (ABPm), mean central venous pressure (CVPm) and cardiac index (CI) were compared between the two groups. The changes of ABPs, ABPm, CVPm, and SVI after PLR and VE were compared with the indices at the baseline. The ROC curve was drawn to evaluate the value of ΔSVI and the change of CVPm (ΔCVPm) in predicting volume responsiveness. SPSS 17.0 software was used for statistical analysis.

RESULTS

Among the 32 patients, 22 were responders and 10 were non-responders. After PLR among the responders, some hemodynamic variables (including ABPs, ABPd, ABPm and CVPm) were significantly elevated (101.2±17.6 vs.118.6±23.7, P=0.03; 52.8±10.7 vs. 64.8±10.7, P=0.006; 68.3±11.7 vs. 81.9±14.4, P=0.008; 6.8±3.2 vs. 11.9±4.0, P=0.001). After PLR, the area under curve (AUC) and the ROC curve of ΔSVI and ΔCVPm for predicting the responsiveness after VE were 0.882±0.061 (95%CI 0.759-1.000) and 0.805±0.079 (95%CI 0.650-0.959) when the cut-off levels of ΔSVI and ΔCVPm were 8.8% and 12.7%, the sensitivities were 72.7% and 72.7%, and the specificities were 80% and 80%.

CONCLUSION

Changes in ΔSVI and ΔCVPm induced by PLR are accurate indices for predicting fluid responsiveness in mechanically ventilated patients with severe sepsis.

Usefulness of the endotoxin activity assay to evaluate the degree of lung injury

PURPOSE

It has been reported that the Pulse Contour Cardiac Output (PiCCO) is very useful mainly in the field of intensive care and treatment to grasp the pathophysiological conditions of pulmonary edema because of its capability of obtaining data such as Pulmonary Vascular Permeability Index (PVPI) and Extra Vascular Lung Water (EVLW). Furthermore, a high degree of usability of various markers has been reported for better understanding of the pathological conditions in cases with septicemia.

MATERIALS AND METHODS

The correlation between the cardiorespiratory status based upon the PiCCO monitor (EVLW and PVPI) and inflammatory markers including C reactive protein, procalcitonin (PC), and Endotoxin Activity Assay (EAA) were evaluated in 11 severe cases that required treatment with a respirator in an intensive care unit.

RESULTS

The EAA values were significantly higher in patients with abnormal EVLW at 0.46±0.20 compared to the normal EVLW group at 0.21±0.19 (p=0.0064). In a similar fashion, patients with abnormal PVPI values tended to have higher PC levels at 18.9±21.8 compared to normal PVPI cases at 2.4±2.2 (p=0.0676). On the other hand, PVPI was significantly higher in the abnormal EAA group at 3.55±0.48 in comparison with the normal EAA group at 1.99±0.68 (p=0.0029). The abnormal EAA group tended to have higher PVPI values than the normal EAA group.

CONCLUSION

The EAA is a measurement method designed to estimate the activity of endotoxins in the whole blood. Our results suggest that the EAA value, which had the greatest correlation with lung disorders diagnosed by the PiCCO monitoring, reflects inflammatory reactions predominantly in the lungs.

Fluid resuscitation of adults with severe falciparum malaria: effects on Acid-base status, renal function, and extravascular lung water

OBJECTIVE

To evaluate the efficacy and safety of liberal fluid resuscitation of adults with severe malaria. DESIGN, SETTING, PATIENTS, AND METHODS: Twenty-eight Bangladeshi and Indian adults with severe falciparum malaria received crystalloid resuscitation guided by transpulmonary thermodilution (PiCCO) in an intensive care setting. Systemic hemodynamics, microvascular indices and measures of acidosis, renal function, and pulmonary edema were followed prospectively.

RESULTS

All patients were hypovolemic (global end-diastolic volume index<680 mL/m) on enrollment. Patients received a median (range) 3230 mL (390-7300) of isotonic saline in the first 6 hours and 5450 mL (710-13,720) in the first 24 hours. With resuscitation, acid-base status deteriorated in 19 of 28 (68%), and there was no significant improvement in renal function. Extravascular lung water increased in 17 of 22 liberally resuscitated patients (77%); eight of these patients developed pulmonary edema, five of whom died. All other patients survived. All patients with pulmonary edema during the study were hypovolemic or euvolemic at the time pulmonary edema developed. Plasma lactate was lower in hypovolemic patients before (rs=0.38; p=0.05) and after (rs=0.49; p=0.01) resuscitation but was the strongest predictor of mortality before (chi-square=9.9; p=0.002) and after resuscitation (chi-square=11.1; p<0.001) and correlated with the degree of visualized microvascular sequestration of parasitized erythrocytes at both time points (rs=0.55; p=0.003 and rs=0.43; p=0.03, respectively). Persisting sequestration was evident in 7 of 15 patients (47%) 48 hours after enrollment.

CONCLUSIONS

Lactic acidosis--the strongest prognostic indicator in adults with severe falciparum malaria--results from sequestration of parasitized erythrocytes in the microcirculation, not from hypovolemia. Liberal fluid resuscitation has little effect on this sequestration and does not improve acid-base status or renal function. Pulmonary edema--secondary to increased pulmonary vascular permeability--is common, unpredictable, and exacerbated by fluid loading. Liberal fluid replacement of adults with severe malaria should be avoided.

Individualizing hemodynamic optimization during the management of circulatory collapse

The best method of hemodynamic monitoring to guide the resuscitation and management of the critically ill patient is unclear. The evaluated article presents data from a prospective randomized controlled trial that recruited 120 shocked patients (n = 60 in each arm) to compare volume-limited versus pressure-limited hemodynamic management. Patients were randomized into two protocolized fluid therapy algorithms using either the upper limits of hemodynamic indices of arterial pulse contour cardiac output and transpulmonary thermodilution (TPTD) analysis (extra vascular lung water <10 ml/kg and global end-diastolic volume index 850 ml/m(2)) or pulmonary artery catheter pressures (<18-20 mmHg). Primary outcomes were ventilator-free days, duration of mechanical ventilation, intensive care unit and hospital stay. Secondary outcomes included sequential organ failure assessment scores and mortality. No benefit was found between pulmonary artery catheter and TPTD in the primary outcomes; interestingly, the nonseptic patients who were monitored with TPTD spent longer on mechanical ventilation and in the intensive care unit.

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.

Volume management in the critically ill patient with acute kidney injury

Acute kidney injury (AKI) frequently occurs in the setting of critical illness and its management poses a challenge for the intensivist. Optimal management of volume status is critical in the setting of AKI in the ICU patient. The use of urine sodium, the fractional excretion of sodium (FeNa), and the fractional excretion of urea (FeUrea) are common clinical tools used to help guide fluid management especially further volume expansion but should be used in the context of the patient's overall clinical scenario as they are not completely sensitive or specific for the finding of volume depletion and can be misleading. In the case of oliguric or anuric AKI, diuretics are often utilized to increase the urine output although current evidence suggests that they are best reserved for the treatment of volume overload and hyperkalemia in patients who are likely to respond to them. Management of volume overload in ICU patients with AKI is especially important as volume overload has several negative effects on organ function and overall morbidity and mortality.

Increasing mean arterial blood pressure in sepsis: effects on fluid balance, vasopressor load and renal function

Introduction

The objective of this study was to evaluate the effects of two different mean arterial blood pressure (MAP) targets on needs for resuscitation, organ dysfunction, mitochondrial respiration and inflammatory response in a long-term model of fecal peritonitis.

Methods

Twenty-four anesthetized and mechanically ventilated pigs were randomly assigned (n = 8/group) to a septic control group (septic-CG) without resuscitation until death or one of two groups with resuscitation performed after 12 hours of untreated sepsis for 48 hours, targeting MAP 50-60 mmHg (low-MAP) or 75-85 mmHg (high-MAP).

Results

MAP at the end of resuscitation was 56 ± 13 mmHg (mean ± SD) and 76 ± 17 mmHg respectively, for low-MAP and high-MAP groups. One animal each in high- and low-MAP groups, and all animals in septic-CG died (median survival time: 21.8 hours, inter-quartile range: 16.3-27.5 hours). Norepinephrine was administered to all animals of the high-MAP group (0.38 (0.21-0.56) mcg/kg/min), and to three animals of the low-MAP group (0.00 (0.00-0.25) mcg/kg/min; P = 0.009). The high-MAP group had a more positive fluid balance (3.3 ± 1.0 mL/kg/h vs. 2.3 ± 0.7 mL/kg/h; P = 0.001). Inflammatory markers, skeletal muscle ATP content and hemodynamics other than MAP did not differ between low- and high-MAP groups. The incidence of acute kidney injury (AKI) after 12 hours of untreated sepsis was, respectively for low- and high-MAP groups, 50% (4/8) and 38% (3/8), and in the end of the study 57% (4/7) and 0% (P = 0.026). In septic-CG, maximal isolated skeletal muscle mitochondrial Complex I, State 3 respiration increased from 1357 ± 149 pmol/s/mg to 1822 ± 385 pmol/s/mg, (P = 0.020). In high- and low-MAP groups, permeabilized skeletal muscle fibers Complex IV-state 3 respiration increased during resuscitation (P = 0.003).

Conclusions

The MAP targets during resuscitation did not alter the inflammatory response, nor affected skeletal muscle ATP content and mitochondrial respiration. While targeting a lower MAP was associated with increased incidence of AKI, targeting a higher MAP resulted in increased net positive fluid balance and vasopressor load during resuscitation. The long-term effects of different MAP targets need to be evaluated in further studies.

Fluid balance and urine volume are independent predictors of mortality in acute kidney injury

Introduction

In ICUs, both fluid overload and oliguria are common complications associated with increased mortality among critically ill patients, particularly in acute kidney injury (AKI). Although fluid overload is an expected complication of oliguria, it remains unclear whether their effects on mortality are independent of each other. The aim of this study is to evaluate the impact of both fluid balance and urine volume on outcomes and determine whether they behave as independent predictors of mortality in adult ICU patients with AKI.

Methods

We performed a secondary analysis of data from a multicenter, prospective cohort study in 10 Italian ICUs. AKI was defined by renal sequential organ failure assessment (SOFA) score (creatinine >3.5 mg/dL or urine output (UO) <500 mL/d). Oliguria was defined as a UO <500 mL/d. Mean fluid balance (MFB) and mean urine volume (MUV) were calculated as the arithmetic mean of all daily values. Use of diuretics was noted daily. To assess the impact of MFB and MUV on mortality of AKI patients, multivariate analysis was performed by Cox regression.

Results

Of the 601 included patients, 132 had AKI during their ICU stay and the mortality in this group was 50%. Non-surviving AKI patients had higher MFB (1.31 ± 1.24 versus 0.17 ± 0.72 L/day; P <0.001) and lower MUV (1.28 ± 0.90 versus 2.35 ± 0.98 L/day; P <0.001) as compared to survivors. In the multivariate analysis, MFB (adjusted hazard ratio (HR) 1.67 per L/day, 95%CI 1.33 to 2.09; <0.001) and MUV (adjusted HR 0.47 per L/day, 95%CI 0.33 to 0.67; <0.001) remained independent risk factors for 28-day mortality after adjustment for age, gender, diabetes, hypertension, diuretic use, non-renal SOFA and sepsis. Diuretic use was associated with better survival in this population (adjusted HR 0.25, 95%CI 0.12 to 0.52; <0.001).

Conclusions

In this multicenter ICU study, a higher fluid balance and a lower urine volume were both important factors associated with 28-day mortality of AKI patients.

Critical care of the potential organ donor

Organ transplantation represents one of the great success stories of 20th century medicine. However, its continued success is greatly limited by the shortage of donor organs. This has led to an increased focus within the critical care community on optimal identification and management of the potential organ donor. The multi-organ donor can represent one of the most complex intensive care patients, with numerous competing physiological priorities. However, appropriate management of the donor not only increases the number of organs that can be successfully donated but has long-term implications for the outcomes of multiple recipients. This review outlines current understandings of the physiological derangements seen in the organ donor and evaluates the available evidence for management strategies designed to optimize donation potential and organ recovery. Finally, emerging management strategies for the potential donor are discussed within the current ethical and legal frameworks permitting donation after both brain and circulatory death.

Evaluation of arterial waveform derived variables for an assessment of volume resuscitation in mechanically ventilated burn patients

OBJECTIVE

The purpose of this study was to assess the usefulness of stroke volume variations to monitor the early fluid resuscitation in mechanically ventilated burn ICU patients.

METHODS AND RESULTS

Data of 29 burn patients (APACHE II - 9.8±3.6, SAPS II - 29±5, TBSA - 39.5±14) were prospectively included in this observational study. Hemodynamic parameters were determined using arterial pressure wave analysis for up to 36h after burn. Statistically significant changes in cardiac index (CI), systemic vascular resistance index (SVRI), stroke volume variation (SVV) were recorded during the observation period. There were significant correlations between CI and SVV (r=-0.454, p=0.03), SVV and SVRI (r=0.482, p=0.02) at 16 h postburn; CI and SVV (r=-0.513, p=0.012), SVV and SVRI (r=0.480, p=0.02) at 24 h postburn, CI and SVV at 36 h postburn (r=-0.478, p=0.021). Significant changes in CI (1.9±1 vs. 3.4±0.9), p=0.02 and in SVV (24.9±3 vs. 14.6±2, p=0.01) were observed in patients with low cardiac output state after administration of 10 ml/kg of Ringer lactate.

CONCLUSION

Our results suggest that measurement of stroke volume variations by arterial pulse contour analysis is valuable in monitoring volume administration and in predicting volume responsiveness during the early postburn period.

Volume-limited versus pressure-limited hemodynamic management in septic and nonseptic shock

OBJECTIVES

To evaluate the effect of hemodynamic management guided by upper limits of cardiac filling volumes or pressures on durations of mechanical ventilation and lengths of stay in critically ill patients with shock.

DESIGN

Prospective, randomized, clinical trial.

SETTING

Mixed intensive care unit of a large teaching hospital and mixed intensive care unit of a tertiary care, academic medical center.

PATIENTS

A total 120 septic (n = 72) and nonseptic (n = 48) shock patients, randomized (after stratification) to transpulmonary thermodilution (n = 60) or pulmonary artery catheter (n = 60) between February 2007 and July 2009.

INTERVENTIONS

Hemodynamic management was guided by algorithms including upper limits for fluid resuscitation of extravascular lung water (<10 mL/kg) and global end-diastolic volume index (<850 mL/m) in the transpulmonary thermodilution group and pulmonary artery occlusion pressure (<18-20 mm Hg) in the pulmonary artery catheter group for 72 hrs after enrollment.

MEASUREMENTS AND MAIN RESULTS

Primary outcomes were ventilator-free days and lengths of stay in the intensive care unit and the hospital. Secondary outcomes included organ failures and mortality. Cardiac comorbidity was more frequent in nonseptic than in septic shock. Ventilator-free days, lengths of stay, organ failures, and 28-day mortality (overall 33.3%) were similar between monitoring groups. Transpulmonary thermodilution (vs. pulmonary artery catheter) monitoring was associated with more days on mechanical ventilation and longer intensive care unit and hospital lengths of stay in nonseptic (p = .001) but not in septic shock. In both conditions, fewer patients met the upper limit of volume than of pressure criteria at baseline and transpulmonary thermodilution (vs. pulmonary artery catheter) monitoring was associated with a more positive fluid balance at 24 hrs.

CONCLUSIONS

Hemodynamic management guided by transpulmonary thermodilution vs. pulmonary artery catheter in shock did not affect ventilator-free days, lengths of stay, organ failures, and mortality of critically ill patients. Use of the a transpulmonary thermodilution algorithm resulted in more days on mechanical ventilation and intensive care unit length of stay compared with the pulmonary artery catheter algorithm in nonseptic shock but not in septic shock. This may relate to cardiac comorbidity and a more positive fluid balance with use of transpulmonary thermodilution in nonseptic shock.

The PiCCO Monitor: A Review

Advanced haemodynamic monitoring remains a cornerstone in the management of the critically ill. While rates of pulmonary artery catheter use have been declining, there has been an increase in the number of alternatives for monitoring cardiac output as well as greater understanding of the methods and criteria with which to compare devices. The PiCCO (Pulse index Continuous Cardiac Output) device is one such alternative, integrating a wide array of both static and dynamic haemodynamic data through a combination of trans-cardiopulmonary thermodilution and pulse contour analysis. The requirement for intra-arterial and central venous catheterisation limits the use of PiCCO to those with evolving critical illness or at high risk of complex and severe haemodynamic derangement. While the accuracy of trans-cardiopulmonary thermodilution as a measure of cardiac output is well established, several other PiCCO measurements require further validation within the context of their intended clinical use. As with all advanced haemodynamic monitoring systems, efficacy in improving patient-centred outcomes has yet to be conclusively demonstrated. The challenge with PiCCO is in improving the understanding of the many variables that can be measured and integrating those that are clinically relevant and adequately validated with appropriate therapeutic interventions.

Comparison of goal-directed hemodynamic optimization using pulmonary artery catheter and transpulmonary thermodilution in combined valve repair: a randomized clinical trial

Our aim was to compare the effects of goal-directed therapy guided either by pulmonary artery catheter (PAC) or by transpulmonary thermodilution (TTD) combined with monitoring of oxygen transport on perioperative hemodynamics and outcome after complex elective valve surgery. Measurements and Main Results. Forty patients were randomized into two equal groups: a PAC group and a TTD group. In the PAC group, therapy was guided by mean arterial pressure (MAP), cardiac index (CI) and pulmonary artery occlusion pressure (PAOP), whereas in the TTD group we additionally used global end-diastolic volume index (GEDVI), extravascular lung water index (EVLWI), and oxygen delivery index (DO₂I). We observed a gradual increase in GEDVI, whereas EVLWI and PAOP decreased by 20–30% postoperatively (P < 0.05). The TTD group received 20% more fluid accompanied by increased stroke volume index and DO₂I by 15–20% compared to the PAC group (P < 0.05). Duration of mechanical ventilation was increased by 5.2 hrs in the PAC group (P = 0.04). Conclusions. As compared to the PAC-guided algorithm, goal-directed therapy based on transpulmonary thermodilution and oxygen transport increases the volume of fluid therapy, improves hemodynamics and DO₂I, and reduces the duration of respiratory support after complex valve surgery.

Applications of minimally invasive cardiac output monitors

Because of the increasing age of the population, critical care and emergency medicine physicians have seen an increased number of critically ill patients over the last decade. Moreover, the trend of hospital closures in the United States t imposes a burden of increased efficiency. Hence, the identification of devices that facilitate accurate but rapid assessments of hemodynamic parameters without the added burden of invasiveness becomes tantamount. The purpose of this review is to understand the applications and limitations of these new technologies.

Estimation of fluid status changes in critically ill patients: fluid balance chart or electronic bed weight?

PURPOSE

Monitoring of fluid balance (FB) can be achieved by subtracting recorded fluid output from input or by measuring changes in body weight (BW). The latter approach is difficult in the critically ill. Recently, hospital beds have become available with the ability to directly weigh patients in the intensive care unit (ICU) patients directly. We sought to compare FB estimates obtained by these 2 methods in a cohort of critically ill patients.

MATERIALS AND METHODS

Between November 2010 and May 2011, all patients admitted in our ICU for more than 2 consecutive days and nursed on a Hill-Rom (Batesville, Ind) Total Care bed were weighed daily at midnight hours. Fluids charting was done by electronic spreadsheet with automated 24 hours calculation. Differences in BW and FB between 2 consecutive days were compared using correlation and Bland-Altman analysis. Corrections for unmeasured fluids losses were performed using a predetermined formula based on peak temperature and intubation status.

RESULTS

We obtained complete data in 160 (31%) of 504 admissions exceeding 2 days (153 patients) resulting in 435 data points. The change in BW over 24 hours and FB for the same period was only weakly correlated before (r = 0.34; P < .001; Fig. 1) or after correction for insensible fluid losses (r = 0.34; P < .001). On Bland-Altman plot, the mean bias was small (0.07 kg), but the 95% limits of agreement, very large (-5.8 and 6.0 kg). The lack of agreement increased with the magnitude of the changes.

CONCLUSION

Obtaining daily weights in ICU patients proved difficult. Compliance was poor. The correlation between changes in BWs and FB was weak. Further studies are required to establish if accurate and reproducible daily weighing of ICU patients is feasible.

Central venous catheter use in severe malaria: time to reconsider the World Health Organization guidelines?

BACKGROUND

To optimize the fluid status of adult patients with severe malaria, World Health Organization (WHO) guidelines recommend the insertion of a central venous catheter (CVC) and a target central venous pressure (CVP) of 0-5 cmH2O. However there are few data from clinical trials to support this recommendation.

METHODS

Twenty-eight adult Indian and Bangladeshi patients admitted to the intensive care unit with severe falciparum malaria were enrolled in the study. All patients had a CVC inserted and had regular CVP measurements recorded. The CVP measurements were compared with markers of disease severity, clinical endpoints and volumetric measures derived from transpulmonary thermodilution.

RESULTS

There was no correlation between the admission CVP and patient outcome (p = 0.67) or disease severity (p = 0.33). There was no correlation between the baseline CVP and the concomitant extravascular lung water (p = 0.62), global end diastolic volume (p = 0.88) or cardiac index (p = 0.44). There was no correlation between the baseline CVP and the likelihood of a patient being fluid responsive (p = 0.37). On the occasions when the CVP was in the WHO target range patients were usually hypovolaemic and often had pulmonary oedema by volumetric measures. Seven of 28 patients suffered a complication of the CVC insertion, although none were fatal.

CONCLUSION

The WHO recommendation for the routine insertion of a CVC, and the maintenance of a CVP of 0-5 cmH2O in adults with severe malaria, should be reconsidered.

Emerging technologies

Hemodynamic monitoring in critically ill patients has been considered part of the standard of care in managing patients with shock and/or acute lung injury, but outcome benefit, particularly in pediatric patients, has been questioned. There is difficulty in validating the reliability of monitoring devices, especially since this validation requires comparison to the pulmonary artery catheter, which has its own problems as a measurement tool. Interpretation of the available evidence reveals advantages and disadvantages of the available hemodynamic monitoring devices.

Early non-invasive cardiac output monitoring in hemodynamically unstable intensive care patients: a multi-center randomized controlled trial

INTRODUCTION

Acute hemodynamic instability increases morbidity and mortality. We investigated whether early non-invasive cardiac output monitoring enhances hemodynamic stabilization and improves outcome.

METHODS

A multicenter, randomized controlled trial was conducted in three European university hospital intensive care units in 2006 and 2007. A total of 388 hemodynamically unstable patients identified during their first six hours in the intensive care unit (ICU) were randomized to receive either non-invasive cardiac output monitoring for 24 hrs (minimally invasive cardiac output/MICO group; n = 201) or usual care (control group; n = 187). The main outcome measure was the proportion of patients achieving hemodynamic stability within six hours of starting the study.

RESULTS

The number of hemodynamic instability criteria at baseline (MICO group mean 2.0 (SD 1.0), control group 1.8 (1.0); P = .06) and severity of illness (SAPS II score; MICO group 48 (18), control group 48 (15); P = .86)) were similar. At 6 hrs, 45 patients (22%) in the MICO group and 52 patients (28%) in the control group were hemodynamically stable (mean difference 5%; 95% confidence interval of the difference -3 to 14%; P = .24). Hemodynamic support with fluids and vasoactive drugs, and pulmonary artery catheter use (MICO group: 19%, control group: 26%; P = .11) were similar in the two groups. The median length of ICU stay was 2.0 (interquartile range 1.2 to 4.6) days in the MICO group and 2.5 (1.1 to 5.0) days in the control group (P = .38). The hospital mortality was 26% in the MICO group and 21% in the control group (P = .34).

CONCLUSIONS

Minimally-invasive cardiac output monitoring added to usual care does not facilitate early hemodynamic stabilization in the ICU, nor does it alter the hemodynamic support or outcome. Our results emphasize the need to evaluate technologies used to measure stroke volume and cardiac output--especially their impact on the process of care--before any large-scale outcome studies are attempted.

TRIAL REGISTRATION

The study was registered at ClinicalTrials.gov (Clinical Trials identifier NCT00354211).

Volume-related weight gain and subsequent mortality in acute renal failure patients treated with continuous renal replacement therapy

Fluid overload is a frequent finding in critically ill patients suffering from acute kidney injury (AKI). To assess the impact of fluid overload on the mortality of AKI patients treated with continuous renal replacement therapy (CRRT), we used a registry of 81 critically ill patients with AKI initiated on CRRT assembled over an 18-month period to conduct a cross- sectional analysis using volume-related weight gain (VRWG) of > or =10% and > or =20% of body weight and oliguria (< or =20 ml/h) as the principal variables, with the primary outcome measure being mortality at 30 days. Mean Apache II scores were 27.5 +/- 6.9 with overall cohort mortality of 50.6%. Mean (+/-SD) VRWG was 8.3 +/- 9.6 kg, representing a 10.2% +/- 13.5% increase since admission. Oliguria was present in 65.4% of patients. Odds ratio (OR) for mortality on univariate analysis was increased to 2.62 [95% confidence interval (CI): 1.07-6.44] by a VRWG > or =10% and to 3.22 (95% CI: 1.23-8.45) by oliguria. VRWG > or =20% had OR of 3.98 (95% CI: 1.01-15.75; p = 0.049) for mortality. Both VRWG > or =10% (OR 2.71, p = 0.040) and oliguria (OR 3.04, p = 0.032) maintained their statistically significant association with mortality in multivariate models that included sepsis and Apache II score. In conclusion, fluid overload is an important prognostic factor for survival in critically ill AKI patients treated with CRRT. Further studies are needed to elicit mechanisms and develop appropriate interventions.

Choosing patient-tailored hemodynamic monitoring

This article is one of ten reviews selected from the Yearbook of Intensive Care and Emergency Medicine 2010 (Springer Verlag) and co-published as a series in Critical Care. Other articles in the series can be found online at http://ccforum.com/series/yearbook. Further information about the Yearbook of Intensive Care and Emergency Medicine is available from http://www.springer.com/series/2855.

Cardiac output derived from arterial pressure waveform

PURPOSE OF REVIEW

Cardiac output (CO) and other flow-based hemodynamic variables have become increasingly important to guide treatment of patients undergoing major surgery with expected fluid shifts in the operating room as well as critically ill ICU patients. Established techniques such as pulmonary artery thermodilution, however, might not be justified in all of these patients. As arterial access is commonly available, less-invasive arterial pressure waveform-based CO devices are becoming more and more popular.

RECENT FINDINGS

Many studies dealing with arterial pressure waveform-based CO have emerged in recent years providing additional information with regard to accuracy of the different commercially available devices. Furthermore, methods of comparative CO studies have been recently brought into question.

SUMMARY

Although there are differences in invasiveness and the need for external calibration, all available devices provide parameters for enhanced hemodynamic monitoring. Initial validation studies of the more established techniques such as the pulse contour cardiac output (PiCCO) or LiDCO were recently met with less enthusiasm, whereas the initially disappointing validation studies of the FloTrac/Vigileo device had encouraging results after software updates. The pressure recording analytical method (PRAM) technique has not so far been sufficiently evaluated to be able to come to a conclusion. Further investigation is required with regard to the ability of the arterial pressure waveform-based methods to guide goal-directed therapy.

Emerging trends in minimally invasive haemodynamic monitoring and optimization of fluid therapy

BACKGROUND

For decades the pulmonary artery catheter has been the mainstay of cardiac output monitoring in critically ill patients, and pressure-based indices of ventricular filling have been used to gauge fluid requirements with acknowledged limitations. In recent years, alternative technologies have become available which are minimally invasive, allow beat-to-beat cardiac output monitoring and permit assessment of fluid requirements by volumetric means and by allowing assessment of heart-lung interaction in mechanically ventilated patients.

METHODS

A qualitative review of the basic science behind the transpulmonary dilution technique used in the measurement of cardiac output, global end-diastolic volume and extravascular lung water; the basic science and validation of pulse contour analysis methods of real-time cardiac output monitoring; the application and limitations of these technologies to guide rational fluid therapy in surgical and critically ill patients.

RESULTS

Transpulmonary dilution techniques correlate well with pulmonary artery catheter-derived measurement of cardiac output. Volumetric measures of preload appear to be superior to central venous and pulmonary artery occlusion pressures. Dynamic indices of preload responsiveness such as stroke volume variation are more useful than static measures in mechanically ventilated patients.

CONCLUSION

In fully mechanically ventilated patients, dynamic measurements of heart-lung interaction such as stroke volume variation are superior to static measures of preload in assessing whether a patient is volume-responsive (i.e. will increase stroke volume in response to a fluid challenge). For patients who are not fully mechanically ventilated, pulse contour analysis allows real-time assessment of increases in cardiac output in response to passive leg-raising.

Excess circulating angiopoietin-2 is a strong predictor of mortality in critically ill medical patients

Introduction

The endothelial specific angiopoietin (Ang)-Tie2 ligand-receptor system has been identified as a non-redundant mediator of endothelial activation in experimental sepsis. Binding of circulating Ang-1 to the Tie2 receptor protects the vasculature from inflammation and leakage, whereas binding of Ang-2 antagonises Tie2 signalling and disrupts endothelial barrier function. Here, we examine whether circulating Ang-1 and/or Ang-2 independently predict mortality in a cohort of critically ill medical patients.

Methods

Circulating vascular endothelial growth factor (VEGF), Ang-1 and Ang-2 were prospectively measured in sera from 29 healthy controls and 43 medical ICU patients by immunoradiometric assay (IRMA) and ELISA, respectively. Survival after 30 days was the primary outcome studied.

Results

Median serum Ang-2 concentrations were increasingly higher across the following groups: healthy controls, patients without sepsis, patients with sepsis and patients with septic shock. In contrast, Ang-1 and VEGF concentrations were significantly lower in all patient groups compared with healthy controls. Ang-2 correlated with partial pressure of oxygen in arterial blood (PaO₂)/fraction of inspired oxygen (FiO₂), tissue hypoxia, Sequential Organ Failure Assessment (SOFA) and Physiology and Chronic Health Evaluation II (APACHE II) score. Multivariate Cox regression analyses confirmed a strong independent prognostic impact of high Ang-2 as a novel marker of 30-day survival.

Conclusions

A marked imbalance of the Ang-Tie system in favour of Ang-2 is present in critically ill medical patients. Our findings highlight the independent prognostic impact of circulating Ang-2 in critical illness. Ang-2 may be used as a readily available powerful predictor of outcome and may open new perspectives to individualise treatment in the ICU.

Accuracy of cardiac function and volume status estimates using the bedside echocardiographic assessment in trauma/critical care

BACKGROUND

Critically ill patients often require invasive monitoring to evaluate and optimize cardiac function and preload. With questionable outcomes associated with pulmonary artery catheters (PACs), some have evaluated the role of less invasive monitors. We hypothesized that the Bedside Echocardiographic Assessment in Trauma (BEAT) examination would generate cardiac index (CI) and central venous pressure (CVP) estimates that correlate with that of a PAC.

METHODS

BEAT was performed on all SICU patients with a PAC in place. Prospective data included stroke volume and the inferior vena cava (IVC) diameter. The CI was calculated and correlated with that from the PAC. Each CI was then categorized as low, normal, or high. The IVC diameter was used to estimate the CVP. The association between the BEAT and PAC estimates of CI and CVP was evaluated using chi.

RESULTS

Eighty-five BEAT examinations were performed, 57% on trauma and 37% on general surgery patients. Fifty-nine percent of the CI examinations and 97% of the IVC examinations contained quality images. Of these, the overall correlation coefficient was 0.70 (p < 0.0001). When CI was categorized, there was a significant association between the BEAT and PAC (p = 0.021). There was a significant association between the CVP estimate from the BEAT examination and the PAC (p = 0.031).

CONCLUSION

Our data show a significant correlation between the CI and CVP estimates obtained from the BEAT examination and that from a PAC. BEAT provides a noninvasive method of evaluating cardiac function and volume status. Bedside echocardiography is teachable and should become a part of future critical care curricula.