Meta-analysis of hemodynamic optimization: relationship to methodological quality

Abilities of pulse pressure variations and stroke volume variations to predict fluid responsiveness in prone position during scoliosis surgery

BACKGROUND

Pulse pressure variation (PPV) and stroke volume variation (SVV) are robust indicators of fluid responsiveness in mechanically ventilated supine patients. The aim of the study was to evaluate the ability of PPV and SVV to predict fluid responsiveness in mechanically ventilated patients in the prone position (PP) during scoliosis surgery.

METHODS

Thirty subjects were studied after the induction of anaesthesia in the supine position [before and after volume expansion (VE) with 500 ml of hetastarch 6%] and in PP (immediately after PP and before and after VE). PPV, SVV, cardiac output (CO), and static compliance of the respiratory system were recorded at each interval. Subjects were defined as responders (Rs) to VE if CO increased > or =15%.

RESULTS

Three subjects were excluded. In the supine position, 16 subjects were Rs. PPV and SVV before VE were correlated with VE-induced changes in CO (r(2)=0.64, P<0.0001 and r(2)=0.56, P<0.0001, respectively). Fluid responsiveness was predicted by PPV >11% (sensitivity=88%, specificity=82%) and by SVV >9% (sensitivity=88%, specificity=91%). PP induced an increase in PPV and SVV (P<0.0001) and a decrease in the static compliance of the respiratory system (P<0.0001). In PP, 17 patients were Rs. PPV and SVV before VE were correlated with VE-induced changes in CO (r(2)=0.59, P<0.0001 and r(2)=0.55, P<0.0005, respectively). Fluid responsiveness was predicted in PP by PPV >15% (sensitivity=100%, specificity=80%) and by SVV >14% (sensitivity=94%, specificity=80%).

CONCLUSIONS

PP induces a significant increase in PPV and SVV but does not alter their abilities to predict fluid responsiveness.

Goal-directed intraoperative therapy based on autocalibrated arterial pressure waveform analysis reduces hospital stay in high-risk surgical patients: a randomized, controlled trial

Introduction

Several studies have shown that goal-directed hemodynamic and fluid optimization may result in improved outcome. However, the methods used were either invasive or had other limitations. The aim of this study was to perform intraoperative goal-directed therapy with a minimally invasive, easy to use device (FloTrac/Vigileo), and to evaluate possible improvements in patient outcome determined by the duration of hospital stay and the incidence of complications compared to a standard management protocol.

Methods

In this randomized, controlled trial 60 high-risk patients scheduled for major abdominal surgery were included. Patients were allocated into either an enhanced hemodynamic monitoring group using a cardiac index based intraoperative optimization protocol (FloTrac/Vigileo device, GDT-group, n = 30) or a standard management group (Control-group, n = 30), based on standard monitoring data.

Results

The median duration of hospital stay was significantly reduced in the GDT-group with 15 (12 - 17.75) days versus 19 (14 - 23.5) days (P = 0.006) and fewer patients developed complications than in the Control-group [6 patients (20%) versus 15 patients (50%), P = 0.03]. The total number of complications was reduced in the GDT-group (17 versus 49 complications, P = 0.001).

Conclusions

In high-risk patients undergoing major abdominal surgery, implementation of an intraoperative goal-directed hemodynamic optimization protocol using the FloTrac/Vigileo device was associated with a reduced length of hospital stay and a lower incidence of complications compared to a standard management protocol.

Trial Registration

Clinical trial registration information: Unique identifier: NCT00549419

Pitfalls in the evaluation and resuscitation of the trauma patient

The management of the trauma patient presents the practitioner with a host of challenges, and the pace, variety of venues, and multidisciplinary nature of the field combine to create a system complexity that is laden with potential pitfalls. This review summarizes some of the general principles of medical errors and examines some of the more common pitfalls encountered in the initial resuscitation and evaluation of the major trauma patient.

Goal-directed haemodynamic therapy and gastrointestinal complications in major surgery: a meta-analysis of randomized controlled trials

Postoperative gastrointestinal (GI) dysfunction is one of the most frequent complications in surgical patients. Most cases are associated with episodes of splanchnic hypoperfusion due to hypovolaemia or cardiac dysfunction. It has been suggested that perioperative haemodynamic goal-directed therapy (GDT) may reduce the incidence of these complications in cardiac surgery, and other surgery, but clear evidence is lacking. We have undertaken a meta-analysis of the effects of GDT on postoperative GI and liver complications. A systematic search, using MEDLINE, EMBASE, and The Cochrane Library databases, was performed. Sixteen randomized controlled trials (3410 participants) met the inclusion criteria. Data synthesis was obtained using odds ratio (OR) with 95% confidence interval (CI) by random-effects model. Statistical heterogeneity was assessed by Q and I2 statistics. GI complications were ranked as major (required radiological or surgical intervention or life-threatening condition) or minor (no or only pharmacological treatment required). Major GI complications were significantly reduced by GDT when compared with a control group (OR, 0.42; 95% CI, 0.27-0.65). Minor GI complications were also significantly decreased in the GDT group (OR, 0.29; 95% CI, 0.17-0.50). Treatment did not reduce hepatic injury rate (OR, 0.54; 95% CI, 0.19-1.55). Quality sensitive analyses confirmed the main overall results. In patients undergoing major surgery, GDT, by maintaining an adequate systemic oxygenation, can protect organs particularly at risk of perioperative hypoperfusion and is effective in reducing GI complications.

[Haemodynamic monitoring in the perioperative phase. Available systems, practical application and clinical data]

A regular hydration status and compensated vascular filling are targets of perioperative fluid and volume management and, in parallel, represent precautions for sufficient stroke volume and cardiac output to maintain tissue oxygenation. The physiological and pathophysiological effects of fluid and volume replacement mainly depend on the pharmacological properties of the solutions used, the magnitude of the applied volume as well as the timing of volume replacement during surgery. In the perioperative setting surgical stress induces physiological and hormonal adaptations of the body, which in conjunction with an increased permeability of the vascular endothelial layer influence fluid and volume management. The target of haemodynamic monitoring in the operation room is to collect data on haemodynamics and global oxygen transport, which enable the anaesthetist to estimate the volume status of the vascular system. Particularly in high risk patients this may improve fluid and volume therapy with respect to maintaining cardiac output. A goal-directed volume management aiming at preventing hypovolaemia may improve the outcome after surgery. The objective of this article is to review the monitoring devices that are currently used to assess haemodynamics and filling status in the perioperative setting. Methods and principles for measuring haemodynamic variables, the measured and calculated parameters as well as clinical benefits and shortcomings of each device are described. Furthermore, the results for monitoring devices from clinical studies of goal-directed fluid and volume therapy which have been published will be discussed.

Clinical review: Goal-directed therapy in high risk surgical patients

A small group of patients account for the majority of peri-operative morbidity and mortality. These 'high-risk' patients have a poor outcome due to their inability to meet the oxygen transport demands imposed on them by the nature of the surgical response during the peri-operative period. It has been shown that by targeting specific haemodynamic and oxygen transport goals at any point during the peri-operative period, the outcomes of these patients can be improved. This goal directed therapy includes the use of fluid loading and inotropes, in order to optimize the preload, contractility and afterload of the heart whilst maintaining an adequate coronary perfusion pressure. Despite the benefits seen, it remains a challenge to implement this management due to difficulties in identifying these patients, scepticism and lack of critical care resources.

Does perioperative hemodynamic optimization protect renal function in surgical patients? A meta-analytic study

OBJECTIVE

Postoperative acute deterioration in renal function, producing oliguria and/or increase in serum creatinine, is one of the most serious complication in surgical patients. Most cases are due to renal hypoperfusion as a consequence of systemic hypotension, hypovolemia, and cardiac dysfunction. Although some evidence suggests that perioperative monitoring and manipulation of oxygen delivery by volume expansion and inotropic drugs may decrease mortality in surgical patients, no study analyzed this approach on postoperative renal dysfunction. The objective of this investigation is to perform a meta-analysis on the effects of perioperative hemodynamic optimization on postoperative renal dysfunction. DATA SOURCES, STUDY SELECTION, DATA EXTRACTION: A systematic literature review, using MEDLINE, EMBASE, and The Cochrane Library databases through January 2008 was conducted and 20 studies met the inclusion criteria (4220 participants). Data synthesis was obtained by using odds ratio (OR) with 95% confidence interval (CI) by random-effects model.

DATA SYNTHESIS

Postoperative acute renal injury was significantly reduced by perioperative hemodynamic optimization when compared with control group (OR 0.64; CI 0.50-0.83; p = 0.0007). Perioperative optimization was effective in reducing renal injury defined consistently with risk, injury, failure, and loss and end-stage kidney disease and Acute Kidney Injury Network classifications, and in studies defining renal dysfunction by serum creatinine and/or need of renal replacement therapy only (OR 0.66; CI 0.50-0.88; p = 0.004). The occurrence of renal dysfunction was reduced when treatment started both preoperatively and intraoperatively or postoperatively, was performed in high-risk patients, and was obtained by fluids and inotropes. Mortality was significantly reduced in treatment group (OR 0.50; CI 0.31-0.80; p = 0.004), but statistical heterogeneity was observed.

CONCLUSIONS

Surgical patients receiving perioperative hemodynamic optimization are at decreased risk of renal impairment. Because of the impact of postoperative renal complications on adverse outcome, efforts should be aimed to identify patients and surgery that would most benefit from perioperative optimization.

The effect of a quantitative resuscitation strategy on mortality in patients with sepsis: a meta-analysis

OBJECTIVE

Quantitative resuscitation consists of structured cardiovascular intervention targeting predefined hemodynamic end points. We sought to measure the treatment effect of quantitative resuscitation on mortality from sepsis.

DATA SOURCES

We conducted a systematic review of the Cochrane Library, MEDLINE, EMBASE, CINAHL, conference proceedings, clinical practice guidelines, and other sources using a comprehensive strategy.

STUDY SELECTION

We identified randomized control trials comparing quantitative resuscitation with standard resuscitation in adult patients who were diagnosed with sepsis using standard criteria. The primary outcome variable was mortality.

DATA ABSTRACTION

Three authors independently extracted data and assessed study quality using standardized instruments; consensus was reached by conference. Preplanned subgroup analysis required studies to be categorized based on early (at the time of diagnosis) vs. late resuscitation implementation. We used the chi-square test and I to assess for statistical heterogeneity (p < 0.10, I > 25%). The primary analysis was based on the random effects model to produce pooled odds ratios with 95% confidence intervals.

RESULTS

The search yielded 29 potential publications; nine studies were included in the final analysis, providing a sample of 1001 patients. The combined results demonstrate a decrease in mortality (odds ratio 0.64, 95% confidence interval 0.43-0.96); however, there was statistically significant heterogeneity (p = 0.07, I = 45%). Among the early quantitative resuscitation studies (n = 6) there was minimal heterogeneity (p = 0.40, I = 2.4%) and a significant decrease in mortality (odds ratio 0.50, 95% confidence interval 0.37-0.69). The late quantitative resuscitation studies (n = 3) demonstrated no significant effect on mortality (odds ratio 1.16, 95% confidence interval 0.60-2.22).

CONCLUSION

This meta-analysis found that applying an early quantitative resuscitation strategy to patients with sepsis imparts a significant reduction in mortality.

Perioperative goal directed haemodynamic therapy--do it, bin it, or finally investigate it properly?

The literature concerning the use of goal directed haemodynamic therapy (GDHT) in high risk surgical patients has been importantly increased by the study of Lopes and colleagues. Using a minimally invasive assessment of fluid status and pulse pressure variation monitoring during mechanical ventilation, improvements were seen in post-operative complications, duration of mechanical ventilation, and length of hospital and intensive care unit (ICU) stay. Many small studies have shown improved outcome using various GDHT techniques but widespread implementation has not occurred. Those caring for perioperative patients need to accept the published evidence base or undertake a larger, multi-centre study.

The ability of a novel algorithm for automatic estimation of the respiratory variations in arterial pulse pressure to monitor fluid responsiveness in the operating room

BACKGROUND

Respiratory variations in arterial pulse pressure (deltaPP(man)) are accurate predictors of fluid responsiveness in mechanically ventilated patients. However, they cannot be continuously monitored. In our study, we assessed the clinical utility of a novel algorithm for automatic estimation of deltaPP (deltaPP(auto)).

METHODS

We studied 25 patients referred for coronary artery bypass grafting. DeltaPP(auto) was continuously displayed using a method based on automatic detection algorithms, kernel smoothing, and rank-order filters. All patients were under general anesthesia, mechanical ventilation, and were also monitored with a pulmonary artery catheter. DeltaPP(man) and deltaPP(auto) were recorded simultaneously at eight steps during surgery including before and after intravascular volume expansion (500 mL hetastarch). Responders to volume expansion were defined as patients whose cardiac index increased by more than 15% after volume expansion.

RESULTS

Agreement between deltaPP(man) and deltaPP(auto) over the 200 pairs of collected data was 0.7% +/- 3.4% (mean bias +/- SD). Seventeen patients were responders to volume expansion. A threshold deltaPP(man) value of 12% allowed discrimination of responders to volume expansion with a sensitivity of 88% and a specificity of 100%. A threshold deltaPP(auto) value of 10% allowed discrimination of responders to volume expansion with a sensitivity of 82% and a specificity of 88%.

CONCLUSION

DeltaPP(auto) is strongly correlated to deltaPP(man) is an accurate predictor of fluid responsiveness, and allows continuous monitoring of deltaPP. This novel algorithm has potential clinical applications.

Central Venous Blood Oxygen Saturation Monitoring in Patients With Chronic Pulmonary Arterial Hypertension Treated With Continuous IV Epoprostenol

BACKGROUND

IV epoprostenol is a highly effective therapy for pulmonary arterial hypertension (PAH). However, monitoring the efficacy and adjusting the dose of epoprostenol often requires serial invasive hemodynamic measurements. This study investigated whether superior vena cava (SVC) oxygen saturation measured from the indwelling catheter and brain natriuretic peptide (BNP) level would predict right heart catheterization markers associated with lower survival rates (right atrial pressure [RAP], > 10 mm Hg; pulmonary artery [PA] oxygen saturation, < 62%) in epoprostenol-treated patients with PAH.

METHODS

Twenty-seven epoprostenol-treated PAH patients had a BNP level and SVC oxygen saturation measured from their indwelling central venous catheters. The results were compared with cardiac catheterization results.

RESULTS

SVC oxygen saturation and BNP level both showed significant correlation with hemodynamic variables. BNP level correlated best with RAP (r = 0.66; p < 0.001), while SVC oxygen saturation correlated most closely with PA oxygen saturation (r = 0.91; p < 0.001). All patients with a BNP level of >or= 117 pg/mL had an elevated RAP (specificity, 100% [defined as a RAP of > 10 mm Hg]), but sensitivity was only 65%. An SVC oxygen saturation of < 64% showed a sensitivity of 89% and a specificity of 78% in predicting a PA oxygen saturation of < 62%.

CONCLUSIONS

SVC oxygen saturation and BNP level predict hemodynamics associated with lower survival rates and may be useful as "noninvasive" markers of prognosis in epoprostenol-treated PAH patients. BNP levels have a lower sensitivity relative to specificity, and a normal BNP level did not exclude a high RAP or low PA oxygen saturation.

Hemodynamic monitoring in shock and implications for management. International Consensus Conference, Paris, France, 27-28 April 2006

OBJECTIVE

Shock is a severe syndrome resulting in multiple organ dysfunction and a high mortality rate. The goal of this consensus statement is to provide recommendations regarding the monitoring and management of the critically ill patient with shock.

METHODS

An international consensus conference was held in April 2006 to develop recommendations for hemodynamic monitoring and implications for management of patients with shock. Evidence-based recommendations were developed, after conferring with experts and reviewing the pertinent literature, by a jury of 11 persons representing five critical care societies.

DATA SYNTHESIS

A total of 17 recommendations were developed to provide guidance to intensive care physicians monitoring and caring for the patient with shock. Topics addressed were as follows: (1) What are the epidemiologic and pathophysiologic features of shock in the ICU? (2) Should we monitor preload and fluid responsiveness in shock? (3) How and when should we monitor stroke volume or cardiac output in shock? (4) What markers of the regional and micro-circulation can be monitored, and how can cellular function be assessed in shock? (5) What is the evidence for using hemodynamic monitoring to direct therapy in shock? One of the most important recommendations was that hypotension is not required to define shock, and as a result, importance is assigned to the presence of inadequate tissue perfusion on physical examination. Given the current evidence, the only bio-marker recommended for diagnosis or staging of shock is blood lactate. The jury also recommended against the routine use of (1) the pulmonary artery catheter in shock and (2) static preload measurements used alone to predict fluid responsiveness.

CONCLUSIONS

This consensus statement provides 17 different recommendations pertaining to the monitoring and caring of patients with shock. There were some important questions that could not be fully addressed using an evidence-based approach, and areas needing further research were identified.

High-altitude physiology and pathophysiology: implications and relevance for intensive care medicine

Cellular hypoxia is a fundamental mechanism of injury in the critically ill. The study of human responses to hypoxia occurring as a consequence of hypobaria defines the fields of high-altitude medicine and physiology. A new paradigm suggests that the physiological and pathophysiological responses to extreme environmental challenges (for example, hypobaric hypoxia, hyper-baria, microgravity, cold, heat) may be similar to responses seen in critical illness. The present review explores the idea that human responses to the hypoxia of high altitude may be used as a means of exploring elements of the pathophysiology of critical illness.

Esophageal Doppler-guided fluid management decreases blood lactate levels in multiple-trauma patients: a randomized controlled trial

Introduction

Esophageal Doppler was confirmed as a useful non-invasive tool for management of fluid replacement in elective surgery. The aim of this study was to assess the effect of early optimization of intravascular volume using esophageal Doppler on blood lactate levels and organ dysfunction development in comparison with standard hemodynamic management in multiple-trauma patients.

Methods

This was a randomized controlled trial. Multiple-trauma patients with blood loss of more than 2,000 ml admitted to the intensive care unit (ICU) were randomly assigned to the protocol group with esophageal Doppler monitoring and to the control group. Fluid resuscitation in the Doppler group was guided for the first 12 hours of ICU stay according to the protocol based on data obtained by esophageal Doppler, whereas control patients were managed conventionally. Blood lactate levels and organ dysfunction during ICU stay were evaluated.

Results

Eighty patients were randomly assigned to Doppler and 82 patients to control treatment. The Doppler group received more intravenous colloid during the first 12 hours of ICU stay (1,667 ± 426 ml versus 682 ± 322 ml; p < 0.0001), and blood lactate levels in the Doppler group were lower after 12 and 24 hours of treatment than in the control group (2.92 ± 0.54 mmol/l versus 3.23 ± 0.54 mmol/l [p = 0.0003] and 1.99 ± 0.44 mmol/l versus 2.37 ± 0.58 mmol/l [p < 0.0001], respectively). No difference in organ dysfunction between the groups was found. Fewer patients in the Doppler group developed infectious complications (15 [18.8%] versus 28 [34.1%]; relative risk = 0.5491; 95% confidence interval = 0.3180 to 0.9482; p = 0.032). ICU stay in the Doppler group was reduced from a median of 8.5 days (interquartile range [IQR] 6 to16) to 7 days (IQR 6 to 11) (p = 0.031), and hospital stay was decreased from a median of 17.5 days (IQR 11 to 29) to 14 days (IQR 8.25 to 21) (p = 0.045). No significant difference in ICU and hospital mortalities between the groups was found.

Conclusion

Optimization of intravascular volume using esophageal Doppler in multiple-trauma patients is associated with a decrease of blood lactate levels, a lower incidence of infectious complications, and a reduced duration of ICU and hospital stays.

The importance of transitions between dialysis and transplantation in the care of end-stage renal disease patients

Analyses describing outcomes of kidney transplantation usually exclude the survival of wait-listed patients and dialysis patients with failed kidney transplants, and thus reflect only a portion of the typical transplant process. We determined death rates during the continuum of wait-listing, transplantation, and after allograft failure among adult end-stage renal disease patients in the United States between 1995 and 2003. Before transplantation, death rates increased with longer waiting times. Death rates were lowest during the period of allograft function and highest after allograft failure. Patients were at particularly high risk during periods of transition between dialysis and transplantation (death rates during the peri-transplant period and during the re-initiation of dialysis after transplant failure were 8.2/100 patient-years (95% confidence interval (CI) 7.7, 8.8) and 17.9/100 patient-years (95% CI 15.7, 20.3), respectively compared to 6.4/100 patient-years (95% CI 6.25, 6.51) during the period of wait-listing. Diabetic patients and older patients were at increased risk at all time points. The most common known cause of death in all age subgroups was cardiovascular disease. The proportion of death owing to sepsis was greatest after allograft failure (16.8% of all deaths were due to sepsis compared to 14.0% during wait-listing, and 12.7% during the period of allograft function). Consideration of the entire transplant experience as a whole should help to focus patient care on periods of particularly high risk, and emphasizes opportunities to improve outcomes by strategies aimed at preventing death owing to cardiovascular and infectious causes.

Monitoring of peri-operative fluid administration by individualized goal-directed therapy

BACKGROUND

In order to avoid peri-operative hypovolaemia or fluid overload, goal-directed therapy with individual maximization of flow-related haemodynamic parameters has been introduced. The objectives of this review are to update research in the area, evaluate the effects on outcome and assess the use of strategies, parameters and monitors for goal-directed therapy.

METHODS

A MEDLINE search (1966 to 2 October 2006) was performed to identify studies in which a goal-directed therapeutic strategy was used to maximize flow-related haemodynamic parameters in surgical patients, as well as studies referenced from these papers. Furthermore, methods applied in these studies and other monitors with a potential for goal-directed therapy are described.

RESULTS

Nine studies were identified pertaining to fluid optimization during the intra- and post-operative period with goal-directed therapy. Seven studies (n = 725) found a reduced hospital stay. Post-operative nausea and vomiting (PONV) and ileus were reduced in three studies and complications were reduced in four studies. Of the monitors that may be applied for goal-directed therapy, only oesophageal Doppler has been tested adequately; however, several other options exist.

CONCLUSION

Goal-directed therapy with the maximization of flow-related haemodynamic variables reduces hospital stay, PONV and complications, and facilitates faster gastrointestinal functional recovery. So far, oesophageal Doppler is recommended, but other monitors are available and call for evaluation.

Measurement of acid-base resuscitation endpoints: lactate, base deficit, bicarbonate or what?

PURPOSE OF REVIEW

Inadequate oxygen delivery to the tissues frequently results in significant metabolic acidosis. The resultant cellular and organ dysfunction can increase morbidity, mortality and hospital stay. Early diagnosis of shock can lead to early resuscitation efforts that can prevent ongoing tissue injury. This review focuses on the metabolic, hemodynamic and regional perfusion endpoints utilized in the diagnosis of metabolic acidosis resulting from shock. Resuscitation strategies aimed at supranormal oxygen delivery will be discussed.

RECENT FINDINGS

Serum pH, lactate, base deficit and bicarbonate have all been extensively studied as clinical markers of metabolic acidosis in shock. While their trend helps guide resuscitation, no single marker or specific value can be utilized to guide resuscitation for all patients. Hemodynamic parameters and regional tissue endpoints are designed to identify compensated shock before it progresses to uncompensated shock. Resuscitation strategies initiated in the early phases of shock can reduce complications and death. Efforts to resuscitate patients to supranormal oxygen delivery endpoints have demonstrated mixed success, with several notable complications.

SUMMARY

Despite the large number of endpoints available to the clinician, none are universally applicable and none have independently demonstrated improved survival when guiding resuscitation. Patients who respond well to initial resuscitation efforts demonstrate a survival advantage over nonresponders.

Year in review 2005: critical care--cardiology

This review summarizes key research papers published in the fields of cardiology and intensive care during 2005 in Critical Care. The papers have been grouped into categories: haemodynamic monitoring; goal-directed therapy; cardiac enzymes and critical care; metabolic considerations in cardiovascular performance; thrombosis prevention; physiology; and procedures and techniques.