Cardiac filling pressures are not appropriate to predict hemodynamic response to volume challenge

Principles of pharmacologic hemodynamic management and closed-loop systems

Every day, physicians in critical-care settings are challenged with the hemodynamic management of patients with severe cardiovascular derangements. There is a potential role for closed-loop (automated) systems to assist clinicians in managing these patients and growing interest in the possible applications. In this review, we discuss the basic principles of critical-care hemodynamic management and the closed-loop systems that have been developed to help in this setting.

Early identification and management of patients with severe sepsis and septic shock in the emergency department

Severe sepsis and septic shock have great relevance to Emergency Medicine physicians because of their high prevalence, morbidity, and mortality. Treatment is time-sensitive, depends on early identification risk stratification, and has the potential to significantly improve patient outcomes. In this article, we review the pathophysiology of, and evidence basis for, the emergency department management of severe sepsis and septic shock.

Evaluating the adequacy of fluid resuscitation in patients with septic shock: controversies and future directions

Fluid resuscitation is a cornerstone in the treatment of severe sepsis and septic shock. However, there is little evidence to guide clinicians in its administration. Current guidelines recommend targeting fluid therapy based on measurements of cardiac filling pressures, such as central venous pressure. Static pressures are poor predictors of a patient's response to fluid. Such response can be better predicted by measuring changes in hemodynamic parameters caused by positive pressure ventilation or maneuvers designed to simulate increased preload. These changes can be measured by analysis of arterial waveforms, echocardiography or Doppler, or with emerging noninvasive technologies. This article reviews the current role of fluid replacement strategies and the use of monitoring systems in the overall resuscitation of patients with severe sepsis and septic shock.

The reliability and validity of passive leg raise and fluid bolus to assess fluid responsiveness in spontaneously breathing emergency department patients

PURPOSE

We investigated the reproducibility of passive leg raise (PLR) and fluid bolus (BOLUS) using the Non-Invasive Cardiac Output Monitor (NICOM; Cheetah Medical, Tel Aviv, Israel) for assessment of fluid responsiveness (FR) in spontaneously breathing emergency department (ED) patients.

METHODS

Prospective, observational study of a convenience sample of adult ED patients receiving intravenous fluid bolus. We assessed stroke volume (SV) using NICOM and obtained results from PLR, where the head of the bed was changed from semirecumbent to supine while the patients' legs raised to 45° for 3 minutes. Fluid bolus was defined as 5 mL/kg normal saline infusion. Maximal increase in SV was recorded. Fluid responsiveness was defined as an increase of SV greater than 10% from baseline. We obtained 4 consecutive responses for each patient; PLR1, PLR2, BOLUS1 separated each by 10 minutes, and BOLUS2 initiated immediately after the end of BOLUS1. We calculated κ statistics, correlation coefficients, and odds ratios with 95% confidence interval and Bland-Altman plots.

RESULTS

We enrolled 109 patients enrolled in this study. The 2 PLRs were significantly correlated (r = 0.78, P < .001) with κ = 0.46 for FR (P < .001). The 2 BOLUSES less strongly correlated (r = 0.14, P = .001) and κ = 0.06 for FR (P < .001). Patients who were responsive to PLR1 had 9.5 (3.6-25) odds of being FR for PLR2, whereas those responsive to BOLUS1 had a 1.8 (0.76-4.3) increased odds of FR for BOLUS2.

CONCLUSION

In conclusion, we have found PLR as measured by the NICOM to be a promising tool for the evaluation of SV responsiveness. It was feasible for use in the ED, and the data suggest that the PLR technique may be more reproducible than the fluid bolus technique for assessing volume responsiveness.

Optimizing oxygen delivery in the critically ill: assessment of volume responsiveness in the septic patient

BACKGROUND

Assessing volume responsiveness, defined as an increase in cardiac index after infusion of fluids, is important when caring for critically ill patients in septic shock, as both under- and over-resuscitation can worsen outcomes. This review article describes the currently available methods of assessing volume responsiveness for critically ill patients in the emergency department, with a focus on patients in septic shock.

OBJECTIVE

The single-pump model of the circulation utilizing cardiac-filling pressures is reviewed in detail. Additionally, the dual-pump model evaluating cardiopulmonary interactions both invasively and noninvasively will be described.

DISCUSSION

Cardiac filling pressures (central venous pressure and pulmonary artery occlusion pressure) have poor performance characteristics when used to predict volume responsiveness. Cardiopulmonary interaction assessments (inferior vena cava distensibility/collapsibility, systolic pressure variation, pulse pressure variation, stroke volume variation, and aortic flow velocities) have superior test characteristics when measured either invasively or noninvasively.

CONCLUSION

Cardiac filling pressures may be misleading if used to determine volume responsiveness. Assessment of cardiopulmonary interactions has superior performance characteristics, and should be preferentially used for septic shock patients in the emergency department.

Pulse pressure variation is not a valid predictor of fluid responsiveness in patients with elevated left ventricular filling pressure

PURPOSE

The purpose of this study was to test the hypothesis that the predictive ability of pulse pressure variation (PPV) for fluid responsiveness would be altered in patients with elevated left ventricular (LV) filling pressure.

MATERIALS AND METHODS

According to the preoperative echocardiographic assessment of the ratio of early transmitral flow velocity to early diastolic velocity of the mitral annulus (E/E'), patients undergoing surgical coronary revascularization were classified into normal (n=34, E/E'<8) and high (n=34, E/E'>15) LV filling pressure group. After anesthetic induction, PPV and hemodynamic data were measured before and after 6 mL/kg of colloid administration. Fluid responsiveness was defined as 12% or more increase in stroke volume index assessed by pulmonary artery catheter and tested by the area under the receiver operating characteristic curve (AUROC).

RESULTS

The AUROCs of PPV in the normal and high filling pressure group were 0.829 (95% confidence interval [CI], 0.661-0.963; P<.001) and 0.583 (95% CI, 0.402-0.749; P=.110), respectively. The AUROCs of cardiac filling pressures and right ventricular end-diastolic volume index did not show statistical significance in both groups.

CONCLUSIONS

None of the assessed preload indices including PPV were able to predict fluid responsiveness in patients with elevated LV filling pressure.

Optimal range of global end-diastolic volume for fluid management after aneurysmal subarachnoid hemorrhage: a multicenter prospective cohort study

OBJECTIVES

Limited evidence supports the use of hemodynamic variables that correlate with delayed cerebral ischemia or pulmonary edema after aneurysmal subarachnoid hemorrhage. The aim of this study was to identify those hemodynamic variables that are associated with delayed cerebral ischemia and pulmonary edema after subarachnoid hemorrhage.

DESIGN

A multicenter prospective cohort study.

SETTING

Nine university hospitals in Japan.

PATIENTS

A total of 180 patients with aneurysmal subarachnoid hemorrhage.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients were prospectively monitored using a transpulmonary thermodilution system in the 14 days following subarachnoid hemorrhage. Delayed cerebral ischemia was developed in 35 patients (19.4%) and severe pulmonary edema was developed in 47 patients (26.1%). Using the Cox proportional hazards model, the mean global end-diastolic volume index (normal range, 680-800 mL/m) was the independent factor associated with the occurrence of delayed cerebral ischemia (hazard ratio, 0.74; 95% CI, 0.60-0.93; p = 0.008). Significant differences in global end-diastolic volume index were detected between the delayed cerebral ischemia and non-delayed cerebral ischemia groups (783 ± 25 mL/m vs 870 ± 14 mL/m; p = 0.007). The global end-diastolic volume index threshold that best correlated with delayed cerebral ischemia was less than 822 mL/m, as determined by receiver operating characteristic curves. Analysis of the Cox proportional hazards model indicated that the mean global end-diastolic volume index was the independent factor that associated with the occurrence of pulmonary edema (hazard ratio, 1.31; 95% CI, 1.02-1.71; p = 0.03). Furthermore, a significant positive correlation was identified between global end-diastolic volume index and extravascular lung water (r = 0.46; p < 0.001). The global end-diastolic volume index threshold that best correlated with severe pulmonary edema was greater than 921 mL/m.

CONCLUSIONS

Our findings suggest that global end-diastolic volume index impacts both delayed cerebral ischemia and pulmonary edema after subarachnoid hemorrhage. Maintaining global end-diastolic volume index slightly above normal levels has promise as a fluid management goal during the treatment of subarachnoid hemorrhage.

Cardiac ultrasound and abdominal compartment syndrome

This review focuses on the available literature published about the evaluation of haemodynamic consequences of the abdominal compartment syndrome (ACS). Animal and clinical studies described decreased venous return, systemic vasoconstriction, systolic and diastolic dysfunction of left and right ventricles. Doppler echocardiography is a non-invasive bedside procedure which provides a complete haemodynamic evaluation of patients with ACS. Despite numerous evaluations in anesthesia during laparoscopic surgery, the use of echocardiography remains scarce in critically ill patients with ACS.

The influence of different mechanical ventilator settings of peak inspiratory pressure on stroke volume variation in pediatric cardiac surgery patients

Background

The usefulness of dynamic parameters derived by heart-lung interaction for fluid responsiveness in pediatric patients has been revealed. However, the effects of peak inspiratory pressure (PIP) that could affect the absolute values and the accuracy in pediatric patients have not been well established.

Methods

Participants were 30 pediatric patients who underwent ventricular septal defect repair. After completion of surgical procedure and sternum closure, mean arterial blood pressure, heart rate, central venous pressure, cardiac output, cardiac index and stroke volume variation (SVV) were measured at PIP 10 cmH₂O (PIP10), at PIP 15 cmH₂O (PIP15), at PIP 20 cmH₂O (PIP20) and at PIP 25 cmH₂O (PIP25).

Results

SVV at PIP15 was larger than that at PIP10 (13.7 ± 2.9% at PIP10 vs 14.7 ± 2.5% at PIP15, P < 0.001) and SVV at PIP20 was larger than that at PIP10 and PIP15 (13.7 ± 2.9% at PIP10 vs 15.4 ± 2.5% at PIP20, P < 0.001; 14.7 ± 2.5% at PIP15 vs 15.4 ± 2.5% at PIP20, P < 0.001) and SVV at PIP25 was larger than that at PIP10 and PIP15 and PIP20 (13.7 ± 2.9% at PIP10 vs 17.4 ± 2.4% at PIP25, P < 0.001; 14.7 ± 2.5% at PIP15 vs 17.4 ± 2.4% at PIP25, P < 0.001; 15.4 ± 2.5% at PIP20 vs 17.4 ± 2.4% at PIP25, P < 0.001).

Conclusions

SVV is affected by different levels of PIP in same patient and under same volume status. This finding must be taken into consideration when SVV is used to predict fluid responsiveness in mechanically ventilated pediatric patients.

Central venous oxygen saturation and carbon dioxide gap as resuscitation targets in a hemorrhagic shock

BACKGROUND

Fluid resuscitation is still a major challenge. We aimed to describe changes in central venous oxygen saturation (ScvO2 ) and venous-to-arterial carbon dioxide gap (dCO2 ) during an experimental stroke volume (SV) index (SVI)-guided hemorrhage and fluid resuscitation model in pigs.

METHODS

Twelve anesthetized, mechanically ventilated pigs were bled till baseline SVI (Tbsl ) dropped by 50% (T0 ), thereafter fluid resuscitation was performed with balanced crystalloid in four steps until initial SVI was reached (T4 ). Statistical analysis was performed with Statistical Program for Social Sciences version 18.0; data are expressed as mean ± standard deviation.

RESULTS

After bleeding, ScvO2 dropped (Tbsl = 78 ± 7 vs. T0 = 61 ± 5% P < 0.05) and oxygen extraction ratio increased (Tbsl = 0.20 ± 0.07 vs. T0 = 0.36 ± 0.05, P < 0.05). By T4 the ScvO2 normalized, but on average it remained 5% lower than at Tbsl (T4 = 73 ± 9% P < 0.05) and oxygen extraction also remained higher as compared with Tbsl (T4 = 0.24 ± 0.09 P = 0.001). ScvO2 showed significant correlation with SVI (r = 0.564, P < 0.001). dCO2 increased during hypovolemia (Tbsl :5.3 ± 2.0 vs. T0 :9.6 ± 2.3 mmHg, P = 0.001), then returned to normal by T4 = 5.1 ± 2.6 mmHg, and it also showed significant correlation with SVI (R = -0.591, P < 0.001) and oxygen extraction (R = 0.735, P < 0.001).

CONCLUSIONS

In this SV-guided bleeding and fluid resuscitation model, both ScvO2 and dCO2 correlated well with changes in SV, but only the dCO2 returned to its baseline, normal value, while ScvO2 remained significantly lower than at baseline. These results suggest that dCO2 may be a good hemodynamic endpoint of resuscitation, while ScvO2 is not strictly a hemodynamic parameter, but rather an indicator of the balance between oxygen delivery and consumption.

The multimodal concept of hemodynamic stabilization

Hemodynamic instability often leads to hypoperfusion, which has a significant impact on outcome in both medical and surgical patients. Measures to detect and treat tissue hypoperfusion early by correcting the imbalance between oxygen delivery and consumption is of particular importance. There are several studies targeting different hemodynamic endpoints in order to investigate the effects of goal-directed therapy on outcome. A so-called multimodal concept putting several variables in context follows simple logic and may provide a broader picture. Furthermore, rather than treating population based "normal" values of certain indices, this concept can be translated into the individualized patient care to reach adequate oxygen supply and tissue oxygenation in order to avoid under, or over resuscitation, which are equally harmful. The purpose of this review is to give an overview of current data providing the basis of this a multimodal, individualized approach of hemodynamic monitoring and treatment.

Pulse pressure variation to predict fluid responsiveness in spontaneously breathing patients: tidal vs. forced inspiratory breathing

We evaluated whether pulse pressure variation can predict fluid responsiveness in spontaneously breathing patients. Fifty-nine elective thoracic surgical patients were studied before induction of general anaesthesia. After volume expansion with hydroxyethyl starch 6 ml.kg(-1) , patients were defined as responders by a ≥ 15% increase in the cardiac index. Haemodynamic variables were measured before and after volume expansion and pulse pressure variations were calculated during tidal breathing and during forced inspiratory breathing. Median (IQR [range]) pulse pressure variation during forced inspiratory breathing was significantly higher in responders (n = 29) than in non-responders (n = 30) before volume expansion (18.2 (IQR 14.7-18.2 [9.3-31.3])% vs. 10.1 (IQR 8.3-12.6 [4.8-21.1])%, respectively, p < 0.001). The receiver-operating characteristic curve revealed that pulse pressure variation during forced inspiratory breathing could predict fluid responsiveness (area under the curve 0.910, p < 0.0001). Pulse pressure variation measured during forced inspiratory breathing can be used to guide fluid management in spontaneously breathing patients.

Diagnostic accuracy of central venous saturation in estimating mixed venous saturation is proportional to cardiac performance among cardiac surgical patients

PURPOSE

Advanced hemodynamic monitoring in cardiac surgery translates into improvement in outcomes. We evaluated the relationship between central venous (ScvO2) and mixed venous (SvO2) saturations over the early postoperative period. The adequacy of their interchangeability was tested in patients with varying degrees of cardiac performance.

METHODS

In this prospective observational study, we evaluated 156 consecutive cardiac surgical patients in an academic center. The ScvO2 and SvO2 data were harvested from 468 paired samples taken preoperatively (T0), after weaning from cardiopulmonary bypass (T1) and on postoperative day 1 (T2).

RESULTS

The relationship between ScvO2 and SvO2 was inconsistent, with inferior correlations in patients with lower cardiac indices (CI) (Pearson r(2) = 0.37 if CI ≤2.0 L/min per square meter vs r(2) = 0.73 if CI >2.0 L/min per square meter, both P < .01). Patients with lower CI also had wider 95% limits of agreement between SvO2 and ScvO2. The proportion of patients with a negative SvO2-ScvO2 gradient increased over time (48/156 [31%] at T0 to 73/156 [47%] at T2; P < .01). This subgroup more frequently required inotropes at T2 than patients with a positive SvO2-ScvO2 gradient (odds ratio, 6.46 [95% confidence interval, 0.81-51.87], P = .06) and also had higher serum lactate levels (1.5 ± 0.8 vs 1.0 ± 0.4; P < .01).

CONCLUSIONS

The diagnostic accuracy of ScvO2 for estimating SvO2 is proportional to cardiac performance. A negative SvO2-ScvO2 gradient at T2 correlated with inotropic support requirement, higher operative risk score, age, lactate level, and duration of cardiopulmonary bypass.

Prognostic value of echocardiographic and Doppler parameters in horses admitted for colic complicated by systemic inflammatory response syndrome

OBJECTIVE

To assess the prognostic value of echocardiographic parameters of left ventricular (LV) function in horses with systemic inflammatory response syndrome (SIRS).

DESIGN

Prospective observational study.

SETTING

Veterinary teaching hospital.

ANIMALS

Forty-one horses admitted for colic with clinical evidence of SIRS.

INTERVENTIONS

All horses underwent Doppler echocardiographic examination on admission. LV echocardiographic parameters, including pulsed-wave tissue Doppler imaging parameters, were compared between nonsurvivors (n = 29) and horses that survived to discharge (n = 12).

MEASUREMENTS AND MAIN RESULTS

With comparable heart rate and LV preload estimate, LV stroke volume index, the velocity time integral, deceleration time, ejection time of Doppler aortic flow, and peak early diastolic myocardial velocity were lower in the nonsurviving than in the surviving horses, while pre-ejection period to ejection time ratio (PEP/ET) of Doppler aortic flow and the peak early diastolic filling velocity to peak early diastolic myocardial velocity ratio (E/Em) were higher (P < 0.05). A cut-off value of 0.26 for PEP/ET predicted mortality with 100% sensitivity and 42% specificity (area under the receiver operating characteristic curve: 0.71), whereas a cut-off value of 2.67 for E/Em predicted mortality with 100% sensitivity and 83% specificity (area under the receiver operating characteristic curve: 0.89).

CONCLUSIONS

Echocardiography may provide prognostic information in colic horses with clinical evidence of SIRS. Especially, PEP/ET and E/Em could be useful markers of systolic and diastolic dysfunction, respectively, to detect horses with a high risk of death requiring more intensive cardiovascular monitoring as it has been reported in human patients with septic shock.

Endpoints of resuscitation: what are they anyway?

Hemodynamic optimization of surgical patients during and after surgery in the Surgical Intensive Care Unit is meant to improve outcomes. These outcomes have been measured by Length Of Stay (LOS), rate of infection, days on ventilator, etc. Unfortunately, the adaptation of modern technology to accomplish this has been slow in coming. Ever since Shoemaker described in 1988 using a pulmonary artery catheter (PAC) to guide fluid and inotropic administration to deliver supranormal tissue oxygenation, many authors have written about different techniques to achieve this "hemodynamic optimization". Since the PAC and CVC have both gone out of favor for utilization to monitor and improve hemodynamics, many clinicians have resorted using the easy to use static measurements of blood pressure (BP), heart rate (HR), and urine output. In this paper, the authors will review why these static measurements are no longer adequate and review some of the newer technology that have been studied and proven useful. This review of newer technologies combined with laboratory measurements that have also proven to help guide the clinician, may provide the impetus to adopt new strategies in the operating rooms (OR) and SICU.

Stroke volume variation fail to predict fluid responsiveness in patients undergoing pulmonary lobectomy with one-lung ventilation using thoracotomy

The purpose of this study was to investigate the ability of stroke volume variation (SVV) to predict fluid responsiveness in patients undergoing pulmonary lobectomy with one lung ventilation (OLV). Thirty patients intubated with double-lumen tube were scheduled for a pulmonary lobectomy requiring OLV for at least 1 hour under general anesthesia. Hemodynamic variables including heart rate, mean arterial pressure, cardiac index (CI), stroke volume index (SVI), central venous pressure (CVP) and SVV were measured before and after volume expansion (VE) (8 mL/kg of 6% hydroxyethyl starch). Fluid responsiveness was defined as an increase in CI ≥ 10% after VE. Of the 30 patients, 16 (53%) were responders and 14 (47%) were nonresponders to intravascular VE. There were significant increases of CI, SVI in responders after VE (p < 0.01), but there were no significant changes in SVV in responders and nonresponders (p > 0.05). The baseline value of SVV, CVP, CI and SVI did not correlate significantly with ΔCI (p > 0.05). The area under the Receiver Operating Characteristic (ROC) curve were 0.507 for SVV (95% confidence interval, 0.294-0.720) and 0.556 for CVP (95% confidence interval, 0.339-0.773), neither was able to predict fluid responsiveness with sufficient statistical power. SVV measured by the Vigileo-FloTrac system was not able to predict fluid responsiveness in patients undergoing pulmonary lobectomy with OLV after thoractomy.

Impact of a goal-directed therapy protocol on postoperative fluid balance in patients undergoing liver transplantation: a retrospective study

OBJECTIVE

Liver transplantation carries major risks during the perioperative period. Few studies focused on the hemodynamics of patients undergoing liver transplantation. The present study was aimed to evaluate the impact of the implementation of a protocol including goal-directed therapy in patients undergoing liver transplantation. Our first goal was to determine its impact on the fluid balance. Secondarily, we evaluated possible improvements in the patient outcomes.

STUDY DESIGN

A before and after study.

PATIENTS AND METHODS

Fifty patients undergoing liver transplantation were included during two successive six-month periods. During the first period, the management of the patients was left at the discretion of the senior physicians (control group, n=25). During the second period, the patients were treated according to a predetermined protocol including a specific hemodynamic monitoring (protocol group, n=25).

RESULTS

The fluid balance was negative in the protocol group and positive in the control group at 24h (-606mL vs. +3445mL, P<0.01) and 48h (-2315mL vs. +1170mL, P<0.01) after liver transplantation. The volume of the crystalloid administration was lower in the protocol group than in the control group (5000mL vs. 8000mL, P<0.01, and 1500mL vs. 6000mL, P<0.01, during surgery and 48h after liver transplantation, respectively). The duration of mechanical ventilation and postoperative ileus were significantly reduced in the protocol group, as compared with the control group, 20h vs. 94h (P<0.01) and 4days vs. 6days (P<0.01), respectively.

CONCLUSION

For patients undergoing liver transplantation, the implementation of a protocol aiming to optimize hemodynamics was associated with reduced fluid balance and decreased requirement for mechanical ventilation and postoperative ileus duration.

Fluid responsiveness predicted by elevation of PEEP in patients with septic shock

BACKGROUND

The assessment of whether a patient is fluid responsive can be difficult in clinical practice. Invasive filling pressures are inadequate indicators of preload and fluid responsiveness in critically ill patients. Dynamic indices may be unreliable in clinical practice because of arrhythmias or spontaneous breathing efforts. Elevation of positive end-expiratory pressure (PEEP) causes cardiorespiratory interactions, which may produce signs of hypovolaemia. Our aim was to assess whether haemodynamic changes during a short elevation of PEEP would predict fluid responsiveness in patients with septic shock.

METHODS

We performed a prospective observational study in 20 patients with septic shock on mechanical ventilation. We assessed the following changes in haemodynamic variables during a temporary elevation of PEEP from 10 cm H2O to 20 cm H2O during an end-expiratory pause: mean arterial pressure (MAP), systolic arterial pressure, pulse pressure, central venous pressure, pulmonary artery occlusion pressure, left ventricular end diastolic area and aortic velocity-time integral. We defined fluid responsiveness as an increase in cardiac output of 15% to a subsequent fluid challenge.

RESULTS

Decrease in MAP related to elevation of PEEP predicted fluid responsiveness (P = 0.003). The best cut-off value of ΔMAP for clinical use was -8%, with a negative predictive value for fluid responsiveness of 100%.

CONCLUSION

In patients with septic shock, the absence of decrease in MAP during an elevation of PEEP may be used to identify patients who will not increase their cardiac output in response to fluid challenge.

Can we Improve Outcome in High Risk Surgery?

Despite the small number of high-risk surgical patients in comparison to all surgical patients, they account for the largest proportion of overall perioperative mortality. Goal directed hemodynamic support may result in a lower incidence of complications and reduced length of hospital stay in these patients. Beyond the standard monitoring of circulation, such as blood pressure and heart rate, further parameters and procedures such as pulse pressure/stroke volume variation-, stroke volume/cardiac index-, and central venous oxygen saturation-guided resuscitation may improve the outcome of high-risk surgical patients. The aim of this review is to focus on the results of animal and clinical studies investigating the usefulness of these indices in the context of goal-directed perioperative support.

Obituary: pulmonary artery catheter 1970 to 2013

The birth of the intermittent injectate-based conventional pulmonary artery catheter (fondly nicknamed PAC) was proudly announced in the New England Journal of Medicine in 1970 by his parents HJ Swan and William Ganz. PAC grew rapidly, reaching manhood in 1986 where, in the US, he was shown to influence the management of over 40% of all ICU patients. His reputation, however, was tarnished in 1996 when Connors and colleagues suggested that he harmed patients. This was followed by randomized controlled trials demonstrating he was of little use. Furthermore, reports surfaced suggesting that he was unreliable and inaccurate. It also became clear that he was poorly understood and misinterpreted. Pretty soon after that, a posse of rivals (bedside echocardiography, pulse contour technology) moved into the neighborhood and claimed they could assess cardiac output more easily, less invasively and no less reliably. To make matter worse, dynamic assessment of fluid responsiveness (pulse pressure variation, stroke volume variation and leg raising) made a mockery of his ‘wedge’ pressure. While a handful of die-hard followers continued to promote his mission, the last few years of his existence were spent as a castaway until his death in 2013. His cousin (the continuous cardiac output PAC) continues to eke a living mostly in cardiac surgery patients who need central access anyway. This paper reviews the rise and fall of the conventional PAC.

Hemodynamic pressure waveform analysis in predicting fluid responsiveness

OBJECTIVE

To assess the usefulness of central venous pressure (CVP), diastolic right ventricular pressure, and pulmonary capillary wedge pressure (PCWP) waveform analysis in predicting fluid responsiveness.

DESIGN

A prospective observational study.

SETTING

Tertiary care university hospital.

PATIENTS

Forty-four patients undergoing coronary artery bypass grafting.

INTERVENTIONS

Analysis of the a/v wave ratio of the PCWP, CVP, and right ventricular dP/dt to predict an increase in stroke volume >15% after the administration of 500 mL of colloid.

MEASUREMENTS AND MAIN RESULTS

Forty-four patients were enrolled in this study and 7 were excluded. There were 24 responders and 13 nonresponders. No differences in mean CVP and PCWP values between the responders and the nonresponders were found. The only parameter associated with a significant response to volume infusion was the ratio of the a/v waves of the PCWP tracing (p = 0.0001). The performance of the a/v wave ratio>1 of the PCWP tracing in predicting fluid responsiveness was evaluated by constructing a receiver operating characteristic curve. The area under the receiver operating characteristic curve was 0.89 (95% confidence interval, 0.79-0.99; p<0.05).

CONCLUSIONS

The a/v ratio measured on the PCWP tracing is a predictor of fluid responsiveness in patients with preserved left ventricular function undergoing coronary artery bypass grafting.

Pulse pressure variation and stroke volume variation to predict fluid responsiveness in patients undergoing carotid endarterectomy

Background

During carotid endarterectomy (CEA), hemodynamic stability and adequate fluid management are crucial to prevent perioperative cerebral stroke, myocardial infarction and hyperperfusion syndrome. Both pulse pressure variation (PPV) and stroke volume variation (SVV), dynamic preload indices derived from the arterial waveform, are increasingly advocated as predictors of fluid responsiveness in mechanically ventilated patients. The aim of this study was to evaluate the accuracy of PPV and SVV for predicting fluid responsiveness in patients undergoing CEA.

Methods

Twenty seven patients undergoing CEA were enrolled in this study. PPV, SVV and cardiac output (CO) were measured before and after fluid loading of 500 ml of hydroxyethyl starch solution. Fluid responsiveness was defined as an increase in CO ≥ 15%. The ability of PPV and SVV to predict fluid responsiveness was assessed using receiver operating characteristic (ROC) analysis.

Results

Both PPV and SVV measured before fluid loading are associated with changes in CO caused by fluid expansion. The ROC analysis showed that PPV and SVV predicted response to volume loading (area under the ROC curve = 0.854 and 0.841, respectively, P < 0.05). A PPV ≥ 9.5% identified responders (Rs) with a sensitivity of 71.4% and a specificity of 90.9%, and a SVV ≥ 7.5% identified Rs with a sensitivity of 92.9% and a specificity of 63.6%.

Conclusions

Both PPV and SVV values before volume loading are associated with increased CO in response to volume expansion. Therefore, PPV and SVV are useful predictors of fluid responsiveness in patients undergoing CEA.

Predicting fluid responsiveness during infrarenal aortic cross-clamping in pigs

OBJECTIVE

Infrarenal aortic cross-clamping (ACC) induces hemodynamic disturbances that may affect respiratory-induced variations in stroke volume and, therefore, affect the ability of dynamic parameters such as pulse-pressure variation (PPV) to predict fluid responsiveness. Since this issue has not been investigated yet to authors' knowledge, the hypothesis was tested that ACC may change PPV and impair its ability to predict fluid responsiveness.

DESIGN

Prospective laboratory experiment.

SETTING

A university research laboratory.

PARTICIPANTS

Nineteen anesthetized and mechanically ventilated pigs.

INTERVENTIONS

Two courses of volume expansion were performed using 500 mL of saline before and during ACC. Animals were monitored using a systemic arterial catheter, and a pulmonary arterial catheter (stroke volume, central venous pressure, pulmonary arterial occlusion pressure). Animals were defined as responders to volume expansion if stroke volume increased ≥ 15%.

RESULTS

Before ACC, 13 animals were responders. Fluid responsiveness was predicted by a PPV ≥ 14% with a sensitivity of 77% (95% CI = 46%-95%) and a specificity of 83% (95% CI = 36%-97%). The area under the receiver operating characteristic curve was 0.90(95% CI = 0.67-0.99) and was higher than those generated for central venous pressure and pulmonary arterial occlusion pressure. ACC induced an increase in PPV (p<0.0005). During ACC, 8 animals were responders. An 18% PPV threshold discriminated between responders and non-responders to volume expansion, with a sensitivity of 87% (95% CI = 47%-98%) and a specificity of 54% (95% CI = 23%-83%). The area under the receiver operating characteristic curve was 0.72 (95% CI = 0.47-0.90) and was not different from those generated for central venous pressure and pulmonary arterial occlusion pressure.

CONCLUSIONS

ACC induced a significant increase in PPV and reduced its ability to predict fluid responsiveness.

Does the central venous pressure predict fluid responsiveness? An updated meta-analysis and a plea for some common sense

BACKGROUND

Despite a previous meta-analysis that concluded that central venous pressure should not be used to make clinical decisions regarding fluid management, central venous pressure continues to be recommended for this purpose.

AIM

To perform an updated meta-analysis incorporating recent studies that investigated indices predictive of fluid responsiveness. A priori subgroup analysis was planned according to the location where the study was performed (ICU or operating room).

DATA SOURCES

MEDLINE, EMBASE, Cochrane Register of Controlled Trials, and citation review of relevant primary and review articles.

STUDY SELECTION

Clinical trials that reported the correlation coefficient or area under the receiver operating characteristic curve (AUC) between the central venous pressure and change in cardiac performance following an intervention that altered cardiac preload. From 191 articles screened, 43 studies met our inclusion criteria and were included for data extraction. The studies included human adult subjects, and included healthy controls (n = 1) and ICU (n = 22) and operating room (n = 20) patients.

DATA EXTRACTION

Data were abstracted on study characteristics, patient population, baseline central venous pressure, the correlation coefficient, and/or the AUC between central venous pressure and change in stroke volume index/cardiac index and the percentage of fluid responders. Meta-analytic techniques were used to summarize the data.

DATA SYNTHESIS

Overall 57% ± 13% of patients were fluid responders. The summary AUC was 0.56 (95% CI, 0.54-0.58) with no heterogenicity between studies. The summary AUC was 0.56 (95% CI, 0.52-0.60) for those studies done in the ICU and 0.56 (95% CI, 0.54-0.58) for those done in the operating room. The summary correlation coefficient between the baseline central venous pressure and change in stroke volume index/cardiac index was 0.18 (95% CI, 0.1-0.25), being 0.28 (95% CI, 0.16-0.40) in the ICU patients, and 0.11 (95% CI, 0.02-0.21) in the operating room patients.

CONCLUSIONS

There are no data to support the widespread practice of using central venous pressure to guide fluid therapy. This approach to fluid resuscitation should be abandoned.

Severe pre-eclampsia and hypertensive crises

Hypertensive disorders of pregnancy are one of the leading causes of peripartum morbidity and mortality globally. Hypertensive disease in pregnancy is associated with a spectrum of severity, ranging from mild pregnancy-induced hypertension to eclampsia. Although most cases of pre-eclampsia may be managed successfully, severe pre-eclampsia is a life-threatening multisystem disease associated with eclampsia, HELLP (haemolysis, elevated liver enzymes, low platelets) syndrome, acute kidney injury, pulmonary oedema, placental abruption and intrauterine foetal death. Management of severe pre-eclampsia includes identification of high-risk patients, optimisation of antenatal care, early intervention and the identification and early management of complications. In the first instance, oral anti-hypertensive agents, including labetalol, nifedipine and methyldopa, should be tried. If oral anti-hypertensive agents have failed to adequately control blood pressure, intravenous anti-hypertensives should be considered. Commonly used intravenous anti-hypertensives include labetalol, hydralazine and glyceryl trinitrate. In addition to anti-hypertensive agents, close attention should be given to regular clinical examination, assessment of fluid balance, neurologic status and monitoring of other vital signs. Magnesium sulphate should be considered early to prevent seizures. Delivery of the baby is the definitive management of severe pre-eclampsia.

A protocol for resuscitation of severe burn patients guided by transpulmonary thermodilution and lactate levels: a 3-year prospective cohort study

Introduction

The use of urinary output and vital signs to guide initial burn resuscitation may lead to suboptimal resuscitation. Invasive hemodynamic monitoring may result in over-resuscitation. This study aimed to evaluate the results of a goal-directed burn resuscitation protocol that used standard measures of mean arterial pressure (MAP) and urine output, plus transpulmonary thermodilution (TPTD) and lactate levels to adjust fluid therapy to achieve a minimum level of preload to allow for sufficient vital organ perfusion.

Methods

We conducted a three-year prospective cohort study of 132 consecutive critically burned patients. These patients underwent resuscitation guided by MAP (>65 mmHg), urinary output (0.5 to 1 ml/kg), TPTD and lactate levels. Fluid therapy was adjusted to achieve a cardiac index (CI) >2.5 L/minute/m² and an intrathoracic blood volume index (ITBVI) >600 ml/m², and to optimize lactate levels. Statistical analysis was performed using mixed models. We also used Pearson or Spearman methods and the Mann-Whitney U-test.

Results

A total of 98 men and 34 women (mean age, 48 ± 18 years) was studied. The mean total body surface area (TBSA) burned was 35% ± 22%. During the early resuscitation phase, lactate levels were elevated (2.58 ± 2.05 mmol/L) and TPTD showed initial hypovolemia by the CI (2.68 ± 1.06 L/minute/m²) and the ITBVI (709 ± 254 mL/m²). At 24 to 32 hours, the CI and lactic levels were normalized, although the ITBVI remained below the normal range (744 ± 276 ml/m²). The mean fluid rate required to achieve protocol targets in the first 8 hours was 4.05 ml/kg/TBSA burned, which slightly increased in the next 16 hours. Patients with a urine output greater than or less than 0.5 ml/kg/hour did not show differences in heart rate, mean arterial pressure, CI, ITBVI or lactate levels.

Conclusions

Initial hypovolemia may be detected by TPTD monitoring during the early resuscitation phase. This hypovolemia might not be reflected by blood pressure and hourly urine output. An adequate CI and tissue perfusion can be achieved with below-normal levels of preload. Early resuscitation guided by lactate levels and below-normal preload volume targets appears safe and avoids unnecessary fluid input.

The role for invasive monitoring in acute lung injury

Because acute lung injury (ALI) may arise from diverse and heterogeneous clinical insults, monitoring strategies for patients with ALI are heterogeneous as well. This review divides the monitoring strategies for ALI into three distinct phases. The "at-risk phase" is the period in which patients are at risk for ALI, and interventions may be applied to minimize or eliminate this risk. The "ALI phase" is the period during which ALI has occurred and requires attentive clinical management. The "resolution phase" is the period defined by resolution of ALI and successful discontinuation of mechanical ventilation. These phases are arbitrary, but they provide a useful framework for discussing the temporal changes in patient condition and monitoring goals in ALI.Invasive hemodynamic monitoring has specific roles in each phase of therapy for patients with ALI: pre-ALI, peri-ALI, and post-ALI. The primary goals are to optimize fluid resuscitation to prevent organ dysfunction, including ALI, and if ALI occurs to additional optimize fluid balance vis-à-vis the lung. By judicious application of invasive hemodynamic monitoring, particularly in its more modern iterations, clinicians can optimize the ebb and flow phases common to critically ill patients. This is vitally important given our current and growing understanding of the relationship between fluid balance and important clinical outcomes, multiple organ dysfunction syndrome, and mortality.

Safety of off-label erythropoiesis stimulating agents in critically ill patients: a meta-analysis

PURPOSE

Erythropoiesis stimulating agents (ESAs) are used to treat anemia in critically ill patients. This indication is off-label, because it is not licensed by regulatory authorities. Recently ESAs were suspected to harm critically ill patients. Our objective was to assess the safety of ESAs in off-label indications in critically ill patients.

METHODS

Eleven databases were searched up to April 2012. We considered randomized controlled trials (RCTs) and controlled observational studies in any language that compared off-label ESAs treatment with other effective interventions, placebo or no treatment in critically ill patients. Two authors independently screened and evaluated retrieved records, extracted data and assessed risk of bias and quality of reporting.

RESULTS

We used frequentist and Bayesian models to combine studies, and performed sensitivity and subgroup analyses. From 12,888 citations, we included 48 studies (34 RCTs; 14 observational), involving 944,856 participants. Harm reporting was of medium to low quality. There was no statistically significant increased risk of adverse events in general, serious adverse events, the most frequently reported adverse events, and death in critically ill patients treated with ESAs. These results were robust against risk of bias and analysis methods. There is evidence that ESAs increase the risk of clinically relevant thrombotic vascular events, and there is some less certain evidence that ESAs might increase the risk for venous thromboembolism.

CONCLUSIONS

In critically ill patients, administration of ESAs is associated with a significant increase in clinically relevant thrombotic vascular events but not with other frequently reported adverse events and death.

Noninvasive assessment of hemodynamic response to a fluid challenge using femoral Doppler in critically ill ventilated patients

PURPOSE

The purpose of the study is to determine if femoral artery blood flow Doppler parameters can assess cardiac response to a fluid challenge (FC).

MATERIALS AND METHODS

We prospectively recorded in 52 critically ill ventilated patients' velocity time integral variation (%VTIf) and maximal systolic velocity variation (%Vfmax) derived from femoral Doppler analysis and aortic velocity time integral variation registered on transthoracic echocardiography before and after an FC of 500-mL saline.

RESULTS

According to Pearson coefficient, %Vfmax and %VTIf were found to be positively correlated with aortic velocity time integral variation (r(2) = 0.46 and 0.51, respectively; P < .0001) and were significantly different between responder patients and nonresponders (11% ± 3.4% vs 5.9% ± 4.3% and 14.9% ± 4.2% vs 5.5% ± 5.5%, respectively; P < .0001). Increase of %VTIf 10% or higher and %Vfmax 7% or higher after an FC showed a sensitivity of 80% and 84%, a specificity of 85% and 73%, and an area under the curve of 0.905 and 0.851, respectively, for discriminating responder and nonresponder patients.

CONCLUSION

Variation of femoral Doppler parameters before and after FC mirrors cardiac response to fluid loading. This tool could be considered as an alternative to transthoracic echocardiography in case of poor thoracic insonation.

Current practice in hemodynamic monitoring and management in high-risk surgery patients: a national survey of Korean anesthesiologists

Background

Hemodynamic optimization improves postoperative outcomes in high-risk surgery patients. The monitoring of cardiac output (CO) and dynamic parameters of fluid responsiveness can guide hemodynamic optimization. We conducted a survey to assess the current hemodynamic monitoring and management practices of Korean anesthesiologists during high-risk surgery.

Methods

E-mails containing a link to our survey, which consisted of 33 questions relating to hemodynamic monitoring during high-risk surgery, were sent to 3,943 members of the Korean Society of Anesthesiologists (KSA). The survey web page was open from December 30, 2011 to March 31, 2012.

Results

A total of 139 anesthesiologists responded during the survey period. Invasive arterial pressure (97.2%) and central venous pressure (93.4%) were routinely monitored. CO was monitored in 58.5% of patients; stroke volume variations were monitored in 50.9% of patients. However, CO was consistently optimized by < 20% of anesthesiologists. An arterial pressure waveform-derived CO monitor was the most frequently used device to monitor CO (79.0%). Blood pressure, urine output, central venous pressure, and clinical experience were considered to be the best indicators of volume expansion than CO or dynamic parameters of fluid responsiveness.

Conclusions

The survey revealed that KSA members frequently monitor CO and dynamic parameters of fluid responsiveness during high-risk surgery. However, static indices were used more often to judge volume expansion. The current study reveals that CO is not frequently optimized despite the relatively high incidence of CO monitoring during high-risk surgery in Korea.

Changes in the mean systemic filling pressure during a fluid challenge in postsurgical intensive care patients

PURPOSE

The difference between mean systemic filling (Pmsf) and central venous pressure (CVP) is the venous return gradient (dVR). The aim of this study is to assess the significance of the Pmsf analogue (Pmsa) and the dVR during a fluid challenge.

METHODS

We performed a prospective observational study in postsurgical patients. Patients were monitored with a central venous catheter, a LiDCO™plus and the Navigator™. A 250-ml intravenous fluid challenge was given over 5 min. A positive response to the fluid challenge was defined as either a stroke volume (SV) or cardiac output increase of greater than 10 %.

RESULTS

A total of 101 fluid challenges were observed in 39 patients. In 43 events (42.6 %) the SV and CO increased by more than 10 %. Pmsa increased similarly during a fluid challenge in responders and non-responders (3.1 ± 1.9 vs. 3.1 ± 1.8, p = 0.9), whereas the dVR increased in responders (1.16 ± 0.8 vs. 0.2 ± 1, p < 0.001) as among non-responders CVP increased along with Pmsa (2.9 ± 1.7 vs. 3.1 ± 1.8, p = 0.15). Resistance to venous return did not change immediately after a fluid challenge. Heart performance (Eh) decreased significantly among non-responders (0.41 ± 0.15 vs. 0.34 ± 0.13, p < 0.001) whereas among responders it did not change when compared with baseline value (0.35 ± 0.15 vs. 0.34 ± 0.12, p = 0.15).

CONCLUSIONS

The changes in Pmsa and dVR measured at the bedside during a fluid challenge are consistent with the cardiovascular model described by Guyton.

Applying dynamic parameters to predict hemodynamic response to volume expansion in spontaneously breathing patients with septic shock

Volume expansion is a mainstay of therapy in septic shock, although its effect is difficult to predict using conventional measurements. Dynamic parameters, which vary with respiratory changes, appear to predict hemodynamic response to fluid challenge in mechanically ventilated, paralyzed patients. Whether they predict response in patients who are free from mechanical ventilation is unknown. We hypothesized that dynamic parameters would be predictive in patients not receiving mechanical ventilation. This is a prospective, observational, pilot study. Patients with early septic shock and who were not receiving mechanical ventilation received 10-mL/kg volume expansion (VE) at their treating physician's discretion after initial resuscitation in the emergency department. We used transthoracic echocardiography to measure vena cava collapsibility index and aortic velocity variation before VE. We used a pulse contour analysis device to measure stroke volume variation (SVV). Cardiac index was measured immediately before and after VE using transthoracic echocardiography. Hemodynamic response was defined as an increase in cardiac index 15% or greater. Fourteen patients received VE, five of whom demonstrated a hemodynamic response. Vena cava collapsibility index and SVV were predictive (area under the curve = 0.83, 0.92, respectively). Optimal thresholds were calculated: vena cava collapsibility index, 15% or greater (positive predictive value, 62%; negative predictive value, 100%; P = 0.03); SVV, 17% or greater (positive predictive value 100%, negative predictive value 82%, P = 0.03). Aortic velocity variation was not predictive. Vena cava collapsibility index and SVV predict hemodynamic response to fluid challenge patients with septic shock who are not mechanically ventilated. Optimal thresholds differ from those described in mechanically ventilated patients.

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.