Respiratory variations in right atrial pressure predict the response to fluid challenge

Estimation of the transpulmonary pressure from the central venous pressure in mechanically ventilated patients

Transpulmonary pressure (PL) calculation requires esophageal pressure (PES) as a surrogate of pleural pressure (Ppl), but its calibration is a cumbersome technique. Central venous pressure (CVP) swings may reflect tidal variations in Ppl and could be used instead of PES, but the interpretation of CVP waveforms could be difficult due to superposition of heartbeat-induced pressure changes. Thus, we developed a digital filter able to remove the cardiac noise to obtain a filtered CVP (f-CVP). The aim of the study was to evaluate the accuracy of CVP and filtered CVP swings (ΔCVP and Δf-CVP, respectively) in estimating esophageal respiratory swings (ΔPES) and compare PL calculated with CVP, f-CVP and PES; then we tested the diagnostic accuracy of the f-CVP method to identify unsafe high PL levels, defined as PL>10 cmH2O. Twenty patients with acute respiratory failure (defined as PaO2/FiO2 ratio below 200 mmHg) treated with invasive mechanical ventilation and monitored with an esophageal balloon and central venous catheter were enrolled prospectively. For each patient a recording session at baseline was performed, repeated if a modification in ventilatory settings occurred. PES, CVP and airway pressure during an end-inspiratory and -expiratory pause were simultaneously recorded; CVP, f-CVP and PES waveforms were analyzed off-line and used to calculate transpulmonary pressure (PLCVP, PLf-CVP, PLPES, respectively). Δf-CVP correlated better than ΔCVP with ΔPES (r = 0.8, p = 0.001 vs. r = 0.08, p = 0.73), with a lower bias in Bland Altman analysis in favor of PLf-CVP (mean bias - 0.16, Limits of Agreement (LoA) -1.31, 0.98 cmH2O vs. mean bias - 0.79, LoA - 3.14, 1.55 cmH2O). Both PLf-CVP and PLCVP correlated well with PLPES (r = 0.98, p < 0.001 vs. r = 0.94, p < 0.001), again with a lower bias in Bland Altman analysis in favor of PLf-CVP (0.15, LoA - 0.95, 1.26 cmH2O vs. 0.80, LoA - 1.51, 3.12, cmH2O). PLf-CVP discriminated high PL value with an area under the receiver operating characteristic curve 0.99 (standard deviation, SD, 0.02) (AUC difference = 0.01 [-0.024; 0.05], p = 0.48). In mechanically ventilated patients with acute respiratory failure, the digital filtered CVP estimated ΔPES and PL obtained from digital filtered CVP represented a reliable value of standard PL measured with the esophageal method and could identify patients with non-protective ventilation settings.

Pleth variability index during preoxygenation could predict anesthesia-induced hypotension: A prospective, observational study

STUDY OBJECTIVE

To determine whether changes in the pleth variability index (PVi) during preoxygenation with forced ventilation for 1 min could predict anesthesia-induced hypotension.

DESIGN

Prospective, observational study.

SETTING

A tertiary teaching hospital.

PATIENTS

Ninety-six patients who underwent general anesthesia using total intravenous anesthesia were enrolled.

INTERVENTIONS

Upon the patient's arrival at the preoperative waiting area, a PVi sensor was affixed to their fourth fingertip. For preoxygenation, forced ventilation of 8 breaths/min in a 1:2 inspiratory-expiratory ratio was conducted using the guidance of an audio file. One minute after preoxygenation, anesthetic administration was initiated. Blood pressure was measured for the next 15 min.

MEASUREMENTS

We calculated the difference (dPVi) and percentage of change (%PVi) between the PVi values immediately before and after forced ventilation. Anesthesia-induced hypotension was defined as a mean arterial pressure of <60 mmHg within 15 min after the infusion of anesthetics.

MAIN RESULTS

Overall, 87 patients were included in the final analysis. Anesthesia-induced hypotension occurred in 31 (35.6%) of the 87 patients. Receiver operating characteristic curve analyses identified a cut-off value of -2 for dPVi, with an area under the curve of 0.691 (95% confidence interval [CI], 0.564-0.818; P < 0.001) and a cut-off value of -7.6% for %PVi, with an area under the curve of 0.711 (95% CI, 0.589-0.832; P < 0.001). Further, multivariate logistic regression analysis showed that a low %PVi with an odds ratio of 9.856 (95% CI, 3.131-31.032; P < 0.001) was a significant determinant of anesthesia-induced hypotension.

CONCLUSIONS

Hypotension frequently occurs during general anesthesia induction and can impact outcomes. Additionally, the percentage change in the PVi before and after preoxygenation using deep breathing can be used to predict anesthesia-induced hypotension.

Cardiopulmonary interactions-which monitoring tools to use?

Heart-lung interactions occur due to the mechanical influence of intrathoracic pressure and lung volume changes on cardiac and circulatory function. These interactions manifest as respiratory fluctuations in venous, pulmonary, and arterial pressures, potentially affecting stroke volume. In the context of functional hemodynamic monitoring, pulse or stroke volume variation (pulse pressure variation or stroke volume variability) are commonly employed to assess volume or preload responsiveness. However, correct interpretation of these parameters requires a comprehensive understanding of the physiological factors that determine pulse pressure and stroke volume. These factors include pleural pressure, venous return, pulmonary vessel function, lung mechanics, gas exchange, and specific cardiac factors. A comprehensive knowledge of heart-lung physiology is vital to avoid clinical misjudgments, particularly in cases of right ventricular (RV) failure or diastolic dysfunction. Therefore, when selecting monitoring devices or technologies, these factors must be considered. Invasive arterial pressure measurements of variations in breath-to-breath pressure swings are commonly used to monitor heart-lung interactions. Echocardiography or pulmonary artery catheters are valuable tools for differentiating preload responsiveness from right ventricular failure, while changes in diastolic function should be assessed alongside alterations in airway or pleural pressure, which can be approximated by esophageal pressure. In complex clinical scenarios like ARDS, combined forms of shock or right heart failure, additional information on gas exchange and pulmonary mechanics aids in the interpretation of heart-lung interactions. This review aims to describe monitoring techniques that provide clinicians with an integrative understanding of a patient's condition, enabling accurate assessment and patient care.

Pulse Pressure Variation-Based Intraoperative Fluid Management Versus Traditional Fluid Management for Colon Cancer Patients Undergoing Open Mass Resection and Anastomosis: A Randomized Controlled Trial

Background

Bowel edema leads to decreased perfusion and oxygenation of the intestine at the anastomotic site after colonic mass resection with failure of healing and leakage. Additionally, dehydration causes bowel hypoperfusion and difficulty healing with more complications. Fluid therapy guided by dynamic monitoring of fluid response can help avoid bowel dehydration and edema with fewer complications.

Objectives

The main goal of this study was to compare the effects of intraoperative fluid therapy based on pulse pressure variation (PPV) to traditional fluid therapy to maintain adequate hydration without intraoperative instability of hemodynamics and postoperative complications.

Methods

This randomized controlled study was conducted on 90 adult patients (age range: 18-70 years) undergoing elective open colonic mass resection and anastomosis at Eldemerdash Hospital, Ain Shams University, Cairo, Egypt. There were two groups of patients, namely group A (n = 45; conventional fluid management [CFM] group) and group B (n = 45; goal-guided fluid management [GGFM] group based on PPV), using randomly generated data from a computer. Intraoperative fluids and vasopressors were given using GGFM or routine care. The key tool for directing hemodynamic management in the GGFM algorithm was the fluid protocol and PPV. As a result, the outcomes were measured to include the volume of intraoperative fluid, water fraction, and postoperative complications.

Results

In this study, 90 patients underwent analysis. Both groups' demographics were similar (P > 0.05). Baseline characteristics and surgical procedures did not differ significantly between the two groups (P > 0.05). Both the amount of urine output and the intraoperative administration of crystalloids were statistically significantly higher in group A (P < 0.05). The two groups' heart rate, mean arterial pressure and intraoperative usage of colloids and ephedrine were not statistically different (P > 0.05). Water fraction, bowel recovery, anastomotic leak, and length of hospital stay were significantly higher in the CFM group (P < 0.05).

Conclusions

For patients with the American Society of Anesthesiologists physical status I - II undergoing elective open resection of colonic mass and anastomosis, PPV-based GGFM, a less invasive tool for intraoperative fluid management, might be a better option than CFM.

RESPIRATION-RELATED VARIATIONS IN CENTRAL VENOUS PRESSURE AS PREDICTORS OF FLUID RESPONSIVENESS IN SPONTANEOUSLY BREATHING PATIENTS

ABSTRACT

Objective : The hemodynamic parameters used to accurately predict fluid responsiveness (FR) in spontaneously breathing patients (SB) require specific material and expertise. Measurements of the central venous pressure (CVP) are relatively simple and, importantly, are feasible in many critically ill patients. We analyzed the accuracy of respiration-related variations in CVP (vCVP) to predict FR in SB patients and examined the optimization of its measurement using a standardized, deep inspiratory maneuver. Patients and Methods : We performed a monocentric, prospective, diagnostic evaluation. Spontaneously breathing patients in intensive care units with a central venous catheter were prospectively included. The vCVP was measured while the patient was spontaneously breathing, both with (vCVP-st) and without (vCVP-ns) a standardized inspiratory maneuver, and calculated as: Minimum inspiratory v-wave peak pressure - Maximum expiratory v-wave peak pressure. A passive leg raising-induced increase in the left ventricular outflow tract velocity-time integral ≥10% defined FR. Results : Among 63 patients, 38 (60.3%) presented FR. The vCVP-ns was not significantly different between responders and nonresponders (-4.9 mm Hg [-7.5 to -3.1] vs. -4.1 mm Hg [-5.4 to 2.8], respectively; P = 0.15). The vCVP-st was lower in responders than nonresponders (-9.7 mm Hg [-13.9 to -6.2] vs. -3.6 mm Hg [-10.6 to -1.6], respectively; P = 0.004). A vCVP-st < -4.7 mm Hg predicted FR with 89.5% sensitivity, a specificity of 56.0%, and an area under the receiver operating characteristic curve of 0.72 (95% CI, 0.58 to 0.86) ( P = 0.004). Conclusion : When a central venous catheter is present, elevated values for vCVP-st may be useful to identify spontaneously breathing patients unresponsive to volume expansion. Nevertheless, the necessity of performing a standardized, deep-inspiration maneuver may limit its clinical application.

Prognostic Value of Respiratory Variation in Right Atrial Pressure in Patients With Precapillary Pulmonary Hypertension

BACKGROUND

Precapillary pulmonary hypertension is characterized by elevated mean pulmonary artery pressure from increased pulmonary vascular resistance. Lack of respiratory variation in right atrial pressure can be viewed as a surrogate for severe pulmonary hypertension and inability of the right ventricle to tolerate preload augmentation during inspiration.

RESEARCH QUESTION

Is the lack of respiratory variation in right atrial pressure predictive of right ventricular dysfunction and worse clinical outcomes in precapillary pulmonary hypertension?

STUDY DESIGN AND METHODS

We retrospectively reviewed right atrial pressure tracings of patients with precapillary pulmonary hypertension who underwent right heart catheterization. Patients with respiratory variation in right atrial pressure (end expiratory-end inspiratory) ≤ 2 mm Hg were considered to have effectively no meaningful variation in right atrial pressure.

RESULTS

Lack of respiratory variation in right atrial pressure was associated with lower cardiac index by indirect Fick (2.34 ± 0.09 vs 2.76 ± 0.1 L/min/m2; P = .001), lower pulmonary artery saturation (60% ± 1.02% vs 64% ± 1.15%; P = .007), higher pulmonary vascular resistance (8.9 ± 0.44 vs 6.1 ± 0.49 Wood units, P < .0001), right ventricular dysfunction on echocardiography (87.3% vs 38.8%; P < .0001), higher pro brain natriuretic peptide (2,163 ± 2,997 vs 633 ± 402 ng/mL; P < .0001), and more hospitalizations within 1 year for right ventricular failure (65.4% vs 29.6%; P < .0001). There was also a trend toward higher mortality at 1 year in patients with no respiratory variation in right atrial pressure (25.4% vs 11.1%; P = .06).

INTERPRETATION

Lack of respiratory variation in right atrial pressure is associated with poor clinical outcomes, adverse hemodynamic parameters, and right ventricular dysfunction in patients with precapillary pulmonary hypertension. Larger studies are needed to further evaluate its utility in prognosis and potential risk stratification in patients with precapillary pulmonary hypertension.

Right Ventricular Limitation: A Tale of Two Elastances

Right ventricular (RV) dysfunction is a commonly considered cause of low cardiac output in critically ill patients. Its management can be difficult and requires an understanding of how the RV limits cardiac output. We explain that RV stroke output is caught between the passive elastance of the RV walls during diastolic filling and the active elastance produced by the RV in systole. These two elastances limit RV filling and stroke volume and consequently limit left ventricular stroke volume. We emphasize the use of the term "RV limitation" and argue that limitation of RV filling is the primary pathophysiological process by which the RV causes hemodynamic instability. Importantly, RV limitation can be present even when RV function is normal. We use the term "RV dysfunction" to indicate that RV end-systolic elastance is depressed or diastolic elastance is increased. When RV dysfunction is present, RV limitation occurs at lowerpulmonary valve opening pressures and lower stroke volume, but stroke volume and cardiac output still can be maintained until RV filling is limited. We use the term "RV failure" to indicate the condition in which RV output is insufficient for tissue needs. We discuss the physiological underpinnings of these terms and implications for clinical management.

Right ventricular and pulmonary artery pulse pressure variation and systolic pressure variation for the prediction of fluid responsiveness: an interventional study in coronary artery bypass surgery patients

PURPOSE

Predicting fluid responsiveness is essential when treating surgical or critically ill patients. When using a pulmonary artery catheter, pulse pressure variation and systolic pressure variation can be calculated from right ventricular and pulmonary artery pressure waveforms.

METHODS

We conducted a prospective interventional study investigating the ability of right ventricular pulse pressure variation (PPV_RV) and systolic pressure variation (SPV_RV) as well as pulmonary artery pulse pressure variation (PPV_PA) and systolic pressure variation (SPV_PA) to predict fluid responsiveness in coronary artery bypass (CABG) surgery patients. Additionally, radial artery pulse pressure variation (PPV_ART) and systolic pressure variation (SPV_ART) were calculated. The area under the receiver operating characteristics (AUROC) curve with 95%-confidence interval (95%-CI) was used to assess the capability to predict fluid responsiveness (defined as an increase in cardiac index of > 15%) after a 500 mL crystalloid fluid challenge.

RESULTS

Thirty-three patients were included in the final analysis. Thirteen patients (39%) were fluid-responders with a mean increase in cardiac index of 25.3%. The AUROC was 0.60 (95%-CI 0.38 to 0.81) for PPV_RV, 0.63 (95%-CI 0.43 to 0.83) for SPV_RV, 0.58 (95%-CI 0.38 to 0.78) for PPV_PA, and 0.71 (95%-CI 0.52 to 0.89) for SPV_PA. The AUROC for PPV_ART was 0.71 (95%-CI 0.53 to 0.89) and for SPV_ART 0.78 (95%-CI 0.62 to 0.94). The correlation between pulse pressure variation and systolic pressure variation measurements derived from the different waveforms was weak.

CONCLUSIONS

Right ventricular and pulmonary artery pulse pressure variation and systolic pressure variation seem to be weak predictors of fluid responsiveness in CABG surgery patients.

Prediction of fluid responsiveness. What’s new?

Although the administration of fluid is the first treatment considered in almost all cases of circulatory failure, this therapeutic option poses two essential problems: the increase in cardiac output induced by a bolus of fluid is inconstant, and the deleterious effects of fluid overload are now clearly demonstrated. This is why many tests and indices have been developed to detect preload dependence and predict fluid responsiveness. In this review, we take stock of the data published in the field over the past three years. Regarding the passive leg raising test, we detail the different stroke volume surrogates that have recently been described to measure its effects using minimally invasive and easily accessible methods. We review the limits of the test, especially in patients with intra-abdominal hypertension. Regarding the end-expiratory occlusion test, we also present recent investigations that have sought to measure its effects without an invasive measurement of cardiac output. Although the limits of interpretation of the respiratory variation of pulse pressure and of the diameter of the vena cava during mechanical ventilation are now well known, several recent studies have shown how changes in pulse pressure variation itself during other tests reflect simultaneous changes in cardiac output, allowing these tests to be carried out without its direct measurement. This is particularly the case during the tidal volume challenge, a relatively recent test whose reliability is increasingly well established. The mini-fluid challenge has the advantage of being easy to perform, but it requires direct measurement of cardiac output, like the classic fluid challenge. Initially described with echocardiography, recent studies have investigated other means of judging its effects. We highlight the problem of their precision, which is necessary to evidence small changes in cardiac output. Finally, we point out other tests that have appeared more recently, such as the Trendelenburg manoeuvre, a potentially interesting alternative for patients in the prone position.

Inferior Vena Cava Collapsibility Index: Clinical Validation and Application for Assessment of Relative Intravascular Volume

Accurate assessment of relative intravascular volume is critical to guide volume management of patients with acute or chronic kidney disorders, particularly those with complex comorbidities requiring hospitalization or intensive care. Inferior vena cava (IVC) diameter variability with respiration measured by ultrasound provides a dynamic noninvasive point-of-care estimate of relative intravascular volume. We present details of image acquisition, interpretation, and clinical scenarios to which IVC ultrasound can be applied. The variation in IVC diameter over the respiratory or ventilatory cycle is greater in patients who are volume responsive than those who are not volume responsive. When 2 recent prospective studies of spontaneously breathing patients (n = 214) are added to a prior meta-analysis of 181 patients, for a total of 7 studies of 395 spontaneously breathing patients, IVC collapsibility index (CI) had a pooled sensitivity of 71% and specificity of 81% for predicting volume responsiveness, which is similar to a pooled sensitivity of 75% and specificity of 82% for 9 studies of 284 mechanically ventilated patients. IVC maximum diameter <2.1 cm, that collapses >50% with or without a sniff is inconsistent with intravascular volume overload and suggests normal right atrial pressure (0-5 mmHg). Inferior vena cava collapsibility (IVC CI) < 20% with no sniff suggests increased right atrial pressure and is inconsistent with overt hypovolemia in spontaneously breathing or ventilated patients. These IVC CI cutoffs do not appear to vary greatly depending on whether patients are breathing spontaneously or are mechanically ventilated. Patients with lower IVC CI are more likely to tolerate ultrafiltration with hemodialysis or improve cardiac output with ultrafiltration. Our goal for IVC CI generally ranges from 20% to 50%, respecting potential biases to interpretation and overriding clinical considerations. IVC ultrasound may be limited by factors that affect IVC diameter or collapsibility, clinical interpretation, or optimal visualization, and must be interpreted in the context of the entire clinical situation.

Measurement site of inferior vena cava diameter affects the accuracy with which fluid responsiveness can be predicted in spontaneously breathing patients: a post hoc analysis of two prospective cohorts

Background

The collapsibility index of the inferior vena cava (cIVC) has potential for predicting fluid responsiveness in spontaneously breathing patients, but a standardized approach for measuring the inferior vena cava diameter has yet to be established.

The aim was to test the accuracy of different measurement sites of inferior vena cava diameter to predict fluid responsiveness in spontaneously breathing patients with sepsis-related circulatory failure and examine the influence of a standardized breathing manoeuvre.

Results

Among the 81 patients included in the study, the median Simplified Acute Physiologic Score II was 34 (24; 42). Sepsis was of pulmonary origin in 49 patients (60%). Median volume expansion during the 24 h prior to study inclusion was 1000 mL (0; 2000). Patients were not severely ill: none were intubated, only 20% were on vasopressors, and all were apparently able to perform a standardized breathing exercise. Forty-one (51%) patients were responders to volume expansion (i.e. a ≥ 10% stroke volume index increase). The cIVC was calculated during non-standardized (cIVC-ns) and standardized breathing (cIVC-st) conditions. The accuracy with which both cIVC-ns and cIVC-st predicted fluid responsiveness differed significantly by measurement site (interaction p < 0.001 and < 0.0001, respectively). Measuring inferior vena cava diameters 4 cm caudal to the right atrium predicted fluid responsiveness with the best accuracy. At this site, a standardized breathing manoeuvre also significantly improved predictive power: areas under ROC curves [mean and (95% CI)] for cIVC-ns = 0.85 [0.78–0.94] versus cIVC-st = 0.98 [0.97–1.0], p < 0.001. When cIVC-ns is superior or equal to 33%, fluid responsiveness is predicted with a sensitivity of 66% and a specificity of 92%. When cIVC-st is superior or equal to 44%, fluid responsiveness is predicted with a sensitivity of 93% and a specificity of 98%.

Conclusion

The accuracy with which cIVC measurements predict fluid responsiveness in spontaneously breathing patients depends on both the measurement site of inferior vena cava diameters and the breathing regime. Measuring inferior vena cava diameters during a standardized inhalation manoeuvre at 4 cm caudal to the right atrium seems to be the method by which to obtain cIVC measurements best-able to predict patients’ response to volume expansion.

Comparison of conventional fluid management with PVI-based goal-directed fluid management in elective colorectal surgery

Intraoperative fluid management is quite important in terms of postoperative organ perfusion and complications. Different fluid management protocols are in use for this purpose. Our primary goal was to compare the effects of conventional fluid management (CFM) with the Pleth Variability Index (PVI) guided goal-directed fluid management (GDFM) protocols on the amount of crystalloids administered, blood lactate, and serum creatinine levels during the intraoperative period. The length of hospital stay was our secondary goal. Seventy ASA I–II elective colorectal surgery patients were randomly assigned to CFM or GDFM for fluid management. The hemodynamic data and the data obtained from ABG were recorded at the end of induction and during the follow-up period at 1 h intervals. In the preoperative period and at 24 h postoperatively, blood samples were taken for the measurement of hemoglobin, Na, K, Cl, serum creatinine, albumin and blood lactate. In the first 24 h after surgery, oliguria and the time of first bowel movement were recorded. Length of hospital stay was also recorded. Intraoperative crystalloid administration and urine output were statistically significantly higher in CFM group (p < 0.001, p: 0.018). The end-surgery fluid balance was significantly lower in Group GDFM. Preoperative and postoperative Na, K, Cl, serum albumin, serum creatinine, lactate and hemoglobin values were similar between the groups. The time to passage of stool was significantly short in Group-GDFM compared to Group-CFM (p = 0.016). The length of hospital stay was found to be similar in both group. PVI-guided GDFM might be an alternative to CFM in ASA I–II patients undergoing elective colorectal surgery. However, further studies need to be carried out to search the efficiency and safety of PVI.

Practical approach to detection and management of acute kidney injury in critically ill patient

Background

Acute kidney injury (AKI) is a common complication in critically ill patients and is associated with high morbidity and mortality. This paper provides a critical review of the etiologies of AKI and a systematic approach toward its diagnosis and management with emphasis on fluid volume assessment and the use of urine biochemical profile and microscopy in identifying the nature and the site of kidney injury.

Materials and methods

The search of PubMed and selection of papers had employed observational designs or randomized control trials relevant to AKI.

Results

AKI is defined by the rate of rise of serum creatinine and a decline in urine output. The pathophysiology is diverse and requires a careful and systematic assessment of predisposing factors and localization of site of injury. The majority of AKIs are due to prerenal causes such as fluid volume deficit, sepsis, or renal as in acute tubular injury. The use of central venous and arterial blood pressure monitoring and inferior vena cava echocardiography complemented by urine analysis and microscopy allows assessment of fluid volume status and AKI etiology.

Conclusions

Timely intervention by avoidance of fluid volume deficit and nephrotoxic agents and blood pressure support can reduce the incidence of AKI in critically ill patients.

Diagnostic Accuracy of the Inferior Vena Cava Collapsibility to Predict Fluid Responsiveness in Spontaneously Breathing Patients With Sepsis and Acute Circulatory Failure

OBJECTIVE

To investigate whether the collapsibility index of the inferior vena cava recorded during a deep standardized inspiration predicts fluid responsiveness in nonintubated patients.

DESIGN

Prospective, nonrandomized study.

SETTING

ICUs at a general and a university hospital.

PATIENTS

Nonintubated patients without mechanical ventilation (n = 90) presenting with sepsis-induced acute circulatory failure and considered for volume expansion.

INTERVENTIONS

We assessed hemodynamic status at baseline and after a volume expansion induced by a 30-minute infusion of 500-mL gelatin 4%.

MEASUREMENTS AND MAIN RESULTS

We measured stroke volume index and collapsibility index of the inferior vena cava under a deep standardized inspiration using transthoracic echocardiography. Vena cava pertinent diameters were measured 15-20 mm caudal to the hepatic vein junction and recorded by bidimensional imaging on a subcostal long-axis view. Standardized respiratory cycles consisted of a deep standardized inspiration followed by passive exhalation. The collapsibility index expressed in percentage equaled the ratio of the difference between end-expiratory and minimum-inspiratory diameter over the end-expiratory diameter. After volume expansion, a relevant (≥ 10%) stroke volume index increase was recorded in 56% patients. In receiver operating characteristic analysis, the area under curve for that collapsibility index was 0.89 (95% CI, 0.82-0.97). When such index is superior or equal to 48%, fluid responsiveness is predicted with a sensitivity of 84% and a specificity of 90%.

CONCLUSIONS

The collapsibility index of the inferior vena cava during a deep standardized inspiration is a simple, noninvasive bedside predictor of fluid responsiveness in nonintubated patients with sepsis-related acute circulatory failure.

Predictors to Intravenous Fluid Responsiveness

Management with intravenous fluids can improve cardiac output in some surgical patients. Management with static preload indicators, such as central venous pressure and pulmonary artery occlusion pressure, has not demonstrated a suitable relationship with changes in the cardiac output induced by intravenous fluid therapy. Dynamic indicators, such as the variability of arterial pulse pressure or stroke volume variation, have demonstrated a suitable relationship. Since improvement in cardiac output does not guarantee an adequate perfusion pressure, in patients with hypotension, it is also necessary to know whether arterial pressure will also increase with intravenous fluid therapy. In this regard, the functional assessment of arterial load by dynamic arterial elastance could help to determine which patients will improve not only their cardiac output but also their mean arterial pressure.

Predictors to Intravenous Fluid Responsiveness

Management with intravenous fluids can improve cardiac output in some surgical patients. Management with static preload indicators, such as central venous pressure and pulmonary artery occlusion pressure, has not demonstrated a suitable relationship with changes in the cardiac output induced by intravenous fluid therapy. Dynamic indicators, such as the variability of arterial pulse pressure or stroke volume variation, have demonstrated a suitable relationship. Since improvement in cardiac output does not guarantee an adequate perfusion pressure, in patients with hypotension, it is also necessary to know whether arterial pressure will also increase with intravenous fluid therapy. In this regard, the functional assessment of arterial load by dynamic arterial elastance could help to determine which patients will improve not only their cardiac output but also their mean arterial pressure.

Focused Real-Time Ultrasonography for Nephrologists

We propose that renal consults are enhanced by incorporating a nephrology-focused ultrasound protocol including ultrasound evaluation of cardiac contractility, the presence or absence of pericardial effusion, inferior vena cava size and collapsibility to guide volume management, bladder volume to assess for obstruction or retention, and kidney size and structure to potentially gauge chronicity of renal disease or identify other structural abnormalities. The benefits of immediate and ongoing assessment of cardiac function and intravascular volume status (prerenal), possible urinary obstruction or retention (postrenal), and potential etiologies of acute kidney injury or chronic kidney disease far outweigh the limitations of bedside ultrasonography performed by nephrologists. The alternative is reliance on formal ultrasonography, which creates a disconnect between those who order, perform, and interpret studies, creates delays between when clinical questions are asked and answered, and may increase expense. Ultrasound-enhanced physical examination provides immediate information about our patients, which frequently alters our assessments and management plans.

Ventilator-induced central venous pressure variation can predict fluid responsiveness in post-operative cardiac surgery patients

BACKGROUND

Ventilator-induced dynamic hemodynamic parameters such as stroke volume variation (SVV) and pulse pressure variation (PPV) have been shown to predict fluid responsiveness in contrast to static hemodynamic parameters such as central venous pressure (CVP). We hypothesized that the ventilator-induced central venous pressure variation (CVPV) could predict fluid responsiveness.

METHODS

Twenty-two elective cardiac surgery patients were studied post-operatively on the intensive care unit during mechanical ventilation with tidal volumes of 6-8 ml/kg without spontaneous breathing efforts or cardiac arrhythmia. Before and after administration of 500mL hydroxyethyl starch, SVV and PPV were measured using pulse contour analysis by modified Modelflow^® , while CVP was obtained from a central venous catheter positioned in the superior vena cava. CVPV was calculated as 100 × (CVP_max -CVP_min )/[(CVP_max + CVP_min) /2].

RESULTS

Nineteen patients (86%) were fluid responders defined as an increase in cardiac output of ≥ 15% after fluid administration. CVPV decreased upon fluid loading in responders, but not in non-responders. Baseline CVP values showed no correlation with a change in cardiac output in contrast to baseline SVV (r = 0.60, P = 0.003), PPV (r = 0.58, P = 0.005), and CVPV (r = 0.63, P = 0.002). Baseline values of SVV > 9% and PPV > 8% could predict fluid responsiveness with a sensitivity of 89% and 95%, respectively, both with a specificity of 100%. Baseline CVPV could identify all fluid responders and non-responders correctly at a cut-off value of 12%. There was no difference between the area under the receiver operating characteristic curves of SVV, PPV, and CVPV.

CONCLUSION

The use of ventilator-induced CVPV could predict fluid responsiveness similar to SVV and PPV in post-operative cardiac surgery patients.

Determinants of the Y Descent and its Usefulness as a Predictor of Ventricular Filling

Our objective was to determine if the magnitude of the Y descent in the central venous pressure tracing could be used to determine which patients have restrictive hemodynamics. To better understand the determinants of the Y descent, we also examined the effects of changes in blood volume, changes in pleural pressure, and respiratory maneuvers on its magnitude. Studies were performed in both humans and dogs. In six anesthetized dogs, we examined the effect on the Y descent in central venous pressure (CVP) of an infusion of normal saline, a decrease in pleural pressure produced by having animals perform a Mueller maneuver, and the combination of a Mueller maneuver and volume loading. Observations were made with the chest closed, chest open, and chest and pericardium open. The state of the chest did not effect the Y descent. The Y descent was only significantly increased when a Mueller maneuver was combined with volume loading. There was a significant inverse relationship between the magnitude of the decrease in esophageal pressure and the Y descent. There was also a linear relationship between the CVP and Y descent. For the human studies, we examined patients undergoing routine cardiac surgery. They were examined during spontaneous breathing before intubation, with positive pressure breathing and closed chest, with positive pressure breathing and open chest, with an open pericardium, with a closed chest and positive pressure breathing postsurgery, and with spontaneous breathing after extubation following surgery. The Y descent was greater in spontaneous breaths postsurgery compared to before surgery, and this was associated with an increase in CVP. However, the magnitude of CVP did not correlate with the magnitude of the Y descent. A restrictive pattern in cardiac filling was identified by a lack of respiratory variation in right atrial pressure during spontaneous breaths. All patients with large Y descents had a restrictive pattern, but many patients with restrictive filling patterns did not have a large Y descent. The magnitude of the Y descent is affected by the volume status, the magnitude and direction of the changes in pleural pressure, and the compliance of the pericardial compartment. A large Y descent indicates a restrictive cardiac state, but a small Y descent does not rule out a restrictive condition because of the many interacting variables.

The comparison of stroke volume variation with central venous pressure in predicting fluid responsiveness in septic patients with acute circulatory failure

Purpose:

The present study was designed to investigate the efficacy of stroke volume variation (SVV) in predicting fluid responsiveness and compare it to traditional measures of volume status assessment like central venous pressure (CVP).

Methods:

Forty-five mechanically ventilated patients in sepsis with acute circulatory failure. Patients were not included when they had atrial fibrillation, other severe arrhythmias, permanent pacemaker, or needed mechanical cardiac support. Furthermore, excluded were patients with hypoxemia and a CVP >12. Patients received volume expansion in the form of 500 ml of 6% hydroxyethyl starch.

Results:

The volume expansion-induced increase in  cardiac index (CI) was >15% in 29 patients (labeled responders) and <15% in 16 patients (labeled nonresponders). Before volume expansion, SVV was higher in responders than in nonresponders. Receiver operating characteristic curves analysis showed that SVV was a more accurate indicator of fluid responsiveness than CVP. Before volume expansion, an SVV value of 13% allowed discrimination between responders and nonresponders with a sensitivity of 78% and a specificity of 89%. Volume expansion-induced changes in CI weakly and positively correlated with SVV before volume expansion. Volume expansion decreased SVV from 18.86 ± 4.35 to 7.57 ± 1.80 and volume expansion-induced changes in SVV moderately correlated with volume expansion-induced changes in CI.

Conclusions:

When predicting fluid responsiveness in mechanically ventilated patients in septic shock, SVV is more effective than CVP. Nevertheless, the overall correlation of baseline SVV with increases in CI remains poor. Trends in SVV, as reflected by decreases with volume replacement, seem to correlate much better with increases in CI.

Assessment of preload and fluid responsiveness in intensive care unit. How good are we?

Early recognition and treatment of acute circulatory failure and tissue hypoperfusion are paramount for improving the odds of survival in critically ill patients. Fluid volume resuscitation is the mainstay intervention in redistributive and hypovolemic shock. Correct identification of a patient who would benefit from fluid administration allows optimization of hemodynamics and avoids ineffective or even deleterious volume expansion that may result in worsening of gas exchange and pulmonary edema in fluid unresponsive patients, in whom inotropic and/or vasopressor support should preferentially be used. The use of dynamic changes in central venous pressure, pulse pressure, and echocardiography for assessment of inferior vena cava diameter variations during respiration allows prediction of fluid volume responsiveness in hemodynamically unstable patients. The use of these bedside approaches and passive leg raising maneuver, which is a reversible and quick fluid volume challenge, allows timely formulation of treatment strategy in patients with shock.

Functional hemodynamic monitoring

Functional hemodynamic monitoring is the assessment of the dynamic interactions of hemodynamic variables in response to a defined perturbation. Recent interest in functional hemodynamic monitoring for the bedside assessment of cardiovascular insufficiency has heightened with the documentation of its accuracy in predicting volume responsiveness using a wide variety of monitoring devices, both invasive and noninvasive, and across multiple patient groups and clinical conditions. However, volume responsiveness, though important, reflects only part of the overall spectrum of functional physiologic variables that can be measured to define the physiologic state and monitor response to therapy.

Consensus on circulatory shock and hemodynamic monitoring. Task force of the European Society of Intensive Care Medicine

OBJECTIVE

Circulatory shock is a life-threatening syndrome resulting in multiorgan failure and a high mortality rate. The aim of this consensus is to provide support to the bedside clinician regarding the diagnosis, management and monitoring of shock.

METHODS

The European Society of Intensive Care Medicine invited 12 experts to form a Task Force to update a previous consensus (Antonelli et al.: Intensive Care Med 33:575-590, 2007). The same five questions addressed in the earlier consensus were used as the outline for the literature search and review, with the aim of the Task Force to produce statements based on the available literature and evidence. These questions were: (1) What are the epidemiologic and pathophysiologic features of shock in the intensive care unit? (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 microcirculation 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? Four types of statements were used: definition, recommendation, best practice and statement of fact.

RESULTS

Forty-four statements were made. The main new statements include: (1) statements on individualizing blood pressure targets; (2) statements on the assessment and prediction of fluid responsiveness; (3) statements on the use of echocardiography and hemodynamic monitoring.

CONCLUSIONS

This consensus provides 44 statements that can be used at the bedside to diagnose, treat and monitor patients with shock.

Brazilian recommendations of mechanical ventilation 2013. Part 2

Perspectives on invasive and noninvasive ventilatory support for critically ill patients are evolving, as much evidence indicates that ventilation may have positive effects on patient survival and the quality of the care provided in intensive care units in Brazil. For those reasons, the Brazilian Association of Intensive Care Medicine (Associação de Medicina Intensiva Brasileira - AMIB) and the Brazilian Thoracic Society (Sociedade Brasileira de Pneumologia e Tisiologia - SBPT), represented by the Mechanical Ventilation Committee and the Commission of Intensive Therapy, respectively, decided to review the literature and draft recommendations for mechanical ventilation with the goal of creating a document for bedside guidance as to the best practices on mechanical ventilation available to their members. The document was based on the available evidence regarding 29 subtopics selected as the most relevant for the subject of interest. The project was developed in several stages, during which the selected topics were distributed among experts recommended by both societies with recent publications on the subject of interest and/or significant teaching and research activity in the field of mechanical ventilation in Brazil. The experts were divided into pairs that were charged with performing a thorough review of the international literature on each topic. All the experts met at the Forum on Mechanical Ventilation, which was held at the headquarters of AMIB in São Paulo on August 3 and 4, 2013, to collaboratively draft the final text corresponding to each sub-topic, which was presented to, appraised, discussed and approved in a plenary session that included all 58 participants and aimed to create the final document.

Fluid resuscitation in sepsis: reexamining the paradigm

Sepsis results in widespread inflammatory responses altering homeostasis. Associated circulatory abnormalities (peripheral vasodilation, intravascular volume depletion, increased cellular metabolism, and myocardial depression) lead to an imbalance between oxygen delivery and demand, triggering end organ injury and failure. Fluid resuscitation is a key part of treatment, but there is little agreement on choice, amount, and end points for fluid resuscitation. Over the past few years, the safety of some fluid preparations has been questioned. Our paper highlights current concerns, reviews the science behind current practices, and aims to clarify some of the controversies surrounding fluid resuscitation in sepsis.

Prevalence of Ventilatory Conditions for Dynamic Fluid Responsiveness Prediction in 2 Tertiary Intensive Care Units

BACKGROUND

Dynamic parameters for fluid responsiveness obtained from heart-lung interaction during invasive mechanical ventilation require specific conditions not always present in intensive care unit (ICU) patients. The aim of this study was to examine the prevalence of these conditions in critically ill patients.

METHODS

We conducted a prospective observational study in 2 medical-surgical ICUs. We evaluated whether it would be possible to measure dynamic indices of fluid responsiveness when fluid expansion was administered. We recorded whether the patients were in controlled invasive mechanical ventilation with tidal volume >8 mL/kg and without arrhythmias. The proportion of patients who fulfilled these conditions was recorded. A post hoc subgroup analyses by terciles of Simplified Acute Physiology Score 3 (SAPS3) were performed.

RESULTS

A total of 826 fluid challenges were undertaken in 424 patients during the study. The use of controlled mechanical ventilation with tidal volume > 8 mL/kg and without arrhythmias occurred in only 2.9% of the patients at the time of fluid challenge episodes. There was an increase in the prevalence of these conditions as the severity of the patients also increased: lower tercile of SAPS3 (0%), intermediate tercile (2%), and higher tercile (6.9%; P < .01 Pearson chi-square test).

CONCLUSIONS

Respiratory-dependent dynamic parameters for predicting fluid responsiveness in ICU may have restricted applicability in daily practice, even in more severe patients, due to low prevalence of required conditions.

Non-invasive detection of hypovolemia or fluid responsiveness in spontaneously breathing subjects

Background

In the assessment of hypovolemia the value of functional hemodynamic monitoring during spontaneous breathing is debated. The aim of our study was to investigate in spontaneously breathing subjects the changes in hemodynamic parameters during graded central hypovolemia and to test whether slow patterned breathing improved the discriminative value of stroke volume (SV), pulse pressure (PP), and their variations (SVV, PPV). In addition, we tested the alterations in labial microcirculation.

Methods

20 healthy volunteers participated in our study. Central hypovolemia was induced by lower body negative pressure (LBNP). Continuous signals of ECG, non-invasive blood pressure and central venous pressure were recorded. During baseline and each stage of LBNP the labial microcirculation was investigated by orthogonal polarization spectral imaging, 3 minute periods of patterned breathing at 6 and 15/min respiratory rate were performed, and central venous blood gas analysis was done. Data from baseline and those of different LBNP levels were compared by analysis of variance and those of different breathing rates by t-test. Finally, we performed ROC analysis to assess the discriminative values of SV, PP, SVV and PPV.

Results

Moderate central hypovolemia induced by LBNP caused significant, clinically relevant falls in PP (p < 0.05) and SV and central venous oxygen saturation (ScvO₂) (p < 0.001). The proportion of perfused vessels (p < 0.001) and microvascular flow index decreased (p < 0.05). PPV increased (p < 0.001), however the magnitude of fluctuations was greater during slow patterned breathing (p < 0.001). SVV increased only during slow patterned breathing (p < 0.001). ROC analysis confirmed the best predictive value for SV (at 56 ml cut-off AUC 0.97, sensitivity 94%, specificity 95%). Slow patterned breathing improved the discriminative value of SVV (p = 0.0023).

Conclusions

Functional hemodynamic monitoring with slow patterned breathing to control spontaneous respiration may be worthy for further study in different populations for the assessment of hypovolemia and the prediction of volume responsiveness.

Perioperative hemodynamic monitoring

Hemodynamic monitoring is the cornerstone of perioperative anesthetic monitoring. In the unconscious patient, hemodynamic monitoring not only provides information relating to cardiac output, volume status and ultimately tissue perfusion, but also indicates depth of anesthesia and adequacy of pain control. In the 21st century the anesthesiologist has an array of devices to choose from. No single device provides a complete assessment of hemodynamic status, and the use of all devices in every situation is neither practical nor appropriate. This article aims to provide the reader with an overview of the devices currently available, and the information they provide, to assist anesthesiologists in the selection of the most appropriate devices for any given situation.

Assessment of intravascular volume status and volume responsiveness in critically ill patients

Accurate assessment of a patient's volume status, as well as whether they will respond to a fluid challenge with an increase in cardiac output, is a critical task in the care of critically ill patients. Despite this, most decisions regarding fluid therapy are made either empirically or with limited and poor data. Given recent data highlighting the negative impact of either inadequate or overaggressive fluid therapy, understanding the tools and techniques available for accurate volume assessment is critical. This review highlights both static and dynamic methods that can be utilized to help in the assessment of volume status.

Bench-to-bedside review: An approach to hemodynamic monitoring--Guyton at the bedside

Hemodynamic monitoring is used to identify deviations from hemodynamic goals and to assess responses to therapy. To accomplish these goals one must understand how the circulation is regulated. In this review I begin with an historical review of the work of Arthur Guyton and his conceptual understanding of the circulation and then present an approach by which Guyton's concepts can be applied at the bedside. Guyton argued that cardiac output and central venous pressure are determined by the interaction of two functions: cardiac function, which is determined by cardiac performance; and a return function, which is determined by the return of blood to the heart. This means that changes in cardiac output are dependent upon changes of one of these two functions or of both. I start with an approach based on the approximation that blood pressure is determined by the product of cardiac output and systemic vascular resistance and that cardiac output is determined by cardiac function and venous return. A fall in blood pressure with no change in or a rise in cardiac output indicates that a decrease in vascular resistance is the dominant factor. If the fall in blood pressure is due to a fall in cardiac output then the role of a change in the return function and cardiac function can be separated by the patterns of changes in central venous pressure and cardiac output. Measurement of cardiac output is a central component to this approach but until recently it was not easy to obtain and was estimated from surrogates. However, there are now a number of non-invasive devices that can give measures of cardiac output and permit the use of physiological principles to more rapidly appreciate the primary pathophysiology behind hemodynamic abnormalities and to provide directed therapy.

Cardiopulmonary interactions and volume status assessment

Assessment of the hemodynamics and volume status is an important daily task for physicians caring for critically ill patients. There is growing consensus in the critical care community that the "traditional" methods-e.g., central venous pressure or pulmonary artery occlusion pressure-used to assess volume status and fluid responsiveness are not well supported by evidence and can be misleading. Our purpose is to provide here an overview of the knowledge needed by ICU physicians to take advantage of mechanical cardiopulmonary interactions to assess volume responsiveness. Although not perfect, such dynamic assessment of fluid responsiveness can be helpful particularly in the passively ventilated patients. We discuss the impact of phasic changes in lung volume and intrathoracic pressure on the pulmonary and systemic circulation and on the heart function. We review how respirophasic changes on the venous side (great veins geometry) and arterial side (e.g., stroke volume/systolic blood pressure and surrogate signals) can be used to detect fluid responsiveness or hemodynamic alterations commonly encountered in the ICU. We review the physiological limitations of this approach.

Optimization of preload in severe sepsis and septic shock

In sepsis both under- and overresuscitation are associated with increased morbidity and mortality. Moreover, sepsis can be complicated by myocardial dysfunction, and only half of the critically ill patients exhibit preload responsiveness. It is of paramount importance to accurately, safely, and rapidly determine and optimize preload during resuscitation. Traditional methods of determining preload based on measurement of pressure in a heart chamber or volume of a heart chamber ("static" parameters) are inaccurate and should be abandoned in favor of determining preload responsiveness by using one of the "dynamic parameters" based on respiratory variation in the venous or arterial circulation or based on change in stroke volume in response to an endogenous or exogenous volume challenge. The recent development and validation of a number of noninvasive technologies now allow us to optimize preload in an accurate, safe, rapid and, cost-effective manner.

Appreciating the strengths and weaknesses of transthoracic echocardiography in hemodynamic assessments

Transthoracic echocardiography (TTE) is becoming the choice of hemodynamic assessment tool in many intensive care units. With an ever increasing number of training programs available worldwide, learning the skills to perform TTE is no longer a limiting factor. Instead, the future emphasis will be shifted to teach the users how to recognize measurement errors and artefacts (internal validity), to realize the limitations of TTE in various applications, and finally how to apply the information to the patient in question (external validity). This paper aims to achieve these objectives in a common area of TTE application-hemodynamic assessments. We explore the strengths and weaknesses of TTE in such assessments in this paper. Various methods of hemodynamic assessments, such as cardiac output measurements, estimation of preload, and assessment of fluid responsiveness, will be discussed.

Perioperative intravascular fluid assessment and monitoring: a narrative review of established and emerging techniques

Accurate assessments of intravascular fluid status are an essential part of perioperative care and necessary in the management of the hemodynamically unstable patient. Goal-directed fluid management can facilitate resuscitation of the hypovolemic patient, reduce the risk of fluid overload, reduce the risk of the injudicious use of vasopressors and inotropes, and improve clinical outcomes. In this paper, we discuss the strengths and limitations of a spectrum of noninvasive and invasive techniques for assessing and monitoring intravascular volume status and fluid responsiveness in the perioperative and critically ill patient.

[Assessment of cardiovascular preload and response to volume expansion]

Volume expansion is used in patients with hemodynamic insufficiency in an attempt to improve cardiac output. Finding criteria to predict fluid responsiveness would be helpful to guide resuscitation and to avoid excessive volume effects. Static and dynamic indicators have been described to predict fluid responsiveness under certain conditions. In this review we define preload and preload-responsiveness concepts. A description is made of the characteristics of each indicator in patients subjected to mechanical ventilation or with spontaneous breathing.

Hemodynamic and perfusion end points for volemic resuscitation in sepsis

Sepsis is the systemic inflammatory response syndrome secondary to a local infection, and severe sepsis and septic shock are the more devastating scenarios of this disease. In the last decade, considerable achievements were obtained in sepsis knowledge, and an international campaign was developed to improve the treatment of this condition. However, sepsis is still one of the most important causes of death in intensive care units. The early stages of sepsis are characterized by a variety of hemodynamic derangements that induce a systemic imbalance between tissue oxygen supply and demand, leading to global tissue hypoxia. This dysfunction, which may occur in patients presenting normal vital signs, can be accompanied by a significant increase in both morbidity and mortality. The early identification of high-risk sepsis patients through tissue perfusion markers such as lactate and venous oxygen saturation is crucial for prompt initiation of therapeutic support, which includes early goal-directed therapy as necessary. The purpose of this article was to review the most commonly used hemodynamic and perfusion parameters for hemodynamic optimization in sepsis, emphasizing the physiological background for their use and the studies that demonstrated their effectiveness as goals of volemic resuscitation.

Hemodynamic resuscitation in septic shock: cardiovascular support and adjunctive therapy

Sepsis is associated with hemodynamic derangements that lead to tissue hypoperfusion and multisystem organ failure if uncorrected. Considerable data published in recent years have addressed detection and treatment of sepsis. However, much is unknown about the selection and titration of appropriate therapy, appropriate goals and end points for resuscitation, and the hemodynamic monitoring necessary based on these goals and end points. Current therapeutic interventions include preload optimization, initiation of timely and appropriate vasopressor and inotropic support, decisions about corticosteroid therapy and recombinant human activated protein C, and early and adequate antibiotic therapy. This article focuses on the cardiovascular support of the septic shock patient, and the current evidence to guide decisions on the use of corticosteroid therapy and recombinant human activated protein C.

Interactions between respiration and systemic hemodynamics. Part II: practical implications in critical care

In Part I of this review, we have covered basic concepts regarding cardiorespiratory interactions. Here, we put this theoretical framework to practical use. We describe mechanisms underlying Kussmaul's sign and pulsus paradoxus. We review the literature on the use of respiratory variations of blood pressure to evaluate volume status. We show the possibilities of attaining the latter aim by investigating with ultrasonography how the geometry of great veins fluctuates with respiration. We provide a Guytonian analysis of the effects of PEEP on cardiac output. We terminate with some remarks on the potential of positive pressure breathing to induce acute cor pulmonale, and on the cardiovascular mechanisms that at times may underly the failure to wean a patient from the ventilator.

Functional hemodynamic monitoring

PURPOSE OF REVIEW

To assess the recent literature on effective use of information received from hemodynamic monitoring.

RECENT FINDINGS

Dynamic hemodynamic measures are more effective in assessing cardiovascular status than static measures. In this review, we will focus on the application of hemodynamic monitoring to evaluate the effect of therapy.

SUMMARY

A systematic approach to an effective resuscitation effort can be incorporated into a protocolized cardiovascular management algorithm, which, in turn, can improve patient-centered outcomes and the cost of healthcare systems, by faster and more effective response in order to diagnose and treat hemodynamically unstable patients both inside and outside of intensive care units.