Predict Volume Responsiveness Research Articles

Changes in End-Tidal Carbon Dioxide and Volumetric Carbon Dioxide as Predictors of Volume Responsiveness in Hemodynamically Unstable Patients

The purpose of this study was to determine whether changes in PETCO2 and exhaled CO2 (VCO2) can predict fluid responsiveness after a preload challenge. A retrospective review of prospectively recorded data. A medical intensive care unit of a university-affiliated tertiary care hospital. Mechanically ventilated patients undergoing a preload challenge. In the authors' intensive care unit, fluid responsiveness is determined by a passive leg raising (PLR) maneuver and/or a 500-mL crystalloid challenge. An increase in the stroke volume index >10% as measured by a NICOM bioreactance cardiac output monitor (Cheetah Medical, Inc, Vancouver, WA) is used to determine fluid responsiveness. PETCO2 and volumetric capnography (VCO2) were monitored via a combined CO2 and flow sensor capnostat (Respironics NM3 Monitor; Philips Healthcare, Eindhoven, Netherlands). Patients were mechanically ventilated with tidal volumes controlled at 8 mL/kg, allowing for consistent minute ventilation. During the study period, 44 challenges (10 PLR and 34 fluid boluses) were performed on 34 patients. There were 24 (54%) positive "fluid" responses. PETCO2 increased by 5.9% ± 7.6% in the responders compared with 1.4% ± 4.4% in the nonresponders (p = 0.02). Similarly, VCO2 increased by 11.0% ± 8.6% in the responders compared with 0.8% ± 5.6% in the nonresponders (p = 0.001). The area under the receiver operating characteristic curve was 0.67 (95% confidence interval, 0.48-0.80) for PETCO2 and 0.79 (95% confidence interval, 0.63-0.89) for VCO2. PETCO2 and VCO2 were predictive of fluid responsiveness only in those patients without underlying lung disease. The stroke volume variation was 15.8 ± 3.7 in the responders compared with 13.6 ± 4.8 in the nonresponders (p = 0.15). Dynamic changes in PETCO2 and VCO2 may be used as adjunctive indicators of fluid responsiveness in patients without underlying lung disease.

Prediction of fluid responsiveness in patients admitted to the medical intensive care unit

PurposeAccurate prediction of fluid responsiveness is of importance in the treatment of patients admitted to the intensive care unit (ICU). We investigated whether physical examination, central venous pressure (CVP), central venous oxygen saturation (ScvO2), passive leg raising (PLR) test, and transpulmonary thermodilution (TPTD)–derived parameters can predict volume responsiveness in patients admitted to the ICU. Materials and MethodsIn this prospective study, structured clinical examination, measurement of CVP and ScvO2, a PLR test, and TPTD measurements were performed in 31 patients. A fluid challenge test was performed in 24 patients (fluid responsiveness was defined as a cardiac index [CI] increase of ≥15%). ResultsPhysical examination, CVP, ScvO2, the PLR test, and the TPTD-derived volumetric preload parameter global end-diastolic volume index showed poor prognostic capabilities regarding prediction of fluid responsiveness. Twenty-nine percent of patients were fluid responsive. There was a statistically significant correlation between the fluid challenge–induced increase in CI and changes in global end-diastolic volume index (r = 0.666, P < .001). In only 17% of patients, CI did not increase after fluid loading. ConclusionsPrediction of fluid responsiveness is difficult using physical examination, CVP, ScvO2, PLR maneuver, or TPTD-derived variables in critically ill patients. A volume challenge test should be considered for the assessment of fluid responsiveness in critically ill patients admitted to the ICU.

Intraoperative Use of Transoesophageal Doppler to Predict Response to Volume Expansion in Infants and Neonates

Background Volume expansion (VE) in neonates or infants during volatile anaesthesia may lead to fluid overload if inappropriate. Transoesophageal Doppler (TED), a non-invasive cardiac output monitoring technique, can provide a comprehensive estimation of the volaemic status. We evaluated whether intraoperative TED-derived parameters can predict volume responsiveness. Methods Neonates and infants under general anaesthesia without myocardial dysfunction were prospectively included when the attending anaesthetist, blinded to TED measurements, decided to provide VE based on clinical appreciation and standard monitoring data. Standard and TED-derived data were recorded before and after VE. After VE, patients were classified as responders and non-responders, if their indexed stroke volume (iSV) increased by more than 15% or not, respectively. The attending anaesthetist assessment of VE responsiveness was recorded at the end of VE. Results Fifty patients aged 42 (4) post-conceptional weeks were included, among which 26 (52%) were responders. Baseline iSV was the only parameter associated with VE responsiveness. Baseline iSV was fairly correlated with VE-induced changes in iSV (ρ=−0.64) and was associated with an area under the receiver operating characteristic curve of 0.90 (0.80, 0.99). Using a cut-off of 25 ml m−2, baseline iSV predicted volume responsiveness with a sensitivity of 92% and a specificity of 83%. Attending anaesthetists’ assessment of VE effectiveness agreed only moderately with TED measurements of iSV changes. Conclusions TED-derived iSV measurement during volatile anaesthesia is useful to predict and follow VE responsiveness in neonates and infants without myocardial dysfunction.

End-tidal carbon dioxide is better than arterial pressure for predicting volume responsiveness by the passive leg raising test

In stable ventilatory and metabolic conditions, changes in end-tidal carbon dioxide (EtCO(2)) might reflect changes in cardiac index (CI). We tested whether EtCO(2) detects changes in CI induced by volume expansion and whether changes in EtCO(2) during passive leg raising (PLR) predict fluid responsiveness. We compared EtCO(2) and arterial pulse pressure for this purpose. We included 65 patients [Simplified Acute Physiology Score (SAPS) II = 57 ± 19, 37 males, under mechanical ventilation without spontaneous breathing, 15 % with chronic obstructive pulmonary disease, baseline CI = 2.9 ± 1.1 L/min/m(2)] in whom a fluid challenge was decided due to circulatory failure and who were monitored by an expiratory-CO(2) sensor and a PiCCO2 device. In all patients, we measured arterial pressure, EtCO(2), and CI before and after a fluid challenge. In 40 patients, PLR was performed before fluid administration. The PLR-induced changes in arterial pressure, EtCO(2), and CI were recorded. Considering the whole population, the fluid-induced changes in EtCO(2) and CI were correlated (r (2) = 0.45, p = 0.0001). Considering the 40 patients in whom PLR was performed, volume expansion increased CI ≥ 15 % in 21 "volume responders." A PLR-induced increase in EtCO(2) ≥ 5 % predicted a fluid-induced increase in CI ≥ 15 % with sensitivity of 71 % (95 % confidence interval: 48-89 %) and specificity of 100 (82-100) %. The prediction ability of the PLR-induced changes in CI was not different. The area under the receiver-operating characteristic (ROC) curve for the PLR-induced changes in pulse pressure was not significantly different from 0.5. The changes in EtCO(2) induced by a PLR test predicted fluid responsiveness with reliability, while the changes in arterial pulse pressure did not.

Stroke Volume Variation as a Guide for Fluid Resuscitation in Patients Undergoing Large-Volume Liposuction

: The potential for fluid overload in large-volume liposuction is a source of serious concern. Fluid management in these patients is controversial and governed by various formulas that have been advanced by many authors. Basically, it is the ratio of what goes into the patient and what comes out. Central venous pressure has been used to monitor fluid therapy. Dynamic parameters, such as stroke volume and pulse pressure variation, are better predictors of volume responsiveness and are superior to static indicators, such as central venous pressure and pulmonary capillary wedge pressure. Stroke volume variation was used in this study to guide fluid resuscitation and compared with one guided by an intraoperative fluid ratio of 1.2 (i.e., Rohrich formula). : Stroke volume variation was used as a guide for intraoperative fluid administration in 15 patients subjected to large-volume liposuction. In another 15 patients, fluid resuscitation was guided by an intraoperative fluid ratio of 1.2. The amounts of intravenous fluid administered in the groups were compared. : The mean amount of fluid infused was 561 ± 181 ml in the stroke volume variation group and 2383 ± 1208 ml in the intraoperative fluid ratio group. The intraoperative fluid ratio when calculated for the stroke volume variation group was 0.936 ± 0.084. All patients maintained hemodynamic parameters (heart rate and systolic, diastolic, and mean blood pressure). Renal and metabolic indices remained within normal limits. : Stroke volume variation-guided fluid application could result in an appropriate amount of intravenous fluid use in patients undergoing large-volume liposuction. : Therapeutic, II.

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

ObjectiveThe purpose of this study was to assess the usefulness of stroke volume variations to monitor the early fluid resuscitation in mechanically ventilated burn ICU patients. Methods and resultsData of 29 burn patients (APACHE II – 9.8±3.6, SAPS II – 29±5, TBSA – 39.5±14) were prospectively included in this observational study. Hemodynamic parameters were determined using arterial pressure wave analysis for up to 36h after burn. Statistically significant changes in cardiac index (CI), systemic vascular resistance index (SVRI), stroke volume variation (SVV) were recorded during the observation period. There were significant correlations between CI and SVV (r=−0.454, p=0.03), SVV and SVRI (r=0.482, p=0.02) at 16h postburn; CI and SVV (r=−0.513, p=0.012), SVV and SVRI (r=0.480, p=0.02) at 24h postburn, CI and SVV at 36h postburn (r=−0.478, p=0.021). Significant changes in CI (1.9±1 vs. 3.4±0.9), p=0.02 and in SVV (24.9±3 vs. 14.6±2, p=0.01) were observed in patients with low cardiac output state after administration of 10ml/kg of Ringer lactate. ConclusionOur results suggest that measurement of stroke volume variations by arterial pulse contour analysis is valuable in monitoring volume administration and in predicting volume responsiveness during the early postburn period.

Heart lung interactions during mechanical ventilation

To survey the recent medical literature examining studies of the hemodynamic effects of mechanical ventilation. Ventilation-induced dynamic changes in arterial pulse pressure and stroke volume variation (PPV and SVV, respectively) identify volume responsiveness. The cause of PPV and SVV are due to intrathoracic pressure-induced variations in right atrial pressure changing intrathoracic blood volume over the ventilatory cycle. This explains why PPV and SVV are inaccurate with smaller tidal volumes used in acute lung injury, but remain useful in one-lung ventilation and prone positioning. Noninvasive measures of PPV and SVV using finger plethysmography and aortic root ultrasound or estimates of intrathoracic blood volume by thoracic impedance also predict volume responsiveness. Finally, the PPV-to-SVV ratio varies with vasomotor tone and can be used to identify vasopressor need in hypotensive patients. The clinical implications of these findings are starting to be realized in recommended management principles. PPV and SVV predict volume responsiveness, but like all monitoring approaches, need to be understood within the framework of their physiologic determinations.

Clinical study of passive leg raising as an indicator of fluid responsiveness in severe septic patients

Objective To assess the value of legs passively lifted as an indicator of fluid responsiveness in mechanically ventilated patients with severe sepsis.Methods Twenty-eight mechanically ventilated patients with severe sepsis admitted from May 2010 to May 2011 for volume resuscitation were collected.Patients with non-sinus rhythm or arrhythmia and parturients were excluded. Variation of hemodynamics of the patients in a semi-recumbent position,after passive leg raising (PLR) and after volume expansion (500 ml 6％ hydroxyethyl starch infusion within 30 mins) was studied by using the technique of pulse indicator continuous cardiac output (PiCCO) system.The volume resuscitation were resulted into two groups,responder and non-responder,as per △SVI (stroke volume index) over 15％.HR,arterial systoicblood pressure (ABPs),arterial diastolic blood pressure (ABPd),mean arterial blood pressure (ABPm),mean central venous pressure (CVPm) and cardiac index (CI) were compared between two groups.The changes of ABPs,ABPm,CVPm and SVI after PLR and after fluid resuscitation werc compared with those before PLR and fluid resuscitation.The ROC curve was drawn to evaluate the value of △SVI and △CVPm in predicting volume responsiveness. SPSS 17.0 software was used for statistic analysis. Results Of 28 patients,8 were responders and 10 were non-responders.In responders after PLR,some hemodynamic variables including ABPs,ABPm and CVPm were significantly increased [(100.1 ± 18.1) vs.(115.9 ±13.1),P=0.005; (68.1±12.4) vs.(77.8±13.0),P=0.03and(7.2±3.4) vs.(10.1±4.1),P=0.03,respectively ].After PLR,the area under curve (AUC) of the ROC curve of △SVI and △CVPm to predict the responsiveness after fluid resuscitation were 0.897 ± 0.059 (95 ％ CI 0.762-1.000) and 0.819±0.081 (95％CI 0.661-0.977),respectively.When the cut-off levels of △SVI and △CVPm were 10.5％ and 12.7％,the sensitivities were 72.2％ and 72.2％,the specificities were 90％ and 80％.Conclusions Changes in △SVI and △CVPm induced by passive leg raising are accurate indices for predicting fluid responsiveness in mechanically ventilated patients with severe sepsis. Key words: Passive leg raising; Fluid resuscitation; Hemodynamic monitoring; Stroke volumeindex; Central venous pressure; Severe sepsis; Fluid responsiveness; ROC curve

Dynamic indices do not predict volume responsiveness in routine clinical practice

Dynamic indices, including pulse pressure, systolic pressure, and stroke volume variation (PPV, SPV, and SVV), are accurate predictors of fluid responsiveness under strict conditions, for example, controlled mechanical ventilation using conventional tidal volumes (TVs) in the absence of cardiac arrhythmias. However, in routine clinical practice, these prerequisites are not always met. We evaluated the effect of regularly used ventilator settings, different calculation methods, and the presence of cardiac arrhythmias on the ability of dynamic indices to predict fluid responsiveness in sedated, mechanically ventilated patients. We prospectively evaluated 47 fluid challenges in 29 consecutive cardiac surgery patients. Patients were divided into different groups based on TV. Dynamic indices were calculated in various ways: calculation over 30 s, breath-by-breath (with and without excluding arrhythmias), and with correction for TV. The predictive value was optimal in the group ventilated with TVs >7 ml kg(-1) with correction for TV, calculated breath-by-breath, and with exclusion of arrhythmias [area under the curve (AUC)=0.95, 0.93, and 0.90 for PPV, SPV, and SVV, respectively]. Including patients ventilated with lower TVs decreased the predictive value of all dynamic indices, while calculating dynamic indices over 30 s and not excluding cardiac arrhythmias further reduced the AUC to 0.51, 0.63, and 0.51 for PPV, SPV, and SVV, respectively. PPV, SPV, and SVV are the only reliable predictors of fluid responsiveness under strict conditions. In routine clinical practice, factors including low TV, cardiac arrhythmias, and the calculation method can substantially reduce their predictive value.

Why the Gray Zone May Shift within the Fog

To the Editor: We read the article by Cannesson1et al. and the accompanying editorial2with great interest, and praise the effort to better define the clinical utility and applicability of pulse pressure variation (PPV), not only as a tool to predict volume responsiveness but also to move away from a single-threshold value for conducting intraoperative volume optimization and perioperative goal-directed fluid therapy. We would like to make three points.First, the most commonly used index to assess volume responsiveness, by far in the United States, appears to be stroke volume variation (SVV). Although the area under the receiver-operating curve, in systematic reviews,3shows that both PPV and SVV have excellent sensitivity and specificity in patients who are mechanically ventilated with normal tidal volumes and in a regular sinus rhythm, the threshold values discriminating between fluid responders and nonresponders are not the same for these two parameters.3,4Thus, although strategies using the “gray zone approach” applied to PPV identify a range of values where volume responsiveness cannot reliably be predicted, this range may not be applicable when SVV is used for determining volume responsiveness. Although it is clear from the work of Joseph Erlanger, the father of the pulse pressure concept,5that pulse pressure in man is proportional to left ventricular stroke volume (depending both on arterial tone and cardiac contractility) it is plausible that variations in pulse pressure may also be proportional to variations in stroke volume. To the extent that PPV and SVV are affected differently by changes in arterial tone, given the same degree of volume responsiveness,4these values may lose their direct proportionality as vascular tone changes. Pinsky described the potential utility of a SVV-to-PPV ratio to reflect ventricular-arterial coupling that might be helpful when extrapolating PPV threshold data to SVV.6Overall, applying PPV's “gray zone” to SVV seems clinically appealing but may be misleading. The “gray zone” defined for PPV should not simply be applied to patients who are being optimized using stroke volume variation. The “gray zone” for SVV requires its own definition.Second, the paper does not address the issue of volume responsiveness versus needing to give volume or using a dynamic index to actively restrict fluids or to administer diuretics to patients under certain clinical circumstances. That is, not all patients who are volume responsive require volume therapy. Conversely, there may be untapped utility for SVV- and/or PPV-guided fluid restriction and diuretic use (consider patients with acute lung injury or acute respiratory distress syndrome).7The goal would be to identify patients with a PPV that is “too low” who, consequently, should receive restrictive fluid therapy or diuretics.Third, what is, perhaps, not considered by the author2is the fact that PPV goals may vary within individual patients across changing clinical settings in relatively short intervals of time, such as during single lung ventilation for thoracic surgery, laparoscopic pneumoperitoneum, and conditions of pathologic intraabdominal hypertension. For example, the goals for intraoperative PPV during esophagectomy vary during the case, such that the goal during the abdominal part of the procedure is fluid liberal and during the thoracic part of the procedure is fluid restrictive.8In summary, we praise Cannesson et al. 1for their work and we agree that there is a “gray zone” well represented by the picture in the editorial2(i.e. , the Golden Gate Bridge with fog going across the middle represents “a static view of dynamic indices”). We contend that PPV and SVV “gray zones” are probably better described as the view one gets of the Golden Gate Bridge, with fog going across the middle as one is driving along winding hilly roads. This is a “dynamic view of dynamic indices,” such that the gray zone changes at different times depending on one's changing vantage point, an analogy closer to clinical reality.

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

In the management of critically ill patients, the assessment of volume responsiveness and the decision to administer a fluid bolus constitute a common dilemma for physicians. Static indices of cardiac preload are poor predictors of volume responsiveness. Passive leg raising (PLR) mimics an endogenous volume expansion (VE) that can be used to predict fluid responsiveness. This study was to assess the changes in stroke volume index (SVI) induced by PLR as an indicator of fluid responsiveness in mechanically ventilated patients with severe sepsis. This was a prospective study. Thirty-two mechanically ventilated patients with severe sepsis were admitted for VE in ICU of the First Affiliated Hospital, Zhejiang University School of Medicine and Ningbo Medical Treatment Center Lihuili Hospital from May 2010 to December 2011. Patients with non-sinus rhythm or arrhythmia, parturients, and amputation of the lower limbs were excluded. Measurements of SVI were obtained in a semi-recumbent position (baseline) and during PLR by the technique of pulse indicator continuous cardiac output (PiCCO) system prior to VE. Measurements were repeated after VE (500 mL 6% hydroxyethyl starch infusion within 30 minutes) to classify patients as either volume responders or non-responders based on their changes in stroke volume index (ΔSVI) over 15%. Heart rate (HR), systolic artery blood pressure (ABPs), diastolic artery blood pressure (ABPd), mean arterial blood pressure (ABPm), mean central venous pressure (CVPm) and cardiac index (CI) were compared between the two groups. The changes of ABPs, ABPm, CVPm, and SVI after PLR and VE were compared with the indices at the baseline. The ROC curve was drawn to evaluate the value of ΔSVI and the change of CVPm (ΔCVPm) in predicting volume responsiveness. SPSS 17.0 software was used for statistical analysis. Among the 32 patients, 22 were responders and 10 were non-responders. After PLR among the responders, some hemodynamic variables (including ABPs, ABPd, ABPm and CVPm) were significantly elevated (101.2±17.6 vs.118.6±23.7, P=0.03; 52.8±10.7 vs. 64.8±10.7, P=0.006; 68.3±11.7 vs. 81.9±14.4, P=0.008; 6.8±3.2 vs. 11.9±4.0, P=0.001). After PLR, the area under curve (AUC) and the ROC curve of ΔSVI and ΔCVPm for predicting the responsiveness after VE were 0.882±0.061 (95%CI 0.759-1.000) and 0.805±0.079 (95%CI 0.650-0.959) when the cut-off levels of ΔSVI and ΔCVPm were 8.8% and 12.7%, the sensitivities were 72.7% and 72.7%, and the specificities were 80% and 80%. Changes in ΔSVI and ΔCVPm induced by PLR are accurate indices for predicting fluid responsiveness in mechanically ventilated patients with severe sepsis.

Intraoperative use of transoesophageal Doppler to predict response to volume expansion in infants and neonates

Volume expansion (VE) in neonates or infants during volatile anaesthesia may lead to fluid overload if inappropriate. Transoesophageal Doppler (TED), a non-invasive cardiac output monitoring technique, can provide a comprehensive estimation of the volaemic status. We evaluated whether intraoperative TED-derived parameters can predict volume responsiveness. Neonates and infants under general anaesthesia without myocardial dysfunction were prospectively included when the attending anaesthetist, blinded to TED measurements, decided to provide VE based on clinical appreciation and standard monitoring data. Standard and TED-derived data were recorded before and after VE. After VE, patients were classified as responders and non-responders, if their indexed stroke volume (iSV) increased by more than 15% or not, respectively. The attending anaesthetist assessment of VE responsiveness was recorded at the end of VE. Fifty patients aged 42 (4) post-conceptional weeks were included, among which 26 (52%) were responders. Baseline iSV was the only parameter associated with VE responsiveness. Baseline iSV was fairly correlated with VE-induced changes in iSV (ρ=-0.64) and was associated with an area under the receiver operating characteristic curve of 0.90 (0.80, 0.99). Using a cut-off of 25 ml m(-2), baseline iSV predicted volume responsiveness with a sensitivity of 92% and a specificity of 83%. Attending anaesthetists' assessment of VE effectiveness agreed only moderately with TED measurements of iSV changes. TED-derived iSV measurement during volatile anaesthesia is useful to predict and follow VE responsiveness in neonates and infants without myocardial dysfunction.

Goal-Directed Fluid Therapy Using Stroke Volume Variation Does Not Result in Pulmonary Fluid Overload in Thoracic Surgery Requiring One-Lung Ventilation

Background. Goal-directed fluid therapy (GDT) guided by functional parameters of preload, such as stroke volume variation (SVV), seems to optimize hemodynamics and possibly improves clinical outcome. However, this strategy is believed to be rather fluid aggressive, and, furthermore, during surgery requiring thoracotomy, the ability of SVV to predict volume responsiveness has raised some controversy. So far it is not known whether GDT is associated with pulmonary fluid overload and a deleterious reduction in pulmonary function in thoracic surgery requiring one-lung-ventilation (OLV). Therefore, we assessed the perioperative course of extravascular lung water index (EVLWI) and paO2/FiO2-ratio during and after thoracic surgery requiring lateral thoracotomy and OLV to evaluate the hypothesis that fluid therapy guided by SVV results in pulmonary fluid overload. Methods. A total of 27 patients (group T) were enrolled in this prospective study with 11 patients undergoing lung surgery (group L) and 16 patients undergoing esophagectomy (group E). Goal-directed fluid management was guided by SVV (SVV < 10%). Measurements were performed directly after induction of anesthesia (baseline—BL), 15 minutes after implementation OLV (OLVimpl15), and 15 minutes after termination of OLV (OLVterm15). In addition, postoperative measurements were performed at 6 (6postop), 12 (12postop), and 24 (24postop) hours after surgery. EVLWI was measured at all predefined steps. The paO2/FiO2-ratio was determined at each point during mechanical ventilation (group L: BL-OLVterm15; group E: BL-24postop). Results. In all patients (group T), there was no significant change (P > 0.05) in EVLWI during the observation period (BL: 7.8 ± 2.5, 24postop: 8.1 ± 2.4 mL/kg). A subgroup analysis for group L and group E also did not reveal significant changes of EVLWI. The paO2/FiO2-ratio decreased significantly during the observation period (group L: BL: 462 ± 140, OLVterm15: 338 ± 112 mmHg; group E: BL: 389 ± 101, 24postop: 303 ± 74 mmHg) but remained >300 mmHg except during OLV. Conclusions. SVV-guided fluid management in thoracic surgery requiring lateral thoracotomy and one-lung ventilation does not result in pulmonary fluid overload. Although oxygenation was reduced, pulmonary function remained within a clinically acceptable range.

Do hemodynamic measures accurately predict volume responsiveness when lung compliance is severely reduced by acute lung injury/acute respiratory distress syndrome?*

Department of Anesthesiology University of Kentucky College of Medicine Lexington, KY * See also p. 152. The author has not disclosed any potential conflicts of interest.

What’s New in Shock, December 2011?

What’s New in Shock, December 2011?

Assessment of Intravascular Fluid Status and Fluid Responsiveness during Mechanical Ventilation in Surgical and Intensive Care Patients

Fluid management of critically ill patients and those undergoing major surgery can be extremely difficult. It is important to predict which patients will respond to volume expansion in order to avoid undesired hypovolaemia and fluid overload. Traditionally, central venous pressure and pulmonary artery occlusion pressure have been used to guide fluid management. However, assimilation of available evidence from the past twenty years demonstrates that neither central venous pressure nor pulmonary artery occlusion pressure appears to be a useful predictor of haemodynamic response to fluid challenge. Recent evidence suggests that stroke volume variation, pulse pressure variation and the variation of the amplitude of the pulse oximeter plethysmographic waveform are far more accurate in predicting volume responsiveness in the intensive care unit. It is important for intensivists and perioperative physicians to understand the strengths and limitations of each method in order to scrutinise and interpret such data appropriately.

Use of Dynamic Variables of Volume Responsiveness and Cardiac Output in Diagnosis of Pulmonary Embolism

INTRODUCTION: Dynamic changes of arterial waveform-derived variables (stroke volume variation (SVV), during positive pressure ventilation (PPV) have been shown to predict volume responsiveness in critically ill patients [1]; however, their use in diagnosing right ventricular (RV) failure is underappreciated.

Detection of Right Ventricular Insufficiency and Guidance of Volume Therapy Are Facilitated by Simultaneous Monitoring of Static and Functional Preload Parameters

Acute right ventricular failure (RVF) is a life-threatening condition. This study investigated whether the combination of central venous pressure (CVP) and left ventricular functional preload parameters, such as stroke volume variation (SVV) and pulse pressure variation (PPV), can be used for the detection of acute RVF and for guidance of volume therapy. Experimental study in a university laboratory. Fifteen anesthetized and ventilated pigs. For the induction of RVF, mean pulmonary artery pressure (MPAP) was increased by 50% with a continuous infusion of a thromboxane-A(2) analog (U46619). Then, blood removal (300 mL) and retransfusion (blood 200 mL + colloid solution 200 mL) were performed. An analysis of volume responders and nonresponders was implemented. Increasing MPAP (25.1 to 37.4 mmHg) led to decreases in mean arterial pressure (72.2 to 60.1 mmHg) and cardiac output (2.8 to 2.3 L/min, p < 0.05). CVP (11.3 to 12.6 mmHg), PPV (13% to 17%), and SVV (11 to 14%) increased significantly (p < 0.05). During volume removal, MPAP (37.4 to 34.1 mmHg), mean arterial pressure (60.1 to 53.2 mmHg), and cardiac output (2.3 to 2.1 L/min) decreased (p < 0.05), whereas PPV and SVV remained unchanged. During volume loading, CVP increased in volume responders and nonresponders; however, PPV decreased in responders only. Increases of CVP and SVV or PPV are suspicious for RVF. However, SVV and PPV fail to predict volume responsiveness in RVF. Changes in SVV and PPV during a volume-loading maneuver can be used to assess volume responsiveness.

Echocardiographic Assessment of Preload Responsiveness in Critically Ill Patients

Fluid challenges are considered the cornerstone of resuscitation in critically ill patients. However, clinical studies have demonstrated that only about 50% of hemodynamically unstable patients are volume responsive. Furthermore, increasing evidence suggests that excess fluid resuscitation is associated with increased mortality. It therefore becomes vital to assess a patient's fluid responsiveness prior to embarking on fluid loading. Static pressure (CVP, PAOP) and echocardiographic (IVC diameter, LVEDA) parameters fails to predict volume responsiveness. However, a number of dynamic echocardiographic parameters which are based on changes in vena-caval dimensions or cardiac function induce by positive pressure ventilation or passive leg raising appear to be highly predictive of volume responsiveness.

Visual evaluation of left ventricular performance predicts volume responsiveness early after resuscitation from cardiac arrest

Purpose Haemodynamic optimisation is a fundamental goal of post-cardiac arrest therapy. Therefore, predicting volume responsiveness is a key issue in therapy of these high-risk patients and transoesophageal echocardiography (TEE) may provide helpful information. The aim of the present study was to evaluate the performance of visual evaluation (eyeballing) of standardised TEE-loops to predict volume responsiveness during post-cardiac arrest period. Methods After approval of the local animal investigation committee, TEE mid-oesophageal long-axis views were recorded before a 5 ml/kg volume bolus at baseline and both 1 and 4 h after return of spontaneous circulation (ROSC) from 8 min electrically induced cardiac arrest. Post-hoc, TEE loops were independently presented in randomized order to 7 blinded TEE-experts and 14 blinded TEE novices who were asked to predict whether the ventricle will increase stroke volume ≥15% after volume loading or not. Statistics were performed calculating sensitivity and specificity for the correct evaluation and agreement of raters. Results 14 out of 20 pigs were successfully resuscitated, and 924 ratings from 21 echocardiographers were included into analysis. Overall, we observed a sensitivity between 71 and 100%, whereas the specificity showed rather low values between 0 and 67% for prediction of volume responsiveness. Best prediction was recorded 1 h after ROSC with median sensitivity (95% CI) of 100% (89–100%) and median specificity of 67% (61–72%). No significant difference was found between ratings of experienced and inexperienced echocardiographers. The concordance rate within the two groups was comparable. Conclusions In post-cardiac arrest period, visual evaluation of long-axis TEE loops allows prediction of volume responsiveness with good sensitivity and reasonable specificity even by novice users, and may therefore be suitable for implementation into treatment protocols.