Hemodynamic-volumetric monitoring

Maintenance of adequate cardiac preload is of paramount importance in the treatment of patients undergoing major surgical surgery and in the critically ill setting. The end point is to maintain the organ perfusion through volume replacement and therapy to optimize cardiac output, oxygen deliver. Various methods have been introduced into clinical practice to estimate cardiac preload. In the last 10 years the transpulmonary indicator dilution technique showed to be accurate as hemodynamic-volumetric monitoring. We briefly review the intra thoracic blood volume index as a preload index and the fluid responsiveness indexes, stroke volume variation and pulse pressure variation, available as novel parameters at the bed-side.The optimization of fluid balance and vasoactive drugs administration based on volumetric monitoring makes the transpulmonary indicator dilution technique a new option as an effective monitoring system where intravascular volume management is a primary objective.     

Assessment of fluid responsiveness in mechanically ventilated cardiac surgical patients

BACKGROUND AND OBJECTIVE: Accurate assessment of preload responsiveness is an important goal of the clinician to avoid deleterious volume replacement associated with increased morbidity and mortality in mechanically ventilated patients. This study was designed to evaluate the accuracy of simultaneously assessed stroke volume variation and pulse pressure variation using an improved algorithm for pulse contour analysis (PiCCO plus, V 5.2.2), compared to the respiratory changes in transoesophageal echo-derived aortic blood velocity (deltaVpeak), intrathoracic blood volume index, central venous pressure and pulmonary capillary wedge pressure to predict the response of stroke volume index to volume replacement in normoventilated cardiac surgical patients. METHODS: We studied 20 patients undergoing elective coronary artery bypass grafting. After induction of anaesthesia, haemodynamic measurements were performed before and after volume replacement by infusion of 6% hydroxyethyl starch 200/0.5 (7 mL kg(-1) ) with a rate of 1 mL kg(-1) min(-1). RESULTS: Baseline stroke volume variation correlated significantly with changes in stroke volume index (deltaSVI) (r2 = 0.66; P < 0.05) as did baseline pulse pressure variation (r2 = 0.65; P < 0.05), whereas baseline values of deltaVpeak, intrathoracic blood volume index, central venous pressure and pulmonary artery wedge pressure showed no correlation to deltaSVI. Pulse contour analysis underestimated the volume-induced increase in cardiac index measured by transpulmonary thermodilution (P < 0.05). CONCLUSIONS: The results of our study suggest that stroke volume variation and its surrogate pulse pressure variation derived from pulse contour analysis using an improved algorithm can serve as indicators of fluid responsiveness in normoventilated cardiac surgical patients. Whenever changes in systemic vascular resistance are expected, the PiCCO plus system should be recalibrated.     

Changes in arterial pressure during mechanical ventilation

Mechanical ventilation induces cyclic changes in vena cava blood flow, pulmonary artery blood flow, and aortic blood flow. At the bedside, respiratory changes in aortic blood flow are reflected by "swings" in blood pressure whose magnitude is highly dependent on volume status. During the past few years, many studies have demonstrated that arterial pressure variation is neither an indicator of blood volume nor a marker of cardiac preload but a predictor of fluid responsiveness. That is, these studies have demonstrated the value of this physical sign in answering one of the most common clinical questions, Can we use fluid to improve hemodynamics?, while static indicators of cardiac preload (cardiac filling pressures but also cardiac dimensions) are frequently unable to correctly answer this crucial question. The reliable analysis of respiratory changes in arterial pressure is possible in most patients undergoing surgery and in critically ill patients who are sedated and mechanically ventilated with conventional tidal volumes.     

脉搏指示连续心排血量技术在心脏前负荷测量的应用近况

监测心脏负荷变化对了解心脏功能具有十分重要的临床意义。中心静脉压(CVP)与右心前负荷虽存在一定关系,但不能完全反映左心前负荷。经动脉插管入左心房及肺动脉漂浮导管(Swan-Ganz导管)测量肺小动脉嵌顿压(PCWP)评估左心前负荷的方法,虽能为判断心脏前负荷提供较为可靠的依据,     

Hypovolaemia

The determination of intravascular volume in haemodynamically unstable patients is key to subsequent management. Administration of fluid remains the cornerstone of treatment but fluid loading in those patients not responsive to fluid is detrimental to outcome, as interstitial oedema impedes tissue oxygenation. Traditionally, static markers of cardiac preload such as central venous pressure have guided fluid therapy. Such markers have been shown to poorly predict fluid responsiveness. This has led to increased interest in dynamic variables such as the fluctuation of blood pressure and stroke volume in response to mechanical ventilation. These variables use the cyclical changes induced by positive pressure ventilation on right and left ventricular loading to measure changes in left ventricular stroke volume and arterial pressure. These dynamic indices, termed systolic pressure variation, pulse pressure variation and stroke volume variation, are superior in predicting fluid responsiveness in mechanically ventilated patients with a regular cardiac rhythm. In patients with spontaneous respiratory effort, the response of stroke volume to a passive leg raise is also an accurate indicator of fluid status.     

心脏前负荷测量进展

心脏前负荷在临床应用有重要的指导价值,但监测方法各有利弊,单一温度稀释法PicCCo技术具有广阔的应用前景,较Swan-Ganz导管技术更敏感,可较准确监测心脏前负荷的变化,为指导临床诊断和治疗提供可靠的依据。因临床上受多种因素所影响,PiCCO所测得的胸腔内血容积等参数作为反映心脏前负荷的指标,仍需进行更深入的分析与探讨。目前在临床上还不能忽视传统技术的应用。     

Assessment of volume responsiveness in mechanically ventilated patients

Monitoring and management of intravascular volume status is of crucial importance in critically ill patients. Hypovolemia, induced by hemorrhage or pathologic fluid shifts in the presence of systemic inflammation, is frequently the cause for hemodynamic instability and hypotension. This deficit of central blood volume leads to a reduction in biventricular cardiac preload. With respect to the Frank-Starling mechanism, this causes an alteration in left ventricular stroke volume. If this reduction in stroke volume cannot be compensated by an increase in heart rate, this finally results in a decline of cardiac output. In this clinical situation fluid loading is the treatment of choice. However, insufficient peripheral vascular resistance and thus reduced cardiac afterload as well as impaired myocardial contractility also have to be taken in account to be causative for hypotension. Potential hazards of fluid loading specifically in the latter situation include pulmonary edema, worsening of pulmonary gas exchange and myocardial failure. Thus, prediction of fluid responsiveness, i.e. the prediction of the hemodynamic response to fluid loading is of utmost importance in critically ill patients. Several conventional parameters of systemic hemodynamic monitoring such as the cardiac filling pressures CVP and PAOP, the estimation of the left ventricular end-diastolic area (LVEDA) by echocardiography and measurement of central blood volumes as the right-ventricular end-diastolic volume (RVEDV) or the global end-diastolic volume (GEDV) by thermodilution are frequently used for preload monitoring. Further, functional preload parameters such as the left ventricular stroke volume variation (SW), describing the specific interactions of the heart and the lungs under mechanical ventilation, have been recently proposed to be useful for predicting fluid responsiveness. Thus, it is the aim of the present article to analyze these different concepts of hemodynamic monitoring regarding their usefulness and clinical applicability to predict fluid responsiveness at the bedside.     

Assessment of intrathoracic blood volume as an indicator of cardiac preload: single transpulmonary thermodilution technique versus assessment of pressure preload parameters derived from a pulmonary artery catheter.

OBJECTIVE: To analyze the clinical value of a new device (PiCCO) for cardiac output measurement and volume preload parameter assessment, based on transpulmonary thermodilution technique, as an alternative to the pulmonary artery thermodilution technique and assessment of pressure preload parameters derived from the pulmonary artery catheter. DESIGN: Prospective, controlled, clinical study. SETTING: University hospital. PARTICIPANTS: Eighteen patients with ejection fraction >50% undergoing coronary artery bypass graft surgery. INTERVENTIONS: A baseline measurement was performed after induction of anesthesia under clinical steady-state conditions (T1). Hypovolemia, defined as central venous pressure (CVP) <10 mmHg and pulmonary capillary wedge pressure (PCWP) <12 mmHg, was treated by infusion of 6% hydroxyethyl starch 200/0.5 (7 mL/kg). After 10 minutes, a second measurement (T2) was performed. MEASUREMENTS AND MAIN RESULTS: The mean difference (bias) between transpulmonary thermodilution cardiac output and pulmonary artery thermodilution cardiac output did not differ at the 2 sample points. Changes in pressure preload parameters of the pulmonary artery catheter (CVP, PCWP) did not correlate with changes in cardiac output or stroke volume, whereas changes in volume preload parameter intrathoracic blood volume (ITBV) of the PiCCO correlated significantly with changes in cardiac output and stroke volume (r = 0.55, p < 0.05; r = 0.62, p < 0.01). CONCLUSION: These results suggest that increased cardiac preload is more reliably reflected by ITBV than by CVP or PCWP. The assessment of ITBV by the transpulmonary single indicator dilution technique is an interesting alternative to the pressure preload parameters.     

Retrospektive Analyse von transpulmonal und pulmonalarteriell gemessenem Herzzeitvolumen bei ARDS-Patienten

Objectives: To investigate the agreement (and its potential dependency on extravascular lung water) between transpulmonary (TPID) and standard pulmonary artery (PAID) thermodilution cardiac output measurements. Methods: One hundred and sixty simultaneous cardiac output measurements using transpulmonary and pulmonary artery thermodilution techniques were retrospectively compared in 18 patients with acute respiratory distress syndrome. In addition, extravascular lung water was determined using a double indicator technique (temperature and indocyanine green). Results: Mean (±SD) difference (’’bias’’) was 0.03?L/min (±1.04?L/min), linear regression analysis resulted in TPID=0.87 PAID+1.16 (r=0.91). Mean extra vascular lung water was 1625?mL (minimum–maximum: 403–3266?mL) and therefore markedly elevated as could have been expected in patients with ARDS. Bias (PAID-TPID) was not dependent on extravascular lung water. Conclusions: Transpulmonary and pulmonary artery thermodilution methods can be used interchangeably. The results demonstrate for the first time in humans that transpulmonary thermodilution provides valid cardiac output values in patients with markedly increased fluid content of the lungs.     

Utilization of Bioreactance Technique as Indicator for Preload Responsiveness During Living Donor Liver Donation

Background

Fluid restriction has been used to decrease central venous pressure as a strategy of fluid management during living donor liver donation (LDLD). However, potential risks such as hemodynamic instability are also involved during the procedure. Monitoring of preload or preload responsiveness is therefore crucial during LDLD. The aim of this study was to explore the efficiency of an innovative bioreactance method that introduced the noninvasive cardiac output monitor (NICOM, Cheetah Medical, Vancouver, Wash, United States), as surrogate indicator for preload responsiveness during LDLD.

Methods

Twenty-six patients underwent LDLD and were enrolled in this study. Fluid was restricted until the organ was harvested. The ultrasonic cardiac output monitor (USCOM Ltd, Sydney, Australia) was applied to measure stroke volume (SV) before and after 500 mL of 6% hydroxyethyl starch 130/0.4 (Voluven, Fresenius Kabi, Friedberg, Germany) fluid challenge, and the value of SV variation (SVV) from NICOM was also recorded. Fluid responsiveness was defined if SV increased by more than 15%. Receiver operating characteristic (ROC) curve was performed.

Results

The area under the ROC curve was 0.6023. The optimal cutoff value of SVV from NICOM was 12% during LDLD.

Conclusions

Our study has shown that SVV measured from the bioreactance technique is a poor indicator for monitoring preload responsiveness during LDLD.     

Intrathoracic blood volume as an end point in resuscitation of the severely burned: an observational study of 24 patients

BACKGROUND: Treatment of burn shock according to empirical resuscitation formulas is still considered the gold standard, and the burn community does not advocate the use of invasive cardiorespiratory monitoring in general. As a consequence, data dealing with early postburn hemodynamics are sparse, and only few studies have paid attention to the topic of end-point burn shock resuscitation. However, recent studies have suggested that burn survival may be improved when invasive monitoring is used to guide fluid therapy during the shock phase. MATERIALS AND METHODS: In an observational study of 24 patients with severe burns, the transpulmonary double indicator dilution technique was used for semi-invasive hemodynamic monitoring. The clinical utility of the intrathoracic blood volume (ITBV) as an end-point variable for fluid resuscitation was evaluated, comparing correlation of filling pressure obtained by a pulmonary artery catheter and intrathoracic blood volume to cardiac index and oxygen delivery. In addition fluid volume predicted by the Parkland burn formula was compared with the actual fluid volume given when ITBV was used as end point for resuscitation. RESULTS: ITBV-guided resuscitation was associated with restoration of preload and peripheral delivery of oxygen within 24 hours in the majority of patients. Augmentation of ITBV was significantly correlated with changes in cardiac index and oxygen transport rate. No such correlation could be demonstrated for the conventional preload parameters such as central venous pressure and pulmonary capillary wedge pressure. Thus, ITBV seemed in burned, hypovolemic patients a better indicator of the preload component of the cardiac output than the conventional preload parameters obtained with the pulmonary artery catheter. Significantly larger volumes of crystalloids than predicted by the Parkland formula were administered when ITBV was used as end point for resuscitation. The extravascular lung water remained normal during this extraordinary high volume load. CONCLUSION: ITBV may be a reliable preload indicator to guide volume therapy in life-threatening burns, and end-point-fixed resuscitation to this parameter seems to be associated with significantly higher fluid administration than calculated compared with traditional burn formulas. The effects of burn resuscitation to fixed end points on survival and multiple organ failure should be evaluated in future randomly assigned trials.     

Transpulmonale Indikatorverfahren in der Intensivmedizin

The management of critically ill patients often requires an advanced hemodynamic monitoring. Beside pulmonary artery catheter (PAC) and transesophageal echocardiography (TEE) the transpulmonary indicator dilution technique (TPID) with arterial registra-tion of the indicator dilution curves is a possi-ble approach to get additional hemodynamic information. Being less invasive, measurements of cardiac output by trans-pulmonary thermodilution are as reliable as the thermodilution using a PAC.Transpulmonary thermodilution can be used even in small children. In addition, intrathoracic blood volume (ITBV) and extravascular lung water (EVLW) can be estimated. ITBV seems to be a better surrogate of cardiac filling than central venous pressure and pulmonary capillary wedge pressure. EVLW can be of special value in the fluid-management of patients with systemic inflammatory response syndrom or acute respiratory failure. By using the dye indocyanine green (ICG) as a second indicator TPID can be performed as transpulmonary double indicator dilution technique. The resulting thermodilution and dye curves are measured with a combined fiberoptic-thermistor catheter. This allows the more accurate measurement of ITBV and EVLW and in addition the assessment of total circulating blood volume and ICG-clearance. ICG-clearance serves clinically as a rapidly reacting indirect measure of liver function. As with the other methods of advanced hemodynamic monitoring the data available at present do not show a positive effect on the incidence of organ failure and mortality by monitoring critically ill patients with TPID. Before applying an advanced hemodynamic monitoring it should be asked critically which parameter is needed for the therapy-management of the individual patient. Based on this a differenciated monitoring decision has to be made.     

Pulse contour analysis for cardiac output monitoring in cardiac surgery for congenital heart disease

Conventional methods of cardiac output monitoring using pulmonary artery catheters may not be feasible in patients with congenital heart disease because of patients' small size or aberrant anatomy. We studied the accuracy of a new device, which uses pulse contour analysis to measure continuous cardiac output, in children and adults undergoing congenital heart surgery. Sixteen patients, median ages 7 yr old, were included in this prospective study. One-hundred-ninety-one data points were obtained in the pre- and postcardiopulmonary bypass periods and in the first 12 h after intensive care unit admission. We evaluated the relationship between cardiac index (CI) derived from transpulmonary thermodilution (TDCI) and CI derived from pulse contour analysis (PCCI). Bias and limits of agreement between TDCI and PCCI over all time periods were 0.1 +/- 1.94, indicating a wide dispersion of the data. Coefficient of correlation (r) between the TDCI and PCCI was 0.7. Although in previous studies, PCCI has been suggested to be accurate in adult cardiac surgery, we found it to be less reliable in our study patients, even after shunt correction. The relationships of the volume and pressure based measures of preload, intrathoracic blood volume index (ITBI), and central venous pressure with CI were also investigated. After repair, correlation (r) between PCCI or TDCI and ITBI (0.56 and 0.71, respectively) was better than that between PCCI or TDCI and CVP (0.16 and 0.11, respectively), indicating greater validity of ITBI as a measure of preload. IMPLICATIONS: Our results suggest that the pulse contour analysis cardiac output (CO) monitoring in patients undergoing congenital heart surgery may not provide as accurate or reliable measures of CO as previously suggested. The volume-based variable of preload intrathoracic blood volume index (ITBI) has better correlation with cardiac index (CI) than the central venous pressure, suggesting that ITBI may be a better indicator of preload.     

HZV-Bestimmung mittels transpulmonaler Thermodilution Eine Alternative zum Pulmonaliskatheter?

Cardiac output measurements are often helpful in the management of critically ill patients and high risk-patients. In this study an alternative technique for measurement of cardiac output by the transpulmonary indicator dilution technique (TPID) was evaluated in comparison to conventional thermodilution using a pulmonary artery catheter. With TPID, a thermistor-tipped catheter (the smallest available is 1.3 F) is placed in the aorta via a femoral artery introducer. Thus, TPID can also be used in very small children in whom placement of a pulmonary artery catheter may be difficult or even impossible. In principle, TPID is less invasive since the possible complications of the pulmonary catheters are avoided. We investigated the accuracy and reproducibility of transpulmonary thermodilution in patients over a broad range in age and body surface. Methods. Following approval by the ethics committee and written consent, the data were obtained from 21 patients without a circulatory shunt undergoing diagnostic heart catheterization. The patients were between 0.5 and 25.2 years old, their body surface between 0.35 and 1.89 m². Measurements were performed in duplicate with bolus injections of ice-cold normal saline (0.15 ml/kg), randomly spread over the respiratory cycle. In total 48 thermodilution curves were measured simultaneously in the pulmonary artery and in the aorta. Thermodilution curves were monoexponentially extrapolated for elimination of recirculation and cardiac output was calculated with a standard Stewart Hamilton procedure. Results. The amplitude of the typical arterial thermodilution curve shows a smaller and more delayed course than the pulmonary artery thermodilution curve. There was a very good correlation between the values found by pulmonary and TPID cardiac output measurements (R=0.968). There was a slightly smaller cardiac output value measured by the TPID (Bias=?4.7±1.5% sem) The reproducibility of duplicate measurements with the two methods were nearly the same, the standard deviation of the difference was 10.9% for the pulmonary thermodilution method and 11.7% for TPID. Discussion. TPID gives an alternative technique for measurement of cardiac output. We showed over a broad range in age and body surface a very good correlation with thermodilution measurements in the pulmonary artery. The slightly smaller values for TPID are explained by early recirculation, for clinical purposes the difference is negligible. However, the reproducibility of a method is clinically very important. Both methods showed in duplicate measurements basically the same reproduciblity. The disadvantage of TPID in being more sensitive to baseline alteration is counterbalanced by less respiratory variability in comparison to the conventional thermodilution technique. However, by increasing the amount of injected indicator (i.e., 0.2 ml/kg?15 ml in an adult) it is possible to reduce the effect of baseline alteration. By using fiberoptic catheters it is even possible to use TPID as double-indicator dilution technique to measure intrathoracic blood volume (ITBV) and extravascular lung water (EVLW). We conclude that in many patients TPID might be an attractive, less invasive and reliable alternative to conventional cardiac output measurement by pulmonary artery catheter.     

Kardiale Vorlast und zentraler Venendruck

The force of cardiac contraction is strongly influenced by myocardial fibre length at the beginning of systole. Because the length of cardiac sarcomers and muscle fibres primarily depends on the end-diastolic ventricular volume, filling pressures a priori can only act as indirect parameters of cardiac preload. Central venous pressure (CVP) gives information on right ventricular end-diastolic pressure, which parallels changes in left ventricular end-diastolic pressure as long as ventricular function is not impaired. Since the pressure-volume relationship of cardiac ventricles is not linear and shows great variability, filling of the ventricles cannot be directly derived from end-diastolic pressure. Further limitations of CVP as a surrogate variable of preload are caused by the influence of intrathoracic and intra-abdominal pressures. A valid parameter of preload should describe the relationship between preload and stroke volume as given by the Frank-Starling law. Furthermore, estimates of cardiac preload should enable prediction of fluid responsiveness. Many studies have demonstrated that under clinical conditions CVP cannot meet these demands and thus does not appear to be a useful predictor of cardiac preload. Variables which more directly represent end-diastolic ventricular volume (e.g. intrathoracic blood volume or end-diastolic ventricular area) offer a higher validity as estimates of cardiac preload. Furthermore, dynamic parameters of ventricular preload, such as pulse pressure variation or stroke volume variation, seem to be more predictive of volume responsiveness in ventilated patients than CVP. These limitations, however, do not impair the importance of CVP as the downstream pressure of the systemic venous system.     

Global end-diastolic volume as a variable of fluid responsiveness during acute changing loading conditions

OBJECTIVE: Dynamic variables of preload such as stroke volume variation (SVV) have been shown to be good predictors of fluid responsiveness. They are, however, not applicable during spontaneous breathing and cardiac arrhythmias. Volumetric variables of preload, such as global end-diastolic volume (GEDV) and left ventricular end-diastolic area (LVEDA), might be alternative variables of preload to guide fluid administration. Therefore, the present study was designed to evaluate whether GEDV and LVEDA are suitable parameters of preload and fluid responsiveness during rapidly changing loading conditions. DESIGN: Prospective animal study. SETTING: Animal laboratory of a university hospital. PARTICIPANTS: Fourteen pigs. INTERVENTIONS: The pigs were studied during changing loading conditions as follows: normovolemia, after removal of 500 mL of blood, and after retransfusion plus an additional 500 mL of 6% hydroxyethyl starch. Cardiac output (CO), stroke volume index (SVI), and GEDV were obtained by transpulmonary thermodilution. Additionally, CO, SVI, and SVV were monitored continuously by pulse-contour analysis. MEASUREMENTS AND MAIN RESULTS: Measurements of hemodynamic variables at each experimental stage were obtained after a period of stabilization. GEDV and LVEDA but not SVV, central venous pressure, and pulmonary capillary wedge pressure accurately reflected rapid changes in preload. When analyzing the correlation of percentage change of preload variables with the percentage change of SVI after fluid resuscitation, only SVV and GEDV showed a significant correlation with fluid responsiveness. CONCLUSIONS: In this animal model, GEDV and LVEDA were superior to SVV in accurately reflecting hemorrhage. However, GEDV and SVV but not LVEDA were suitable to predict fluid responsiveness.     

Assessment of cardiac output,intravascular volume status,and extravascular lung water by transpulmonary indicator dilution in critically ill neonates and infants

OBJECTIVE: To assess cardiac output, intrathoracic blood volume, global end-diastolic volume, and extravascular lung water in critically ill neonates and small infants using transpulmonary indicator dilution. DESIGN: Prospective, observational, clinical study. SETTING: Pediatric intensive care unit in a university hospital. PARTICIPANTS: Critically ill neonates and small infants suffering from severe heart failure, respiratory failure, or sepsis (n = 10). INTERVENTIONS: A total of 194 transpulmonary indicator dilution measurements were done. Global end-diastolic volume, intrathoracic blood volume, and stroke volume were measured and compared with standard hemodynamic parameters during the clinical course and before and after volume loading (16 +/- 3.7 mL/kg of 10% albumin solution) in 8 of 10 patients. MEASUREMENTS AND MAIN RESULTS: A positive correlation was found for stroke volume index versus global end-diastolic volume (r = 0.76, p < 0.001) and intrathoracic blood volume (r = 0.56, p < 0.001). In contrast, no correlation was observed for stroke volume index versus central venous pressure. Volume loading resulted in significant increases in stroke volume index (p < 0.01), global end-diastolic volume (p < 0.01), and intrathoracic blood volume (p < 0.01); whereas central venous pressure, heart rate, mean arterial pressure, and extravascular lung water remained unchanged. CONCLUSION: Transpulmonary indicator dilution enables measurement of cardiac output and intravascular volume status in critically ill neonates and infants at the bedside. The effects of volume loading on cardiac preload and effective change in stroke volume can be monitored by this technique, whereas central venous pressure was not indicative of changes in intravascular volume status.     

Stroke volume variation as an indicator of fluid responsiveness using pulse contour analysis in mechanically ventilated patients

Assessment of cardiac performance and adequate fluid replacement of a critically ill patient are important goals of a clinician. We designed this study to evaluate the ability of stroke volume variation (SVV), derived from pulse contour analysis, and frequently used preload variables (central venous pressure and pulmonary capillary wedge pressure) to predict the response of stroke volume index and cardiac index to volume replacement in normoventilated cardiac surgical patients. We studied 20 patients undergoing elective coronary artery bypass grafting. After the induction of anesthesia, hemodynamic measurements were performed before (T1) and subsequent to volume replacement by infusion of 6% hydroxyethyl starch 200/0.5 (7 mL/kg) with a rate of 1 mL x kg(-1) x min(-1). Except for heart rate, all hemodynamic variables changed significantly (P < 0.01) after volume loading. Linear regression analysis between SVV at baseline (T1) and DeltaSVV after volume application showed a significant correlation (r = -0.97; P < 0.01), whereas linear regression analysis between SVV (T1) and percentage changes of stroke volume index (r = 0.19) and cardiac index (r = 0.17) did not reveal a significant relationship between variables. The results of our study suggest that SVV derived from pulse contour analysis cannot serve as an indicator of fluid responsiveness in normoventilated cardiac surgical patients.     

Respiratory variations in pulse oximetry plethysmographic waveform amplitude to predict fluid responsiveness in the operating room

BACKGROUND: Respiratory variations in pulse oximetry plethysmographic waveform amplitude (DeltaPOP) are related to respiratory variations in pulse pressure (DeltaPP) and are sensitive to changes in preload. The authors hypothesized that DeltaPOP can predict fluid responsiveness in mechanically ventilated patients during general anesthesia. METHODS: Twenty-five patients referred for cardiac surgery were studied after induction of general anesthesia. Hemodynamic data (cardiac index, central venous pressure, pulmonary capillary wedge pressure, DeltaPP, and DeltaPOP) were recorded before and after volume expansion (500 ml hetastarch, 6%). Fluid responsiveness was defined as an increase in cardiac index of 15% or greater. RESULTS: Volume expansion induced changes in cardiac index (2.0+/-0.4 to 2.3+/-0.5 mmHg; P<0.05), DeltaPP (11+/-7 to 6+/-5%; P<0.05), and DeltaPOP (12+/-9 to 7+/-5%; P<0.05). DeltaPOP and DeltaPP were higher in responders than in nonresponders (17+/-8 vs. 6+/-4 and 14+/-7 vs. 6+/-4%, respectively; P<0.05 for both). A DeltaPOP greater than 13% before volume expansion allowed discrimination between responders and nonresponders with 80% sensitivity and 90% specificity. There was a significant relation between DeltaPOP before volume expansion and percent change in cardiac index after volume expansion (r=0.62; P<0.05). CONCLUSIONS: DeltaPOP can predict fluid responsiveness noninvasively in mechanically ventilated patients during general anesthesia. This index has potential clinical applications.     

Fluid challenge in patients at risk for fluid loading-induced pulmonary edema

BACKGROUND: This study evaluated the effects of protocol-guided fluid loading on extravascular lung water (EVLW) and hemodynamics in a group of patients at high risk for volume expansion-induced pulmonary and systemic edema. METHODS: Nine acutely admitted septic patients with acute lung injury (ALI) were prospectively studied. In addition to sepsis and ALI, the following criteria indicating increased risk for edema formation had to be fulfilled: increased vascular permeability defined as microalbuminuria greater than fivefold normal and hypoalbuminemia < 30 g l(-1). Two hundred-ml boluses of a 10% hydroxyethyl starch (HES) was titrated to obtain best filling pressure/stroke volume relation. Extravascular lung water and intrathoracic blood volume (ITBV) were measured using a transpulmonary double-indicator dilution technique. Baseline data were compared with data at the end of fluid loading and 3 h postchallenge. RESULTS: At study entry the mean EVLW was 13 ml kg(-1), and the mean EVLW/ITBV ratio (indicator of pulmonary permeability) was 0.72 (normal range 0.20-0.30). To attain optimal preload/stroke volume relation 633 +/- 240 ml of HES was needed. Fluid loading significantly increased preload (CVP, PAOP and ITBV), and stroke volume. Effective pulmonary capillary pressure (Pcap) rose only slightly. As a result, the Pcap-PAOP gradient decreased. Despite increased cardiac output, EVLW did not change by plasma expansion. CONCLUSION: In this selected group of at-risk patients, the optimization of cardiac output guided by the concept of best individual filling pressure/stroke volume relationship did not worsen permeability pulmonary edema.