Sebastian Haas

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.

Haemodynamics and cardiac function during robotic-assisted laparoscopic prostatectomy in steep Trendelenburg position.

Robotic‐assisted laparoscopic prostatectomy (RALP) is usually performed in steep Trendelenburg position, which can be associated with cardiac impairment due to positioning and capnoperitoneum. This study investigated haemodynamic consequences and cardiac function in this type of surgery and evaluated the hypothesis that steep Trendelenburg position and capnoperitoneum results in haemodynamic and ventricular impairment.

Changes in sevoflurane plasma concentration with delivery through the oxygenator during on-pump cardiac surgery

BACKGROUND It is unclear what factors affect the uptake of sevoflurane administered through the membrane oxygenator during cardiopulmonary bypass (CPB) and whether this can be monitored via the oxygenator exhaust gas. METHODS Stable delivery of sevoflurane was administered to 30 elective cardiac surgery patients at 1.8 vol% (inspiratory) via the anaesthetic circuit and ventilator. During CPB, sevoflurane was administered in the oxygenator fresh gas supply (Compactflo Evolution™; Sorin Group, Milano, Italy). Sevoflurane plasma concentration (SPC) was measured using gas chromatography. Changes were correlated with bispectral index (BIS), patient temperature, haematocrit, plasma albumin concentration, oxygenator fresh gas flow, and the sevoflurane concentration in the oxygenator exhaust at predefined time points. RESULTS The mean SPC pre-bypass was 54.9 µg ml(-1) [95% confidence interval (CI): 50.6-59.1]. SPC decreased to 43.2 µg ml(-1) (95% CI: 40.3-46.1; P<0.001) after initiation of CPB, and was lower still during rewarming and weaning from bypass, 39.4 µg ml(-1) (95% CI: 36.6-42.3; P<0.001). BIS did not exceed a value of 55. SPCs were higher during hypothermia (P<0.001) and with an increase in oxygenator fresh gas flow (P=0.015), and lower with haemodilution (P=0.027). No correlation was found between SPC and the concentration of sevoflurane in the oxygenator exhaust gas (r=-0.04; 95% CI: -0.18 to 0.09; P=0.53). CONCLUSIONS The uptake of sevoflurane delivered via the membrane oxygenator during CPB seems to be affected by hypothermia, haemodilution, and changes in the oxygenator fresh gas supply flow. Measuring the concentration of sevoflurane in the exhaust from the oxygenator is not useful for monitoring sevoflurane administration during bypass.

Electrical impedance tomography (EIT) for quantification of pulmonary edema in acute lung injury.

BackgroundAssessment of pulmonary edema is a key factor in monitoring and guidance of therapy in critically ill patients. To date, methods available at the bedside for estimating the physiologic correlate of pulmonary edema, extravascular lung water, often are unreliable or require invasive measurements. The aim of the present study was to develop a novel approach to reliably assess extravascular lung water by making use of the functional imaging capabilities of electrical impedance tomography.MethodsThirty domestic pigs were anesthetized and randomized to three different groups. Group 1 was a sham group with no lung injury. Group 2 had acute lung injury induced by saline lavage. Group 3 had vascular lung injury induced by intravenous injection of oleic acid. A novel, noninvasive technique using changes in thoracic electrical impedance with lateral body rotation was used to measure a new metric, the lung water ratioEIT, which reflects total extravascular lung water. The lung water ratioEIT was compared with postmortem gravimetric lung water analysis and transcardiopulmonary thermodilution measurements.ResultsA significant correlation was found between extravascular lung water as measured by postmortem gravimetric analysis and electrical impedance tomography (r = 0.80; p < 0.05). Significant changes after lung injury were found in groups 2 and 3 in extravascular lung water derived from transcardiopulmonary thermodilution as well as in measurements derived by lung water ratioEIT.ConclusionsExtravascular lung water could be determined noninvasively by assessing characteristic changes observed on electrical impedance tomograms during lateral body rotation. The novel lung water ratioEIT holds promise to become a noninvasive bedside measure of pulmonary edema.

Thermodilution-derived indices for assessment of left and right ventricular cardiac function in normal and impaired cardiac function.

Objective:The aim of this study was to assess whether thermodilution-derived parameters of right and left ventricular cardiac function (right ventricular ejection fraction, global ejection fraction, cardiac function index) are able to track changes of cardiac contractile function and whether they are influenced by substantial preload reduction. Design:Prospective animal study. Setting:University-affiliated animal research laboratory. Subjects:Domestic pigs. Interventions:Sixteen domestic pigs were studied. Right ventricular ejection fraction, global ejection fraction, and cardiac function index were compared to direct measurement of left ventricular rate of maximum systolic pressure rise and the left ventricular rate of maximum systolic pressure rise corrected to preload. Measurements were done with normal cardiac function during normo- and hypovolemia. Thereafter, cardiac function was impaired by continuous infusion of verapamil and measurements were repeated during normo- and hypovolemia (withdrawal of blood 20 mL kg−1 body weight). Measurements and Main Results:With normal cardiac function, hypovolemia led to a significant decrease of right ventricular ejection fraction from 36.7% ± 6.6% to 29.8% ± 5.8% (p < .001), global ejection fraction from 40.5% ± 6.2% to 33.6% ± 7.6% (p < .001), and the left ventricular rate of maximum systolic pressure rise from 2104 ± 390 mm Hg sec−1 to 1297 ± 438 mm Hg sec−1 (p < .001). Cardiac function index (8.92 ± 2.20 min−1 to 7.93 ± 1.54 min−1) and the left ventricular rate of maximum systolic pressure rise corrected to preload (18.2 ± 4.7 mm Hg sec−1 mL to 15.2 ± 4.3 mm Hg sec−1 mL) did not change significantly. Infusion of verapamil led to a significant reduction of right ventricular ejection fraction, global ejection fraction, cardiac function index, the left ventricular rate of maximum systolic pressure rise, and the left ventricular rate of maximum systolic pressure rise corrected to preload (p < .001). Now, hypovolemia led to a significant decrease of right ventricular ejection fraction (29.1% ± 4.6% to 24.9% ± 5.9%; p < .001), global ejection fraction (37.1% ± 4.7% to 31.9% ± 3.9%; p < .05), cardiac function index (7.58 ± 1.02 to 6.27 ± 1.19 min−1; p < .05), and the left ventricular rate of maximum systolic pressure rise (733 ± 141 mm Hg sec−1 to 426 ± 108 mm Hg sec−1; p < .05). Only the left ventricular rate of maximum systolic pressure rise corrected to preload did not change significantly (6.7 ± 1.3 mm Hg sec−1 mL to 4.6 ± 1 mm Hg sec−1 mL; p > .05). Conclusions:Right ventricular ejection fraction, global ejection fraction, and cardiac function index enable detection of changes in load-independent, intrinsic cardiac contractility. Importantly, they also reflect changes of contractile function caused by substantial decrease of preload, emphasizing the importance of assessing both cardiac contractile function in coherence with cardiac preload to differentiate between reduced intrinsic contractility and hypovolemia.

Effects of one-lung ventilation on thermodilution-derived assessment of cardiac output

BACKGROUND Cardiac output (CO) monitoring can be useful in high-risk patients during one-lung ventilation (OLV), but it is unclear whether thermodilution-derived CO monitoring is valid during OLV. Therefore, we compared pulmonary artery (CO(PATD)) and transcardiopulmonary thermodilution (CO(TPTD)) with an experimental reference in a porcine model. METHODS CO(PATD) and CO(TPTD) were measured in 23 pigs during double-lung ventilation (DLV) and 15 min after the onset of OLV, during conditions of normovolaemia and after haemorrhage. An ultrasonic flow probe placed around the pulmonary artery (CO(PAFP)) was used for reference. RESULTS The range of CO in these experiments was 1.5-3 litre min(-1). Normovolaemia: during DLV and conditions of normovolaemia, the mean (95% limits of agreement) bias for CO(PATD) compared with CO(PAFP) was -0.05 (-0.92 and 0.83) litre min(-1), and 0.58 (-0.40 and 1.55) litre min(-1) for CO(TPTD). During OLV, the bias for CO(PATD) remained unchanged at 0.08 (-0.51 and 0.66) litre min(-1), P=0.15, and the bias for CO(TPTD) increased significantly to 0.85 (0.05 and 1.64) litre min(-1), P=0.047. Hypovolaemia: during DLV, the bias for CO(PATD) compared with CO(PAFP) was 0.22 (-0.20 and 0.66) litre min(-1) and for CO(TPTD) was 0.60 (0.12 and 1.10) litre min(-1). There was no significant change of bias during OLV for CO(PATD) [0.30 (-0.10 and 0.70) (litre min(-1)), P=0.25] or bias CO(TPTD) [0.72 (0.21 and 1.22) (litre min(-1)), P=0.14]. Trending ability during OLV, quantified by the mean of angles θ, showed good values for both CO(PATD) (θ=11.2°) and CO(TPTD) (θ=1.3°). CONCLUSIONS CO(TPTD) is, to some extent, affected by OLV, whereas CO(PATD) is unchanged. Nonetheless, both methods provide an acceptable estimation of CO and particularly of relative changes of CO during OLV.

Comparison of an automated respiratory systolic variation test with dynamic preload indicators to predict fluid responsiveness after major surgery

BACKGROUND Predicting the response of cardiac output to volume administration remains an ongoing clinical challenge. The objective of our study was to compare the ability to predict volume responsiveness of various functional measures of cardiac preload. These included pulse pressure variation (PPV), stroke volume variation (SVV), and the recently launched automated respiratory systolic variation test (RSVT) in patients after major surgery. METHODS In this prospective study, 24 mechanically ventilated patients after major surgery were enrolled. Three consecutive volume loading steps consisting of 300 ml 6% hydroxyethylstarch 130/0.4 were performed and cardiac index (CI) was assessed by transpulmonary thermodilution. Volume responsiveness was considered as positive if CI increased by >10%. RESULTS In total 72 volume loading steps were analysed, of which 41 showed a positive volume response. Receiver operating characteristic (ROC) curve analysis revealed an area under the curve (AUC) of 0.70 for PPV, 0.72 for SVV and 0.77 for RSVT. Areas under the curves of all variables did not differ significantly from each other (P>0.05). Suggested cut-off values were 9.9% for SVV, 10.1% for PPV, and 19.7° for RSVT as calculated by the Youden Index. CONCLUSION In predicting fluid responsiveness the new automated RSVT appears to be as accurate as established dynamic indicators of preload PPV and SVV in patients after major surgery. The automated RSVT is clinically easy to use and may be useful in guiding fluid therapy in ventilated patients.

Bispectral index guided titration of sevoflurane in on-pump cardiac surgery reduces plasma sevoflurane concentration and vasopressor requirements: a prospective, controlled, sequential two-arm clinical study.

BACKGROUND Electroencephalographic-based monitoring systems such as the bispectral index (BIS) may reduce anaesthetic overdose rates. OBJECTIVE We hypothesised that goal-directed sevoflurane administration (guided by BIS monitoring) could reduce the sevoflurane plasma concentration (SPC) and intraoperative vasopressor doses during on-pump cardiac surgery. DESIGN A prospective, controlled, sequential two-arm clinical study. SETTING German university medical centre with more than 2500 cardiac surgery interventions per year. PATIENTS Sixty elective on-pump cardiac surgery patients. INTERVENTION In group Sevo1.8% (n = 29), the sedation depth was maintained with a sustained inspired concentration of sevoflurane 1.8% before and during cardiopulmonary bypass (CPB). In group SevoBIS (n = 31), the inspired sevoflurane concentration was titrated to maintain a BIS target between 40 and 60. OUTCOME MEASURES SPC during CPB and the intraoperative administration of noradrenaline. Additional analyses were performed on intraoperative awareness, postoperative blood lactate concentration, duration of mechanical ventilation, intensive care unit length of stay and kidney injury. RESULTS Mean inspired sevoflurane concentration was 0.8% in group SevoBIS, representing a 57.1% reduction (P < 0.001) compared with group Sevo1.8%. The mean SPC was 42.3 &mgr;g ml−1 [95% confidence interval (CI) 40.0 to 44.6] in group Sevo1.8% and 21.0 &mgr;g ml−1 (95% CI 18.8 to 23.3) in group SevoBIS, representing a 50.2% reduction (P < 0.001). During CPB, the mean cumulative dose of noradrenaline administered was 13.48 &mgr;g kg−1 (95% CI 10.52 to 17.19) in group Sevo1.8% and 4.06 &mgr;g kg−1 (95% CI 2.67 to 5.97) in group SevoBIS (P < 0.001). Pearsons correlation coefficient (between the cumulative applied dosage of sevoflurane calculated from the area under the curve of the SPC over time and the administered cumulative noradrenaline dose) was 0.607 (P < 0.001). No intraoperative awareness signs were detected. CONCLUSION BIS-guided titration of sevoflurane reduces the SPC and decreases noradrenaline administration compared with routine care during on-pump cardiac surgery.

Prediction of volume-responsiveness during one-lung ventilation: a comparison of static, volumetric, and dynamic parameters of cardiac preload.

OBJECTIVES The aim of this study was to evaluate the ability of static, volumetric, and dynamic parameters of cardiac preload to predict volume responsiveness during one-lung ventilation (OLV). DESIGN Prospective experimental study. SETTING Laboratory of the animal facility of the University Medical Center Hamburg-Eppendorf. PARTICIPANTS Twenty-three German domestic pigs. INTERVENTIONS Hypovolemia was induced by withdrawing 20 mL/kg body weight (BW) of blood. OLV was established, and the volume withdrawn was re-transfused in 3 volume-loading steps, each consisting of 7 mL/kg BW. An ultrasonic flow probe around the pulmonary artery was used to measure the stroke-volume index (SVI) and to evaluate the volume response. An increase in the SVI of ≥ 15% was considered a positive response. For each measurement time point, central venous pressure (CVP), left atrial pressure (LAP), the global end-diastolic volume index (GEDI), stroke-volume variation (SVV), and pulse-pressure variation (PPV) were recorded. The ability to predict volume responsiveness was assessed using ROC analysis. MEASUREMENTS AND MAIN RESULTS A total of 69 volume loading steps were performed, 48 of which showed a positive volume response. ROC analysis revealed the following area under the curve (AUC) values: CVP, 0.88; LAP, 0.65; GEDI, 0.75; SVV, 0.78; and PPV, 0.83. A comparison of the areas under the ROC curves did not reveal any statistically significant differences (p>0.05), with the exception of LAP compared with CVP (p = 0.005). CONCLUSIONS Under these OLV experimental conditions, the volumetric and dynamic parameters of preload, as well as CVP, seemed to be of similar value in predicting volume responsiveness.

A novel flexible cryoprobe for EUS-guided pancreatic biopsies

BACKGROUND EUS-guided FNA (EUS-FNA) is an established technique for the cytologic diagnosis of pancreatic disease. Attempts to obtain adequate histologic specimens have yielded variable and mostly insufficient results. OBJECTIVE To evaluate the safety, feasibility, and quality of histologic biopsy specimens obtained by using a new cryobiopsy probe and to compare them with standard EUS-FNA and (laparoscopic) trucut biopsy specimens of pancreatic tissue. DESIGN Animal non-survival study. INTERVENTION Eighty-four pancreatic biopsy specimens (12 per group) were obtained in 4 anesthetized pigs by using one of the following the 18-gauge flexible cryoprobe; a conventional, 19-gauge, EUS-FNA needle; or a rigid, trucut biopsy device (18 gauge). The latter, used in laparoscopic surgery, was considered as the criterion standard for obtaining histology specimens. MAIN OUTCOME MEASUREMENTS Specimens were evaluated for artifacts and specimen quality by a blinded pathologist who used a 7-point Likert scale to assess histologic adequacy. Biopsy size and bleeding time after biopsy also were recorded. RESULTS The new cryoprobe was equivalent to the rigid, trucut needle and superior (P < .001) to the conventional 19-gauge FNA needles with respect to artifacts, quality of the specimen, biopsy specimen size, and bleeding. LIMITATIONS Animal model. CONCLUSION EUS-guided cryobiopsy was associated with better specimen quality for histologic analysis and a shorter bleeding time compared with a conventional 19-gauge FNA needle in the animal model. It is a promising new technique for histologic examination of pancreatic tissue.