[Manual skills in anaesthesiology]. / Erlernen von manuellen Fähigkeiten in der Anästhesie.

Assessment in anaesthesia traditionally takes the form of written papers and oral examinations. These are important for assessing trainee's knowledge and judgement, but do not test for competency in practical skills, which is essential for successful clinical practice. The presence of learning curves for practical skills in anaesthesia is now well recognized and they are useful tools to monitor a learning process. From these, estimates of the number of procedures that must be performed by trainees in order to reach an acceptable success rate can be produced. It is clear that these figures give some help for the rational design of training programs, however, numbers alone do not provide a sufficient basis to declare a trainee competent for a given procedure. Not only technical skills need to be taught, but also decision-making and even more important behavioral skills. In clinical practice there are often problems in providing all the necessary training on patients and by this reorganization of residency programs may be necessary. However, the role of medical simulation in the assessment of anesthetists in training is still unclear, and the introduction of simulator-based tests may be premature.

Haemodynamic monitoring.

The monitoring of cardiovascular function is an indispensable element in anaesthesia. A thorough understanding of pathophysiology in various disease states allows optimal balancing of the invasiveness and completeness of haemodynamic monitoring. The prevention of both intraoperative and postoperative complications is therefore a primary goal.

Contractility in humans after coronary artery surgery.

BACKGROUND: Propofol's unique pharmacokinetic profile offers advantages for titration and rapid emergence in patients after coronary artery bypass graft (CABG) surgery, but concern for negative inotropic properties potentially limits its use in these patients. The current study analyzed the effect of various propofol plasma concentrations on left ventricular (LV) contractility by means of a single-beat contractile index based on LV maximal power (PWR(max)). METHODS: The study was conducted in 30 patients after CABG surgery. Immediately after admission to the intensive care unit (ICU), four different plasma concentrations of propofol 0.65, 1.30, 1.95, and 2.60 microg/ml were established. At each concentration level, the cardiac and vascular effects of propofol were studied by combining echocardiographic data with invasively derived aortic root pressure. Preload was characterized by LV end-diastolic dimensions. Afterload was indicated in terms of indexed systemic vascular resistance (SVRI), LV end-systolic meridional wall stress (LV-ESWS), and arterial elastance (Ea). Quantification of effects on contractility was achieved by preload-adjusted PWRmax. RESULTS: Myocardial contractility did not change during a fourfold increase in propofol plasma concentration. Preload-adjusted PWRmax amounted to 3.90+/-1.75 W x ml(-2) x 10(4), 3.98+/-1.69, 3.94+/-1.70, and 3.88+/-1.72, respectively (mean+/-SD). With respect to ventricular loading conditions, propofol caused a significant reduction in both pre- and afterload. CONCLUSIONS: The current results strongly suggest that propofol lacks direct cardiac depressant effects. Nevertheless, meaningful vascular actions of propofol could be demonstrated. Significant decreases in ventricular loading conditions accounted for a marked decrease in arterial blood pressure and supported the concept that propofol in clinically relevant concentration is a vasodilator.

Assessment of cardiovascular volume status by transoesophageal echocardiography and dye dilution during cardiac surgery.

Conventional evaluation of cardiovascular volume status by filling pressures is unreliable in critically ill patients. Measurements of left ventricular end diastolic area index by transoesophageal echocardiography and of intrathoracic blood volume index by dye indicator dilution are new approaches to this problem. In this study, different indices of cardiovascular volume status were analysed to define their relation during the pronounced haemodynamic changes associated with systemic inflammation after cardiopulmonary bypass. Correlations were performed with left ventricular end diastolic area index, intrathoracic blood volume index, central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP). Data from 15 patients receiving coronary artery bypass grafts were compared after induction of anaesthesia and in the intensive care unit. Spearman's correlation coefficient for perioperative absolute changes in left ventricular end diastolic area index and intrathoracic blood volume index was 0.87 (P < 0.05). However, an increase in intrathoracic blood volume index by 125 mL m-2 was necessary to maintain a baseline left ventricular end diastolic area index. Absolute values of all variables varied widely, with the only significant correlation found between CVP and PCWP. Changes in CVP and PCWP did not correlate with changes in left ventricular end diastolic area index or intrathoracic blood volume index. Provided simultaneous baseline measurements are available and a supranormal intrathoracic blood volume index compensates for the haemodynamic changes in systemic inflammation, left ventricular end diastolic area index and intrathoracic blood volume index may substitute for each other during the evaluation of cardiovascular volume status in patients with stable cardiac function.

Evaluation of transesophageal echocardiography as a diagnostic and therapeutic aid in a critical care setting.

OBJECTIVES: To assess the impact of transesophageal echocardiography (TEE) on therapeutic management in relation to pulmonary artery catheterization (PAC) in the ICU. DESIGN: Retrospective analysis of 108 consecutive TEE video and related patient files during a 7-month period. SETTING: A 33-bed medical and surgical ICU. METHODS: All critically ill patients with or without PAC in whom a TEE was performed, excluding postoperative cardiac surgical patients. Patients were divided in a cardiac and a septic group depending on the primary disease on admission to the ICU. The impact of TEE in relation to PAC on ICU management was evaluated in whether therapy changes were performed strictly on the basis of the TEE findings. MAIN RESULTS: Of 64% of patients with a PAC, 44% underwent therapy changes after TEE: 41% in the cardiac and 54% in the septic subgroup. In 41% of patients without a PAC, TEE led to a change in therapy. CONCLUSIONS: TEE results in altered therapeutic management in at least one third of our (noncardiac surgery) ICU patient population independent of the presence of a PAC.

Doppler evaluation of right ventricular outflow impedance during positive-pressure ventilation.

Positive-pressure ventilation has often been advocated to increase oxygen delivery. This ventilation mode itself, however, can impair right ventricular ejection and, thus, diminish cardiac output. In this study, alterations of right ventricular outflow impedance were evaluated after stepwise increases of positive end-expiratory pressure (PEEP). Different pulmonary artery flow characteristics were evaluated with transesophageal echocardiography in mechanically ventilated postoperative coronary artery bypass surgery patients without pulmonary hypertension. A progressive decrease of pulmonary artery flow velocity and time velocity integrals was found with increasing PEEP levels. No changes in acceleration time or pre-ejection period were observed. In order to decrease the influence of heart rate, the ratios of the different pulmonary artery flow characteristics were calculated. At end-inspiration, both the ratio of acceleration time to right ventricular ejection period and the ratio of pre-ejection period to right ventricular ejection period showed progressive increases above 10 cmH2O positive end-expiratory pressure (13.3% at the level of 15 cmH2O and 8.5% at the level of 20 cmH2O). In this study, acceleration time appears not to be of importance in ventilated patients. These data strongly support the hypothesis that intermittent squeezing of the pulmonary arterial tree during inspiration, rather than positive end-expiratory pressure, creates an increase of right ventricular outflow impedance.

Acute hemodynamic changes of pressure-controlled inverse ratio ventilation in the adult respiratory distress syndrome. A transesophageal echocardiographic and Doppler study.

Twelve patients with the adult respiratory distress syndrome were included in this study and evaluated by transesophageal echocardiography and Doppler, assessing right and left ventricular intracardiac blood flow alterations with progressive increase of inspiration-to-expiration (I-E) ratios. Whereas midpulmonary artery flow parameters did not show any change, early left ventricular filling demonstrated a significant increase after switching the ventilatory mode from volume to pressure-controlled ventilation with 2:1 I-E ratio (end-inspiration: 39 +/- 26 cm with positive end-expiratory pressure [PEEP]-ventilation to 68 +/- 56 cm with pressure-controlled inverse-ratio ventilation, 2:1; p < 0.01; at end-expiration, from 67 +/- 21 cm with PEEP-ventilation to 83 +/- 36 cm with pressure-controlled ventilation 1:1; p < or = 0.05), resulting probably from different ventilatory flow and pressure curves. In the meanwhile, cardiac index demonstrated a significant augmentation (from 4.73 +/- 1.71 L/min.m2 to 5.56 +/- 1.66 L/min.m2; p < 0.05). Pressure-controlled inverse ratio ventilation results in both respiratory and hemodynamic advantages as is demonstrated by this study.

Transesophageal Echo-doppler evaluation of the hemodynamic effects of positive-pressure ventilation after coronary artery surgery.

Transesophageal echocardiography was used to extend knowledge about the impact of positive end-expiratory pressure (PEEP) during mechanical ventilation on right and left ventricular function and right ventricular impedance. At 20 cmH2O PEEP, a progressive increase of right ventricular end-diastolic area was seen (27%) that coincided with a reduction of early left ventricular filling velocity (25%) across the mitral valve, and a decrease of both pulmonary artery flow velocity (end-expiration 27% and end-inspiration 42%) and time-velocity index (end-inspiration 25%). As these changes were not accompanied by a change of the fractional area of contraction, the increase of the right ventricular diameter might be explained by right ventricular compensation due to an imbalance between augmented right ventricular impedance and reduced venous return.

Evaluation of the hemodynamic and respiratory effects of inverse ratio ventilation with a right ventricular ejection fraction catheter.

Pc-IRV has been shown to have respiratory advantages, compared with CPPV. However, the hemodynamic effects of this ventilation mode have not yet been fully elucidated. We used a REF catheter to monitor the hemodynamic changes in the RV. Fifteen ARDS patients were included in the study. The respiratory data showed a 35 percent decrease of PIP and a 32 percent decrease of VTi and VTe with Pc-IRV 4:1 compared with CPPV. Hemodynamic parameters showed a significant incrase in CI (17 percent) in Pc-IRV 4:1, without change in REF. Observing in retrospect the pressure-volume relationship of the RV, we could differentiate a preload (group 1) and an afterload dependent group of patients (group 2), CI was significantly different in the two groups as it rose only in the preload-dependent patients. RVEDVI showed a significant change in group 1, whereas this was absent in the second group. REF was maintained in switching ventilation from CPPV to Pc-IRV with increasing I:E ratio. Pc-IRV appears to be a good alternative ventilatory mode in comparison with CPPV in a selected group of patients with preload dependency (responders); in these patients with respiratory insufficiency, close hemodynamic monitoring is required to optimize ventilation, especially in relation to the hemodynamic effects.

Hemodynamic effects of dopexamine in patients following coronary artery bypass surgery.

Dopexamine is a new dopamine analogue, with combined agonist properties on dopamine receptors and the beta 2-adrenoceptor. The aim of this study was to evaluate the short-term hemodynamic effects of dopexamine at different dosage rates in postoperative coronary artery bypass (CABG) patients, especially with respect to the right ventricle, using a right ventricular ejection fraction pulmonary artery catheter. With a dose of 2 micrograms/kg/min of dopexamine, significant increases in heart rate (25%), cardiac index (33%), and right ventricular ejection fraction (20%) were observed. Pulmonary vascular resistance decreased with a dose over 1 microgram/kg/min (15%). Mean arterial blood pressure and pulmonary artery pressures were not affected. At 4 micrograms/kg/min, cardiac index was further increased. In conclusion, dopexamine could be beneficial to patients with a compromised right ventricle by lowering afterload and improving ventricular performance after CABG.