We examined hemodynamic and autonomic components of blood pressure responses during active and passive stressor tasks in a sample of young, normotensive men and women who were physically active but differed on fitness (i.e., [V below dot]O2peak). During the hand cold pressor, increases in systolic blood pressure were inversely related to fitness among women but not men. Regardless of gender, fitter participants had a greater increase in cardiac pace during mental arithmetic, coherent with a decreased cardiac-vagal component of heart rate variability, and a greater compensatory reduction in stroke volume. Fitness was otherwise unrelated to changes in cardiac output and vascular resistance during the stressor tasks. Our findings suggest that cardiorespiratory fitness augments the cardiac-vagal withdrawal that is characteristic of mental arithmetic. The blunted systolic blood pressure response to the hand cold pressor among fitter women suggests that cardiorespiratory fitness should be considered as a covariate in studies that examine the hand cold pressor as a predictor of future hypertension among women.

Background and objective: Induction of general anaesthesia in combination with positive-pressure ventilation is often associated with a significant decrease of arterial pressure. A decreased preload may contribute to this phenomenon. The aim was to investigate whether a change in cardiac filling occurs following the induction of general anaesthesia with sufentanil under typical clinical conditions.

Methods: Fifteen patients scheduled for elective coronary bypass grafting were studied immediately before surgery. In addition to standard monitors, a transpulmonary double-indicator dilution technique measured in vivo intrathoracic blood volume, global end-diastolic volume and total circulating blood volume. For induction of anaesthesia 2 μg kg−1 sufentanil was given. Measurements were performed awake and after the induction of anaesthesia, intubation and mechanical ventilation of the lungs.

Results: To maintain arterial pressure during the induction period within −20% of baseline pressure, on average 22 ± 6 mL kg−1 crystalloids and 8 ± 6 mL kg−1 colloids were given. Despite these amounts of fluid, cardiac filling was decreased, whereas circulating blood volume increased significantly. Both central venous pressure and pulmonary capillary wedge pressure increased.

Conclusions: Induction of general anaesthesia with positive-pressure ventilation is regularly associated with a blood volume shift from intra- to extrathoracic compartments. Even in low-dose opioid monoanaesthesia with sufentanil – often regarded as relatively inert in haemodynamic terms – the phenomenon could be demonstrated as the primary cause of the often-observed decrease of arterial pressure. It seems, therefore, rationally justified to restore cardiac filling by generous administration of intravenous fluids, at least in patients with unaffected cardiac pump function. During induction of anaesthesia, central venous pressure and pulmonary capillary wedge pressure do not reliably indicate cardiac filling.

Background and objective Assessment of cardiac preload is of major importance in the management of critically ill patients. Echocardiographic determined left ventricular end-diastolic area and indicator dilution derived intrathoracic blood volume are used as surrogates for cardiac preload. However, no controlled comparison studies on the relationship between induced changes in end-diastolic area and intrathoracic blood volume and concomitant changes in stroke volume index are available.

Methods The effects of a change in body position on these variables were investigated in 10 anaesthetized patients.

Results Intrathoracic blood volume and end-diastolic area decreased by 18 ± 11% and 27 ± 13% respectively. Stroke volume index concomitantly decreased by 19 ± 11%. Correlation analysis revealed a close relation between stroke volume index and intrathoracic blood volume (r = 0.75) and end-diastolic area (r = 0.76).

Conclusions Within the observed range of data, intrathoracic blood volume and end-diastolic area are equivalent indices of cardiac preload.

The interrater reliability and concurrent validity of two methods of scoring the ensemble-averaged impedance cardiogram were evaluated. Impedance cardiographic and electrocardiographic signals were recorded from 40 undergraduate men and women during a baseline rest period and a vocal mental arithmetic task period. Recordings were scored by four raters using a conventional method, involving ensemble averaging after careful editing of beat-to-beat waveforms, and a streamlined method, involving ensemble averaging without beat-to-beat editing. Intraclass correlations for interrater reliability exceeded .92, whereas intraclass correlations for concurrent validity exceeded .97, indicating excellent agreement between raters and scoring methods for all cardiac measures. The streamlined method was significantly faster than the conventional method. The results indicate that variations in beat-to-beat editing do not constitute a serious source of error in the ensemble-averaged impedance cardiogram and support the interrater reliability and concurrent validity of the two scoring methods.