Hemodynamic perturbations during robot-assisted laparoscopic radical prostatectomy in 45° Trendelenburg position.

BACKGROUND: Robot-assisted laparoscopic radical prostatectomy has gained widespread use. However, circulatory effects in patients subjected to an extreme Trendelenburg position (45°) are not well characterized. METHODS: We studied 16 patients (ASA physical status I-II) with a mean age of 59 years scheduled for robot-assisted laparoscopic radical prostatectomy (45° head-down tilt, with an intraabdominal pressure of 11-12 mm Hg). Hemodynamics, echocardiography, gas exchange, and ventilation-perfusion distribution were investigated before and during pneumoperitoneum, in the Trendelenburg position and, in 8 of the patients, also after the conclusion of surgery. RESULTS: In the 45° Trendelenburg position, central venous pressure increased almost 3-fold compared with the initial value, with an associated 2-fold increase in mean pulmonary artery pressure and pulmonary capillary wedge pressure (P<0.01). Mean arterial blood pressure increased by 35%. Heart rate, stroke volume, cardiac output, and mixed venous oxygen saturation were unaffected during surgery, as were echocardiographic heart dimensions. After induction of anesthesia, isovolumic relaxation time was prolonged, with no further change during the study. Deceleration time was normal and stable. In the horizontal position after pneumoperitoneum exsufflation, filling pressures and mean arterial blood pressure returned to baseline levels. Pneumoperitoneum reduced lung compliance by 40% (P<0.01). Addition of the Trendelenburg position caused a further decrease (P<0.05). Arterial blood acid-base balance was normal. End-tidal carbon dioxide tension increased whereas arterial carbon dioxide was unaffected with unchanged ventilation settings. Pneumoperitoneum increased PaO2 (P<0.05). Ventilation-perfusion distribution, shunt, and dead space were unaltered during the study. CONCLUSIONS: Pneumoperitoneum and 45° Trendelenburg position caused 2- to 3-fold increases in filling pressures, without effects on cardiac performance. Filling pressures were normalized immediately after surgery. Lung compliance was halved. Gas exchange was unaffected. No perioperative cardiovascular complications occurred.

Ventilation-perfusion relationships in pulmonary arterial hypertension: effect of intravenous and inhaled prostacyclin treatment.

UNLABELLED: In seven patients with idiopathic or secondary pulmonary arterial hypertension (PAH), ventilation-perfusion (V (A)/Q ) relationships were measured during a right heart catheterization using the multiple inert-gas elimination technique before and during intravenous infusion with epoprostenol (EPO), and following 5 months of 20 microg inhaled iloprost taken three times daily (ILO). Pre-treatment pulmonary vascular resistance (PVR) was 9.3+/-5.0 mmHg/l/min and the dispersion of perfusion and ventilation for V (A)/Q -ratios was increased. EPO reduced PVR by 20%, and increased cardiac output, shunt, and mixed venous oxygenation (SV(O2)). The arterial oxygen tension (Pa(O2)) remained unchanged. Basal central haemodynamics did not change after 5 months of ILO. Fifteen minutes after ILO, PVR decreased by 20%, and the shunt, SV(O2), and Pa(O2) remained unaltered. CONCLUSIONS: In secondary PAH with normal lung volumes, significant V (A)/Q mismatching occurred. The PVR was reduced to a similar degree during EPO and after ILO, but only EPO increased the shunt and SV(O2). EPO and ILO did not significantly affect the Pa(O2).

Tidal volume forced expiration in asthmatic infants: reproducibility and reversibility tests.

BACKGROUND: The tidal volume forced expiration technique used in infants is considered as the first practical noninvasive method of assessing airway physiology in infants. However, its role has been discussed mainly due to the high variability of the derived parameters. OBJECTIVES: The aim of the study was to assess the reproducibility of a complete measurement with the tidal volume forced expiration technique in infants as measured by the maximal flow at FRC (V(max)FRC). A second aim was to evaluate the bronchial reversibility test in infant asthma. METHODS: Thirty infants with asthma were investigated with the tidal volume forced expiration technique twice with 10 min in between and a third time 10 min after inhalation of terbutalin 0.5 mg. RESULTS: The mean V(max)FRC in the first investigation was 285 ml.s(-1) (coefficient of variation 57%), unchanged in the second investigation and significantly lower than the mean predicted value of 404 ml.s(-1). The relative difference between the 2 investigations of V(max)FRC was mean 10.5% (SD 8.4) of the absolute V(max)FRC value and independent of the size of this V(max)FRC value. The 95% confidence interval for individual changes would then be up to 27% (mean + 2 SD). The infants with the lowest V(max)FRC percent predicted decreased further in V(max)FRC after inhalation of the bronchodilator (p < 0.05). CONCLUSIONS: The tidal volume forced expiration technique was able to measure flow at late expiration with the same reproducibility as seen with spirometry in adults, even if the flow was low. We found the technique acceptable for clinical practice and research, but the results from reversibility tests are difficult to interpret. A significant change of V(max)FRC would, however, be 27% or more.