Haemodynamic changes during anaesthesia in knee-elbow position

To evaluate hemodynamic alterations during surgical procedures performed in the knee-elbow position.

prospective evaluation of the aortic blood flow (ABF) and other cardiovascular variables measured with a transesophageal Doppler (TED) in 2 groups of patients free of previous cardiovascular diseases undergoing lumbar discectomy.

Operating theatre of a neurosurgical department. Beside TED, the standard monitoring included continuous ECG surveillance, capnometry, noninvasive measurement of blood pressure and pulsoxymetry.

Overall, 24 ASA 1 patients have been enrolled. In 12 patients (Group A) the intervention was performed without dobutamine. In the other 12 patients (Group B) dobutamine (2.5-3 micrograms/kg/min) was started from the beginning of the intervention; the two groups did not differ in terms of age, body size, duration of surgery or anesthetic technique used; hemodynamic measurements were obtained at the beginning of the intervention (T1), with the patients still supine, during the intervention in the knee-elbow position (T2) and finally at the end of the procedure (T3) being the patients still anesthetized but lying supine again.

In both groups the ABF; the systolic volume and the ETCO2 significantly decreased in the knee-elbow position; concomitantly, peripheral vascular resistances increased. In Group B, the hemodynamic variables were significantly better than in the other group.

In the patients enrolled, the perioperative administration of low-dose dobutamine was associated with better cardiovascular performance.