Canadian Journal of Anesthesia, Vol 40, 320-324, Copyright © 1993 by Canadian Anesthesiologists' Society

ARTICLES

Aortocaval compression in the sitting and lateral decubitus positions during extradural catheter placement in the parturient

PJ Andrews, WE Ackerman 3rd and MM Juneja
Department of Anesthesiology, University of Louisville, School of Medicine, Kentucky 40292.

We prospectively studied the incidence of concealed aortocaval compression in parturients at term during identification of the extradural space. Forty ASA I or II parturients, at term and in active labour, who requested extradural analgesia were randomly allocated to one of two groups. Parturients in the first group (n = 22) were positioned in the left lateral decubitus position and those in the second group (n = 18) were in the sitting position. Cardiac output (CO) was recorded at one-minute intervals for five minutes before extradural catheter placement (supine position with a 15 degrees wedge under the right side), and during and thereafter for five minutes (in the supine wedged position), using the BoMED NCCOM3-R7 thoracic electrical bioimpedance (TEB) monitor. The average of five COTEB recordings before positioning the patient were compared with the average of five COTEB measurements during and after extradural space identification. A change of > 25% COTEB was considered beyond machine variability. Upper limb arterial pressure was recorded at one-minute intervals. In the left lateral decubitus position, 17 of 22 patients demonstrated a > 25% reduction in COTEB compared with five of 18 patients in the sitting position (chi 2, P < 0.01). The percentage change in COTEB in the lateral decubitus position (-29.8%, 95% CI -17% to -44%) was greater than the sitting position (-9.8%, 95% CI +36% to -32%) (P < 0.01). A decreased incidence of aortocaval compression during identification of the extradural space was demonstrated in the sitting position when compared with the left lateral decubitus position.