Regional ventilation and perfusion were studied in 10 anesthetized paralyzed supine patients by single-photon emission computerized tomography. Atelectasis was estimated from two transaxial computerized tomography scans. The ventilation-perfusion (V/Q) distribution was also evaluated by multiple inert gas elimination. While the patients were awake, inert gas V/Q ration was normal, and shunt did not exceed 1% in any patient. Computerized tomography showed no atelectasis. During anesthesia, shunt ranged from 0.4 to 12.2. Nine patients displayed atelectasis (0.6-7.2% of the intrathoracic area), and shunt correlated with the atelectasis (r = 0.91, P < 0.001). Shunt was located in dependent lung regions corresponding to the atelectatic area. There was considerable V/Q mismatch, with ventilation mainly of ventral lung regions and perfusion of dorsal regions. Little perfusion was seen in the most ventral parts (zone 1) of caudal (diaphragmatic) lung regions. In summary, shunt during anesthesia is due to atelectasis in dependent lung regions. The V/Q distributions differ from those shown earlier in awake subjects.

SUMMARYBackground: Rectal administration of enemas, foams and suppositories is the most efficient way to deliver locally acting drugs to the distal colon. Ropivacaine, a long-acting local anaesthetic, was chosen as a candidate for a new rectal treatment of ulcerative colitis. Aim: To determine the colonic spread of a rectal ropivacaine formulation. Methods: In this randomized, incomplete cross-over study, 12 male volunteers were given 200 mg ropivacaine HCl rectally in 20, 40, 60 and 80 mL hydroxypropyl methylcellulose gel. The viscosity of the gel was 1.1 Pa s. The spread of the radiolabelled ( 99m Tc-labelled diethylenetriaminepenta-acetic acid) formulations was