Anesthesia and Atelectasis

Abstract

The effects of pentobarbital, halothane and methoxyflurane anesthesia on FRC, lung compliance and A-aDO= were determined in dogs during unassisted spontaneous respiration. Similar measurements were made in patients free of cardiopulmonary disease, immediately before extremity surgery, during surgery under halothane anesthesia, and again postoperatively. No significant change in FRC, lung compliance or A-aDOa occurred throughout the anesthetic experience in the dog or in man. We conclude that progressive atelectasis is not a predictable consequence of unassisted respiration during anesthesia in the healthy dog and hi man.

LOCAL ANESTHETICS The effects of four local anesthetics, procaine, lidocaine, tetracaine and dibucaine, on the soleus neuromuscular preparation of the cat in vivo were studied. All anesthetic agents, when injected intra-arterially or intravenously, depressed the posttetanic potentiation of the soleus muscle and abolished the neural repetitive afterdiseharge of the motor nerve terminals. Lidocaine was 1.5, tetracaine 10, and dibucaine 15 times more potent than procaine in depressing posttetanic potentiation. Recovery of posttetanic potentiation was rapid following procaine and lidocaine, but it was prolonged after tetracaine and dibucaine. Since posttetanic potentiation and posttetanic repetitive activity are neural events and local anesthetics depressed them without depressing the transmission of single twitches, it was concluded that local anesthetics act by selective depression of the motor nerve terminal. The possibility of a postjunctional effect of local anesthetics is considered, but, according to the dose-response relationship, it occurs only after injection of large doses. {usubiaga, J. E.., and Standaert, F.z The Effects of Local Anesthetics on Motor Nerve Terminals, }. Pharmacol Exper. Therap. 159: 353 (Feb.) 1968.)