Canadian Journal of Anesthesia, Vol 11, 159-167, Copyright © 1964 by Canadian Anesthesiologists' Society

Duration of Anaesthesia with Thiopental When Combined with Each of Mannitol, Urea, Sodium Bicarbonate, or Tromethamine ("THAM," "Tris")

¹ Department of Anesthesiology, State University of New York, Upstate Medical Center, Syracuse, New York

Crossover experiments were earned out ten medium-sized mongrel dogs using intravenous injections of a therapeutic dose of mannitol, urea, sodium bicarbonate, and tromethamine (THAM), to determine1 whether any of these would alter significantly the duraation of thiopental "sleep" induced with a single intravenous dose of 25 mg /kg body weight.

Mannitol, in a dose of 1 gm /kg given over 15 minutes, prolonged recovery time by approximately 25 per cent, whereas sodium bicarbonate, in a dose of 75 mg /kg given within 30 seconds shortened recovery by about 25 per cent Urea (1 gm /kg in 15 minutes) and tromethamme (300 mg /kg in 15 minutes) had no appreciable effect on recovery time although, with urea, there was a trend to delayed recovery, whereas with tromethamine, the trend was towards more rapid recovery. Urea and tromethamine caused retching and/or vomiting during administration in some of the animals, and tromeihamine caused apnoea and death in one.

The biochemical effect of these drugs and the obscure mechanism of action on pulmonary ventilation were reviewed briefly along with their clinical applications. The prior unpredictability of their interaction with thiopental was evident from the results, and points to the importance of carrying out such studies before employing drug combinations clinically, particularly during the course of anlaesthesia. Serious complications arising from the combuiation of therapeutic agents with anaesthetic drugs can only be prevented or managed effectively when one is aware of the specific responses that drug combinations can cause.