Canadian Journal of Anesthesia, Vol 11, 460-475, Copyright © 1964 by Canadian Anesthesiologists' Society

Arterial-Blood Gas Studies Associated with Anaesthesia for Adenotonsillectomy in Children

¹ Chief Anaesthetist, The Children's Hospital, Winnipeg, and Assistant Professor (Anaesthesia), Department of Surgery, University of Manitoba
² Department of Anaesthesia, The Children's Hospital, Winnipeg, and Lecturer (Anaesthesia), Department of Surgery, University of Manitoba
³ Department of Anaesthesia, The Children's Hospital, Winnipeg

As a base line, the effect of pre-anaesthetic medicatin on the arterial blood gases was compared with normal, unpremedicated controls Meperidine and atropine given together by intramuscular injection, about one hour begore sampline, were found to cause no significant alteration in arterial pO₂, pH, or standard bicarbonate. There was a rise in arterial pCO₂ which was only significant at approximately the 6 per cent level.

The results of arterial blood samples taken during and after adenotonsillectomy, using six different techniques of anaesthesia, have been presented and analysed. When endotracheal intubation was used and respiration was spontaneous, ether resulted in the most normal ventilation Methoxyflurane and halothane, with spontaneous respiration, caused a signigicant elevation of arterial pCO₂ and hypoventilation. It is not suggested that statistical significance and clinical importance necessarily correspond, but the effect of hypercarbia on the amount of bleeding during this difficult operation should be considered.

Controlled respiration with halothane–oxygen, or nitrous oxide–oxygen (75% 25%) and succmylcholme, caused significantly lower arterial pCO₂ levels and higher pH levels. These differences continued in the postoperative period, except that the halothane–oxygen–controlled respiration group tended to have a period of depressed respiration after extubation, probably as a result of clinical miscalculation. This was shown by a marked rise in arterial pCO₂ and the lowest arterial pO₂ level of all the techniques at this time.

Arterial oxygen tensions during anaesthesia varied widely but were all well above 100 mm Hg With 75 per cent nitros oxide and 25 per cent oxygen using manually controlled respiration with succmylcholme, the mean arterial pO₂ was 121 mm Hg (±18), and this technique, properly carried out, was considered safe in children.

Very steep and rapid falls in arterial oxygen tensions occurred in the immediate post-anaesthesia period in all cases in the absence of any obstruction. This is a very dangerous period and oxygen should be given routinely to all patients both at this time and when suctioning is done in the recovery room.

The results with the technique of ether insufflation, because of the smallness of the group, are considered separately. If the technique is clinically well done, the arterial blood gases are apparently quite within normal range However, the lack of control of the airway and the very common finding of blood in the tracheo-bronchial tree post-operatively, when this technique is employed, are thought to make it less desirable than the proper use of endotracheal intubation.

Many of these children are difficult to manage in the recovery room. The patients who had 75 per cent nitrous oxide, 25 per cent oxygen, and controlled respiration with succmylcholine are strikingly easier to manage and generally have less bleeding at this time.

It is quite clear that the anaesthetist must devote all his attention to his proper task during this procedure. The practice of assisting the surgeon as well can only be described as unreasonable and dangerous.

Note:

Presented at the Annual Meeting, Canadian Anaesthetists' Society, Montebello, Quebec, May 11–14, 1964