Canadian Journal of Anesthesia, Vol 2, 41-63, Copyright © 1955 by Canadian Anesthesiologists' Society

Mixed Pentothal–Curare–Nitrous Oxide Anaesthesia for Children and Infants: A Technique and Dosage Scale for Rapid Intubation and for Maintenance

¹ Department of Anaesthesia, Children's Memorial Hospital and McGill University, Montreal, Quebec

Some of the advantages of mixed pentothal-curare (Baird's solution) and nitrous oxide anaesthesia over the other types of general anaesthesia in adults are noted and the need in paediatric anaesthesia for a method with similar advantages was pointed out. The main object of this preliminary investigation was to seek a basic dosage scale of mixed pentothal–curare (ml./lb. body wt.) in children for a specific purpose (rapid injection for orotiacheal intubation) so that this technique of anaesthesia and its advantages might be extended into the paediatric field. A surprisingly constant and accurate scale was found, and so it was possible to modify the well-known rapid injection technique for advantageous use in children and infants.

The indications, contra-indications, and possible complications of this method in children were assumed to be basically similar to those in adults and those found to differ significantly from experience with adults or felt to be of special importance in paediatric anaesthesia are emphasized. The technique itself is, except for the added preliminary induction phase and quantitative modifications, similar to that employed in adults. It is presented in much detail, however, in order that the clinical effects of each step and the management thereof in children may be fully understood and the margins of safety guarded. Postoperative observation and care are similarly emphasized.

The amounts of pentothal–curare required fpr rapid intubation and for maintenance of children and infants and the clinical effects thereof were remarkably uniform. The salient findings are as follows:

1. The optimum mixture for 100 lb. children down to about 20 lb. Infants is that of Baird's solution (25 mgm. pentothal with 5 units curare per ml. of solution). Since the duration of the effects of pentothal increases and those of curare remain about the same in progressively younger infants, a mixture with, a smaller proportion of pentothal (15 or 20 mgm./ml.) would likely be more suitable for them.

2. The tolerance of all of the children and infants to a rapidly injected dose of the pentothal–curare sufficient for intubation was excellent and probably equivalent to that of adults. The tolerance displayed to subsequent total maintenance dosage by 20 to 100 lb patients appeared to be about one-half that of adults, and by infants under 20 lb. It was probably about one-quarter that of adults.

3. The dose of rapidly injected pentothal–curare needed for intubation was very closely related to body weight and could therefore be predicted with safety and much greater accuracy than in adults. The amount used for maintenance seemed at least as closely related to body weight as in adults.

4. The optimum rapid intubation dose of millilitres of pentothal–curare mixture (1) for children and infants is lb. wt/6, ±1/10 for variables. The optimum intermittent maintenance dose is about 1/10 to the intubating dose given every

15 to 30 minutes. The maximum tolerated total maintenance dosage in children seems to be equal to the intubation dose and in infants it is only one-half of the intubating dose.

5. The degree and duration of pentothal–curare anaesthesia and relaxation in children are comparable to those observed in adults.

6. The amount of pentothal–curare needed for maintenance can be greatly reduced by a disproportionately small amount (trace) of ether or trichlorethylene. This was found to be particularly useful near the end of operations in the interests of rapid emergence and in halving the total maintenance dosage of pentothalcurare in lengthy procedures.

Throughout this investigation all of the well-known advantages seen in adults from rapid intubation and maintenance with pentothal–curare–nitrous oxide were obtained. The disadvantages and possible dangers in children are easily circumvented by knowledgeable and careful selection and management.

Note:

Presented before the Annual Meeting of the Canadian Anaesthetists' Society, Vancouver, British Columbia, June 14–15, 1954.