Intubation using inhaled anesthetics without muscle relaxants (IAWMR) is a well accepted technique when used for the management of difficult pediatric airways . Its frequency of use for routine tracheal intubation of healthy pediatric patients is unknown, and there are no data regarding its safety. One purpose of this study was to determine the frequency of routine practice of IAWMR among anesthesiologists who have a special interest in pediatric anesthesia and who practice anesthesia in the United States. We also sought to determine reasons for using this technique.
We randomly chose a subset (33%) of Society for Pediatric Anesthesia (SPA) anesthesiologists practicing in the United States to receive the survey. Initial surveys were sent by mail in February 1997, with a second mailing 2 mo later for those anesthesiologists who did not response to the first mailing. Survey responders' anonymity was maintained by numerical coding of envelopes, with separation of surveys and envelopes at the time they were received. Survey responders received no reimbursement for responses. Survey questions inquired about the respondent's background and about preferences and attitudes regarding use of IAWMR for tracheal intubation of healthy infants (0-12 mo) and children (12 mo-7 yr). The complete survey form is shown in (Appendix 1 Table 4). A healthy patient was defined as one who was ASA physical status I or II, and who had a normal airway. The definition also specified that the patient was adequately fasted, had no history of gastroesophageal reflux, and was undergoing nonemergent surgery. Associations between survey covariates and preference for tracheal intubation with IAWMR were analyzed by using odds ratios, using chi squared analysis and Fisher's exact test, when appropriate, to calculate P values. In addition, stepwise multiple logistic regressions (MLR) were performed to find the most efficient multivariate models describing the associations between preference for intubation with IAWMR and survey covariates. Data are reported as percentage +/- SE or as odds ratios (95% confidence limits).
Of the 423 surveys mailed, 299 were returned, for a response rate of 71%. Practices were classified as academic by 53.4% +/- 2.9% of responders. At least 6 mo of postgraduate fellowship training in pediatric anesthesia had been completed by 65.4% +/- 2.8% of responders. Sevoflurane was available to 87.3% +/- 2.0% of survey responders at the time they were surveyed. Of all responders, 27% +/- 2.6% stated they had increased their use of IAWMR as a result of the availability of sevoflurane. For induction of healthy infants and children, survey responders listed the percentage that they induced by the inhaled route, yielding mean percentages of 91.2% +/- 1.0% and 86.7% +/- 1.1%, respectively. The technique of intubation with IAWMR had been learned by 98.0% +/- 0.9% of all responders, with 67.7% +/- 2.7% having first learned it during residency, 14.8% +/- 2.1% during fellowship, and 15.5% +/- 2.2% after the completion of their training. The percentage of responders who had learned the technique as a resident did not vary with the number of years since completion of their residency training. Only 5.0% +/- 1.29% were taught tracheal intubation with IAWMR as a technique to be used solely for the management of a difficult airway. Of all responders who listed their most often used technique for tracheal intubation of healthy infants and children (94%), intubation with IAWMR was most often used by 38.1% +/- 2.9% and 43.6% +/- 2.97%, respectively. Of those anesthesiologists who classified their practice as nonacademic, IAWMR was listed as the most often used technique by 54.6% +/- 4.3% and 59.2% +/- 4.3% for infants and children, respectively. Of all responders who most often used intubation with IAWMR, 72.0% +/- 4.4% and 77.7% +/- 3.8% preferred to place an IV before intubation of infants and children, respectively. A summary of responder preferences is given in Table 1.
Univariate analysis of practitioner covariates found several associations with preference for IAWMR (Table 2). Our best stepwise logistic regression model found only the associations of covariates that were both strongly associated with preference for IAWMR and that maintained association after controlling for potential confounders. In the MLR model, anesthesiologists who most often used intubation with IAWMR for healthy infants had more than twice the odds (odds ratio [OR] 2.30, 95% confidence interval [CI] 1.18-4.50; P = 0.015) of classifying their own practice as nonacademic, and nearly one-third the odds (OR 0.34, 95% CI 0.17-0.68; P = 0.002) of having >50% of their cases involve supervision of nurses or residents. Associations for anesthesiologists who preferred IAWMR for tracheal intubation of healthy children were similar to those for healthy infants.
Anesthesiologists who use IAWMR for tracheal intubation of healthy infants most commonly selected as their reasons the lack of need for a muscle relaxant during intubation or during the remainder of the case (81.5%) and the desire to avoid both succinylcholine and the excessive duration of nondepolarizing muscle relaxants (57.8%). Reasons for using IAWMR for infants and children are given in Table 3. Only 12.5% +/- 2.0% and 10.5% +/- 1.9% of all survey responders stated that they never use IAWMR for tracheal intubation of healthy infants and children, respectively. MLR modeling found those anesthesiologists who never use IAWMR for healthy infants to have twice the odds of having >10 yr since completion of their residency training (OR 2.14, 95% CI 1.01-4.7).
Tracheal intubation of the difficult pediatric airway using an inhaled anesthetic and no muscle relaxant has been recommended in pediatric anesthesia textbooks [1-3]. There is no discussion of how to perform this technique, and mention of its use for tracheal intubation of healthy patients is nonexistent. There are no published data regarding the frequency of use or the safety of tracheal intubation with IAWMR. Personal communications with colleagues led us to believe that IAWMR is often used for tracheal intubation of healthy pediatric patients. Our data indicate that, within the SPA, for healthy pediatric patients, tracheal intubation with IAWMR is the technique most often used (by more than one third of anesthesiologists) and is the majority practice among those who classify their practice as nonacademic.
Those anesthesiologists who never use IAWMR for infants were twice as likely to have been practicing anesthesia for >10 y from the time of completion of their training. This could represent a difference in teaching during the era in which they trained, but that seems unlikely, because we could not find a relationship between those who learned IAWMR as a resident and the number of years since completion of training.
In our study, the most commonly stated reason for using IAWMR was the lack of need for a muscle relaxant during intubation or maintenance of anesthesia. Avoiding the use of a muscle relaxant for an entire case saves the cost of the relaxant and reversal drug. Avoiding reversal drug may also decrease nausea and vomiting . Tracheal intubation facilitated by succinylcholine or mivacurium does not require reversal, but issues of safety and prolonged block have been raised for both drugs [5,6]. Reliability of blockade is also an issue with mivacurium . As detailed in Table 3, difficulty with pediatric venous access, due to either technical challenge or lack of an assistant able to place an IV, is a reason survey responders use IAWMR. In our MLR model, anesthesiologists who most often used IAWMR had three times the odds of working most cases alone. When percent supervision was left as a continuous variable, the statistical significance was even greater (P = 0.028 vs P = 0.043). We think that this strong association may be due to the lack of an assistant to start an IV line.
The methodology of this study deserves comments. Survey studies have limitations, of which responder selection bias is notable. There is the potential for responders with a particular practice bias to have a higher response rate to a survey. Obtaining a high survey response rate decreases the likelihood of this type of bias. We obtained a 71% response by choosing a population interested in the survey questions and by creating a survey form consisting of only one page of carefully constructed questions (Appendix 1 Table 4). Taken to the extreme, even if all 29% of the nonresponders preferred to use a muscle relaxant for tracheal intubation of healthy pediatric patients, the percentage of anesthesiologists who prefer IAWMR for infants and children would be 25.3 +/- 2.1% and 28.6% +/- 2.2%, respectively. We believe that those percentages would still indicate frequent use of this technique. Survey studies may also be limited due to lack of truthfulness of responses, but maintaining the anonymity of responders should have decreased that problem. Regarding the association of covariates with preference for IAWMR, our univariate analysis found strong associations with many covariates. The limited number of covariates that maintained significance in our MLR model could be related either to a true lack of association or to a loss of power in the MLR analysis of those covariates. We acknowledge the inability to extrapolate our findings to anesthesiologists outside our study population. However, we have no reason to believe that the practice of tracheal intubation with IAWMR is less widespread among non-SPA anesthesiologists in the United States.
In conclusion, our survey of SPA anesthesiologists demonstrates considerable use of IAWMR for tracheal intubation of healthy pediatric patients, especially among nonacademic anesthesiologists. As long as tracheal intubation with IAWMR remains prevalent, training programs should promote education of the technique so that trainees have the opportunity to acquire this skill in a supervised environment. A prospective trial comparing the safety of IAWMR with that of tracheal intubation with muscle relaxants may be warranted.
This work was performed in loving memory of Nicholas Theodore Politis. The authors give special thanks to Peggy Rachels for her relentless efforts and to Wilson Somerville for his editorial expertise.
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