“Should all children now have intravenous inductions? Maybe, and maybe not.”
PREOPERATIVE discussions in pediatric anesthesia often include the anesthesiologist saying: “there are two ways to induce anesthesia in your child: with anesthetic gas through a mask, or giving an anesthetic drug through an intravenous line.” Not infrequently the parent will respond, “which is best?” Do we have the evidence to answer this simple question? In this issue, Ramgolam et al. report findings from a randomized controlled trial comparing intravenous and inhalational induction in children that are deemed to be at risk of developing perioperative respiratory complications.1 At-risk children are defined using data from the authors’ previous work2 and include children having at least two of the following: an upper respiratory tract infection in the previous 2 weeks, more than three episodes of wheezing in the last 12 months, wheezing at exercise, nocturnal dry cough, history of eczema, passive smoking, and two members of the family with atopic symptoms. Perioperative respiratory complications are defined as arterial oxygen desaturation less than 95%, severe coughing, airway obstruction, bronchospasm, laryngospasm, or postoperative stridor. They found that intravenous induction had about half the rate of respiratory complications (10.7% for intravenous vs. 26% for inhalational induction). To some extent it is not surprising that intravenous inductions have fewer complications. They are faster, and the child progresses rapidly through the excitement phases of light anesthesia. There is also no pungent gas to irritate the airway. Ramgolam et al.’s results are consistent with what we would expect from our basic understanding of anesthetic pharmacology. So, should we now respond to parents that intravenous induction is safer? Should all children now have intravenous inductions? Maybe, and maybe not.
Randomized controlled trials provide high-quality evidence, but they are inevitably performed at a population level, in a particular population. How do the results extrapolate to your population and to your patient? First, the study only included those at risk of respiratory complications; they also excluded children needing premedication, and only included children where a laryngeal mask airway was the intended airway device. Inhalational induction also included a bolus of propofol in about half the cases. More importantly, they only included children whom the anesthesiologist deemed suitable for both induction methods, presumably excluding the children that had a needle phobia or no visible veins.
It is also pertinent to note that only one outcome was analyzed—respiratory complications. Clinically, when deciding on intravenous or inhalational induction we inevitably consider a risk–benefit analysis for each child across a range of outcomes. The child may be distressed by the idea of a needle, or indeed, a mask. Ramgolam et al. did not measure distress; however, it is interesting to note that while 15 of the children randomized to receive intravenous induction received an inhalational induction, six children that were randomized to an inhalational induction received an intravenous induction. The reasons for this crossover are not fully described, but this may hint that a child’s preference can go either way.
Respiratory complications were the primary outcome in this trial, but in some cases, the anesthesiologist may consider this outcome of lesser importance; inhalational induction may indeed increase the risk of coughing or breath holding, but these can usually be safely managed and rarely lead to ongoing morbidity. In this trial, a composite outcome was used, which included outcomes that some may regard as trivial (such as transient oxygen desaturation or coughing); however, it is important to note that in a secondary analysis a substantial difference was still seen when outcomes were limited to the more clinically worrisome outcomes of bronchospasm or laryngospasm (2% for intravenous vs. 11% for inhalational induction).
As noted previously, the treating anesthesiologist thought there was equipoise and that either method of induction should be safe and acceptable. A relatively large number of cases were recruited, indicating a flexible approach in their institution. This “open-minded” attitude was fortuitous for conducting such a study. Many anesthesiologists, departments, and perhaps even countries have fairly fixed views on the best induction technique (either one way or the other).
So, what should we do after this study? It does not mean that we should abandon inhalational inductions altogether. There is no doubt that inhalational induction is better in cases where intravenous access is problematic or the child has a needle phobia. This trial provides good quality evidence that “all else being equal,” it is somewhat safer to go with an intravenous induction in children that are at risk of respiratory complications. This trial is a good example of how the relevance of the trial to your patient needs to be considered in terms of the population it was conducted in, and the relative importance of the outcome to your particular patient. When deciding on induction technique, care should be taken to weigh all the relevant factors.
If the veins do not appear too bad, the child seems happy to have an intravenous line (or already has one), and there are risk factors for respiratory complications, then we should probably answer the parent with, “in this case I think an intravenous anesthetic would be best.”
The author is not supported by, nor maintains any financial interest in, any commercial activity that may be associated with the topic of this article.