This quality assurance study has shown that, on the whole, nitrous oxide was rated as highly effective by both nurses and children. However, certain adverse effects led to the delivery of nitrous oxide being halted.
Serious adverse effects were defined in this study as adverse effects that led to the delivery of nitrous oxide being halted. These adverse effects were managed by the nurse and doctor present, without it being necessary to summon anaesthesia personnel. As with all forms of sedation, careful monitoring of the use of nitrous oxide is important. We routinely administered oxygen for 3–5 minutes following the procedure to prevent diffusion hypoxia. Falling oxygen saturation during the procedure was observed in one case in our dataset, and in 0.1 % of procedures in the largest safety study conducted (10). In the Norwegian Institute of Public Health's technology assessment, none of the 525 adverse effects observed was considered serious according to standard definitions (8).
Dizziness, anxiety and euphoria were recorded as adverse effects in our study. These adverse effects are to be expected to some degree with sedation of this type. The incidence of nausea/vomiting in our dataset was comparable to that in the studies summarised in a health technology assessment by the Norwegian Institute of Public Health (8), although the incidence was higher in individual studies (14). Both the Norwegian Institute of Public Health's assessment and a review published in 2013 conclude that use of nitrous oxide in children is effective, safe and has few adverse effects (4).
In a safety study of 7 802 procedures on 5 779 children aged 1 month–18 years, adverse effects were reported in 4 % of cases, despite some use of nitrous oxide of a higher concentration (70 %) than in our study (50 %) (10). In our study, the risk of adverse effects increased with the length of the procedure.
The safety of employees who are regularly exposed to nitrous oxide is an important factor to consider when deciding whether nitrous oxide can be used in hospitals (15). Such safety concerns may be one reason why Norwegian hospitals use nitrous oxide to only a limited degree. Because nitrous oxide is released from the mask only upon inspiration, in theory there should be no leakage of nitrous oxide into the room from a securely-fitting mask. In addition, the procedures are short, in most cases less than 15 minutes, and a limited number of procedures are performed per day, often by different nurses. The safety of nitrous oxide for personnel is also supported by the previous health technology assessment (8), which found no evidence for an increased miscarriage rate in midwives/dental nurses. A risk of infertility was seen with high, but not low, levels of exposure, and congenital malformations were no more frequent among children born to exposed personnel.
Our quality assurance study, with a large number of procedures performed over a little more than four years, provides experience relevant to clinical practice. Data were collected prospectively and systematically. This results in better quality data than retrospective review of medical records, because it allows complete data to be obtained and is not dependent on making assumptions and interpreting information in medical records. Prospective recording also allows for subjective assessment of effectiveness.
We did not administer nitrous oxide to children younger than four years. We could therefore ensure that the child understood and was able to cooperate with the procedure and that the gas was administered through a securely-fitting mask. Studies have shown that nitrous oxide is safe for use in infants as young as one month, but the average age in these studies was 4–6 years (9, 10, 16, 17). We used nitrous oxide in children aged 4–17 years, and found that effectiveness varied little with age. The median age in our dataset was also higher than in the aforementioned studies. Nitrous oxide was tried when there was reason to believe that it would work well, thus all of our patients were pre-selected. In our experience, cooperation and acceptance of the mask are greater when the child understands the procedure well, and we have no plans to significantly change the lower age limit in our clinic.
In our study, nitrous oxide was administered and evaluated by well-trained nurses with expertise in monitoring sick children. The nurses' assessments may be influenced to some degree by prior expectations of a beneficial effect. Nevertheless, the children's experiences were highly consistent with the nurses' assessments, and both were mainly positive. One of the effects of nitrous oxide on children may be mild euphoria and indifference, which can affect pain scoring. However, concordance between the nurses' and the children's assessments helps increase confidence in the ratings.
We did not compare different methods of sedation in our study. However, nitrous oxide was compared with other sedation methods and with placebo in the recently published health technology assessment (8), which included a total of 22 randomised studies. Nitrous oxide was deemed to be as effective as other methods of sedation and more effective than placebo; shorter duration of sedation was also highlighted as an advantage of nitrous oxide (8). Nitrous oxide is a good alternative to agents such as midazolam, not least because a rapid onset of action and faster elimination time are advantageous both for children and for busy hospital personnel (2, 18).
Many of the procedures in our study are relatively simple and do not require general anaesthesia. Nevertheless, our results show that a number of surgical and orthopaedic procedures in which general anaesthesia would normally be used, could in fact be performed with nitrous oxide. As nitrous oxide is considered to be effective, there is an argument for using it in combination with effective pain relief for shorter procedures, instead of general anaesthesia. However, nitrous oxide often has an insufficient analgesic effect, and supplementary medication such as local anaesthesia, non-opioid analgesics or opioids may be required. Our usual practice is therefore to offer nitrous oxide as an alternative to midazolam. Effective pain relief during the procedure is important with both types of sedative.