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Children with a dry cough at night or wheezing during exercise are at elevated risk of respiratory adverse events during and after general anesthesia, researchers reported.

Those were two of the findings of a prospective cohort study aimed at finding risk factors for perioperative respiratory adverse events in children, according to Britta von Ungern-Sternberg, PhD, of the Princess Margaret Hospital for Children in Subiaco, Australia, and colleagues.

The complete list could form the basis of a pre-anesthetic assessment that might reduce the incidence of such events, the researchers argued in the Sept. 4 issue of The Lancet.

The researchers collected data, using questionnaires, on all children who had general anesthesia for surgical or medical interventions at Princess Margaret Hospital for Children from Feb. 1, 2007, to Jan. 31, 2008. All told, 9,297 questionnaires were available for analysis, they reported.

Over the study period, they reported, 1,392 (or 15%) of the children had perioperative respiratory adverse events, including 193 with bronchospasm, 351 with laryngospasm, 332 with airway obstruction, 919 with oxygen desaturation, 687 with coughing, and 58 with stridor.

Urgent procedures, the researchers reported, were riskier than elective procedures, at 17% versus 14%, leading to a relative risk of 1.2 with a 95% confidence interval from 1.1 to 1.3, which was significant at P=0.001.

The researchers found that a positive respiratory history -- defined as a nocturnal dry cough, wheezing during exercise, wheezing more than three times in the past 12 months, or a history of present or past eczema -- was associated with an increased risk of adverse events. Specifically, such a history:

• Increased the risk of bronchospasm more than eight-fold. The relative risk was 8.46, with a 95% confidence interval from 6.18 to 11.59, which was significant at P<0.0001.
• Increased the risk of laryngospasm fourfold. The relative risk was 4.13, with a 95% confidence interval from 3.37 to 5.08, which was significant at P<0.0001.
• Increased the risk of perioperative cough, desaturation, or airway obstruction threefold. The relative risk was 3.05, with a 95% confidence interval from 2.76 to 3.37, which was significant at P<0.0001.

As well, they reported, upper respiratory tract infection was associated with an increased risk, but only when symptoms were present or when the infection occurred less than two weeks before the procedure.

If at least two family members had asthma or atopy, or smoked, that also increased the risk significantly (at P<0.0001 for all).

The risk was lower with intravenous induction of anesthesia compared with inhalational induction, with inhalational compared with intravenous maintenance of anesthesia, with airway management by a specialist pediatric anesthetist compared with a resident, and with the use of a face mask compared with tracheal intubation. All differences were significant at P<0.0001.

The findings generally accord with previous studies, but raise several questions, according to Jerrold Lerman, MD, of Women and Children's Hospital of Buffalo, in Buffalo, N.Y.

For instance, Lerman said in an accompanying commentary, it's not clear whether the practice described in the study is consistent with current practice in large urban pediatric centers, where surgery for children with some of the risk factors -- high temperature and green runny nose -- is usually cancelled, while it was not in the study.

"Unsurprisingly, these children developed perioperative respiratory adverse events," he wrote.

Because the study took place in a single institution, its external validity might be challenged, Lerman argued, but nevertheless it "adds an interesting perspective" on the understanding of perioperative respiratory adverse events.