WEDNESDAY, Oct. 19 (HealthDay News) -- Obese children need special attention when they undergo anesthesia, two new studies suggest.

In one study, researchers found that obese children with asthma suffer more complications from anesthesia than normal weight children with asthma. In the other study, researchers found that obese children require less of one type of anesthesia than normal weight kids.

If a child is obese, has asthma or both, parents should expect close monitoring, said researcher Dr. Olubukola Nafiu, an assistant professor of pediatric anesthesiology at the University of Michigan.

"Children who are obese and asthmatic have a twofold increased risk of developing respiratory problems when they are given anesthesia," Nafiu said.

Both studies are scheduled for presentation Monday at the annual meeting of the American Society of Anesthesiologists in Chicago.

To determine if complications were more frequent among obese kids with asthma, Nafiu looked at 1,102 children and teens, aged 6 to 18, after anesthesia and divided them into four groups. One group was obese and had asthma, one group was normal weight with asthma, another was obese without asthma, and the last group was normal weight without asthma.

Those in the obese-asthmatic and obese non-asthmatic groups were more likely to have critical airway problems, such as spasms, than their thinner peers, the study found, but there were no fatal complications among the study patients.

Both obesity and asthma are known to be independent risk factors for respiratory problems during anesthesia, Nafiu said. Both conditions are increasing in U.S. children at an alarming rate, and the researchers wanted to find out if complications are more frequent in pediatric patients who have the two disorders.

Respiratory problems are a leading cause of complications, including death, during pediatric surgery, the authors said.

In a second study, Dr. Olutoyin Olutoye, of Texas Children's Hospital in Houston, found that obese children require smaller doses of the anesthetic propofol than their slimmer peers.

According to Olutoye, doctors have known that obese adults need less propofol than normal weight adults, but whether that applied to obese children was unclear. Since propofol can cause low blood pressure and reduced breathing, it's important not to administer too much, the researchers noted in a news release from the American Society of Anesthesiologists.

The study included 40 obese and 40 normal weight children. The investigators measured each child's response 20 seconds after getting propofol. The normal weight kids needed 50 to 60 percent more of the anesthetic than the obese children.

In obese children, 75 percent of excess body weight is fat tissue, which can alter the distribution of propofol in the body, the researchers explained.

Additional studies involving children are needed to determine how obesity affects other anesthetic medications, Olutoye said.

"These studies confirm the general impression that anesthesiologists already have about obese children," said Dr. Mark Singleton, chair of the American Society of Anesthesiologists' committee on pediatric anesthesia, who was not involved with the study.

The message from the asthma and obesity study is, "Kids with asthma and obesity are at double jeopardy," Singleton said.

However, he pointed out that the anesthesia-dose research only involved the drug propofol, which is injected, and would not apply to other drugs. Most children's anesthesia is induced by inhalation, Singleton noted.

Doctors should obtain children's height and weight to see if they fall within the obese range, Nafiu added. A body mass index (BMI) in the 95th percentile or above is considered obese.

Parents of obese and/or asthmatic children should expect numerous questions from the doctor before their child undergoes surgery that requires anesthesia, and they should expect especially close monitoring, he added.

Because the research was presented at a medical meeting, it should be considered preliminary until published in a peer-reviewed medical journal.

More information

To help prepare your child for anesthesia, visit the Nemours Foundation.