Anxiety could be the major culprit in postvaccination presyncope

Drinking water before a blood draw may help keep a patient upright afterward, but does little to prevent feelings of dizziness after vaccination, according to a new study.

“Many adolescents and young adults have presyncope, or feelings that they might pass out, after vaccination,” says Alex R. Kemper, MD, MPH, chief of the Division of Ambulatory Pediatrics at Nationwide Children’s Hospital, Columbus, Ohio, professor of Pediatrics at The Ohio State University, Columbus, member of the US Preventive Services Task Force, and lead author of the study.

“Fortunately, syncope, or actually passing out, after vaccination, is rare,” says Kemper. “We tested whether having teenagers and young adults drink water would decrease the likelihood of presyncope. We decided to do this because studies of people donating blood have shown that this can work.”

Instead, Kemper says the research team found that feelings of anxiety before vaccination are more likely to result in presyncope.

The National Academy of Medicine has suggested that a vasovagal reaction and activation of the sympathetic nervous system may be to blame for syncope related to vaccination, which occurs in about 1 in every 1000 vaccinations given, according to the report. Syncopal episodes usually occur within 15 minutes of vaccination, and the Advisory Committee on Immunization Practices recommends that patients be seated or lying down during vaccination as a precaution, although there are no evidence-based recommendations for preventing postvaccination presyncope.

The study, published in Pediatrics, was aimed at determining whether drinking water prior to vaccination could help, much as drinking water before phlebotomy aids in relieving presyncope by increasing peripheral vascular tone.

Researchers studied individuals aged 11 to 21 years who were asked to drink 500 mL of water 10 to 60 minutes prior to vaccination. Symptoms were then assessed with a 12-item survey for a 20-minute period after vaccination. A total of 906 participants were placed in a control group and 901 in the intervention group. No persons in either group experienced syncope, but 32.6% experienced presyncope. However, there were no significant differences in episodes of presyncope between the control and intervention groups, according to the study.

With further analysis, the research team found that presyncope was most common in individuals of younger age, in those with a history of passing out after a shot or blood draw, in individuals with prevaccination anxiety, in those that received more than 1 injection at a time, and in those with greater postvaccination pain.

The study also reviewed positioning during vaccination, with 92.4% of participants sitting down, 0.9% lying down, 6.2% standing, and 0.5% walking, but found no significant difference in episodes of presyncope among these groups.

The study authors suggest that future research could focus on interventions to reduce anxiety prior to vaccination or to address pain after vaccination to see whether these methods have an impact on presyncopal events.

“Pediatricians and other healthcare providers should be aware that presyncope is common and should be prepared to monitor their patients after vaccination for presyncope or syncope,” Kemper says. “Future studies are needed to see if interventions to address anxiety might decrease the risk of presyncope or syncope.”