EMS ketamine use on agitated patients on cocaine increases intubation 5.75-fold, study finds

Ketamine is safe and well-tolerated when administered in a controlled environment such as a hospital for procedural sedation, as patients rarely lose their airway or respiratory drive. Although ketamine use is prevalent, evidence on safety and efficacy is limited and risk factors for respiratory arrest and intubation have not been well studied. Furthermore, many patients with excited delirium are intoxicated or are using illicit substances and these co-ingestants may alter the properties of the drug.

Researchers from Florida Atlantic University's Schmidt College of Medicine conducted a study to explore whether patients treated with prehospital ketamine for excited delirium with concomitant substance intoxication have higher rates of subsequent intubation in the emergency department compared to those without confirmed substance usage.

Results of the study, published in the journal Prehospital and Disaster Medicine, showed that among 86 patients given prehospital intramuscular ketamine for excited delirium, those with concomitant cocaine intoxication had a statistically significant 5.75-fold increased rate of subsequent intubation in the emergency department, which were higher in men than women. There were no deaths reported.

Patients testing positive for alcohol, amphetamines, barbiturates, benzodiazepines, ecstasy, marijuana, opiates, and synthetic cathinones, both bath salts and flakka, had similar rates of intubation compared to those negative for these substances. Baseline characteristics including age, ketamine dose, and body mass index were similar between those who did or did not undergo intubation.

"While additional research is needed, it is tempting to speculate about possible mechanisms whereby prehospital ketamine administered intramuscularly for excited delirium with concomitant cocaine intoxication may increase subsequent intubation in the emergency department," said Joshua J. Solano, M.D., first author, an emergency medicine physician, an assistant professor of emergency medicine and integrated medical science, and director of quality improvement and patient safety, FAU Schmidt College of Medicine. "One plausible explanation is that cocaine may deplete excitatory neurotransmitters and lead to an exaggerated respiratory depression requiring intubation."

Over the course of 28 months, all medical records from two large community hospitals were searched for all patients age 18 years or older with intramuscular administration of ketamine for excited delirium and identified illicit and prescription substance co-ingestions.

For the study, trained abstractors collected demographic characteristics, history of present illness, urine drug screens, alcohol levels, and noted additional sedative administrations. Substance intoxication was determined by urine drug screens and alcohol positivity or negativity, as well as physician history of present illness. Patients without toxicological testing or documentation of substance intoxication, or who may have tested positive due to emergency department sedation, were excluded from relevant analyses. Subsequent emergency department intubation was the primary pre-specified outcome.

Study co-authors are Lisa M. Clayton, D.O., an emergency medicine physician, associate professor of integrated medical science and program director of the FAU emergency medicine residency; Daniel J. Parks, M.D., resident physician, FAU emergency medicine; Shayne E. Polley, M.D., an FAU medical school graduate and emergency medicine resident at Christ Emergency Medicine in Oak Lawn, Illinois; Patrick G. Hughes, D.O, an emergency medicine physician, an assistant program director of the FAU emergency medicine residency and an associate professor of integrated medical science; Charles H. Hennekens, M.D., Dr.PH, Sir Richard Doll professor and senior academic advisor; Richard D. Shih, M.D., an emergency medicine physician, professor of integrated medical science, and division director of the FAU emergency medicine residency program; and senior author Scott M. Alter, M.D., M.B.A., an emergency medicine physician, an associate professor of emergency medicine, and associate research director of the FAU emergency medicine residency, all within the Schmidt College of Medicine.