S1131 Ketamine Abortive Therapy Is Associated With Reduced Opiate Use in the ED Management of Cyclic Vomiting Syndrome

Introduction: Cyclic vomiting syndrome (CVS) is defined by episodic bouts of repetitive vomiting, but many CVS patients also experience abdominal pain during attacks. The emergency department (ED) management of severe CVS-associated pain remains to be clearly defined, and often involves opiate administration. Ketamine, an N-methyl-D-aspartate receptor antagonist, has both analgesic and anti-emetic properties, but its potential in ED-based CVS management of pain remains unclear. Methods: We conducted a retrospective cohort study of 22 CVS patients who visited our center’s ED between 2005-2017 and who received at least 1 ketamine dose during 1 of their ED presentations. We recorded outcomes including opiate administration and dosing (oral morphine equivalents), ketamine administration and dose, hospital admission rate and associated length of inpatient stay. Mixed-effects models were used to account for within-patient clustering. Results: The study population [n = 22 patients; 13 (59%) female, median (IQR) age 36 (29-43 years)] made 331 CVS-associated ED visits (median 11 visits per patient). Ketamine was administered during 153 (46%) of these ED encounters. ED visits with ketamine administration had a reduced proportion of opiate use (23 of 153 visits; 15%) compared to visits without ketamine use (133 of 178; 75%). Ketamine use was associated with an overall reduction in oral morphine equivalents of -14.8 mg (95% CI: -18.9 to -10.7), and among those who received ketamine, each 1 mg increase in ketamine dose was associated with a further -0.5 mg reduction in oral morphine equivalents (95% CI: -0.15 to -0.004). ED visits with ketamine administration had a slightly higher (37%) admission rate than those without ketamine administration (20%), with an increased adjusted odds of hospital admission (OR: 2.9; 95% CI: 1.7 to 5.4). Ketamine administration was associated with a non-significant reduction in length of stay of -12.9 hours (95% CI: -47.5 to 21.2). Conclusion: Ketamine appears to be an effective alternative to opiate administration in the ED management of patients presenting with CVS attacks associated with abdominal pain. Although the odds of hospital admission were higher with ketamine-associated ED visits in our cohort, this may reflect a bias to consider ketamine in those presenting with more severe or more refractory symptoms. Overall, these findings support ketamine’s potential role in the ED management of CVS.