BACKGROUND: Ketamine acts predominantly by antagonizing the N-methyl-D-aspartate receptor, has a chiral structure and is metabolize by the cytochrome P450 (CYP) 3A and CYP2B6 enzymes. The most common administration routes are intravenous and intramuscular, although it can be administered subcutaneously and oral; but due to extensive first-pass metabolism it has a low bioavailability. 

CASE REPORT: We present a 73 y.o. male ASA II patient scheduled for colonoscopy due to mild hematochezia. The patient had hypertension and benign prostate hypertrophy. Sedation with spontaneous ventilation was performed with standard monitoring, EKG, pulse-oxymetry and blood pressure. The patient first received an intravenous bolus of Ketamine 15mg and Propofol 50mg, followed by an infusion at 150mg/h.
During the procedure a 12mm polyp was identified in the ascending colon and for it´s extraction it was first elevated with diluted methylene blue injected in the mucosa. The procedure went without incidents and the patient would have been ready for discharge with a Modified Aldrete Score of 10/10 20 min after the procedure. However, when performing the next procedure on the list, we discovered that the methylene blue had been diluted in a labelled bag containing ketamine diluted in saline, and thus the patient received 100mg of it in the colonic mucosa. We explained him the incident and he was kept under observation at the post-anaesthesia recovery unit for 12h. During this period the patient was asymptomatic and was later discharged home.  

DISCUSSION: Safety is a team effort and commitment, however, even with correctly labelled medication errors can occur; and it is important to come forward to the patients about it. This is the first case report of ketamine administration in the gastrointestinal mucosa; and through this administration error we can learn about it. The patient didn´t develop any symptoms of ketamine administration which could indicate that it was not absorbed, or at least not fully, by the gastrointestinal mucosa. 

REFERENCES: Peltoniemi MA et al. Clin Pharmacokinet 2016.

LEARNING POINTS: Ketamine appears not to be absorbed by the gastrointestinal mucosa. More studies are necessary to fully understand the pharmacokinetics and pharmacodynamics of this drug. It´s vital to labelled all the medication, and also check all the empty syringes and ampules at the end of every procedure.

Accidental administration of ketamine in the gastrointestinal mucosa