The role of ketamine in opioid-free spinal deformity surgery: is it possible and beneficial?

Background: As the opioid epidemic in the United States has continued to gain momentum in recent years, the current study aims to explore the efficacy of ketamine in a traditionally challenging setting regarding pain control, and contribute toward developing an opioid-free intraoperative pain protocol in spinal deformity surgery.

Methods: Fifty-four patients who underwent spinal deformity surgery between January 1, 2017 and December 31, 2017 by one senior surgeon were included. Demographic data and preoperative opioid use was collected. Surgical details including number of levels fused, estimated blood loss, and operative time was also collected. All patients received a hydromorphone patient-controlled anesthesia (PCA) device postoperatively. 36/54 patients received perioperative ketamine during their procedure, both intraoperatively and postoperatively. The consumption of postoperative hydromorphone and the ratio of doses given by doses attempted postoperatively were recorded. Patient charts were also reviewed for documented ileus during their inpatient stay.

Results: Mean age was 49 years, and 31% were male. Average BMI was 24.3 kg/m2 . The average number of levels fused was 11.6. Mean operative time was 10.7 hrs, and average EBL was 1,522 mL. The mean length of stay was 8 days. Average postoperative PCA use of hydromorphone in the no ketamine group (NK) (n=18) was 5.99 mg compared to 6.91 mg for those who received perioperative ketamine (K) (n=36); there was no significant difference between populations (P=0.57), although the variances was significant (P=0.044). There was no correlation between intraoperative ketamine and postoperative PCA use (r=-0.05; P=0.72). Additionally, there was no correlation between postoperative PCA use and dose of postoperative ketamine received (r=-0.15; P=0.27). The ratio of doses given: attempted was 0.61 in the NK group and 0.59 in those in the K group (P=0.79). Average postoperative hydromorphone use was 5.48 mg in patients that did not use opioids preoperatively (n=39) compared to 12.77 mg in those who used opioids preoperatively (n=9; P=0.0003). 9/54 patients had a documented ileus during their admission, while 4/9 (11%) had received ketamine (P=0.095).

Conclusions: Though our study showed no significant change in postoperative opioid requirement in our population, our results show that integration of ketamine in these extensive operations fare similarly to traditional opioid-based regimens. There was also no significant association seen between ketamine use and adverse side effects such as ileus. At our institution we are currently establishing opioid-free intraoperative pain protocols that use ketamine as an adjunct, and further study will explore the effect this may have on postoperative opioid consumption for spinal surgery patients as well as postoperative patients in general.