Abstract ID: A20

Abstract Title: The effect of adding low dose ketamine to standard practice analgesia after major spine surgery in patients with chronic therapeutic opioid intake

Poster Type: Either


ABSTRACT BODY

Introduction
Patients undergoing major spine surgery for chronic back pain frequently take narcotics preoperatively. Postoperative pain management is often challenging in these patients. They have some degree of opioid tolerance mediated by NMDA receptors (1). We hypothesized that ketamine, a NMDA receptor antagonist will be useful to improve analgesia provided by narcotics.
Methods
After institutional approval and obtaining informed consent, we prospectively studied 40 ASA I-III adults undergoing lumbar laminectomy, fusion and instrumentation in a randomized double-blinded and placebo controlled clinical trial. Patients with preoperative back pain and opioid therapy were divided into two groups, Group1 received IV ketamine 0.15 mg/kg before incision followed by 2 mcg/kg/min for 24 hours, Group 2 received saline placebo. All patients had epidural catheters inserted by the surgeon at the end of surgery and bupivacaine 0.1% infusion was titrated between 6-12 cc/hour. In addition, they used hydromorphone by IVPCA. Intraoperative fentanyl, time to first request of analgesia, IVPCA hydromorphone consumption and visual analog scores for 48 hours (at rest, movement and physical therapy), time to mobilization, length of hospital stay, acute pain service interventions (PO opioids, epidural boluses, neurontin, and muscle relaxants) and patient satisfaction were followed up by a blinded observer. Central nervous system (CNS) side effects (confusion, agitation, hallucinations, headache, giddiness, light headedness, strange feeling and bad dreams), nausea, vomiting, pruritus, constipation, fever, respiratory/ cardiovascular compromise, seizures, twitches and motor weakness were also noted by the blinded observer. Statistical analysis was done using t-test, rank-sum test, chi-square test and fisher-exact test (SPSS11.5). P<0.05 was significant.
Results
Three patients (1 in Gp 1/ 2 in Gp 2) were dropped from the study because of protocol violations. Demographics, preoperative pain score, duration of opioid intake, anesthesia and surgery, number of spinal levels operated, intraoperative fentanyl dose, duration of PACU stay, blood loss and length of incision were similar in both groups. No difference in VAS at rest and movement was seen at 0, 1, 2, 4,8,12,18,24,36 and 48 hours after surgery between the two groups. Median VAS at rest and movement were more than 4 and 6 respectively at all time periods. No difference was noted in incremental and cumulative IVPCA use at any of the time periods and other analgesic outcome measures (Table). CNS side effects were reported in 10 (56%) in Gp 2 (three of them described as severe) compared to 7 (37%) in Gp 1 (p=0.33). Two patients in Gp 1 reported severe CNS side effects, one of them developed dissociation. Nausea and vomiting were noted in 8 (44%) patients in Gp 2 compared to 6 (32%) in gp1 (p=0.64). No difference in the incidence of fever, pruritus, constipation, urinary retention, motor weakness was seen between the groups.
Conclusion
IV Ketamine in the dose studied as adjuvant to IVPCA hydromorphone and epidural bupivacaine did not improve analgesia in patients with preoperative opioid intake after major spine surgery though the side effects were not increased.
1. Curr Rev Pain. 2000; 4:203-5.

ATTACHED FILES

A20_VIMAL TABLE.doc





Reg Anesth Pain Med 2004; 29(2):A20