Epidural ketamine reduces post-operative epidural PCA consumption of fentanyl/bupivacaine.

PURPOSE: To study the analgesic effect of epidural ketamine on postoperative pain and epidural PCA consumption after total abdominal hysterectomy.

METHODS: Sixty-one ASA I-II patients, 34-60 yr were randomly assigned into three groups. Epidural catheters were inserted before induction of anaesthesia. Patients in group I and II received 30 mg ketamine epidurally before induction of anaesthesia or 20 min after skin incision: group III received placebo. Postoperatively, on first analgesia request, sedation score, Visual Analogue Scale (VAS), Prince Henry Score (PHS) and Bromage motor weakness score were taken and followed by an epidural bolus of 9 ml bupivacaine 0.25% + 50 micrograms fentanyl. Analgesia was maintained by PCA with a mixture of bupivacaine 0.1% + fentanyl 0.001% epidurally. Measurements were repeated at 1, 2, 4, 8, 12 and 24 hr.

RESULTS: First analgesia request was 17 +/- 6.8 min in the control group compared with 31.4 +/- 23.8 and 44 +/- 23.1 min for groups I and II respectively. The differences between group III and group I (P < 0.05) and between group III and group II (P < 0.01) were statistically significant. Twenty four hour PCA consumption was 101.2 +/- 47.2, 87 +/- 27 and 162 +/- 38 ml for groups I, II and III respectively. The differences between group III and group I and that between group III and group II were statistically significant (P < 0.001).

CONCLUSION: Epidural ketamine 30 mg reduces post hysterectomy pain as evidenced by prolongation of time to first analgesia request and reduction in postoperative epidural PCA consumption. This effect is manifest whether ketamine is given before induction or 20 min after skin incision.