Epidural ketamine for postoperative analgesia in the elderly

Abstract

BACKGROUND: In this pilot study we examined the use of epidural ketamine as an opioid alternative for postoperative analgesia in elderly patients undergoing major abdominal surgery. METHODS: With the approval of the local REB we approached patients older than 65 years scheduled for major abdominal surgery. After obtaining written informed consent 20 patients were allocated to receive a bolus of epidural bupivacaine 0.125% supplemented either with epidural ketamine 40mg (ketamine group) or epidural morphine 2mg (morphine group) 30 minutes before surgery. Postoperative analgesia and sedation were assessed using a verbal rating score (0=no pain, 1=mild pain, 2=moderate pain, 3=severe pain) and Ramsay's sedation score, respectively. At the patient's request five ml boluses of 0.125% bupivacaine together with ketamine (2mg/ml) or morphine (0.1mg/ml) were given until a pain score of two at rest was established. The incidence of postoperative nausea and vomiting (PONV) requiring treatment was recorded. RESULTS: We approached and randomized 20 patients with 10 patients in each group. Mean age was 69±5 years in the morphine group and 69±3 years in the ketamine group. Pain scores immediately (0h) and (6h) after surgery were significantly higher in the ketamine group than in morphine group (0h: 2.5±2.0 versus 0.0, p=0.002; 6h: 1.8±1.3 versus 0.0, p=0.001). None of the patients receiving epidural morphine requested a top up within the first 24 postoperative hours. Eight patients in the ketamine group required additional boluses. The total amount of epidural ketamine administered was 70±19mg. Thirty minutes after the operation sedation score was higher in the morphine than in the ketamine group (4.1±1.2 versus 2.7±0.5, p=0.03). In the morphine group three patients had PONV while in the ketamine group PONV was not observed. CONCLUSION: The results of this pilot study show that epidural ketamine, when compared to epidural morphine, is associated with less sedation and a smaller risk of PONV, but necessitates more frequent or continuous administration to achieve comparable analgesia.

Wherefore ketamine?

“…A strong case can be made for the intrinsic toxicity of ketamine, however [32]. To my mind, it is clear that ketamine should not be administered spinally, especially in view of the fact that the gains are not impressive [37]. In the vein of neurological toxicity, permanent anosmia has also been reported in a patient on long-term (6 months) therapy with intranasal ketamine for chronic pain [38], a route that has been questioned previously [39].…”

Clinical, Biochemical and Haemodynamic Effects of the Intrathecal Ketamine for Ovariohysterectomy in Bitches

“…It is said that ketamine HCl administered intrathecally not only antagonises the NMDA receptors, but it also creates a sensory and motor blockage by blocking the calcium channels (2,8,10,16,17). Some researchers (6,20) have also noted that the effect of ketamine HCl is created by interacting with the opioid receptors in the spinal cord. El Shobary et al (6) claimed that it was more effective than morphine within the first 6 h after the operation and therefore, the IT ketamine could be used for postoperative analgesia.…”

“…Some researchers (6,20) have also noted that the effect of ketamine HCl is created by interacting with the opioid receptors in the spinal cord. El Shobary et al (6) claimed that it was more effective than morphine within the first 6 h after the operation and therefore, the IT ketamine could be used for postoperative analgesia. This study demonstrated that administering ketamine intrathecally achieved dissociative anaesthesia in a short time (1 min) and that even though the dissociative anaesthesia ended 95 min later, the anaesthesia has continued in the back legs and inguinal region (for other 17 min) as shown by clinical observation and pinprick tests.…”

A Prospective Randomized Double Blind Study on Efficacy of Dexmedetomidine and Ketamine as Adjuvant to Epidural Ropivacaine in Lower Abdominal and Lower Limb Surgery

“…but morphine provided prolonged analgesia in elderly patients. [18] Sethi et al studied ketamine in patient controlled epidural analgesia after abdominal surgery and concluded that ketamine reduces postoperative morphine consumption and is an effective adjuvant to local anesthetics. [19] Krishna T et al in their study opined that combined uses of ketamine and midazolam with intrathevcal bupivacaine provided prolonged analgesia compared to either ketamin or midazolam.…”