July 2005 - The Hong Kong College of Anaesthesiologists

More documents

Recommendations

Info

Bull HK Coll Anaesthesiol Volume 14, Number 2 July 2005Low‐dose Subcutaneous Ketamine Infusion: a Dose FindingStudy for Post‐operative Analgesia1Derek LS Chan, 2 Tommy KL Suen, 3 Anne KwanDepartment of Anaesthesia, United Christian Hospital, Hong KongSUMMARYIn this double‐blinded, randomized controlled trial we determined the optimal dose of subcutaneousketamine infusion required for post‐operative analgesia after major abdominal surgery. Patients wererandomly allocated to receive either 0.9% saline or one of three ketamine doses (0.05, 0.1, 0.2 mg/kg/h),given as subcutaneous infusion. All patients were given intravenous morphine for postoperativeanalgesia using the patient‐controlled analgesia pump. A total of 50 patients completed the study. Fivepatients (one had ketamine 0.05 mg/kg/h; 2 received 0.1 mg/kg/h and 2 had 0.2 mg/kg/h) developedsevere psychomimetic adverse reactions that significantly compromised their safety. Postoperatively,there were no differences among groups in subjective assessment of analgesic efficacy, pain scores at restand on movement, opioid consumption and other adverse reactions. We observed a trend of lower PCAmorphine consumption among the ketamine groups. We concluded that the use of low‐dosesubcutaneous ketamine infusion for post‐operative analgesia is not recommended until furtherinformation regarding side effects profile is available.Keywords: Ketamine, Patient controlled analgesia, Anesthesia, Dose finding studyBull HK Coll Anaesthesiol 2005;14:83‐9Ketamine is a well know anesthetic agentfor over three decades. It has analgesicproperties at sub‐anesthetic doses. 4‐12,14,16This is related to a non‐competitive antagonism1MBBS, BSc(Med), FANZCA, FHKCA, FHKAM(Anaesthesiology), Associate Consultant; 2 MBBS,FANZCA, FHKCA, FHKAM (Anaesthesiology),Senior Medical Officer; 3MB BS, FANZCA,FHKCA, Dip Pal Med, Dip Pain Mgt (HKCA)FHKAM (Anaesthesiology), Dip Epi & Biostat, DipAcup, M Pal Care, Consultant and Chief of Service.Department of Anaesthesia, United Christian Hospital.Address correspondence to: Dr Derek Chan,Department of Anaesthesiology and OperatingServices, Alice Ho Miu Ling Nethersole Hospital, TaiPo, NT. E‐mail: dlschan@yahoo.com.hk83at the N‐methyl‐D‐aspartate (NMDA) receptorat the level of spinal cord dorsal horn. 1‐3 NMDAreceptors have an important role in thedevelopment of wind‐up phenomenon andlong‐term central sensitization of the painpathway. 2The use of sub‐anesthetic, low doseketamine as an analgesic has been investigated.Several reports have produced positive results,without the occurrence of dose‐dependentpsychomimetic side effects. 4,5,17,18 Effects oncardiovascular and respiratory systems are alsominimal at this range of doses. 4,5,7,10,12,17,18 Thereported analgesic efficacy is comparable to thatof morphine and pethidine without the commonside effects such as respiratory depression, 5,8,11,12
Bull HK Coll Anaesthesiol Volume 14, Number 2 July 2005urinary retention, sedation, pruritus andtolerance. 4,13 The incidence of nausea andvomiting is less than or equal to that ofopioids. 4,13 When used as an adjunct, ketaminehas an opioid‐sparing effect. 4 A ketaminesubcutaneous infusion of 0.1 mg/kg/h has beenshown to produce similar analgesic efficacy as amorphine infusion of 0.03 mg/kg/h subcutaneously.5 In this regard, adequate analgesiawith fewer side effects will result in quickerrecovery and fewer complications. Thus, in thelong run, ketamine administration shouldreduce costs and potentially opioid tolerance,dependence, and chronic pain syndrome.Various routes of administration, includingsubcutaneous, have been examined and areeffective in providing analgesia. However, theoptimal dose range of subcutaneous ketamineinfusion for analgesia has not been found.Subcutaneous infusion is simple to administerand does not require an intravenous access. Thisstudy aims to provide clinicians withinformation on a useful alternative or adjuvantto postoperative analgesia.MethodsAfter obtaining hospital ethics committeeapproval, patients admitted for electiveabdominal surgery involving a midline incisionwere invited to participate if they had chosen IVpatient controlled analgesia (PCA) for postoperativepain relief. With written, informedconsent, 50 patients were randomly allocatedinto four groups receiving either 0.9% saline(Group S) or one of three ketamine doses (0.05,0.1 and 0.2 mg/kg/h, Group Ket 0.05, Ket 0.1,and Ket 0.2, respectively) given as asubcutaneous infusion. All patients wereprovided with PCA morphine. The pumps wereprogrammed to deliver morphine 1 mg bolus,lockout interval of 8 min and 4 hourly limit of0.25 mg/kg. Premedication was not prescribed.General anesthesia consisted of induction withthiopentone, maintenance with isoflurane in70% nitrous oxide/oxygen mixture. Trachealintubation and intra‐operative paralysis werefacilitated by either atracurium, cisatracurium orrocuronium. We gave morphine and/or fentanylfor intraoperative analgesia. The actual conduct84of anesthesia was left to the discretion of theattending anesthetists. A subcutaneous bolus ofketamine (0.2 mg/kg) was given immediatelyprior to the infusion while patients in the groupS received equivalent volume of 0.9% normalsaline. The infusion was commencedimmediately after induction of generalanesthesia prior to surgical incision. The anteriorchest wall was used as the infusion site becauseit caused minimal interference with the surgeryand provided easy access for inspection andreposition during study period. The infusionwas given via a 25G subcutaneous infuserneedle of known volume, and the syringe drivenby a syringe pump (Terumo Corporation, Tokyo,Japan). List anesthetists, recovery room nurses,ward staffs, and patient assessors were blindedto the treatment used.Data collection was started at induction ofgeneral anesthesia and lasted for 72 hours aftercommencement of PCA use. Ketamine wasinfused for the first 48 hours. Ward nursesexperienced in looking after continuousinfusions and PCA pumps monitored thepatients. Patients suffering from nausea andvomiting were treated with metoclopramide 10mg IVI, as requested and those showingpsychomimetic symptoms were treated withdiazepam 2 mg IVI every 8 hours, as indicated.Patient demographic data were recorded.Intraoperative data included type and durationof surgery, length and dermatomal range ofincision, and total opioid dose. Recovery dataincluded length of hospital stay, total opioiddose. Pain scores were recorded using a 11‐pointverbal rating scale (VRS: 0 = no pain, 10 = worstpain imaginable) at rest and on movement.Postoperatively, 2 hourly nursing observationsincluding pain scores, sedation scores (0 = alert,4 = unarousable), presence of nausea, vomiting,PCA consumption, volume of study druginfused, heart rate, arterial pressure, respiratoryrate, and pulse oximetry reading. The acute painservice also assessed the patients twice daily forthe presence of hallucination, vivid dreams, andother psychomimetic side effects such asparanoia and delusion. At the end of the 48‐hourinfusion, patient were asked to give asatisfactory score of the effectiveness of
Page 2: Bull HK Coll Anaesthesiol Volume 14
Page 6 and 7: Bull HK Coll Anaesthesiol Volume 14
Page 12 and 13: Clinical InvestigationsBull HK Coll
Page 36 and 37: Case ReportsBull HK Coll Anaesthesi

July 2005 - The Hong Kong College of Anaesthesiologists

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?