Low-dose ketamine with clonidine and midazolam for adult day care surgery.

EDITOR: The ideal anaesthetic for day-surgery procedures should give quick recovery without pain, nausea or vomiting and ensure a rapid return to preoperative mental state with rapid discharge and patient satisfaction. Ketamine was introduced into clinical practice nearly 40 yr ago but its use has declined. It nevertheless remains in regular use in certain surgical disciplines, e.g. paediatrics, plastic and burn surgery, during emergencies or during short diagnostic procedures. However, when administered to adult patients as the sole anaesthetic it frequently causes emergence reactions characterized by anxiety and hallucinations. A number of agents, including midazolam and clonidine, have been used to reduce or prevent these reactions. The aim of the present study was to test whether the combination of low-dose ketamine with midazolam, clonidine and ketorolac but without opioid administration, could provide adequate anaesthesia for interventions with low-to-medium pain potential performed on a day-surgery basis. This included breast surgery, laparoscopy, superficial excision of minor lesions, thoracoscopy, appendicectomy and proctological surgery. Five hundred patients, (172 males and 328 females) ASA Grade I–II, were enrolled in the study. All gave written, informed consent and were instructed in the use of the visual analogue scale (VAS). Overall mean age was 53.9 (SD 12.2) yr and mean weight 76.1 (SD 22.5) kg. Sedation was assessed using the Observer’s Assessment of Alertness/Sedation Scale (OAA/S) [1] and cognitive function was assessed with the Mini Mental State Examination [2]. The Profile of Mood State was used to assess mood [3]. Heart rate (HR), respiratory rate, oxygen saturation and arterial pressure were measured before and during surgery and for 1 h afterwards. Before induction of anaesthesia with propofol 2 mg kg 1, patients were given atropine 0.01 mg kg 1, midazolam 0.03– 0.05 mg kg 1 and ketamine 0.4 mg kg 1 all intravenously (i.v.). All patients received nitrous oxide 65% in oxygen. Muscle relaxation was obtained with suxamethonium (1.0–1.5 mg kg 1) or vecuronium (0.1 mg kg 1) for tracheal intubation and maintained with vecuronium. After tracheal intubation patients were given clonidine 150 μg i.v. If depth of anaesthesia was not adequate (blood pressure, BP or HR 20% of the preinduction values, lacrimation and sweating) patients were given ketamine 0.4– 0.6 mg kg 1 (maximum total dose 1 mg kg 1) or bolus injections of propofol 0.5 mg kg 1. The last ketamine administration was at least 1 h before the end of surgery. Ketorolac 30 mg and dexamethasone 8 mg were administered i.v. 30 min before wound closure. Total dose of ketamine used was 0.6 (SD 0.2) mg kg 1. At the end of the procedure, neuromuscular block was reversed using neostigmine, nitrous oxide was discontinued and the interval from this time to eye opening was recorded. Overall mean duration of surgery and anaesthesia were 121.4 (SD 60.1) min and 146.4 (SD 63.5) min, respectively. Time from discontinuation of nitrous oxide to eye opening was 176.9 (SD 106.1) s. Immediately after extubation and every 10 min thereafter, VAS scores for pain, sleepiness and nausea, OAA/S, and Aldrete score [4] were measured. In the first postoperative hour, ketorolac 0.3–0.6 mg kg 1 was administered if VAS for pain was 30. Patients were discharged from the recovery room when two consecutive Aldrete scores were 9 and all VAS scores were 30. At this time, the Profile of Mood State and Mini Mental State examination were repeated and patients were asked whether they felt strange or disoriented. Vital signs, nausea, pain, sleepiness and readiness for discharge from the hospital were assessed at 2, 3 and 4 h from the end of surgery. Patients were judged ‘ready for discharge’ (even if not actually dismissed from the hospital) when they had stable vital signs: no nausea, were oriented, able to ambulate unassisted Correspondence to: Carlo Ori, Dipartimento di Farmacologia ed Anestesiologia, Sezione di Anestesiologia e Rianimazione, Università degli Studi di Padova, via C. Battisti, 267 35121 Padova, Italy. E-mail: [email protected]; Tel: 39 0498213090; Fax: 39 0498754256