Comparison of mepivacaine and lidocaine for intravenous regional anaesthesia: pharmacokinetic study and clinical correlation.

BACKGROUND: Limitations to the use of lidocaine for intravenous regional anaesthesia (IVRA) include lack of optimal intraoperative analgesia and systemic toxic reactions. This randomized double-blind study was conducted to compare intraoperative and postoperative analgesia, adverse effects, and plasma concentrations of mepivacaine or lidocaine, on release of the tourniquet in patients undergoing IVRA for distal upper limb surgery. METHODS: Forty-two adult patients were randomly allocated to receive either a 0.5% lidocaine solution 3 mg kg(-1) (n=20) or mepivacaine 5 mg kg(-1) (n=22). Plasma concentrations of both anaesthetic agents were measured at 5, 10, 20, 30, 45, and 60 min after deflation of the tourniquet by gas chromatography. RESULTS: Although plasma concentrations of mepivacaine and lidocaine were comparable 5 min after deflation, concentrations of lidocaine decreased significantly thereafter, whereas plasma concentrations of mepivacaine were similar over the 60-min study period. Supplementary analgesia during the intraoperative period was required by 45% of patients in the lidocaine group as compared with 9% in the mepivacaine group (P=0.02). No adverse effects were observed in patients given mepivacaine. In the lidocaine group, adverse effects were observed in 10% of the patients. The total ischaemia time, volume of the local anaesthetic, and duration of the surgical procedure were not significantly different between the two groups. CONCLUSIONS: Mepivacaine 5 mg kg(-1) ensured better intraoperative analgesia than lidocaine 3 mg kg(-1) when used for IVRA. Plasma concentrations of lidocaine decreased significantly between 5 and 60 min following tourniquet deflation, whereas blood concentrations of mepivacaine remained below the toxic concentration.

[Agranulocytosis caused by metamizol. Anesthetic attitude]. / Agranulocitosis por metamizol. Actitud anestésica.

Agranulocytosis induced by metamizole is uncommon, with a frequency of less than one case per million treatments. We describe such a case in a patient requiring emergency surgery. An 85-year-old man with a history of infantile paralysis with mental retardation and Paget's disease and X-ray signs of the right femur came to the emergency room with a diaphysial fracture. He received 1 g metamizole i.v. every 8 hours for analgesia. Ten hours after admission a routine blood cell count showed a rapid fall in the number of leukocytes; at 24 hours the count was 600 x 10(9)/l. The diagnosis was agranulocytosis induced by metamizole. Postponement of surgery was advisable and treatment with granulocyte colony stimulating factor (GCSF) at a dose of 5 micrograms/kg/day. Agranulocytosis resolved after 3 days of treatment, after which time the bone was set with a straight femoral plate under subarachnoid anesthesia. Two packs of red blood cells were required during the immediate postoperative period. Twelve days after surgery the patient was released. We review the anesthetic approach to agranulocytosis and its treatment.

[Comparative study of postoperative analgesia with methadone and fentanyl in continuous peridural perfusion]. / Estudio comparativo de la analgesia postoperatoria con metadona y fentanilo en perfusión peridural continua.

OBJECTIVE: To determine whether continuous epidural perfusion of fentanyl, which is more liposoluble than methadone, provides a similar level of analgesia with fewer side effects than methadone administered by the same route for postoperative pain. PATIENTS AND METHODS: Prospective double blind study of 40 patients, randomly assigned to two groups. Group F (n = 20) received 300 micrograms-1200 micrograms/24 h in epidural perfusion. Group M (n = 20) received 9 mg-18 mg/24 h in epidural perfusion. In both cases treatment was for pain in the first 72 h after abdominal surgery. Analgesia quality was evaluated on a visual analog (VAS) scale from 1 to 10 at rest and moving. Need for complementary analgesia was also recorded, as were side effects related to the technique. RESULTS: Quality of analgesia was good and similar which both drugs. Postoperative pain did not surpass 3 on the VAS at rest or 4.5 while moving, although group F patients' need for complementary analgesia was significantly greater (p < 0.05). The incidence of hypoxemia was greater in group M than in group F (p = 0.05). CONCLUSIONS: Continuous epidural perfusion of fentanyl provides good analgesia and is associated with less hypoxemia than is methadone.