When local anesthetics are used, the administration of dexmedetomidine (DEX) can prolong analgesic duration. However, the effect of caudal DEX on high volume/low concentration (HVLC) local anesthetics has not been studied. We investigated the analgesic effect of DEX added to a HVLC of ropivacaine for caudal block in children. Eighty children (the American Society of Anesthesiologists (ASA) status I; age, 1-6 years) undergoing ambulatory orchiopexy were enrolled in the study. Children were randomly assigned to undergo a caudal block with 1.5 mL/kg of 0.15% ropivacaine and either 1 µg/kg of DEX (DEX group, n 40) or the same amount of saline (Control group, n 40) under general anesthesia. The results showed that the time to first analgesic request was significantly longer in the DEX group than in the control group. The sevoflurane requirement for anesthesia and frequency of emergence agitation (EA) were also significantly lower in the DEX group. There was no difference in adverse events between the two groups. In conclusion, a dose of 1 µg/ kg of caudal DEX prolonged the first analgesic request time, although the immediate postoperative pain scores were comparable in both groups. Furthermore, caudal DEX significantly reduced the sevoflurane requirement and the frequency of EA.Key words dexmedetomidine; caudal block; child; orchiopexy Caudal block is common method for postoperative analgesia in children undergoing infra-umbilical surgery. One major limitation of caudal block is a relatively short analgesic duration owing to the single-injection. Thus, adjuvants such as ketamine, clonidine, or opioids are frequently added to the local anesthetics in order to improve analgesic efficacy and duration.1,2) The effectiveness of local anesthetics using in caudal block is dependent upon the dose, volume, and concentration of the local anesthetic solution, but high-concentration local anesthetics can increase the incidence of motor weakness, delayed micturition, or urinary retention. In children undergoing ambulatory surgery, such adverse effects can prolong the discharge time and may result in inadvertent admission. Recently, high-volume/low-concentration (HVLC) regimens for caudal blocks in children (1.5 mL/kg of 0.1-0.2% local anesthetics) have gained popularity following a report by Silvani et al. that demonstrated that a HVLC regimen provides a longer analgesic duration with less adverse effects than conventional dose/concentration. [3][4][5][6][7][8] However, the analgesic duration is still limited in caudal block with single-injection.Dexmedetomidine (DEX) is a highly selective α 2 adrenoceptor agonist with an α2/α1 selectivity ratio of 1600 : 1, and is eight times more potent than clonidine. 9) DEX is successfully used as an adjuvant in caudal blocks for children in order to reduce pain without inducing any significant respiratory and hemodynamic effects. Several studies have reported that in children, caudal DEX (1-2 µg/kg) with 0.25% bupivacaine (1 mL/kg) prolongs postoperative analgesic duration by 2.5-3 fold comp...

Malignant hyperthermia (MH) may lead to metabolic crisis of skeletal muscle in susceptible individuals following exposure to triggering agents such as volatile anesthetics or depolarizing muscle relaxants. MH is a rare and a potentially lethal disease, which can lead to cardiac arrest. We report a case of severe MH, in which the rapidly evolving signs of hypermetabolism eventually resulted in cardiac arrest. Despite conventional treatments following cardiopulmonary resuscitation, the patient's vital signs did not improve. Therefore, we applied extracorporeal membrane oxygenation for providing hemodynamic support.