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BackgroundSedation in spinal anesthesia can reduce patient's anxiety and discomfort. Dexmedetomidine has a sedative, hypnotic, analgesic, and minimal respiratory depression effect. However, use of the dexmedetomidine is associated with prolonged recovery. This study was designed to investigate the optimal dose of intravenous dexmedetomidine for proper sedation with minimal recovery time in spinal anesthesia.MethodsOne hundred twenty eight patients, aged 20-70 years (58.8 ± 0.7), were recruited. After performing the spinal anesthesia with hyperbaric bupivacaine (13 mg), a loading dose of dexmedetomidine (1 µg/kg) was administered for 10 min, followed by the maintenance infusion of the following: Group A (n = 33; normal saline), Group B (n = 35; dexmedetomidine 0.2 µg/kg/hr), and Group C (n = 39; dexmedetomidine 0.4 µg/kg/hr). Heart rate, blood pressure, and the bispectral index score (BIS) were recorded during the operation. In the recovery room, modified aldrete score (MAS) was measured.ResultsThere were no significant differences in mean blood pressure and heart rate among the three groups. BIS was not significantly different among the three groups from baseline to 60 min after the infusion of dexmedetomidine. BIS were significantly increased in Group A after 70 and 80 min, and Group A and B after 90, 100, 110 min of dexmedetomidine infusion (P < 0.05). MAS was higher in Group A as compared to Group B and C, within 30 min after admission in the recovery room (P < 0.05).ConclusionsThe loading dose (1 µg/kg/10 min) of dexmedetomidine was sufficient for surgery of less than 60 min. Dexmedetomidine infusion followed by maintenance dose (0.2 µg/kg/hr) was sufficient for surgery within 90 min.

BackgroundRecently, the addition of dexmedetomidine to sedation regimens after cardiac surgery had been reported and there is a possibility that dexmedetomidine can cause vasoconstriction. Vasopressin has been used as a prophylactic treatment for refractory vasodilatory shock during coronary artery bypass graft (CABG). Also, vasopressin may play an important role in initiating spasms at the graft artery. Here we evaluate the direct effect of dexmedetomidine on isolated human gastroepiploic arteries and the synergistic effect of dexmedetomidine and vasopressin.MethodsDiscarded gastroepiploic arteries from elective subtotal gastrectomy (n = 10) were used in this study. We measured the level of contraction in isolated human gastroepiploic arteries induced by increasing concentrations of dexmedetomidine (10-10 to 10-6 M) with or without vasopressin (10-10, 10-9 M). Arterial contractions caused by increasing concentrations of vasopressin (10-10 to 10-7.5 M) with or without dexmedetomidine (10-9, 10-7 M) were also measured in the tissue samples.ResultsSupraclinical concentrations of dexmedetomidine elicited contractions at concentrations of 10-7 M and 10-6 M (P < 0.05 versus resting tension). The same concentrations of dexmedetomidine (10-7, 10-6 M) significantly enhanced vasopressin-induced contractions (P < 0.05 versus vasopressin-induced contraction). Vasopressin produced concentration-dependent contractions and vasopressin (10-10, 10-9.5, 10-9 M) also increased the intensity of dexmedetomidine (10-7 M) induced contractions.ConclusionsThere was a synergistic effect between supraclinical doses of dexmedetomidine and vasopressin on the degree of contraction in isolated human gastroepiploic arteries. However, a sedative dose of dexmedetomidine (clinical dose: 0.2-0.7 µg/kg/hr, plasma concentration: 0.36-1.25 ng/ml) did not enhance vasopressin induced-contraction in isolated human gastroepiploic arteries.

Transesophageal echocardiography (TEE) has an important role during congenital heart surgery. TEE in small infants is associated with complications, including an inability to pass the TEE probe, esophageal trauma, airway compression, aortic compression, and interference with ventilation. Recently, a monoplane intravascular ultrasound catheter (IVUC) has been developed for intracardiac echocardiography. The efficacy of IVUC for transesophageal use has been shown in numerous animal studies and several human studies, but there have been few reports involving small infants using an IVUC probe. We examined 15 pediatric patients undergoing congenital cardiac surgery using an 8-Fr AcuNav IVUC probe. We checked the cardiac anatomy, cardiac function pre-operatively and de-aeration before weaning from CPB; the surgical repairs were evaluated post-operatively. Although the IVUC probe has limitations associated with the monoplane, we found the IVUC probe to be useful in small infants and safer than the TEE.