RESUMO
BACKGROUND: Magnesium, ropivacaine, gentamicin, and rocuronium block neuromuscular (NM) transmission by different mechanisms. Therefore, concurrent administration of these agents may induce prolonged muscle paralysis via synergistic interaction. This study investigated the efficacy and safety of NM block caused by the administration of high concentrations of magnesium in combination with ropivacaine, gentamicin, and rocuronium. METHODS: Eighty-three left phrenic nerve-hemidiaphragms from male SD rats (150-250 g) were hung in Krebs solution. Three consecutive single twitch tension (ST, 0.1 Hz) and one tetanic tension (TT, 50 Hz for 1.9 s) were obtained before drug application and at each new drug concentration. The concentration of MgCl2 and MgSO4 in Krebs solution was increased until an 80 to 90% reduction in ST was reached. To test the effects of combinations of NM agents, a Krebs solution was premixed with MgCl2 alone, MgCl2 and ropivacaine, or MgCl2, ropivacaine, and gentamicin. The concentration of ropivacaine, gentamicin, or rocuronium was then progressively increased until an 80 to 90% reduction in ST was reached. The effective concentrations were estimated with a probit model. RESULTS: The potency of MgCl2 was greater than that of MgSO4, and pretreatment with MgCl2 increased the potency of gentamicin and rocuronium. Unexpectedly, MgCl2 did not potentiate ropivacaine, and the potency of gentamicin and rocuronium failed to show an increase when premixed with 0.5 µM ropivacaine. CONCLUSIONS: The concomitant administration of high concentrations of magnesium and ropivacaine together with clinically relevant concentrations of gentamicin or rocuronium potentiated NM blockade but not with clinically relevant concentrations of ropivacaine.
RESUMO
BACKGROUND: Partially paralyzed patients may be placed in the risk of pharyngeal dysfunction. Bupivacaine acts as acetylcholine receptor ion channel blocker and may synergistically interact with rocuronium to augment NM blockade. Thus, this study aims to elucidate whether or not, at a therapeutic concentration, bupivacaine by itself may cause NM blockade and reduce an effective concentration of rocuronium. METHODS: Twenty-two left phrenic nerve-hemidiaphragms (Male SD rats, 150-250 g) were hung in Krebs solution. Three consecutive ST, 0.1 Hz and one TT, 50 Hz for 1.9 s were obtained before drug application and at each new drug concentration. A concentration of bupivacaine in Krebs solution (n = 5) was cumulatively increased by way of 0.01, 0.1, 1, (1, 2, 3, 4, 5, 6, 7) × 10 µM. In a Krebs solution, pre-treated with bupivacaine 0 (n = 5), 0.1 (n = 5), 1.0 (n = 5), 10 (n = 2) µM, and then concentrations of rocuronium were cumulatively increased by way of 1, 3, 5, 7, 9, 12, 14, 16, 18, 20 µM. EC for each experiment were determined by a probit. The EC(50)'s of rocuronium were compared using a Student's t-test with Bonferroni's correction. Differences were considered significant when P < 0.05. RESULTS: The potency of bupivacaine for normalized TF was 11.4 (± 1.1) µM. Below 30 µM of bupivacaine, the single twitch potentiation sustained despite the development of tetanic fade and partial inhibition of PTT. Bupivacaine significantly facilitated the NM blockade induced by rocuronium. CONCLUSIONS: Clinicians should be aware that bupivacaine by itself at its therapeutic concentration inhibit NM conduction and enhances rocuronium-induced muscle relaxation.
RESUMO
BACKGROUND: Spinal anesthesia is the most common regional anesthesia conducted for many surgical procedures. Multiple factors can affect the success, the side effects, and patient satisfaction with the procedure. This study was undertaken prospectively to discover factors affecting dissatisfaction and refusal of spinal anesthesia. METHODS: Starting in December 2007, patients who underwent spinal anesthesia in the operating rooms of our hospital were surveyed over a period of a year. Before attempting the procedure, patient characteristics and previous history of anesthesia were recorded. Spinal anesthesia was administered with 0.5% heavy bupivacaine combined with fentanyl 0-20 µg. Intraoperative data and postoperative data on the day after surgery were collected. The patients were also asked about their general satisfaction with spinal anesthesia, causes of dissatisfaction with the procedure, and causes of their refusal to have spinal anesthesia again. RESULTS: Six patients among 1,197 cases were excluded from the study because of spinal anesthesia failure. The dissatisfaction rate of spinal anesthesia was 3.7%, and its risk factors were more than three puncture attempts, paresthesia at puncture, postoperative nausea and vomiting, and postoperative backache. The refusal rate to have spinal anesthesia again was 3.2%, and its risk factors were postoperative backache and dissatisfaction. CONCLUSIONS: Although spinal anesthesia was conducted safely during the study and revealed a high rate of patient satisfaction (96.3%), side effects still occurred. Therefore, attending anesthesiologists must perform the procedure carefully and always pay attention to patients under spinal anesthesia.
