Denervation stage differentially influences resistance to neuromuscular blockers in rat gastrocnemius.

BACKGROUND: Muscle denervation was common in clinical surgery patients, which was mostly caused by trauma, paraplegia, and other factors. Denervated muscle in patients could lead to significant differential reaction to neuromuscle blockers due to the time of denervation and affected muscle area. We tested the hypothesis that resistance to non-depolarizing muscle relaxants (NDMRs) changes with time, and is related to the expression of immature and total acetylcholine receptors (AChRs). MATERIALS AND METHODS: The study evaluated the effect change of neuromuscular blockers in tibial nerve transected rat model. To determine 50% effective dose of NDMRs and succinycholine at 1, 7, 14, 28, and 35 days after denervation, action potential amplitude was monitorted by intracellular recording method. The messenger DNA that encodes the AChR-γ and AChR-ε subunits and the protein of the -γ and -ε subunits were quantified in the gastrocnemius by reverse transcription-polymerase chain reaction and western blotting respectively. Receptor number and pharmacodynamic changes was analyzed by correlation and regression analysis. RESULTS: Increased AChR-γ correlated with total AChRs, suggesting that the up-regulated AChRs may contain the immature isoform. The 50% effective dose of vecuronium and atracurium increased 1.2- to 1.5-fold at all time periods and correlated significantly with AChRs and AChR-γ. CONCLUSIONS: After denervation, resistance to NDMRs occurred earlier, was more marked from 14 days, and changes in resistance to NDMRs in skeletal muscle after nerve injury is dependent on the level of expression of immature and total AChRs. Denervation time should be of concern when such patients undergo surgery.

Cerebral protective effect of nicorandil premedication on patients undergoing liver transplantation.

BACKGROUND: Neurological injury is a common complication in the early period after liver transplantation, posing an enormous obstacle to treatment efficiency and patient survival. Nicorandil is a mitochondrial ATP-sensitive potassium channel (mitoKATP) opener. It has been reported to be effective in reducing brain injury in recent studies. However, it is still unclear whether nicorandil has cerebral protective effect in patients undergoing liver transplantation. METHODS: Fifty patients scheduled for liver transplantation were randomly divided into a nicorandil group (group N) (n=25), in which patients received 10 mg nicorandil through a nasogastric tube 30 minutes before induction of anesthesia, and a control group (group C) (n=25) who received 10 mL normal saline. The Mini-Mental State Examination (MMSE) was performed before anesthesia (day 0), and on days 3 and 7 after surgery. Blood samples were obtained before induction of anesthesia (T1), and at 12 (T2) and 36 hours (T3) after surgery for determination of serum neuron-specific enolase (NSE) and S100ß protein (S100ß) concentrations. RESULTS: During surgery, 5 patients in each group were eliminated due to severe reperfusion or renal insufficiency. Therefore, 20 patients remained in each group. The MMSE scores after operation were significantly lower than those before operation in group C. However, there was no difference at days 3 and 7 compared with day 0 in group N. Serum NSE concentrations after surgery were significantly higher than baseline (at T1) in both groups, except at T3 in group N. Serum S100ß concentration after surgery was significantly higher than baseline (at T1) in both groups. The MMSE scores at days 3 and 7 in group N were significantly higher than those in group C. The concentrations of serum NSE and S100ß at T2 and T3 in group N were significantly lower than those in group C. CONCLUSIONS: Oral nicorandil, as a premedication before liver transplantation, improves postoperative MMSE scores. It also attenuates the increase of NSE and S100ß in blood, indicating its cerebral protective effect.