Differences in sensitivity to rocuronium among orbicularis oris muscles innervated by normal or damaged facial nerves and gastrocnemius muscle innervated by somatic nerve in rats: combined morphological and functional analyses.

OBJECTIVES/HYPOTHESIS: To evaluate mechanisms of discrepant responses to the nondepolarizing muscle relaxant rocuronium among normal and injured facial nerve-innervated orbicularis oris and tibial nerve-innervated gastrocnemius, and to provide information for the proper use of muscle relaxants to balance evoked electromyography (EEMG) monitoring and immobility in general anesthesia. STUDY DESIGN: Randomized controlled study. METHODS: Right-sided facial nerve injury was induced by crush axotomy in 18 Sprague-Dawley rats. At different rocuronium concentrations, muscular tension amplitude (MTA) was determined in vitro for normal and injured facial nerve-innervated orbicularis oris and gastrocnemius; the number of unsaturated acetylcholine receptors (AChRs) at end plates was determined by (125) I-α-bungarotoxin staining followed with gamma spectroscopy. The morphological composition of muscle fibers was determined by histological examination. RESULTS: Following rocuronium incubation, the percentage of MTA inhibition (MTAI%) of gastrocnemius was significantly higher than the corresponding values of orbicularis oris (P < .05), and the degree of saturation of AChR in gastrocnemius was significantly greater than that in orbicularis oris (P < .05). The baseline MTA and AChR density of injured-side orbicularis oris was significantly smaller than those of the normal side, whereas no significant difference was found regarding MTAI% and the degree of AChR saturation between the normal and injured side. CONCLUSIONS: The affinity of AChR at end plates and different number of AChR per unit fiber cross-sectional area may be the mechanisms for differential sensitivities to neuromuscular blockers between facial nerve-innervated muscles and somatic nerve-innervated muscles. The lower EEMG responses in the impaired facial nerve-innervated muscles may result from the lower AChR density at end plates compared with the normal facial nerve-innervated muscles.

[Clinical evaluation of the heart function early after repair of tetralogy of Fallot: follow-up of 43 patients].

OBJECTIVE: To evaluate the heart function of the patients early after the repair of tetralogy of Fallot (TOF). METHODS: Forty-three patients with TOF, 25 males and 18 females, underwent operation at the age of 2.5 - 52 years (16.7 years on average) and were followed up for 1 - 3.5 years. Twenty-one age-matched healthy persons were used as controls. Tissue Doppler imaging (TDI) was used to measure the values of the peak tricuspid ring velocity during early diastole (Ea), late diastole (Aa), systole, and isovolumic contraction, and isovolumetric contraction acceleration (IVA); and isovolumetric contraction time (ICT), isovolumetric relaxation time (IRT), and isovolumetric contraction velocity (IVV) of the right ventricle. Tei index was calculated using the formula: (ICT + IRT)/ET. Treadmill test was used on the patients aged > 17 to measure the maximal heart rate maximal blood pressure, maximal exercise tolerance (MET), and movement time. RESULTS: The peak tricuspid ring velocity during Ea of the repaired TOF group (rTOF group) was 11.5 +/- 2.6 cm/s, significantly lower than that of the control group (17.1 +/- 2.4 cm/s, P < 0.0001), the peak tricuspid ring velocity during Aa of the rTOF group was 9.6 +/- 1.7 cm/s, significantly lower than that of the control group (12.9 +/- 2.9 cm/s, P < 0.001), the E/A of the rTOF group was 1.16 +/- 0.36, significantly lower than that of the control group (1.36 +/- 0.26, P < 0.05). The IVV of the rTOF group was 7.7 +/- 1.8 cm/s, significantly lower than that of the control group (9.9 +/- 1.4 cm/s, P = 0.0030, and the IVA of the rTOF group was 131.7 +/- 37.6 cm/s(2), significantly lower than that of the control group (222.5 +/- 39.2 cm/s(2), P < 0.001). The Tei index of the rTOF group was 0.58 +/- 0.11, significantly higher than that of the control group (0.52 +/- 0.04, P = 0.029). The maximal heart rate maximal blood pressure, MET, and movement time of the rTOF group were all significantly lower than those of the control group (P < 0.05 or P < 0.01). CONCLUSION: The heart function of the patients undergoing repair of TOF fails to recover to the normal level during a short time after the surgery.

Right ventricular dysfunction due to right ventricular outflow tract patch.

Doppler tissue imaging analysis was used to examine the relationship between right ventricular function and right ventricular outflow tract damage in 54 patients with repaired tetralogy of Fallot. The patients were divided into three groups: 16 in whom the right ventricular outflow tract was directly sutured (group DS), 23 who had transventricular patch repair (group TVP), and 15 who had transannular patch repair (group TAP). The control group consisted of 16 age-matched patients who underwent patch closure of a ventricular septal defect (group C). The Tei index was obtained from tricuspid and pulmonary Doppler flow velocities. The right ventricular Tei index was significantly greater in groups TVP and TAP than in group DS. Doppler tissue imaging analysis in groups TVP and TAP showed shorter myocardial systolic velocity, diastolic peak velocity, and atrial diastolic peak velocity, lower peak myocardial velocity and acceleration during isovolumic contraction, and prolonged isovolumic relaxation and contraction times compared to groups DS and C. Right ventricular dysfunction is due to the right ventricular outflow tract patch. Thus, the right ventricular outflow tract may be essential for right ventricular ejection and maintenance of right ventricular function.