Reliability and variability in the measurement of interlimbal distance with a semiautomated video replay analysis system (SAVRAS)

Intraoperative succinylcholine and the postoperative eye alignment

In 99 patients undergoing strabismus surgery, an intravenous bolus of succinylcholine (Sch) was given after completion of the strabismus procedure. Reliable data were obtained in 53 patients. The interlimbal distance measured at 60 seconds after injection (VR60) was compared to the interlimbal distance at 1 and 6 weeks postoperatively, to evaluate the correlation between the drug-induced eye position under anesthesia and the awake-eye alignment postoperatively. Correlations were highest in patients undergoing symmetric recessions of the medial or lateral recti in primary horizontal strabismus. Confidence intervals of 0.8 to 1.2 were noted for both the esotropia and exotropia groups. Two patients experienced Sch-related complications of masseter spasm and prolonged apnea. Although infrequent, the potential gravity of the complications from Sch use and the currently enjoyed high rate of success in primary strabismus surgery suggest that these formulas not be used clinically. Nonetheless, the high correlations between the drug-induced and awake ocular position provide further support to the premise that the Sch sensitive fibers provide an important motor component to the awake eye position.

A comparison of the succinylcholine induced ocular position and the postoperative alignment in strabismus

Succinylcholine was injected intraoperatively in 41 strabismus patients with congenital esotropia or intermittent or constant exotropia. Regression analyses were performed to investigate the predictive relationships between the one-, six-, and 26-week postoperative alignment and the intraoperative, succinylcholine-induced ocular position. Ocular position, determined by the interlimbal distance in millimeters, was calculated using a semi-automated, video replay analysis system. Large, statistically significant correlation coefficients were obtained for patients undergoing bimedial recessions of 4.0 to 5.5 mm and bilateral lateral rectus recessions of 5.0 to 7.0 mm. Small correlations were obtained for esotropes undergoing the recession/resection procedure and those with bimedial recessions of 6.0 mm or greater. These data support the theory that the succinylcholine-sensitive subgroup of the extraocular muscle fibers are those whose tonic contracture provide the motor component to ocular alignment. Sample sizes at present are insufficient to suggest clinical use of these data. In future research, these relationships will be tested for their ability to predict postoperative alignment and thereby, improve success rates in strabismus surgery.