Purpose
To determine the influence of general anesthesia and strabismus surgery on children’s intellectual abilities.
Design
Prospective, observational study.
Methods
settings: Institutional. patients: Children 5 to 10 years of age receiving general anesthesia with sevoflurane and undergoing strabismus surgery were included. Intellectual abilities were examined before and 4 weeks after surgery using the Kaufman Assessment Battery for Children. Four subtests representing intellectual abilities related to complex cortical function were examined: identification of objects in a partially completed picture, reproduction of a presented design by using rubber triangles, selecting a picture that completes or is similar to another picture, and memory for location of pictures presented on a page. main outcome measures: Preoperative and postoperative age-adjusted scores of the 4 subtests of the Kaufman Assessment Battery for Children.
Results
The study group consisted of 21 children who underwent strabismus surgery under general anesthesia (mean duration, 51.3 minutes). The mean preoperative total score of the 4 subtests was 49.4 ± 6.2. The mean postoperative total score adjusted for potential learning effects and test–retest reliability was 48.1 ± 7.7. There was no significant postoperative change in the total score ( P = .108). However, the triangle test score decreased significantly after operation ( P = .019), particularly in patients with decreased stereoacuity after surgery.
Conclusions
General anesthesia with sevoflurane and strabismus surgery generally do not affect the intellectual abilities of complex cortical function in children 5 to 10 years of age at 4 weeks after surgery. Cortical functions related to hand–eye coordination may be affected by transient changes in postoperative stereoacuity.
Surgery and anesthesia may induce neurotoxic effects on the developing brain, causing long-term neurobehavioral abnormalities. This issue is important in children because learning abilities and intellectual functions are immature and vulnerable in the developmental period. Recent animal studies have found that exposure to anesthetic agents during sensitive periods of brain development may result in neuronal apoptosis and reduced neurogenesis. The functional consequences of these findings are yet to be elucidated, and translating the results from animal experiments into humans may be problematic. Results from human studies are scarce, and most of the studies are based on a retrospective history of anesthetic exposure in the early years of life, often showing conflicting results. Other confounding factors complicating the evaluation of anesthetic risk on brain development are nonstandardized anesthesia protocols with different types of anesthetic agents, dose and duration of exposure, different types of surgical stress, and the patients’ diverse underlying conditions.
In an attempt to understand this issue further, we performed a prospective study of children who underwent strabismus surgery under sevoflurane anesthesia and evaluated their intellectual functions before and after surgery to determine the direct causal effect of anesthesia and surgery on the intellectual abilities of children.
Methods
Patients and Ophthalmologic Examination
A prospective study was performed of children 5 to 10 years of age who underwent strabismus surgery under general anesthesia induced with sevoflurane. Patients with exotropia or esotropia requiring surgery were included. Patients were excluded if they had ophthalmologic problems other than strabismus, including amblyopia, a history of prior surgery performed, prior history of general anesthesia, systemic disorders such as congenital anomalies, or neurologic disorders. We noted preoperative patient characteristics, including gender, type of strabismus, age at surgery, refractive errors, and stereopsis. A thorough ophthalmologic evaluation was performed, including anterior segment findings and fundus examinations. Intraoperative procedures and type of surgery, postoperative alignment, and stereopsis also were collected. Sensory status was evaluated using the Randot stereoacuity test (Stereo Optical Co Inc, Chicago, Illinois, USA). Postoperative change in stereopsis was defined as a change of 2 octaves or more (doublings of threshold) of stereoacuity threshold.
Intelligence Function Tests
The Korean version of the Kaufman Assessment Battery for Children (K-ABC) was used to assess intellectual abilities in children. It comprises 3 global test scores, which are the sequential processing scale, the simultaneous processing scale, and the achievement scale. The sequential and simultaneous processing scales on the K-ABC measure intelligence and evaluate the child’s ability to solve unfamiliar problems simultaneously and sequentially. However, the subtests of the sequential processing scales of the K-ABC focus on rather simple operations or short-term recall; therefore, in this study, we used only the simultaneous processing scale to evaluate more complex cognitive intelligence. Four subtests of the simultaneous processing scale that were applicable to all age groups from 5 to 10 years were examined: (1) identification of objects in a partially completed picture (picture), (2) reproduction of a presented design by using rubber triangles (triangle), (3) selecting a picture that completes or is similar to another picture (visual analogy), and (4) memory for location of pictures presented on a page (location memory). The selected subtests of the K-ABC were undergone within 1 week before the operation, and the same test was administered 4 weeks after surgery. The same examiner (D.S.C.) scored each subject’s item responses to avoid scoring errors and to eliminate interobserver variability.
Anesthetic Methods
In each case, anesthesia was administered by an independent anesthesiologist. Continuous noninvasive monitoring of blood pressure, pulse rate, respiratory rate, and peripheral oxygen saturation was performed throughout each procedure. Supplemental oxygen was administered by use of a face mask. Preoxygenation was done with oxygen (O 2 ) via facial mask fitting, and induction was started with manual ventilation with sevoflurane (Sevorane, Abbott Korea, Korea) delivered at 1% to 3%, equivalent to 1.2 minimal alveolar concentration (MAC), and vaporized at atmospheric pressure in nitrous oxide and oxygen administered at a 1:1 ratio with a total gas flow rate of 2 L/minute. After induction, intravenous cannulation and injection of rocuronium 0.6 mg/kg was followed.
Main Outcome Measures
Age-adjusted scores of the subtests comprising simultaneous processing scales of the K-ABC were compared before and after surgery. Postoperative scores were adjusted for retest improvement, potential learning effects, and test–retest reliability.
Statistical Analysis
Statistical analyses were performed using SPSS for Windows version 15.0 (SPSS, Inc, Chicago, Illinois, USA). The Wilcoxon signed-rank test was used to compare preoperative and postoperative scores. The Mann–Whitney U test was used to compare scores between subgroups with different preoperative characteristics. The Spearman rank correlation coefficient was determined between potential factors related to postoperative decreases in test scores. P values less than .05 were considered statistically significant.
Results
A total of 21 patients requiring strabismus surgery were recruited in this study. The mean age of patients was 7.3 ± 1.6 years (range, 5.0 to 10.4 years). Thirteen (61.9%) of 21 patients were male. Nineteen patients had exotropia (90.5%) and 2 patients (9.5%) had esotropia. The mean refractive error was −0.79 ± 1.80 diopters (D; range, −3.25 to +3.50 D). Sixteen patients (76.2%) had good stereopsis of 100 seconds of arc or less, whereas 5 patients (23.8%) had stereopsis of more than 100 seconds of arc.
The mean duration of sevoflurane anesthesia was 51.3 ± 17.2 minutes (range, 30 to 110 minutes), and the mean time of operation was 29.6 ± 11.1 minutes (range, 13 to 54 minutes).
The mean age-adjusted preoperative K-ABC scores of the following indexes for the picture, triangle, visual analogy, and location memory tests were 12.1 ± 1.7, 12.2 ± 2.1, 12.1 ± 2.7, 13.0 ± 2.1, respectively. The mean age-adjusted preoperative total score was 49.4 ± 6.2. There was no significant difference in total scores according to gender, preoperative stereopsis, or type of strabismus ( P = .402, P = .901, and P = .587, respectively, Mann–Whitney U test), and this was similar in each subtest.
The mean age-adjusted postoperative scores for the picture, triangle, visual analogy, and location memory tests were 12.0 ± 2.4, 12.2 ± 2.7, 12.7 ± 2.3, and 13.6 ± 2.7, respectively, and the mean total score was 50.5 ± 7.7. The mean postoperative scores adjusted for potential learning effects and test–retest reliability of each subtest were 11.9 ± 2.4, 11.2 ± 2.8, 12.0 ± 2.3, and 13.2 ± 2.7, respectively. The mean postoperative total score adjusted for potential learning effects was 48.1 ± 7.7, and this was not significantly different from preoperative scores ( P = .108, Wilcoxon signed-rank test). Regarding subtests, the scores of the picture, visual analogy, and location memory tests did not show any significant postoperative change ( P = .221, P = .741, and P = .453, respectively). However, the triangle test score decreased significantly after operation ( P = .019).
Subgroup analysis was performed according to patients’ postoperative change in stereoacuity. Postoperative stereoacuity improved in 2 patients (9.5%), was maintained in 14 patients (66.7%), and decreased in 5 patients (23.8%). Of the patients with improved or maintained stereoacuity, there was no significant postoperative change in the total score ( P = .139) or in any of the subtests. Of the patients with decreased stereoacuity, there was no significant postoperative change in the total score or in the picture, visual analogy, or location memory test scores ( P = .680, P = .343, P = .343, and P = .892, respectively), but the triangle test score showed a trend of decrease after surgery ( P = .078). Regarding postoperative alignment at 1 month after surgery, all patients had satisfactory motor outcome within 5 prism diopters (PD) of esodeviation and 10 PD of exodeviation. However, the postoperative alignment at 1 day after surgery was variable between orthotopia and 30 PD of esotropia. Of the 5 patients with decreased stereoacuity, 1 patient (20%) with preoperative partially accommodative esotropia showed a monofixation syndrome at 1 month after surgery and had shown better preoperative stereoacuity tested with base-out prisms. The remaining 4 patients (80%) had preoperative exotropia, and all had consecutive esotropia of 20 PD or more on the first day after operation, reflecting a longer period of binocular suppression up to 1 month. Conversely, all but 1 patient (93.8%) with improved or maintained stereoacuity had less than 15 PD of esotropia on the first day after operation. There was no significant factor related to the amount of change in the total score or subtest scores, including age, duration of surgery or anesthesia, visual acuity, refractive error, and stereoacuity.
Results
A total of 21 patients requiring strabismus surgery were recruited in this study. The mean age of patients was 7.3 ± 1.6 years (range, 5.0 to 10.4 years). Thirteen (61.9%) of 21 patients were male. Nineteen patients had exotropia (90.5%) and 2 patients (9.5%) had esotropia. The mean refractive error was −0.79 ± 1.80 diopters (D; range, −3.25 to +3.50 D). Sixteen patients (76.2%) had good stereopsis of 100 seconds of arc or less, whereas 5 patients (23.8%) had stereopsis of more than 100 seconds of arc.
The mean duration of sevoflurane anesthesia was 51.3 ± 17.2 minutes (range, 30 to 110 minutes), and the mean time of operation was 29.6 ± 11.1 minutes (range, 13 to 54 minutes).
The mean age-adjusted preoperative K-ABC scores of the following indexes for the picture, triangle, visual analogy, and location memory tests were 12.1 ± 1.7, 12.2 ± 2.1, 12.1 ± 2.7, 13.0 ± 2.1, respectively. The mean age-adjusted preoperative total score was 49.4 ± 6.2. There was no significant difference in total scores according to gender, preoperative stereopsis, or type of strabismus ( P = .402, P = .901, and P = .587, respectively, Mann–Whitney U test), and this was similar in each subtest.
The mean age-adjusted postoperative scores for the picture, triangle, visual analogy, and location memory tests were 12.0 ± 2.4, 12.2 ± 2.7, 12.7 ± 2.3, and 13.6 ± 2.7, respectively, and the mean total score was 50.5 ± 7.7. The mean postoperative scores adjusted for potential learning effects and test–retest reliability of each subtest were 11.9 ± 2.4, 11.2 ± 2.8, 12.0 ± 2.3, and 13.2 ± 2.7, respectively. The mean postoperative total score adjusted for potential learning effects was 48.1 ± 7.7, and this was not significantly different from preoperative scores ( P = .108, Wilcoxon signed-rank test). Regarding subtests, the scores of the picture, visual analogy, and location memory tests did not show any significant postoperative change ( P = .221, P = .741, and P = .453, respectively). However, the triangle test score decreased significantly after operation ( P = .019).
Subgroup analysis was performed according to patients’ postoperative change in stereoacuity. Postoperative stereoacuity improved in 2 patients (9.5%), was maintained in 14 patients (66.7%), and decreased in 5 patients (23.8%). Of the patients with improved or maintained stereoacuity, there was no significant postoperative change in the total score ( P = .139) or in any of the subtests. Of the patients with decreased stereoacuity, there was no significant postoperative change in the total score or in the picture, visual analogy, or location memory test scores ( P = .680, P = .343, P = .343, and P = .892, respectively), but the triangle test score showed a trend of decrease after surgery ( P = .078). Regarding postoperative alignment at 1 month after surgery, all patients had satisfactory motor outcome within 5 prism diopters (PD) of esodeviation and 10 PD of exodeviation. However, the postoperative alignment at 1 day after surgery was variable between orthotopia and 30 PD of esotropia. Of the 5 patients with decreased stereoacuity, 1 patient (20%) with preoperative partially accommodative esotropia showed a monofixation syndrome at 1 month after surgery and had shown better preoperative stereoacuity tested with base-out prisms. The remaining 4 patients (80%) had preoperative exotropia, and all had consecutive esotropia of 20 PD or more on the first day after operation, reflecting a longer period of binocular suppression up to 1 month. Conversely, all but 1 patient (93.8%) with improved or maintained stereoacuity had less than 15 PD of esotropia on the first day after operation. There was no significant factor related to the amount of change in the total score or subtest scores, including age, duration of surgery or anesthesia, visual acuity, refractive error, and stereoacuity.
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