In a 3-year period, one of the authors (J.D.A.C.) found that adults with horizontal misalignment were better treated with the adjustable suture technique if they had received conscious sedation rather than general anesthetia for the primary surgical stage of the repair.
The phrase "conscious sedation" means the use of intravenous agents to produce a minimally depressed state of consciousness to supplement regional or local anesthesia while maintaining the patient's protective reflexes intact.1
The adjustable suture technique of strabismus repair as described by Jampolsky2 revolutionized the treatment of nonaccommodative strabismus. Most surgeons have continued to use Jampolsky/s technique of general anesthesia for the primary surgical repair, and topical drop anesthesia for the subsequent secondary adjustment, usually performed within 24 hours after recovery from the general anesthetic. There is, however, a difficulty in making the adjustment in patients who are recovering from a general anesthetic, in that they may feel nauseated and unwell for as long as 18 to 24 hours after they have recovered consciousness. These factors may delay the final adjustment process and make it qualitatively more difficult, and in addition may increase the time spent in the Day Care Surgical Unit (DCSU).
Consciously sedated patients recover full normal consciousness rapidly, usually within 30 minutes of the primary procedure, are nauseated infrequently, and have a postsedation euphoric phase that is helpful to the surgeon performing the adjustment.
We present a retrospective review of 50 adult patients treated with the adjustable suture technique. The patients underwent either general anesthesia or conscious sedation, followed by local anesthetic conscious adjustment on the same day in the DCSU. We compared the incidence of nausea and pain, time for the primary surgical procedure, and total time in the DCSU, as well as preoperative and postoperative deviation and percent net change in deviation between the two groups.
MATERIALS AND METHODS
A consecutive series of patients with adjustable suture repair of strabismus treated by one of us (J.D.A.C.) in the period 1989 to 1992 was analyzed. All patients with vertical or oblique misalignment were excluded, leaving 50 patients with isolated horizontal strabismus. Twentythree of the 50 patients were treated with the conscious sedation method, and 27 with general anesthesia.
All patients received a complete ophthalmologic and strabismologic evaluation. The deviations were measured te an accommodative target in all cardinal positions of gaze at Vs of a meter and 6 meters in all patients. In exotropes, one deviation was also measured past 20 feet. Fusion and stereopsis were evaluated at near with Lang, Titmus, and Bagolini lenses and troposcope, and at distance with the AO vectograph. Where possible, Hess screens and field of single binocular vision were recorded.
All patients were examined on at least three occasions before surgery was performed. The procedure was explained carefully to the patients. All patients passed the "Q-tip test" as a preoperative rehearsal of the secondary adjustment process. During this test, the patients learned that although a feeling of pressure might remain, there would be no sensation of pain with the continued topical drop anesthesia.
Time Taken for Primary Surgery and Total Time in DCSU
Frequency of Postoperative Pain and Nausea
Because of the "gate theory* of pain propounded by Wall3 and Melzak, it has been the author's practice to use preemptive topical analgesia with 0.5% Marcarne without adrenaline on all strabismus repairs during the initial surgical intervention and continuing through the recovery stage until final adjustment. In this theory, preemptive use of a topical anesthetic agent prevents the opening of subconscious pain pathways, allowing greater patient comfort and thus a greater ability to concentrate on the adjustment itself
All patients were attended by a specialist anesthetist who remained present throughout the procedure. Their vital signs were monitored with an automatic blood pressure (BP) cuff and a continuous three-lead EKG and pulse oximeter.
Those patients receiving general anesthesia were given similar doses of fentanyl or sufentanil as those receiving conscious sedation. They did not receive any benzodiazepines, but were given Pentothal or propofol as induction agents (Pentothal 3 to 5 mg/kg, propofol 2 to 3 mg/kg). They received succinylcholine 1 to 2 mg/kg, and were intubated with an endotracheal tube. In a few cases only, no relaxants were given and the patient was intubated with a laryngeal mask airway (LMA). The intubated patients were paralyzed with vecuronium (15 µ-g/kg), and ventilated with isoflurane. Those with the LMA breathed spontaneously and were also anesthetized with isoflurane. At the end of the procedure, those paralyzed were reversed with edrophonium (0.5 mg/kg), and atropine 0.6 mg. The intubated patients were extubated in the operating room, and those with the LMA had the airway removed in the recovery room once they were conscious.
In the postanesthetic recovery room (PAR), all patients' vital signs were monitored continuously with BP and pulse oximeter, and their pulse was measured every 5 minutes until alert. The PAR nurses instilled topical drop anesthesia, bupivacaine 0.5%, every 10 minutes until adjustment. In all patients adjustment was performed on the day of operation, before leaving the DCSU.
Postoperatively, all patients were examined initially within the first week, and again at 6 weeks and 6 months postoperatively. Their percent net change in deviation was calculated from a formula applied using the preoperative deviation in primary position, which was measured within 1 week prior to surgery, and the postoperative deviation measured within 1 week after surgery. We used the formula:
Percent net change in deviation = [(Preoperative deviation - Postoperative deviation) 4- Preoperative deviation] x 100
We also evaluated all 50 hospital charts for medications given to patients in the DCSU. We felt that this was objective post hoc evidence for postoperative pain and nausea (better than subjective patient and physician recollection).
The DCSU nurses charted the time from the patient's entry into the operating room until final discharge from the DCSU. This included a separate category for the length of the primary surgical procedure. Unfortunately, the length of time taken for the secondary adjustment process was noted inconsistently in the charts, so we were unable to use these data.
Table 1 compares the time for the primary surgical care and the total time in the DCSU in the two groups. Although the surgical time was somewhat less in the general anesthesia group, their total time in the DCSU was greater than in the conscious sedation group. However, because of the small sample size, a statistically valid comparison could not be made.
Postoperative nausea occurred in the general anesthesia group only (5/27 = 16%). In other words, 22/27 general anesthesia patients (84%) and 23/23 (100%) conscious sedation patients were able to have adjustable suture repairs and to cooperate with the secondary adjustment process without nausea impeding their ability to focus on the task at hand (Table 2).
Postoperative pain was experienced in a similar proportion of both groups after the adjustment was completed and the topical bupivacaine 0.5% eyedrops were no longer instilled (Table 2). Most patients were then given oral acetaminophen 300 mg and codeine 30 mg.
Results of Treatment
In the first 15 to 20 minutes after patient entry into the PAR, the nursing staff reported that much less vigilance and intensity of care was needed for the consciously sedated patient than for the general anesthesia patient. It was difficult to quantify this difference, but after 20 minutes, the nursing intensity became independent of the anesthetic technique.
There was no statistically significant difference in the values of the preoperative and postoperative deviations between the two groups. The values of the percent net change were also similar, with the consciously sedated patients achieving a larger percent net change for both esotropia and esotropia correction than the general anesthesia group (Table 3).
In North America, physicians and hospitals are seeing dramatic shifts in surgical practice, from inpatient general anesthesia to outpatient conscious sedation and local anesthesia settings. This has already been seen in general ophthalmology with cataract extraction.4 Cataract surgery performed in a physician's office or surgery center was found to cost one half the amount of similar surgery in a hospital's integrated ambulatory department.4 While the total time in the DCSU was 42 minutes less for the conscious sedation patients than the general anesthesia patients, the time spent in the recovery area also required much reduced intensity of nursing care. Also more patients could be treated in that DCSU on that day because of a faster turnover time if the patients were consciously sedated.
By using conscious sedation rather than general anesthesia for adjustable suture surgery, patients have a more rapid recovery of their own conscious focus; thus are able to achieve a successful realignment within 30 to 60 minutes of the initial surgery, instead of up to 24 hours later. The use of preemptive persistent topical drop anesthesia before and during surgery and adjustment means that the patients do not require systemic analgesia until after the adjustment process is completed. The extremely low incidence of nausea and the moderately common incidence of mild euphoria afterwards in the conscious sedation group are also important factors in allowing the patient to complete a successful secondary adjustment process.
From the values of the range and average of preoperative and postoperative deviations and the percent net change in deviation, it is clear that consciously sedated patients are just as able to cooperate with the secondary conscious topical anesthesia adjustment as the traditionally (generally) anesthetized patients are. However, the values for percent net change in the general anesthesia group might well have been better if we had waited 24 hours to perform adjustments in the patients in this group, as would traditionally be the case. However, we chose this methodology to determine if the drugs used in the conscious sedation group truly would allow earlier adjustment than the general anesthesia patients.
In this retrospective pilot study, our preliminary conclusions are that conscious sedation anesthesia is as safe and at least as effective as general anesthesia for adjustable suture strabismus repair. However, conscious sedation is better tolerated by the patients, allows earlier adjustment, and decreases time in the DCSU and the intensity of postoperative nursing care. We believe these results support a larger prospective study to evaluate more fully the benefits of each technique, firstly to the patient, and secondly to the planners and deliverers of cost-effective health care.
1. Bennett CR. Conscious Sedation in Dental Practice. St Louis, Mo: CV Mosby; 1974:14-22.
2. Jampolsky A. Transactions of the New Orleans Academy of Ophthalmology. 1978:321-349.
3. Wall PD. Introduction. In: Wall PD, Melzak R, eds. Textbook of Pain. New York, NY: Churchill, Livingston; 1984:1-16.
4. Henderson JA. Anesthesia for ambulatory surgery. In: Wetchler B, ed. Ambulatory Surgery: Past, Present and Future. 2nd ed. Philadelphia, Pa: JB Lippincott; 1990.
Time Taken for Primary Surgery and Total Time in DCSU
Frequency of Postoperative Pain and Nausea
Results of Treatment