The intraoperative oculocardiac reflex as a predictor of postoperative vaso-vagal responses during adjustable suture surgery

Surgical and anesthetic influences of the oculocardiac reflex in adults and children during strabismus surgery

One of the most common untoward occurrences during strabismus surgery at all ages is the oculocardiac reflex. Although typically easily treated, the sudden bradycardia or cardiac arrest may add a few gray hairs to ophthalmologists and anesthesiologists alike as it can be potentially fatal. This updated review of the literature and novel detailed treatment algorithm may prevent patient morbidity and mortality through proper recognition of at-risk patients and rapid treatment through proper communication between surgical and anesthesia physicians/providers.

Effect of Ice Slush on Reducing the Oculocardiac Reflex During Strabismus Surgery

BACKGROUND

The aim of this study was to explore whether ice slush (IS) causing local hypothermia can effectively inhibit the oculocardiac reflex (OCR) during strabismus surgery.

METHODS

This prospective, randomized, double-blind study included 58 patients with concomitant strabismus scheduled for lateral rectus (LR) recession under general anesthesia. Patients were randomly allocated to receive IS (IS group) or standard treatment (control group) with sterile saline at room temperature before surgery. OCR was defined as a sudden decrease in heart rate (HR) of >15% from baseline. If one incidence of the OCR was found in 1 patient in any stage (0/I/II/III), the patient was defined as an OCR responder, and the incidence of overall OCR was the incidence of OCR responders. The primary outcome was the incidence of overall OCR during all stages of the surgery, which was analyzed by the Z test and computed based on the absolute risk difference with 2-sided 95% confidence intervals (CIs) using the Newcombe method.

RESULTS

The overall OCR occurred in 19 of 29 patients (62.5% [95% CI, 45.7-82.1]) in the IS group and 28 of 29 patients (96.6% [95% CI, 82.2-99.9]) in the control group (absolute risk difference, -31.0% [95% CI, -49.4 to -11.0]; Z test, P < .001), which demonstrated that the incidence of overall OCR in IS group was significantly lower than that in the control group.

CONCLUSIONS

IS on the ocular surface causing local hypothermia is a promising and easily accessible method to reduce the overall OCR, which can improve the safety of strabismus surgery.

The Oculocardiac Reflex: A Review

BACKGROUND

A typical oculocardiac reflex (OCR) is a moderate trigemino-vagal bradycardia elicited by tension on an extraocular muscle (EOM) during strabismus surgery; however, many other orbital stimuli can elicit cardiac slowing including retinopathy of prematurity examination.

METHODS

World literature related to trigeminovagal and oculocardiac reflex covering over 15,000 patients including 51 randomized clinical trials and case reports are analyzed and reviewed. Under an ongoing observational trial in Alaska, anesthetic, patient and surgical influences on routine strabismus surgery using prospective, uniform EOM tension are compared seeking sufficient sample size to characterize this individually widely variable cardiac response.

RESULTS

With adequate sample size, and emphasizing clinical studies controlling type of EOM, muscle tension amount and duration, anticholinergic and opioid medications, the following augment OCR; rapid-acting opioids and dexmedetomidine while OCR is reduced in older patients, the right eye, less EOM tension, deeper inhaled agents, hypocarbia, anticholinergic medications and orbital block. In re-operations, the former are relatively poor predictors of subsequent OCR.

CONCLUSION

Profound bradycardia can occur in almost 10% of strabismus surgery cases without anticholinergic preventive measures, but reliable prediction of OCR remains elusive. With foreknowledge and careful anesthetic monitoring of the patient before EOM manipulation, residual adverse sequelae from OCR are fortunately very rare. Despite well over a century of experience, the teleology for this occasionally dramatic cardiac response to eye surgery is still not known.

Quantitative measurement of passive duction force tension in intermittent exotropia and its clinical implications

PURPOSE

To evaluate the passive duction force (PDF) in extraocular muscles (EOMs) in patients with intermittent exotropia (IXT) using a quantitative tension-measuring device.

METHODS

This prospective, case-control study enrolled 25 patients with IXT and 26 age- and sex-matched controls. PDF was measured under general anesthesia as the eyeball was rotated medially or laterally away from the direction of the force being tested. The preferred eye for fixation was determined using a cover-uncover test.

RESULTS

The PDF in the IXT and control groups were 60.9 g and 52.1 g, respectively, for the lateral rectus (LR) (p = 0.046) and 53.0 g and 48.8 g for the medial rectus (MR) (p = 0.293). When the eyes were examined separately in the IXT group, the PDF of LR was larger in the nonpreferred eye for fixation than in the control group (p = 0.039), whereas there was no difference in the preferred eye for fixation (p = 0.216). Additionally, the relative PDF of LR in the nonpreferred eye compared to the ipsilateral PDF of MR was positively associated with the duration of manifest deviation (p = 0.042) and the average angle of the near and far deviations (p = 0.023).

CONCLUSIONS

The PDF in the LR in patients with IXT in the nonpreferred eye for fixation was larger than normal and could increase with the duration of manifest deviation and the angle of deviation. Evaluating the PDF in EOMs could provide information that is useful for managing strabismus and understanding its pathophysiology.

New instrument for quantitative measurements of passive duction forces and its clinical implications

PURPOSE

Evaluating the passive duction force of the extraocular muscles is important for the diagnosis of and surgical planning for strabismus. This is especially relevant in patients with an observable limitation of duction movement. The purpose of this study was to validate passive duction forces in healthy subjects using a novel instrument.

METHODS

An instrument for making continuous quantitative measurements of passive duction forces was designed. Tension was measured as the eyeball was rotated horizontally or vertically from the resting position under general anesthesia 10 mm (50°) away from the direction of force to be tested (opposite side).

RESULTS

Seventy eyes of 35 subjects were enrolled in this study (age range of 4-80 years and mean age of 36.3 years). The passive duction force was measured at 49.0 ± 15.3 g (mean ± standard deviation) for medial rotation, 44.8 ± 13.2 g for lateral rotation, 50.5 ± 14.8 g for superior rotation, and 53.5 ± 13.8 g for inferior rotation. The passive duction forces were similar for all gaze positions, but it was larger for inferior rotation than for lateral rotation (P = 0.009). The passive duction force was significantly larger for vertical rotation (51.9 ± 14.4 g) than for horizontal rotation (46.9 ± 14.4 g) (P = 0.006). The passive duction force did not differ significantly with sex (P = 0.355), side (P = 0.087), or age (P = 0.872).

CONCLUSIONS

These measurements of passive duction forces in a healthy population provide valuable information for diagnosing specific strabismic problems and could be useful for increasing the precision of strabismus surgery. Graphical abstract.

Incidence and ramifications of the oculocardiac reflex during the orbitozygomatic approach: a prospective assessment

OBJECTIVE

The oculocardiac reflex (OCR) is a sudden decrease in heart rate resulting from mechanical manipulation of the orbit, especially due to traction on the orbital contents. The purpose of this study was to determine the incidence and clinical ramifications of OCR elicitation by the orbitozygomatic (OZ) approach.

METHODS

Electrocardiographic strips were collected prospectively from 104 patients undergoing OZ approaches. Recording was started at the commencement of the craniotomy cuts and was stopped after completion of the OZ osteotomy. Each recording was divided into stage 1, which encompassed the time between the start of the craniotomy cuts to the commencement of the osteotomy cuts, and stage 2, which encompassed the time from commencement of osteotomy cuts until completion of all bone work and dural tacking Orbital manipulation occurred exclusively during stage 2. A decrease in heart rate of 10 bpm or more between stage 1 and stage 2 was recorded as an OCR event.

RESULTS

In our 104 patients we detected OCR events 31.7% of the time. There was no significant difference in rate of OCR occurrence found in analysis of the covariates of hypertension, hyperlidemia, diabetes mellitus, hypothyroidism/hyperthyroidism, β-blocker use, calcium channel blocker use, or tobacco use. In each case, transient cessation of orbital manipulation was sufficient to normalize heart rate. No patients required anticholinergic intervention as a result of OCR, and there were no postoperative ramifications of the OCR.

CONCLUSIONS

OCR occurs in nearly one-third of patients who undergo the OZ approach. However, simple cessation of orbital manipulation is sufficient to normalize the patient's heart rate. Rarely is medical management required or does there appear to be any significant postoperative ramifications.

Adjustable suture strabismus surgery

Surgical management of strabismus remains a challenge because surgical success rates, short-term and long-term, are not ideal. Adjustable suture strabismus surgery has been available for decades as a tool to potentially enhance the surgical outcomes. Intellectually, it seems logical that having a second chance to improve the outcome of a strabismus procedure should increase the overall success rate and reduce the reoperation rate. Yet, adjustable suture surgery has not gained universal acceptance, partly because Level 1 evidence of its advantages is lacking, and partly because the learning curve for accurate decision making during suture adjustment may span a decade or more. In this review we describe the indications, techniques, and published results of adjustable suture surgery. We will discuss the option of 'no adjustment' in cases with satisfactory alignment with emphasis on recent advances allowing for delayed adjustment. The use of adjustable sutures in special circumstances will also be reviewed. Consistently improved outcomes in the adjustable arm of nearly all retrospective studies support the advantage of the adjustable option, and strabismus surgeons are advised to become facile in the application of this approach.

Adjustment in patients with asystole during strabismus surgery

PURPOSE

To investigate whether patients who developed asystole during strabismus surgery under general anesthesia also develop asystole during adjustment, and whether adjustment can safely be performed under topical anesthesia in these patients.

DESIGN

Retrospective, noncomparative interventional case series.

METHODS

Adjustment was performed with topical anesthesia in four patients aged 28, 32, 50, and 53 years who exhibited asystole during strabismus surgery under general anesthesia. Blood pressure and electrocardiogram were monitored during the adjustment.

RESULTS

Adjustment was successfully completed in all patients without asystole. Two patients showed oculocardiac reflex (OCR), with a reduction in heart rate (HR) >20% of the baseline value. One of these patients exhibited severe OCR that developed when the patient's posture was changed from the supine to the sitting position for measurement of the angle of strabismus after adjustment, and again during conjunctival manipulation after conjunctival closure. No patient required atropine.

CONCLUSIONS

Adjustment can safely be performed under topical anesthesia in patients who developed asystole during strabismus surgery under general anesthesia.

Adjustable sutures in children using a modified technique

PURPOSE

Adjustable-suture techniques are commonly used to decrease the reoperation rate in adults undergoing strabismus surgery, but they are infrequently used in children because of the difficulty of performing adjustments on a conscious child. The purpose of this study is to evaluate a new technique for using adjustable sutures in children, which makes the second stage of the procedure unnecessary if no adjustment is needed.

METHODS

This was a retrospective study of children who underwent surgery for exotropia or esotropia. The technique used was a variation of the standard fornix-based adjustable suture with a separate slipknot. The pole sutures were buried within the sclera and tied; then the incision of the conjunctiva was closed to cover the adjustable sutures. The patients were then measured 4 to 6 hours after the initial surgery. The decision of whether to adjust was based on predetermined criteria. Those children not adjusted were discharged with no further manipulation needed because the conjunctiva was already closed. For those children who were adjusted, the adjustment was made with the patient under intravenous propofol sedation or laryngeal mask anesthesia.

RESULTS

A total of 61 consecutive children ages 12 months to 14 years underwent surgery using this technique. Patients were followed-up after surgery for a minimum of 6 weeks (median 19.4). Fifty-four of the 61 patients (88%) were within 10 prism diopters (PD) of orthophoria on their final postoperative visit. Of the 22 patients who underwent an adjustment, 20 (91%) were within 10 PD of orthophoria at their final postoperative visit. The median follow-up was 19.4 weeks (range 6 to 45.9).

CONCLUSIONS

This new adjustable-suture technique was associated with excellent short-term eye alignment. It is particularly suited for pediatric surgery because it eliminates the necessity of further manipulation of children who do not require adjustment.

Oculocardiac reflex in sedated patients having laser in situ keratomileusis

PURPOSE

To eliminate stress as a variable in assessing the frequency of the oculocardiac reflex during laser in situ keratomileusis (LASIK).

SETTING

Merida Ophthalmological Hospital and Oftalmedica, Mexico City, Mexico.

METHODS

A pulse oximeter registered the heart rate of 30 sedated patients having LASIK. Sedation was accomplished with a combination of midazolam and fentanyl. The heart rate was noted before and during suction. The results in 1 eye of each patient were recorded. Oculocardiac reflex was defined as a decrease of 10% or more of the basal heart rate.

RESULTS

Fourteen patients (46.7%) had a 10% or more decrease in heart rate when suction was applied. Ten of the 14 had a decrease in heart rate between 10% and 19%, 3 between 20% and 29%, and 1 of more than 30%. Two patients (6.6%) had an increase in the basal heart rate of more than 10%.

CONCLUSIONS

The findings suggest that the oculocardiac reflex occurs more frequently in sedated patients than in nonsedated patients.

The association between the oculocardiac reflex and post-operative vomiting in children undergoing strabismus surgery

The oculocardiac reflex (OCR) is a potentially serious complication of ophthalmic surgery which is most commonly elicited during paediatric strabismus surgery. Post-operative vomiting (POV) is also extremely common after such procedures and may result in admission following planned day-case surgery. Although many factors play a part in the occurrence of POV, stimulation of the trigemino-vagal reflex arc is thought to explain the particularly high rate of vomiting after strabismus surgery. The OCR and the vaso-vagal response share this neuronal pathway, the bradycardia of the OCR often being the only objective feature of the vaso-vagal response while the patient is anaesthetised. The aim of this study was to investigate the possible association between the occurrence of the OCR and subsequent POV in children undergoing strabismus surgery. We have studied this relationship in 79 children, aged between 1 and 13 years, undergoing strabismus surgery under standardised anaesthetic conditions. A positive OCR was regarded as a drop in heart rate of 10% or more, or the onset of a dysrhythmia. An intraoperative OCR was elicited in 51 (64.6%) of the 79 children, whilst 29 (36.7%) developed POV in the subsequent 24 h period. There was a significant association between a positive intraoperative OCR and POV (p = 0.01): children with a positive OCR were 2.6 times more likely to vomit than those without the reflex. We conclude that there is an association between the occurrence of the OCR and POV and discuss possible preventive strategies.

Clinical characteristics of surgically treated adult strabismus

BACKGROUND

Strabismus is present in approximately 4% of the population with most forms becoming clinically evident in infancy and childhood. Adult strabismus, including that resulting from recurrent childhood deviations, varies in etiology, presentation, symptomatology, and response to treatment. This report is intended to prospectively characterize adults who required surgical correction of their strabismic deviation.

METHODS

Beginning in 1991, a prospective computerized database was collected that contained all clinical, laboratory, and surgical information on the adult ocular motility service at the Scheie Eye Institute and The Children's Hospital of Philadelphia (Philadelphia, Pa). Analysis of those patients who underwent surgical correction of their strabismus is included in this report. Demography, clinical characteristics, and surgical procedures including results were analyzed separately in adults with their strabismus beginning before visual maturation (BVM) (9 years of age) and after visual maturation (AVM).

RESULTS

A minimum of 6 months and average of 1.8 years follow up is reported on 262 procedures in 255 patients with an average age of 37 between January 1991 and January 1996. Sixty-two percent of patients had their strabismus onset BVM. Fifty-one percent of BVM patients and 80% of AVM patients had incomitant deviations. Adjustable suture surgery was performed on 97% of all patients, with 28% of BVM and 57% of AVM patients having multiplanar surgery. Successful motor alignment was achieved in 85% of all patients after one surgical procedure. Sensory success was achieved in 81% of all AVM patients and 25% of all BVM patients. Subjective success was 94% in both groups of patients.

CONCLUSIONS

Numerous differences exist between childhood and adult strabismus characteristics and response to surgery. Although strabismus surgery is effective, differences in results reflect the varied physiology regarding etiology, pathophysiology, and symptomology. Classification into AVM and BVM groups will provide continued clarity for future studies.

The use of propofol and mivacurium anesthetic technique for the immediate postoperative adjustment of sutures in strabismus surgery

PURPOSE

Adjustable suture techniques have become increasingly popular over the last decade and may reduce the re-operation rate after strabismus surgery. The adjustment usually is made in the hospital or office 5 to 24 hours after surgery, when the patient has fully recovered from general anesthesia. The ability to perform suture adjustment in the operating room, immediately after completion of surgery, would be an attractive alternative with respect to patient monitoring, sterility, comfort, and timing. The purpose of this study is to compare the alignment of patients in the operating room adjusted immediately after surgery with their alignment the morning after surgery.

METHODS

Patients with strabismus who have good vision in each eye and who were judged to be appropriate candidates for adjustable sutures were invited to enroll in a study using propofol and mivacurium total intravenous anesthetic technique. Patients underwent strabismus surgery in which one or more muscles were placed on adjustable sutures. Immediately after extubation, these patients were awakened in the operating room, assisted in sitting upright, and asked to fixate on a 20/400 Snellen E target on the operating room wall. Sutures were adjusted, when necessary, to obtain the desired postoperative alignment. Prism and alternate cover measurements, taken after the sutures were permanently tied, were compared with measurements taken the morning after surgery.

RESULTS

Twenty-nine patients qualified for inclusion. Measurements of horizontal and vertical alignment in the operating room were all within 12 prism diopters (PD) of the measurements taken 18 to 24 hours after surgery (mean variation, 4 PD horizontally and 2 PD diopters vertically). The measured deviation changed less than or equal to 6 PD horizontally in 78% of patients and less than or equal to 3 PD vertically in 70% of patients.

CONCLUSION

For some adult patients with strabismus, a total intravenous general anesthesia technique using an infusion of propofol and mivacurium may provide the opportunity for accurate suture adjustment in the operating room, immediately after completion of surgery.

The use of hyaluronic acid during adjustable suture surgery

We prospectively studied the force required to move an extraocular muscle after adjustable suture surgery with and without the perioperative use of hyaluronic acid (Healon). The 15 muscles that received hyaluronic acid averaged 15.0 g of force to move the muscle 2.0 mm which was significantly different than the average force of 36.15 g required for the 13 control muscles. The decreased force required to adjust the muscle along with potential antiinflammatory properties of hyaluronic acid make this a useful adjunct during adjustable suture surgery.