Effect of different anaesthetic regimes on the oculocardiac reflex during paediatric strabismus surgery

Giuseppe Dagnini (1866-1928): Discoverer of the Trigemino-Cardiac Reflex and Practical Implications in Neurosurgery and Other Medical Specialties

The authors present the life and art of Giuseppe Dagnini, a renowned Italian physician who was born in Bologna in 1866. He was the chief of the Maggiore Hospital in Bologna and authored valuable scientific works on the trigemino-cardiac reflex which is still applied in modern clinical practice. Dr. Dagnini firstly described the reflex in 1908 postulating that stimulation of one of the 3 branches of the trigeminal nerve triggers the afferent pathway in lowering heart rate. The authors also provide a modern outlook on the clinical implications of the TCR in neurosurgery, neuroanesthesia, and other medical specialties.

The role of surgical factors eliciting oculocardiac reflex of patients undergoing orbital tumor surgery: a retrospective study

PURPOSE

Orbital tumors are an interdisciplinary disease, and surgery is one of the main treatment methods. The oculocardiac reflex (OCR) is a condition of surgery for orbital tumors. The aim of this study was to investigate whether there is an association between many surgical factors and the incidence of OCR in orbital tumor surgery.

METHODS

Comparisons were made between patients with and without OCR using the Mann-Whitney test, Fisher's exact test, and Chi-square test. When comparing multiple groups (groups > 2), to explain which two groups had differences, post hoc testing was used for analysis, and the differences between groups were judged according to the adjusted standardized residuals.

RESULTS

The results showed that the incidence of intraoperative OCR was different based on the different exposed operative field locations (p = 0.021). The OCR incidence in those with lesions involving the orbital apex and lesions adhering to extraocular muscles was higher than that of others (p < 0.001 and p = 0.003). In addition, multivariate logistic regression analysis revealed that orbital apex involvement and extraocular muscle adhesion were highly associated with a higher incidence of OCR (p < 0.001 and p = 0.013), while the operative field located in the lateral-superior orbit was highly associated with a lower incidence of OCR (p = 0.029).

CONCLUSION

In orbital tumor surgery under general anesthesia, lesions involving the orbital apex and lesion adhesion to the extraocular muscles were independent risk factors for OCR, and an operative field located in the lateral-superior orbit was a protective factor for OCR.

Comparing Effectiveness and Safety of Intravenous Atropine with Topical Tetracaine in Preventing and Relieving Oculocardiac Reflex in Patients Undergoing Strabismus Surgery: A Randomized Clinical Trial

Background

Oculocardiac reflex (OCR) is one of the serious complications following surgical therapeutic procedures for strabismus. Various medications have been tested to prevent or mitigate this complication. We aimed to compare the effect of intravenous atropine and topical tetracaine on the incidence and severity of OCR in strabismus surgery.

Materials and Methods

In this triple-blind randomized clinical trial study, 120 patients who were candidates for strabismus surgery were randomly assigned to receive intravenous atropine, topical tetracaine, or artificial tears as the control. The incidence of OCR and its severity along with the changes in hemodynamic conditions were compared across the groups.

Results

The incidence rate of OCR in the groups receiving atropine, tetracaine, and the control was found to be 17.5%, 25.0%, and 32.5% in the releasing phase without any difference, respectively (P = 0.303); however, it was 2.5%, 7.5%, and 25.0%, respectively, in the cutting phase, indicating a lower rate in the group receiving tetracaine (P = 0.004). Similarly, there was no difference in the severity of OCR across the three study groups in the releasing phase (P = 0.666); however, in the cutting phase, OCR was revealed to be milder in the group receiving atropine as compared to other groups (P = 0.033). Prescribing atropine led to higher mean systolic blood pressure and mean arterial pressure during surgery.

Conclusion

The injection of atropine can effectively reduce the incidence of OCR during strabismus surgery and reduce its severity if this reflex occurs.

Evaluation of the Perioperative Effects of Dexmedetomidine and Midazolam-Ketamine Premedication in Strabismus Surgery

PURPOSE

To evaluate the effects of intranasal dexmedetomidine and midazolam-ketamine combination for premedication on sedation quality, oculocardiac reflex development, mask tolerance, and separation from parents in children who would undergo strabismus surgery.

METHODS

A total of 74 patients aged 2 to 11 years, were divided into two groups. The dexmedetomidine group (n = 37) received 1 mcg/kg of dexmedetomidine and the midalozam-ketamine group (n = 37) received 0.1 mg/kg of midazolam and 7.5 mg/kg of ketamine combination intranasally. Mean arterial pressure, peripheral oxygen saturation, Ramsay Sedation Scale values, and heart rate were recorded before and after the premedication. The children's separation from the family scores were evaluated and recorded. The mask compliance was evaluated and recorded. Patients who developed oculocardiac reflex and were administered atropine were recorded. In the postoperative period, nausea and vomiting, recovery times, and postoperative agitation were evaluated.

RESULTS

Ramsay Sedation Scale scores, mask acceptance, and family separation scores were similar in both groups (P > .05). Oculocardiac reflex was observed more in the dexmedetomidine group (P = .048). Atro-pine requirement and postoperative nausea and vomiting rates were similar in both groups (P > .05). Mean arterial pressures and heart rates were significantly lower in the dexmedetomidine group during the pre-medication period. The recovery time was longer in the midazolam-ketamine group (P < .001). The incidence of postoperative agitation was significantly lower in the midazolam-ketamine group (P = .001).

CONCLUSIONS

The sedation efficacy of intranasal dexmedetomidine and midazolam-ketamine combination that were given in premedication was similar. Oculocardiac reflex was observed more with dexmedetomidine. The recovery time was prolonged in the midazolam-ketamine group, but postoperative agitation was observed less. [J Pediatr Ophthalmol Strabismus. 2023;60(6):427-434.].

Esketamine versus Sufentanil Applied Prior to Placement of Suspension Laryngoscope

OBJECTIVE

In laryngeal microsurgery, the insertion of the suspension laryngoscope is a strong stimulus that may cause hemodynamic fluctuations and adverse cardiovascular events. The purpose of this study was to compare the effect of preemptive treatment with esketamine and sufentanil on maintaining hemodynamics and reducing the occurrence of adverse cardiovascular events during the insertion of suspension laryngoscope.

METHODS

In this double-blind randomized controlled trial, patients undergoing general anesthesia for laryngeal microsurgery were randomly assigned (1:1) to esketamine 0.5 mg kg-1 (esketamine group) and sufentanyl 0.125 μg kg-1 (sufentanil group) before inserting the laryngoscope, respectively.

RESULTS

During the insertion of suspension laryngoscope, the incidence of bradycardia (HR < 60 beats/min) was 39.3% (22/56) in esketamine group, lower than 60.0% (33/55) in sufentanil group (odds ratio [OR], 2.32 [95% CI, 1.11-5.08]; p = 0.029). The incidence of hypotension (MAP <65 mmHg) was 33.9% (19/56) in esketamine group, lower than 56.4% (31/55) in sufentanil group (odds ratio [OR], 2.52 [95% CI, 1.91-5.27]; p = 0.018). The frequency of hypotension in esketamine group was lower than that in sufentanil group (0.36 ± 0.52 vs. 0.56 ± 0.50, p = 0.035). The time-weighted average of HR dropping above 30% of baseline was smaller in esketamine group than in sufentanil group (0.52 ± 2.06 vs. 1.08 ± 2.77, p = 0.006).

CONCLUSIONS

These findings showed that compared with preemptive treatment of sufentanil (0.125 μg kg-1 ), esketamine (0.5 mg kg-1 ) was effective in reducing the incidence of cardiovascular adverse events, including bradycardia and hypotension induced by the insertion of suspension laryngoscope during the laryngeal microsurgery.

LEVEL OF EVIDENCE

2 Laryngoscope, 133:3021-3027, 2023.

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.

Hydroxyzine Dihydrochloride Premedication Is a Necessity for Pediatric Patients Undergoing Strabismus Surgery: An Observational Prospective Clinical Trial

Objective

In this single-blind, observational prospective clinical trial, we aimed to determine and compare the effects of premedication with hydroxyzine plus midazolam and midazolam alone on the incidence of oculocardiac reflex (OCR).

Methods

Forty-five patients were divided into three groups. Group M received 0.5 mg/kg midazolam alone, Group H received 0.5 mg/kg hydroxyzine plus 0.5 mg/kg midazolam, and Group HM received 1 mg/kg hydroxyzine plus 0.5 mg/kg midazolam. The Ramsay Sedation Scale (RSS), the heart rates (HR1: after induction of anesthesia; HR2: before retraction of orbital muscle; and HR3: right after retraction of orbital muscle), the muscles with OCR, and the incidence of OCR (20% decrease of the HR right after the traction) were recorded and compared between the three groups.

Results

The mean HR1, HR2, and HR3 values were significantly increased (p=0.002, p < 0.001, p < 0.001) and the incidence of OCR (p=0.004) was significantly decreased in Group H and in Group HM (for all, p < 0.01) compared to Group M. The most common orbital muscle in which OCR occurred was the rectus medialis.

Conclusion

Premedication with a combination of 0.5 or 1 mg hydroxyzine with 0.5 mg midazolam significantly reduced the incidence of OCR compared to premedication with midazolam alone. This study was registered on https://clinicaltrials.gov/ with number NCT03806270.

Topical anaesthesia in strabismus surgery for Graves' orbitopathy: a comparative study of 111 patients

PURPOSE

To evaluate the tolerability and usability of topical anaesthesia in single rectus muscle recession for strabismus caused by Graves' orbitopathy (GO). To compare the perioperative pain score and surgical outcome between GO patients and non-GO patients.

METHODS

A retrospective comparative study of consecutive single rectus muscle recession performed under topical anaesthesia was carried out. All patients scheduled for one-stage single rectus muscle recession under topical anaesthesia were included. Numerical visual analogue pain score scale (NVAS) points, rates of motor success (horizontal deviation < 8 prism diopters (PD) and vertical deviation ≤ 6 PD) and sensory success (no diplopia without prisms), complications and postoperative adjustment frequencies were compared between GO and non-GO patients.

RESULTS

A total of 111 patients were included. The mean perioperative pain scores were 2.3 (SD ± 1.3) in GO and 1.6 (SD ± 1.1) in non-GO patients (p = 0.06 adjusted for gender). The postoperative mean alignments in GO and non-GO patients were 2 versus 3 PD horizontally and 1 versus 1 PD vertically respectively. Both motor and sensory success rates were 98% in GO patients and 94% versus 93% in non-GO patients. Adjustments as a second procedure the day after surgery was performed in 10% of the GO patients and 15% of the non-GO patients. The oculocardiac reflex was not triggered in any of the GO patients.

CONCLUSION

Topical anaesthesia in single muscle recession for GO is safe, well-tolerated and gives comparable surgical outcomes to those achieved in non-GO patients.

Profound trigeminocardiac reflex from lingual nerve stimulation: a case report

Trigeminocardiac reflex (TCR) is a well-known brainstem reflex that manifests as hypotension, bradycardia, dysrhythmia, and asystole when stimulation is applied to a branch of the trigeminal nerve. Most commonly associated with ophthalmic, orbital, and neurologic surgeries, mandibular division and oral cavity variants occur far less frequently. Here, we describe a case of asystolic TCR elicited by lingual nerve stimulation. This case highlights the role of specific anesthetic medications in modulating this phenomenon and reinforces the need for early recognition and clear communication in case of its occurrence. Anesthesia providers must consider discontinuing or avoiding certain medications when clinically appropriate, even during low TCR-risk procedures.

The association between surgical technique and oculocardiac reflex in pediatric strabismus surgery: an observational study

Background and objectives

The most common cause of oculocardiac reflex (OCR) is traction of the extraocular muscles. Therefore, strabismus surgery is highly risk for the development of this complication. This study aimed to investigate whether an association exists between the occurrence of OCR and the type of extraocular muscle manipulated during strabismus in a pediatric population.

Methods

A total of 53 pediatric patients who were operated for strabismus under sevoflurane anesthesia were enrolled in this prospective study. The association between surgical techniques and the occurrence of OCR was investigated.

Results

This study included 30 (56.6%) males and 23 (43.4%) females, with a mean age of 8.4 years. Overall, 83 eyes with 93 extraocular muscles were operated. Surgery was performed most frequently on the medial (44.6%) and lateral (36.1%) recti. OCR occurred in 33 (62.3%) patients. OCR was found to be significantly higher in the first operated muscle compared with the second muscle, regardless of muscle type, as identified in the statistical analysis based on the sequence of the operated muscles.

Conclusions

The manipulation of the first extraocular muscle has a higher risk of OCR in the pediatric population undergoing two-muscle surgery for strabismus.

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.

Trigeminocardiac Reflex Induced by Maxillary Nerve Stimulation during Sphenopalatine Ganglion Implantation: A Case Series

BACKGROUND

The trigeminocardiac reflex (TCR) is a brainstem reflex following stimulation of the trigeminal nerve, resulting in bradycardia, asystole and hypotension. It has been described in maxillofacial and craniofacial surgeries. This case series highlights TCR events occurring during sphenopalatine ganglion (SPJ) neurostimulator implantation as part of the Pathway CH-2 clinical trial "Sphenopalatine ganglion Stimulation for Treatment of Chronic Cluster Headache".

METHODS

This is a case series discussing sphenopalatine ganglion neurostimulator implantation in the pterygopalatine fossa as treatment for intractable cluster headaches. Eight cases are discussed with three demonstrating TCR events. All cases received remifentanil and desflurane for anesthetic maintenance.

RESULTS

Each patient with a TCR event experienced severe bradycardia. In two cases, TCR resolved with removal of the introducer, while the third case's TCR event resolved with both anticholinergic treatment and surgical stimulation cessation.

CONCLUSION

Each TCR event occurred before stimulation of the fixed introducer device, suggesting the cause for the TCR events was mechanical in origin. Due to heightened concern for further TCR events, all subsequent cases had pre-anesthesia external pacing pads placed. Resolution can occur with cessation of surgical manipulation and/or anticholinergic treatment. Management of TCR events requires communication between surgical teams and anesthesia providers, especially during sphenopalatine ganglion implantation when maxillary nerve stimulation is possible.

Differentiation of skin incision and laparoscopic trocar insertion via quantifying transient bradycardia measured by electrocardiogram

Most surgical procedures involve structures deeper than the skin. However, the difference in surgical noxious stimulation between skin incision and laparoscopic trocar insertion is unknown. By analyzing instantaneous heart rate (IHR) calculated from the electrocardiogram, in particular the transient bradycardia in response to surgical stimuli, this study investigates surgical noxious stimuli arising from skin incision and laparoscopic trocar insertion, and their difference. Thirty-five patients undergoing laparoscopic cholecystectomy were enrolled in this prospective observational study. Sequential surgical steps including umbilical skin incision (11 mm), umbilical trocar insertion (11 mm), xiphoid skin incision (5 mm), xiphoid trocar insertion (5 mm), subcostal skin incision (3 mm), and subcostal trocar insertion (3 mm) were investigated. IHR was derived from electrocardiography and calculated by the modern time-varying power spectrum. Similar to the classical heart rate variability analysis, the time-varying low frequency power (tvLF), time-varying high frequency power (tvHF), and tvLF-to-tvHF ratio (tvLHR) were calculated. Prediction probability (P_K) analysis and global pointwise F-test were used to compare the statistical performance between indices and the heart rate readings from the patient monitor. Analysis of IHR showed that surgical stimulus elicits a transient bradycardia, followed by the increase of heart rate. Transient bradycardia is more significant in trocar insertion than skin incision (p < 0.001 for tvHF). The IHR change quantifies differential responses to different surgical intensity. Serial P_K analysis demonstrates de-sensitization in skin incision, but not in laparoscopic trocar insertion. Quantitative indices present the transient bradycardia introduced by noxious stimulation. The results indicate different effects between skin incision and trocar insertion.

Sinus arrest with prolonged asystole due to the trigeminocardiac reflex during application of local anaesthetic in the nasal mucosa

The trigeminocardiac reflex (TCR) is defined as a sudden onset of parasympathetic dysrhythmias during stimulation of the trigeminal nerve. We describe a peripheral variation of TCR during manipulation of the nasal mucosa. A 42-year-old patient suffering from severe obstructive sleep apnoea was scheduled for surgical treatment. After inducted anaesthesia, the surgeon infiltrated the nasal mucosa with a local anaesthetic. The patient immediately showed an asystole and was treated with ephedrine and five chest compressions, despite spontaneous sinus rhythm return after ceasing of manipulation. Treatment with atropine established this TCR episode and ensured an event-free surgery.The authors present here, for the first time, a prolonged asystole caused by the TCR, triggered by minimal manipulation of the nasal mucosa. This severe manifestation of peripheral TCR demonstrates its importance in daily clinical business. This case was treated according to a modified treatment algorithm for all subtypes of TCR which is presented here.

Prospective evaluation of anesthetic protocols during pediatric ophthalmic surgery

PURPOSE

To date, no protocol of anesthesia for pediatric ophthalmic surgery is unanimously recognized. The primary anesthetic risks are associated with strabismus surgery, including oculocardiac reflex, postoperative nausea and vomiting, and postoperative pain.

METHODS

This was a prospective, monocentric, observational study conducted in a tertiary pediatric ophthalmic unit. Our anesthetic protocol for strabismus surgery included postoperative nausea and vomiting prevention using dexamethasone and ondansetron. No drug-based prevention of oculocardiac reflex or local/locoregional anesthesia was employed.

RESULTS

A total of 106 pediatric ophthalmic surgeries completed between November 2015 and May 2016 were analyzed. The mean patient age was 4.4 (range: 0.2-7.3, standard deviation: 2.4) years. Ambulatory rate was 90%. Oculocardiac reflex incidence was 65% during strabismus surgery (34/52), 50% during congenital cataract surgery (4/8), 33% during intramuscular injection of botulinum toxin (1/3), and 0% during other procedures. No asystole occurred. Postoperative nausea and vomiting incidence was 9.6% after strabismus surgery (5/52) and 0% following the other procedures. One child was hospitalized for one night because of persistent postoperative nausea and vomiting. Postoperative pain generally occurred early on in the recovery room and was quickly controlled. Its incidence was higher in patients who underwent strabismus surgery (27%) than in those who underwent other procedures (9%).

CONCLUSION

Morbidity associated with ophthalmic pediatric surgery is low and predominantly associated with strabismus surgery. The benefit-risk ratio and cost-effectiveness of oculocardiac reflex prevention should be questioned. Our postoperative nausea and vomiting rate is low, thanks to the use of a well-managed multimodal strategy. Early postoperative pain is usually well-treated but could probably be more effectively prevented.

Surgical factors affecting oculocardiac reflex during strabismus surgery

Background

To investigate surgical factors associated with the occurrence of oculocardiac reflex (OCR) and changes in heart rate (HR) during strabismus surgery.

Methods

Patients who underwent strabismus surgery under general anesthesia were enrolled in this study. The HR during surgery was measured at baseline, and at the following points during surgery: traction of the muscle, maximal increase after traction (adrenergic phase), and the cutting of the muscle. OCR was defined as an HR reduction of more than 20% at traction of the muscle, when compared to baseline HR. The HR at each stage during the surgery was compared between patients with and without OCR.

Results

A total of 162 operated muscles from 99 patients were enrolled. The incidence of OCR was 65% in patients. In patients with two muscle surgeries, there were significantly more OCRs in the first operated muscle than in the second operated muscle (p < 0.01). The difference in the decrease in HR in patients with OCR was significantly lower than that in patients without OCR at traction of the muscle, the adrenergic phase, and the cutting of the muscle (all, p < 0.01). The first operated muscle was a significant risk factor associated with the occurrence of OCR (OR = 3.95, p < 0.01).

Conclusion

The first operated muscle in patients with two muscle surgeries was a significant risk factor for OCR. Decreased HR at the traction of the muscle during surgery did not fully recover in patients with OCR.

Antagonistic and Synergistic Activation of Cardiovascular Vagal and Sympathetic Motor Outflows in Trigeminal Reflexes

The trigeminal nerve and heart are strongly related through somato-autonomic nervous reflexes that induce rapid changes in cardiovascular function. Several trigeminal reflexes have been described, but the diving and trigeminocardiac reflexes are the most studied. The heart is a target organ dually innervated by the sympathetic and parasympathetic systems. Thus, how cardiac function is regulated during the trigeminal reflexes is the result of the combination of an increased parasympathetic response and increased, decreased, or unaltered sympathetic activity. Various hemodynamic changes occur as a consequence of these alterations in autonomic tone. Often in the oxygen-conserving physiological reflexes such as the diving reflex, sympathetic/parasympathetic co-activation reduces the heart rate and either maintains or increases blood pressure. Conversely, in the trigeminocardiac reflex, bradycardia and hypotension due to parasympathetic activation and sympathetic inactivation tend to be observed. These sudden cardiac innervation disturbances may promote the generation of arrhythmias or myocardial ischemia during surgeries in the trigeminal territory. However, the function and mechanisms involved in the trigeminal reflexes remain to be fully elucidated. The current review provides a brief update and analysis of the features of these reflexes, with special focus on how the autonomic nervous system interacts with cardiovascular function.

The Effect of Sub-Tenon's Bupivacaine on Oculocardiac Reflex during Strabismus Surgery and Postoperative Pain: A Randomized Clinical Trial

PURPOSE

Oculocardiac reflex (OCR), defined as bradycardia induced by manipulation of extraocular muscles, is a serious complication during strabismus surgery for which prevention and proper management is required. In the present study, we investigated the efficacy of sub-Tenon injection of bupivacaine for prevention of OCR and postoperative pain.

METHODS

A prospective randomized controlled clinical trial was conducted. Fifty patients who were candidates for strabismus surgery were randomized into case (sub-Tenon's bupivacaine injection) or control (normal saline injection) groups. Standard strabismus surgery was performed for all cases. Occurrence and severity of OCR (primary outcome) and postoperative pain (using the Visual Analog Scale) were compared between the two groups.

RESULTS

Both incidence (32% vs. 100%; P = 0.002) and severity of OCR (mean heart rate decrease, 10.1 vs. 38.7 beats/minute; P < 0.001) were significantly lower in the study group compared to those in the control group. Postoperative pain scores were significantly lower in the case group than in the control group (mean score, 2.8 vs. 5.9 at 60 minutes after surgery; P < 0.001).

CONCLUSIONS

Sub-Tenon injection of bupivacaine as a local anesthetic can significantly prevent OCR and decrease the severity of bradycardia. This technique can also diminish postoperative pain in patients who underwent strabismus surgery.

The effect of anesthesia depth on the oculocardiac reflex in strabismus surgery

The aim of this study was to investigate the effect of the bispectral index (BIS) guided depth of anesthesia to inhibition of the oculocardiac reflex (OCR) during pediatric strabismus surgery. Patients between the ages of 3 and 16 years who were scheduled for elective strabismus surgery were randomly assigned to two groups. In Group 1 (n: 32), the BIS values of the patients were maintained at <50; in Group 2 (n: 28), the BIS values of the patients were maintained at levels greater than or equal to 50 with 4-7 % desflurane in a 50 % O₂-air mixture by titrating the concentration during the surgery. The heart rates, presence of dysrhythmia, anticholinergic drug usage and the type of the operated extra ocular muscle were recorded. The incidence of OCR was 25 % in Groups 1 and 64.3 % in Group 2, (p < 0.05). Moreover, the incidence of OCR in group 2 was higher in medial rectus (MR) traction (78.9 %) than in lateral rectus (LR) traction (33.3 %) (p = 0.035), with no significant difference in Group 1 between MR (21.1 %) and LR (26.7 %) tractions (p = 0.83). We found that the lower BIS values are associated with the lower incidence of OCR in pediatric patients undergoing strabismus surgery. And our findings confirmed that the deeper anesthesia has a protective effect against the OCR.

Anesthetic influence on occurrence and treatment of the trigemino-cardiac reflex: a systematic literature review

Trigeminocardiac reflex (TCR) is defined as sudden onset of parasympathetic dysrhythmia including hypotension, apnea, and gastric hypermotility during stimulation of any branches of the trigeminal nerve. Previous publications imply a relation between TCR and depth of anesthesia. To gain more detailed insights into this hypothesis, we performed a systematic literature review.Literature about occurrence of TCR was systematically identified through searching in Cochrane Central Register of Controlled Trials (CENTRAL), PubMed (MEDLINE), EMBASE (Ovid SP), and the Institute for Scientific Information (ISI Web of Sciences) databases until June 2013, as well as reference lists of articles for risk calculation. In this study, TCR was defined as drop in mean arterial blood pressure and heart rate, both >20% to baseline. We calculated intraoperative cerebral state index (CSI) of each TCR-case using a newly developed method. These data were further divided into 3 subgroups: CSI <40 (deep anesthesia), CSI 40-60 (regular anesthesia), and CSI >60 (slight anesthesia).Including 45 studies with 910 patients, 140 (15%) presented with TCR, and 770 (85%) without TCR during operation. TCR occurrence showed a 1.2-fold higher pooled risk slighter anesthesia (CSI <40: 13%, at CSI 40-60: 21%, and at CSI >60: 27%) compared with deeper anesthesia. In addition, we could discover a 1.3-fold higher pooled risk of higher MABP drop with a strong negative correlation (r = -0.935; r = 0.89) and a 4.5-fold higher pooled risk of asystole during TCR under slight anesthesia compared with deeper anesthesia.Our work is the first systematic review about TCR and demonstrates clear evidence for TCR occurrence and a more severe course of the TCR in slight anesthesia underlying the importance of skills in anesthesia management during skull base surgery. Furthermore, we have introduced a new standard method to calculate the depth of anesthesia.

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.

Effect of ketamine and midazolam on oculocardiac reflex in pediatric strabismus surgery

Background

The oculocardiac reflex (OCR) can be elicited during manipulation of the orbital structures in the strabismus correction surgery. A sinus bradycardia is the most common manifestation of OCR; and cardiac dysrhythmia and asystole may also occur. Various efforts to reduce OCR have been attempted, but without coherent outcome results.

Methods

Sixty one children, undergoing elective strabismus surgery, were randomly allocated into 2 groups: Group K received ketamine 1.0 mg/kg; and Group M received midazolam 0.15 mg/kg for induction of anesthesia. Anesthesia was maintained with 1-1.3 MAC of sevoflurane with 50% N₂O in O₂. Heart rate and blood pressure were measured 30 seconds before extraocular muscle (EOM) traction and immediately after traction. The OCR was defined as a decrease in heart rate more than 20% of the baseline heart rate, following manipulating EOM. Postoperative nausea and vomiting (PONV) and emergence agitation (EA) were assessed in postanesthetic care unit (PACU).

Results

Blood pressure before tightening EOM in Group K was higher than that in Group M (P < 0.05). However Δ HR (2.7 ± 15% vs. - 0.9 ± 16%) and incidence of OCR (10.0% vs. 19.4%) after traction an EOM were not different between the two groups. The occurrence of PONV (6.7 vs. 9.7%) and EA (30.0% vs. 22.6%) were similar.

Conclusions

Ketamine does not reduce the incidence of OCR compared with midazolam in pediatric strabismus surgery. In addition, ketamine does not increase the incidence of PONV and EA. In conclusion, it is reliable to use ketamine in pediatric strabismus surgery.

Anaesthetics differentially modulate the trigeminocardiac reflex excitatory synaptic pathway in the brainstem

The trigeminocardiac reflex (TCR) occurs upon excitation of the trigeminal nerve with a resulting bradycardia and hypotension. While several anaesthetics and analgesics have been reported to alter the incidence and strength of the TCR the mechanisms for this modulation are unclear. This study examines the mechanisms of action of ketamine, isoflurane and fentanyl on the synaptic TCR responses in both neurones in the spinal trigeminal interpolaris (Sp5I) nucleus and cardiac vagal neurones (CVNs) in the Nucleus Ambiguus (NA). Stimulation of trigeminal afferent fibres evoked an excitatory postsynaptic current (EPSC) in trigeminal neurones with a latency of 1.8 ± 0.1 ms, jitter of 625 μs, and peak amplitude of 239 ± 45 pA. Synaptic responses further downstream in the reflex pathway in the CVNs occurred with a latency of 12.1 ± 1.1 ms, jitter of 0.8-2 ms and amplitude of 57.8 ± 7.5 pA. The average conduction velocity to the Sp5I neurones was 0.94 ± 0.18 mm ms(-1) indicating a mixture of A-δ and C fibres. Stimulation-evoked EPSCs in both Sp5I and CVNs were completely blocked by AMPA/kainate and NMDA glutamatergic receptor antagonists. Ketamine (10 μm) inhibited the peak amplitude and duration in Sp5I as well as more distal synapses in the CVNs. Isoflurane (300 μm) significantly inhibited, while fentanyl (1 μm) significantly enhanced, EPSC amplitude and area in CVNs but had no effect on the responses in Sp5l neurones. These findings indicate glutamatergic excitatory synaptic pathways are critical in the TCR, and ketamine, isoflurane and fentanyl differentially alter the synaptic pathways via modulation of both AMPA/kainate and NMDA receptors at different synapses in the TCR.

Ketamine versus propofol for strabismus surgery in children

PURPOSE

To compare the effects of intravenous infusion of ketamine and propofol anesthesia in children undergoing strabismus surgery.

METHODS

Sixty pediatric patients aged 4-11 years were enrolled for the study. Patients in Group K were infused ketamine 1-3 mg/kg/hr (n = 30) and patients in Group P were infused with propofol 6-9 mg/kg/hr (n = 30). After giving fentanyl 1 mug/kg and rocuronium bromide 0.5 mg/kg, patients were intubated.

RESULTS

The consumption of anesthetics (P = 0.0001) and antiemetics (P = 0.004), the incidence of oculocardiac reflex (P = 0.02) in Group K were significantly lower than in Group P. The recovery time (P = 0.008), postoperative agitation score (P = 0.005), Face Pain Scale (P = 0.001), Ramsay Sedation Score (P = 0.01) during awakening and at postoperative 30th min (P = 0.02) in Group K were significantly lower than in Group P. The postoperative agitation score during awakening was significantly lower than the preoperative values in Group K (P = 0.0001).

CONCLUSIONS

The infusion of ketamine is more advantageous than the infusion of propofol in children for use in strabismus surgery.

Anesthetic management for pediatric strabismus surgery: Continuing professional development

PURPOSE

Strabismus surgery is one of the most common pediatric ophthalmic procedures. The purpose of this continuing professional development module is to update physicians on the anesthetic considerations of pediatric patients undergoing strabismus surgery.

PRINCIPAL FINDINGS

The preoperative assessment is important, as patients undergoing strabismus surgery may have an associated neuromuscular disorder, congenital syndrome, or cardiac disease. Malignant hyperthermia is no longer considered as being an issue associated with strabismus. The laryngeal mask airway is used frequently and has been shown as being associated with a low incidence of complications in strabismus surgery. The anesthesia technique can be adapted to decrease the incidence of the oculocardiac reflex and the oculorespiratory reflex, and the use of anticholinergic prophylaxis remains debatable. Since patients are at high risk for postoperative nausea and vomiting (PONV), combination anti-emetic therapy is recommended using dexamethasone and ondansetron. Metoclopramide was not found to provide additional benefit when combined with other anti-emetics. Droperidol is effective, but there remains a black box warning for dysrhythmias. Effective analgesics in this patient population include acetaminophen, nonsteroidal anti-inflammatory drugs, peribulbar blocks, and subtenon blocks. Topical tetracaine drops have demonstrated mixed results, and topical nonsteroidal anti-inflammatory drops were found not to be effective. The use of opioids should be minimized due to the increased incidence of PONV.

CONCLUSIONS

To provide optimal care for the pediatric patient undergoing strabismus surgery, it is important to understand the unique anesthetic considerations for strabismus surgery and to appreciate how each decision regarding the anesthetic technique can alter these considerations.

Coronary artery spasm occurring in the setting of the oculocardiac reflex

The oculocardiac reflex (OCR) occurs in up to 90% of ophthalmological surgeries. Several preventive and treatment strategies have been described. Coronary artery spasm (CAS) plays an important role in the pathogenesis of variant angina and myocardial infarction. We describe an unusual case of a perioperative myocardial infarction due to CAS that occurred in the setting of the treatment of the OCR. We offer insight aimed at minimizing the deleterious effects of the OCR and its management.

Incidence of postoperative nausea and vomiting after paediatric strabismus surgery with sevoflurane or remifentanil-sevoflurane

BACKGROUND

In this prospective, randomized, double-blind study, we evaluated and compared the incidence of postoperative nausea and vomiting (PONV) after paediatric strabismus surgery with two different anaesthetic methods, sevoflurane or remifentanil-sevoflurane.

METHODS

In total, 78 paediatric patients (aged 6-11 yr) undergoing strabismus surgery were enrolled and randomly assigned to two groups, sevoflurane (Group S) and remifentanil-sevoflurane (Group R). Anaesthesia was maintained with 2-3% sevoflurane in Group S (n=39) or with a continuous infusion of remifentanil combined with 1% sevoflurane in Group R (n=39), both using 50% N(2)O/O(2). Arterial pressure and heart rate before induction, after tracheal intubation, after skin incision, and at the end of surgery were recorded. The incidence of PONV in the post-anaesthesia care unit, the day surgery care unit, and at home 24 h after surgery was recorded.

RESULTS

Arterial pressure and heart rate were stable throughout the surgery, but were significantly lower in Group R than in Group S after tracheal intubation and skin incision. The incidence of PONV and postoperative vomiting was 17.9%/17.9% and 12.8%/10.2% (Group S/Group R) at the respective time points; values were comparable between the groups.

CONCLUSIONS

The incidence of PONV after paediatric strabismus surgery under sevoflurane anaesthesia was relatively low, and combining remifentanil with sevoflurane did not further increase the incidence.

Classification of potential risk factors for trigeminocardiac reflex in craniomaxillofacial surgery

PURPOSE

Trigeminocardiac reflex (TCR) in craniomaxillofacial surgery can lead to severely life-threatening situations. At least mild forms are probably much more common than the existing surgical literature suggests. Therefore, the aim of this presentation of cases and literature review was to evaluate the predisposing factors leading to a classification of risk factors for potential TCR and to give information concerning preventive measures and management procedures.

PATIENTS AND METHODS

All surgery reports from the Department of Cranio-Maxillofacial and Oral Surgery in the University Hospital in Zurich between 2003 and 2008 were searched for severe intraoperative cardiovascular complications, and a literature review was performed for publications concerning asystole or bradycardia during maxillofacial surgical procedures.

RESULTS

Three incidents were revealed in which severe bradycardia--in 2 cases followed by asystole--had occurred. All incidents were successfully managed.

CONCLUSION

All craniomaxillofacial surgeons involved in orbital surgery in general and in the treatment of midface fractures, eyelid surgery, and orthognathic procedures in particular should be aware of the possibility of the TCR and should be familiar with its prevention and therapy.

Influence of topical anesthetics on oculocardiac reflex and corneal healing in rabbits

AIM

To investigate the incidence of oculocardiac reflex (OCR) with two anesthetic regimens and its prevention using topical anesthetics in a rabbit model, and to explore the effect of topical anesthetics on corneal healing.

METHODS

Forty-eight clinically healthy adult New Zealand white rabbits of either sex were divided into two groups (Group A and B) and anesthetized with either ketamine (Group A, n =24) or propofol (Group B, n =24). he incidence of OCR was recorded in each group with a variety of ocular manipulation with or without the use of topical anesthetics (40g/L lignocaine, 5g/L proparacain, 5g/L bupivacaine). Corneal toxicity and healing following the use of each topical anesthetic was assessed one day after surgery and up to 7 days postoperatively by clinical examination of the eye, histopathology and collagen staining and transmission electron microscopy.

RESULTS

No incidence of OCR was recorded with ocular manipulation under ketamine anesthesia, whereas significant reduction in heart rate (P<0.01) was recorded under propofol anesthesia. Topical anesthetics could successfully prevent the OCR without affecting the corneal healing.

CONCLUSION

Topical anesthetics may be recommended for prevention of OCR without any local adverse effect.

Effect of different anesthetic agents on oculocardiac reflex in pediatric strabismus surgery

PURPOSE

The oculocardiac reflex (OCR) occurs frequently during pediatric strabismus surgery. The aim of this study was to assess the effects of various anesthetic regimens on the incidence of OCR during the surgery.

METHODS

Two hundred and eighty children, 1 to 9 years old, undergoing elective strabismus surgery, were randomly assigned to eight groups; ketamine-sevoflurane (KS), ketamine-desflurane (KD), ketamine-propofol (KP), ketamine-remifentanil (KR), midazolam-sevoflurane (MS), midazolam-desflurane (MD), midazolam-propofol (MP), and midazolam-remifentanil (MR). No premedication was given. Anesthesia was induced using ketamine 1 mg kg(-1) or midazolam 0.15 mg kg(-1) with 66% N(2)O in O(2). Laryngeal mask airways (LMAs) were placed with rocuronium 0.5 mg kg(-1). Anesthesia was maintained with sevoflurane 2-3 vol. %, desflurane 5-6 vol. %, propofol 7-8 mg kg(-1) h(-1), or remifentanil 0.75 microg kg(-1) over 1 min, followed by a continuous infusion of remifentanil 0.5 microg kg(-1) min(-1) with 66% N(2)O in O(2). Heart rate (HR) was recorded during extraocular muscle (EOM) manipulation. OCR was defined as a reduction in HR of more than 20% induced by the traction of an EOM.

RESULTS

In patients given ketamine, OCR occurred more frequently in the KP (65.7%) and KR (62.9%) groups than in the KD (29.4%) and KS (37.1%) groups (P < 0.05). In patients given midazolam, OCR occurred more frequently in the MP (54.3%) and MR (60.6%) groups than in the MD (36.4%) and MS (31.4%) groups (P < 0.05).

CONCLUSION

Propofol or remifentanil anesthesia was associated with a higher incidence of OCR during pediatric strabismus surgery than sevoflurane and desflurane anesthesia, when either ketamine or midazolam was used as an induction agent.

Effect of remifentanil on oculocardiac reflex in paediatric strabismus surgery

BACKGROUND

Rapidly acting narcotics enhance the degree of bradycardia due to the oculocardiac reflex (OCR) elicited by extraocular muscle (EOM) tension during strabismus surgery. We evaluated and compared the effects of remifentanil and sevoflurane on OCR during paediatric strabismus surgery.

METHODS

One hundred and twenty children, 1-9 years old, undergoing elective strabismus surgery, were randomly assigned to receive sevoflurane or remifentanil. No anticholinergic prophylaxis was administered. Anaesthesia was induced using ketamine 1.0 mg/kg or midazolam 0.15 mg/kg with 66% N(2)O in O(2). Laryngeal mask airways were placed with rocuronium 0.5 mg/kg. Anaesthesia was maintained with sevoflurane 2.0-3.0 vol% with 66% N(2)O in O(2) or remifentanil 0.75 mug/kg over 1 min and followed by the continuous infusion of remifentanil 0.5 mug/kg/min with 66% N(2)O in O(2). Heart rate (HR) and blood pressure (BP) were measured and compared. OCR was defined as a reduction in HR of >20% induced by traction of an EOM.

RESULTS

During anaesthesia, HR and BP were maintained at a lower level in the remifentanil group than in the sevoflurane group (each, P<0.05). The mean percent change in HR (-23.3+/-17.0% vs. -11.2+/-13.0%; P<0.05) and the incidence of OCR (58.3% vs. 28.3%; P<0.05) following traction of an EOM were higher in the remifentanil group than in the sevoflurane group.

CONCLUSIONS

Remifentanil enhanced the degree of bradycardia due to OCR as compared with sevoflurane during paediatric strabismus surgery.

Comparison of desflurane with sevoflurane for the incidence of oculocardiac reflex in children undergoing strabismus surgery

BACKGROUND

The oculocardiac reflex (OCR) is frequently observed during strabismus surgery. This study was designed to evaluate and compare the effect of sevoflurane and desflurane on the incidence of OCR.

METHODS

After obtaining Institutional Review Board approval and informed consent from parents, we enrolled 237 paediatric patients, aged 2-10 yr, undergoing strabismus surgery. No premedication was given. Anaesthesia was induced with thiopental and rocuronium. Patients were randomly allocated to one of the two anaesthetic regimens. Group S (n = 123) received sevoflurane and Group D (n = 114) received desflurane, both with 60% N2O/O2 for maintenance of anaesthesia. The OCR was defined as a > or = 20% decrease in heart rate (HR) from baseline values obtained immediately before muscle manipulation. If the HR did not increase after release of muscle tension, atropine 0.01 mg kg(-1) was administered.

RESULTS

There were no significant differences between the two groups in age, sex, body weight, and the number of muscles operated upon. The mean values of baseline HR were 123 (16) min(-1) in Group S and 121 (18) in Group D (NS). The minimum HR was 106 (22) min(-1) in Group S and 103 (21) in Group D (NS). There was no difference in the incidence of OCR between sevoflurane (26.0%) and desflurane (28.0%) anaesthesia.

CONCLUSIONS

Both agents can be used safely during strabismus surgery in paediatric patients.

Single bolus of intravenous ketamine for anesthetic induction decreases oculocardiac reflex in children undergoing strabismus surgery

BACKGROUND

Oculocardiac reflex (OCR) is a major complication of pediatric strabismus surgery. The aim of the present study was to determine whether a single bolus of intravenous (i.v.) ketamine for anesthetic induction can decrease OCR in children undergoing strabismus surgery.

METHODS

One hundred and twenty healthy children undergoing strabismus surgery were allocated to three groups using double-blind randomization. Anesthesia was induced with propofol 3 mg/kg in Group P, ketamine 1 mg/kg in Group K1, or ketamine 2 mg/kg in Group K2. Anesthesia was maintained with 3% sevoflurane in 50% N(2)O/O(2) in all patients. The baseline heart rate was obtained 30 s prior to the first traction of the extraocular muscle (EOM). OCR was defined as a development of arrhythmia or a decrease of more than 20% of the baseline heart rate during EOM traction.

RESULTS

The incidence of OCR was significantly lower in the ketamine groups (4/40 and 1/40 in Group K1 and K2, respectively) compared with the propofol group (14/40).

CONCLUSION

A single bolus of i.v. ketamine 1 or 2 mg/kg for anesthetic induction results in a lower incidence of OCR than propofol when combined with sevoflurane for maintenance in children undergoing strabismus surgery.

Combined propofol sedation with sub-Tenon's lidocaine/mercaine infusion for strabismus surgery in adults

AIMS

To evaluate the safety and efficacy of propofol sedation combined with sub-Tenon's anaesthesia for strabismus surgery in adults.

METHODS

Thirty-two consecutive patients aged 31-85 years underwent strabismus surgery under general (n=16) or local (n=16) anaesthesia. In the local anaesthesia (study) group, sedation was induced with a loading dose of midazolam, fentanyl, and propofol, followed by continuous infusion of propofol, 3-6 mg/k/h to deep sedation. A nasal tube was inserted to prevent airway obstruction. Sub-Tenon's anaesthesia included infusion of a 3-4 ml mixture (50 : 50) of lidocaine 2%/mercaine 0.5%. General anaesthesia consisted of premedication with midazolam, followed by fentanyl, esmeron-bromate, propofol, and tracheal intubation. Duration of surgery and anaesthesia, intraoperative oculocardiac reflex and arrhythmias, time to discharge, postoperative pain, nausea and vomiting, and patient and surgeon satisfaction were evaluated.

RESULTS

The local anaesthesia group had a significantly shorter operative and anaesthesia time, fewer episodes of oculocardiac reflex or arrythmia/bradycardia requiring treatment, fewer early or late episodes of nausea and vomiting, and less pain. The patients and surgeon in this group reported higher satisfaction.

CONCLUSION

Propofol sedation with local sub-Tenon's injection of lidocaine/mercaine is recommended for the induction and maintenance of anaesthesia during unilateral or bilateral strabismus surgery in adults. The method is quick and effective, without systemic or ocular side effects.

Muscle surgery in patients with Graves' disease using topical anesthesia

PURPOSE

To report our experience in extraocular muscle surgery for Graves' disease using topical anesthesia.

DESIGN

Retrospective, noncomparative, observational case series.

PARTICIPANTS

In 135 patients with Graves' disease, a total of 200 ocular muscles were operated during the past 20 years at the Department of Ophthalmology, Ludwig-Maximilian-University, Munich, Germany.

METHODS

Surgery was performed under topical anesthesia with tetracaine hydrochloride 1% eyedrops. Because of the restrictive nature of the motility impairment, recession of the muscles was used in all patients. The exact amount of recession was determined during the operation with active cooperation from the patient.

MAIN OUTCOME MEASURES

Binocular single vision and the angle of deviation were evaluated preoperatively and postoperatively.

RESULTS

Postoperative binocular single vision in the primary position was achieved by 78.7% of the patients on the first postoperative day. Subsequent evaluation demonstrated binocular single vision in 91.9% of all patients and in 96.4% of the group with only 1 muscle (inferior rectus) operated.

CONCLUSIONS

The authors have demonstrated that topical anesthesia is a feasible and reliable method for performing extraocular muscle surgery in patients with Graves' disease. Intraoperative patient discomfort seemed insignificant, and the active cooperation of the patient in finding the appropriate extent of surgery was advantageous. The overall results showed that deviation surgery with the use of topical anesthesia is highly successful in restoring binocular single vision in patients with endocrine orbitopathy.

Single-stage adjustable strabismus surgery for restrictive strabismus

PURPOSE

To evaluate the feasibility and stability of ocular alignment of single-stage adjustable strabismus surgery (SSASS) in restrictive strabismus.

METHODS

This was an observational case series comprising 12 patients with restrictive strabismus (mean age, 54.8 years) who were treated with SSASS using intravenous midazolam, fentanyl, and topical anesthesia. All were studied in a retrospective institutional manner. The refractive strabismus in 7 patients was caused by dysthyroid orbitopathy. Five patients had undergone previous ocular surgery, and 4 had undergone previous strabismus surgery. SSASS typically involved the vertical rectus muscles. Horizontal rectus muscles were adjusted when necessary. Silicon-treated polyester suture material (Ti-cron; United States Surgical, Norwalk, CT no longer available), 6-0, were used for inferior rectus recessions. Ocular alignment was set at ortho at the end of surgery and evaluated at 2 days, 6 weeks, and 3 months after surgery. The typical hang-back procedure was to lock the suture at the middle and edges of the tendon or muscle at the intended disinsertion point. The tendon was then disinserted and hung back from the original insertion with adjustments until the desired position (ortho) and single vision were attained.

RESULTS

All patients remained comfortable throughout surgery and had no significant postoperative discomfort. All patients except 2 (16.6%) maintained satisfactory vertical alignment (<2 prism diopters). These 2 patients with dysthyroid orbitopathy had progressive overcorrection after inferior rectus recession.

CONCLUSIONS

SSASS, using intravenous midazolam, fentanyl, and topical anesthesia, is a safe and precise alternative treatment for patients with restrictive strabismus including those with dysthyroid orbitopathy.