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.     

A modality-specific somatosensory evoked potential test protocol for clinical evaluation: A feasibility study

ObjectiveWe aimed to establish an objective neurophysiological test protocol that can be used to assess the somatosensory nervous system.MethodsIn order to assess most fiber subtypes of the somatosensory nervous system, repetitive stimuli of seven different modalities (touch, vibration, pinprick, cold, contact heat, laser, and warmth) were synchronized with the electroencephalogram (EEG) and applied on the cheek and dorsum of the hand and dorsum of the foot in 21 healthy subjects and three polyneuropathy (PNP) patients. Latencies and amplitudes of the modalities were assessed and compared. Patients received quantitative sensory testing (QST) as reference.ResultsWe found reproducible evoked potentials recordings for touch, vibration, pinprick, contact-heat, and laser stimuli. The recording of warm-evoked potentials was challenging in young healthy subjects and not applicable in patients. Latencies were shortest within Aβ-fiber-mediated signals and longest within C-fibers. The test protocol detected function loss within the Aβ-fiber and Aδ-fiber-range in PNP patients. This function loss corresponded with QST findings.ConclusionIn this pilot study, we developed a neurophysiological test protocol that can specifically assess most of the somatosensory modalities. Despite technical challenges, initial patient data appear promising regarding a possible future clinical application.SignificanceEstablished and custom-made stimulators were combined to assess different fiber subtypes of the somatosensory nervous system using modality-specific evoked potentials.     

头脉冲试验与头脉冲抑制试验参数相关性分析

目的验证头脉冲试验（HIMP）和头脉冲抑制试验（SHIMP）在前庭眼动反射中的互补效应。方法选择前庭上神经炎患者33例，健康成人10例（20耳），对前庭上神经炎患者患侧和健康成人左右侧HIMP和SHIMP增益、扫视潜伏期、扫视波振幅及显性扫视产生百分比进行匹配分析，比较HIMP和SHIMP各项参数之间相互关系。结果HIMP增益与SHIMP增益呈线性正相关，并且HIMP增益大于SHIMP增益，差异具有统计学意义（t=5.890，r=0.956，P均=0.000）。HIMP潜伏期大于SHIMP潜伏期，差异具有统计学意义（t=-3.360，P=0.001），但无相关性（r=0.180，P=0.196）。HIMP扫视振幅与SHIMP扫视振幅呈负相关（r=-0.484，P=0.000），HIMP扫视百分比与SHIMP显性扫视百分比呈负相关（r=-0.604，P=0.000）。HIMP增益与HIMP扫视潜伏期、振幅及百分比均呈负相关，且均具有统计学意义（P＜0.05）。SHIMP增益与SHIMP代偿性扫视振幅及百分比呈正相关，具有统计学意义（P＜0.05）。SHIMP增益与SHIMP扫视潜伏期无相关性（r=-0.044，P=0.756）。结论SHIMP和HIMP均可检查水平性角前庭眼动反射（VOR）的直接通路，代偿性扫视和反代偿性扫视的增益、振幅和扫视产生的百分比可作为动态观察指标评估前庭功能。两者参数变化对评估VOR通路的损伤和恢复情况起到一定指导意义。     

General anaesthesia for ophthalmic surgery

The majority of ophthalmic surgeries are performed as day cases under topical or regional anaesthesia with or without intravenous sedation. However, general anaesthesia is necessary in certain circumstances e.g. local anaesthetic allergy or patients who are unable to cooperate or to lie flat or still. Patients for ophthalmic surgery are frequently elderly with multiple comorbidities, such as diabetes and hypertension. Patients with rare genetic syndromes may present for eye surgery. Therefore adequate preoperative evaluation and preparation will minimize perioperative complications. The goals of general anaesthesia are smooth induction and emergence, with stable intra-ocular pressure (IOP) and akinesia of the globe. These can be achieved with a combination of intravenous and inhalational agents with or without muscle relaxants and opiates. Use of the laryngeal mask airway has the advantage of causing a smaller rise in IOP on insertion and less coughing on emergence. Total intravenous anaesthesia with propofol and remifentanil has the advantages of causing less postoperative nausea and vomiting (PONV), reduced stress response to airway intervention, rapid recovery and smooth emergence. Some eye procedures require special consideration, for example, strabismus and vitreoretinal surgery involves traction of the rectus muscles producing a higher incidence of oculocardiac reflex and PONV. Most ophthalmic surgery produces mild to moderate pain amenable to non-opioid analgesics. Intraoperative topical and regional anaesthesia reduce postoperative pain and opiate requirement. Open globe injury and a full stomach present unique challenges to prevent increase in IOP as well as protecting the airway.     

Predictive value of intraoperative blink reflex monitoring for surgical outcome during microvascular decompression for hemifacial spasm

ObjectiveTo investigate the prognostic and predictive value of intraoperative blink reflex (BR) monitoring during microvascular decompression (MVD) for hemifacial spasm (HFS).MethodsWe retrospectively reviewed 41 patients with HFS undergoing MVD with intraoperative BR and lateral spread response (LSR) monitoring. Facial spasm was evaluated for six months postoperatively.ResultsThe BR resolved in 38 patients and persisted in three after MVD. For patients who exhibited BR resolution, 1-day, 1-month, and 6-month follow-ups revealed that 35 (92.1%), 35 (92.1%), and 38 (100%) patients had spasm resolution, respectively. However, of the three patients with persistent BR, one (33.3%), one (33.3%), and zero (0%) patients exhibited spasm resolution at the three corresponding follow-ups. We found a statistically significant difference in spasm resolution between the persistent and resolved BR groups at six months postoperatively. A comparison between intraoperative BR and LSR monitoring revealed that BR was a better predictor of clinical outcomes.ConclusionsIntraoperative BR monitoring is a potentially useful tool to help facilitate an adequate decompression and is a reliable prognostic predictor of surgical outcome.SignificanceThis study is the first to document the relationship between intraoperative BR monitoring and surgical outcome in patients with HFS.     

EMG breakthrough during cortical silent period in congenital hemiparesis: a descriptive case series

BackgroundThe cortical silent period is a transient suppression of electromyographic activity after a transcranial magnetic stimulation pulse, attributed to spinal and supraspinal inhibitory mechanisms. Electromyographic breakthrough activity has been observed in healthy adults as a result of a spinal reflex response within the cortical silent period.ObjectivesThe objective of this case series is to report the ipsilesional and contralesional cortical silent period and the electromyographic breakthrough activity of 7 children with congenital hemiparesis.MethodsTMS was delivered over the ipsilesional and contralesional primary motor cortices with resting motor threshold and cortical silent period measures recorded from first dorsal interosseous muscle.ResultsSeven children (13 ± 2 years) were included. Ipsilesional and contralesional resting motor thresholds ranged from 49 to 80% and from 38 to 63% of maximum stimulator output, respectively. Ipsilesional (n = 4) and contralesional (n = 7) cortical silent period duration ranged from 49 to 206 ms and 81 to 150 ms, respectively. Electromyographic breakthrough activity was observed ipsilesionally in 3/4 (75%) and contralesionally in 3/7 (42.8%) participants. In the 3 children with ipsilesional breakthrough activity during the cortical silent period, all testing trials showed breakthrough. Contralesional breakthrough activity was observed in only one of the analyzable trials in each of those 3 participants. The mean peak amplitude of breakthrough activity ranged from 45 to 214 μV (ipsilesional) and from 23 to 93 μV (contralesional).ConclusionFurther research is warranted to understand the mechanisms and significance of electromyographic breakthrough activity within the cortical silent period in congenital hemiparesis. Understanding these mechanisms may lead to the design of tailored neuromodulation interventions for physical rehabilitation.Trial registrationNCT02250092 (https://clinicaltrials.gov/ct2/show/NCT02250092)     

Expression and effect of sodium-potassium-chloride cotransporter on dorsal root ganglion neurons in a rat model of chronic constriction injury

Sodium-potassium-chloride cotransporter 1 (NKCC1) and potassium-chloride cotransporter 2 (KCC2) are associated with the transmission of peripheral pain.We investigated whether the increase of NKCC1 and KCC2 is associated with peripheral pain transmission in dorsal root ganglion neurons.To this aim,rats with persistent hyperalgesia were randomly divided into four groups.Rats in the control group received no treatment,and the rat sciatic nerve was only exposed in the sham group.Rats in the chronic constriction injury group were established into chronic constriction injury models by ligating sciatic nerve and rats were given bumetanide,an inhibitor of NKCC1,based on chronic constriction injury modeling in the chronic constriction injury + bumetanide group.In the experiment measuring thermal withdrawal latency,bumetanide (15 mg/kg) was intravenously administered.In the patch clamp experiment,bumetanide (10 μg/μL) and acutely isolated dorsal root ganglion neurons (on day 14) were incubated for 1 hour,or bumetanide (5 μg/μL) was intrathecally injected.The Hargreaves test was conducted to detect changes in thermal hyperalgesia in rats.We found that the thermal withdrawal latency of rats was significantly decreased on days 7,14,and 21 after model establishment.After intravenous injection of bumetanide,the reduction in thermal retraction latency caused by model establishment was significantly inhibited.Immunohistochemistry and western blot assay results revealed that the immune response and protein expression of NKCC1 in dorsal root ganglion neurons of the chronic constriction injury group increased significantly on days 7,14,and 21 after model establishment.No immune response or protein expression of KCC2 was observed in dorsal root ganglion neurons before and after model establishment.The Cl^– (chloride ion) fluorescent probe technique was used to evaluate the change of Cl^– concentration in dorsal root ganglion neurons of chronic constriction injury model rats.We found that the relative optical density of N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (a Cl^– fluorescent probe whose fluorescence Cenintensity decreases as Cl– concentration increases) in the dorsal root ganglion neurons of the chronic constriction injury group was significantly decreased on days 7 and 14 after model establishment.The whole-cell patch clamp technique revealed that the resting potential and action potential frequency of dorsal root ganglion neurons increased,and the threshold and rheobase of action potentials decreased in the chronic constriction injury group on day 14 after model establishment.After bumetanide administration,the above indicators were significantly suppressed.These results confirm that CCI can induce abnormal overexpression of NKCC1,thereby increasing the Cl^– concentration in dorsal root ganglion neurons;this then enhances the excitability of dorsal root ganglion neurons and ultimately promotes hyperalgesia and allodynia.In addition,bumetanide can achieve analgesic effects.All experiments were approved by the Institutional Ethics Review Board at the First Affiliated Hospital,College of Medicine,Shihezi University,China on February 22,2017 (approval No.A2017-169-01).