Ischaemic optic neuropathy after spinal fusion

Perioperative Blindness in Spine Surgery: A Scoping Literature Review

Perioperative vision loss (POVL) is a devastating surgical complication that impacts both the recovery from surgery and quality of life, most commonly occurring after spine surgery. With rates of spine surgery dramatically increasing, the prevalence of POVL will increase proportionately. This scoping review aims to aggregate the literature pertinent to POVL in spine surgery and consolidate recommendations and preventative measures to reduce the risk of POVL. There are several causes of POVL, and the main contribution following spine surgery is ischemic optic neuropathy (ION). Vision loss often manifests immediately following surgery and is irreversible and severe. Diffusion weighted imaging has recently surfaced as a diagnostic tool to identify ION. There are no effective treatments; therefore, risk stratification for counseling and prevention are vital. Patients undergoing prone surgery of long duration and/or with significant expected blood loss are at greatest risk. Future research is necessary to develop effective treatments.

Application of Controlled Hypotension During Surgery for Spinal Metastasis

With advances in tumor treatment, metastasis to bone is increasing, and surgery has become the only choice for most terminal patients. However, spinal surgery has a high risk and is prone to heavy bleeding. Controlled hypotension during surgery has outstanding advantages in reducing intraoperative bleeding and ensuring a clear field of vision, thus avoiding damage to important nerves and vessels. Antihypertensive drugs should be carefully selected after considering the patient's age, different diseases, etc, and a single or combined regimen can be used. Hypotension also inevitably leads to a decrease in perfusion of important organs, so the threshold of hypotension and the maintenance time of hypotension should be strictly limited, and the monitoring of important organs during the operation is particularly important. Information such as blood perfusion, blood oxygen saturation, cardiac output, and neurophysiological conduction potential changes should be obtained in a timely fashion, which will help to reduce the risk of hypotension. In short, when applying controlled hypotension, it is necessary to choose an appropriate threshold and duration, and appropriate monitoring should be conducted during the operation to ensure the safety of the patient.

Systematic Review and Meta-Analysis of Prone Position on Intraocular Pressure in Adults Undergoing Surgery

BACKGROUND

Patients undergoing surgery in the prone position may be at risk for postoperative vision loss associated with increased intraocular pressure. The purpose of this systematic review and meta-analysis is to estimate the magnitude of the increase in intraocular pressure at specific perioperative time points in adult patients. The research question to be addressed is "What is the magnitude of the increase in intraocular pressure at specific perioperative time points in adults undergoing surgery in the prone position?"

METHODS

Comprehensive search strategies were used to identify nine eligible studies (N = 229). Standardized mean difference effect sizes were calculated for two intraoperative time points.Time points for meta-analysis were selected to achieve the greatest number of comparisons for analysis at each time point. Prediction intervals for each time point were also calculated to show the dispersion of true effect sizes around the mean.

RESULTS

Meta-analysis showed that intraocular pressure increased significantly between induction of anesthesia and up to 10 minutes of prone position (T1: standardized mean difference [d] = 2.55; P < .001) and continued to increase significantly until the end of the prone position (T2: d = 3.44; P = .002).

CONCLUSIONS

Intraocular pressure increases of this magnitude demonstrate the need for implementing interventions to reduce the risk for postoperative vision loss in patients undergoing surgery in the prone position.

CLINICAL RELEVANCE

Implementing preoperative ophthalmologic examinations for patients undergoing surgery in the prone position may help to reduce the risk for ocular injury. Intraoperative interventions that can be implemented to reduce or mitigate the increase in intraocular pressure include implementing a 5- to 10-degree reverse Trendelenburg prone position, reducing the amount of time the patient is in the prone position, considering staged procedures, monitoring intraocular pressure, providing periodic position changes or rest periods, preventing pressure on the eye, and administering specific medications or anesthetics.

Practice Advisory for Perioperative Visual Loss Associated with Spine Surgery 2019: An Updated Report by the American Society of Anesthesiologists Task Force on Perioperative Visual Loss, the North American Neuro-Ophthalmology Society, and the Society for Neuroscience in Anesthesiology and Critical Care

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Alert for Perioperative Visual Loss: An Unusual Presentation of an Orbital Haemangioma during Spinal Surgery

A 62-year-old man with a history of non-insulin-dependent diabetes mellitus, hypertension and obesity, presented for elective lumbar laminectomy for spinal canal stenosis. Twenty minutes after placement in the prone position, he developed left orbital proptosis. The surgery was deferred and a subsequent CT scan showed an orbital haemangioma. This case highlights the importance of meticulous attention to eye-care for patients in the prone position.

[Post operative visual loss after cervical laminectomy in prone position]

Postoperative visual loss is a rare and devastating complication. The estimated incidence is 0.01-1% after non ocular surgery. It has been reported after spine, cardiac and head and neck surgeries. We report a patient who was operated for cervical laminectomy in prone position and complained of loss of vision in one eye postoperatively. He was thoroughly investigated after visual loss. The case was diagnosed as central retinal artery occlusion (CRAO) of the left eye. Here we consider the potential etiological factors causing this unilateral loss of vision and try to suggest strategies to reduce the incidence of the complication in spinal surgery.

Lumbar spine surgery positioning complications: a systematic review

OBJECT There are a variety of surgical positions that provide optimal exposure of the dorsal lumbar spine. These include the prone, kneeling, knee-chest, knee-elbow, and lateral decubitus positions. All are positions that facilitate exposure of the spine. Each position, however, is associated with an array of unique complications that result from excessive pressure applied to the torso or extremities. The authors reviewed clinical studies reporting complications that arose from positioning of the patient during dorsal exposures of the lumbar spine. METHODS MEDLINE, Scopus, and Web of Science database searches were performed to find clinical studies reporting complications associated with positioning during lumbar spine surgery. For articles meeting inclusion criteria, the following information was obtained: publication year, study design, sample size, age, operative time, type of surgery, surgical position, frame or table type, complications associated with positioning, time to first observed complication, long-term outcomes, and evidence-based recommendations for complication avoidance. RESULTS Of 3898 articles retrieved from MEDLINE, Scopus, and Web of Science, 34 met inclusion criteria. Twenty-four studies reported complications associated with use of the prone position, and 7 studies investigated complications after knee-chest positioning. Complications associated with the knee-elbow, lateral decubitus, and supine positions were each reported by a single study. Vision loss was the most commonly reported complication for both prone and knee-chest positioning. Several other complications were reported, including conjunctival swelling, Ischemic orbital compartment syndrome, nerve palsies, thromboembolic complications, pressure sores, lower extremity compartment syndrome, and shoulder dislocation, highlighting the assortment of possible complications following different surgical positions. For prone-position studies, there was a relationship between increased operation time and position complications. Only 3 prone-position studies reported complications following procedures of less than 120 minutes, 7 studies reported complications following mean operative times of 121-240 minutes, and 9 additional studies reported complications following mean operative times greater than 240 minutes. This relationship was not observed for knee-chest and other surgical positions. CONCLUSIONS This work presents a systematic review of positioning-related complications following prone, knee-chest, and other positions used for lumbar spine surgery. Numerous evidence-based recommendations for avoidance of these potentially severe complications associated with intraoperative positioning are discussed. This investigation may serve as a framework to educate the surgical team and decrease rates of intraoperative positioning complications.

Application of controlled hypotension combined with autotransfusion in spinal orthomorphia

Background:

Idiopathic scoliosis is a common spinal deformity in teenagers, which is managed mainly by orthomorphia. However, due to great trauma, long operative duration and large blood loss, a great amount of blood transfusion is needed during the surgery. Allogeneic blood transfusion should be reduced in order to release blood insufficient, decline blood transfusion expense, as well as avoid transfusion diseases.

Objective:

The objective of the following study is to investigate the value of controlled hypotension combined with autotransfusion in idiopathic scoliosis orthomorphia and in order to reduce surgical bleeding and reduction in blood transfusion.

Subjects and Methods:

Intra-operative controlled hypotension was performed during posterior orthomorphia surgery on all the 46 cases of idiopathic scoliosis, 17 cases in which were served as the control group, who underwent allogeneic blood transfusion without autotransfusion, whereas the other 29 cases were served as the experimental group, who underwent autotransfusion that including reinfusion of pre-operative deposited autologous blood and intra-operative salvaged autologous blood. The blood loss volume and transfusion status in two groups were observed.

Results and Conclusion:

Blood loss volume in the control group was 400-1000 (835.3 ± 167.5) mL and that in the experimental group was 350-1400 (812.1 ± 152.7) mL, there was no marked difference between the two groups (P > 0.05). The volume of allogeneic blood transfusion in the control group was 500-1800 (855.9 ± 321.1) mL, which was greater than that in the experimental group ((0-1300 (337.9 ± 258.3) mL) (P < 0.01). The results suggested that controlled hypotension reduces intraoperative bleeding and post-operative autotransfusion minimizes the need of allogeneic blood transfusion.

A case report and brief review of the literature on bilateral retinal infarction following cardiopulmonary bypass for coronary artery bypass grafting

Postoperative visual loss is a devastating perioperative complication. The commonest aetiologies are anterior ischaemic optic neuropathy (AION), posterior ischaemic optic neuropathy (PION), and central retinal artery occlusion (CRAO). These appear to be related to certain types of operation, most commonly spinal and cardiac bypass procedures; with the rest divided between: major trauma causing excessive blood loss; head/neck and nasal or sinus surgery; major vascular procedures (aortic aneurysm repair, aorto-bifemoral bypass); general surgery; urology; gynaecology; liposuction; liver transplantation and duration of surgery. The non-surgical risk factors are multifactorial: advanced age, prolonged postoperative anaemia, positioning (supine v prone), alteration of venous drainage of the retina, hypertension, smoking, atherosclerosis, hyperlipidaemia, diabetes, hypercoagulability, hypotension, blood loss and large volume resuscitation. Other important cardiac causes are septic emboli from bacterial endocarditis and emboli caused by atrial myxomata. The majority of AION cases occur during CPB followed by head/neck surgery and prone spine surgery. CPB is used to allow coronary artery bypass grafting on a motionless heart. It has many side-effects and complications associated with its use and we report here a case of bilateral retinal infarction during routine coronary artery bypass grafting in a young male patient with multiple risk factors for developing this complication despite steps to minimise its occurrence.

Anterior ischemic optic neuropathy after conventional coronary artery bypass graft surgery

Background

Perioperative optic neuropathy is a disease which can lead to serious, irreversible damage of vision. This complication could be the result of non-ocular surgery, for example, cardiac or spinal procedures.

We present a case of anterior ischemic neuropathy (AION) which occurred following a conventional coronary artery bypass graft procedure.

Case Report

A 57-year-old man, 4 days after Conventional Coronary Artery Bypass Graft surgery as result of multi-vessel stabile coronary artery disease and history of anterolateral wall myocardial infarction, was admitted to the Eye Clinic due to significant loss of vision in his right eye. The patient had hypertension and was a heavy smoker. On admission, the slit lamp examination revealed a relative afferent pupillary defect in the right eye. The fundus examination showed optic disc edema with the presence of flame hemorrhages. Best corrected visual acuity (BCVA) was 0.02. The results of eye examination and fluorescein angiography confirmed the diagnosis of AION. Anti-aggregation and antithrombotic treatment was continued with steroids and vasodilators. After 7 days of this treatment we noticed the improvement of BCVA to 0.2. At 6-month follow-up, the vision was stable, and fundus examination revealed optic disc atrophy.

Conclusions

After cardiac surgical operations, such as coronary artery bypass graft procedures, anterior ischemic optic neuropathy may occur. In those cases, close cooperation between the various specialists is necessary.

Complications in spinal deformity surgery: issues unrelated directly to intraoperative technical skills

STUDY DESIGN

Literature review of complications unrelated directly to surgical skills involved in spinal deformity surgery.

OBJECTIVE

Highlight complications associated with perioperative issues.

SUMMARY OF BACKGROUND DATA

Complications can arise from mundane events that arise during the operative experience, but are not directly related to surgical skills.

METHODS

Literature reviews that touches on the more common potential complication events that do not involve direct surgical expertise.

RESULTS

The topics of positioning, nutrition, blood loss, comorbidities, OR time, and pulmonary and GI concerns are discussed as basics that could derail a surgical outcome even with an otherwise uneventful surgical technique. The need for vigilance is stressed and the nuances of understanding these are discussed.

CONCLUSION

Mundane events can derail a perfectly executed surgical undertaking. Attention to detail, team work, close monitoring, and checklist type focus will help to improve, focus, and avoid these preventable complications that have nothing to do with direct surgical skills.

Perioperative visual loss in ocular and nonocular surgery

Incidence estimates for perioperative vision loss (POVL) after nonocular surgery range from 0.013% for all surgeries up to 0.2% following spine surgery. The most common neuro-ophthalmologic causes of POVL are the ischemic optic neuropathies (ION), either anterior (AION) or posterior (PION). We identified 111 case reports of AION following nonocular surgery in the literature, with most occurring after cardiac surgery, and 165 case reports of PION following nonocular surgery, with most occurring after spine surgery or radical neck dissection. There were an additional 526 cases of ION that did not specify if the diagnosis was AION or PION. We also identified 933 case reports of central retinal artery occlusion (CRAO), 33 cases of pituitary apoplexy, and 245 cases of cortical blindness following nonocular surgery. The incidence of POVL following ocular surgery appears to be much lower than that seen following nonocular surgery. We identified five cases in the literature of direct optic nerve trauma, 47 cases of AION, and five cases of PION following ocular surgery. The specific pathogenesis and risk factors underlying these neuro-ophthalmic complications remain unknown, and physicians should be alert to the potential for loss of vision in the postoperative period.

Postoperative ischemic optic neuropathy

STUDY DESIGN

Systematic literature review.

OBJECTIVE

To determine if there are predictors or preventative measures for postoperative ischemic optic neuropathy (ION) associated with spine surgery.

SUMMARY OF BACKGROUND DATA

Postoperative ION is a devastating complication that is most common after cardiac and spinal fusion surgery. Identifying patient or perioperative predictors for postoperative ION could lead to therapeutic modifications designed to minimize its occurrence.

METHODS

A systematic literature review was conducted in MEDLINE, EMBASE, and the Cochrane Collaboration Library for literature published in English from 1990 through 2008 reporting on ION following spine surgery. References from review articles of ION were used, but articles without original material were excluded. Data on study design, patient demographics, and perioperative characteristics were collected and analyzed. Two independent reviewers assessed the strength of literature using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria assessing quality, quantity, and consistency of results. Disagreements were resolved by consensus.

RESULTS

Nineteen of 360 articles on postoperative ION after spine surgery met inclusion/exclusion criteria. The quality of evidence was very low as the majority of articles were case reports. The majority of ION patients were men between 30 and 69 years, undergoing spinal fusion surgery with an operative duration greater than 5 hours and an estimated blood loss greater than 1 L. Confounding factors and lack of a denominator from the case reports and case series precluded identification of risk factors with even a modest level of evidence.

CONCLUSION

Postoperative ION after spinal surgery is a rare event, which may be associated with prone position surgery of more than 5 hours surgical duration and blood loss of more than 1 L. Informing patients of this remote risk should be considered during preoperative counseling. The quality of evidence for preventative measures for postoperative ION after spinal fusion surgery is very low, but it has been proposed that efforts aimed at reducing the duration or severity of venous congestion in the head may be beneficial.

Perioperative visual loss: what do we know, what can we do?

Perioperative visual loss (POVL), a rare, but devastating complication, can follow non-ocular surgery. Highest rates of visual loss are with cardiac and spine surgery. The main causes of visual loss after non-ocular surgery are retinal vascular occlusion and ischaemic optic neuropathy. This review updates readers on the incidence, suspected risk factors, diagnosis, and treatment of POVL due to these conditions.

ADULT DEGENERATIVE SCOLIOSIS

OBJECTIVE

To review and define principles and features of treatment for adult degenerative scoliosis, the most common cause of adult spinal deformities.

STUDY DESIGN

We conducted a comprehensive review of the literature and our clinical experience.

METHODS

A systematic review of Medline was conducted, including journal articles published in March 2007 and before. We searched for articles related to adult spinal deformities (scoliosis) and treatments.

CONCLUSION

Degenerative scoliosis is a complex disorder. The primary surgical aims are to decompress the neural elements, normalize both sagittal balance and coronal and rotational deformity, fixate to the sacrum/ilium when appropriate, and optimize conditions for osteogenesis and fusion.

Perioperative visual loss after nonocular surgeries

PURPOSE

To review the current knowledge of persistent visual loss after nonocular surgeries under general anesthesia.

DESIGN

Perspective.

METHODS

Literature review.

RESULTS

The incidence of perioperative visual loss after nonocular surgeries ranges from 0.002% of all surgeries to as high as 0.2% of cardiac and spine surgeries. Any portion of the visual pathways may be involved, from the corneas to the occipital lobes, but the most common site of permanent injury is the optic nerves, and the most often presumed mechanism is ischemia. Anterior ischemic optic neuropathy (AION) is more prevalent among cardiac surgery patients and posterior ischemic optic neuropathy (PION) predominates among those who have had spine and neck procedures. Patients range from age five to 81 years and typically awake with severe bilateral visual loss. Multiple factors have been proposed as risk factors for perioperative ION, including long duration in the prone position, excessive blood loss, hypotension, anemia, hypoxia, excessive fluid replacement, use of vasoconstricting agents, elevated venous pressure, head positioning, and a patient-specific vascular susceptibility that may be anatomic or physiologic. However, the risk factors for any given patient or procedure may vary and are likely multifactorial.

CONCLUSIONS

If, when an ophthalmologist is consulted for a patient with perioperative visual loss, an obvious ocular cause is not apparent, urgent neuroimaging should be obtained to rule out intracranial pathology. Anterior and posterior ION should be considered and careful documentation is essential. Currently, the pathogenesis of perioperative ION remains unclear, and preventive and therapeutic measures remain elusive.

Anaesthesia in the prone position

Prone positioning of patients during anaesthesia is required to provide operative access for a wide variety of surgical procedures. It is associated with predictable changes in physiology but also with a number of complications, and safe use of the prone position requires an understanding of both issues. We have reviewed the development of the prone position and its variants and the physiological changes which occur on prone positioning. The complications associated with this position and the published techniques for various practical procedures in this position will be discussed. The aim of this review is to identify the risks associated with prone positioning and how these risks may be anticipated and minimized.

Changes in intraocular pressure due to surgical positioning: studying potential risk for postoperative vision loss

STUDY DESIGN

Parallel group design.

OBJECTIVE

Compare the intraocular pressure responses in the prone flat versus prone Trendelenburg's position.

SUMMARY OF BACKGROUND DATA

Postoperative vision loss (PVL) complicates approximately 0.05% of spine surgeries. Prone positioning is considered a risk factor because it increases intraocular pressure, which may decrease perfusion pressure to the optic nerve (perfusion pressure = mean arterial pressure - intraocular pressure [IOP]). The prone Trendelenburg's position is often used during spine surgery; however, its effect on optic nerve perfusion is unknown. The purpose of this study is to compare the IOP responses in the prone flat versus prone Trendelenburg's positions to determine if prone Trendelenburg's position also risks PVL.

METHODS

Twenty subjects randomized into 2 groups. Group 1 lay in the prone flat position (0 degrees). Group 2 lay in the prone Trendelenburg's position (-7 degrees). IOPs were measured with a hand-held applanation tonometer while seated, 1 minute after assuming the group's position (Time 0), and at 10-minute intervals for 60 minutes.

RESULTS

The differences in mean IOPs with respect to positions and time were significant (P = 0.0001, P = 0.000). There was a significant difference between sitting and all other times for both groups. In Group 1, there was a significant difference in IOP between Time 0 and all other times prone flat (P < 0.05). In Group 2, there was a significant difference in IOP between Time 0 all other times prone Trendelenburg (P < 0.05).

CONCLUSION

IOP increases in the prone Trendelenburg's position, and when combined with other factors, may be a risk factor for PVL. The pathophysiology is discussed and suggestions for clinicians are made.

Vision loss after spine surgery: review of the literature and recommendations

✓In recent studies spinal surgery has replaced cardiac surgery as a leading cause of postoperative vision loss (POVL). Estimates of the incidence of POVL after spinal surgery range from 0.028 to 0.2%, but with advances in complex spinal instrumentation and the rise in annual spinal operations, POVL may see an ominous increase in its incidence. Postoperative vision loss is an uncommon but devastating complication, with unknown origin and pathogenesis. The authors undertook a literature review and summarize the current understanding of its pathophysiology, highlight the limitations of existing knowledge, and recommend practical guidelines for avoiding this devastating outcome.

The incidence of vision loss due to perioperative ischemic optic neuropathy associated with spine surgery: the Johns Hopkins Hospital Experience

STUDY DESIGN

Twenty-year retrospective review of 14,102 spine surgeries.

OBJECTIVE

To determine the incidence of perioperative ischemic optic neuropathy (POION) in spine surgery at our institution.

SUMMARY OF BACKGROUND DATA

In recent years, perioperative vision loss in patients undergoing spine surgery has become an issue of increasing concern to physicians, patients, and medicolegal experts. The incidence of POION in spine surgery has been addressed in two separate studies that found incidences of 0% and 0.12%.

METHODS

We performed a 20-year database search for all patients who underwent spine surgery and had a concurrent ICD-9 discharge diagnosis pertaining to vision loss. Patient charts were reviewed in detail to confirm the diagnosis of POION.

RESULTS

Of 14,102 cases of spine surgery during the study time frame, we identified 4 cases of POION, for an incidence of 0.028%. In 3 of the 4 cases, surgery was performed with the patient in the prone position; the fourth patient was placed in the lateral decubitus position. All affected patients had experienced intraoperative anemia, hypotension, or both. The average time of surgery was 420 minutes.

CONCLUSIONS

POION is a rare but potentially devastating and untreatable complication of spine surgery, particularly that performed with the patient in the prone position. Anemia, hypotension, long duration of surgery, and significant intraoperative hydration may all be risk factors for this condition. All patients undergoing spine surgery should be informed about the low but definite risk of this condition, and every attempt should be made during surgery to maintain stable hemoglobin and mean arterial pressure and to avoid overhydration.

Postoperative visual loss associated with spine surgery

Postoperative visual loss associated with spine surgery is a rare complication with no established definitive etiology. Multiple case reports have been published in the literature, and an overview of the case reports of the various visual disturbances following spine surgery is presented. Our objective was to review the current literature and determine if there were any risk factors that suggest what kind of patients have a higher likelihood of developing postoperative visual loss. Furthermore, analysis of factors common to the cases may offer a better understanding of possible etiologies leading to prevention strategies of postoperative visual loss. We used PubMed to perform a search of literature with spine surgery cases that are associated with visual disturbances. A total of 7 studies representing 102 cases were reviewed and evaluated in regard to age, sex, comorbidities, diagnosis, operative time, blood loss, systolic blood pressure, lowest hematocrit, and visual deficits and improvement. Ischemic optic neuropathy, especially posterior ischemic optic neuropathy, was the most common diagnosis found in the studies. The average age of the patients ranged from 46.5 years to 53.3 years with the majority having at least one comorbidity. Operative time ranged on average from 385 min to 410 min with a median in one case series of 480 min, average blood loss ranged from 3.5 l to 4.3 l and no visual improvement was seen in the majority of the cases. The etiology of postoperative visual loss is probably multifactorial, however, patients with a large amount of blood loss producing hypotension and anemia along with prolonged operative times may be causing a greater risk in developing visual disturbances. An acute anemic state may have an additive or synergistic effect with other factors (medical comorbidities) leading to visual disturbances. Although our study failed to provide definitive causative factors of postoperative visual loss, suggestions are made that warrant further studies.

Visual field defect after posterior spine fusion

STUDY DESIGN

Case report and literature review.

OBJECTIVES

Review cases and literature regarding visual loss following posterior spine fusion for scoliosis and emphasize right-to-left atrial shunt as a risk factor for paradoxical embolus resulting in a postoperative visual field defect.

SUMMARY OF BACKGROUND DATA

The existing literature discusses various possible etiologies of postoperative visual loss including direct pressure, hypotension, blood loss, and anemia. One study shows higher rates of cerebral microemboli in patients with right-to-left atrial shunts.

METHODS

Chart and literature review.

RESULTS

A paradoxical embolus to a branch of the central retinal artery resulted in a unilateral quadrant defect (homonymous quadrantanopsia) in a girl with a previously undiagnosed right-to-left atrial shunt.

CONCLUSIONS

Right-to-left atrial shunts may predispose to cerebral emboli during scoliosis surgery. These emboli may be a cause of postoperative visual field defects.

Controlled hypotension for spinal surgery

Controlled, deliberate hypotension during anesthesia for major spinal surgery reduces intraoperative blood loss and transfusion requirement. Hypotension may be achieved with increased doses of volatile anesthetic agents or by continuous infusion of vasodilating drugs. Safe application of this technique requires knowledge of the physiology of hemorrhagic shock and close intraoperative monitoring to avoid vasoconstriction and end-organ ischemia.

Incidence of and risk factors for perioperative optic neuropathy after cardiac surgery

BACKGROUND

Visual loss from optic neuropathy rarely occurs in the perioperative period in patients who have undergone nonocular surgery. We performed a retrospective, matched, case-control study to determine the incidence of perioperative optic neuropathy (PON) after cardiac surgery with the use of cardiopulmonary bypass (CPB) and to determine risk factors that may lead to this potentially devastating complication.

METHODS

Medical records of all patients undergoing cardiac surgery during a 9-year period were reviewed retrospectively to identify visual loss from acute unilateral and bilateral optic neuropathy during the perioperative period that had developed in patients. Data were collected from these patients and compared with data from control subjects matched for age, gender, risk factors for vascular disease, and type of surgery to determine the incidence of and potential risk factors for PON.

RESULTS

Of 9701 surgical patients requiring CPB, 11 patients (0.113%) with PON were identified. Although both the absolute and relative drop in hemoglobin during the perioperative period approached statistical significance, no other putative risk factors were identified.

CONCLUSIONS

The risk of PON associated with cardiac surgery in which CPB is used is low but substantial. The factors that lead to the condition remain unknown, although the presence of systemic vascular disease and both the absolute and relative drop in hemoglobin during the perioperative period seem to be important. Because PON often causes profound permanent visual loss, we recommend that patients, particularly those with systemic vascular disease, for whom cardiac surgery with CPB is planned, be made aware of this potential complication.

Complications per et postopératoires immédiates des arthrodèses lombaires et lombosacrées

PURPOSE OF THE STUDY

Incidence of complications following lumbar or lumbosacral fusion is still an imprecise notion. The aim of this prospective observational study was to determine the frequency of intraoperative and early postoperative complications after this procedure and to analyze favoring factors.

MATERIAL AND METHODS

Twenty-one orthopedic units participated in this study which included 872 patients who underwent lumbar or lumbosacral fusion procedures involving the sector limited by L1 and S1. A minimum of 6 months follow-up was required for inclusion. Four types of complications were studied: general complications, infection, neurological and meningeal complications, mechanical problems. The following preoperative and intraoperative parameters were recorded: epidemiological and morphological data, history of lumbar spine surgery, comorbid conditions, indication for surgery, and technical aspects of the fusion. Two types of analysis were performed. The first was a descriptive analysis designed to determined the overall incidence of complications and the incidence of each type of complication. A multivariate analysis was then performed in order to determine factors influencing occurrence of complications.

RESULTS

Mean follow-up was 13 months, mean age of the cohort was 51 +/- 15.5 years. Prior lumbar surgery was noted in 12% of the patients. A decompression procedure was associated in 40% of the patients due to lumbar stenosis. Posterolateral arthrodesis was used in 71% of the patients and 91% were instrumented. Most of the fusions were short, involving one or two levels. One or more intraoperative or early postoperative complications were observed in 200 patients (23%). The incidences of the four types of complications expressed in percent of the total cohort were 9.7%, 5.6%, 8.6%, and 3.6% for general, infectious, neurological and meningeal, and mechanical complications respectively. Three factors exhibited a significant correlation with occurrence of complications, irrespective of the type: excess weight, presence of several comorbid conditions, and extent of the zone of fusion.

CONCLUSION

This study enabled a precise assessment of the incidence of complications subsequent to lumbar or lumbosacral fusion: 23%. The incidence of serious complications requiring a reoperation was 14.7%. This finding, together with the factors found to influence occurrence of these complications should be kept in mind when determining indications for lumbar or lumbosacral fusion.

Unilateral Visual Loss After Cervical Spine Surgery

This is a case report of a patient who underwent an uneventful surgery for atlanto-axial dislocation in the prone position, after which he developed painless, unilateral loss of vision in the immediate postoperative period. Based on the ophthalmologic findings a probable diagnosis of ischemic optic neuropathy (ION) was made. Although he recovered his visual acuity completely in 1 month, the visual field defects and color vision abnormalities persisted. Intraoperative anemia, hypotension, with or without vasculopathic risk factors, and prolonged surgery in the prone position have been reported as major risk factors for the development of this complication following spine surgery. However, this healthy young man had an uneventful surgery with no such intraoperative complications. ION in this patient could have been due to a combination of factors, such as a malpositioned horseshoe headrest and surgery performed in the prone position, both of which have the potential to raise the intraocular pressure and lower the perfusion pressure of the optic nerve/nerve head. Variations in the blood supply of the optic nerve due to the presence of watershed zones could be another explanation for this dreaded complication.

Bilateral posterior ischemic optic neuropathy after lumbar spine surgery

PURPOSE

To report a case of bilateral posterior ischemic optic neuropathy (PION) in a healthy young patient after lumbar spine surgery which was initially diagnosed as functional visual loss.

DESIGN

Observational case report.

PARTICIPANT

A 33-year-old woman who experienced visual loss in the immediate postoperative period after a lumbar spine fusion.

TESTING

Serial visual field testing and fundus examinations, ERG.

RESULTS

Bilateral PION was confirmed 2 months postoperatively with the development of bilateral optic disc pallor and a normal ERG.

CONCLUSION

Young patients without vascular risk factors may develop bilateral PION after otherwise uncomplicated lumbar spine surgery. In subjects complaining of visual loss in the postoperative period who have a normal fundus and normal neuroimaging, a diagnosis of PION should be suspected, and close follow-up is warranted.

Postoperative blindness

This chapter discusses the cases of postoperative blindness reported in the literature and the theories that attempt to explain the mechanisms involved. Although uncommon, alterations in vision and blindness after anesthesia for major surgical procedures, particularly cardiopulmonary bypass or spine surgery, are well documented, with an incidence varying between 0.05% and 1%. Accurate incidence data are unavailable because it is not known what percentages are reported. However, the large number of case reports over many years has provided some significant information. Although sustained compression of the eye is an important cause, postoperative visual loss may also occur, in an unrelated manner, because of ischemic optic neuropathy, central retinal artery or vein occlusion, or cortical blindness.

Anesthesia for minimally invasive neurosurgery

Neurosurgerical techniques utilizing minimally invasive approaches will continue to emerge. For some of these future possibilities, anesthesia may not be required. Other types of neurosurgery, whether performed by humans or a machine, will require entry through the cranium and an absolute lack of movement. Anesthesia will keep pace with these innovations by accurately controlling the delivery of anesthetic to achieve optimal conditions. This control will allow for a safer, more comfortable surgical procedure while decreasing blood loss and morbidity associated with neurosurgery.

Neurophysiologic response to intraoperative lumbosacral spinal manipulation

BACKGROUND

Although the mechanisms of spinal manipulation are poorly understood, the clinical effects are thought to be related to mechanical, neurophysiologic, and reflexogenic processes. Animal studies have identified mechanosensitive afferents in animals, and clinical studies in human beings have measured neuromuscular responses to spinal manipulation. Few, if any, studies have identified the basic neurophysiologic mechanisms of spinal manipulation in human beings or animals.

OBJECTIVES

The purpose of this clinical investigation was to determine the feasibility of obtaining intraoperative neurophysiologic recordings and to quantify mixed-nerve root action potentials in response to lumbosacral spinal manipulation in a human subject undergoing lumbar spinal surgery.

METHODS

An L4-L5 laminectomy was performed in a 62-year-old man. Short-duration (<0.1 ms) mechanical force, manually assisted spinal manipulative thrusts (150 N) were delivered to the lumbosacral spine with an Activator II Adjusting Instrument. With the spine exposed, spinal manipulative thrusts were delivered internally to the L5 mammillary process, L5-S1 joint, and the sacral base with various force vectors. This protocol was repeated by contacting the skin overlying respective anatomic landmarks. Mixed-nerve root recordings were obtained from gas-sterilized platinum bipolar hooked electrodes attached to the S1 nerve root at the level of the dorsal root ganglion during the spinal manipulative thrusts and during a 30-second baseline period during which no spinal manipulative thrusts were applied.

RESULTS

During the active trials, mixed-nerve root action potentials were observed in response to both internal and external spinal manipulative thrusts. Differences in the amplitude and discharge frequency were noted in response to varying segmental contact points and force vectors, and similarities were noted for internally and externally applied spinal manipulative thrusts. Amplitudes of mixed-nerve root action potentials ranged from 200 to 2600 mV for internal thrusts and 800 to 3500 mV for external thrusts.

CONCLUSIONS

Monitoring mixed-nerve root discharges in response to spinal manipulative thrusts in vivo in human subjects undergoing lumbar surgery is feasible. Neurophysiologic responses appeared sensitive to the contact point and applied force vector of the spinal manipulative thrust. Further study of the neurophysiologic mechanisms of spinal manipulation in humans and animals is needed to more precisely identify the mechanisms and neural pathways involved.

Post-operative bilateral vision loss

A 41-year-old man presented with acute bilateral loss of vision upon awakening after elective surgery. After thorough evaluation it was determined that he had suffered bilateral posterior ischemic optic neuropathies secondary to hypotension while under general anesthesia. One eye showed significant improvement over the next 4 weeks, whereas the other remained unchanged.