Injury and Liability Associated With Spine Surgery.

BACKGROUND: Although spine surgery is associated with significant morbidity, the anesthesia liability profile for spine surgery is not known. We examined claims for spine procedures in the Anesthesia Closed Claims Project database to evaluate patterns of injury and liability. MATERIALS AND METHODS: A retrospective cohort study was performed. Inclusion criteria were anesthesia claims provided for surgical procedures in 2000 to 2014. We compared mechanisms of injury for cervical spine to thoracic or lumbar spine procedures using χ and the Fisher exact test. Univariate and multivariate logistic regression analyses were used to determine factors associated with permanent disabling injury in spine surgery claims. RESULTS: The 207 spine procedure (73% thoracic/lumbar; 27% cervical) claims comprised >10% of claims. Permanent disabling injuries to nerves, the spinal cord, and the eyes or visual pathways were more common with spine procedures than in nonspine procedures. Hemorrhage and positioning injuries were more common in thoracic/lumbar spine claims, whereas difficult intubation was more common in cervical spine claims. Multiple logistic regression demonstrated prone positioning (odds ratio=3.50; 95% confidence interval, 1.30-9.43) and surgical duration of ≥4 hours increased the odds of severe permanent injury in spine claims (odds ratio=2.73; 95% confidence interval, 1.11-6.72). CONCLUSIONS: Anesthesia claims related to spine surgery were associated with severe permanent disability primarily from nerve and eye injuries. Prone positioning and surgical duration of ≥4 hours were associated with permanent disabling injuries. Attention to positioning, resuscitation during blood loss, and reducing length of surgery may reduce these complications.

Perioperative Visual Loss in Spine Fusion Surgery: Ischemic Optic Neuropathy in the United States from 1998 to 2012 in the Nationwide Inpatient Sample.

BACKGROUND: Perioperative ischemic optic neuropathy (ION) causes visual loss in spinal fusion. Previous case-control studies are limited by study size and lack of a random sample. The purpose of this study was to study trends in ION incidence in spinal fusion and risk factors in a large nationwide administrative hospital database. METHODS: In the Nationwide Inpatient Sample for 1998 to 2012, procedure codes for posterior thoracic, lumbar, or sacral spine fusion and diagnostic codes for ION were identified. ION was studied over five 3-yr periods (1998 to 2000, 2001 to 2003, 2004 to 2006, 2007 to 2009, and 2010 to 2012). National estimates were obtained using trend weights in a statistical survey procedure. Univariate and Poisson logistic regression assessed trends and risk factors. RESULTS: The nationally estimated volume of thoracic, lumbar, and sacral spinal fusion from 1998 to 2012 was 2,511,073. ION was estimated to develop in 257 patients (1.02/10,000). The incidence rate ratio (IRR) for ION significantly decreased between 1998 and 2012 (IRR, 0.72 per 3 yr; 95% CI, 0.58 to 0.88; P = 0.002). There was no significant change in the incidence of retinal artery occlusion. Factors significantly associated with ION were age (IRR, 1.24 per 10 yr of age; 95% CI, 1.05 to 1.45; P = 0.009), transfusion (IRR, 2.72; 95% CI, 1.38 to 5.37; P = 0.004), and obesity (IRR, 2.49; 95% CI, 1.09 to 5.66; P = 0.030). Female sex was protective (IRR, 0.30; 95% CI, 0.16 to 0.56; P = 0.0002). CONCLUSIONS: Perioperative ION in spinal fusion significantly decreased from 1998 to 2012 by about 2.7-fold. Aging, male sex, transfusion, and obesity significantly increased the risk.

Perioperative visual loss.

Perioperative visual loss is an infrequent, devastating complication associated with spine surgery, most commonly from ischemic optic neuropathy. Current research and expert opinion indicate that it is associated with procedures that create elevated venous pressure in the head for prolonged periods of time. The largest case-control study on ischemic optic neuropathy associated with spine surgery found six independent and significant risk factors including male sex, obesity, Wilson frame use, longer operative times, greater blood loss, and a lower colloid to crystalloid ratio in the non-blood fluid administration. The American Society of Anesthesiologists developed a practice advisory for the prevention of this complication. In this setting, it is advisable to avoid significant physiologic and hemodynamic perturbations as much as possible, given the uncertainty of the pathophysiology. Because prevention of this complication cannot be guaranteed, consent for perioperative visual loss should be strongly considered in patients at high risk for this complication.

A perioperative consult service results in reduction in cost and length of stay for colorectal surgical patients: evidence from a healthcare redesign project.

BACKGROUND: A major restructuring of perioperative care delivery is required to reduce cost while improving patient outcomes. In a test implementation of this notion, we developed and implemented a perioperative consult service (PCS) for colorectal surgery patients. METHODS: A 6-month planning process was undertaken to engage key stakeholders from surgery, nursing, and anesthesia in a healthcare redesign project that resulted in the creation of a PCS to implement a coordinated clinical pathway. After Institutional Review Board (IRB) approval, data were collected for all elective colorectal procedures for three phases: phase 0 (pre-implementation; 1/2014-6/2014), phase 1 (7/2014-10/2014), and phase 2 (11/2014-10/2015). Length of stay (primary endpoint; LOS), total hospital cost, use of clinical pathway components, markers of functional recovery, and readmission and reoperation rates were analyzed. Outcomes and patient characteristics among phases were compared by two-tailed t tests and Wilcoxon rank-sum tests. Categorical variables were analyzed by chi-square and Fisher's exact tests. RESULTS: We studied 544 patients (phase 0 = 179; phase 1 = 124; phase 2 = 241), with 365 consecutive patients being cared for in the redesigned care structure. Median LOS was reduced and sustained after implementation (phase 0, 4.24 days; phase 1, 3.32 days; phase 2, 3.32 days, P < 0.01 phase 0 v. phases 1 and 2), and mean LOS was reduced in phase 2 (phase 0, 5.26 days; phase 1, 4.93 days; phase 2, 4.36 days, P < 0.01 phase 0 v. phase 2). Total hospital cost was reduced by 17 % (P = 0.05, median). Application of clinical pathway components was higher in phases 1 and 2 compared to phase 0 (P < 0.01 for all components except anti-emetics); measures of functional recovery improved with successive phases. Reoperation and 30-day readmission rates were no different in phase 1 or phase 2 compared to phase 0 (P > 0.15). CONCLUSIONS: Restructuring of perioperative care delivery through the launch of a PCS-reduced LOS and total cost in a significant and sustainable fashion for colorectal surgery patients. Based on the success of this care redesign project, hospital administration is funding expansion to additional services.

Dexmedetomidine Does Not Affect Evoked Potentials During Spine Surgery.

BACKGROUND: The effect of dexmedetomidine on evoked potentials (EPs) has not been elucidated. We aimed to investigate the effect of dexmedetomidine on somatosensory, motor, and visual EPs. METHODS: After IRB approval, 40 adult patients scheduled for elective spine surgery using total IV anesthesia with propofol and remifentanil were randomly assigned to receive either dexmedetomidine (n = 20) or placebo (n = 20) in a double-blind, placebo-controlled trial. After obtaining informed consent, positioning, and baseline EPs recording, patients were randomly assigned to either IV dexmedetomidine 0.6 µg/kg infused over 10 minutes, followed by 0.6 µg/kg/h, or a corresponding volume of IV normal saline (placebo). EP measures at 60 ± 30 minutes after initiation of study drug were defined as T1 and at 150 ± 30 minutes were defined as T2. Changes from baseline to T1 (primary end point) and from baseline to T2 (secondary end point) in EP latencies (milliseconds) and amplitudes (microvolts) were compared between groups. Data presented as mean ± SD (95% confidence interval). RESULTS: Data from 40 patients (dexmedetomidine: n = 20; age, 54 ± 3 years; 10 males; placebo: n = 20; age, 52 ± 2 years; 5 males) were analyzed. There was no difference between dexmedetomidine versus placebo groups in primary end points: change of somatosensory EPs at T1, latency: 0.01 ± 1.3 (-0.64, 0.65) vs 0.01 ± 1.3 (-0.64, 0.65), P = 0.43 (-1.24, 0.45); amplitude: 0.03 ± 0.14 (-0.06, 0.02) vs -0.01 ± 0.13 (-0.07, 0.05), P = 0.76 (-0.074, 0.1); motor EPs amplitude at T1: 65.1 ± 194.8 (-35, 165; n = 18) vs 109.2 ± 241.4 (-24, 243; n = 16), P = 0.57 (-113.5, 241.57); visual EPs at T1 (right eye), amplitude: 2.3 ± 3.6 (-0.4, 5.1; n = 11) vs 0.3 ± 6.0 (-3.3, 3.9; n = 16), P = 0.38 (-6.7, 2.6); latency N1: 2.3 ± 3.6 (-0.4, 5.1) vs 0.3 ± 6.0 (-3.3, 3.9), P = 0.38 (-6.7, 2.6); latency P1: -1.6 ± 13.4 (-11.9, 8.7) vs -1.4 ± 8.1 (-6.3, 3.5), P = 0.97 (-9.3, 9.7) or secondary end points. There were no differences between right and left visual EPs either at T1 or at T2. CONCLUSIONS: In clinically relevant doses, dexmedetomidine as an adjunct to total IV anesthesia does not seem to alter EPs and therefore can be safely used during surgeries requiring monitoring of EPs.

Postoperative opioid-induced respiratory depression: a closed claims analysis.

BACKGROUND: Postoperative opioid-induced respiratory depression (RD) is a significant cause of death and brain damage in the perioperative period. The authors examined anesthesia closed malpractice claims associated with RD to determine whether patterns of injuries could guide preventative strategies. METHODS: From the Anesthesia Closed Claims Project database of 9,799 claims, three authors reviewed 357 acute pain claims that occurred between 1990 and 2009 for the likelihood of RD using literature-based criteria. Previously cited patient risk factors for RD, clinical management, nursing assessments, and timing of events were abstracted from claim narratives to identify recurrent patterns. RESULTS: RD was judged as possible, probable, or definite in 92 claims (κ = 0.690) of which 77% resulted in severe brain damage or death. The vast majority of RD events (88%) occurred within 24 h of surgery, and 97% were judged as preventable with better monitoring and response. Contributing and potentially actionable factors included multiple prescribers (33%), concurrent administration of nonopioid sedating medications (34%), and inadequate nursing assessments or response (31%). The time between the last nursing check and the discovery of a patient with RD was within 2 h in 42% and within 15 min in 16% of claims. Somnolence was noted in 62% of patients before the event. CONCLUSIONS: This claims review supports a growing consensus that opioid-related adverse events are multifactorial and potentially preventable with improvements in assessment of sedation level, monitoring of oxygenation and ventilation, and early response and intervention, particularly within the first 24 h postoperatively.

Massive hemorrhage: a report from the anesthesia closed claims project.

BACKGROUND: Hemorrhage is a potentially preventable cause of adverse outcomes in surgical and obstetric patients. New understanding of the pathophysiology of hemorrhagic shock, including development of coagulopathy, has led to evolution of recommendations for treatment. However, no recent study has examined the legal outcomes of these claims. The authors reviewed closed anesthesia malpractice claims related to hemorrhage, seeking common factors to guide future management strategies. METHODS: The authors analyzed 3,211 closed surgical or obstetric anesthesia malpractice claims from 1995 to 2011 in the Anesthesia Closed Claims Project. Claims where patient injury was attributed to hemorrhage were compared with all other surgical and obstetric claims. Risk factors for hemorrhage and coagulopathy, clinical factors, management, and communication issues were abstracted from claim narratives to identify recurrent patterns. RESULTS: Hemorrhage occurred in 141 (4%) claims. Obstetrics accounted for 30% of hemorrhage claims compared with 13% of nonhemorrhage claims (P < 0.001); thoracic or lumbar spine surgery was similarly overrepresented (24 vs. 6%, P < 0.001). Mortality was higher in hemorrhage than nonhemorrhage claims (77 vs. 27%, P < 0.001), and anesthesia care was more often judged to be less than appropriate (55 vs. 38%, P < 0.001). Median payments were higher in hemorrhage versus nonhemorrhage claims ($607,750 vs. $276,000, P < 0.001). Risk factors for hemorrhage and coagulopathy were common, and initiation of transfusion therapy was commonly delayed. CONCLUSIONS: Hemorrhage is a rare, but serious, cause of anesthesia malpractice claims. Understanding which patients are at risk can aid in patient referral decisions, design of institutional systems for responding to hemorrhage, and education of surgeons, obstetricians, and anesthesiologists.

Perioperative visual loss and anesthetic management.

PURPOSE OF REVIEW: Perioperative visual loss (POVL) is an uncommon complication primarily associated with cardiac, spine, and head and neck surgery that can have a potentially severe impact on quality of life. The largest multicenter case control study to date on POVL recently identified risk factors associated with ischemic optic neuropathy and prone spinal fusion surgery. This review will summarize these findings and the updated American Society of Anesthesiologists practice advisory on POVL to provide guidance on identification and management of high-risk patients undergoing prone spine surgery. Epidemiology data on POVL from national databases, POVL in robotic surgery, and posterior reversible encephalopathy syndrome as a newer cause of POVL will also be discussed. RECENT FINDINGS: Risk factors associated with prone spinal fusion surgery and ischemic optic neuropathy identified in a large multicenter case-control study include male sex, obesity, use of the Wilson spinal frame, longer anesthetic duration, greater blood loss, and a lower percentage of colloid in the nonblood fluid administration. SUMMARY: Strategies aimed at modifying risk factors for ischemic optic neuropathy associated with prone spinal fusion surgery that are extrinsic to the patient may decrease its incidence. Further research is needed to validate this concept.

Autopsy utilization in medicolegal defense of anesthesiologists.

BACKGROUND: The rate of autopsy in hospital deaths has declined from more than 50% to 2.4% over the past 50 yr. To understand the role of autopsies in anesthesia malpractice claims, we examined 980 closed claims for deaths that occurred in 1990 or later in the American Society of Anesthesiologists Closed Claims Project Database. METHODS: Deaths with autopsy were compared with deaths without autopsy. Deaths with autopsy were evaluated to answer the following four questions: Did autopsy findings establish a cause of death? Did autopsy provide new information? Did autopsy identify a significant nonanesthetic contribution to death? Did autopsy help or hurt the defense of the anesthesiologist? Reliability was assessed by κ scores. Differences between groups were compared with chi-square analysis and Kolmogorov-Smirnov test with P < 0.05 for statistical significance. RESULTS: Autopsies were performed in 551 (56%) of 980 claims for death. Evaluable autopsy information was available in 288 (52%) of 551 claims with autopsy. Patients in these 288 claims were younger and healthier than those in claims for death without autopsy (P < 0.01). Autopsy provided pathologic diagnoses and an unequivocal cause of death in 21% of these 288 claims (κ= 0.71). An unexpected pathologic diagnosis was found in 50% of claims with evaluable autopsy information (κ = 0.59). Autopsy identified a significant nonanesthetic contribution in 61% (κ = 0.64) of these 288 claims. Autopsy helped in the defense of the anesthesiologist in 55% of claims and harmed the defense in 27% (κ = 0.58) of claims with evaluable autopsy information. CONCLUSIONS: Autopsy findings were more often helpful than harmful in the medicolegal defense of anesthesiologists. Autopsy identified a significant nonanesthetic contribution to death in two thirds of claims with evaluable autopsy information.

Cervical spinal cord, root, and bony spine injuries: a closed claims analysis.

BACKGROUND: The aim of this study was to characterize cervical cord, root, and bony spine claims in the American Society of Anesthesiologists Closed Claims database to formulate hypotheses regarding mechanisms of injury. METHODS: All general anesthesia claims (1970-2007) in the Closed Claims database were searched to identify cervical injuries. Three independent teams, each consisting of an anesthesiologist and neurosurgeon, used a standardized review form to extract data from claim summaries and judge probable contributors to injury. RESULTS: Cervical injury claims (n = 48; mean ± SD age 47 ± 15 yr; 73% male) comprised less than 1% of all general anesthesia claims. When compared with other general anesthesia claims (19%), cervical injury claims were more often permanent and disabling (69%; P < 0.001). In addition, cord injuries (n = 37) were more severe than root and/or bony spine injuries (n = 10; P < 0.001), typically resulting in quadriplegia. Although anatomic abnormalities (e.g., cervical stenosis) were often present, cord injuries usually occurred in the absence of traumatic injury (81%) or cervical spine instability (76%). Cord injury occurred with cervical spine (65%) and noncervical spine (35%) procedures. Twenty-four percent of cord injuries were associated with the sitting position. Probable contributors to cord injury included anatomic abnormalities (81%), direct surgical complications (24% [38%, cervical spine procedures]), preprocedural symptomatic cord injury (19%), intraoperative head/neck position (19%), and airway management (11%). CONCLUSION: Most cervical cord injuries occurred in the absence of traumatic injury, instability, and airway difficulties. Cervical spine procedures and/or sitting procedures appear to predominate. In the absence of instability, cervical spondylosis was the most common factor associated with cord injury.

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.

Prolonged propofol anesthesia is not associated with an increase in blood lactate.

BACKGROUND: Lactic acidosis is considered an early sign of propofol infusion syndrome. In this study, we investigated the changes in lactate and pH with propofol versus volatile anesthesia (VA) of long duration. METHODS: Demographic and intraoperative data were recorded retrospectively from the anesthesia records of patients who underwent elective spine surgery longer than 8 h. Propofol patients were matched 1:2 to VA patients, based on anesthesia time (AT) (+/-30 min) and blood loss (BL) (+/-500 mL). RESULTS: Of 246 patients identified, 50 received propofol (AT = 10 +/- 2 h, BL = 1955 +/- 1409 mL) and were matched to 100 VA cases (AT = 10 +/- 1 h, BL = 1801 +/- 1543 mL), and of those, 40 and 72 patients, respectively, had complete lactate data at baseline and at 8 h after anesthesia and were included in the main analysis. The propofol group received 8.8 +/- 2 mg x kg(-1) x h(-1) of propofol. The VA group age was older than the propofol group (58 +/- 12 vs 51 +/- 15 yr, respectively, P = 0.002), but there was no difference between the groups in gender, ASA grade, intraoperative hemodynamic variables, and use of vasopressors. After 8 h, the VA group had a larger increase in arterial lactate from baseline compared with the propofol group (change from baseline: propofol, 0.48 +/- 0.72 mmol/L; VA, 1.2 +/- 1.2 mmol/L, P = 0.001). CONCLUSIONS: During prolonged spine surgery >8 h, VA was associated with higher serum lactate, when compared with propofol infusion. Prospective studies are needed to elucidate the exact mechanisms and clinical implications of this finding.

Liability associated with obstetric anesthesia: a closed claims analysis.

BACKGROUND: Obstetrics carries high medical liability risk. Maternal death and newborn death/brain damage were the most common complications in obstetric anesthesia malpractice claims before 1990. As the liability profile may have changed over the past two decades, the authors reviewed recent obstetric claims in the American Society of Anesthesiologists Closed Claims database. METHODS: Obstetric anesthesia claims for injuries from 1990 to 2003 (1990 or later claims; n = 426) were compared to obstetric claims for injuries before 1990 (n = 190). Chi-square and z tests compared categorical variables; payment amounts were compared using the Kolmogorov-Smirnov test. RESULTS: Compared to pre-1990 obstetric claims, the proportion of maternal death (P = 0.002) and newborn death/brain damage (P = 0.048) decreased, whereas maternal nerve injury (P < 0.001) and maternal back pain (P = 0.012) increased in 1990 or later claims. In 1990 or later claims, payment was made on behalf of the anesthesiologist in only 21% of newborn death/brain damage claims compared to 60% of maternal death/brain damage claims (P < 0.001). These payments in both groups were associated with an anesthesia contribution to the injury (P < 0.001) and substandard anesthesia care (P < 0.001). Anesthesia-related newborn death/brain damage claims had an increased proportion of delays in anesthetic care (P = 0.001) and poor communication (P = 0.007) compared to claims unrelated to anesthesia. CONCLUSION: Newborn death/brain damage has decreased, yet it remains a leading cause of obstetric anesthesia malpractice claims over time. Potentially preventable anesthetic causes of newborn injury included delays in anesthesia care and poor communication between the obstetrician and anesthesiologist.

Development of an index to characterize the "invasiveness" of spine surgery: validation by comparison to blood loss and operative time.

STUDY DESIGN: Prospective cohort study. OBJECTIVE: To create and validate an index describing the extent of spine surgical intervention to allow fair comparisons of complication rates among patients treated by different surgeons, devices, or hospitals. SUMMARY OF BACKGROUND DATA: Safety comparisons in spine surgery are limited by lack of methods that adjust for important variations in the surgical "case-mix." Among other factors, the magnitude of an operation is likely to have a substantial influence on the likelihood of complications. METHODS: We created a spine surgery invasiveness index defined as the sum, across all vertebral levels, of 6 possible interventions on each operated vertebra: anterior decompression, anterior fusion, anterior instrumentation, posterior decompression, posterior fusion, and posterior instrumentation. We assessed the validity of this index by examining its association with blood loss and surgery duration in 1723 spine surgeries, adjusting for important factors including age, gender, body mass index, diagnosis, neurologic deficit, revision surgery, and vertebral level of surgery. RESULTS: Blood loss increased by 11.5% and surgery duration increased by 12.8 minutes for each unit increase in the invasiveness index. The invasiveness index explained 44% of the variation in blood loss and 52% of the variation in surgery duration. For specific surgical components, blood loss increased by 9.4% and surgery duration by 11.4 minutes for each vertebral level of anterior decompression, 19.4% and 33.8 minutes for each segment of anterior instrumentation, 12.9% and 22.7 minutes for each level of posterior decompression, and 25.1% and 18.8 minutes for each segment of posterior instrumentation. CONCLUSION: An "invasiveness" index based on the number of vertebrae decompressed, fused, or instrumented showed the expected associations with both blood loss and surgery duration. This quantitative description of surgery invasiveness may be useful to adjust for surgical variations when making safety comparisons in spine surgery.

ASRA Practice Advisory on Neurologic Complications in Regional Anesthesia and Pain Medicine.

Neurologic complications associated with regional anesthesia and pain medicine practice are extremely rare. The ASRA Practice Advisory on Neurologic Complications in Regional Anesthesia and Pain Medicine addresses the etiology, differential diagnosis, prevention, and treatment of these complications. This Advisory does not focus on hemorrhagic and infectious complications, because they have been addressed by other recent ASRA Practice Advisories. The current Practice Advisory offers recommendations to aid in the understanding and potential limitation of neurologic complications that may arise during the practice of regional anesthesia and pain medicine.

Complications associated with eye blocks and peripheral nerve blocks: an american society of anesthesiologists closed claims analysis.

BACKGROUND AND OBJECTIVES: Concern for block-related injury and liability has dissuaded many anesthesiologists from using regional anesthesia for eye and extremity surgery, despite many studies demonstrating the benefits of regional over general anesthesia. To determine injury patterns and liability associated with eye and peripheral nerve blocks, we re-examined the American Society of Anesthesiologists Closed Claims Database as part of the American Society of Regional Anesthesia and Pain Medicine's Practice Advisory on Neurologic Complications of Regional Anesthesia and Pain Medicine. METHODS: Claims with eye or peripheral nerve blocks performed perioperatively from 1980 through 2000 were analyzed. The liability profile of anesthesiologists who provided both the eye block and sedation for eye surgery was compared with the profile of anesthesiologists who provided sedation only. The injury patterns associated with peripheral nerve blocks and payment factors were analyzed. RESULTS: Anesthesiologists who provided both the eye block and sedation for eye surgery (n = 59) had more injuries associated with block placement (P < .001), a higher proportion of claims with permanent injury (P < .05), and a higher proportion of claims with plaintiff payment (P < .05), compared with anesthesiologists who provided sedation only (n = 38). Peripheral nerve blocks (n = 159) were primarily associated with temporary injuries (56%). Local anesthetic toxicity was associated with 7 of 19 claims with death or brain damage. CONCLUSIONS: Performance of eye blocks by anesthesiologists significantly alters their liability profile, primarily related to permanent eye damage from block needle trauma. Though most peripheral nerve block claims are associated with temporary injuries, local anesthetic toxicity is a major cause of death or brain damage in these claims.

Effects of anemia and hypotension on porcine optic nerve blood flow and oxygen delivery.

BACKGROUND: Perioperative ischemic optic neuropathy occurs after major surgical procedures, which are often associated with hypotension, anemia, or venous congestion. However, the effects of these conditions on optic nerve (ON) blood flow are unknown and cannot be studied adequately in humans. METHODS: Farm-raised pigs were anesthetized with isoflurane, kept normocapnic and normothermic, and subjected to conditions of euvolemic or hypovolemic hypotension (mean arterial pressure 50-55 mm Hg), anemia (hematocrit 17%), venous congestion, and combinations thereof. Control animals were kept euvolemic and normotensive for the entire experiment. Fluorescent microspheres were used to measure cerebral blood flow (CBF) and ON blood flow at baseline and after experimental conditions, and to calculate oxygen delivery (DO2). RESULTS: No significant changes in CBF or ON blood flow or DO2 occurred with euvolemic hypotension (n = 5), compared with controls (n = 12). Hypovolemic hypotension (n = 4) resulted in stable CBF and cerebral DO2, but significant reductions in ON DO2 (P = 0.032). The significant increase in CBF associated with anemia (n = 6) resulted in stable cerebral DO2. In contrast, ON blood flow did not significantly change with anemia, with (n = 5) or without (n = 6) euvolemic hypotension, resulting in significant reductions in ON DO2 (P < 0.01). CONCLUSION: Compensatory mechanisms for porcine CBF maintain stable DO2 under specified conditions of hypotension or anemia, whereas ON compensatory mechanisms were unable to maintain blood flow and to preserve DO2. The authors conclude that the porcine ON is more susceptible to physiologic perturbations than the brain.