Diana G. McGregor

Preoperative antiplatelet therapy does not increase the risk of spinal hematoma associated with regional anesthesia

One thousand orthopedic procedures in 924 patients given spinal or epidural anesthesia were prospectively studied to determine the risk of hemorrhagic complications associated with regional anesthesia.A history of excessive bruising or bleeding was elicited in 115 (12%) patients. Preoperative antiplatelet medications were taken by 386 (39%) patients. Aspirin was the most frequently reported antiplatelet drug and was taken by 193 patients. Subcutaneous heparin was administered to 22 patients before surgery on the operative day. One patient of 774 tested had a preoperative platelet count less than 100,000/mm.3 In addition, 26 of 171 preoperative prothrombin times and 10 of 115 preoperative activated partial thromboplastin times were longer than normal. Only 31 preoperative bleeding times were performed; five were prolonged. There were no documented spinal hematomas (major hemorrhagic complications). Blood was noted during needle or catheter placement (minor hemorrhagic complication) in 223 (22%) patients, including 73 patients with frank blood in the needle or catheter. Preoperative antiplatelet therapy did not increase the incidence of minor hemorrhagic complications. However, female gender, increased age, a history of excessive bruising/bleeding, surgery to the hip, continuous catheter anesthetic technique, large needle gauge, multiple needle passes, and moderate or difficult needle placement were all significant risk factors. The lack of correlation between antiplatelet medications and bloody needle or catheter placement (producing clinically insignificant collections of blood in the spinal canal or epidural space) is strong evidence that preoperative antiplatelet therapy is not a significant risk factor for the development of neurologic dysfunction from spinal hematoma in patients who undergo spinal or epidural anesthesia while receiving these medications. (Anesth Analg 1995;80:303-9)

A retrospective review of 4767 consecutive spinal anesthetics: Central nervous system complications

Serious neurologic complications rarely occur after spinal anesthesia.Historically, the reported frequency of persistent sensory or motor deficits has ranged from 0.005% to 0.7%. However, the introduction of small-gauge needles and new local anesthetics and intrathecal adjuvants makes it necessary to reevaluate the frequency of neurologic complications after spinal anesthesia. This study is a retrospective review of 4767 consecutive spinal anesthetics performed between June 1987 and June 1990. Mean patient age was 65 +/- 15 yrs. There were 3560 (74.7%) men and 1207 (25.3%) women. A preexisting neurologic condition was present in 481 (10.1%) cases. The surgical procedures were genitourinary and lower extremity orthopedic in 4348 (91.2%) cases. A paresthesia was elicited during needle placement in 298 (6.3%) cases. Six patients reported pain upon resolution of the spinal anesthetic (persistent paresthesia). Four persistent paresthesias resolved within 1 wk; the remaining two resolved in 18-24 mo. The presence of a paresthesia during needle placement significantly increased the risk of persistent paresthesia (P < 0.001). There were also two infectious complications. One patient with recent (treated) urosepsis underwent a urologic procedure under spinal anesthesia and subsequently developed a disc space infection. The second patient developed a paraspinal abscess. Both were treated with surgical drainage and antibiotics and remained neurologically intact. There were 62 (1.3%) patients with a postdural puncture headache, including 23 (0.5%) who underwent an epidural blood patch. These results are similar to those of previously published reviews and demonstrate the continued safety of spinal anesthesia. (Anesth Analg 1997;84:578-84)

Neurologic complications of 603 consecutive continuous spinal anesthetics using macrocatheter and microcatheter techniques

Recent case reports of cauda equina syndrome after continuous spinal anesthesia have led to a reevaluation of the indications and applications of this regional anesthetic technique.However, few large studies have formally investigated the frequency of neurologic complications using macro- and microcatheter (smaller than 24 gauge) techniques. This retrospective review examines 603 continuous spinal anesthetics, including 127 administered through a 28-gauge microcatheter, performed between June 1987 and May 1992. The surgical procedure was orthopedic in 397 of 476 (83.4%) macrocatheter patients. All microcatheter patients were parturients. Three patients reported pain (persistent paresthesia) postoperatively. In two patients, the symptoms resolved in 4 days; the other patient was discharged 8 days postoperatively with residual foot pain. There was also one patient with aseptic meningitis and one patient with a sensory cauda equina syndrome (still present after 15 mo). There were 58 (9.6%) patients with a postdural puncture headache (PDPH), including 42 of 127 (33.1%) patients in the microcatheter group. An epidural blood patch was performed in 41 (6.8%) patients. The frequency of neurologic complications, excluding PDPH, is similar to those in published reviews. However, PDPH in microcatheter patients is more frequent than previously reported. (Anesth Analg 1997;84:1063-70)

Hyperglycemia in Patients Undergoing Cerebral Aneurysm Surgery: Its Association With Long-term Gross Neurologic and Neuropsychological Function

OBJECTIVE To evaluate whether elevated intraoperative blood glucose concentrations are associated with an increased risk of long-term neurologic dysfunction in patients at risk for ischemic brain injury. PATIENTS AND METHODS Data from 1000 patients were retrieved from the Intraoperative Hypothermia for Aneurysm Surgery Trial database. All patients were recruited between February 2000 and April 2003, and underwent surgery for aneurysm clipping within 14 days of subarachnoid hemorrhage. Gross neurologic and neuropsychological function was evaluated at 3 months after surgery using certified observers and standardized assessment instruments. Intraoperative blood glucose concentrations, measured once when the aneurysm clip was placed, were correlated with neurologic outcome using both univariable and multivariable logistic regression analyses. RESULTS Blood glucose concentrations at the time of aneurysm clipping ranged from 59 to 331 mg/dL. At 3 months after surgery, those with blood glucose concentrations of 129 mg/dL or more (upper 2 quartiles) were more likely to have impaired cognition (P=.03). Those with glucose concentrations of 152 mg/dL or more (upper quartile) were more likely to experience deficits in gross neurologic function assessed by the National Institutes of Health Stroke Scale (P<.05), but not other scoring scales. Length of stay in intensive care units was longer in those with glucose concentrations of 129 mg/dL or more, but there was no difference among glucose groups in the duration of overall hospital stay or the fraction of patients discharged to home. CONCLUSION In patients at high risk for ischemic brain injury, intraoperative hyperglycemia, of a magnitude commonly encountered clinically, was associated with long-term changes in cognition and gross neurologic function.

Effect of single-dose dexamethasone on blood glucose concentration in patients undergoing craniotomy.

Summary: Dexamethasone, a corticosteroid used to treat cerebral edema, is known to produce elevations in the blood glucose concentration, but the effect of a single intraoperative dose of dexamethasone on the blood glucose concentration is unknown. Glucose concentrations in response to either a 10-mg intravenous bolus of dexamethasone or a saline placebo were evaluated in nondiabetic patients undergoing elective craniotomy. Both arterial and venous blood glucose concentrations were obtained immediately before and after treatment and hourly for 4 hours intraoperatively. The arterial blood glucose concentration in those who received 10 mg dexamethasone (n = 10) increased from 97 ± 15 mg/dL (mean ± SD) to 149 ± 23 mg/dL over the course of the study, compared with a change from 88 ± 11 mg/dL to 103 ± 12 mg/dL in those who received placebo (n = 10) (P < 0.05 for 4-hour sample vs. baseline for both groups; P < 0.05 between groups at 4 hours). Further, venous blood glucose concentrations were highly predictive of arterial glucose values (R2 = 0.98; P < 0.001). Since elevations in the blood glucose concentration should be avoided in the setting of central nervous system ischemia, findings from this investigation suggest that contemplated corticosteroid use should be reviewed for appropriateness of treatment. If dexamethasone is used, even as a single dose during craniotomy, intraoperative blood glucose concentrations should be carefully monitored and hyperglycemia treated, particularly in patients at risk for glucose-mediated exacerbation of brain injury.

Effect of Nitrous Oxide on Neurologic and Neuropsychological Function after Intracranial Aneurysm Surgery

Background:Laboratory studies suggest that nitrous oxide augments brain injury after ischemia or hypoxia. The authors examined the relation between nitrous oxide use and outcomes using data from the Intraoperative Hypothermia for Aneurysm Surgery Trial. Methods:The Intraoperative Hypothermia for Aneurysm Surgery Trial was a prospective randomized study of the impact of intraoperative hypothermia (temperature = 33°C) versus normothermia (temperature = 36.5°C) in patients with aneurysmal subarachnoid hemorrhage undergoing surgical clipping. Anesthesia was dictated by a limited-options protocol with the use of nitrous oxide determined by individual anesthesiologists. All patients were assessed daily for 14 days after surgery or until hospital discharge. Neurologic and neuropsychological testing were conducted at 3 months after surgery. Outcome data were analyzed via both univariate tests and multivariate logistic regression analysis correcting for factors thought to influence outcome. An odds ratio (OR) greater than 1.0 denotes a worse outcome in patients receiving nitrous oxide. Results:Outcome data were available for 1,000 patients, of which 373 received nitrous oxide. There was no difference between groups in the development of delayed ischemic neurologic deficit. At 3 months after surgery, there were no significant differences between groups in any outcome variable: Glasgow Outcome Score (OR, 0.84; 95% confidence interval [CI], 0.63–1.14; P = 0.268), National Institutes of Health Stroke Scale (OR, 1.29; 95% CI, 0.96–1.73; P = 0.087), Rankin Disability Score (OR, 0.84; 95% CI, 0.61–1.15; P = 0.284), Barthel Activities of Daily Living Index (OR, 1.01; 95% CI, 0.68–1.51; P = 0.961), or neuropsychological testing (OR, 1.26; 95% CI, 0.85–1.87; P = 0.252). Conclusions:In a population of patients at risk for ischemic brain injury, nitrous oxide use had no overall beneficial or detrimental impact on neurologic or neuropsychological outcomes.