s: 33rd Annual Meeting of the Society of Neurosurgical Anesthesia and Critical Care: CLINICAL NEUROLOGICAL SCIENCE/CRITICAL CARE

s: 33rd Annual Meeting of the Society of Neurosurgical Anesthesia and Critical Care: CEREBRAL PROTECTION/TECHNIQUES

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.

UNLABELLED:The effect of trace levels of waste anesthetic gases on the health of postanesthesia care unit (PACU) nurses who work in an unscavenged environment has been questioned, although it seems likely that levels of trace gases in the PACU would be much lower than those in the operating room. In this study, we documented nitrous oxide levels in the ambient air of two large PACUs. Nitrous oxide levels were measured using a time-weighted average monitor worn by 33 PACU workers at two different hospitals for the duration of their shifts. On the same day, patient data were collected at the time of admission to the PACU. Data included age and weight of the patient, type of surgery, anesthetic technique, and end-tidal level of nitrous oxide immediately before the patient left the operating room. The mean time-weighted average nitrous oxide level in PACU A was 2.0 ppm (range 0-6.4); in PACU B, it was undetectable, i.e., < 2.0 ppm. Levels of nitrous oxide to which PACU patient care personnel are exposed are well below the National Institute of Occupational Safety and Health and Occupational Health and Safety Administration recommended exposure level of 25 ppm measured for the duration of anesthetic administration. IMPLICATIONS:Our results indicate that the levels of nitrous oxide in postanesthesia care units with well maintained, modern ventilation systems are very low. Previous research suggests that the health of workers exposed to these levels should not be adversely affected.

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)

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)

p erioperative nerve injuries have long been recognized as a complication of spinal and epidural anesthesia. Fortunately, severe or disabling neurologic complications rarely occur. Cheney et al. j examined the American Society of Anesthesiologists Closed Claims database to determine the role of nerve damage in malpractice claims filed against anesthesia care providers. Of the 4,183 claims reviewed, 670 (16%) were for anesthesia-related nerve injury, including 189 claims involving the lumbosacral roots (105 claims) or spinal cord (84 claims). Lumbosacral nerve root injuries having identifiable etiology were associated predominant ly with a regional anesthetic technique (92%), and were related to paresthesias during needle or catheter placement or pain during injection of local anesthetic. Major factors associated with spinal cord injury were blocks for chronic pain management and systemic anticoagulation in the presence of neuraxial block. Neurologic complications associated with neuraxial anesthesia may be divided into two categories: those that are unrelated to the spinal or epidural anesthetic but coincide temporally and those that are a direct result of the regional technique. Postoperative neurologic injury caused by pressure from improper patient positioning or from tightly applied casts or surgical dressings, as well as surgical t rauma are often attributed to the neuraxial anesthetic. Marinacci 2 evaluated 542 patients with postoperative neurologic deficits allegedly caused by spinal anesthesia. In only 4 cases were the findings related to the spinal anesthetic (cauda equina syndrome, arachnoiditis, and chronic radiculitis). In the remaining 538 patients, the neurologic deficits exhibited an

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/mm3. 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.