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Continuous spinal anesthesia: mechanical and technical problems of catheter placement.

BACKGROUND AND OBJECTIVE: Although continuous spinal anesthesia with microcatheters has a number of advantages, there are also some drawbacks: technical problems in advancing the catheter, the possibility of traumatizing neural structures, the development of cauda equina syndrome, and maldistribution of the local anesthetic. METHODS: Spinaloscopy was performed with a 2-mm-diameter endoscope in fresh cadavers to visualize the fate of the catheters, as well as the distribution of the local anesthetic administered through these fine-bore catheters. Midline and paramedian approach achieved an easy insertion of the 28-gauge catheter as long as the 22-gauge needle was not advanced too far into the subarachnoid space, thereby making it impossible for the catheter to bend at the anterior wall of the dura mater. RESULTS: Injection of methylene blue-colored hyperbaric local anesthetic through the catheter revealed an inhomogenous distribution with pooling in the caudal segments. After the catheter tip leaves the needle, the catheter should be advanced only 2-3 cm to avoid coiling, possible damage of the nerve roots, or malpositioning in preformed pouches. CONCLUSION: To take advantage of continuous spinal anesthesia, a meticulous technique is required.

Anesthesia, Spinal↗

[Spinal anesthesia and prevention of thrombosis by heparin].

Non traumatic spinal hematomas are a rare pathology, anticoagulant treatments are one of their most frequent etiology. Therefore, the association of spinal anesthesia and a preventive treatment which has antithrombotic aim by the use of subcutaneous heparin (non fragmented or low molecular weight) is being discussed by many authors. It is lawful to associate spinal anesthesia with a soft dose of non fragmented subcutaneous heparin (Kakkar method) if the protocols are strictly respected. It is certainly possible to use low molecular weight subcutaneous heparin as well. However a slight decline in their use urges anyone to be very cautious.

Anesthesia, Conduction↗

High spinal anesthesia does not depress central nervous system function as measured by central conduction time and somatosensory evoked potentials.

Short-latency somatosensory evoked potentials (SSEPs) in response to median nerve stimulation were recorded from the neck and the scalp before and during diagnostic high spinal anesthesia (touch T3, pinprick C8) in six patients with chronic pain. The central conduction time--the time difference between the neck-recorded N13 and the scalp-recorded N20--and the amplitudes of the SSEPs did not change in a statistically significant way during high spinal anesthesia. However, latencies of the neck-recorded N13 and the scalp-recorded N20 and P25 increased slightly. This may have been due to a local anesthetic effect on those spinal roots of the median nerve in which segmental pinprick analgesia occurred. Because high spinal anesthesia did not depress central nervous function, as measured by central conduction time, and SSEP amplitudes, it is concluded that scalp-recorded SSEPs during high spinal anesthesia measure the effects of local anesthetics in the cerebrospinal fluid on neuronal pathways outside the brain.

Adult↗

Proximal paraparesis following spinal anesthesia.

A 70-year-old man with prostatic cancer extending to the urinary bladder underwent transurethral resection of the bladder neck under spinal anesthesia and developed weakness of the proximal lower limbs a few hours after the procedure. The weakness persisted for several months. Because there were no local surgical complications (hematoma, infectious epiduritis, abscess) or bone metastases responsible for nerve root or spinal cord compression, a causal relation between the neurologic deficit and the spinal anesthesia was considered likely. Neurologic deficits are uncommon after spinal anesthesia and can be produced by complications of the surgical procedure (direct nerve injury, hematoma, abscess), arachnoiditis, neurotoxicity of disinfectants or of preservatives added to solutions of anesthetic drugs, or spinal cord ischemia. Precipitating factors for spinal cord ischemia include faulty patient position during the procedure, intraoperative arterial hypotension and injection of vasoconstricting agents.

Aged↗

Bupivacaine-sparing effect of fentanyl in spinal anesthesia for cesarean delivery.

BACKGROUND AND OBJECTIVES: Visceral pain decreases in cesarean patients under spinal anesthesia when the dose of local anesthetic is increased. However, larger doses of local anesthetic are associated with higher sensory blocks. We hypothesized that the addition of fentanyl could reduce the dose of bupivacaine necessary to achieve adequate surgical anesthesia. METHODS: Two double-blinded, sequential, prospective studies were performed on 120 patients. In the preliminary study, the patients received 8, 10, or 12 mg of 0.5% hyperbaric bupivacaine intrathecally. In the second, main study, they received each bupivacaine dose with 10 microg of fentanyl. Each group consisted of 20 patients, and the groups were identified as B8, B10, B12, BF8, BF10, and BF12. Sensory and motor block, intraoperative pain defined by visual analogue scale (VAS), muscle relaxation, and side effects were assessed. We also measured the sensory and motor recovery and the onset of pain in the postanesthesia care unit (PACU). RESULTS: Maximal block level and incidence of high block (> or = T1) were higher in the 12-mg groups. There was intraoperative pain in 35% of the B8 patients and 20% of the B10 patients, but none in the B12 patients and all fentanyl groups. Incidences of other side effects were not different. The addition of fentanyl to bupivacaine significantly delayed the onset of postoperative pain and sensory recovery, but motor recovery time did not change with additional fentanyl. CONCLUSIONS: The optimal dose of hyperbaric bupivacaine to produce surgical anesthesia was 12 mg, which was accompanied by high sensory block. With the addition of 10 microg of fentanyl, the dose of bupivacaine could be reduced to 8 mg in spinal anesthesia for cesarean delivery.

Adjuvants, Anesthesia↗

[Effects of intravenous and intramuscular atropine on bradycardia during spinal anesthesia].

The effects of intravenous and intramuscular atropine on pulse rate have been studied in 40 patients undergoing gynecological surgery. Intramuscular atropine 0.5 mg was administered 30 min before induction of spinal anesthesia in 20 patients (i.m. group). Intravenous atropine 0.5 mg was administered immediately after induction of spinal anesthesia in 20 patients (i.v. group). Decrease in heart rate after spinal block was significantly less in i.v. group than in i.m. group. Although no one in i.v. group was given an additional atropine, 10% of the patients in i.m. group was given an additional atropine for bradycardia. Authors conclude that intravenous atropine has more significant effect on prevention of bradycardia during spinal anesthesia compared with intramuscular atropine.

Anesthesia, Spinal↗

Neonatal neurobehavioral tests following cesarean section under general and spinal anesthesia.

The Scanlon Group of Early Neonatal Neurobehavioral Tests (E.N.N.S.) was administered to 150 babies delivered by elective cesarean section. Fifty of the mothers were induced into general anesthesia with thiopental, 4 mg. per kilogram, and 50 with ketamine, 1 mg. per kilogram. Fifty mothers received spinal anesthesia with 6 to 8 mg. of tetracaine. All mothers receiving spinal anesthesia were given 100 per cent oxygen by a transparent face mask and all undergoing general anesthesia received N2O-O2 (6L:6L) until delivery of the baby. All mothers were healthy and all babies weighed 2,500 grams or more, were apparently normal, and had Apgar scores of 7 or more at one minute to 10 at five minutes. Spinal anesthesia was associated with the greatest percentage of high scores on both the first and second day for overall assessment, pinprick response, tone, rooting, sucking. Moro response, placing, alertness, and total decrement (habituation) scores. There was a statistically significant difference between all the scores for spinal compared to the other two groups. The scores were lowest following a thiopental induction and intermediate with ketamine although the difference did not reach statistical significance.

Adolescent↗

Spinal anesthesia attenuates myocardial ischemia during coronary artery spasm induced by intraaortic methacholine in rats.

Coronary artery spasm is not rare in patients with coronary artery disease, but the influence of regional anesthesia on spasm-induced myocardial ischemia is not known. We investigated the effects of spinal anesthesia on myocardial ischemia during coronary artery spasm in rats, and compared these with the effects of an alpha- and beta-adrenergic antagonist, and an alpha-adrenergic agonist. An intraaortic catheter was inserted via the right internal carotid artery so that the tip of the catheter was placed near the coronary ostium. An intrathecal catheter was placed at lumbar level. Coronary spasm was induced by the intraaortic injection of methacholine, and we identified the thresholds of myocardial ischemia, defined as the dose of methacholine that induced ST-segment elevation. Subsequently, the thresholds were determined after spinal anesthesia, and after the intraaortic injection of phentolamine and propranolol. The thresholds of myocardial ischemia increased significantly after intrathecal bupivacaine. In contrast, the threshold did not change after the injection of phentolamine. The thresholds increased significantly after the injection of propranolol. Methoxamine significantly decreased the threshold of ischemia. These results demonstrated that spinal anesthesia attenuated myocardial ischemia during methacholine-induced coronary spasm. This effect was equivalent to that of propranolol.

Adrenergic alpha-Agonists↗

[The blood pressure of upper and lower extremities in parturients under spinal anesthesia for cesarean section].

BACKGROUND: In clinical practice, we only measure the blood pressure of the arm during cesarean section. However, it can not accurately reflect the real image of pressure of the lower extremity in labor women. Therefore, we recorded simultaneously the arm and leg blood pressure in the term parturients undergoing cesarean section under spinal anesthesia. METHODS: After hydration with 1500 ml lactated Ringer's solution, all patients received spinal anesthesia with 2ml (0.5%) spinal heavy bupivacaine. The right hip was elevated 15 degree to insure left uterine displacement. Prior to spinal block blood pressure of the arm and leg was measured and recorded simultaneously using a Criticon Dinamap vital sign monitor 1846sx and was continued in determination every minute thereafter until uterine incision. RESULTS: We found that monitoring the lower extremity blood pressure might detect the onset of systemic hypotension more earlier and in some instances is disclosed hypotension that was not even detected by the arm cuff monitor. In addition, we found that the blood pressure in the leg was higher than that in the arm, but when hypotension occurred, it might fall even lower than that of the arm. CONCLUSIONS: We suggest that monitoring blood pressure in cesarean section under spinal anesthesia should be minute to minute for the first ten minutes and one had best monitor the lower extremity blood pressure in order to promptly detect hypotension.

Adult↗

Comparison of the effect of two different doses of 0.75% glucose-free ropivacaine for spinal anesthesia for lower limb and lower abdominal surgery.

We compared the clinical efficacy and safety of two doses of ropivacaine for spinal anesthesia in Chinese patients undergoing lower limb and lower abdominal surgery. In this randomized, open-label study, 40 patients were divided into two groups: group A received 3.5 mL (26.25 mg) of 0.75% glucose-free ropivacaine, and group B received 4.5 mL (33.75 mg). Sensory and motor blocks were assessed during and after surgery through to complete recovery. Seven standard measurements were taken: time to onset of sensory blocks; maximum sensory cephalad spread; time to maximum sensory block; maximum number of blocked segments; duration of sensory block at L3; time to onset of complete motor block; and duration until complete motor block recovery. Vital signs and any adverse effects related to spinal anesthesia were also recorded. No significant differences were found between the two groups: time to onset of sensory block at L3 in group A vs B (2.1 +/- 9.6 vs 1.7 +/- 7.3 minutes), maximum cephalad spread [T4-5 (C3-T11) vs T4 (C3-T8)], maximum number of blocked segments (18.0 +/- 3.4 vs 19.8 +/- 3.7), time to maximum sensory block (34.0 +/- 22.9 vs 26.8 +/- 17.9 minutes), duration of sensory block at L3 (251.2 +/- 34.7 vs 277.3 +/- 51.1 minutes), time to onset of complete motor block (13.4 +/- 6.4 vs 10.3 +/- 3.4 minutes), and time for complete recovery from motor block (264 +/- 52.1 vs 292.5 +/- 64.5 minutes). No significant differences in global hemodynamic changes were found during and after the operation. While shivering was more frequent in group B during the operation, the difference was not significant. Otherwise, there were no differences in adverse effects during and after surgery. We conclude that both doses of 0.75% glucose-free ropivacaine, 26.25 mg (3.5 mL) and 33.75 mg (4.5 mL), have the same efficacy and safety in Chinese patients undergoing spinal anesthesia for lower limb and lower abdominal surgery.

Abdomen↗

Low-dose bupivacaine plus fentanyl for spinal anesthesia during ambulatory inguinal herniorrhaphy: a comparison between 6 mg and 7. 5 mg of bupivacaine.

BACKGROUND: Inguinal herniorrhaphy is commonly performed as an outpatient procedure. Spinal anesthesia offers some advantages over general anesthesia in this setting. METHODS: Forty patients were randomly divided into two groups according to a double-blind protocol: Group L had spinal anesthesia with bupivacaine 6.0 mg and Group H with bupivacaine 7.5 mg; in both groups, fentanyl 25 micro g was added to the spinal anesthetic. The sensory block was measured by 'pin-prick' and the motor block was evaluated by a modified Bromage scale. RESULTS: No differences were seen in the spread, duration and regression of sensory block between the groups on the operated side. A greater number of patients required analgesics during the operation in Group L (6) compared with Group H (1) (P<0.05). The return of the modified Bromage scale to grade 0 was earlier in Group L than in Group H (P<0.05) but the time to mobilization and discharge was similar. Seven patients (17%) needed to be catheterized and two had the catheter retained overnight. Times to home discharge (median) were 350 and 445 min, respectively, in Groups L and H. Postoperatively and during the first week, visual analog pain scores, analgesic requirements and side-effects were similar between the groups. In Group H, 95% of the patients and in Group L 85% would have the same anesthetic again if operated upon for a similar procedure. CONCLUSIONS: Spinal anesthesia with bupivacaine 7.5 mg and fentanyl offers an alternative to general or local anesthesia for ambulatory inguinal herniorrhaphy. However, the long discharge times and risk for urinary retention restrict its routine use in all patients.

Adult↗

Shivering threshold during spinal anesthesia is reduced in elderly patients.

BACKGROUND: Both accidental and perioperative hypothermia are common in the elderly. The elderly are at risk because their responses to hypothermia may be delayed or less efficient than in those of younger subjects. For example, the vasoconstriction threshold during isoflurane anesthesia is approximately 1 degree C less in elderly than younger patients. However, the extent to which other cold defenses are impaired in the elderly remains unclear, especially in those older than 80 yr. Operations suitable for spinal anesthesia provided an opportunity to quantify shivering thresholds in patients of varying ages. Accordingly, the hypothesis that the shivering threshold is reduced as a function of age during spinal anesthesia was tested. METHODS: Twenty-eight ASA Physical Status 1-3 patients undergoing lower extremity orthopedic procedures were studied. Spinal anesthesia was induced without preanesthetic medication, using bupivacaine sufficient to produce a dermatomal level near T9. Electrocardiogram signals were recorded at 10-min intervals. Subsequently, an observer masked to patient age and core temperature identified the onset of sustained electromyographic artifact consistent with shivering. The tympanic membrane temperature triggering shivering identified the threshold. RESULTS: Three patients did not shiver at minimum core temperatures exceeding 36.2 degrees C. Fifteen patients aged < 80 yr (58 +/- 10 yr) shivered at 36.1 +/- 0.6 degrees C; in contrast, ten patients aged > or = 80 yr (89 +/- 7 yr) shivered at a significantly lower mean temperature, 35.2 +/- 0.7 degrees C (P = 0.002). The shivering thresholds in seven of the ten patients older than 80 yr was less than 35.5 degrees C, whereas the threshold equaled or exceeded this value in all younger patients (P = 0.0002). CONCLUSIONS: Age-dependent inhibition of autonomic thermoregulatory control in the elderly might be expected to result in hypothermia. That it usually does not suggests that behavioral regulation (e.g., increasing ambient temperature, dressing warmly) compensates for impaired autonomic control. Elderly patients undergoing spinal anesthesia, however, may be especially at risk of hypothermia because low core temperatures may not trigger protective autonomic responses. Furthermore, hypothermia in the elderly given regional anesthesia may not be perceived by the patient (who typically feels less cold after induction of the block), or by the anesthesiologist (who does not observe shivering). Consequently, temperature monitoring and management usually is indicated in these patients.

Adult↗