Bupivacaine concentrations in lumbar cerebrospinal fluid in patients with failed spinal anaesthesia.

BACKGROUND: Spinal anaesthesia (SA) has high success rates. However, inadequate block after SA has been reported even in the absence of technical problems. Various mechanisms for failed SA (FSA) have been proposed, but reports of cerebrospinal fluid (CSF) concentrations of local anaesthetics (LA) after FSA are scarce. We report lumbar CSF concentrations of bupivacaine in 20 patients in whom adequate block after subarachnoid injection failed to develop. METHODS: All patients with inadequate block after subarachnoid injection of plain bupivacaine 0.5% and in whom a second subarachnoid injection of LA was to be performed as a rescue technique were eligible for entry into this study. A CSF sample was withdrawn immediately before injection of the second dose of LA. Patients in whom failure was obviously due to technical problems or inadequate dosage were excluded. Bupivacaine concentrations were assessed with high-performance liquid chromatography. RESULTS: During the study period of 15 months, 2600 spinal anaesthetics were performed. The failure rate was 2.7% (71 patients). In 20 patients (0.77%), CSF concentrations of bupivacaine were determined, which ranged from 3.36 to 1020 microg ml(-1). CONCLUSIONS: Inadequate CSF concentration of LA is a common reason for FSA. However, in 12 of our 20 patients, concentrations were above 73 microg ml(-1), a concentration that should lead to an adequate block. In these patients, maldistribution of bupivacaine could be responsible for FSA. In view of the absence of sufficient block, despite adequate lumbar CSF concentrations of bupivacaine, concerns about neurotoxicity with repeat injections may be warranted.

Epinephrine increases the neurotoxic potential of intrathecally administered lidocaine in the rat.

BACKGROUND: Epinephrine is commonly added to lidocaine solutions to increase the duration of spinal anesthesia. Despite this common usage, the effect of epinephrine on the neurotoxic potential of this anesthetic is not known. The current experiments investigated whether adding epinephrine increases functional impairment or histologic damage induced by spinal administration of lidocaine in the rat. METHODS: Eighty rats were divided into four groups to receive an intrathecal injection of normal saline containing either 5% lidocaine, 5% lidocaine with 0.2 mg/ml of epinephrine, 0.2 mg/ml of epinephrine, or normal saline alone. Animals were assessed for persistent sensory impairment using the tail-flick test administered 4 and 7 days after infusion. Animals were then killed, and the spinal cord and nerve roots were prepared for neuropathologic evaluation. RESULTS: Rats given 5% lidocaine developed persistent sensory impairment and histologic damage, and the addition of epinephrine resulted in a further significant increase in injury. Sensory function in animals given epinephrine without anesthetic was similar to baseline and did not differ from saline. Histologic changes in animals treated with epinephrine alone did not differ significantly from saline controls. CONCLUSIONS: The neurotoxicity of intrathecally administered lidocaine is increased by the addition of epinephrine. When making clinical recommendations for maximum safe intrathecal dose of this anesthetic, one may need to consider whether the solution contains epinephrine.

Teaching the use of fiberoptic intubation in anesthetized, spontaneously breathing patients.

UNLABELLED: In patients with difficult airways, the standard of care involves fiberoptic intubation under spontaneous ventilation. However, the safety and feasibility of a fiberoptic intubation teaching program has only been documented in paralyzed and apneic patients, whereas data obtained in patients under spontaneous respiration are limited and conflicting. We evaluated 100 anesthetized patients undergoing orotracheal fiberoptic intubation. Five anesthesia residents with no prior experience in fiberoptic laryngoscopy participated in the study. In a randomized fashion, each participant tracheally intubated 10 spontaneously breathing patients (Group A: sevoflurane anesthesia via an airway endoscopy mask) and 10 paralyzed patients (Group B: total IV anesthesia with propofol, fentanyl, atracurium). Overall rate of success (96%), defined as successful intubation of the trachea within two attempts, was not different between groups. During fiberoptic intubation, Spo2 values remained >95% in Group A, whereas Spo2 decreased to <95% in two patients in Group B. Failure to pass the tube into the trachea over the bronchoscope was encountered in four patients in Group A and in no patient in Group B. Our data suggest that it is safe to teach the use of fiberoptic intubation in anesthetized, spontaneously breathing patients with normal airway anatomy. IMPLICATIONS: Fiberoptic intubation under spontaneous respiration is a well established technique for management of difficult airways. Our study demonstrates the feasibility and safety of a novice training program for fiberoptic intubation under general anesthesia, not only in paralyzed patients but also in those breathing spontaneously.

Toxicity of spinal local anaesthetics.

Recent reports of severe neurological injury after spinal anaesthesia have generated concerns about the neurotoxic potential of local anaesthetics and, in particular, of lignocaine. Further, there is an increasing body of evidence indicating that transient neurological symptoms commonly occur after uneventful lignocaine spinal anaesthesia but not after bupivacaine. Results from an epidemiological study suggest that patient positioning and outpatient status are major co-factors. Neither the dose nor the concentration of lignocaine appear to reduce the risk for transient neurological symptoms. Available data on alternative short-acting local anaesthetics with respect to transient neurological symptoms are limited and conflicting. Experimental data provide further information on factors contributing to local anaesthetic induced neurotoxicity: adrenaline significantly increases the neurotoxic effects of lignocaine in vivo, whereas the addition of glucose does not.

Gastric intramucosal pH-guided therapy in patients after elective repair of infrarenal abdominal aneurysms: is it beneficial?

OBJECTIVE: To determine if gastric intramucosal pH (pHi)-guided therapy reduces the number of complications and length of stay in the intensive care unit (ICU) or the hospital after elective repair of infrarenal abdominal aortic aneurysms. DESIGN: Prospective, randomized study. SETTING: Surgical intensive care unit (SICU) of a University Hospital. PATIENTS: Fifty-five consecutive patients randomized to group 1 (pHi-guided therapy) or to group 2 (control). INTERVENTIONS: Patients of group 1 with a pHi of lower than 7.32 were treated by means of a prospective protocol in order to increase their pHi to 7.32 or more. MEASUREMENTS AND RESULTS: pHi was determined in both groups on admission to the SICU and thereafter at 6-h intervals. In group 2, the treating physicians were blinded for the pHi values. Complications, APACHE II scores, duration of endotracheal intubation, fluid and vasoactive drug treatment, treatment with vasoactive drugs, length of stay in the SICU and in the hospital and hospital mortality were recorded. There were no differences between groups in terms of the incidence of complications. We found no differences in APACHE II scores on admission, the duration of intubation, SICU or hospital stay, or hospital mortality. In the two groups the incidence of pHi values lower than 7.32 on admission to the SICU was comparable (41% and 42% in groups 1 and 2, respectively). Patients with pHi lower than 7.32 had more major complications during SICU stay (p < 0.05), and periods more than 10 h of persistently low pHi values (< 7.32) were associated with a higher incidence of SICU complications (p < 0.01). CONCLUSIONS: Low pHi values (< 7.32) and their persistence are predictors of major complications. Treatment to elevate low pHi values does not improve postoperative outcome. Based on these data, we cannot recommend the routine use of gastric tonometers for pHi-guided therapy in these patients. Further studies are warranted to determine adequate treatment of low pHi values that results in beneficial effects on the patient's postoperative course and outcome.

Propofol reduces succinylcholine induced increase of masseter muscle tone.

PURPOSE: Succinylcholine is known to increase the tone of the masseter muscles. As excessive jaw tension may complicate rapid sequence induction, we investigated three induction techniques, all including the use of succinylcholine, with respect to masseter muscle tone, neuromuscular blockade, intubation conditions, and time course of intubation. METHODS: Sixty adult patients were allocated to one of three induction groups: Group THIO received 5 mg.kg-1 thiopentone, Group THIO/ATR received 5 mg.kg-1 thiopentone plus 0.05 mg.kg-1 atracurium for precurarization, and Group PROP received 2.5 mg.kg-1 propofol. All patients received 3 micrograms.kg-1 fentanyl and 1.5 mg.kg-1 succinylcholine. Time for induction of anaesthesia was recorded, and, after inserting a Grass Force Transducer between upper and lower incisors, jaw tone and the time course of jaw tension was recorded before and after the administration of succinylcholine. RESULTS: No differences in the onset of sleep were observed among the three groups (Group THIO 33 +/- 2 sec: THIO/ATR 30 +/- 2 sec: PROP 35 +/- 2 sec, mean +/- SE). Masseter preloads following induction of anaesthesia were similar in all three groups (THIO 16.4 +/- 2.1 N: THIO/ATR 15.1 +/- 2.0 N: PROP 12.7 +/- 1.6 N). However, after administration of succinylcholine, the increase in masseter tone was less in Groups PROP (5.0 +/- 1.1 N) and THIO/ATR (6.4 +/- 2.1 N) than in Group THIO (12.4 +/- 3.0 N; P < 0.05). CONCLUSION: Jaw tension after administration of succinylcholine is influenced by the choice of induction agent. The increase of masseter muscle tone is lower following propofol or thiopentone/atracurium induction than with thiopentone alone.

Lidocaine toxicity in primary afferent neurons from the rat.

Evidence from both clinical studies and animal models suggests that the local anesthetic, lidocaine, is neurotoxic. However, the mechanism of lidocaine-induced toxicity is unknown. To test the hypothesis that toxicity results from a direct action of lidocaine on sensory neurons we performed in vitro histological, electrophysiological and fluorometrical experiments on isolated dorsal root ganglion (DRG) neurons from the adult rat. We observed lidocaine-induced neuronal death after a 4-min exposure of DRG neurons to lidocaine concentrations as low as 30 mM. Consistent with an excitotoxic mechanism of neurotoxicity, lidocaine depolarized DRG neurons at concentrations that induced cell death (EC50 = 14 mM). This depolarization occurred even though voltage-gated sodium currents and action potentials were blocked effectively at much lower concentrations. (EC50 values for lidocaine-induced block of tetrodotoxin-sensitive and -resistant voltage-gated sodium currents were 41 and 101 microM, respectively.) At concentrations similar to those that induced neurotoxicity and depolarization, lidocaine also induced an increase in the concentration of intracellular Ca++ ions ([Ca++]i; EC50 = 21 mM) via Ca++ influx through the plasma membrane as well as release of Ca++ from intracellular stores. Finally, lidocaine-induced neurotoxicity was attenuated significantly when lidocaine was applied in the presence of nominally Ca(++)-free bath solution to DRG neurons preloaded with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Our results indicate: 1) that lidocaine is neurotoxic to sensory neurons; 2) that toxicity results from a direct action on sensory neurons; and 3) that a lidocaine-induced increase in intracellular Ca++ is a mechanism of lidocaine-induced neuronal toxicity.

Combined effect of patient variables on sensory level after spinal 0.5% plain bupivacaine.

BACKGROUND: The combined effect of age, weight, height, and vertebral column length (VCL) on the distribution of isobaric 0.5% bupivacaine within the subarachnoid space is unclear. The aim of the present study was to evaluate the combined influence of these patient variables on the upper sensory level and on its predictability. METHODS: In 100 patients who were above the age of 49 years, the age, weight, height, VCL, body surface (BS), and body mass index (BMI) were noted. Spinal puncture and subarachnoid drug administration were standardized. Cephalad spread of spinal anaesthesia (SA) was assessed by loss of temperature sensation and pinprick discrimination 15, 30, 60, 90, and 120 min following subarachnoid injection of 18 mg of plain 0.5% bupivacaine. Linear regression analysis was performed for each of the patient variables and the cephalad segmental spread of anaesthesia. Multiple regression analysis was used to test for combined correlation between patient variables and the sensory level of SA. RESULTS: No linear correlation was found between the patient variables and the sensory level of anaesthesia. In contrast, multiple regression analysis revealed that age (P<0.01), weight (P<0.05), and height (P<0.01) significantly contributed to the spread of anaesthesia. A squared multiple comparison coefficient between 0.10 and 0.21, however, is an indication that the predictive value of the combined variables remained rather low. CONCLUSION: Multiple regression analysis revealed that age, weight, and height significantly correlated with the sensory level after subarachnoid injection of plain bupivacaine. The low predictive value suggests that patient factors other than age, weight, or height add to cephalad spread of SA.

Preoperative anxiolysis with minimal sedation in elderly patients: bromazepam or clorazepate-dipotassium?

BACKGROUND: In elderly patients undergoing ophthalmic surgery the loss of co-operation due to over-sedation, induced by drugs given preoperatively, may jeopardise the success of microsurgery performed under regional anaesthesia. The aim of this study was to compare the psychotropic effects of bromazepam and clorazepate-dipotassium, two benzodiazepines with predominantly anxiolytic and only weak sedative action. METHODS: A randomised, placebo-controlled, double-blind study was designed to include 60 patients, ASA physical status II-III, older than 60 years scheduled for ophthalmic surgery under regional anaesthesia. The patients were randomised to receive either bromazepam (3 mg) or clorazepate-dipotassium (20 mg) or placebo. The study drugs were given at 10 p.m. the night before surgery and 90 min before surgery. Using the State-Trait Anxiety Inventory (STAI), the patient's anxiety was assessed at the end of the preoperative visit, on the next morning before the study drug was given and on arrival at the operating theatre. RESULTS: Bromazepam induced a marked anxiolytic effect as documented by a significant reduction in the STAI State values after both applications (P<0.01). Clorazepate did not differ from placebo at any evaluation time with regard to the STAI and haemodynamic values. Sedative effects and oxygen saturation (SpO2) were comparable in all groups. CONCLUSION: Bromazepam is superior to clorazepate in its anxiolytic action and suitable as preoperative medication in the elderly patient because of lack of overt sedative effects.

Transient neurologic symptoms after spinal anesthesia: a lower incidence with prilocaine and bupivacaine than with lidocaine.

BACKGROUND: Recent evidence suggests that transient neurologic symptoms (TNSs) frequently follow lidocaine spinal anesthesia but are infrequent with bupivacaine. However, identification of a short-acting local anesthetic to substitute for lidocaine for brief surgical procedures remains an important goal. Prilocaine is an amide local anesthetic with a duration of action similar to that of lidocaine. Accordingly, the present, prospective double-blind study compares prilocaine with lidocaine and bupivacaine with respect to duration of action and relative risk of TNSs. METHODS: Ninety patients classified as American Society of Anesthesiologists physical status I or II who were scheduled for short gynecologic procedures under spinal anesthesia were randomly allocated to receive 2.5 ml 2% lidocaine in 7.5% glucose, 2% prilocaine in 7.5% glucose, or 0.5% bupivacaine in 7.5% glucose. All solutions were provided in blinded vials by the hospital pharmacy. Details of spinal puncture, extension and regression of spinal block, and the times to reach discharge criteria were noted. In the evening of postoperative day 1, patients were evaluated for TNSs by a physician unaware of the drug administered and the details of the anesthetic procedure. RESULTS: Nine of 30 patients receiving lidocaine experienced TNSs, 1 of 30 patients receiving prilocaine (P = 0.03) had them, and none of 30 patients receiving bupivacaine had TNSs. Times to ambulate and to void were similar after lidocaine and prilocaine (150 vs. 165 min and 238 vs. 253 min, respectively) but prolonged after bupivacaine (200 and 299 min, respectively; P < 0.05). CONCLUSIONS: Prilocaine may be preferable to lidocaine for short surgical procedures because it has a similar duration of action but a lower incidence of TNSs.

[Perioperative gastrointestinal ischemia in abdominal aortic aneurysm operations]. / Perioperative gastrointestinale Ischämien bei abdominalen Aortenaneurysma-Operationen.

QUESTIONS UNDER STUDY: Surgery of abdominal aortic aneurysms involves a high risk of postoperative complications. It has been suggested that the incidence of postoperative complications is related to the development of gastrointestinal acidotic episodes of the mucosa. The goal of this study was, therefore, to determine the incidence of gastrointestinal acidotic episodes during repair of abdominal aortic aneurysms, and to test the hypothesis that these episodes predict an adverse postoperative course. METHODS: In 49 consecutive patients undergoing elective surgery for repair of an abdominal aneurysm, intramucosal gastric pH (pHi) was measured perioperatively. The length of the surgical procedure, perioperative intravenous fluid intake, use of vasoactive drugs, APACHE-II scores, days with an endotracheal tube in place, days of intensive care and major postoperative complications were prospectively assessed. The patients were assigned to either a group with a pHi > or = 7.35 or a group with pHi < 7.35 measured towards the end of the surgical procedure, and then compared. RESULTS: The pHi decreased from 7.42 +/- 0.09 after induction of anesthesia to 7.37 +/- 0.07 (p < 0.05) during clamping of the aorta, and continued to decrease to 7.34 +/- 0.08 (p < 0.001) towards the end of surgery and on admission to the surgical intensive care unit (mean +/- standard deviation). The percentage of patients with pHi < 7.35 increased from 10% at the beginning of the operation to 55% on admission to the intensive care unit (p < 0.0001). There was no difference in the postoperative course between patients with pHi > or = 7.35 and those with pHi < 7.35 measured after declamping of the aorta. Patients who had a major complication during their stay in the intensive care unit had lower perioperative pHi values than patients without complications (p < 0.001). CONCLUSIONS: Perioperative gastrointestinal acidotic episodes of the mucosa are common during repair of abdominal aortic aneurysms. The perioperative course, however, is not influenced by these acidotic episodes, despite the fact that patients with complications during their stay in the intensive care unit had lower perioperative pHi values. The routine use of pHi measurements during elective surgery of abdominal aortic aneurysms, therefore, is not justified.

Teaching the use of fiberoptic intubation for children older than two years of age.

UNLABELLED: In 144 anesthetized children aged 2-9 yrs, the safety and feasibility of orotracheal fiberoptic intubation, with and without an airway endoscopy mask, were assessed and compared with laryngoscopic intubation. Eight anesthesia residents with experience in adult fiberoptic intubation, but who were beginners in pediatric anesthesia, participated in this study. In a randomized fashion, each resident intubated 18 children (6 in each group). The time (mean +/- SD) to achieve successful intubation was different for laryngoscopic and fiberoptic intubation (34 +/- 17 s and 80 +/- 39 s, respectively; P < 0.001). The use of the airway endoscopy mask further prolonged fiberoptic intubation (167 +/- 121 s, P < 0.001). Spo2 values remained >95% in all patients during conventional laryngoscopy and fiberoptic laryngoscopy with a mask, whereas Spo2 decreased below 95% in 2 of the 48 patients during fiberoptic intubation without a mask. Both patients promptly recovered during ventilation via a face mask. We conclude that teaching the use of fiberoptic intubation in healthy, anesthetized children aged 2-9 yrs is safe and feasible. IMPLICATIONS: Fiberoptic intubation is a valuable technique of airway management. We studied the feasibility and safety of a training program that could be used for children more than 2 yrs old. This study demonstrates that fiberoptic intubation can be effectively practiced in pediatric patients without increased risk of side effects.

A similar incidence of transient neurologic symptoms after spinal anesthesia with 2% and 5% lidocaine.

Recent reports suggest that transient neurologic symptoms are common after spinal anesthesia with 5% lidocaine. To determine whether reducing the anesthetic concentration might decrease the incidence of symptoms, 50 ASA class I or II patients undergoing brief gynecologic procedures under spinal anesthesia were randomly allocated to receive 1 mg/kg of either 5% or 2% lidocaine in 7.5% glucose. Patients were evaluated on the first postoperative day by an anesthesiologist who was unaware of the solution administered or the details of the anesthetic procedure. Symptoms suggestive of transient radicular irritation were observed in 8 patients (32%) receiving 5% lidocaine, and in 10 patients (40%) receiving 2% lidocaine (NS). These results confirm our previous findings that transient neurologic symptoms may occur in up to one third of the patients receiving 5% lidocaine, and indicate that a modest reduction in lidocaine concentration does not reduce risk.

Transient radicular irritation after single subarachnoid injection of isobaric 2% lignocaine for spinal anaesthesia.

Several cases have been reported recently in which symptoms suggestive of transient radicular irritation occurred following the use of hyperbaric 5% lignocaine for spinal anaesthesia. We report on three patients in whom we observed similar symptoms attributable to this kind of radicular irritation following uneventful spinal anaesthesia using isobaric 2% lignocaine. All three patients underwent minor gynaecological procedures and developed burning pains in the buttocks within 24 h of surgery. The long-term outcome was not clear for all the patients, but in at least one the pain disappeared.

Intravenous sedation for retrobulbar injection and eye surgery: diazepam and/or propofol?

Principle goals of sedation for eye surgery are to provide patient comfort and to allow the patient to stay calm during both retrobulbar injection and surgery. Insufficient sedation may not prevent the patient from moving during retrobulbar injection, whereas very deep sedation may result in respiratory complications during surgery. The aim of the present study was to evaluate the effectiveness and suitability of a combination of diazepam and propofol for sedation for both application of retrobulbar block and subsequent elective eye surgery. One-hundred and fifty patients were randomly allocated to receive either diazepam, propofol or a combination of both drugs before retrobulbar injection. Tolerance of retrobulbar injection and comfort during the surgical procedure were assessed by comfort scores using a nominal analogue scale between 1 (worst possible condition) and 6 (best conceivable condition). Side effects related to sedation were recorded. The combination of diazepam and propofol resulted in the highest comfort scores for both retrobulbar block (5.3 +/- 0.3) and the surgical procedure (5.4 +/- 0.4). Diazepam alone did not produce adequate sedation for retrobulbar block (3.1 +/- 0.3), whereas comfort scores during surgery were significantly higher (5.3 +/- 0.3) compared to propofol alone (3.6 +/- 0.4). No severe side effects induced by sedation were noted in any of the study groups. The combination of diazepam and propofol proved able to provide a reliable degree of sedation with minimal side effects for both retrobulbar block and surgery. The combination was clearly superior to the sedation induced by propofol or diazepam alone.

Transient neurologic symptoms after spinal anesthesia.

We recently reported several cases consistent with transient radicular irritation after spinal anesthesia with hyperbaric 5% lidocaine. The present prospective, blind, nonrandomized study was performed to determine the incidence of these transient neurologic symptoms and to identify factors that might be associated with their occurrence. We studied 270 patients scheduled for gynecologic or obstetric procedures under spinal anesthesia. For spinal anesthesia, either 5% lidocaine in 7.5% glucose or 0.5% bupivacaine in 8.5% glucose was used. Patients were evaluated on postoperative day 3 by a quality assurance nurse who was unaware of the drug given or details of the anesthetic technique. Transient neurologic symptoms were observed in 37% of patients receiving 5% lidocaine, whereas only one patient receiving 0.5% bupivacaine had transient hypesthesia of the lateral aspect of the right foot. These results suggest that symptoms were the result of a specific drug effect. However, because of the limitations of the study one cannot conclude that lidocaine per se was the cause.

Perioperative administration of caffeine tablets for prevention of postoperative headaches.

Interruption of daily caffeine consumption can cause caffeine withdrawal headache. As headache ranks among the most frequent minor postoperative sequelae, the impact of perioperative substitution of caffeine on the incidence of postoperative headache was evaluated. Forty patients undergoing minor surgical procedures with general anaesthesia were randomly allocated to receive either placebo or caffeine tablets at a dosage equal to their individual average daily caffeine consumption. Daily dietary intake was calculated based on an average week-day consumption using conversion factor from previously published sources. The patients were instructed at the preoperative visit to abstain from all external sources of caffeine. Compliance with these dietary restrictions was verified by blood samples obtained immediately before the surgical procedure and on postoperative day 1. The patients were assessed for headache using a standardised checklist immediately before induction of anaesthesia, on the evening of the day of surgery and on the morning of postoperative day 1. Ten patients (50%) who received placebo reported headaches, which persisted in seven patients (35%) until the next day. No patient receiving caffeine substitution therapy reported headache following surgery, and only one complained of headache on postoperative day 1. We suggest that the prophylactic administration of caffeine tablets might be considered for surgical patients who are accustomed to a high daily intake of caffeine.

Hyperosmolarity does not contribute to transient radicular irritation after spinal anesthesia with hyperbaric 5% lidocaine.

BACKGROUND AND OBJECTIVES: In addition to major neurologic injury, local anesthesia toxicity may also include less severe but more common neurologic side effects. The authors recently observed symptoms suggestive of transient radicular irritation in one third of patients after spinal anesthesia with hyperbaric 5% lidocaine, whereas evidence of neurologic symptoms was lacking with hyperbaric 0.5% bupivacaine. The purpose of this prospective double-blinded study was to evaluate if the high osmolarity of hyperbaric 5% lidocaine solution might contribute to the development of transient radicular irritation. METHODS: Forty-four patients undergoing brief gynecologic procedures under spinal anesthesia were randomly allocated to receive 1.5 mL of one of three study drugs: 5% lidocaine in 7.5% dextrose (drug A), 0.5% bupivacaine in 8.25% dextrose (drug B), or 5% lidocaine in 2.7% dextrose (drug C). Drug C was prepared by the pharmacy (University Hospital, Basel, Switzerland) with an osmolarity similar to that of drug B. Drugs A and B were commercially available. Patients were evaluated on postoperative day 1 for symptoms of transient radicular irritation by an anesthesiologist who was unaware of the drug given or details of the anesthetic technique. RESULTS: Symptoms suggestive of transient radicular irritation were observed with a similar high incidence in patients receiving both lidocaine preparations, but in no patient receiving hyperbaric 0.5% bupivacaine (P < .01). CONCLUSIONS: The results suggest that transient radicular irritation did not result from the marked hyperosmolarity of the hyperbaric 5% lidocaine. However, because lidocaine and bupivacaine were not administered at equipotent dosages, the relative potential for both drugs to induce transient radicular irritation remains to be determined.