Spinal anesthesia with hypobaric bupivacaine for knee arthroscopies: effect of posture on motor block.

BACKGROUND AND OBJECTIVES: The clinical impact of patient positioning on motor block during unilateral spinal anesthesia was the focus of our study. It was assumed that a 45 degrees rotation toward the prone position would minimize blocking the ventral motor roots compared with using the conventional lateral decubitus position. METHODS: Spinal anesthesia with 3.4 mL of hypobaric 0.18% bupivacaine via a 27-gauge Whitacre needle was administered to 70 patients undergoing knee arthroscopy. The patients were kept either in a lateral decubitus position (group I) or rotated approximately 45 degrees toward the prone position (group II). No prophylactic vasopressors or infusions were used. The intensity of motor block (modified Bromage scale) was assessed for both the operative and the contralateral side. RESULTS: The patients in group I had a slightly more pronounced motor block, but statistical significance could be shown only 20 minutes following the block. There was no statistical difference between the groups in the need of additional analgesics during the operation. None of the patients needed general anesthesia. The hemodynamics were stable and none of the patients developed postspinal headache or backache. CONCLUSIONS: The position of the patient affects the spread of the spinal anesthesia when clearly hypobaric agents are used. However, this small modification in positioning of the patient did not lead to a clinically meaningful difference in the spread of the motor block.

A low dose of plain or hyperbaric bupivacaine for unilateral spinal anesthesia.

BACKGROUND AND OBJECTIVES: Unilateral spinal anesthesia may be advantageous, especially in the outpatient setting. A low dose of anesthetic solution, pencil-point needle, low speed of intrathecal injection, and a lateral position have been reported to facilitate the production of unilateral distribution of spinal anesthesia. We compared the effects of plain and hyperbaric bupivacaine in attempting to obtain a unilateral spinal anesthesia for patients undergoing outpatient knee arthroscopy. METHODS: Sixty patients were randomly allocated to 2 groups to receive either 1.2 mL (6 mg) of plain 0.5% bupivacaine (group 1; n = 30) or 1.2 mL (6 mg) of hyperbaric 0.5% bupivacaine in 8% glucose (group 2; n = 30). Drugs were administered at the L2-3 interspace with the patient in the lateral position. Patients remained in this position for 20 minutes before being turned supine for the operation. Spinal block was assessed by pinprick and modified Bromage scale and compared between the operated and nonoperated sides. RESULTS: There was a significant difference between the operated and nonoperated side in both groups at all testing times, but a more unilateral spinal block was achieved with hyperbaric bupivacaine. Unilateral motor and sensory block was observed in 25 patients in group 2 (83%) and in 11 patients in group 1 (37%) (P <.01). The hemodynamic changes were minimal, since hypotension occurred only in 5.0% and bradycardia in 1.7% of all patients. CONCLUSION: In conclusion, the spinal anesthesia in both groups are suitable alternatives for adult outpatient knee arthroscopies, but hyperbaric bupivacaine provides us with a more unilateral spinal block.

The use of bupivacaine and fentanyl for spinal anesthesia for urologic surgery.

We evaluated the effect of 25 microg of fentanyl added to bupivacaine on sensory and motor block. By using a double-blinded study design, 80 men undergoing urologic surgery were randomized into the following four groups: Group I, bupivacaine 10 mg; Group II, bupivacaine 10 mg + fentanyl 25 microg; Group III, bupivacaine 7.5 mg + fentanyl 25 microg; Group IV, bupivacaine 5 mg + fentanyl 25 microg. The final volume of intrathecal injectate was adjusted to 2. 5 mL with sterile distilled water. Spinal anesthesia was administered with the 27-gauge Whitacre needle at the L2-3 interspace with the patient in the sitting position. Neural block was assessed by using pinprick and a modified Bromage scale. The degree of motor block was more profound in Group II compared with Group I at the end of operation. In Group IV, there was no motor block at the end of operation in any of the patients. The median level of the upper limit of the sensory block was higher than T(7) in all groups before the start of surgery. The addition of 25 microg of fentanyl to 5 mg of bupivacaine resulted in short-acting motor block. When 25 microg of fentanyl was added to 10 mg of bupivacaine, it increased the intensity and duration of motor block. Only 5 (6. 3%) of the patients needed supplemental analgesia during the operation. ¿abs¿

Low-dose bupivacaine: a comparison of hypobaric and near isobaric solutions for arthroscopic surgery of the knee.

The results of studies on the effect of volume, concentration or total dose of local anaesthetic on the spread of spinal anaesthesia are inconclusive. Most support the assumption that the total dosage is more important than the volume. We compared low-dose bupivacaine (6 mg) in 0.5% and 0.18% solutions as sole anaesthetic to achieve predominantly unilateral spinal anaesthesia for knee arthroscopy. Sixty patients were randomly allocated to two groups to receive either 1.2 ml 0.5% bupivacaine (6 mg) (n = 30) or 3.4 ml 0.18% hypobaric bupivacaine (6.1 mg) (n = 30). Drugs were administered at the L3-4 interspace with the patient in the lateral position. Patients remained in this position for 20 min before being turned supine for the operation. Spinal block was assessed by pinprick and modified Bromage scale and compared between the operated and nonoperated sides. No significant changes were found in the spread or duration of sensory or motor block (p > 0.05). The haemodynamic changes were also similar between the groups. The same pinprick level of analgesia, degree of motor block and duration of spinal anaesthesia was obtained with bupivacaine (6 mg) in low (1.2 ml) or high (3.4 ml) volumes.

Restricted spinal anaesthesia for ambulatory surgery: a pilot study.

The increasing use of ambulatory surgery requires methods of anaesthesia that allow patients to be discharged soon after the operation is completed. Spinal anaesthesia is usually simple and quick, and the incidence of post-spinal headache has been reduced by using non-cutting small-gauge needles. Limiting the spread of spinal anaesthesia, as long as it still provides analgesia for surgery, should reduce the haemodynamic effects and speed recovery. Restricted spinal anaesthesia, intended to be unilateral using 0.18% hypobaric bupivacaine via a 25G or 27G Whitacre unidirectional needle, was compared with epidural anaesthesia (using a mixture of lignocaine and prilocaine) in 64 matched-pair patients undergoing ambulatory arthroscopy. Motor blockade, assessed for the specific myotomes L2 to S1, was significantly more unilateral in the spinal group. Two patients in the spinal group and nine patients in the epidural group were treated for hypotension (P < 0.05). One patient in the spinal group developed a post-spinal headache. One patient in the epidural group rated the anaesthesia poor.

A low-dose hypobaric bupivacaine spinal anesthesia for knee arthroscopies.

BACKGROUND AND OBJECTIVES: Ambulatory surgery requires anesthesia methods that allow rapid recovery and safe discharge of the patient. Spinal anesthesia is easy and quick to perform, and the use of noncutting small gauge needles reduces the occurrence of postdural puncture headache. For minimal hemodynamic consequences and faster recovery and discharge it would be optimal to limit the spread of spinal anesthesia only to the area which is necessary for surgery. In this study, the possibility in achieving unilateral spinal anesthesia with 0.18% hypobaric bupivacaine was studied. METHODS: Spinal anesthesia with 3.4 mL of hypobaric 0.18% bupivacaine (6.12 mg), without any intravenous infusion or prophylactic vasopressors, was administered with 27-gauge Whitacre unidirectional needle to 70 ASA I and II patients undergoing knee arthroscopies. The patients were allocated randomly to be kept either 20 (group I) or 30 (group II) minutes in the lateral position operation side uppermost. Sensory and motor block (pinprick/modified Bromage scale) were compared between the operation and the contralateral side. RESULTS: The motor and sensory block between operation and contralateral sides were significantly different at all testing times in both groups (P < .001, Mann-Whitney U test). The motor block was completely unilateral in 14 patients (39%) in group I and in 22 patients (65%) in group II. The hemodynamics were stable in all 70 patients. CONCLUSIONS: Approximately three and a half milliliters hypobaric 0.18% bupivacaine (6.12 mg) provides a predominantly unilateral spinal block. Thirty minutes spent in the lateral position does not provide benefits over 20 minutes. The main advantages of our method are the hemodynamic stability and the patient satisfaction.

Inverse correlation between the peak venous serum concentration of bupivacaine and the weight of the patient during interscalene brachial plexus block.

Thirty-five adult patients with rheumatoid arthritis received for 36 interscalene brachial plexus blocks a standard dose of bupivacaine 200 mg, regardless of the weight (range 39.2-102.5 kg) of the patient. The peak venous serum concentrations (Cmax) of bupivacaine, measured by HPLC, were in the range 0.82-4.30 mg litre-1; there were no signs of toxicity. There was a very significant inverse correlation between the Cmax of bupivacaine and the weight of the patient (r = -0.5922; t = -4.285; P = 0.0001, Pearson's test). In spite of the correlation, only 35.1% of the total variance could be explained by regression. Thus weight had little influence on Cmax under interscalene brachial plexus block.

Lack of effect of cimetidine on the pharmacokinetics of bupivacaine in healthy subjects.

1. The possibility of a pharmacokinetic interaction between the H2-receptor antagonist cimetidine and the long-acting local anaesthetic agent bupivacaine was studied in seven healthy, non-smoking volunteers. 2. The study consisted of two sessions at a minimum interval of 4 days. In a randomized, crossover fashion, the volunteers received bupivacaine HCl 1.4 mg kg-1 by i.m. injection at two occasions, once after no premedication, and once after two oral doses of 400 mg cimetidine. The concentrations of bupivacaine and its metabolites, 4'-hydroxybupivacaine and desbutylbupivacaine, were assayed by h.p.l.c., in serum up to 8 h and in urine fractions up to 24 h. 3. No influence of cimetidine on the pharmacokinetics of bupivacaine or on the serum cumulation of urinary recovery of its measured metabolites was detected. 4. These data suggest that cimetidine may be used safely as a premedication before local anaesthetic procedures with bupivacaine.

Bupivacaine with and without adrenaline in interscalene brachial plexus blockade. Studies in patients with rheumatoid arthritis.

The action of adrenaline on the pharmacokinetics of bupivacaine has been tested during two successive interscalene brachial plexus blocks in 10 patients with rheumatoid arthritis. The mean venous serum Cmax of bupivacaine after using it with or without adrenaline 1:200000 were 1.49 +/- 0.41 micrograms ml-1 and 2.46 +/- 0.85 micrograms ml-1, respectively. In spite of relatively high total serum concentrations, we could not detect any evidence of toxicity from bupivacaine. Significant tachycardia was seen after bupivacaine with adrenaline, but systolic and diastolic arterial pressures did not change significantly in any session. Marked subjective side effects were noticed only after bupivacaine with adrenaline (shivering twice and palpitations once). The serum protein bound fraction of bupivacaine was higher in rheumatic patients than in our healthy controls: 97.1 +/- 2.4% and 91.3 +/- 3.6%, respectively. Thus bupivacaine as a local anaesthetic agent seems to be even safer in patients with rheumatoid arthritis than in normal healthy volunteers, because of lower free fraction in the former.

Ethanol and the absorption of oral penicillin in man.

The effect of alcohol on the pharmacokinetics of phenoxymethylpenicillin was studied in six healthy volunteers. Ethanol had no influence on peak penicillin serum concentrations, times of the penicillin peaks, elimination half-lives (t1/2), AUC0-8h values and 24-h urinary excretion.

Simultaneous determination of bupivacaine and its two metabolites, desbutyl- and 4'-hydroxybupivacaine, in human serum and urine.

A sensitive and selective high-performance liquid chromatographic (HPLC) method for the determination of bupivacaine and its two metabolites, desbutyl- and 4'-hydroxybupivacaine, in human serum and urine is described. Bupivacaine, both metabolites and the internal standard, etidocaine, are extracted with diethyl ether and then back-extracted into an acidic aqueous phase. After subsequent extraction into diethyl ether, evaporation and reconstitution in the mobile phase, bupivacaine and the metabolites are determined by HPLC using a reversed-phase C8 column with tetrahydrofuran-potassium phosphate buffer (8:92, v/v, pH 2.4) as the mobile phase. The sensitivity of the method is 10 micrograms/l for bupivacaine and both metabolites and the extraction efficiencies are 95, 54 and 92% for bupivacaine and desbutyl- and 4'-hydroxybupivacaine, respectively. The reproducibility of the method is good, the coefficients of variation varying between 1.8 and 7.4% in the concentration range 0.10-2.00 mg/l. The procedure was applied to human serum and urine samples from two elderly women who had been operated on under epidural analgesia (plain bupivacaine, 1.5 mg/kg) because of uterine prolapse.

Pharmacokinetics and clinical effects of scopolamine in caesarean section patients.

A new method (ELISA) was used to evaluate the pharmacokinetics of scopolamine following intravenous (0.005 mg/kg), intramuscular (0.01 mg/kg), and oropharyngeal (0.035 mg/kg) administration of the drug to pregnant patients anaesthetized for caesarean section. After intravenous (N = 4) the drug fast disappeared from the circulation with a half-life of about 5 min., and the serum levels generally were measurable up to 3 hours, mean elimination half-life was 1.85 hours. A fast absorption was found after intramuscular injection, tmax = 10 min. (N = 4), and the drug had a clinically significant oropharyngeal absorption as well, tmax was around 1 hour (N = 6). The intramuscular and oropharyngeal, but not the intravenous, administrations produced a marked postoperative sedative and amnesic effects. All three administration ways caused a significant antisecretory action.

Disposition of nomifensine after acute and prolonged dosing.

The pharmacokinetics of nomifensine were studied after single oral and intravenous doses. The effect of prolonged oral dosing on the pharmacokinetics of nomifensine was also evaluated. Nomifensine was rapidly absorbed from the gastrointestinal tract. The peak concentration of free nomifensine (0.18 mumol/L) was reached at 1.13 hours after dosing. The highest concentration after the intravenous dose was 1.21 mumol/L. The elimination t1/2 after a single dose was about 4 hours regardless of the route of administration. Nomifensine was extensively distributed in body fluids and tissues, with an apparent volume of distribution of 8.69 L/kg. The AUC of free nomifensine after oral dosing was only 26.5% of that after intravenous infusion. Absorption from the gastrointestinal tract was complete, and the AUCs of total nomifensine were equal after all treatments. The main reason for limited bioavailability seems to be extensive first-pass metabolism during the absorption process. The AUC of free nomifensine decreased substantially (from 0.78 to 0.32 hr X mumol/L) and the elimination t1/2 was shortened (from 4.39 to 2.11 hours) after a 2-week dosing period. These effects suggest marked induction of the metabolizing enzymes. An increase in nomifensine dosage may be needed in some patients to maintain a full therapeutic effect.

High-performance liquid chromatographic determination of bupivacaine in human serum.

A selective high-performance liquid chromatographic method for the determination of bupivacaine in human serum is described. The technique is based on a single extraction of the drug from alkalinized serum with a mixture of hexane-isopropanol-chloroform. Desmethyldoxepin is used as internal standard. The chromatographic system consists of a home-packed Nucleosil C8 (10 microns) column; the mobile phase is acetonitrile--0.05 M potassium phosphate buffer (pH 3.3) (28:72, v/v). The method can accurately measure serum bupivacaine concentrations down to 20 micrograms/l using 500 microliters of sample. The coefficient of variation for intra-assay variability of bupivacaine is 2.1% (n = 13) and for inter-assay variability of bupivacaine 5.7% (n = 11) at 1.00 mg/l. The calibration graph is linear over the range 0.02-5.00 mg/l and the extraction efficiency is 91.8 +/- 3.8% (+/- S.D., n = 7). The method is accurate and sensitive for both clinical and pharmacokinetic studies on bupivacaine in man. The method is applied to the analysis of serum samples obtained from orthopaedic patients during both spinal and epidural analgesia.