Effect of chronic bupivacaine infusion on seizure threshold to bupivacaine

Thirty rats were pretreated with a continuous infusion of bupivacaine or placebo. On the fourth day the acute seizure threshold to bupivacaine was determined for both groups. The seizure dose, blood and brain concentration of bupivacaine showed no difference between the groups. The tachyphylaxis seen clinically when bupivacaine is used for a regional nerve blockade does not seem to evolve for the CNS-effects.     

Comparison of bupivacaine and alkalinized bupivacaine in brachial plexus anesthesia

To define the effect of alkalinization of bupivacaine 0.5% in subclavian perivascular brachial plexus blockade, the time to onset, time to peak effect, and 6-hour regression of sensory and motor blockade were determined. Sixty physical status ASA I and II patients were randomly allocated to one of two groups and a double-blind design was used: group I (n = 30) received bupivacaine 0.5% (pH, 5.5) 3 mg/kg, while group II (n = 30) received alkalinized bupivacaine 0.5% (pH, 7.05-7.15) 3 mg/kg. Onset and regression of sensory blockade were determined by pinprick in the C4-T2 skin dermatomes, while motor blockade was assessed using a scheme of proximal to distal muscle group paralysis. Time to onset of sensory blockade (group I, 4.0 +/- 1.2 min; group II, 3.6 +/- 0.9 min) and time to peak sensory effect (group I, 17.7 +/- 1.8 min; group II, 16.3 +/- 1.8 min) did not differ significantly between the groups. Similarly, no difference in time to onset of motor blockade (group I, 6.9 +/- 1.7 min; group II, 6.3 +/- 1.5 min) or time to peak motor effect (group I, 18.1 +/- 1.9 min; group II, 15.1 +/- 1.9 min) was observed. Regression of postoperative sensory and motor blockade was similar in both groups. It is concluded that alkalinization of bupivacaine 0.5% solutions does not confer any added clinical advantage in subclavian perivascular brachial plexus blockade when compared with commercially available bupivacaine.     

The clinical effectiveness of epidural bupivacaine, bupivacaine with lidocaine, and bupivacaine with fentanyl for labor analgesia

STUDY OBJECTIVE: To examine the efficacy of bupivacaine alone and in combination with lidocaine or fentanyl for epidural analgesia during labor. DESIGN: Randomized, single-blind study. SETTING: Labor and delivery unit at a university medical center. PATIENTS: Forty-five primiparas requesting epidural analgesia. INTERVENTIONS: Following epidural placement at L3-4 interspace, patients received either bupivacaine 0.5% (Group 1, n = 15), bupivacaine 0.25% with lidocaine 1% (Group 2, n = 15), or bupivacaine 0.5% with fentanyl 50 micrograms in 10 ml of saline (Group 3, n = 15). Patients in Groups 1 and 2 received 6 to 10 ml of local anesthetic depending on patient height, while patients in Group 3 received 5 ml of local anesthetic plus 50 micrograms of fentanyl in 10 ml of saline. All solutions contained epinephrine 1:200,000. MEASUREMENTS AND MAIN RESULTS: Patients were assessed at regular intervals following administration of the epidural solution. Visual analog scale (VAS) scores were used to measure onset of analgesia, time to complete pain relief, duration of analgesia, and patient satisfaction with therapy. The frequency of shivering and pruritus and the extent of sensory/motor block also were evaluated. There were no intragroup differences in time to complete pain relief or patient satisfaction. However, patients in Group 3 noted the most rapid onset and longest duration of pain relief. Patients in Group 3 also experienced significantly less shivering and had the lowest degree of motor block. Two patients in Group 3 experienced mild pruritus. CONCLUSIONS: Epidurally administered fentanyl safely extended the duration of labor analgesia while reducing bupivacaine dose requirements and magnitude of motor block. In this setting, the combination of bupivacaine and lidocaine offered no clinical advantage over bupivacaine alone.     

Comparison of caudal epidural bupivacaine with bupivacaine plus tramadol and bupivacaine plus ketamine for postoperative analgesia in children

This study compared the effect of single-dose caudal epidural bupivacaine, bupivacaine plus ketamine and bupivacaine plus tramadol for postoperative pain management in children having surgery for inguinal hernia. Following ethics committee approval and informed parental consent, 75 children ASA PS I and II, between three and nine years of age and scheduled for elective unilateral inguinal hernia repair with general anaesthesia were recruited. The patients were randomly divided into three groups to receive 0.5 ml/kg caudal bupivacaine 0.25% (group B), bupivacaine 0.25% plus tramadol 1 mg/kg (group BT) or bupivacaine 0.25% plus ketamine 0.5 mg/kg (group BK). The injections were performed under general anaesthesia. Mean arterial pressure, heart rate, pulse oximetry, respiratory rate and sedation and pain scores were recorded at defined intervals following recovery from anaesthesia. The groups were similar in age, weight and duration of operation (P >0.05). No patient experienced hypotension, bradycardia or respiratory depression. Duration of analgesia was (mean+/-SD) 6.5+/-4.1 h in group B, 9.2+/-3.9 h in group BK, and 8.5+/-3.1 h in group BT (P <0.05). More patients in group B required supplementary analgesics in the first 24 h (P <0.05). Sedation scores were comparable in all groups. Incidence of emesis and pruritus was similar in all the groups. Caudally administered 0.5 ml/kg bupivacaine 0.25% plus ketamine or bupivacaine 0.25% plus tramadol 1 mg/kg provided significantly longer duration of analgesia without an increase in the adverse effects when compared to bupivacaine alone.     

Dexamethasone bupivacaine versus bupivacaine for peribulbar block in posterior segment eye surgery

AimThe study conducted aims to assess the efficacy, time to first analgesic request, and postoperative inflammatory response after adding dexamethasone to local anesthetic mixture for a peribulbar block in posterior segment eye surgery.Patients and methodsA double-blind randomized study was carried out on 50 ASA I and II patients scheduled for elective posterior segment surgery (vitreoretinal). Patients were allocated randomly into two groups, 25 patients in each group. Group I received equal volumes of 10 ml of a l:1 mixture of bupivacaine 0.5% and saline, supplemented with 4 mg dexamethasone in 1 ml saline and group II received the same local anesthetic mixture (total volume 10 ml) without adding dexamethasone. The duration and onset of motor block, time to first analgesic request, postoperative inflammatory response, and other side effects such as nausea and vomiting were assessed.ResultsPatients receiving peribulbar block were significantly pain free by end of surgery (0 h) (P < 0.05) and throughout the postoperative period in the dexamethasone group at 2 and 6 h postoperatively. The number of patients requiring rescue analgesics was significantly lower with dexamethasone bupivacaine block (P < 0.05). The incidence of postoperative nausea and vomiting was significantly less in the first group (I) in comparison to the other group (II) (P < 0.05) and lastly the level of C reactive protein postoperatively was found to be significantly less in the dexamethasone group than the other one (P < 0.0001).ConclusionAdding dexamethasone to bupivacaine in peribulbar block appears to be a safe and clinically superior adjuvant with less postoperative pain, inflammatory response in patients undergoing posterior segment eye surgery.     

Hyperbaric ropivacaine and bupivacaine

Editor—Whiteside and colleagues¹ in their comparison ofhyperbaric ropivacaine and bupivacaine for spinal anaesthesiastate that ‘the key issue is the difference in clinicalprofile of the block...not the relative potencies of the twodrugs’. It would have been much easier     

Duration of bupivacaine intradermal anesthesia when the bupivacaine is mixed with chloroprocaine

In a double-blind trial in 20 human volunteers, the duration of intradermal anesthesia with a mixture of bupivacaine, 0.5 mg, and chloroprocaine, 3 mg, was compared with the duration of intradermal anesthesia obtained with either bupivacaine, 0.5 mg, or chloroprocaine, 3 mg, alone. The duration of intradermal anesthesia produced by the bupivacaine mixed with chloroprocaine, 36 +/- 16 (mean +/- 1 SD) minutes, was significantly less than the duration of the same amount of bupivacaine alone, 139 +/- 78 minutes. Duration of anesthesia with chloroprocaine alone, 24 +/- 11 minutes, was similar to the duration of anesthesia with chloroprocaine plus bupivacaine. A possible explanation for these results is that bupivacaine competes with chloroprocaine for nonspecific receptors at the biophase and in the surrounding nerve tissue.     

Propranolol reduces bupivacaine clearance

Propranolol reduces the clearance of lidocaine by both reducing hepatic blood flow and inhibiting lidocaine metabolism. The authors investigated the possibility that propranolol reduces the clearance of bupivacaine as well. Bupivacaine, 30-50 mg, was administered intravenously to six normal human volunteers, over 10-15 min on two occasions, at least 2 weeks apart. Propranolol, 40 mg orally every 6 h, was used on one occasion, beginning 24 h prior to the bupivacaine administration. The sequence of the sessions was randomized. Twenty-two venous blood samples were obtained over 36 h in order to determine bupivacaine clearance, terminal elimination rate constant, and volume of distribution. All subjects experienced mild CNS toxicity, consisting of tinnitus, facial tingling, or subtle visual disturbances, associated with peak venous plasma concentrations of 0.81 to 2.7 micrograms/ml. Mean bupivacaine clearance was 0.33 +/- 0.12 l/min for the control session and 0.21 +/- 0.12 l/min during propranolol use, a significant 35% reduction (P less than 0.01). The terminal elimination rate constant (beta) was 0.27 +/- 0.16 h-1 for the control session and 0.14 +/- 0.069 h-1 with propranolol (P less than 0.05); terminal elimination half-lives were 2.6 and 4.9 h, respectively. Volume of distribution was unchanged. Because bupivacaine clearance should be relatively insensitive to hepatic perfusion, it appeared that propranolol caused a substantial inhibition of bupivacaine metabolism at the level of the hepatocyte. These data suggest that concomitant use of propranolol could result in the accumulation of a toxic concentration of bupivacaine.