Alkalinisation of bupivacaine for sciatic nerve blockade

Abstract

SummaryThis Key wordsAnaesthetic techniques, regional; sciatic nerve block. Anaesthetics, local; bupivacaine.Sciatic nerve blockade is a useful technique for providing intra-operative and postoperative analgesia for many operative procedures on the foot and lower limb. It is our practice to use bupivacaine for this purpose since it has a long duration of action in comparison to other agents currently available. The main disadvantage is its prolonged latency before satisfactory blockade is achieved.Local anaesthetic agents are weak bases prepared commercially as acidic salts to aid solubility and stability in solution. It has been demonstrated that the charged cationic molecule is required for conduction blockade while the uncharged base is necessary for adequate tissue p e n e t r a t i~n .~-~ The proportion of each will depend on the pKa of the agent and the ultimate pH of the solution. By raising the pH of the local anaesthetic solution nearer to the physiological range, the fraction of uncharged base available for tissue penetration will be increased. Recent studies have shown that latency and duration of action of both lignocaine and bupivacaine can be favourably altered by this m e t h~d .~-~ The purpose of this present study was to assess whether alkalinisation of bupivacaine produced any effect on the latency or duration of action of sciatic nerve blockade and to examine whether the systemic absorption of local anaesthetic is altered with the modified solution.

Sciatic nerve block with 0.5% levobupivacaine, 0.75% levobupivacaine or 0.75% ropivacaine

“…The onset time of nerve block reported in this study is longer than that reported when using levobupivacaine for different nerve blocks [5] but similar to that reported by other authors evaluating sciatic nerve block performed with other long-acting agents [6,9,[11][12][13]. Both the reduction in the onset time and increase in duration of nerve block demonstrated with 0.75% levobupivacaine as compared to the 0.5% concentration are reasonably related to the increase in the total dose injected and similar findings have been already reported [9,14].…”

Adjuvant Dexamethasone for Bupivacaine Sciatic and Ankle Blocks

“…Second, we typically give an "intermediate level" 10 systemic dexamethasone dose (~0.2 mg/kg) to enhance analgesia. Either or both of these factors, in addition to the study method of administering intravenous dexamethasone 8 mg to all patients, may have contributed to the unexpectedly high proportion of patients in both groups who had not experienced pain at the end of the 48-hour follow-up period, at odds with previous studies showing sciatic block to consistently have an analgesic duration of 13 to 14 hours, [17][18][19][20] and ankle block even shorter. 31,32 This precluded calculation of time to first pain with acceptable precision, thus necessitating analysis of this outcome as the proportion of patients with pain at specified time points.…”

Abordagem simplificada do nervo ciático por via posterior, no ponto médio do sulco glúteo-femoral, com uso de neuroestimulador

“…The large diameter of the sciatic nerve may lead to a less foreseeable blockade onset time, as compared to other peripheral blocks, although this pharmacological effect is primarily influenced by chemical properties of the anesthetic drug. In our investigation, mean onset time was 6 minutes, relatively lower than previous studies using other anesthetics by different routes, such as ropivacaine (10 to 25 minutes) 13,14,[24][25][26] and bupivacaine (20 to 30 minutes) 27 . It has to be stressed that no patient needed analgesic complementation during surgery, differently from what has been reported by other authors 14 .…”

“…Nesta investigação, observou-se latência média de 6 minutos, relativamente menor que estudos prévios que utilizaram outros anestésicos por diferente vias, como a ropivacaí-na, cuja latência média foi de 10 a 25 minutos 13,14,[24][25][26] , e bupivacaína de 20 a 30 minutos 27 . Ressalta-se a observação que nenhum paciente necessitou complementação analgésica durante a cirurgia, diferentemente referido por outros autores 14 .…”