Factors influencing precipitation of pH-adjusted bupivacaine solutions

Buffered Versus Nonbuffered Local Anesthetics and Local Pain Scores in Upper Eyelid Blepharoplasty: Randomized Controlled Trial

PURPOSE

This split-face study aimed to see whether different types of local anesthetics or their buffered/nonbuffered combinations produce lower pain scores in upper eyelid blepharoplasty.

METHODS

The study involved 288 patients, randomly divided into 9 groups: 1) 2% lidocaine with epinephrine-Lid + Epi; 2) 2% lidocaine with epinephrine and 0.5% bupivacaine (1:1)-Lid + Epi + Bupi; 3) 2% lidocaine with 0.5% bupivacaine (1:1)-Lid + Bupi; 4) 0.5% bupivacaine-Bupi; 5) 2% lidocaine-Lid; 6) 4% articaine hydrochloride with epinephrine-Art + Epi; 7) buffered 2% lidocaine/epinephrine with sodium bicarbonate (SB) in a 3:1 ratio-Lid + Epi + SB; 8) buffered 2% lidocaine with SB in a 3:1 ratio-Lid + SB; 9) buffered 4% articaine hydrochloride/epinephrine with SB in a 3:1 ratio-Art + Epi + SB. Following the injection of the first eyelid and a 5-minute period of soft pressure on the injection site, patients were asked to rate their pain level on the Wong-Baker Face Pain Rating Visual Analogue Scale. Rating of the pain level was repeated 15 and 30 minutes following anesthetic administration.

RESULTS

The lowest pain scores at the first time point were observed in Lid + SB when compared with all of the other groups ( p < 0.05). At the final time point, significantly lower scores were also observed in Lid + SB, Lid + Epi + SB, and Art + Epi + SB when compared with the Lid + Epi group ( p < 0.05).

CONCLUSION

These findings could help surgeons select an appropriate combination of local anesthetics, particularly in patients with lower pain threshold and tolerance because buffered combinations of local anesthetics produce significantly lower pain scores compared with nonbuffered solutions.

What the phlebologist should know about local anesthetics

An increasing number of phlebological interventions are performed under local and tumescent anesthesia. Although the modern local anesthetic agents are generally perceived as being effective and safe drugs, the administration of these drugs may be associated with a number of adverse events. It is therefore mandatory that everyone who uses these compounds has insight into the pharmacological actions of these drugs and is capable of recognizing and adequately treating potential adverse events. The present narrative review summarizes the current knowledge on mechanisms of action of the most important local anesthetic drugs and reviews the potential adverse effects as well as their treatment.

Tumescent anaesthesia

Tumescent anaesthesia describes the practice of injecting a very dilute solution of local anaesthetic combined with epinephrine and sodium bicarbonate into tissue until it becomes firm and tense (tumescent). It was initially described in the field of liposuction but now surgical applications for the technique are widely varied ranging across vascular surgery, breast surgery, plastic surgery and ENT procedures. It is widely used in both hospital- and office-based environments and may form the sole method of anaesthesia for surgery. Advantages include a reduction in blood loss through both epinephrine-induced vasoconstriction as well as hydrostatic compression from the tumescent effect. Sodium bicarbonate reduces pain associated with the injection of an acidic local anaesthetic solution. Due to the unique pharmacokinetic profile of this technique lidocaine doses of 35 mg/kg bodyweight have been shown to be safe for liposuction procedures. Tumescent lidocaine is absorbed very slowly from subcutaneous tissues producing lower, and more delayed, peak blood levels compared to other routes, as well as extended postoperative analgesia. Slow systemic absorption allows the rapid hepatic plasma clearance of lidocaine to maintain safe local anaesthetic blood levels. This slow absorption from subcutaneous tissue has been likened to a depot injection. Careful attention must be given to appropriate local anaesthetic dosage alterations in cases of co-administration with agents affecting hepatic drug clearance or conditions reducing liver blood supply. Adherence to these pharmacological principles has produced an exemplary safety record for this technique to date.

Spinal Cord Compression in a Patient with a Pain Pump for Failed Back Syndrome: A Chalk-Like Precipitate Mimicking a Spinal Cord Neoplasm: Case Report

OBJECTIVE AND IMPORTANCE

The use of intrathecal morphine has been effective with few complications for chronic intractable pain of both benign and malignant origins. A rare but serious problem that exists is the formation of an inflammatory mass at the catheter tip of the pain pump.

CLINICAL PRESENTATION

We report the case of a 67-year-old female patient with failed back syndrome who presented with sensory complaints and back pain.

INTERVENTION

Magnetic resonance imaging revealed impingement on the thoracic cord by a mass. The mass was originally thought to be a spinal cord tumor; however, operation and chemical analysis of the mass showed that it was a bupivacaine precipitate at the tip of the catheter of the pain pump.

CONCLUSION

This is the first such case, to our knowledge, of a bupivacaine precipitate mimicking a spinal cord tumor.

Identification of the precipitate in alkalinized solutions of mepivacaine and bupivacaine at 37 degrees C

Commercial and control solutions of bupivacaine (0(.)75%) and mepivacaine (1(.)5%) were alkalinized with bicarbonate until cloudy at room temperature. The solutions were heated to 37 degrees C for 2(.)5 h. The precipitates were filtered, lyophylized and analysed by fast atom bombardment mass spectrometry. Analysis showed the precipitates to be predominantly the free base of the local anaesthetic. The precipitate of the commercial bupivacaine solution also contained a small amount of the hydrochloride salt. The mepivacaine control crystals contained an unknown at molecular weight 528, which may represent a dimer of the free base and hydrochloride salt.

The use of pH adjusted lignocaine in controlling operative pain in the day surgery unit: a prospective, randomised trial

We report the results of a randomised, case matched, controlled, double blind study on 40 patients undergoing correction of their prominent ears, comparing efficacy of pH adjusted lignocaine to lignocaine alone in controlling operative pain. Each patient received commercial lignocaine in one ear and the same preparation reconstituted with 1 ml of 8.4% sodium bicarbonate in the other ear according to our randomisation protocol. 30 patients were studied to compare the difference between the buffered and commercial preparation infiltrated at room temperature. A further 10 patients were studied to assess the benefit the buffered preparation at room temperature had over commercial lignocaine warmed to body temperature. Linear analogue pain scores for discomfort at infiltration and during the operation itself were analysed. Buffered lignocaine imparts a significant reduction in pain on infiltration, compared to the commercial preparation at both room and body temperature. Both preparations were equally effective in obliterating pain during the operation itself.