Topical anaesthesia of intact skin: liposome-encapsulated tetracaine vs EMLA

In this randomized, double-blind study, we have compared the ability of 5% liposome-encapsulated tetracaine (amethocaine) (LET) vs 5% eutectic mixture of local anaesthetics (EMLA) to produce local anaesthesia of intact skin in 40 healthy volunteers. Volunteers had both preparations applied to their forearms under an occlusive dressing for 1 h. Superficial anaesthesia was measured by a total of nine 1-mm pinpricks on each arm. Deeper anaesthesia was assessed by single insertion of a sterile 22-gauge needle to a depth of 3 mm and pain was reported on a visual analogue scale (VAS). If the volunteer perceived greater than four of the 1-mm pinpricks, the 3-mm insertion was not performed. Results showed that the number of pinpricks perceived was significantly less (P < 0.01) for LET (median 1.0; range 0-9) vs EMLA (1.5; 0-9). In volunteers who had deeper anaesthesia assessed, there was no significant difference (P = 0.065) in VAS scores for LET (mean 1.5 (SD 1.4); n = 34) vs EMLA (2.4 (2.1); n = 28). Overall anaesthetic effect, as ranked by all of the subjects, was significantly better for LET compared with EMLA (P = 0.024). We have demonstrated that when applied in equal volumes, 5% LET produced better superficial local anaesthesia than EMLA.      

Split skin grafting using topical local anaesthesia (EMLA): a comparison with infiltrated anaesthesia

The analgesic efficacy of EMLA cream was compared with that produced by infiltration of lignocaine solution when used to provide anaesthesia for cutting of skin grafts. The study was performed as an open parallel group comparison in 80 patients. Pain felt during administration of the anaesthetic and during cutting of the graft was assessed using visual analogue and verbal rating scales. During graft cutting, the anaesthesia produced by EMLA was at least as effective as infiltration. On administration, infiltration produced varying amounts of pain in all patients, but in contrast EMLA produced no discomfort. In view of this lack of discomfort and the consequent greater freedom afforded regarding the area of donor site anaesthetised, EMLA can be considered the treatment of choice when skin grafts are harvested under local anaesthetic.     

Topical anesthesia of the skin by liposome-encapsulated tetracaine

The potential of a liposomal local anesthetic formulation to provide topical anesthesia of the intact skin was investigated. Tetracaine base 0.5% was encapsulated into multilamellar phospholipid vesicles. The topical anesthetic effects of the liposomal and a control (Pontocaine cream) preparation were evaluated by pinprick technique in adult volunteers. Liposomal tetracaine-produced anesthesia, which lasted at least 4 hours after 1 hour application under occlusion. Pontocaine cream was ineffective. The liposomal formulation appeared to be suitable to provide long lasting anesthesia of the skin with low drug concentration.     

Comparison of percutaneous anaesthesia for venous cannulation after topical application of either amethocaine or EMLA cream

We have compared, in a double-blind study, the efficacy of topicalamethocaine cream 1 g (5% w/w) in alleviating the pain of venouscannulation with that of 5% EMLA cream 2.5 g. One hundred andtwenty unpremedicated female patients undergoing minor gynaecologicalsurgery, were allocated randomly to one of four groups: 5 %EMLA cream 2.5 g for 30 min; 5% EMLA cream 2.5 g for 60 min;amethocaine cream 1 g (5% w/w) for 30 min; amethocaine cream1 g (5% w/w) for 60 min. After removal of the cream, venouscannulation was performed with an 18-gauge cannula. Patientsassessed the pain experienced using a 700-mm visual analoguescore and four-point rank score. In addition, a blinded observerassessed the patient's response to venous cannulation usinga four-point rank score. Good analgesia was obtained in allgroups and there was no statistically significant differencein pain scores between the groups.     

Clonidine prolongs canine tetracaine spinal anaesthesia

Using a randomized blind cross-over design, the comparative efficacy of clonidine in prolonging tetracaine spinal anaesthesia was studied in six mongrel dogs. Lumbar subarachnoid injections (1 ml) of: tetracaine 4 mg with clonidine 150 micrograms, tetracaine 4 mg with epinephrine 200 micrograms, tetracaine 4 mg, clonidine 150 micrograms, epinephrine 200 micrograms, and five per cent dextrose in H2O (vehicle) were administered randomly to each animal at 5-7 day intervals. Subarachnoid tetracaine produced a motor blockade of 186 +/- 58 (mean +/- SEM) min. Both clonidine and epinephrine produced a similar prolongation of tetracaine motor blockade, 135 per cent (p less than 0.01) and 116 per cent (p less than 0.05) respectively, compared with tetracaine alone. No motor blockade was observed in dogs receiving clonidine, epinephrine or five per cent dextrose in H2O. The addition of clonidine to tetracaine spinal anaesthesia produced a significant increase in duration of sensory blockade, 56 per cent (p less than 0.01) and 107 per cent (p less than 0.01) respectively, when compared to tetracaine with and without epinephrine. Subarachnoid clonidine alone produced a sensory blockade of 76 +/- 17 minutes, while only one animal receiving subarachnoid epinephrine had a sensory blockade (40 minutes). No neurologic deficits were observed in any of the animals. The study concludes that during spinal anaesthesia with tetracaine in dogs, clonidine is as effective as epinephrine in prolonging motor blockade, but is more effective in prolonging sensory blockade.     

碱化丁卡因溶液尿道粘膜表面麻醉的临床观察和药代动力学研究

１６例接受膀胱镜检的患者分为临床碱化组和临床对照组；将２０只家兔匀分为动物碱化组和动物对照组。碱化组均给予ｐＨ７．１５的１％丁卡因溶液，对照组给予ｐＨ５．１的１％丁卡因溶液。结果，临床碱化组麻醉效果优于临床对照组（Ｐ＜０．０５）。但临床对照组药液在血液中达峰时间（Ｔｐｅａｋ）快；峰浓度（Ｃｍａｘ）及血药浓度的各个时点均高于临床碱化组（Ｐ均＜０．０１）。两组中分布半衰期，消除半衰期无显著性差异。表现分布容积（Ｖｄ），药时曲线下面积（ＡＵＣ）和清除率（ＣＬ）有显著性差异（Ｐ均＜０．０１）。动物碱化组丁卡因在血中浓度低，而在膀胱组织中浓度高（Ｐ均＜０．０１）。认为碱化丁卡因具有效果好，毒性低和清除快的优点，用于临床尿道粘膜表面麻醉安全有效。     

Painless treatment of hydrocele: EMLA cream anaesthesia and fibrin adhesive sclerotherapy

Sclerotherapy for hydroceles was performed in 18 patients. Cutaneous anaesthesia was induced with an anaesthetic cream (lidocaine and prilocaine, EMLA cream) and a fibrin sealant (Tissucol) was injected into the sac after fluid aspiration. Patients experienced no pain during needle insertion and sclerosant procedure; 2 recurrences were observed during follow-up. EMLA cream anaesthesia and fibrin adhesive sclerotherapy represent a useful alternative to surgical treatment of hydroceles.     

Tetracaine gel vs EMLA cream for percutaneous anaesthesia in children

We have evaluated the anaesthetic effect of tetracaine gel 1 g, applied for 45 min, compared with EMLA cream 2 g, applied for 60 min, in a randomized, double-blind study in 60 children aged 3-15 yr. Venous cannulation was performed 15 min after removal of the EMLA cream (n = 20) and tetracaine gel (n = 20). Cannulation was performed up to 215 min after removal of the tetracaine gel in another 20 patients. Significantly lower pain scores were recorded by the children treated with tetracaine gel compared with EMLA cream (P < 0.02). Forty to 45% of children in the tetracaine groups reported no pain compared with only 10% in the EMLA group. Only minor adverse effects were observed. We conclude that tetracaine gel provided effective, rapid, long-lasting and safe local anaesthesia, and was significantly better than EMLA cream in reducing pain during venous cannulation in children using the recommended application periods for both formulations.      

Isobaric spinal anaesthesia with bupivacaine and tetracaine (author's transl)]

4 ml 0.5% solutions of bupivacaine and tetracaine without the addition of a vasoconstrictor, approximately isobaric, were used for spinal anaesthesia on patients in the sitting position. The sensory and motor block due to the two local anesthetics was tested and compared. The mean time on onset of complete analgesia was the same for both local anaesthetics (9 and 11 min), as was also the highest level of analgesia (T10). The duration of maximal extension of analgesia was on an average 45 min longer due to tetracaine (bupivacaine 105 min, tetracaine 150 min). The duration of maximal spread of the blocked sensation of pain, temperature, pressure and touch was similar for each of both local anesthetics. The regression of these sensory qualities, blocked in a dissoaciated manner, took a parallel course. With tetracaine the motor block of the lower extremities developed faster and lasted longer (Bromage 3 for bupivacaine 192 min, for tetracaine 220 min). Motor function and proprioception normalized in a synchronized manner. Isobaric spinal anaesthesia with these two solutions of local anaesthetics was found to be reliable and controllable, especially when administered to the sitting patient. Tetracaine is a good alternative to bupivacaine, currently controversial for intrathecal use.     

Viscosity of diluent and sensory level of subarachnoid anaesthesia achieved with tetracaine

Purpose

Our objective was to evaluate the effect of viscosity in determining the cephalad spread of tetracaine administered by the subarachnoid route.

Methods

We studied 42 patients that were randomly assigned to receive subarachnoid anaesthesia for arthroscope of the knee. They received 8 mg tetracaine dissolved in either glucose 10%, sodium chloride (NaCl) 5%, glucose 5%, or NaCl 2.5%. The specific gravity and viscosity of each solvent was also measured. Cephalad spread was defined as the level of sensory block achieved.

Results

The specific gravity of the glucose 5% and the NaCl 2.5% solutions were similar (1.0197 ± 0.0001 vs 1.0177 ± 0.0001 (mean ± SD)). That was also true for the more concentrated pair of solutions (1.0385 ± 0.0001 for glucose 10% vs 1.0353 ± 0.0003 in NaCl 5%). However, the viscosities of the 10% and 5% solutions of glucose (0.01178 ± 0.0002 and 0.01020 ± 0.0002 (g·cm^?1·sec^?1)) were higher (P < 0.05) than that of the other two solutions, being 0.00955 ± 0.0001 for NaC1 5% and 0.00934 ± 0.0002 for NaCl 2.5%. The median maximal extent of sensory block achieved was significantly higher (P < 0.05) with a solution of tetracaine in glucose 10% injected into the subarachnoid space at the L_3–4 interspace than that observed in the two groups administered tetracaine in NaCl. The level of sensory block 30 min after the injection of anaesthetic was; T₃ [T_1–6] (median [range]) with glucose 10%, T₆ [T_4–10] with NaCl 5%, T₅ [T_2–11] with glucose 5%, and T_5.5 [T_2–11] with NaCl 2.5%.

Conclusion

Viscosity was shown to be one of determinants of the clinical extent of spread of a subarachnoid anaesthetic such as tetracaine.     

Comparison of hyperbaric solutions of bupivacaine and tetracaine during continuous spinal anaesthesia

The aim of this study was to compare two equipotent solutions of hyperbaric bupivacaine and tetracaine in 30 elderly patients undergoing elective hip surgery under continuous spinal anaesthesia. With the patient in the supine position, 2 ml (8 mg) of either hyperbaric solution (density 1.030) were administered in a double-blind and randomized fashion. The median maximum sensory and temperature discrimination levels (T5 and T4) were similar with both solutions. The duration of analgesia was not different (114 +/- 23 min for bupivacaine and 125 +/- 35 min for tetracaine). Thirteen out of fifteen patients receiving bupivacaine and all 15 patients receiving tetracaine had complete motor blockade. The haemodynamic changes and vasopressor requirements were comparable. The plasma catecholamine levels measured at four different times remained unchanged and were not different between the two groups at any time. The authors conclude that, during continuous spinal anaesthesia, equipotent hyperbaric solutions of bupivacaine and tetracaine have similar anaesthetic and haemodynamic effects.     

Spinal anaesthesia with hyperbaric tetracaine: effect of age and body mass

To discover the influence of age and body mass on spinal analgesia with hyperbaric tetracaine, 60 patients (17-82 years) were administered a subarachnoid injection of 15 mg tetracaine in 3 ml of 5% glucose. The patients were in the lateral position during the injection and in the supine position thereafter. The maximal spread of analgesia (mean T4, range T1-T11) did not correlate with age or body mass. Any variable studied was not significantly different for the different age groups. In 29 patients (48%) the block required supplementation with fentanyl or general anaesthesia (five patients). Tourniquet-induced pain occurred in eight patients (28% of patients with tourniquet). Decreases in systolic arterial blood pressure, greater than 30% of the preanaesthetic value, correlated with the level of analgesia and were more frequent in patients over 50 years (P less than 0.01). Severe hypotension and bradycardia with transient serious changes in QRS-complexes occurred in one patient (analgesia level, T3). In conclusion, 15 mg of hyperbaric tetracaine provided a relatively high sensory spinal blockade without correlating with age or body mass. Supplementation of analgesia during surgery was needed in almost half of the patient material.     

Effects of different glucose concentrations on spinal anaesthesia with bupivacaine and tetracaine

The effects of 5% and 8% glucose in 0.5% tetracaine or bupivacaine on the anaesthetic spread were investigated in 80 urological patients requiring spinal anaesthesia for trans-urethral resection of the prostate. The local anaesthetic solutions were randomly administered, the patients being divided into four groups of 20, and the anaesthetic profile was then evaluated in a double-blind fashion by an independent observer. Maximum cephalad spread of analgesia was significantly greater with tetracaine in 8% glucose compared to the other three groups (tetracaine/5% glucose, bupivacaine/5 or 8% glucose) (P less than 0.05). Glucose concentration significantly influenced spreading characteristics of tetracaine, the 8% solution achieving a higher level in a shorter time than the 5% solution. Sensory regression to both T10 and S1 dermatome was longer with bupivacaine in 8% glucose compared to 5% glucose. The concentration of glucose, however, did not influence the regression of sensory analgesia for tetracaine. Both the 5% and 8% solutions of tetracaine achieved a 3+ motor blockade significantly faster than either bupivacaine solution. Regression of motor blockade from tetracaine was not influenced by the glucose concentration, but the 8% solution of bupivacaine had a delayed 2+ and 3+ blockade, although the ultimate decay for both solutions was similar. The results of our study suggest that 0.5% bupivacaine 4 ml in 5% glucose provides a rapid and controllable spread of sensory analgesia for transurethral surgery, of optimal duration associated with a complete motor blockade of moderate duration.     

EMLA cream as a topical anaesthetic for ulcer debridement and simultaneous split-skin grafting

Summary The object of the study was to investigate the effect of EMLA cream when used as an anaesthetic for the debridement of ulcers and wounds. The cream was applied to a fresh, standardized wound caused by a dermatome, to an ulcer which was to be revised and for simultaneous split-skin grafting to both donor site and recipient area to be debrided. The effect on wound healing, the plasma concentrations of lidocaine and prilocaine and the analgesic effect following the application of EMLA to the ulcer and to both ulcer and donor site were studied. The study showed that EMLA cream when topically applied has a sufficient analgesic effect for revision of an open ulcer and can be used concomitantly for both revision of the ulcer and cutting of the split-skin graft. The application of EMLA cream to the fresh wound, or to the recipient area prior to cleaning, did not cause any clinical signs of a delayed healing at the applied areas compared to the control sites. Correspondence to: L. Ohlsén     

Percutaneous anaesthesia with a lidocaine-prilocaine cream (EMLA®) for cutting split-skin grafts

Summary Percutaneous anaesthesia induced by a lidocaine/prilocaine cream (EMLA®) applied to the donor area for 1 to 8 h enabled split-skin grafts to be harvested without supplementary analgesia in 72 out of 83 patients (87%). The pain during cutting of the graft was rated as either none or slight by 60 patients, as moderate by 16 and as severe by 6 of the patients. The results suggest that the best analgesic effect is obtained if the graft is cut within five hours of the cream being applied. No adverse influence on the viability of the graft or on the healing of the donor site was observed. Topical anaesthesia with EMLA cream is useful for harvesting split-skin grafts and is now used routinely at this clinic.