Anaesthesia Local Anaesthetics ================== þ Epi for fingers/toes? - 48 cases of digital gangrene since 1888-2000: mostly used tourniquets. None after 1948 using commercially available substances with epinephrine. Wilhelmi Plast Recontr Surg 2001:107:393: lido with epi more effective, didn't have to use tourniquet, lasted longer, and since tourniquet caused damage. Doppler flow studies after epi: blood flow is redced, but within 60-90 minutes back to normal. OR tourniquet time several hours. Recent study of 3000 cases of epinephrine in fingers. Topical vs. digital block: LET and local lido with digital blocks: local faster, just as good. unpublished Adam Singer, SUNY Stonybrook. LET and EMLA both equally effective, gel easier to use; standard is to apply in triage, all wounds, adult and child, at SUNY Stonybrook. þ levobupivacaine (e.g., Chirocaine) - L isomer of bupivicaine - less cardiotoxic than bupivicaine in large doses, primarily for cases in the OR - new in 2000 þ Hematoma Blocks þ Topical Anaesthesia þ Reactions to local anaesthetics þ Two different classes: benzoic acid esters and amides: ============================================================================= Esters ("proke coke and tetra") Amides ----------------------------------------------------------------------------- Procaine (Novacaine) Lidocaine (Xylocaine) Cocaine Bupivicaine (Sensorcaine, Marcaine) Tetracaine (Pontocaine) Mepivicaine (Carbocaine) Benzocaine Pilocaine (Citanest) Etidocaine ============================================================================= No significant cross-reactivity between groups. þ Maximum Lidocaine Doses: - QUICK AND DIRTY: 1/2 cc 1% plain lido per kilo (35cc for 70kg)) - IV: 3 mg/kg - nerve block/local: 5 mg/kg (for 70 kg: 350 mg, which is 35cc of 1%, 17.5cc of 2%, and 8.75cc of 4%) - nerve block/local with epi: 7 mg/kg (for 70 kg, 500 mg, which is 50 cc) - 1% lido is 10 mg/cc; 2% is 20 mg/cc; 4% is 40 mg/cc) (can wait 30 minutes after maximal dosage, and then give additional, according to Rosen, 3rd ed. p307.) þ Maximum Doses, Other Anaesthetics: - Lidocaine: 5 mg/kg, or 7 mg/kg if with epinephrine - Bupivicaine: 2 mg/kg up to 175 mg max; 3 mg/kg up to 225 mg max if with epi - Procaine: 7 mg/kg - Tetracaine: 1.5 mg/kg for infiltration, 20 mg total for spinal - Cocaine: 2 mg/kg (per Emergency Medicine, April 30 1991, page 151) þ Local Anaesthetics do reduce pain from IV insertion (18-22 ga.) [Langham BT, et al. Local anesthetic: does it really reduce the pain of insertion of all sizes of venous cannula? Anaesthesia 1992; 47(10):890.] þ Benadryl (diphenhydramine) for local anesthesia: - use 5% solution, diluted with 4 parts saline to produce 1% solution; duration of about 30 minutes. PDR recommends against use for local anesthesia. [Pollack C, Swindle NG. Use of diphenhydramine for local anesthesia in "caine"-sensitive patients. J Emerg Med 1989;7:611.] þ Reducing pain with injection: - distraction by pressure or vibration - buffering with NaHCO3 - warming [Davidson JAH, Boom SJ. Warming lidocaine to reduce pain associated with injections. Brit Med J 1992;12(305):617-618.] But see new article that says it doesn't help Martin S, et al. Does warming local anesthetic reduce the pain of subcutaneous injection? Am J Emerg Med 1996; 14(1):10.] Abstract: And a new article that says there is a synergistic effect: [Mader TJ, Playe SJ, Garb JL. Reducing the pain of local anesthetic infiltration: warming and buffering have a synergistic effect. Ann Emerg Med. 1994;23:550-4.] Abstract: - Giving digital blocks in the web space. [Knoop K, Trott A, Syverud S. Comparison of digital versus metacarpal blocks for repair of finger injuries. Ann Emerg Med. 1994;23:1296-300.] Abstract: This small study shows that it works better in the web space than in the metacarpal head area, and if it were a bigger study I'm sure it would have shown it to be less painful (based on my own clinical experience). - And, buffering lidocaine with epi will diminish the effect of the epinephrine: >I remember being told by the lecturer on facial anesthesia at last year's >ACEP meeting that you should not use HCO3 with the xylo + epi that you use >for dental or facial anesthesia as it effects the mode of action which >requires the polarization that the acidic solution provides. Does this >apply to ALL uses of xylo+epi (e.g. when used for local infiltration vs. >nerve block)? Or was the lecturer off base? Buffering lidocaine results in degradation of epinephrine which may be a consideration if the latter is being used for purposes of hemostasis or for prolonging the anesthetic effect (1). (We all recall, of course, the advise against mixing catecholamines with bicarbonate solutions from ACLS--although rapid sequential infusions in that situation is probably of no consequence compared to prior mixing). As it stands, the duriation of effect of lidocaine is shorter when used on the face then when used elsewhere. --H. Louzon MD [Murakami CS, Odland PB, Ross BK. Buffered local anesthetics and epinephrine degradation. J Dermatol Surg Oncol 1994 Mar;20(3):192-5.] Reference: - You CAN buffer Marcaine (Sensoricaine, bupivicaine) Cheney PR, Molzen G, Tandberg D The effect of pH buffering on reducing the pain associated with subcutaneous infiltration of bupivicaine [published erratum appears in Am J Emerg Med 1991 Jul;9(4):410] [see comments] Am J Emerg Med 1991 Mar;9(2):147-8 Abstract: