Effect of adrenaline on duration of infraorbital nerve block with lignocaine in the rat.
A double-blind investigation of the effect of adrenaline on conduction blockade was undertaken in six groups of rats (n = 12 or more) using a standardized injection of 0.4 ml of solution into the left infraorbital nerve. All six solutions contained lignocaine 0.25 g dl-1. In groups 1-3, the solutions were isotonic, in groups 4-6 the osmolarity was 0.6 isotonic. Solutions 1 and 4 contained potassium chloride 4 mmol litre-1 but no adrenaline; solutions 2 and 5 potassium chloride and adrenaline 5 micrograms ml-1 (1:200 000); solutions 3 and 6 adrenaline but no potassium chloride. The presence and duration of sensory blockade was determined from the reflex submandibular electromyographic response to periodic electrical stimulation of the homolateral and contralateral upper lips. In groups 1 and 4 (adrenaline absent) the mean durations of blockade (+/- SD) were 45 +/- 24 and 43 +/- 19 min. In groups 2, 3, 5 and 6 (adrenaline present) the durations of block averaged 97 +/- 4, 97 +/- 38, 105 +/- 21 and 92 +/- 16 min, respectively. Thus adrenaline approximately doubled the duration of blockade irrespective of osmolarity or potassium chloride concentration of the local anaesthetic solution (P less than 0.001).
D000818:Animals; D004837:Epinephrine / Q000494:pharmacology*; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D009407:Nerve Block; D009915:Orbit / Q000294:innervation*; D009994:Osmolar Concentration; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D013997:Time Factors
D011189:Potassium Chloride; D008012:Lidocaine; D004837:Epinephrine