Standard TAC (0.5%
tetracaine, 0.05%
epinephrine, and 11.8%
cocaine)
solution is finding increased use as a topical
anesthetic for
lacerations. The extent of systemic absorption of TAC components and their resultant physiologic effects are unclear. Absorption of
cocaine or
tetracaine may result in serious toxicity. The investigators hypothesized that there are no measurable plasma
cocaine or
tetracaine levels after application of TAC in a swine
laceration model. After an overnight fast 10 domestic swine underwent
tracheostomy,
mechanical ventilation, femoral venous, and arterial cannulation. Maintenance
anesthesia with intermittent
thiopental and
pancuronium was provided to maintain stage III
anesthesia. Heart rate (HR), arterial pressure (BP), plasma
cocaine, and
tetracaine levels were measured at intervals for 180 minutes. Five milliliters of TAC was applied for 15 minutes to a standardized facial
laceration in experimental swine (n = 5). Randomly labeled plasma samples were placed in vials containing 2%
sodium fluoride and 1%
potassium oxalate, immediately refrigerated, and analyzed for
cocaine and
tetracaine using gas chromatography and mass spectroscopy. Significant changes in HR and mean BP, compared with baseline values, were analyzed using Dunnett's multiple range test. Plasma
cocaine levels were measurable in all experimental swine after 10 minutes, while no
tetracaine was detectable. No significant differences in HR or BP changes were observed between experimental and control subjects. Application of standard TAC
solution results in measurable plasma
cocaine levels, but not
tetracaine. Further studies into
anesthetic formulation, as well as timing and technique of application, are required before consensus on optimal emergency departmental use of topical
anesthesia can be achieved.