Evaluation of adverse effects of EMLA (lidocaine/prilocaine) cream for the placement of jugular catheters in healthy cats

Hospitalized veterinary patients undergo a number of potentially painful procedures such as venipuncture and catheter placement. In human pediatric patients, topical anesthetics are gaining popularity in the prevention of pain associated with such minor invasive procedures. A cream containing a mixture of 2.5% lidocaine and 2.5% prilocaine (EMLA cream , AstraZeneca, Wilmington, DE, USA) has been shown to provide effective local analgesia for catheter placement, venipuncture, vaccinations, lumbar spinal taps, circumcision, and skin mass removals in adults, children, and neonates (Hallen & Uppfeldt, 1982; Manner et al., 1987; Rosdahl et al., 1988; Gupta & Sibbald, 1996; Koscielniak-Nielsen et al., 1998; Halperin et al., 2000). EMLA is an abbreviation for Eutectic Mixture of Local Anesthetics; a eutectic mixture allows solubilization of the anesthetic agents in a form that permits local absorption without the use of organic solvents (Lener et al., 1997). Analgesia is due to high local concentrations of lidocaine and prilocaine in the skin, with minimal systemic absorption. EMLA cream is well tolerated in most human patients, even neonates (Taddio, 2001). Common side effects include blanching of the skin or local erythema (Lener et al., 1997). Methemoglobinemia or neurologic toxicity have been reported less commonly, generally within 1–3 h of cream removal when EMLA has been applied to a large surface area or for prolonged periods of time (Lener et al., 1997; Rincon et al., 2000). For human pediatric patients, a conservative maximum EMLA dose of 1–2 g over 10 cm, with an application time of 1–1.5 h under occlusion, has been recommended (Chang et al., 1994). There is only one report of the use of EMLA cream in cats, in which EMLA was apparently well tolerated for the placement of peripheral cephalic catheters in dogs, cats, and rabbits in an experimental setting (Flecknell et al., 1990). No adverse effects were observed in these animals, although the degree of systemic absorption was not measured. The purpose of this pilot study was to determine the degree of systemic absorption and clinical adverse effects during the use of EMLA cream in the placement of jugular catheters in healthy cats. Ten healthy young adult cats (five male, five female) without previous jugular venipuncture were used for the study. The study protocol was approved by the IACUC at the University of Wisconsin-Madison. For each cat, 1 g (1 cc) of EMLA cream (Astra Pharmaceuticals) was applied in a thick layer to a 2 · 5 cm area of closely shaved skin (#40 blade) overlying one jugular vein. The treated area was then covered with a 6 · 7 cm occlusive bandage (Tegaderm; 3M Corp., St Paul, MN, USA). Clinic personnel wore exam gloves during cream application. After 1 h, the occlusive bandage was removed and the EMLA cream was gently wiped away with 70% ethanol. A routine sterile scrub of the area was performed, and a 19-gauge, 20.3 cm jugular catheter (Intracath; Becton Dickinson, Cockeysville, MD, USA) was placed on the treated side. As jugular catheters in cats are generally placed under sedation in our hospital, all cats were monitored by the technician for discomfort during catheter placement, to include: (i) struggling against restraint, (ii) biting or scratching, or (iii) loud vocalization. If one or more of these signs were observed, the procedure was stopped, and the cat was sedated for subsequent jugular catheter placement with midazolam (0.1 mg/kg, i.m.) and butorphanol (0.4 mg/kg, i.m.). Four categories of adverse effects were evaluated: local irritation, systemic absorption of lidocaine or prilocaine, development of methemoglobinemia, and clinical evidence of gastrointestinal, neurologic, or cardiovascular complications. For evaluation of local irritation, the treated area was examined for the presence of erythema, swelling, or pruritis (as evidenced by scratching) after cream and bandage removal. For evaluation of systemic absorption, blood samples [0.5 mL each in ethylenediaminetetraacetic acid (EDTA)] were obtained for the determination of serum lidocaine and prilocaine concentrations, J. vet. Pharmacol. Therap. 26, 439–441, 2003. SHORT COMMUNICATION