Blood collection in cats is an essential part of feline medicine. However, the collection of blood samples may be a stressful experience for many patients, decreasing the quality of life for patients, increasing the risks of injury to veterinary staff, and making for a more negative experience for both humans and cats involved in the process. Decreasing the stress associated with phlebotomy may be accomplished through multiple means, including low stress handling practices and chemical sedation/anxiolysis. The use of topical local anesthetics has been proposed as a measure to reduce the stress of phlebotomy by preventing cats from feeling the needle penetrating skin.
Previous studies have documented the use of a topical lidocaine/prilocaine preparation (EMLA) for the placement of cephalic and jugular catheters in cats, with varying results. The purpose of this study was to determine the efficacy of EMLA in jugular venipuncture in cats for blood collection. The study was designed as a prospective double blinded placebo-controlled trial.
Healthy cats presenting to a veterinary teaching hospital for routine exams, pre-anesthetic blood collection, or blood donation were enrolled into the study. Cats were required to have no neck lesions, and to be easily handled on physical exam. Eighteen cats were selected and enrolled randomly into equal EMLA and placebo groups.
Cats had a baseline Modified Behavioural Pain Scale (MBPS) score measured at baseline, and were excluded if >= 2. All interventions were standardized and performed by the same experienced operators. In all cats, a 2x4cm area of the left jugular groove was clipped and 1mL of either EMLA or liquid paraffin applied, and an occlusive bandage of plastic film and cotton wool applied for 30 minutes. The bandage was then removed, the area prepped with a chlorhexidine and alcohol solution, and phlebotomy performed.
During sampling, cats were observed and a MBPS score applied. The ease and success of the procedure were scored by the phlebotomist. Heart rate, respiratory rate, and rectal temperature were measured before and after the collection. Phlebotomists and observers were blinded to the group of the cat. The application area was then observed 15 minutes after the procedure for evidence of local reaction.
No statistical difference was seen in the physiologic parameters before and after phlebotomy in either group. The sample collection process was scored as “easy” in 1/9 control cats and 8/9 EMLA cats. Median stress score was 2 for EMLA cats vs 6 for control cats. Withdrawal movements were seen in 7/9 control cats and 1/9 placebo cats. These differences were all statistically significant.
No local or systemic adverse reactions to EMLA were reported. One cat in each group developed a hematoma after blood collection.
Some limitations to this study exist. Feline stress levels were measured based on a score, and not based on biochemical markers. However, the purpose of this intervention is to aid blood collection, and so biochemical markers may be less relevant. While the study design was excellent, numbers were small, and a larger sample size would be recommended. Only cats compliant with handling were enrolled, and so more data on less easily handled cats would be of benefit. Another concern is for practicality- while this practice did reduce stress, it requires shaving the neck and placement of a neck bandage (which may themselves induce stress) and at least an additional 30 minutes of stay in the hospital. In a busy clinic environment, this may not always be practical.
The authors conclude that, based on this study, application of EMLA for 30 minutes prior to jugular phlebotomy decreased feline stress and increases the ease of blood collection in cats. (MRK)
Oliveira RLS, Soares JHN, Moreira CMR, et al. The effects of lidocaine–prilocaine cream on responses to intravenous catheter placement in cats sedated with dexmedetomidine and either methadone or nalbuphine. Vet Anaesth Analg 2019; 46: 492–495.
Wagner KA, Gibbon KJ, Strom TL, et al. Adverse effects of EMLA (lidocaine/prilocaine) cream and efficacy for the placement of jugular catheters in hospitalized cats. J Feline Med Surg 2006; 8: 141–144.