Short Communication
Onset, duration and efficacy of four methods of local anesthesia of the horn bud in calves

https://doi.org/10.1111/j.1467-2995.2012.00717.xGet rights and content

Abstract

Objective

To determine the onset, duration and efficacy of four local anesthetic methods for the horn bud in calves.

Study design

Crossover study.

Animals

Eight, 2 month-old Holstein Friesian bull calves.

Methods

Calves were subjected to one of the four following treatments: 1) cornual nerve block (C), 2) ring block (R), 3) cornual nerve block using a percutaneous jet delivery technique (JET) all using 2% lidocaine with epinephrine (0.01 mg mL−1), and 4) topical eutectic mixture of local anesthetics (EMLA) cream. A peripheral nerve stimulator was used to assess cutaneous sensation over the horn bud using a graded response. Onset, duration and efficacy of anesthesia were determined.

Results

The efficacy of the blocks was as follows: C 87.5%, R 100%, JET 37.5%, EMLA 0%. The median onset time and duration of anesthesia for C and R were: 2 (range 0.5–5) and 304 (range 107–512), and 3.25 (range 1–9) and 147 (range 62–299) minutes, respectively. Three of eight JET injections had a median onset and duration of 8 (range 0.5–9) and 132 (range 101–155) minutes, respectively. The duration of the C block was significantly longer than the R block (p= 0.047).

Conclusions and clinical relevance

The relatively rapid onset and long duration of anesthesia with C or R blocks using 2% lidocaine with epinephrine validates their practical use in dehorning calves while jet injection and EMLA cream provided insufficient analgesia to be clinically useful. The efficacy of the C block requires further study.

Introduction

Dehorning is a routine practice in cattle production. Previous studies have shown that dehorning is painful and that local anesthesia mitigates acute pain (Morisse et al. 1995; Grøndahl-Nielsen et al. 1999; Stafford & Mellor 2005; Stewart et al. 2009; Graf & Senn 1999). The cornual nerve block is currently the accepted technique to anesthetize cattle horn prior to removal (Grøndahl-Nielsen et al. 1999). Some studies have combined the cornual block with a ring block to increase the probability of effective anesthesia (Faulkner & Weary 2000). To our knowledge, the efficacy, onset and duration of action of the cornual nerve block has not specifically been evaluated.

Recent advances in drug delivery technology have resulted in needle-free techniques (JET) for intradermal and subcutaneous drug delivery. JET uses a high-velocity stream of fluid to pierce the skin and deliver drugs into the intradermal, subcutaneous or intramuscular spaces (Schramm Baxter & Mitragotri 2004). JET has many potential advantages over needle injections including decreased; pain on delivery, biohazardous waste, tissue trauma and risk of infection.

An eutectic mixture of local anesthetics (EMLA) is used as a topical anesthetic in people undergoing minor medical procedures (Buckley & Benfield 1993). EMLA (Astra-Zeneca Canada Inc., Ontario, Canada) cream contains 2.5% lidocaine and 2.5% prilocaine and application 1–5 hours before a procedure is recommended. EMLA cream could provide a simple, safe method of anesthesia of the horn bud in calves.

The objective of this study was to examine four local anesthetic techniques: cornual nerve block, ring block, percutaneous jet injection and topical EMLA cream, for anesthesia of the horn bud in calves. Efficacy, onset time and the duration of anesthesia were evaluated.

Section snippets

Study design

Eight, 2 month-old male Holstein Friesian calves (65–90 kg) were used in a randomized crossover study. One the first day of the study, calves were randomly assigned to receive one treatment (1–4). On subsequent weeks, calves would receive the next numbered treatment so that each calf received all four treatments with 7 days ‘washout’ between treatments. Calves were purchased from two local farms and individually housed for 2 weeks before the study. The calves had free access to water, calf

Anesthetic treatments

On each treatment day, calves received one of four treatments:

  • Cornual nerve block (C) – 5 mL lidocaine 2% with epinephrine (0.01 mg mL−1) (Lido-2; Rafter 8 Products, Alberta, Canada) was injected under the skin midway between the horn bud and the lateral canthus of the eye, ventral to the frontal crest, using a 20-gauge 2.5 cm needle. Four mL was injected at this location, after ensuring the needle was not in a blood vessel, and the remainder was infiltrated through the tissues on withdrawal

Results

The median baseline positive avoidance response to stimulation was level 6 for all treatment groups. Seven C calves (87.5%), eight R calves (100%), and three JET calves (37.5%) developed cutaneous anesthesia of the horn bud. Topical EMLA cream failed in all calves. In the calf with the failed block in treatment C, cutaneous sensation was mapped using needle prick around the horn bud. This calf had a localized area of sensation at the caudolateral aspect of the horn bud. 6/8 C, 5/8 R and 2/3 JET

Discussion

Two novel techniques of anesthesia, JET and EMLA, of the horn bud were evaluated in this study, and neither was found to be effective. Failure of the JET injection was likely due to poor anesthetic penetration or inadequate drug concentrations around the cornual nerve. Some injections failed to inject all the lidocaine through the skin. In people, ‘wet’ injections can result from a characteristic in the design of the device, use of the device, variations in skin morphology, or some interaction

Acknowledgement

This research project was funded through the Margaret Gunn Endowment Fund.

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