RESEARCH PAPER
Evaluation of analgesic, sympathetic and motor effects of 1% and 2% lidocaine administered epidurally in dogs undergoing ovariohysterectomy

https://doi.org/10.1016/j.vaa.2020.07.034Get rights and content

Abstract

Objective

To compare, versus a control, the sensory, sympathetic and motor blockade of lidocaine 1% and 2% administered epidurally in bitches undergoing ovariohysterectomy.

Study design

Randomized, blinded, controlled clinical trial.

Animals

A total of 24 mixed-breed intact female dogs.

Methods

All dogs were administered dexmedetomidine, tramadol and meloxicam prior to general anesthesia with midazolam–propofol and isoflurane. Animals were randomly assigned for an epidural injection of lidocaine 1% (0.4 mL kg−1; group L1), lidocaine 2% (0.4 mL kg−1; group L2) or no injection (group CONTROL). Heart rate (HR), respiratory rate (fR), end-tidal partial pressure of carbon dioxide (Pe′CO2), and invasive systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures were recorded every 5 minutes. Increases in physiological variables were treated with fentanyl (3 μg kg−1) intravenously (IV). Phenylephrine (1 μg kg−1) was administered IV when MAP was <60 mmHg. Postoperative pain [Glasgow Composite Pain Score – Short Form (GCPS–SF)] and return of normal ambulation were recorded at 1, 2, 3, 4 and 6 hours after extubation.

Results

There were no differences over time or among groups for HR, fR, Pe′CO2 and SAP. MAP and DAP were lower in epidural groups than in CONTROL (p = 0.0146 and 0.0047, respectively). There was no difference in the use of phenylephrine boluses. More fentanyl was administered in CONTROL than in L1 and L2 (p = 0.011). GCPS–SF was lower for L2 than for CONTROL, and lower in L1 than in both other groups (p = 0.001). Time to ambulation was 2 (1–2) hours in L1 and 3 (2–4) hours in L2 (p = 0.004).

Conclusions and clinical relevance

Epidural administration of lidocaine (0.4 mL kg−1) reduced fentanyl requirements and lowered MAP and DAP. Time to ambulation decreased and postoperative pain scores were improved by use of 1% lidocaine compared with 2% lidocaine.

Introduction

Epidural administration of local anesthetics is a widely used technique in veterinary medicine for several surgical procedures, including ovariohysterectomy (Jones 2001; Almeida et al. 2007; Natalini 2010; Diniz et al. 2013; Ismail 2016; Hermeto et al. 2017). However, conduction block of sympathetic and motor nerves from epidurally administered local anesthetics may limit the use of this technique because the vasodilatory effects of general anesthetics may be augmented or delay to ambulation may extend time to discharge (Torske & Dyson 2000; Brown 2005). When the volume of the epidural solution remains the same, the duration and magnitude of conduction block is associated with the dose of the local anesthetic (Gomez de Segura et al. 2009). Solutions containing low concentrations of bupivacaine and ropivacaine have been successfully used to provide effective epidural analgesia while minimizing the magnitude and duration of motor blockade (Lacassie et al. 2007; Veering 2003; Gomez de Segura et al. 2009; Abelson et al. 2011).

Lidocaine is the most widely used local anesthetic in veterinary practice (Vickroy 2018). When injected epidurally in dogs at a concentration of 2% and a volume of 0.3 mL kg−1, lidocaine results in effective analgesia and motor block lasting approximately 120 minutes (Almeida et al. 2010). Data on the effects of 1% lidocaine administered epidurally in dogs are scarce. Therefore, we compared the sensory, sympathetic and motor blockade of lidocaine 1% and 2% administered epidurally in bitches undergoing ovariohysterectomy, and compared them with a control group without epidural anesthesia. We hypothesized that 1% lidocaine epidurally would result in 1) superior postoperative analgesia than a control group without an epidural; 2) fewer animals with intraoperative arterial hypotension; and 3) a shorter duration of motor block than dogs administered 2% lidocaine epidurally.

Section snippets

Animals

The Animal Care and Use Committee of the Faculty of Veterinary Sciences, UNCPBA, Argentina, approved the protocol (no. 087/04). A group of 24 mixed-breed intact female dogs from a local rescue shelter [mean ± standard deviation (SD)] aged 2.4 ± 1.4 years and weighing 20.0 ± 5.4 kg admitted for ovariohysterectomy were enrolled in a randomized, blinded, controlled study. Dogs were classified as American Society of Anesthesiologists physical status 1 based on physical examination, complete blood

Results

All dogs completed the procedures without intraoperative and postoperative complications. There were no differences among groups for age, body weight, dose of propofol, duration of anesthesia or duration of surgery (Table 1).

There were no differences over time or among groups for HR, fR, Pe′CO2 and SAP (p = 0.08, 0.09, 0.14 and 0.56, respectively). However, MAP and DAP were lower in groups L1 and L2 than in group CONTROL (p = 0.0146 and 0.0047, respectively) (Fig. 1).

There was no difference in

Discussion

Sensory nerve fibers from the dorsal root ganglia of the caudal thoracic (T10) to the cranial lumbar (L4) segments innervate the ovaries in dogs (Chien et al. 1991). Similar spinal segments (from T9 to L3) supply the abdominal muscles, subcutaneous tissue, abdominal skin and the underlying parietal peritoneum (Evans & de Lahunta 2013). In the current study, a lidocaine volume of 0.4 mL kg−1 for epidural injection was based on a study that demonstrated that a total volume of 0.4 mL kg−1 of

Conclusion

Lumbosacral epidural administration of 1% or 2% lidocaine at a volume of 0.4 mL kg−1 resulted in a reduction of intraoperative fentanyl administration without significant intraoperative cardiovascular and respiratory rate alterations compared with no epidural treatment in bitches undergoing ovariohysterectomy. Compared with 2% lidocaine, epidural lidocaine 1% resulted in lower postoperative pain scores and a shorter time to return to ambulation.

Acknowledgements

This study was funded by the Proyecto CyT Estratégico Res. de Consejo Académico 09/2018 (2017–2018) grant from the Facultad de Ciencias Veterinarias de la UNCPBA, Argentina.

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