Clinical evaluation of clonidine added to lidocaine solution for subarachnoid analgesia in sheep

Abstract

Clonidine (CL) is a alpha2-adrenergic agonist that produces analgesia in animals and humans by a non-opiate alpha2-adrenergic action in the spinal cord dorsal horn. The objective of this prospective randomized study was to investigate the clinical effects of CL/lidocaine (LD) combination administered by the subarachnoid route in sheep. Each sheep received each of three treatments, at no shorter than weekly intervals. Treatments consisted of 0.003 mg/kg CL, 1.2 mg/kg LD and a combination of CL (0.003 mg/kg) and LD (1.2 mg/kg) (CLLD). Subarachnoid injections were given in all animals between the last lumbar and first sacral vertebra. Heart rate (HR), arterial pressures, respiratory rate, rectal temperature, analgesia, sedation, and motor blockade were determined before drug administration (basal) and 5, 10, 15 and 30 min after drug administration, and at 30-min intervals until loss of analgesia occurred. The duration of analgesia after subarachnoid CLLD administration was 187 +/- 24 min (mean +/- SD), i.e. more than twice of that obtained with CL (99 +/- 19 min) or LD (55 +/- 4.4 min) alone. In all sheep, CL, administered either alone or with LD, induced moderate sedation. After subarachnoid administration of three treatments, all sheep had ataxia and subsequent sternal recumbency. The CL treatment causes decreases in blood pressure (diastolic arterial pressure and mean arterial pressure) and HR. Data suggest that the CLLD combination could be used subarachnoidally in sheep requiring prolonged surgery.

Comparison of analgesic and systemic effects of bupivacaine, methadone, or bupivacaine/methadone administered epidurally in conscious sheep

“…However, intrathecal ropivacaine did not cause any damage to rabbit spinal cord even at higher concentrations . One alternative to increasing the duration of analgesic effect and reducing the concentration of the local anaesthetic is combining of these agents with other drugs such as xylazine, ketamine, clonidine, tramadol and morphine, which has shown varying degrees of success in small ruminants.…”

Anestesia peridural com lidocaína isolada ou associada à clonidina: efeito cardiorrespiratório e analgésico em cães

“…No atual estudo, o volume administrado no espaço peridural foi o mesmo em ambos os tratamentos, visto que, no tratamento C, o volume de lidocaína foi reduzido, visando-se a perfazer o volume final de 0,25ml kg -1 , conforme preconizado pela literatura (GASPARINI et al, 2007;CASSU et al, 2010). Dessa forma, sugere-se que a migração cranial do bloqueio possa ser atribuída às características de lipossolubilidade da clonidina (EISENACH et al, 1987), corroborando resultados prévios descritos em ovinos (DE ROSSI et al, 2006).…”

Use and Efficacy of Analgesic Agents in Sheep (Ovis aries) Used in Biomedical Research

“…45,67 These studies recorded time to voluntary leg withdrawal from the stimulus. Other studies utilized superficial or deep muscle pinpric ks, 3,[11][12][13][14]17,21,22,26,39,42,59 as an alternative method of mechanical stimulation of so-called 'first-pain.' 9 This method tends to evaluate analgesia by using a scale based on reaction to the stimulus.…”

“…9 This method tends to evaluate analgesia by using a scale based on reaction to the stimulus. 14 To assess diffusion or extent of analgesia, skin pricks and deep muscle pricks are made in adjacent dermatomic regions, beginning at the tail and moving cranially. 14 Noxious stimuli activate afferent nociceptors, which trigger multiple levels of information processing, not all of which go through higher brain centers.…”

“…14 To assess diffusion or extent of analgesia, skin pricks and deep muscle pricks are made in adjacent dermatomic regions, beginning at the tail and moving cranially. 14 Noxious stimuli activate afferent nociceptors, which trigger multiple levels of information processing, not all of which go through higher brain centers. This higher-order brain processing creates the experience of pain, which is considered to influence animal wellbeing.…”