Introduction

Xylazine, one of the alpha2 agonists, has been widely used in veterinary practice both systemically as a sedative and analgesic drug [17], and neuraxially for analgesia in various species [2, 3, 5, 8, 16]. It causes muscle relaxation and, depending on the dose used, it can induce cardiorespiratory depression, a fall in body temperature, a reduction in ruminal activity, a reduction in swallowing (hence, drooling of saliva) with an increased risk of aspiraton, and diuresis [13, 17] (Zuagg and Nussbaum, 1989).

When local anaesthetic agents are administered by the epidural route, they affect both motor and sensory nerves, and motor dysfunction, resulting in severe ataxia and recumbency, is a particular disadvantage for surgery when it is desirable that the animal should remain standing. Ataxia and recumbency may occur also following epidural administration of alpha2 agonists, especially at higher doses, either due to systemic absorption of the drug and/or to local action on motor nerves [14, 19]. However, at appropriate doses, xylazine has been reported to be a suitable agent for providing analgesia without excessive ataxia and recumbency [7, 15, 19, 2, 9]. Upper caudal epidural administration of lidocaine and xylazine combination in cattle provides satisfactory analgesia for some surgical interventions such as fetotomy, repair of recto-vaginal fistulae, replacement of prolapsed uterus, vagina or rectum, facilitiation of embryo transfer, and perineal urethrostomy. Furthermore, this combination has a longer analgesic effect than xylazine used alone and should allow an animal to remain standing [6, 7, 12].

The aim of the present study was to reveal whether epidural administration of xylazine and lidocaine combined with xylazine sedation could provide satisfactory analgesia for some surgical interventions carried out on the lower urinary tract, and on the umbilical and perineal regions.

Materials and methods

The calves (Table 1) exhibited various surgical disorders: urolithiasis (n:2), rectovaginal fistula (n:1), atresia ani (n:2), omphalophlebitis (n:2), omphaloarteritis (n:1) and umbilical hernia (n:2).

Table 1 Age, breed, sex, body weight, site of the epidural injection and surgical procedure for each of the 10 animals
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The older calves were starved for 12 hours prior to operation. After surgical preparation of the sites for the epidural injections and the operation areas, each calf was given 0.05 mg/kg body weight of xylazine intramuscularly for sedation and then the combination of anaesthetic drugs (0.2 mg/kg lidocaine + 0.02 mg/kg xylazine + 5 ml 0.09% NaCl) was injected into one of the following epidural spaces: lumbosacral (L6-S 1; n:5), sacrococcygeal (S5-Co1;n:3) or intercoccygeal (Co1-Co2; n:2).

Heart rate, respiratory rate and body temperature were recorded for each animal before the administration of the drugs and at 5,10,15,30 and 60 minutes afterwards. Responses to needle prick in the perineal and hindlimb areas and the umbilical region were assessed to monitor the effectiveness of analgesia and were graded as follows:

1: Normal reaction to pain sensation

2: Mild tail reflex and pain by needle prick

3: Tail reflex absent, mild response to needle prick

4: Tail and needle prick reflexes absent, good analgesia for surgery.

These tests were repeated at 1, 3, 5, 10, 15, 30, 60, 90, 120, 150 and 180 minutes after the epidural injection.

Statistical analysis

Measurements were compared with baseline values (time:0) by performing Anova followed by Tukey Test using Minitab statistical program [11]. Values were given as mean ± standard deviation. Statistical difference was considered significant at p < 0.05.

Results and discussion

Sedation with xylazine and epidural administration of the xylazine-lidocaine combination resulted in a significant decrease of respiratory rate at 10, 15 and 60 minutes (p < 0.01) and of body temperature at 60 minutes (p < 0.05); heart rate was decreased but the reduction was not statistically significant (Table 2).

Table 2 Alterations in body temperature and heart-respiratory rates (mean ± SD) in 10 calves at 0, 5, 10,15,30 and 60 minutes after sedation with xylazine and epidural administration of xylazine and lidocaine combination
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Analgesia started at 3 minutes in the perineal region and at 15 minutes in the umbilical region following epidural injection. Perineal analgesia continued up to 150 minutes (Figure 1; Table 3).

Figure 1
figure 1

Appropriate time intervals for surgical internevtion after administration of anaesthetic drugs.

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Table 3 Distribution of the 10 calves amongst the grades of analgesia at intervals following sedation with xylazine and epidural injection of the lidocaine and xylazine combination
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However, adequate analgesia for the surgery was not achieved at the cranial side of the umbilicus and, therefore, surgical interventions in this region were performed with local infiltration anaesthesia. Intervals during which analgesia was sufficient for surgery are shown in Figure 1.

In order to avoid complications resulting from general anaesthesia, epidural injection of local anaesthetic agents has been widely reported for surgical interventions in the perineal region in cattle, horses, goats and sheep [7, 6, 8, 18]. Investigation revealed that epidural administration of local anaesthetic drugs when used alone had various side effects and, although providing satisfactory analgesia for laparotomy, it did not always prevent response to visceral manipulation [6, 10, 18]. On the other hand, epidural injection of xylazine resulted in adequate analgesia, albeit with a slower onset than was achieved by the administration of local anaesthetic drugs; however, bradycardia, respiratory depression and hypothermia have been reported [1, 2, 5, 10]. In the present study, the side effects of local anaesthetic/xylazine combination were minimized, and analgesia was prolonged by the low dosage of xylazine used for sedation and regional analgesia.

The results of the present study indicated that epidural administration of xylazine-lidocaine combination following sedation with xylazine provided satisfactory analgesia for perineal and lower urinary tract surgery without any complications. However, as observed by Lewis et al. [10], satisfactory analgesia for umbilical surgery was not achieved.