Effect of intravenous regional anaesthesia and regional nerve blocks on blood

The helpful factor which could be as a pain indicator in animal body could be the rate of blood parameters. In other words, any decreasing or increasing rate in concentration of blood parameters in animal serum could identify pain or abnormal conditions in the body. The concentration of hormonal factors such as cortisol concentration as well as metabolic parameters such as serum concentration of lactate, free fatty acids and glucose could indicate the pain in body (CAMBRIDGE et al., 2000). Moreover, severe pain as a stressor whether it would be acute pain or chronic pain could have some physiological effects on the endocrine system. This mentioned stressor can activate the hypothalamic-pituitary-adrenal-thyroid gonadal [HPATG] system which is the main human stress control strategy (TENNANT, 2013). Cortisol secretion is under multihormonal control which during physical

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as well as physiological stress, cortisol can be synthetized and subsequently could be released from the cortex of adrenal glands (AXELROD and REISINE, 1984; BOANDL et al., 1989).

The evaluated results in our study showed that cortisol concentration was raised after turning cows to lateral recumbency in both IVRA and 4-point NBA groups which can demonstrate the effect of lateral recumbency as a stress model on hormonal and metabolic responses of dairy cows. According to our results, increased level of cortisol concentration in both IVRA and 4-point NBA was seen after LR till end of examination’s day. In cattle, the fluctuations of the plasma cortisol concentrations could evaluate the duration of pain-induced distress resulted in some manipulations such as dehorning, castration as well as tail docking (PETRIE et al., 1996a; PETRIE et al., 1996b; ARMSTRONG, 1985; ROBERTSON et al., 1994; MELLOR et al., 1991; COHEN et al., 1990; JOHNSTON and BUCKLAND, 1979). However, the increased level of cortisol concentration in IVRA group was greater before anaesthesia application while in 4-point NBA group that higher rate of cortisol concentration had a higher level after administration of local anaesthesia. The stress response which is any fluctuation in hormonal and metabolic level could happen following any stressors such as injury or trauma (DESBOROUGH, 2000). In calves, application of local anaesthesia can eliminate the plasma cortisol responses before surgical or interventional procedures. For instance, local anaesthesia’s administration before castration could result in lower mean or maximum plasma cortisol concentrations in the first two hours following operation compared to the operated calves without application of local anaesthesia (EARLEY and CROWE, 2002; FISHER et al., 1996). Against, our results did not show any elimination of plasma cortisol concentration following anaesthesia application which could be due to LR. Our results are in agreement with WEBSTER et al. (2013) and JURKOVICH et al. (2015), in which application of local anaesthesia could not reduce the plasma cortisol response following operation may be resulted in tissue inflammation or tissue irritation after local anaesthesia’s application. Additionaly, according to MELLOR and STAFFORD (1997), application of local anaesthesia with lidocaine before electric dehorning of calves could not significantly decline the plasma concentration of cortisol which can be concluded that anaesthesia cannot decrease the stress caused by dehorning. Against, another studies demonstrated that local anaesthesia could prevent the raise of cortisol concentration in plasma in calves only for the duration of effect of local anaesthesia (MCMEEKAN et al., 1998). However, the cortisol response can be virtually eliminated following application of local anaesthesia before manipulating procedures (STAFFORD et al., 2002). On the other hand, application of local anaesthetic can be stressful.

According to BOANDL et al. (1989), injection of local anaesthetic as well as handling and

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dehorning can increase plasma cortisol concentration due to stress induction during these procedures (BOANDL et al., 1989). Moreover, the concentration of cortisol in plasma can be also raised in cattle due to stress of transport, husbandry procedures or any interventions in cattle (MITCHELL et al., 1988; LEY et al., 1996; KENT and EWBANK, 1983). In some studies, as a concequence following castration in calves with acute pain, the increased level of plasma concentration of cortisol has been highlighted (OBERTSON et al., 1994; COHEN et al., 1990; FELL et al., 1986; LEY et al., 1996). However, in our study, there was not seen any remarkable difference between two anaesthetized groups with either intravenous regional anaesthesia or 4-point regional nerve block analgesia related to serum cortisol concentration.

It should be considered that, measuring cortisol concentration could not be a reliable method to recognize pain in dairy cows, in order that stress resulted from any intervention, manipulation and even environmental stress signals such as fluctuations of temperature and so on may cause change in level of serum cortisol concentration. In human, cortisol released due to manipulation could have a complex metabolic impact on protein, fat as well as carbohydrate. For example, cortisol can increase protein breakdown as well as induction of gluconeogenesis which may occur in the liver. Due to inhibition of glucose’s usage in the cells, the glucose concentration would be increased (DESBOROUGH, 2000). Regarding the effect of regional anaesthesia, studies have demonstrated that epidural anaesthesia can prevent endocrine as well metabolic responses in operations of pelvic and lower limbs. By using epidural analgesia before start of operation, increasing the cortisol and glucose concentrations in response to hysterectomy can be prevented. In other words, the glycaemic and adrenocortical responses to the surgery could be abolished by application of regional analgesia (ENQUIST et al., 1977; DESBOROUGH, 2000). Hyperglycemia, loss of body fat as well as negative nitrogen balance could be the integrated effects of glucocorticoids (BAXTER and FORSHAM, 1972). However, in our examination on cattle, glucose concentration had an increased level after anaesthesia application with either IVRA or 4-point NBA. Meanwhile, lactate concentration was raised in both anaesthetized groups from turning cows to LR until returning cows to standing position while after standing position that increased level of lactate concentration decreased till end of examination but did not reach baseline lactate concentration and still was higher than baseline concentration before LR.

However, in our investigation, there was not seen any remarkable difference comparing intravenous regional anaesthesia and 4-point regional nerve block related to measured metabolic as well as hormonal blood parameters.

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