Comparative evaluation of atracurium and rocuronium as muscle relaxants in buffalo

Introduction

Muscle relaxation is an integral component of anaesthetic triad (Amnesia, analgesia and muscle relaxation) for achieving smooth and safe surgical procedures. Orthopedic and thoracic surgeries are difficult to perform without adequate muscle relaxation especially when the subject is a large muscular species. So, neuromuscular blocking (NB) agents have become an essential component of anaesthetic regimen for such surgeries. NB agents cause little or no significant systemic effects. It is possible to produce quickly and with certainty, any degree of muscle relaxation without influencing the excitability and functioning of the central nervous and cardiovascular systems (Hall et al., 2001) [7] . Neuromuscular blocking agents interfere with acetylcholine inhibiting receptor-coupled trans-membrane ion movements necessary for muscle contraction (Bouzat et al., 2004 and Unwin, 2005) [2,14] thereby resulting into skeletal muscle paralysis and muscular relaxation (Kita and Goodkin, 2000) [10] . NB agents reduces the dose of anaesthesia, facilitate endotracheal intubation, skeletal muscle tone relaxation at light planes of anaesthesia, orthopedic manipulations and prevention of patient movement during delicate ocular, neurological, or cardiac surgery (Taylor, 2006; and Martinez and Keegan, 2007) [13,11] . The introduction of NB drugs into clinical practice has revolutionized the practice of anaesthesia in human patients. It has improved the safety and results of many established surgical procedures, as they produce negligible effect on heart rate and arterial blood pressure in anaesthetized patients (Barnes et al., 1982) [1] . The literature related to evaluation and use of NB drugs in bovines and specially in buffaloes are scarce, however, the increased value of individual buffalo leads to increased demand for orthopedic and thoracic surgeries in these animals. Atracurium and rocuronium are recent non-depolarising neuromuscular blocking agents with minimum depressant effects on vital systems in different species. So, the study was planned to evaluate their safety and efficacy in buffalo for their intended future use.

Atracurium was used at different dose rates of 0.1, 0.2, 0.3, 0.35, 0.375 and 0.4 mg per kg body weight and Rocuronium at 0.15, 0.2, 0.25 and 0.3 mg per kg body weight intravenously. Based on the results of pilot trials, the dose rate of atracurium and rocuronium was chosen as 0.4 mg/kg and 0.2 mg/kg body weight intravenously, respectively for further study. The facility of positive pressure ventilation was kept available throughout the experiment. All the animals were kept off feed for 24 hours and off water for 12 hours prior to experiment. The animals were comfortably secured in standing position inside a chute, physiological parameters were recorded, blood samples were collected and then atracurium 2 or rocuronium 3 were injected in the jugular vein as per the protocol and the parameters were recorded.

Haematological and Biochemical Study

For haematological and biochemical analysis, blood samples were aseptically collected from jugular venipuncture before drug administration, at five minute of injection, at recovery and at 24 hours of recovery. Haematological parameters were estimated in automatic analyser MS4 after collecting blood samples in vials containing EDTA. For analysis of biochemical parameters blood was collected in two sets of test tubes for each animal. One containing 3.8% sodium fluoride solution (10 mg/ml of blood) for estimation of glucose and other set containing heparin (10 units/ml) for estimation of blood urea nitrogen, creatinine, bilirubin, cortisol, cholesterol, triglycerides, total plasma proteins, albumin, alanine amino transferase, aspartate amino transferase, lactate dehydrogenase, gamma glutamyl transferase, alkaline phosphatase, calcium, phosphorus, sodium, potassium and chloride. Plasma was harvested by centrifugation at 3000 rpm for 20 minutes and then stored at-20 °C. Biochemical parameters were analysed with automatic analyzer using commercially available standard system pack kits. Sodium, potassium and chloride were analyzed with automatic electrolyte analyzer.

The statistical analysis of data was done by one-wayanalysis of variance and Duncan's multiple range test (Duncan, 1955) [5] . The comparison between the groups had been analyzed using unpaired t-test. The significant difference was considered if p<0.05.

Results and Discussion

The recorded lower weak time, down time, time for chin on ground, turning of neck, lateral recumbency, salivation, mouth gag application and intubation time were significantly lower for rocuronium than atracurium (Table - 1). This shows the rapid onset of action of rocuronium as compared to atracurium. Whalley et al., 1998 [15] also reported to faster tracheal intubation on rocuronium administration, however, extubation time, regaining of sternal recumbency, standing with ataxia, standing without ataxia and walking with ataxia did not differ significantly between rocuronium and atracurium. The time of spontaneous recovery of train of four twitches to 70% was also similar for both agents. Cason et al., 1990 [4] have also reported similar findings. The time for the loss of tongue reflex and jaw tone in buffaloes was markedly less for rocuronium as compared to atracurium. Rocuronium also took lower time for loss of swallowing reflex, fore limb tone, hind limb tone, prepucial and scrotal tone was also recorded for rocuronium than atracurium which may be due to faster onset of action of former than later (Whalley et al., 1998) [15] . However, there was no significant difference in regain of any reflexes between the two drugs (Table-2). There was no significant difference in physiological parameters induced after administration of NB drugs (Table 3). The difference in the base values was within the normal physiological limits (Hafez, 1968).

Hematological Parameters

The haematological parameters of the animals are recorded in Table-4 showing no significant variation.

Biochemical parameters

There was a significant difference at recovery in ALT between the groups (Table -4). The lower value in group 1 might indicate low stress on liver induced by atracurium as compared to rocuronium as it is metabolized by Hoffman elimination which depends upon pH and temperature rather than hepatic pathways (Stenlake et al., 1981 and Hughes, 1986). However, the total protein between the groups varied significantly before drug administration, at recovery and at 24 hours of recovery between groups. Both groups differed at base values and at 24 hours of recovery which might nullify undesirable effects due to administration of these NB agents. The serum potassium and chloride level also varied significantly at recovery between the groups but it remained within normal limits.

Conclusion

Rocuronium was found to be better muscle relaxant than atracurium in terms of fast onset of action, shorter duration, rapid and smooth recovery and more cardiovascular stability in buffaloes.

Acknowledgement

AcknowledgementThe authors are thankful to Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar, Haryana for providing all facilities, resources and support required for this research.

References

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