Evaluation of the Analgesic and Clinical Effects Associated with the Subarachnoid Administration of Propofol in Sheep

The objective of this study was to evaluate the toxic, analgesic and clinical effects associated with intrathecal administration of propofol in sheep. Five, healthy adult non-pregnant Awassi sheep were used in the study. Propofol (2.85 mg/kg; n = 4) or normal saline (control, n = 1) was administered into the subarachnoid space at the lumbosacral intervertebral junction. Animals were assessed clinically for toxic signs, analgesia, sedation and ataxia. The heart rate, respiratory rate, rectal temperature, arterial blood pH, HCO3, PaO2 and PaCO2 were recorded before (time = 0) and then at 5, 15, 30, 60, 90 and 120 min after injection of propofol. Tissues from the spinal cord and meninges were evaluated histologically for evidence of local toxic effects due to intrathecal injection of propofol. Following the administration of propofol, sheep showed signs of sedation and were ataxic within 15 min. The sheep developed sufficient surgical analgesia of the caudal abdominal wall, vagina, perinea, pelvic limbs and udder 15 to 30 min following injection of the drug and lasted for over 90 min. Sheep in the treatment group had significantly higher heart rates, PaCO2 and HCO3 values and decreased blood pH. Values of PaO2 increased significantly initially and then decreased while the respiratory rate and rectal temperatures decreased but not significantly. Histological examination of the meninges and spinal cord showed no significant changes. Results of this study showed that a single injection of propofol into the subarachnoid space can result in sufficient surgical analgesia of the caudal abdominal wall, vagina, perinea, pelvic limbs and udder with moderate sedative effect and acceptable clinical and acid-base alterations in sheep.