Spinal Anesthesia With Bupivacaine Versus Prilocaine on Postoperative Shivering After Inguinal Hernia Repair

Inguinal hernia is the most common type of abdominal hernia, more common in men than women. Inguinal hernia repair is performed under general, spinal anesthesia or local anesthesia.

Core body temperature is normally tightly regulated to within a few tenths of a degree. The major thermoregulatory defenses in humans are sweating, arteriovenous shunt vasoconstriction, and shivering.

Spinal anesthesia is considered a safe anesthetic technique for the surgery, however 40 to 60 percent of patients' experience shivering due to vasodilatation, which facilitates rapid heat loss and causes a redistribution of body heat from the core to peripheral tissue. However, perioperative heat loss due to exposure of skin, evaporation from exposed sites, cold intravenous fluids, contribute to factors that predispose shivering. Postoperative shivering can be either thermos-genic with hypothermia or nonthermogenic associated with pain modulation and surgical stress.

Shivering is considered undesirable, as these random spontaneous, asynchronous skeletal muscle contractions increases the basal metabolism with increase in oxygen consumption up to be 600% hypoxemia, metabolic acidosis, triggering myocardial ischemia, increased wound pain, delayed wound healing, as well as increase in blood pressure, intraocular and intracranial pressure.

Bupivacaine is a long acting local anesthetic belonging to the amide group it is more stable and less likely to cause allergic reactions among other local anesthetics however; it delays hospital discharge in ambulatory surgery. Prilocaine is a local anesthetic belonging to the amide group with rapid onset, intermediate potency, and action.

The old local anesthetics prilocaine was reintroduced in the market as hyperbaric prilocaine 2% which provides anesthesia for 75-90 minutes after spinal administration, thus increasingly used in the ambulatory setting.

Since bupivacaine 0.5% has significantly prolonged postoperative analgesic duration versus prilocaine 2%, thus We hypothesis that bupivacaine may have a superior effect on minimizing postoperative shivering through providing better analgesia.

The main aim of this study is to compare spinal anesthesia with prilocaine 2%, versus bupivacaine 0.5% on postoperative shivering during repair of inguinal hernia.