The Efficacy Of Nalbuphine Versus Fentanyl As Additives To Bupivacaine In Spinal Anaesthesia For Internal FixationI Of Tibia

The Efficacy Of Nalbuphine Versus Fentanyl As Additives To Bupivacaine In Spinal Anaesthesia For Internal FixationI Of Tibia

INTRODUCTION Regional techniques, such as spinal anaesthesia may offer advantages over general anaesthesia including reduced stress response to surgery and analgesia extending into the postoperative period.(1,2) Adequate pain management to facilitate rehabilitation and to accelerate functional recovery after lower limb orthopedic surgery is essential to enable patients to resume normal activity as soon as possible.(3) To increase the duration of analgesia produced by local anesthetic, a number of adjuvants have been added through the central neuraxial route.(4) The profound segmental anti-nociception produced by neuraxial opioids in doses much smaller than would be required for comparable anti-nociception if administered systemically has made them very popular and effective in the treatment of many painful states.(5)The anti-nociception is also devoid of motor, sensory and autonomic blockade so there is no paralysis or hypotension. Furthermore, the availability of a specific opioid receptor antagonist naloxone to reverse their action when necessary has made the use of opioids more acceptable.(6) Opioids work in the intrathecal space by activating opioid- receptors in the dorsal gray matter of spinal cord, which modulates the function of afferent pain fibers.(7)Intrathecal and epidural narcotics seem to modulate pain primarily at the spinal cord rather than in the brain as do intravenous narcotics.(8) Site of action in the spinal cord may provide analgesia with less sedation, confusion and nausea, which are adverse effects associated with intravenous narcotics.(9) Various opioids have been used along with bupivacaine to prolong its effect, to improve the quality of analgesia and minimize the requirement of postoperative analgesics.(10,11) The main obstacles for optimal use of opioids are their side effects which include pruritis, nausea/ emesis, constipation, urinary retention, respiratory depression, undesirable sedation and the development of tolerance/ dependence. Though some side effects may be benign but others like respiratory depression can prove to be life threatening.(12-14) Nalbuphine is a semisynthetic opioid with mixed mu antagonist and kappa agonist properties. When used singly or in combination with other agents it has the potential to maintain or even enhance opioid based analgesia while simultaneously mitigating the common mu-opioid side effects. (15) Nalbuphine binds readily to both mu- and kappa-receptors. The binding of nalbuphine to mu receptors only serves to competitively displace other mu-agonists from the receptor, without itself displaying any agonist activity.(16)When nalbuphine binds to kappa-receptors, however, it has an agonist effect. Kappa-opioid receptors are distributed throughout brain and spinal cord involved in nociception. Nalbuphine binds avidly to kappa-receptors in these areas to produce analgesia. This pattern of binding and effects defines nalbuphine as a mixed agonist-antagonist.(17) Fentanyl, a lipophilic opioid has rapid onset of action, It does not tend to migrate intrathecally to the 4th ventricle in sufficient concentration to cause delayed respiratory depression.(18,19)

AIM OF THE WORK The aim of our study is to compare the effect of intrathecal nalbuphine versus intrathecal fentanyl as adjuvants to bupivacaine, as regard the intra-operative and post-operative analgesia, the hemodynamic stability, the onset of sensory/motor block and the duration of action in patients undergoing internal fixation of tibia.

PATIENTS This study will be carried out in El-Hadara University Hospital on sixty patients aged 18-50 years; belonging to American Society of Anesthesiologists (ASA) physical status I and II, scheduled for elective internal fixation of tibia, of expected duration less than 3 h, under subarachnoid block, this prospective study will be done in a double-blinded, randomized way.

Exclusion criteria: