RESUMO
BACKGROUND: Propofol is an intravenous anesthetic that is widely used to anesthetize patients during neurosurgical procedures. Although propofol is considered to be an essential component of contemporary management of acute brain injury in the operating room and in critical care settings, propofol-induced hypotension (PIH) remains a frequent and undesirable side effect. After 3 decades of clinical use, multiple proposed causes of PIH, and conflicting experimental results, the mechanism of PIH is still a puzzle for neuroscience and anesthesiology. This study evaluated the role of opioid receptors in PIH. METHODS: Pentobarbital-anesthetized rats were subjected to systemic or central pretreatment with naloxone followed by intravenous or central administration of propofol. RESULTS: In the absence of pretreatment with naloxone, intravenous (7.5 mg/kg) and intracistenal propofol (10 µg) injection induced 45% and 35% reductions in the mean arterial pressure, respectively (P<0.05). Both systemic (5 mg/kg) and central (100 µg) pretreatment with naloxone prevented PIH without independently affecting mean arterial pressure. CONCLUSIONS: This experiment in anesthetized rats indicates that central and peripheral opioid receptor blockade prevents PIH, suggesting that these receptors are involved in the cardiovascular alterations elicited by propofol administration.
