The Effects Of Remifentanil Used For Controlled Hypotension On Nasal Mucosal Blood Flow In Rabbits

Objective:Nasal Endoscopic Surgery (NES) is a new technique being developed in recent years. Because of the narrow nasal passage, abundant vascular systems, and the complicated structure, intraoperative hemorrhage is easy to appear, the operation is effected, and the risk and complications of surgical treatment is increased. To avoid hemorrhage and obtain a clear operational field, the technique of controlled hypotension has been applied in nasal endoscope operation wider and wider.The definition of operational field and the blood loss during operation may vary based on different drugs used for controlled hypotension. Remifentanil hydrochloride, a new ultra-short-actingμ-opioid receptor agonist, is now currently used in propofol total intravenous anesthesia (propofol-TIVA). Compared with other comparable drugs such as fentanyl or alfentanil, remifentanil appears to offer a superior intraoperative hemodynamic stability during stressful surgical events and maintains intact cerebral blood flow reactivity, Meanwhile, it appears to provoke moderate to mild hypotension. To observe the change on Heart rate (HR), mean arterial pressure (MAP), common carotid artry blood flow (CABF) and nasal mucosal blood flow (NBF) of New Zealand rabbit. To assess the feasibility of remifentanil used for controlled hypotension during nasal endoscope operation and the advantage of it compared with nitroprusside and esmolol.Methods:Sixty New Zealand rabbit, aged 120-150d old, weighing approximately 1.8-2.2kg,were randomly divided into three groups:R group remifentanil-infusion (n=20), S group SNP-infusion (n=20) and E group esmolol-infusion (n=20).Anesthesia was induced with ketamine 2mg/kg. Tracheostomy was performed via infiltration anesthesia with 0.5 mL of 1%lidocaine hydrochloride solution, and then a 20F pediatrictracheal tube was inserted into the trachea and fixed. Intravenous indwelling catheters were placed in the right femoral artery and the left posterior auricular marginal vein and were used for measurement of arterial pressure and as routes of fluid infusion and drug administration, respectively. Arterial pressure was recorded continuously via a pressure transducer and heart rate was calculated from pressure waveforms. Ringer solution was infused at a rate of 5ml·kg-1·h-1. Muscular relaxation was induced by administration of 0.6 mg/kg atracurium and animals were placed on controlled ventilation with a tidal volume of 30 to 50 mL and a respiratory rate of 35 to 50 breaths/min. Anesthesia was maintained with propofol 4～6 mg·kg-1·h-1. After cardiorespiratory parameters had been stabilized for at least 30min, remifentanil, nitroprusside or esmolol. was infused. In the R group, remifentanil was infused at a rate of 0.25μg·kg-1·min-1. In the S group, nitroprusside was infused at a rate of 80μg·kg-1·min-1 to maintain the MAP no less than 60 mmHg. In the E group, esmolol was infused at a rate of 150μg·kg-1·min-1. HR, MAP, CABF and NBF were measured during each period before and during the infusion of drugs.Results:1. interior-group comparison:In R group,MAP,HR,and CABF showed mild decrease during infusion remifentanil, Whereas NBF showed signifcant decrease in R group (P<O.05). In S group, MAP and CABF showed a signifcant decrease during infusion nitroprusside (P<0.05), whereas, HR and NBF showed signifcant increase in S group (P<O.05). In E group, MAP showed mild decrease during infusion esmolol, meanwhile, MAP and NBF showed signifcant decrease in E group (P<0.05)2. The decreases in MAP measured as percent change were greater in S group than in R group (P<0.05).NBF showed signifcant increase in S group,but it showed signifcant decrease in R group.3. The decreases in MAP measured as percent change were significantly greater in E group than in R group (P<0.05).NBF were no significant difference between the R group and the E group (P>0.05)4. A significant negative correlation was observed between MAP and NBF in S group(P<0.05),howere, little correlation was observed between MAP and NBF in R group and E group. In all groups,the corrrlation between MAP and NBF were not significant (P>0.05)Conclusions:Our findings suggest that compared with traditional drugs used for controlled hypotension such as nitroprusside and esmolo, infusion of remifentanil reduces NBF, as does deliberate hypotension, without a major decrease in MAP and CABF. Remifentanil may be safer and more effective in nasal endoscopic surgery.