Abstract
The aim of this study was to compare fentanyl-based versus remifentanil-based anesthesia with regards to the intraoperative hemodynamic stress response and recovery profiles in patients undergoing Le Fort I osteotomy. Seventeen patients were randomly divided into two groups: patients in the F-group received 2 μg/kg fentanyl intravenously followed by an infusion of 0.03–0.06 μg/kg/min, while patients in the R-group received a 0.5 μg/kg bolus of remifentanil followed by an infusion of 0.0625–0.250 μg/kg/min. Mean arterial pressure and heart rate were recorded at the following points: before anesthetic induction, at endotracheal intubation, 5 min after intubation, at incision, just before the osteotomy, during the osteotomy, during the maxillary fracturing, at suturing, at extubation, 5 min after extubation, and then 15 and 30 min postoperatively. Heart rate and mean arterial pressure were significantly lower in the R-group in comparison to the F-group from t 1 to t 9 ( P < 0.05). All measured recovery times were significantly shorter in the R-group ( P < 0.05). The incidence of postoperative side effects was comparable between groups. Remifentanil-based anesthesia is an appropriate alternative to fentanyl during Le Fort I orthognathic surgery; it promotes hemodynamic stability, blunts the stress response to noxious stimuli, and provides a better recovery profile.
Maxillofacial orthognathic surgery involves the surgical manipulation of facial skeletal elements for the correction of various forms of dentofacial skeletal deformities in order to correct malocclusion and facial asymmetry. Orthognathic surgery, including the Le Fort I osteotomy and subsequent maxillary fracturing, has a marked impact on the cardiovascular stress response, which can result in an unchecked increase in the mean arterial blood pressure (ABP) and heart rate (HR). Frequent adjustments to the depth of anesthesia and analgesia, and the subsequent pharmacological interference, are required to blunt such hemodynamic stress responses. The use of high-dose opioids can be effective, but has the drawbacks of respiratory depression and delayed recovery. In patients undergoing orthognathic surgery, a compromised airway postoperatively is a particular concern.
Theoretically, it would be extremely beneficial in such clinical situations to utilize an adjuvant treatment that is capable of effectively controlling autonomic responses, while facilitating a faster recovery with fewer side effects. Remifentanil may be such an adjuvant anesthetic as it is a potent opioid with a uniquely short duration of action. Remifentanil has been used synergistically with both intravenous (i.v.) and inhalational anesthetics. It provides strong analgesia and extremely deep levels of surgical anesthesia to manage undesirable stress responses. Remifentanil can decrease the sympathetic flow and increases vagal tone, allowing the maintenance of a physiological HR and ABP during surgery.
The ultra-short duration of action of remifentanil has been attributed to its ester linkage, which is metabolized directly in the plasma by non-specific esterases. This enables advantageous rapid postoperative recovery pharmacokinetics, which has been proven to be true regardless of the infused dose and duration of anesthesia.
This study was designed to compare the use of fentanyl-based versus remifentanil-based anesthesia with specific regards to the intraoperative hemodynamic stress response and recovery profiles in patients undergoing a Le Fort I orthognathic osteotomy.
Methods
This was a prospective, randomized, comparative study; all patients provided written informed consent before study enrollment. Seventeen otherwise healthy patients aged 18–30 years of both genders, with American Society of Anesthesiologists (ASA) physical status of I, were included in the study. They all had indications for single jaw orthognathic surgery, namely a Le Fort I osteotomy.
All patients were submitted to routine preoperative evaluation and laboratory studies in accordance with the hospital’s standard protocol. All patients were fasted overnight and received lorazepam 2 mg and ranitidine 150 mg orally as a pre-anesthetic 2 h before the operation. This was followed by glycopyrrolate 0.2 mg intramuscularly 30 min before the procedure. Monitoring included electrocardiography (ECG), pulse oximetry (SpO 2 ), capnography, spirometry, end-tidal gas analysis, body temperature, bispectral index (BIS), and neuromuscular transmission (TOF; transmission with four stimulators). A 22-gauge catheter was inserted into a radial artery for direct determination of arterial pressure. Two cannulae were inserted at different sites in the same arm, one for the infusion of narcotics via a standard syringe pump (Diprifusor, Grasepy 3500, SIMS, Waterford, Herts, UK) and the other for fluids and other medications. Thirty minutes before the induction of anesthesia, all patients received routine prophylactic antibiotics, 300 mg of clindamycin i.v. and then 300 mg every 6 h. Also dexamethasone 0.1–0.3 mg/kg i.v. was given to minimize postoperative edema.
Patients were randomly allocated by sealed envelope technique to one of two groups, one receiving fentanyl (F-group) and the other remifentanil (R-group). In the F-group, patients received a bolus dose of fentanyl (2 μg/kg) before the induction of anesthesia, followed by a continuous infusion at a rate of 0.03–0.06 μg/kg/min. In the R-group, patients received an initial bolus of 0.5 μg/kg remifentanil over 60 s before the induction of anesthesia, followed by a continuous infusion of 0.0625–0.250 μg/kg/min.
Anesthesia was induced in both groups with intravenous 1% propofol (2 mg/kg) and cisatracurium (0.15 mg/kg) to facilitate nasotracheal intubation. An 18-gauge nasogastric tube and a temperature probe were placed in the esophagus. Both tubes were taped to the nasotracheal tube with the same curve. The tubes were taped to the patient’s head after being padded with foam. An oropharyngeal seal was obtained by packing to prevent any leakage of blood into the stomach.
After the appropriate preparation and draping, the surgeon injected the initial surgical site with 3.6 ml 2% lidocaine with epinephrine (1:80,000). Anesthesia was maintained with 50% oxygen in air, and sevoflurane was administered at one minimum alveolar concentration (MAC) to achieve end-tidal concentrations of between 1% and 3%. Doses for anesthetics and opioids were adjusted according to the BIS monitoring values. The aim was to maintain the BIS between 40 and 60. Neuromuscular blockade was maintained by administering intermittent boluses of cisatracurium. Ventilation was controlled to maintain an end-tidal carbon dioxide tension from 35 to 40 mmHg. The patients were placed in a 10° head-up position before surgery began.
Surgery was performed using the same anesthesia and surgical protocols, and all operations were performed by the same surgical team; the surgical team was unaware of the group to which the patients belonged. The anesthesiologists and data collectors in the operating room (OR) were aware of the opioids administered to both groups, and were informed about the study design.
The design of the study was to control the hemodynamic response; hence the mean arterial blood pressure (MAP) values were adjusted to between 60 and 75 mmHg. In both groups, signs of inadequate anesthesia (e.g. BIS > 60 or increases in the MAP greater than the targeted MAP) or somatic responses (e.g. movement, tearing, or sweating) were treated by initially increasing the depth of anesthesia by raising the concentration of sevoflurane in a stepwise manner to a maximum end-tidal concentration of 3%. Then, increases in the infusion rate were made by increments of 0.016 μg/kg/min fentanyl in the F-group or 0.05 μg/kg/min remifentanil in the R-group. A minimum of 1 min was required between the infusion rate increases. If the target MAP could not be achieved by the uppermost infusion rate of opioid, labetalol was given as a ‘rescue’ medication in 5-mg increments every 5–10 min to achieve the desired effect.
Excessive depth of anesthesia in both groups was judged by BIS monitoring, and hypotension and/or bradycardia was treated initially by decreasing the concentration of sevoflurane as appropriate, together with increasing intravenous fluids. If this intervention was not effective, the infusion rate of fentanyl or remifentanil was decreased gradually to the lowermost values. A HR < 50 beats/min was treated with 10 μg/kg atropine intravenously. A MAP < 50 mmHg was treated with 6 mg i.v. ephedrine.
Approximately 20 min before the end of the procedure, patients in both groups received 1 g paracetamol i.v. and 1 mg/kg tramadol i.v. for postoperative analgesia, as well as ondansetron (4 mg, i.v.) to prevent postoperative nausea and vomiting. At the end of surgery, the administration of sevoflurane, nitrous oxide, fentanyl, and remifentanil were stopped simultaneously and 100% oxygen was administered. Stomach suctioning was applied and the nasogastric tube was removed. The oral cavity was inspected under direct vision and the throat pack was removed. The residual neuromuscular blockade was reversed with an i.v. combination of 0.05–0.075 mg/kg neostigmine and 0.005–0.01 mg/kg glycopyrrolate, and the patients were tracheally extubated when their protective airway reflexes returned and the patient was breathing spontaneously, responding to verbal commands, making purposeful movements, and the T4/T1 ratio was 90%. After complete recovery from the anesthetic, patients were transferred to the post-anesthesia care unit (PACU) for a minimum of 1 h. Patients were given oxygen via a facemask at a rate of 3 l/min throughout this period.
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