The effects of melatonin premedication on propofol and thiopental induction dose-response curves: a prospective, randomized, double-blind study.

BACKGROUND: The effect of melatonin on the intraoperative requirements for i.v.anesthetics has not been documented. We studied the effect of melatonin premedication on the propofol and thiopental dose-response curves for abolition of responses to verbal commands and eyelash stimulation. METHODS: This prospective, randomized, double-blind study included 200 adults with ASA physical status I. Patients received either 0.2 mg/kg melatonin or a placebo orally for premedication (n = 100 per group). Approximately 50 min later, subgroups of 10 melatonin and 10 placebo patients were administered various doses of propofol (0.5, 1.0, 1.5, 2.0, or 2.4 mg/kg) or thiopental (2.0, 3.0, 4.0, 5.0, or 6.0 mg/kg) for anesthetic induction. The ability of each patient to respond to the command, "open your eyes," and the disappearance of the eyelash reflex were assessed 60 s after the end of the injection of propofol or thiopental. Dose-response curves were determined by probit analysis. RESULTS: Melatonin premedication decreased thiopental ED50 values for loss of response to verbal command and eyelash reflex from 3.4 mg/kg (95% confidence interval, 3.2-3.5 mg/kg) and 3.7 mg/kg (3.5-3.9 mg/kg) to 2.7 mg/kg (2.6-2.9 mg/kg) and 2.6 mg/kg (2.5-2.7 mg/kg), respectively (P < 0.05). Corresponding propofol ED50 values decreased from 1.5 mg/kg (1.4-1.6 mg/kg) and 1.6 mg/kg (1.5-1.7 mg/kg) to 0.9 mg/kg (0.8-0.96 mg/kg) and 0.9 mg/kg (0.8-0.95 mg/kg), respectively (P < 0.05). CONCLUSIONS: Melatonin premedication significantly decreased the doses of both propofol and thiopental required to induce anesthesia.

Lactate and acid base changes during laparoscopic cholecystectomy.

BACKGROUND: The observation of hemodynamic and metabolic impairment related to CO2 pneumoperitoneum and postoperative mesenteric ischemia reports following laparoscopic procedures have raised concern about local and systemic effects of increase intraabdominal pressure during laparoscopic procedures. The present study aims to evaluate the metabolic and acid base responses of using high pressure versus low pressure pneumoperitonium in patients undergoing laparoscopic cholecystectomy in a prospective randomized clinical trial. PATIENTS AND METHOD: 20 ASA I-II patients scheduled for elective laparoscopic cholecystectomy were randomly allocated to one of two study groups; high pressure pneumoperitoneum 12-14mmHg (HPP, n=10) versus low pressure pneumoperitoneum 6-8mmHg (LPP, n=10) undergoing laparoscopic cholecystectomy. Arterial blood gases and lactate levels were determined after induction of anesthesia (before pneumoperitonium), then after 10 min, then 30 min after insufflations and at the end of surgery and 1 hour postoperatively. Nurses in recovery unit reported pain assessment starting postoperatively until 3 hours on a 10mm VAS (0-10). Statistical significant was established at P<0.05. RESULT: Bicarbonate was significantly (P>0.0412) lower in high pressure group at 30 min and 60 min after insufflations. In high pressure group lactate levels increased significantly as compared to low pressure group, (at 30 minutes after the establishment of abdominal pneumatic inflation P<0.006 and remained significantly increased (P<0.001) until the end of surgery and one hour thereafter) (P<0.001). The mean postoperative pain score during second hour (VAS) at HPP group was 7.4 +/- 1.17 which is significantly (P < or = 0.006) higher than pain score in LPP group 5.0 +/- 1.886. Shoulder tip pain was reported in 3 patients in the high pressure group and only one patient in the lower pressure group. CONCLUSION: High-pressure pneumoperitonium causes statistically significant elevation in the arterial lactate level intraoperatively until one hour post operatively. It also causes higher pain score and shoulder tip pain.

The dose of succinylcholine required for excellent endotracheal intubating conditions.

In this prospective, randomized, double-blind, placebo-controlled study, we attempted to define the dose of succinylcholine that provides excellent intubation conditions in patients within 60 s during simulated rapid-sequence induction of anesthesia. Anesthesia was induced in 180 patients with 2 microg/kg fentanyl and 2 mg/kg propofol. After loss of consciousness, patients were randomly allocated to receive 0.3, 0.5, 1.0, 1.5, or 2.0 mg/kg succinylcholine or saline solution (control group). Tracheal intubation was performed 60 s later. A blinded investigator performed all laryngoscopies and graded intubating conditions. Intubating conditions were excellent in 0.0%, 43.3%, 60.0%, 63.3%, 80.0%, and 86.7% of patients after 0.0, 0.3, 0.5, 1.0, 1.5, and 2.0 mg/kg succinylcholine, respectively. The incidence of excellent intubating conditions was significantly more frequent (P < 0.001) in patients receiving succinylcholine than in the controls and in patients who received 2.0 mg/kg succinylcholine (P < 0.05) than in those who received 0.3 mg/kg succinylcholine. The calculated doses of succinylcholine (and their 95% confidence intervals) that are required to achieve excellent intubating conditions in 50% and 80% of patients at 60 s are 0.39 (0.29-0.51) mg/kg and 1.6 (1.2-2.0) mg/kg, respectively. It appears that there are no advantages to using doses of succinylcholine larger than 1.5 mg/kg.

The effect of prone position on respiratory mechanics during spinal surgery.

OBJECTIVE: To study the effect of prone position on respiratory mechanics during spine surgery. DESIGN: Prospective study. SETTING: Elective spine surgery at a university hospital. PATIENTS: 12 ASA physical I & II with no coexisting cardiorespiratory disease undergoing cervical or lumbar laminectomy under general anesthesia in prone position. MEASUREMENTS: Ten min after induction of general anesthesia and endotracheal intubation, while patients were in supine position, the following measurements were taken using anesthesia delivery unit (Datex Ohmeda type A_Elec, Promma, Sweden): peak airway pressure (Ppeak), peak plataeu pressure (Pplat), peak mean pressure (Pmean) and dynamic lung compliance (DLC). The same measurements were recorded 10 min after placing patients into prone position. At the end of surgery and 5 min after turning the patients supine and before tracheal extubation, the same measurements were again recorded. The results expressed as means +/- sd. One way ANOVA was used for analysis of differences in the data before, during prone position and after turning patients supine at the end of the procedure. For all comparisons p < 0.05 was considered significant. RESULTS: During prone position there was significant reduction in DLC and significant increase in airway pressures. CONCLUSION: We conclude that turning the patients form supine to prone position during anesthesia for spine surgery caused significant decrease of DLC and significant increase of airway pressure.

Succinylcholine dosage and apnea-induced hemoglobin desaturation in patients.

BACKGROUND: The authors examined the notion that a reduction in succinylcholine dose from 1 mg/kg to approximately 0.6 mg/kg would allow a faster recovery of spontaneous ventilation and reduction in the incidence of hemoglobin desaturation during the period of apnea in simulated complete upper airway obstruction situations. METHODS: This prospective, randomized, double-blind study involved 60 patients. After preoxygenation to an end-tidal oxygen concentration >90%, patients were anesthetized with 2 microg/kg fentanyl and 2 mg/kg propofol. After loss of consciousness, patients were randomly allocated to receive 0.56 or 1.0 mg/kg succinylcholine or saline (control group). Oxygen saturation was monitored continuously at the index finger. When the patient became apneic, the face mask was removed and the patient's airway was left unsupported. If the oxygen saturation decreased to 90%, the face mask was reapplied, and ventilation was assisted until the patient was awake. Time from injection of the study drug to the first visible spontaneous diaphragmatic movements was noted. RESULTS: Oxygen saturation decreased <90% in 45%, 65%, and 85% of patients in the control, 0.56 mg/kg, and 1.0 mg/kg succinylcholine groups, respectively (P = 0.03). Corresponding times (mean +/- SD) to spontaneous of diaphragmatic movements were 2.7 +/- 1.2, 4.8 +/- 2.5, and 4.7 +/- 1.3 min, respectively. These times were longer (P < 0.001) after either dose of succinylcholine compared with controls. CONCLUSIONS: Reduction in succinylcholine dose from 1.0 mg/kg to 0.56 mg/kg decreased the incidence of hemoglobin saturation <90% from 85% to 65% but did not shorten the time to spontaneous diaphragmatic movements. A significant fraction of patients would be at risk if there were failure to intubate and ventilate whether succinylcholine is administered or not and regardless of the dose of succinylcholine administered.

Use of dexamethasone to reduce postoperative vomiting and pain after pediatric tonsillectomy procedures.

OBJECTIVE: The purpose of this study is to determine whether a single dose of dexamethasone 0.5mg/kg administered before surgery could decrease post operative vomiting and pain and improves oral intake in the first 24-hours after pediatric tonsillectomy procedures. METHODS: It is a randomized, double blind, placebo controlled study. Sixty children age 2-12-years ASA 1 and 11 were scheduled for tonsillectomy, dexamethasone (n=29) and control group (n=31) were enrolled in the study. Dexamethasone group received 0.5mg/kg intravenous dexamethasone and control group received saline at the time of induction. The anesthetic regimen and surgical procedures were standardized for all patients. All patients were observed in post anesthesia care unit (PACU) and ward for post operative vomiting, pain, need for rescue antiemetic or analgesia and time for first oral intake for 24-hours. RESULTS: Data from 60 patients were analyzed. The overall incidence of early as well as late vomiting was significantly less in dexamethasone as compared to control group (37% versus 74% P=0.016), overall incidence of retching was 29% in control and 3.4% in dexamethasone (p=0.008). Vomiting once or more than once was significantly high in control as compared to dexamethasone group. The need for rescue antiemetic, the time to first oral intake and analgesic requirements did not show any significant difference in both groups. CONCLUSION: Dexamethasone is considered safe and there was no adverse effects associated with a single dose of dexamethasone. Although the need for rescue antiemetic, time to oral intake and analgesia requirements in both groups were not significant, however, we found that dexamethasone does have antiemetic properties as overall incidence of retching and vomiting was significantly less in dexamethasone group as compared to control group in children who underwent tonsillectomy.