Isosorbide dinitrate spray. Attenuation of cardiovascular responses to laryngoscopy and intubation

A comparison of the stress response to laryngoscopy. The Macintosh versus the McCoy blade

The cardiovascular changes and catecholamine concentrations were compared in 20 patients before and after laryngoscopy with either the Macintosh or the McCoy laryngoscope blades. Following induction with fentanyl and thiopentone and muscle relaxation with vecuronium the vocal cords were visualised for 10 s with either the Macintosh or McCoy blade, chosen at random. Heart rate, arterial blood pressure and plasma noradrenaline and adrenaline concentrations were measured before, and at, laryngoscopy, and 1, 3 and 5 min later. There was a significant increase in both heart rate (33%) and arterial blood pressure (27%) after laryngoscopy using the Macintosh blade (p < 0.01). Use of the McCoy blade did not result in any significant change in either heart rate or arterial blood pressure. There was a slight increase (p > 0.05) in plasma noradrenaline concentrations using the Macintosh blade which persisted for 5 min after laryngoscopy. This was not observed with the McCoy blade. There was no change in plasma adrenaline concentrations with either blade during the 5 min after laryngoscopy when compared to the values before laryngoscopy. It is concluded that the stress response to laryngoscopy is less marked with the use of the McCoy blade and is probably due to a reduction in the force necessary to obtain a clear view of the larynx.

Laryngeal oedema after isosorbide dinitrate spray and sublingual nifedipine

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The efficacy of guanfacine in reducing perioperative hemodynamic changes and volatile anesthetic requirement

STUDY OBJECTIVE

To evaluate the efficacy of guanfacine, an alpha 2-adrenergic agonist, for attenuating hemodynamic changes associated with tracheal intubation or extubation, providing intraoperative hemodynamic stability, and reducing inhalation anesthetic requirement in patients undergoing gynecologic surgery.

DESIGN

Randomized, double-blind, placebo-controlled study.

SETTING

Inpatient gynecology at a university hospital.

PATIENTS

45 women (ASA I) undergoing elective abdominal hysterectomy.

INTERVENTIONS

Guanfacine and placebo supplementation. Oral guanfacine at 0.5 or 1 mg or a placebo (control) 3 hours before induction of anesthesia. Anesthesia was induced with thiamylal 5 mg/kg and vecuronium 0.2 mg/kg, and maintained with isoflurane and 50% nitrous oxide (N2O) in oxygen. The inspired isoflurane concentration was maintained at 1% during the first 5 minutes following induction of anesthesia and titrated to the concentration required to maintain hemodynamic stability [defined as +/- 10% of systolic blood pressure (SBP)]. The end-tidal concentration of isoflurane was monitored throughout anesthesia. On completion of surgery, N2O and isoflurane were discontinued. Following confirmation of recovery from anesthesia and muscle relaxation, the endotracheal tube was removed.

MEASUREMENTS AND MAIN RESULTS

Patients in the control group showed significant increases in SBP and diastolic blood pressure (DBP) and heart rate (HR) associated with tracheal intubation 50 +/- 5, 57 +/- 6.3, and 45 +/- 4.6 (%, mean +/- SEM, p < 0.05 for any variables), respectively. Plasma norepinephrine and epinephrine concentrations increased to 382 +/- 40 pg/ml and 49 +/- 4.2 pg/ml, respectively (p < 0.05 compared with basal values). These changes were attenuated in patients receiving 1 mg of guanfacine (29 +/- 4.2, 33 +/- 4.5, 25 +/- 3.2, 210 +/- 32, and 22 +/- 3.5, respectively (p < 0.05 for any variables compared with placebo group). Higher inspired concentrations of isoflurane (%) were required in the control and 0.5 mg guanfacine-treated groups (1.2 +/- 0.05 and 1.0 +/- 0.04, respectively) than in the 1 mg guanfacine-treated group (0.62 +/- 0.03) for hemodynamic stability (p < 0.05). Coefficient of variation in HR changes during surgery was 17.2, 13.9, and 8.8 in the placebo, guanfacine 0.5 mg, and guanfacine 1 mg treated groups, respectively. Compared with placebo, guanfacine 1 mg reduced the maximum changes (mean +/- SEM) in SBP (7 +/- 1.2 vs. 18 +/- 2.2) and in HR (23 +/- 2.1 vs. 44 +/- 3.6) occurring during tracheal extubation. The incidence of perioperative complications was similar among the three groups.

CONCLUSION

Guanfacine 1 mg administered orally proved to be an effective premedicant for providing intraoperative hemodynamic stability, attenuating the increase in BP and HR associated with tracheal intubation and extubation, and reducing anesthetic requirements without increasing the incidence of perioperative complications.