A COMPARISON OF THE STRESS-RESPONSE TO LARYNGOSCOPY - THE MACINTOSH VERSUS THE MCCOY BLADE

The cardiovascular changes and catecholamine concentrations were compa red in 20 patients before and after laryngoscopy with either the Macin tosh or the McCoy laryngoscope blades. Following induction with fentan yl and thiopentone and muscle relaxation with vecuronium the vocal car ds were visualised for 10s with either the Macintosh or McCoy blade, c hosen at random. Heart rate, arterial blood pressure and plasma noradr enaline and adrenaline concentrations, were measured before, and at, l aryngoscopy, and 1, 3 and 5 min later. There was a significan t increa se in both heart rate (33%) and arterial blood pressure (27%) after la ryngoscopy using the Macintosh blade (p < 0.01). Use of the McCoy blad e did not result in any significant change in either heart rate or art erial blood pressure. There was a slight increase (p > 0.05) in plasma noradrenaline concentrations using the Macintosh blade which persiste d for 5 min after laryngoscopy. This was not observed with the McCoy b lade. There was no change in plasma adrenaline concentrations with eit her blade during the 5 min after laryngoscopy when compared to the val ues before laryngoscopy. It is concluded that the stress response to l aryngoscopy is less marked with the use of the McCoy blade and is prob ably due to a reduction in the force necessary to obtain a clear view of the larynx.