900 Correspondence Intubating conditions and correct application of cricoid pressure during rapid sequence induction: who should hold the mask ? To the Editor: In difficult elective intubations, cricoid pressure (CP) is often applied after laryngoscope-assisted head extension and jaw thrust to improve visualization. In contrast, during rapid sequence induction (RSI), CP is applied as the drugs are injected. The head can flex forward as consciousness is lost and make it difficult for the assis- tant to know where to apply CP. If CP is then applied the resulting skin tension can act like a "bow string" to prevent flail extension of the head and forward displace- ment of the mandible. Difficulty in inserting the laryn- goscope into the mouth during PSI for Caesarean section has been attributed to large breasts getting in the way of the laryngoscope handle. Another explana- tion, "fixed" flexion of the head due to the "bow string" effect deserves consideration. If the anaesthetist holds the mask and maintains head extension with a jaw thrust as CP is applied, the "bow string" effect is prevented. An intravenous stop cock assembly allows injection with one hand while the other holds the mask and head position. When the anatomy is not obvious, the inferior aspect of the thyroid cartilage can be felt with the fingers of the right hand and the assistant instructed to apply CP from below. Since the jaw thrust prevents the tongue from obstructing the air- way, an extra period of apnoeic oxygenation is possible while waiting for the muscle relaxant to take effect. Gerard Bruin MD FRCPC, Norm Buckley MD FKCPC Hamilton Health Sciences Corporation Department of Anaesthesia/McMaster Campus 1200 Min Street West, Room 2U3 Hamilton, Ontario, L8N 3Z5 Pharmacological properties of the denervated heart To the Editor: We read with interest Dr. Haddow's thoughtful review article concerning the management of anaesthesia for patients having undergone lung transplantation) As indicated in his article, one of the considerations for this type of patient is the potential for disruption of the nerves innervating the heart. Dr. Haddow asserts that in the event of such cardiac denervation, heart rate will not change in response to the administration of anti- cholinesterase drugs. We wish to challenge this opinion which, although widely held, has little evidence to sup- port it. On the contrary, we have demonstrated that neostigmine consistently produces a dose-dependent, atropine-sensitive reduction in heart rate in cardiac transplant patients, and in particular patients transplant- ed remotely prior to the administration of neostigmine (> six months) may be especially sensitive to its brady- cardic effect.2 We have recently shown that edrophoni- um also evokes a dose-dependent, atropine-sensitive reduction in heart rate in the cardiac transplant patient, although the magnitude of the bradycardia is smaller and less variable compared to that produced by neostig- mine. s Animal studies suggest that anticholinesterases may produce a bradycardic response in the denervated heart by their direct stimulation ofcholinergic receptors in the peripheral cardiac parasympathetic pathway, or by their anticholinesterase action, whereby acetylcholine tonically released from cardiac parasympathetic post- ganglionic cells is protected from hydrolysis by acetyl- cholinesterase. 4 These findings have prompted us to caution that when administering anticholinesterase drugs to heart transplant patients, a muscarinic antago- nist should always be co-administered to block the car- diac and other muscarinic side effects,s While it remains to be demonstrated that anticholinesterase drugs evoke a bradycardic response in a heart denervated during the course of lung transplantation, such an effect is antici- pated in light of the observations in the cardiac trans- plant patients and animal studies cited above. S.B. Backman MDCM PhD FRCPC G.S. Fox MD FRCPC F.E. Ralley MB CHB Department of Anaesthesia Royal Victoria Hospital McGill University Montreal, Quebec REFERENCES 1 Haddow GR. Anaesthesia for patients after lung trans- plantation. Can J Anaesth 1997; 44: 182-97. 2 Backman SB, Fox GS, Stein RD, Ralley FE. Neostigmine decreases heart rate in heart transplant patients. Can J Anaesth 1996; 43: 373-8. CAN J ANAESTH 1997 / 44:8 / pp 900-902