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Correspondence |
Valencia, Spain
To the Editor:
We wish to comment on the letter by Maruyama et al.1 recently published in the Canadian Journal of Anesthesia. We agree with the pathophysiologic explanation put forward by the authors regarding the imbalance between sympathetic and parasympathetic tone as the cause of the cardiac block observed. We have recently described a series of cases in which nodal rhythm (probably a vagal-mediated anomalous cardiac response similar to sinus arrest) developed in patients with spinal block who were treated with atropine.2 The sympathetic blockade that occurs during spinal anesthesia is not the same than during general anesthesia, but a common explanation is possible. Vasodilatation is a general response during both types of anesthesia. In some instances the heart beats without sufficient preload and can develop a paradoxical, predominantly vagal, response consisting of bradycardia or other vagal responses (such as sinus arrest, nodal rhythm, or cardiac arrest).3 In this context, atropine may worsen or potentiate the cardiac response. If our perception is correct, then a sympathomimetic drug (such as epinephrine, as was the choice of the authors, or low-dose ephedrine, the drug used to treat our patients) would be the drug of choice in these cases to increase preload by producing vasoconstriction. In addition ephedrine increases heart rate. This approach has been supported by several authors.2,4 Atropine can be a drug of second choice, or perhaps should be administered together with a sympathomimetic drug.
References
1 Maruyama K, Mochizuki N, Hara K. High-degree atrioventricular block after the administration of atropine for sinus arrest during anesthesia (Letter). Can J Anesth 2003; 50: 528–9.
2 Errando CL. Nodal rhythm after administration of atropine to bradycardic patients under subarachnoid anesthesia. Four cases and a review of pathophysiology and treatment (Spanish). Rev Esp Anestesiol Reanim 2001; 48: 384–6.[Medline]
3 Pollard JB. Cardiac arrest during spinal anesthesia: common mechanisms and strategies for prevention. Anesth Analg 2001; 92: 252–6.
4 Auroy Y, Bargue L, Benhamou D, et al. Recommandation of the SOS ALR Group on the use of locoregional anesthesia (French). Ann Fr Anesth Réanim 2000; 19: 621–3.[Medline]
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