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J Thorac Cardiovasc Surg 2004;127:592-593
© 2004 The American Association for Thoracic Surgery
Brief communication |
a Department of Cardiovascular Anesthesia, Vita-Salute University of Milan, IRCCS San Raffaele Hospital, Milan, Italy
Received for publication June 16, 2003; accepted for publication September 12, 2003.
* Address for reprints: Donatella Sparicio, MD, Via Olgettina 60, 20132 Milano, Italy
Sparicio.donatella{at}hsr.it
Off-pump surgery is gaining popularity for coronary artery bypass grafting (CABG). We report the perioperative management of 2 patients who self-assumed lithium and had refractory hypotension during beating heart surgery. Both patients had a dramatic hemodynamic improvement after receiving methylene blue.
Clinical summary
Two men (57 and 68 years, each weighing 72 kg, height 180 and 186 cm) with coronary artery disease and ejection fraction greater than 50% were scheduled for elective off-pump CABG. Medical history included depression on treatment with benzodiazepines and lithium carbonate (300 mg every 8 hours). They were both on treatment with beta-blockers (atenolol and carvedilol), calcium antagonist (amlodipine), nitrates, and aspirin; patient A also used an angiotensin-converting enzyme inhibitor. Both patients had an unnoticed self-administration of lithium the morning before surgery.
Standard premedication and anesthesia were administered. Target coronary vessels were mechanically stabilized and posterior vessel presentation obtained with a suspension stitch placed in the middle of the 4 pulmonary veins. Both patients received an in situ internal thoracic artery graft to the left anterior descending artery and a saphenous vein graft to the posterior descending and obtuse marginal arteries. Hypotension ensued after pericardial opening and anastomosis. Arterial blood pressure, 80/50 mm Hg (mean arterial pressure = 60 mm Hg), was not responsive to etilephrine boluses, atrial pacing, dopamine infusion (10 µg/kg/min), steep Trendelenburg position, fluid loading, and opening of both pleura; nevertheless, patients' stability, in the absence of arrhythmias or ST-T changes, maintenance of diuresis, and an optimal cooperation between anesthesiologist and surgeon, permitted concluding the procedure without converting to cardiopulmonary bypass. Intraoperative transesophageal echocardiography demonstrated normal biventricular function without new segmental acinesia. In the hypothesis of vasoplegia both patients received methylene blue (1.5 mg/kg intravenously) in 20 minutes with a rapid improvement of mean arterial pressure (80 mm Hg).
At the end of the operation, the patients were transferred to the intensive care unit and had an uneventful postoperative course.
Discussion
Lithium (Li+), the primary drug used for the treatment of bipolar (maniac-depressive) disorders, may induce prolonged sleep time after barbiturate anesthesia, enhanced neuromuscular blockade after muscle relaxant administration, and cardiac conduction abnormalities.1 The mechanism of action of Li+ as a mood-stabilizing agent remains unknown. Therapeutic doses of lithium interfere with the metabolism of cathecolamines that are involved in the pathophysiology of the troubles of humor; Li+ also inhibits the liberation of norepinephrine and dopamine from the nervous terminations, strengthens the liberation of serotonin, and increases the presynaptic reuptake and storage of catecholamines. Furthermore, it has interactions with drugs like angiotensin-converting enzyme inhibitors (which reduce Li+ clearance with possible Li+ toxicity) and beta-blockers (which enhance the central depression induced by lithium).
In light of these pharmacodynamic properties, in these patients we suspected that chronic lithium therapy played a role in the unresponsiveness to vasoconstrictor agents. Lithium should be discontinued before surgery, at least the day of the operation, especially when high blood pressures are requested during surgery.2
Methylene blue inhibits the enzyme guanylate cyclase, avoiding the cyclic guanosine 3'5'-monophosphate-dependent vasorelaxant effects of nitric oxide in the smooth muscle of vessels. It has been used as an unconventional drug to treat refractory vasoplegia after cardiopulmonary bypass, anaphylaxis, and septic shock.3-5
We especially appreciated its use in these patients because the alternative drug (norepineprine), in the postoperative period of cardiac surgery, could be detrimental, especially after CABG. No data exist on the effects of methylene blue on arterial conduits.
Conclusion
We recommend lithium to be discontinued before surgery and suggest methylene blue as an alternative drug to treat vasodilatory shock in the perioperative period of cardiac surgery.
Acknowledgments
We are in debt to Gherbi Giordano, RN, for the care provided to these patients.
References
receptor agonists complicating cardiopulmonary bypass: lithium as a potential cause. Anesth Analg. 1996;82:1082–1085This article has been cited by other articles:
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  E. G. Leite, A. Ronald, A. J. Rodrigues, and P. R. B. Evora Is methylene blue of benefit in treating adult patients who develop catecholamine-resistant vasoplegic syndrome during cardiac surgery? Interact CardioVasc Thorac Surg, December 1, 2006; 5(6): 774 - 778. [Abstract] [Full Text] [PDF]
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 K. Taylor Reply to the Editor J. Thorac. Cardiovasc. Surg., January 1, 2006; 131(1): 251 - 251. [Full Text] [PDF]
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 G. Shanmugam Vasoplegic syndrome--the role of methylene blue Eur J Cardiothorac Surg, November 1, 2005; 28(5): 705 - 710. [Abstract] [Full Text] [PDF]
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K. Taylor and H. Holtby Methylene blue revisited: Management of hypotension in a pediatric patient with bacterial endocarditis J. Thorac. Cardiovasc. Surg., August 1, 2005; 130(2): 566 - 566. [Full Text] [PDF]
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