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How would you anesthetize this patient?
The avoidance of myocardial depression still remains the goal of anesthetic management for patients with dilated cardiomyopathy. All the potent volatile anesthetic agents are myocardial depressants. For this reason, these agents, especially in high concentrations, are probably best avoided in this group of patients. An anesthetic based on a combination of narcotics and sedative-hypnotics (with or without nitrous oxide) can be employed instead. Etomidate and ketamine are acceptable anesthetic induction agents, while thiopental and propofol are relatively contraindicated.
For the patient with a severely compromised myo-cardium, the synthetic piperidine opioids (fentanyl, sufen-tanil, remifentanil, and alfentanil) are useful, since myocardial contractility is not depressed. Chest wall rigidity associated with these medications is treated with muscle relaxants. Bradycardia associated with high-dose opioid anesthesia may be prevented by the use of pancuronium for muscle relaxation, anticholinergic drugs, or pacing. For peripheral or lower abdominal surgical procedures, the use of a regional anesthetic technique is a reasonable alternative, provided filling pressures are carefully controlled and the hemodynamic effects of the anesthetic are adequately monitored. Regional techniques may not be possible in many patients due to anticoagulation for associated atrial fibrillation or mural thrombus prevention.
In planning the anesthetic management of the patient with dilated cardiomyopathy, associated cardiovascular conditions, such as the presence of CAD, valvular abnormal-ities, outflow tract obstruction, and constrictive pericarditis, should also be considered. Patients with CHF often require circulatory support intra- and postoperatively. Inotropic drugs, such as dopamine or dobutamine, have been shown to be effective in low-output states, and produce modest changes in systemic vascular resistance at lower dosages. In severe failure, more potent drugs, such as epinephrine, may be required. The effects of β-adrenergic agents are limited, however, by the downregulation of β-adrenergic receptors that occurs in chronic CHF. Milrinone is a phosphodiesterase inhibitor with inotropic and vasodilator properties that may improve hemodynamic performance. As noted above, stroke volume is inversely related to afterload in the failing ventricle, and reducing left ventricular afterload with vasodilating drugs, such as nitroprusside and milrinone, is also effective in increasing cardiac output. In patients with myocarditis, especially of the viral variety, transvenous or external pacing may be required should heart block occur. Intra-aortic balloon counterpulsation and left ventricular assist devices are further options to be considered in the case of the severely compromised ventricle.
There is a definite increase in the incidence of supra-ventricular and ventricular dysrhythmias in myocarditis and the dilated cardiomyopathies. These dysrhythmias often require extensive electrophysiologic investigation, and may be unresponsive to maximal medical therapy.
Etomidate or ketamine
Opioids: fentanyl, sufentanil, alfentanil
+/– Nitrous oxide
Electrocardiogram for dysrhythmias Arterial line
Pulmonary artery catheter Transesophageal echocardiography
Implantable cardioverter-defibrillators are often implanted in these patients, and must be turned off during surgery requiring electrocautery. Thus, proper ECG monitoring and access to a charged external cardioversion device are crucial in the management of these patients. Amiodarone is a long-acting antidysrhythmic medication with intrinsic myocardial depressant properties. Nevertheless, amio-darone seems to have an overall beneficial effect in patients with CHF, especially those who present with chronic atrial fibrillation. Furthermore, amiodarone is currently the antiarrhythmic medication of choice in persistent ventricu-lar tachycardia/ventricular fibrillation, which may be encountered at any time in patients with severely impaired myocardial function (Table 4.1)
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