Hensley's Practical Approach to Cardiothoracic Anesthesia


III. Cardiac Anesthesia

available to stabilize the hemodynamics by slowing the heart rate down after the isoproterenol test is completed. Baseline and stimulated gradient measurements are repeated after cardio pulmonary bypass discontinuation to assess a relief of obstruction. Cardiopulmonary bypass should be resumed to remove additional septal muscle if the maximal residual LVOT gradient exceeds 25-30 mm Hg. D. Early Postoperative Care The majority of patients with HCM are eligible for fast-track recovery. For postoperative pain control, bilateral pecto-intercostal facial plane blocks can be performed after chest closure utilizing 0.25% bupivacaine 0.5-1 mL/kg. Patients with uncomplicated intraoperative courses are usually extubated within 2-4 hours after intensive care unit (ICU) admission. Patients with no significant comorbidities and smooth intraoperative course can be extubated in the operat ing room. IV. Surgical Subgroups and Anesthetic Considerations A. Apical Myectomy In a subset of patients with HCM, hypertrophy is primarily localized at the apex of the LV. These patients can have progressive, drug-refractory diastolic heart failure with limiting symp toms related to low cardiac output, even absent left ventricular obstruction. Previously heart transplantation was the only surgical therapy available for such patients. Apical myectomy to enlarge the LV cavity and improve diastolic dysfunction is now one of the therapeutic options for symptomatic patients with HCM. 24 The ventricle is opened at the apex, and excessive muscle is excised during this procedure. In contrast to patients having transaortic septal myectomy for subaortic obstruction, patients with apical HCM undergoing ventricular enlargement by api cal myectomy usually require low-dose inotropic support (epinephrine 0.03 μg/kg/min) during discontinuation of cardiopulmonary bypass. Unlike patients with cardiomyopathy due to sys tolic dysfunction who are managed with afterload reduction, patients with apical HCM require normal or slightly higher than normal peripheral resistance both before and after the operation. CLINICAL PEARL Patients undergoing apical myectomy might require inotropic support after cardiopulmonary bypass because of ventriculotomy. B. Pulmonary Hypertension Some degree of pulmonary hypertension is present in ∼ 50% of patients undergoing septal my ectomy, and almost 15% have moderate-to-severe pulmonary hypertension (systolic pulmo nary artery pressure ≥ 50 mm Hg). Preoperative pulmonary hypertension is independently associated with late mortality following septal myectomy. 25 Intraoperatively, pulmonary pres sure is monitored with pulmonary artery catheter, and elevated pulmonary artery pressure is expected to improve following relief of LVOT obstruction; post-bypass use of pulmonary inodilator milrinone or inhaled nitric oxide is uncommon. C. Hypertrophic Cardiomyopathy in Children HCM is a common genetic disorder in adults; it is often well tolerated in pediatric popula tions, which may reduce the rates of pediatric diagnosis. 26 Similar to adult patients, presen tation in early childhood is usually associated with dynamic LVOT obstruction and various degrees of MR related to SAM. Children often appear less symptomatic than adults, possibly because their activities are self-limited. However, the progression of LV hypertrophy may be more rapid in children than in adults. Further, the reported incidence of sudden cardiac death in children with HCM may be as high as 6% compared to 1%-3% in adults. Surgical my ectomy should be considered for symptomatic children when the resting or provoked LVOT gradient is > 50 mm Hg. Surgery may also be advised in children who are asymptomatic or mildly symptomatic with high gradients of between 75 and 100 mm Hg at rest or when there is severe concomitant MR.


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