Anaesthetic management of a case of dilated cardiomyopathy for emergency appendectomy.

The anesthetic management of a patient with dilated cardiomyopathy (DCM) undergoing non-cardiac surgery poses a challenge for anesthesiologist either due to pre-existing or a risk of precipitating congestive heart failure. We report a successful use of combined spinal epidural for emergency appendicectomy in a patient of DCM. Different anesthetic concerns and agents, some recent advances are also discussed.

INTRODUCTION

Dilated cardiomyopathy (DCM) is primarily a disease characterized by the left ventricle (LV) or biventricular dilatation, systolic dysfunction, and normal LV wall thickness. DCM is defined by the presence of: (a) Fractional myocardial shortening less than 25% and/or left ventricular ejection fraction (LVEF) less than 45%; and (b) LV end diastolic diameter greater than 117% excluding any known cause of myocardial disease.[1] DCM is the most common type of non-ischemic cardiomyopathy, the third most common cause of heart failure, and the most common indication for cardiac transplantation. Though, there are some reported cases of perioperative management of patients with DCM, we present a case of DCM posted for emergency surgery.

CASE REPORT

A 43-year-old female came to the emergency room with complaints of pain abdomen, was diagnosed to have acute appendicitis and was scheduled for an emergency appendectomy. She was a known case of DCM since 1½ years. She gave a history of hospital admission 5 months ago with features suggestive of congestive heart failure. Her symptoms were well-controlled on treatment with oral frusemide, spironolactone, digoxin, ramipril and carvedilol.

On examination, her heart rate was 88/min and blood pressure of 106/66 mmHg. There were no features suggestive of congestive cardiac failure. A 12 lead electrocardiography (ECG) showed normal sinus rhythm and T-wave inversion in leads III and aVF. Chest X-ray revealed cardiomegaly. The ECG showed LVEF of 20%. Routine laboratory investigations were normal with hemoglobin level of 10.7 g%.

High-risk consent was taken from the patient and regional anesthesia technique explained.

Combined spinal-epidural anesthesia was planned. After taking patient in the operating room, pulse oximetry, ECG and non-invasive blood pressure monitors were applied. After securing intravenous line, left radial artery and right internal jugular vein cannulation was also carried out under local anesthesia.

Under all aseptic precautions, a combined spinal epidural block was given. Sub arachnoid block with 7.5 mg of 0.5% bupivacaine heavy along with 25 μg fentanyl and 0.3 mg of morphine attained a sensory level of T5. It was associated with hypotension with blood pressure of 76/40 mmHg, which was managed with intermittent intravenous boluses of 3 mg ephedrine. Surgery lasted 45 min. Central Venous Pressure (CVP) ranged from 7 to 9 cm H2O.

Her post-operative course in high dependency unit for 1 day and further in ward till discharge was uneventful.

DISCUSSION

In patients with DCM, left and/or right ventricular systolic pump function is impaired, leading to progressive cardiac enlargement, a process called remodeling, and often, but not invariably, producing symptoms of congestive heart failure. Although no cause is apparent in many cases, DCM is probably the end result of myocardial damage produced by a variety of toxic, metabolic or infectious agents. Mural thrombi may be present, particularly in the LV apex.

Perioperative issues in such patients include precipitation of congestive heart failure, arrhythmias and systemic embolism from pre-existing mural thrombi, last two being absent in our patient.

The poor predictors in this patient were an ejection fraction of less than 20% on echocardiography, LV end diastolic dilation and hypokinetic LV. High-risk consent was taken due to above reasons. Other poor prognostic factor associated with DCM is non-sustained ventricular tachycardia.[2]

Anesthetic management goals in such patients consist of maintaining normovolemia, prevention of increase in afterload and avoidance of drug induced myocardial depression. Invasive blood pressure monitoring was carried out in the above case for early detection and treatment of hypotension. Central venous pressure monitoring helped in optimizing fluid therapy. Transesophageal echocardiography, continuous cardiac output monitoring,[3] bispectral index[4] and pulmonary artery catheterization are some of the other modalities of monitoring, that have been found useful in patients with DCM.

Neuraxial blockade and various pharmacological agents such as dobutamine, amrinone, milrinone, and levosimendan[5] have been used in patients with DCM successfully to reduce afterload.

A combined Spinal Epidural Block was planned in our patient because along with reducing the afterload, it provides predictable and good post-operative analgesia.[6] A low dose of local anesthetic along with fentanyl was used in subarachnoid block to prevent sudden fall in blood pressure. Morphine 0.3 mg (5 μg/kg body weight) was also given in spinal block to prolong post-operative analgesia. Epidural catheter was also placed to provide anesthesia if spinal failed or to increase the level or duration of block, if required. Ephedrine helped in treating subarachnoid block related hypotension, by restoring peripheral resistance.

Among the IV induction agents, etomidate is preferred as it causes least cardiovascular depression. Ketamine, by its sympathetic stimulation action, increases afterload, thus avoided, but can be used along with midazolam, propofol[7] and/or opioids like fentanyl in patients with severe myocardial dysfunction. Propofol in clinically used concentrations decreases sympathetic tone and reduces systemic vascular resistance, which is beneficial. Propofol also has some direct negative inotropic effect on heart but studies have shown that net effect on myocardial contractility is insignificant in clinically used concentrations.[8] Opioids cause little or no cardiovascular depression and decrease the dose of general anesthetics for both induction as well as maintenance. All of the potent volatile anesthetic agents are myocardial depressants, and for this reason, high concentration of these agents is best avoided. Low doses are usually well-tolerated; however, recently, much interest has been generated regarding use of xenon in patients with DCM, because of its minimal effect on heart rate, arterial and LV pressures, myocardial contractility, and regional chamber stiffness.[910]

Anesthetic management of patients with DCM poses a challenge for the anesthesiologist, but meticulous planning, appropriate monitoring, judicious use of pharmacological agents and tailor made anesthetic technique according to patient's general condition and surgical requirement can lead to a favorable outcome.