Anaesthetic Management for a Dilated Cardiomyopathy Patient,Scheduled for Lumbar Spine Surgery

Abstract

Background:

Dilated cardiomyopathy (DCM) is characterized by dilatation and impaired contraction of left or both ventricles. Diagnostic criteria are left ventricular ejection fraction less than 40% or fractional shortening less than 25%. Perioperative anesthetic management of these patients are very challenging for anesthesiologists and intensive care team.

Case presentation:

A 55-year-old female, presented with complaints of severe low-back ache with bilateral lower limb involvement without involvement of bladder and bowel. Severe cord compression at the L4-5 level and severe lumbar canal stenosis were detected by magnetic resonance imaging. Echocardiography showed that the left ventricle (LV) had global hypokinesia, with an ejection fraction of 25% to 30%. The planed surgical procedures were L4 lumbar laminectomy and L4-5 microdiscectomy.

Conclusion:

Continuous monitoring and control of hemodynamic parameters as well as central venous pressure guided fluid therapy is the cornerstone in improving outcome in patients with dilated cardiomyopathy for non-cardiac surgery.

Introduction

Dilated cardiomyopathy (DCM) is characterised by left ventricular or biventricular enlargement and impairment of systolic function. Patients with compromised left ventricle (LV) dysfunction pose a conundrum for anaesthesiologists, who must safeguard a stable cardiovascular status and curtail the morbidity and mortality of the patients.^[1-3] Before the final surgical procedures, cardiac risk factors are usually managed in order to prepare for elective surgeries.^[4] We delineate the anaesthetic plan of a diagnosed hypothyroid patient with severe left ventricle dysfunction who underwent lumbar spine surgery.

Case Report

A 55-year-old female, weighing 56 kg, presented with complaints of severe low-back ache with bilateral lower limb involvement but no involvement of bladder and bowel. She had a documented case of hypothyroidism managed with tablet Thyroxine 125 mcg daily. Neurological examination revealed a sensory deficit in both the lower limbs with a grade 3/5 motor power deficit. Magnetic resonance imaging revealed severe lumbar canal stenosis and severe cord compression at the L4–5 level. All routine blood tests were in the normal range. Preoperative electrocardiography (ECG) revealed sinus tachycardia with intraventricular conduction delay, and echocardiography revealed the global hypokinesia of LV, with ejection fraction being 25%–30% and no thrombi present. Preoperative counselling was done, and the risk associated with the anaesthesia was explained.

The cardiologist recommended that the patient be premedicated with oral alprazolam 0.25 mg and oral dytor 10 mg the night before and two hours prior to surgery. Dobutamine 2 mcg/kg/min intravenous infusion was started two hours prior to surgery to decrease afterload. Standard monitoring was attached to the patient in the operating room, which included noninvasive blood pressure, pulse oximetry and ECG. Under local anaesthesia, peripheral right forearm venous line, left radial arterial and right internal jugular vein cannulation procedures were carried out. Her basal heart rate was 110/min, arterial blood pressure was 126/86 mmHg and central venous pressure (CVP) was 6 mmHg. External cardiac pacemaker pads were attached prior to surgery to handle any emergencies. The following injections were used to induce anaesthesia: 0.2 mg of glycopyrrolate, 0.03 mg/kg of midazolam, 1.5 mcg/kg of fentanyl and a titrated dose of etomidate. Tracheal intubation with 7.5 mm endotracheal tube was done with vecuronium 0.1 mg/kg body weight. Maintenance of anaesthesia was done with O₂: air (40:60), sevoflurane (0.25%), propofol (50–100 mcg/kg/min) and intermittent boluses of vecuronium and fentanyl. Ventilation was adjusted to maintain an EtCO₂ value between 35 and 40 mmHg. Temperature was maintained at around 36°C. Spinal decompression lasted three hours. In the perioperative period, the heart rate was maintained in the range 80–100/min, mean arterial pressure was maintained in the range 70–85 mmHg with intermittent noradrenaline support (0.01–0.05 mcg/kg/min), CVP was maintained at 4–8 mmHg and total 1,000 mL of normal saline was given. The total blood loss was 50 mL, and the urine output was 300 mL. The patient was given a shot of ondansetron (4 mg) prior to extubation. The endotracheal tube was removed after accomplishment of surgery, and the patient was shifted to the postanaesthesia care unit. After surgery, her haemodynamic parameters remained stable. Following surgery, analgesia was maintained with fentanyl infusion 30 mcg/hour and paracetamol 1 g i.v. eight hourly.

Discussion

Patients with compromised LV function and global hypokinesia are at risk of perioperative forward heart failure. Myocardial ischemia occurs more often and is more severe during the first 24–72 hours after surgery. Myocardial infarction (MI) and perioperative fatal arrhythmias are the main causes of morbidity and mortality in these patients.^[5] The postoperative stress caused by anaesthesia, surgical complications and early postoperative movement are likely related to this. Furthermore, the majority of spine surgeries are performed in the prone position, which has a significant impact on cardiovascular function, including a reduction in cardiac output (CO). In the prone position, abdominal compression aggravates the obstruction of the inferior vena cava, resulting in reduced cardiac output, venous stasis, increased bleeding and thrombotic consequences.^[6] Careful positioning of patients can reduce these risks.

The aim of anaesthesia is to keep the blood pressure and heart rate stable, prevent irregular heart rate and ensure enough blood volume and minimal myocardial depression.^[7] It is recommended to avoid drugs that cause myocardial depression, tachycardia and a decrease in systemic vascular resistance.^[8]

We used fentanyl, etomidate and vecuronium bromide for induction and intubation because of the least myocardial depressant property. Since invasive blood pressure monitoring measures blood pressure beat to beat, it is crucial for identifying changes in blood pressure quickly and adapting treatment accordingly in cardiac compromised patients. Central venous pressure monitoring has also been shown to optimise fluid management. Other monitoring methods that have been reported to be helpful in patients with dilated cardiac myopathy include pulmonary artery catheterisation, bispectral index, transoesophageal echocardiography and continuous cardiac output monitoring.^[9] We avoid N₂O during maintenance of anaesthesia because N₂O reduces CO in patients with compromised LV function and may cause hypotension and LV failure in patients with severe preexisting LV dysfunction.^[10] It has been shown that turning the patient prone results in a decrease in cardiac index and an increase in systemic vascular resistance, particularly during propofol intravenous anaesthesia compared to inhalational anaesthesia with sevoflurane.^[11] Post-operative pain is also a problem for cardiac compromised patients, because it may produce postoperative hypertension, arrhythmias or heart failure, which commonly occur in the first 24 hours after surgery.

Finally, we would like to emphasise the significance of communicating with patients and their relatives before the surgery and discussing the possible risks and benefits. Anaesthesiologists face difficulties when managing the anaesthesia of patients with dilated cardiomyopathy; however, successful outcomes can be achieved with careful planning, appropriate monitoring, prudent use of pharmaceutical drugs and a customised anaesthetic technique based on the patients’ surgical need and general condition.