Use of combined spinal epidural technique with milrinone nebulization in a patient with pulmonary stenosis posted for elective cesarean section - A case report -

Abstract

Background

Anesthetic management in pregnant women with congenital heart disease is complex due to physiological changes during pregnancy and the specific hemodynamic challenges posed by different cardiac anomalies. A multidisciplinary approach is essential to optimize maternal and fetal outcomes. Pregnancy induces significant cardiovascular changes to meet the increased metabolic demands of the mother and growing fetus. Cardiovascular changes may aggravate the underlying pathology during pregnancy, leading to hemodynamic instability.

Case

A 27-year-old pregnant female presented with severe pulmonary stenosis after pulmonary valve balloon dilatation for an elective cesarean section using a combined spinal-epidural technique (CSE) and milrinone nebulization to avoid right ventricular dysfunction.

Conclusions

CSE reduces the stress response to surgery, minimizes myocardial depression associated with anesthetic drugs, and improves postoperative pain control. Techniques such as milrinone nebulization may help lessen the hemodynamic perturbations associated with auto-transfusion post-delivery.

Congenital heart disease (CHD) refers to structural problems of the heart present at birth. The prevalence of CHD in pregnant women is growing significantly due to advances in obstetrics, neonatology, cardiology, and anesthesia care [1]. The clinical features of pulmonary stenosis depend on its severity and the transvalvular gradient [2]. Cardiovascular changes during pregnancy can complicate the course with exacerbation of symptoms and increased stress on an already hypertrophied right ventricle [3]. Here, we describe the case of a 27-year-old primigravida with pulmonary stenosis after pulmonary valve balloon dilatation at 22 weeks of gestation, who underwent elective lower segment cesarean section (LSCS) at 32 weeks of gestation under a combined spinal epidural anesthetic technique. Obtained the written consent from the patient of this case report.

CASE REPORT

A 27-year-old primigravida at 10 weeks of gestation presented to the emergency department with complaints of dyspnea (New York Heart Association [NYHA] class III) and occasional chest pain, unaware of an underlying heart disease in the preconception period. Transthoracic echocardiography (TTE) revealed pulmonary stenosis at the valvular level with a peak velocity of 6.9 m/s, peak gradient of 190 mmHg, and mean gradient of 100 mmHg. The right ventricle was dilated and hypertrophied, with a D-shaped left ventricular cavity and left ventricular ejection fraction of 60%. Based on these findings, the patient was classified under the World Health Organization (WHO) pregnancy risk category III. No congenital anomalies were observed.

At 22 weeks’ gestation, a multidisciplinary team performed pulmonary valve balloon dilatation under local anesthesia. Post-procedural TTE showed a velocity of 3.98 m/s across the pulmonary valve with a reduced peak gradient of 64 mmHg. Mild tricuspid regurgitation (TR) was observed with a TR gradient of 44 mmHg.

Due to fetal growth retardation and a reduced amniotic fluid index, elective LSCS was planned at 32 weeks of gestation. The patient’s clinical condition improved significantly over 10 weeks following pulmonary valve balloon dilatation, with NYHA classification improving from III to I (with no limitation in performing daily activities and a 6-min walk test of more than 400 m without a drop in oxygen saturation). Biochemical parameters were within normal limits except for a hemoglobin level of 11.4 g/dl. The airway examination results were unremarkable, and a spinal examination revealed mild left-sided scoliosis. The patient was deemed fit for the procedure according to the American Society of Anesthesiologists physical status classification IV. Preoperative orders included continuing the metoprolol tablet 25 mg for heart rate control and aspiration prophylaxis with intravenous injection of pantoprazole 40 mg.

In the preoperative area, two 16G intravenous cannulas were secured in the right hand, and an arterial cannula was placed in the left radial artery. Combined spinal-epidural technique (CSE) was administered. A eutectic mixture of local anesthetic cream was applied to the lumbar area 30 min before the procedure. Under standard American Society of Anesthesiologists monitoring, the epidural needle was inserted at the L1–L2 level, with loss of resistance identified at a 3.5-cm depth, and the catheter was fixed 8 cm from the skin. After epidural catheter insertion, 1.2 ml of 0.5% bupivacaine heavy was administered at the L3–L4 level using a 25G Quincke needle. Initial spinal anesthesia produced a sensory block up to the T10 dermatome. To extend the block to the T6 level, two 4-ml aliquots of 0.5% bupivacaine were administered 10 min apart.

Following induction, nebulized milrinone (informed consent for the use of the drug was obtained) at 80 mcg/kg (4 mg) for 5 min was administered to promote pulmonary vasodilation, increase right ventricle inotropy, and promote the forward flow across the stenotic valve to compensate for the increased preload as a result of auto-transfusion post-delivery [4]. Repeat doses were not administered. Oxygen was provided via a face mask at 6 L/min until completion of surgery. A live female infant weighing 1.8 kg was successfully delivered. Obtained the written consent from the patient of this case report.

Intraoperatively, 300 ml of Ringer’s lactate was administered, considering that auto transfusion would additionally increase the right ventricle preload, resulting in strain on the right ventricle. Fifteen units of oxytocin were infused over 30 min. The estimated blood loss was approximately 500–600 ml while the urine output was 120 ml. The patient remained hemodynamically stable throughout the procedure, maintaining a mean arterial pressure > 70 mmHg (Table 1).

Table 1.

Hemodynamic Parameter and Oxygen Saturation During Perioperative Period

Parameter	Pre-induction	Post-induction	Post-nebulization	At the time of delivery	Post-surgery
Heart rate (bpm)	92	87	90	97	96
Systolic blood pressure (mmHg)	121	116	115	126	118
Diastolic blood pressure (mmHg)	76	72	72	79	71
Mean arterial pressure (mmHg)	91	87	86	95	87
Oxygen saturation (%)	100	100	100	100	100

The surgery lasted 50 min. At the end of the procedure, 5 ml 0.125% bupivacaine was administered via an epidural catheter for postoperative analgesia.

After surgery, the patient was transferred to the labor room for observation. Cardiovascular surgeons remained on standby during emergencies. The epidural catheter was maintained for 3 days postoperatively and removed under aseptic precautions. Prior to discharge, TTE was performed, and no new changes were observed. The patient was discharged on postoperative day 7.

DISCUSSION

Congenital heart abnormalities have been reported in approximately 1% of all live births, with only 10% surviving until adolescence without surgery. Most patients remain undiagnosed until the third or fourth decade [5]. Morbidity and mortality related to cardiac disease in pregnancy account for approximately 1–4% of all pregnancies [6]. Patients with heart disease cannot tolerate the cardiovascular, respiratory, endocrine, or renal changes during pregnancy. The WHO pregnancy risk category system classifies patients into four groups based on the likelihood of morbidity and mortality. Patients belonging to the WHO pregnancy risk category four are usually recommended to continue the pregnancy because of the risks posed to both the mother and fetus [7].

Pulmonary stenosis involves a narrowing of the right ventricular outflow tract and can occur at the subvalvular, valvular (most common), or supravalvular level. Pulmonary stenosis can occur as an isolated defect or a congenital anomaly. Signs and symptoms are based on the degree of stenosis. Complications of severe stenosis include right ventricular failure and arrhythmia. The management of pulmonary stenosis is based on the degree of stenosis, transvalvular gradient, and valve [8]. Pulmonary valvuloplasty is the treatment of choice and should be performed in patients with a peak gradient of > 64 mmHg unless pulmonary stenosis is complicated by factors such as a dysplastic valve, supra- or subvalvular stenosis, associated severe pulmonary regurgitation, and other concurrent cardiac surgeries [9]. In patients undergoing pulmonary valve balloon dilatation (PVBD) for severe pulmonary stenosis, the procedure is considered successful when the peak-to-peak gradient is reduced by at least 50% of the initial value. Post-PVBD, the peak gradient reduced by more than 50% of the initial value in our case. The ideal time for valvuloplasty is at 14 and 28 weeks of gestation. Management requires a multidisciplinary approach involving obstetricians, neonatologists, cardiologists, anesthesiologists, and cardiovascular surgeons. In our case, the patient refused a trial of labor and was scheduled for elective LSCS, considering fetal growth retardation and decreased amniotic fluid index, under steroid coverage for fetal lung maturity. In such cases, the choice of anesthesia is based on the patient’s current cardiac status. General anesthesia is usually the preferred choice in such cases because of the risk of hypotension and subsequent right heart failure with neuraxial techniques, especially spinal anesthesia alone [10]. However, the use of CSE offers the advantage of providing a rapid onset of blockade with low-dose spine along with the flexibility of extending the block with an epidural [11]. In this case, CSE was preferred over general anesthesia given the stable hemodynamics preoperatively (NYHA class 1) to avoid increases in the right ventricle afterload associated with intubation and mechanical ventilation. Low-dose spinal anesthesia with graded epidural administration in the patient did not lead to hypotension.

Hemodynamic instability due to right ventricular failure, arrhythmia, and pulmonary hypertension is an alarming surgical complication in such patients. A maximum increase in the cardiac output immediately after delivery can lead to additional stress in the hypertrophied right ventricle. Milrinone is a phosphodiesterase III inhibitor with high selectivity for the pulmonary vasculature when delivered via an inhaled or nebulized route, causing pulmonary vasodilatation and increased right ventricular contraction. The intravenous use of milrinone may cause systemic hypotension, which can be detrimental in such cases. Hence, in our patient, milrinone was administered via nebulization, an administration route which has minimal side effects, to avoid right ventricular dysfunction due to increased preload and promote forward flow across the pulmonary valve [12]. Despite the off-label use of nebulized milrinone in our case, its benefits have been reported in preclinical studies and it has been used safely within recommended doses [13].

In conclusion, this case highlights that the management of pregnant patients with cardiac disease requires careful planning, risk stratification, and preoperative optimization. The choice of anesthetic depends on the patient’s cardiac status and hemodynamics. The use of CSE reduces the stress response to surgery, minimizes myocardial depression associated with anesthetic drugs, and improves postoperative pain control. Techniques such as milrinone nebulization may help lessen the hemodynamic perturbations associated with auto-transfusion post-delivery.