Scimitar syndrome is a rare complex of congenital anomalies of the cardiopulmonary system.1 Although its incidence has been reported to be 1–3/100,000 live births,2 exact incidence may be higher due to the cases with asymptomatic course.3 This syndrome is typically characterized by hypoplasia of the right lung and the main pulmonary artery, abnormal pulmonary venous drainage, cardiac dextroposition, anomalies of tracheobronchial tree, cardiac anomalies, and elevation of the right hemidiaphragm.4,5 Two main forms of this syndrome, infantile and adult, have been described. The adult form is diagnosed incidentally, and some patients may be completely asymptomatic.2,3,6 The limited number of case reports in the literature describing patients with scimitar syndrome focus primarily on surgical treatment of the disease.7,8 Herein, we discuss the anesthetic management and position-related oxygenation and hemodynamic changes in an adult patient with scimitar syndrome
The patient provided written Health Insurance Portability and Accountability Act authorization.
A 58-year-old, 80-kg, 163-cm woman presented for left total mastectomy and axillary dissection under general anesthesia. Her medical history was significant for a spontaneous vaginal delivery and a cesarean delivery under general anesthesia when the patient was 30 and 32 years of age, respectively. Our patient had no complaint about any respiratory problems except for dyspnea in the lateral left decubitus position.
Her posteroanterior chest x-ray revealed a scimitar-shaped density enhancement in the right parenchymal area and an increased cardiothoracic index (Figure). On transthoracic echocardiography, a normal ejection fraction was observed together with minimal tricuspid insufficiency, dilation of the right structures, left ventricular diastolic dysfunction, partial pulmonary venous return anomaly, and a secundum atrial septal defect. Chest tomography revealed a unilobar right lung with no fissure and right pulmonary veins draining into the inferior vena cava. These radiological findings were the typical signs of scimitar syndrome. The results of preoperative arterial blood gas analysis were as follows: pH 7.42, Paco2 35.5 mm Hg, Pao2 57 mm Hg, oxygen saturation (Sao2) 89.5%, and HCO3 23.6 mmol/L.
Because of her history of dyspnea in the left lateral decubitus position, we performed positional testing of her heart rate, blood pressure, and Sao2 in standing, supine, Trendelenburg, reverse Trendelenburg, and right and left decubitus positions for 5 minutes each (Table).
The patient with normal sinus rhythm on electrocardiography had a heart rate of 97 beats/min, an invasive blood pressure of 150/90 mm Hg, and an Sao2 of 92% before anesthetic induction. For induction, lidocaine 1 mg/kg, thiopental 4 mg/kg, rocuronium 0.6 mg/kg, and fentanyl 2 µg/kg were administered intravenously. Orotracheal intubation was performed without problem, and the patient was mechanically ventilated with tidal volume 7 mL/kg, positive end-expiratory pressure 5 cm H2O, respiratory frequency 14 breaths/min, and 50% oxygen and 50% air. She was then placed in the supine-slightly right lateral position. Anesthesia was maintained by adding fentanyl boluses (total dose, 100 µg) and a ketamine infusion. Her Spo2 increased after anesthetic induction and mechanical ventilation to 98% at the end of surgery that lasted for 170 minutes. Her arterial blood gas analysis at this time was pH 7.42, Paco2 36.8 mm Hg, Pao2 112 mm Hg, and Sao2 98.2%. Hemodynamic stability was maintained during the surgery. The patient developed no problems during 24-hour close monitoring in the intensive care unit. She was then admitted to the clinic and discharged after 72 hours.
The number of adult patients with congenital cardiopulmonary disease, as in the present case of scimitar syndrome, undergoing noncardiac surgery is gradually increasing.9 Diagnosis of the adult form of scimitar syndrome is frequently established incidentally; some patients may be completely asymptomatic except for recurrent pulmonary infections,2,3,6 and the disease may be overlooked because the patient is asymptomatic during normal daily activities and physicians rarely encounter this syndrome.2 Although the present patient underwent cesarean delivery under general anesthesia when she was 32 years of age, typical radiological features of scimitar syndrome were not detected at that time because of the absence of clinical signs and no chest x-ray.
Hemodynamic changes are less common in the adult form of scimitar syndrome, and many patients maintain their lives with no need for surgical correction.2 But the presence of dyspnea in the left lateral position suggested that there could be positional hemodynamic and oxygenation changes in the pulmonary venous return and blood flow of vena cava in our patient during surgery and recovery. It was observed that blood pressure, heart rate, and Spo2 were lower in the left lateral decubitus position than in the right lateral decubitus position.
In the present case report, we want to “emphasize primarily the importance of positional oxygenation change” in our case. Although respiratory complaints have been addressed in the case reports presented previously,2,3,6,10 there is no information about a test performed for the presence of positional hypoxemia. This is a simple test and may suggest anesthesia and surgery-related concerns that are likely to develop on induction, during positioning, or in recovery.7,10,11
Normally, in the lateral decubitus position, ventilation-perfusion changes occur with anesthesia in patients who have normal lung anatomy with spontaneous breathing and closed chest wall as well as normal pulmonary vascular bed. While functional residual capacity (FRC), compliance, and ventilation decrease in the downside lung as compared to the upside lung, perfusion increases.12 Mediastinal configurations compress the downside lung, and thus, physical enlargement of this lung is prevented and FRC selectively decreases in the downside lung. In addition, abdominal structures push the diaphragm, paralyzed under anesthesia, in a cephalic direction, compress the downside lung, and disproportionally reduce the FRC of the downside lung. All these changes led to impairment in ventilation-to-perfusion ratio.12,13
The surgical necessity of a slightly right lateral position in the present case required for the left mastectomy meant the hypoplastic lung was the downside lung. This seems to have been protective for the patient. Although how the known cardiac pathologies affect total pulmonary perfusion in the right lateral position is not known, increased ventilation is possible in healthy lung that is not hypoplastic. Moreover, we think that applying a positive end-expiratory pressure of 5 cm H2O contributed to the regulation of ventilation in the downside right hypoplastic lung.12,14 Consequently, placing the patient with scimitar syndrome in the supine-slightly right lateral position enabled maintenance of the drainage of aforementioned vascular bed and ventilation of the lungs under optimal conditions. Thus, Spo2 values gradually increased during the procedure. This result was also anticipated by the preoperative test. While oxygenation was good when the patient was in the right lateral position, left lateral position resulted in impaired ventilation-perfusion balance and hypoxemia. Obviously, assessment of oxygenation changes by preoperative position test and accordingly reevaluation of blood flow of cardiopulmonary vascular bed via radiological methods or echocardiography might be important in some severe cases.
Preferring ketamine infusion in combination with fentanyl, which has minimum depressing effect on systemic vascular resistance and the myocardium, instead of inhalation anesthetics might have contributed to the maintenance of a stable hemodynamics.9,10,14 Different anesthetic strategies may be useful in other patients with scimitar syndrome depending on the complexity of the anomalies and the positioning required for surgery. In a 58-year-old patient who underwent thoracoscopy with intermittent apnea during general anesthesia, segmental left lobe resection was performed successfully with endobronchial left lung intubation. Spo2 was maintained above 93%, and only mild hypotension, responsive to ephedrine, was observed.15 Tolerance of this operation may again be related to the right decubitus positioning as in our patient.
In conclusion, patients with scimitar syndrome should be assessed preoperatively for positional Sao2 and hemodynamic changes related to position required for surgery and for recovery. It is likely that surgery in the left lateral decubitus position may present with hypotension and oxygen desaturation that will require addressing by the anesthesia team.
Name: Demet Sergin, MD.
Contributions: This author helped prepare the manuscript, and analyze and interpret the data.
Name: Burçak Tanatti, MD.
Contributions: This author helped prepare the manuscript and helped with acquisition of the data.
Name: Sezgin Ulukaya, MD.
Contributions: This author helped with manuscript control, manuscript conception and design, and final approval of the version to be published.
This manuscript was handled by: Raymond C. Roy, MD.
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