General anesthesia during dental treatment in a pediatric patient with Fontan circulation using a minimally invasive cardiac output monitoring device

Abstract

This case report presents the hemodynamic management of a 3-year-old patient with Fontan circulation who underwent dental treatment under general anesthesia using minimally invasive cardiac output monitoring devices. To avoid the use of monitoring methods more invasive than the dental procedure itself, cardiac output was continuously assessed using FloTrac™ and BioZ.com™ systems. The bispectral index was maintained between 40 and 67 during anesthesia. Although the patient’s body surface area (BSA) was 0.5 m², which is below the validated threshold for both devices, monitoring was cautiously conducted to observe hemodynamic trends. Discrepancies in the cardiac output and index values were observed between the two modalities. Although the absolute values were less reliable owing to the patient’s low BSA, hemodynamic stability was maintained by tracking the dynamic changes in cardiac parameters. These observations underscore both the limitations and the potential of noninvasive cardiac monitoring in pediatric patients with Fontan circulation undergoing general anesthesia. Accordingly, future development of monitoring technologies that can accurately measure cardiac output in pediatric patients with BSA < 1 m² is warranted.

INTRODUCTION

Recently, the outcomes of pediatric cardiac surgery have significantly improved, leading to an increasing number of patients with unique hemodynamic conditions [1]. The Fontan procedure is a special circulation that directs venous blood to the pulmonary circulation while bypassing the right side of the heart [2].

Currently, minimally invasive cardiac output (CO) monitors, such as FloTrac™ and BioZ.com™, are available. We describe our experience administering general anesthesia during the dental treatment of a pediatric patient with Fontan circulation using a minimally invasive CO monitoring device.

CASE REPORT

A 3-year-old boy (height, 89.0 cm; weight, 11.0 kg; body mass index, 13.8 kg/m²; BSA, 0.516 m²) was scheduled for dental treatment under general anesthesia [3].

Past medical history: The patient’s appearance, pulse, grimace, activity, and respiration (Apgar score) at birth was 9/9 and the weight was 2,908 g. A heart murmur was detected, and the oxygen saturation (SpO₂) levels decreased from 89% to 72%. On day six, the patient was unresponsive to oxygen therapy and was transferred to the Neonatal Intensive Care Unit. The SpO₂ levels dropped to 60%, necessitating an emergency right-sided modified Blalock-Taussig shunt (RMBTS) procedure on day 10. At four months, the patient underwent a bidirectional Glenn (BDG) procedure and atrial septal defect enlargement surgery. The Fontan procedure (total cavopulmonary connection-extracardiac conduit [TCPC-EC] method) was performed at eight months.

Medication: The patient was receiving warfarin (0.75 mg/day) and aspirin (20 mg/day) as anticoagulants, along with imidapril hydrochloride (1.5 mg/day) for hypertension.

Present condition: At age of two years, the mother observed dental caries. Dental procedures were performed under general anesthesia due to multiple dental caries and uncooperative behavior during dental treatment.

Preoperative evaluation: The patient’s complexion was good, with no lip or nail cyanoses. The indoor SpO₂ level was 95–99%. The blood pressure (BP) was 104/61 mmHg and heart rate (HR) was 108 beats/min. No dyspnea was noted during routine activities. Blood tests showed a prothrombin time-international normalized ratio of 3.36 and a prolonged activated partial thromboplastin time of 43.7 s. Echocardiography revealed a left ventricular ejection fraction (Pombo) of 53%.

The cardiologist advised that owing to the Fontan circulation and the use of an artificial conduit, dental treatment under general anesthesia was at risk of infective endocarditis. Therefore, antibiotics were recommended 1 h before treatment and continued for at least three days after treatment to prevent infective endocarditis.

Intraoperative progress

The patient was admitted one day before surgery to establish intravenous access. Preoperative dietary restrictions began at midnight on the day of surgery and drinking was restricted to 6 am. Routine medications were administered at 6 am.

Upon arrival in the operating room, monitoring devices, including a pulse oximeter, electrocardiograph (ECG), automatic BP monitor, Bispectral Index, and BioZ.com™ (Dash3000, GE Healthcare) for CO monitoring, were attached. SpO₂ was 97%, BP was 95/55 mmHg, and HR rate was 95 beats/min.

Anesthesia, including 3% sevoflurane, 2 mg midazolam, 10 µg fentanyl citrate, and 5 µg/kg atropine sulfate, all administered intravenously, was induced with oxygen at 6 L/min. Rocuronium bromide (10 mg) was administered intravenously, and oral intubation was performed after confirming mask ventilation. The laryngoscopic view was Cormack I and intubation was straightforward.

Subsequently, a plastic cannula was placed in the right dorsalis pedis artery for invasive arterial pressure and CO measurements using a minimally invasive CO monitoring system (FloTrac™, Edwards Life Sciences). The measured parameters of CO, stroke volume, stroke volume variation, pulse rate, and mean arterial pressure were monitored (Fig. 1).

Fig. 1. Charts of the parameters obtained from the FloTrac™ and BioZ.com™ measurements. (A) The red line indicates CO obtained from FloTrac™. The blue line represents SVV. The green line shows CO obtained from BioZ.com™. (B) The yellow line indicates SV. The purple line represents PR. The green line indicates MAP. CO, cardiac output; MAP, mean arterial pressure; PR, pulse rate; SV, stroke volume; SVV, stroke volume variation.

Anesthesia was maintained using oxygen (1 L/min), air (1 L/min), and 2% sevoflurane. Additionally, 10 min before the procedure, 550 mg of ampicillin sodium was administered intravenously to prevent infective endocarditis. The ventilator was set to pressure-controlled ventilation with an adjusted pressure of 12 hPa, positive end-expiratory pressure of 5 hPa, respiratory rate of 22–25 breaths/min, and inspiratory-to-expiratory ratio of 1:1.5.

The BP was 85–95/35–45 mmHg, HR was 85–95 beats/min, body temperature was 37.1–37.5℃, end-tidal carbon dioxide was 36–39 mmHg, and bispectral index was 40–67 after the surgery. The cardiac index measured using the BioZ.com™ was 1.9–2.1 L/min/m². The ECG showed P-wave irregularities; however, no arrhythmias requiring immediate treatment were observed. Respiratory status was stable; a fraction of inspired oxygen was 0.55, arterial oxygen partial pressure was 117–177 mmHg, and arterial partial pressure of carbon dioxide was 39.4–-41.4 mmHg. A 2% lidocaine solution with epinephrine (1:80,000) was used as a local anesthetic. The total amount of epinephrine administered was 36.25 mcg/ml. Correction for acidosis was not necessary.

The administration of oxygen at a rate of 6 L/min facilitated awakening. The endotracheal tube was removed after confirming adequate spontaneous breathing and recovery of the bispectral index. The duration of anesthesia was 3 h and 23 min. FloTrac™ and BioZ.com™ were monitored until the endotracheal tube was extubated and the patient was awakened. Postoperatively, the patient showed no signs of heart failure and resumed routine medications on the evening of the same day. The patient was discharged on the following day.

DISCUSSION

The Fontan procedure is a palliative surgery for congenital heart disease in which two-ventricle repair is impossible. In such cases, it functions as a single ventricle. Specific conditions include hypoplastic left heart syndrome, tricuspid atresia, and pure pulmonary atresia [4]. In this case, the patient had tricuspid atresia and congenital pulmonary stenosis and underwent the Fontan procedure after RMBTS and BDG surgeries.

Over time, variations in the Fontan procedure have developed, which is an essential factor in anesthesia management [5]. The three forms of the Fontan procedure are the atriopulmonary connection, total cavopulmonary connection with a lateral tunnel, and TCPC-EC (Fig. 2).

Fig. 2. Schematic diagrams of the Fontan procedure. (A) APC method. (B) TCPC-LT method. (C) TCPC-EC method. APC, atriopulmonary connection; TCPC-EC, total cavopulmonary connection with extracardiac conduit; TCPC-LT, total cavopulmonary connection with lateral tunnel.

The Fontan procedure establishes a unique circulatory system called the Fontan circulation, where blood from the superior and inferior vena cava, and sometimes the hepatic veins, flows directly into the pulmonary arteries. Fontan circulation improves cyanosis; however, the absence of a pump to propel blood into the pulmonary arteries means that the driving pressure for the pulmonary blood flow, the transpulmonary gradient (TPG), is determined by the difference between the central venous pressure (CVP) and functional left atrial pressure (LAP) [4]. That is, TPG = CVP - LAP = CVP - left ventricular end-diastolic pressure.

Consequently, the blood flow in patients with Fontan circulation is slow, which increases the risk of thromboembolic events and infective endocarditis [4]. Therefore, anticoagulant therapy with warfarin and aspirin was continued, and antibiotics were administered before initiating dental treatment.

Key factors in anesthesia management for patients with Fontan circulation are the continuation of anticoagulant and preoperative antibiotic administration, as well as minimizing pulmonary vascular resistance to enhance pulmonary blood flow [4]. This means avoiding hypothermia, hypoxemia, hypercapnia, acidosis, or high airway pressure. Furthermore, because a decreased preload can lead to reduced CO levels, careful attention to dehydration and blood loss is necessary. In this case, intravenous access was secured the day before the procedure and fluid management was performed to prevent dehydration. A slightly lower airway pressure minimized pulmonary vascular resistance and increased the respiratory rate during the procedure.

Continuous pulmonary artery catheter-based CO monitoring is widely used for perioperative CO monitoring. However, it is only used when its benefits outweigh the invasive nature of the procedure. For pediatric patients undergoing minimally invasive dental treatment, the invasiveness of inserting a pulmonary artery catheter is much higher than that of the catheter itself, making the procedure unsuitable for children.

FloTrac™ uses arterial pressure waveform analysis to continuously measure CO [6]. According to Fujiwara et al., FloTrac™ is useful for the perioperative management of dental treatment under general anesthesia [7]. BioZ.com™ measures CO by recording impedance waveforms from electrodes placed on both sides of the neck and chest, and is non-invasive, cost-effective, and capable of measuring each heartbeat [8]. Therefore, for this patient with a history of thoracotomy, continuous CO monitoring was performed using the minimally invasive and noninvasive devices, FloTrac™ and BioZ.com™, respectively.

However, these monitors have limitations, particularly for patients with body surface areas (BSA) outside the specified range. FloTrac™ and BioZ.com™ are suitable for patients with a BSA ranging from 1.44 to 5.29 m² in height and 30 to 155 kg in weight. In this case, the patient had a BSA of 0.5 m². FloTrac™ and BioZ.com™ set the lower limit of BSA to 1 m², and the patient’s BSA was significantly below this lower limit. Consequently, differences were observed in the CO and CI values measured using FloTrac™ and BioZ.com™. The BioZ.com™ monitor cannot be set for BSA below 1 m²; therefore, the BioZ.com™ monitor was set to 1 m² for the measurement. The values of CO and CI measured by the BioZ.com™ monitor ranged from 1.9 to 2.0 (Fig. 3). The differences in measurement results between the FloTrac™ and BioZ.com™ monitors may have been due to the arterial access site being the dorsalis pedis artery rather than the radial artery.

Fig. 3. Monitoring with the BioZ.com™ device. (A) The measurement image of the BioZ.com™ monitor. (B) The BioZ.com™ monitoring sensor being attached.

The reliability of the measured values was low, given that the patient’s BSA was significantly < 1 m². However, management was achieved by focusing on changes in measured values without causing significant hemodynamic fluctuations. Future developments in devices that accurately measure CO in pediatric patients with BSA < 1 m² are required.