Pulmonary arterial hypertension (PAH) is a common complication in patients with congenital heart defects (CHD) [1]. Patients with PAH have reported markedly increased morbidity and mortality during general anesthesia (GA) and surgery, compared to normal patients [2,3]. Patients with PAH have higher risk of perioperative complications, such as right ventricular (RV) failure and systemic hypotension [4]. Since GA poses high risk to PAH patients, more suitable anesthetic management is needed for these patients. In recent years, some studies have suggested sevoflurane inhalation or insufflation sedation as an alternative sedation method [5-8]. We present a case of sevoflurane insufflation sedation for dental treatment in a five-year-old child with PAH.

A five-year-old male child with multiple dental caries was referred from local clinic due to his low body weight (11 kg) in January 2013. He was born with congenital heart defects (CHD) - heart with mass, tetralogy of fallot (TOF), large ventricular septal defects (VSD) and left ventricle (LV) to right atrium (RA) shunt - in December 2006. He underwent palliative operation of right modified blalock-taussing shunt (RMBT) in January 2007 and total correction operation in April 2009. He was diagnosed with hypertension (HTN) in 2007 and has been receiving inpatient care and hypertension medication ever since. He was diagnosed with tuberous sclerosis in January 2007 and has been receiving antiepileptic drug (AED).

The patient’s chief complaint was multiple dental caries. Results from the clinical and radiographic examination showed dental caries on #54, 55, 65, 74, 75, 84 and 85. Operation under sevoflurane insufflation sedation was planned in consideration of the patient’s medical history and to lower the risk of possible complications. The chest radiograph taken before the operation showed enlarged heart size and increased pulmonary vasculature (Fig. 1), confirming the previous diagnosis of CHD with left to right shunt.

Before the treatment, his parents’consent was acquired after the explanation of the entire sedation process was provided. Treatment was performed twice: Amoxicillin, 650 G, oral, administered 1 hour prior to each dental treatment as a prophylaxis to bacterial infection, and 8 vol% inspired sevoflurane gas administered using a full facial mask. After achieving loss of consciousness, the facial mask was substituted with a nasal cannula (Softech BI-FLO^® Cannula 1844, Teleflex Inc., Pennslvania, USA)(Fig. 2). This nasal cannula is composed of two parts, where one supplies the oxygen and sevoflurane and the other detects expired gas of the patient (Fig. 3). Sevoflurane vaporizer was set to deliver 100% oxygen at gas flow of 2.0 L/min. End-tidal sevoflurane concentration as well as patient’s respiration through capnography line of the nasal cannula was monitored throughout sevoflurane insufflation sedation. Inspired sevoflurane gas concentration was adjusted to maintain end-tidal sevoflurane concentration in the range of 1 to 1.5 vol%. Then, sedation depth was monitored using S/5 Entropy™ Module (Datex-Ohmeda Division, Instrumentarium Corporation, Helsinki, Finland)(Fig. 2). The patient was sedated throughout the operation while maintaining normal vital signs and spontaneous respiration. After completion of the dental treatment, sevoflurane was discontinued. The patient gained consciousness less than 5 minutes after discontinuation of sevoflurane. He was discharged from the hospital on the same day without any complications. All procedures during operation were performed under supervision of an anesthesiologist and were monitored applying the same standard as for GA. At the 3-months follow-up, the patient did not show any PAH-related complication and was referred back to the local clinic for further follow-up.

PAH is a complication of CHD with VSD and is associated with significant perioperative risk for major complications, such as RV failure and systemic hypotension [1,9]. PAH with increased pulmonary vascular resistance (PVR) is associated with considerable morbidity and mortality. An analysis on 156 children (median age 4.0 years) with PAH who had undergone noncardiac surgery demonstrated outcome of 1.17% cardiac arrest and 0.78% death [10]. Another analysis on 92,881 children younger than 18 years old who had perioperative caridiac arrest at a tertiary referral center found that all children undergoing noncardiac surgery or procedure demonstrated 0.029% cardiac arrest and 0.016% death [11].

General anesthesia causes decreases in functional residual capacity (FRC) and increases the chances of uneven distribution of ventilation. This may lead to a cascade of symptoms of ventilation-perfusion (V/Q) mismatch, hypoxia, hypoxic pulmonary vasoconstriction (HPV) and ultimately exacerbation of pulmonary hypertension [12]. Furthermore, increased PVR may lead to decreased RV function. Finally, RV failure can result in systemic hypotension [2,4,9,13]. Positive pressure ventilation during GA in PAH patients has high risk and should be conducted under the presence of well-trained professional anesthesiologist and with extra care.

In addition, airway instrumentation during GA can trigger a rapid increase in PVR [8]. Tracheal intubation has been reported to precipitate pulmonary hypertensive crisis and death in critically ill adult patients with severe PAH [14,15].

In other words, if possible, deep sedation may be safer than general anesthesia using positive pressure ventilation for patients with PAH. The patient in this case was born with CHD of large VSD and LV-RA shunt and had been taking HTN medication since 2007. For reasons stated above, the dental treatment was planned to be completed under deep sedation.

In numerous recent articles, sevoflurane inhalation and insufflation sedations have been suggested as new sedation methods [5-8,16]. Sevoflurane has low blood-gas partition coefficient, which allows rapid induction and emergence [17]. This characteristic is suitable in outpatient procedures. In general, sevoflurane is associated with clinical pulmonary vasodilation and is an accepted component of a balanced anesthetic technique in patients with PAH [2]. Especially, most of the previous reports on sevoflurane inhalation and/or insufflation sedations were conducted on premature or preterm infants, to whom general anesthesia imposes higher risk [7,8,16]. Therefore, sevoflurane inhalation and insufflation sedations can be used safely even in high-risk patient groups. In addition, the sedation depth can be easily controlled using inhalation and insufflation sedation, and they have auto-regulation effect, which also enables safer sedation [18].

Friesen RH and Alswang M stated, when spontaneous ventilation through the natural airway is used, end-tidal CO₂ should be monitored via nasal cannulae [19,20]. In this case, the nasal cannula connected to capnograph was used, as previously described by Kim, et al. [6]. This type of nasal cannula not only delivers sevoflurane gas, but also allows monitoring of respiration gases (oxygen, carbon dioxide and sevoflurane). It also takes up less space on patient’s face and allows wider access for the dental treatment (Fig. 2).

The procedural sedation was conducted with special attention to over-sedation, because over-sedation is associated with hypercarbia, hypoxemia and airway obstruction in patients managed with a natural airway and spontaneous ventilation [19,21]. Hypercarbia, hypoxemia and airway obstruction can trigger a rapid increase in PVR. As the appropriate dose of sevoflurane to achieve appropriate sedation depth varies per person, sedation depth was monitored by acquiring the electroencephalograph (EEG) and frontal electromyography (FEMG) signals using S/5 Entropy™ Module to prevent over-sedation and maintain proper sedation depth.

This successful case of dental treatment in a patient with PAH through sevoflurane insufflation sedation has shown that sevoflurane insufflation sedation can be used effectively and safely in PAH patients and opened doors to sevoflurane sedation in high risk patients. Deep sedation by sevoflurane insufflation may be used as alternative method of GA in the field of cardiopulmonary dysfunction and in high-risk patients.