Several recent studies have shown that frequent emergency room (ER) visits among children are due to dental trauma [1,2]. Majewski et al, [2] documented 39% of children came to ER due to dental causes and more than one-half of the patients were 5 years old or younger. Perez et al. [3] indicated most injuries occurred at oral soft tissue and anterior teeth.

Oftentimes, emergency room doctors encounter difficulty in treating these patients. Pediatric patients are difficult to communicate and uncooperative upon command. Especially, a panic causing injury aggravates these confusing state. Therefore, proper anesthesia technique is crucial to render successful emergency dental treatment. Oral sedative drug such as chloral hydrate has been widely used in pediatric emergency treatment, but cannot be the best choice because of its slow onset of action.

Deep sedation with open airway rather than general anesthesia is recommended in this case. General anesthesia takes long induction time, can cause sore throat due to laryngeal edema, and delays recovery of consciousness. Sury et al, [4] reported the success of sevoflurane deep sedation via nasal cannula in infants undergoing MRI. We modified the nasal cannula for easier applying to children and conducted 11 emergency cases who had dental emergency treatment under sevoflurane deep sedation insufflated via a nasal cannula. In the present study, the authors present our useful experience.

Pediatric patient visiting ER because of dental trauma needs immediate treatment. To achieve successful dental treatment for uncooperative patient, anesthesia is very important. General anesthesia has been widely used for pediatric dental trauma treatment. However, general anesthesia is not suitable for emergency treatment for several reasons. First and foremost, general anesthesia requires long induction time, which makes it difficult in emergency cases. According to Kim et al, [5], average induction time for general anesthesia was 32 minutes. Second, essential endotracheal intubation causes many complications such as additional trauma and sore throat due to laryngeal edema or arytenoid dislocation [3]. Another major problem is delayed recovery of consciousness [3]. Lastly, application of ventilator could cause ventilation-perfusion mismatch that may lead to hypoxemia. For these reasons, oral sedative drug such as chloral hydrate has been suggested as an alternative. But it also has its own shortcomings; it takes long onset of action and recovery time.

Deep sedation using sevoflurane as a sedative has been done in several dental procedures. Sevoflurane is a predictable anesthetic medication, which is also fast on its onset and recovery. It has rapid adjustment of anesthetic depth and high safety profile regarding cardiovascular system [6]. Several cases were completed with deep sedation using sevoflurane inhalation via nasal hood or nasal cannula for short-term dental treatment [7]. Kim et al. [6,7] reported cases of sevoflurane inhaled deep sedation using nasal hood and nasal cannula. Ji et al, [8] reported 14 cases dental treatment under sevoflurane sedation, but of 14 cases, only 3 were emergency dental treatment. This report analyzed dental and anesthetic records of 11 patients who had emergency dental treatment under sevoflurane sedation, by far the largest study. Previous report used nasal hood for brief dental procedures [6]. Nasal hood has good sealing effect and ability to provide large amount of oxygen without resistance. However, nasal hood itself can be an obstacle to dental procedure because most of the traumatic injury mainly affect upper anterior portion of mouth where nasal hood is placed. To overcome this, nasal cannula was used in this study. For optimal use, couple of factors needs to be considered. When nasal cannula is placed too deeply into the nares, the cannula itself can act as an obstruction to the patient. Diameter of nasal cannula also needs to be considered. If it fits too tightly into the nares, it disturbs patient's spontaneous breathing. On the contrary to this, if it fits too loosely into the nares, the supply of oxygen / sevoflurane becomes inefficient. Therefore it is very important to choose the right-sized cannula with enough gap to minimize obstruction and without disturbing oxygen / sevoflurane supply. Since sevoflurane inhalation sedation via nasal cannula was first reported by Sury et al, [4] for MRI scan, only the sedative effect has been widely accepted. When the procedure causes pain, analgesic effect of sevoflurane is additional benefit to keep patients sedated. Previously, propofol and remifentanil intravenous injection was used for sedation and analgesia. But intravenous injection is a difficult and invasive procedure to the uncooperative patient, and it can induce pain and fear. In this study, patients did not show movements or awakening during painful procedure such as extraction and injection. We additionally used papoose board not for restraint but for fall prevention. After induction of deep sedation, no physical restraint was needed. Sevoflurane has been reported to cause nausea and vomiting during recovery [9], but no significant adverse effects were observed in this study. In deep sedation procedure with open airway, monitoring is important [5]. Especially, medication such as sevoflurane affects respiratory depression more than cardiovascular system. In respiratory monitoring, capnography shows the most sensitive monitor for ventilation. During the sedation, ETCO₂ and ETS showed continuous fluctuation. Moreover, the two elements were in inverse proportion to each other. When there was no problem on nasal breathing, ETCO₂ and ETS shows to the nearest 40 mmHg and 1 vol% respectively. But when patients showed difficulty in breathing or dominantly breathed through their mouth, ETCO₂ fell and ETS rose. It is because the nasal cannula we used has back-to-back air supply and detector. In other words, air detector dominantly detected not patient's expired gas but supply gas when the patients' nasal breathing decreases. In this case, while the value of ETS was high, actual patient's insufflated concentration of sevoflurane decreased. Decreased insufflated concentration of sevoflurane made patient easily arousable. Therefore, it is important to maintain ETCO₂ within normal range during the sevoflurane sedation. ETS at this time reflects actual patient's end- tidal concentration of sevoflurane. In this study, delivered sevoflurane concentration was 3-4 vol% for deep sedation but average ETS was 2.2 vol%, but actual patient's end-tidal concentration of sevoflurane which is lower than 2.2 vol% by concentration effect and so depth of sedation level is lower than 1 MAC [10]. Difference between supplied concentration of sevoflurane and ETS was found. It's because fluctuation of ETS and dilution effects. Sevoflurane gas might dilute by atmosphere and passing through anatomical dead space because it's not closed breathing circuit. From these cases, emergency sevoflurane sedation to uncooperative pediatric patient was successful. Especially for pediatric patient, the airway of the children is relative to the rear than adults. For this reason, children are often caused airway obstruction than adults. However, proper monitoring (capnography, gas analyzer) is important for safe and effective sedation. If proper cases were selected, sevoflurane sedation would bring a satisfying result to dentist, patient and parents.