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Year : 2015  |  Volume : 33  |  Issue : 3  |  Page : 239-244

Evaluation of nitrous oxide inhalation sedation during inferior alveolar block administration in children aged 7-10 years: A randomized control trial

1 Department of Paedodontics and Preventive Dentistry, Manipal University, Manipal College of Dental Sciences, Mangalore, Karnataka, India
2 Department of Public Health Dentistry, Manipal University, Manipal College of Dental Sciences, Mangalore, Karnataka, India

Date of Web Publication9-Jul-2015

Correspondence Address:
Dr. Arathi Rao
Department of Paedodontics and Preventive Dentistry, Manipal College of Dental Sciences, Manipal University, Light House Hill Road, Mangalore - 575 001, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0970-4388.160399

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Background: Nitrous oxide-oxygen (N 2 O-O 2 ) is being used in combination with many drugs and this possess risk for leading to deep sedation or reflexes being compromised. Aim: The purpose of our study was to use N 2 O-O 2 alone, to evaluate its effectiveness for pain control during inferior alveolar nerve block administration in children. Design: This was a single-centered, simple randomized, double-blinded, placebo-controlled parallel-group study involving 40 children in the age group of 7-10 years divided into 2 groups: N 2 O-O 2 sedation and oxygen. Pain perception for local anesthesia was assessed using face, legs, activity, cry, consolability scale. Children's behavior was assessed using Frankl ratings, depth of sedation using Observer's Assessment of Alertness/Sedation scale. The vital signs and oxygen saturation were recorded. Results: There was a significantly lower pain reaction to local anesthetic administration in the N 2 O-O 2 group (P < 0.01). Improvement in the behavior of the children belonging to N 2 O-O 2 group during and after the procedure as compared to the O 2 group (P < 0.01) was also observed. All the vital signs recorded were in the normal physiologic limits in both the groups. Conclusion: Pain experienced by children receiving N 2 O-O 2 sedation was significantly lower. N 2 O-O 2 inhalation sedation produces adequate sedation with vital signs within normal limits and treatments successfully completed.

Keywords: Behavior, conscious sedation, nitrous oxide, pain

How to cite this article:
Takkar D, Rao A, Shenoy R, Rao A, Suprabha BS. Evaluation of nitrous oxide inhalation sedation during inferior alveolar block administration in children aged 7-10 years: A randomized control trial. J Indian Soc Pedod Prev Dent 2015;33:239-44

How to cite this URL:
Takkar D, Rao A, Shenoy R, Rao A, Suprabha BS. Evaluation of nitrous oxide inhalation sedation during inferior alveolar block administration in children aged 7-10 years: A randomized control trial. J Indian Soc Pedod Prev Dent [serial online] 2015 [cited 2022 Aug 17];33:239-44. Available from: http://www.jisppd.com/text.asp?2015/33/3/239/160399

   Introduction Top

Nonpharmacological behavior management techniques are routinely used and suffice to create an environment that facilitates the development of child's confidence and allows the dentist to carry out procedures with minimal disruption. However, in case of very fearful or anxious children, these techniques may not be sufficient and conscious sedation may prove to be a helpful tool. [1]

Use of pharmacological behavior management techniques such as nitrous oxide (N 2 O) conscious sedation coupled with local anesthesia when required forms the foundation of the delivery of pain-free dentistry to children. [2]

Nitrous oxide-oxygen (O2) was frequently used in combination with many drugs such as chloral hydrate, hydroxyzine, midazolam. The majority of the studies used N 2 O in combination with other agents to obtain the desired effects. [3],[4],[5],[6],[7],[8],[9] N 2 O when combined with other agents possess risk as the combination can have synergistic action and potential for central nervous system depression is magnified and lead to deep sedation or general anesthesia such as effect [10],[11],[12],[13] with reflexes being compromised.

Administration of local anesthesia often leads to high anxiety and unco-operative behavior in children. Nerve block anesthesia is known to be more painful and least accepted by children. The purpose of our study was to use N 2 O-O 2 alone to evaluate its effectiveness for pain control during inferior alveolar nerve block administration in children.

   Materials and Methods Top

This was a single-centered, simple randomized, double-blinded, placebo-controlled parallel-group study. Sample size was calculated with a power of 0.90 at 95% confidence level. Forty children in the age group of 7-10 years were selected after screening for inclusion and exclusion criteria for children attending for dental treatment in a pediatric dental department. The study was carried over a period of 6 months.

Inclusion criteria

The inclusion criteria were as follows: Dental treatment to be done under inferior nerve block anesthesia; subjects who belong to Frankl 2 and 3 rating during examination process; subjects belong to American Society of Anesthesiologists 1 category; written informed consent from the parents/guardians.

Exclusion criteria

Exclusion criteria were as follows: Clinical condition contraindicating the use of N 2 O-O 2 ; subjects with known allergy to lignocaine.

Ethical clearance

Ethical clearance was obtained from the Institutional Ethics Committee approval prior to the commencement of the study. Detailed information regarding the procedures, risk involved, etc. contained in the patient/information sheet was given to the parents, and all queries answered. After obtaining written informed consent from parents, verbal consent was taken from the children prior to the study.


Subjects were randomly allocated into two Groups-A and B using the chit-pick box method. Group A (n = 20) were given N 2 O-O 2 sedation and Group B (n = 20) only oxygen as placebo. Twenty chits were made for each group and kept in a box. Each child was asked to pick a chit and accordingly he/she was allocated into the group.


Three investigators were involved in the study:

  1. Administrator - Person administering sedation (N 2 O-O 2 and oxygen).
  2. Observer - Person monitoring the child and recording the scales and vital signs.
  3. Operator - Person who carried out the dental procedure.

The subject and the observer were blind to the agent used during the procedure. The child picked the chit and gave it to the administrator, who noted down the same in a separate log book. The observer was seated in such a manner that the N 2 O unit and display was not visible.

Sedation and treatment protocol

Preprocedural evaluation

Child's airway was assessed. Extra- and intra-oral physical examination were done. Before commencing the sedation process, child's behavior was again determined using Frankl scale. [14]. The vital signs (pulse, respiratory rate) and oxygen saturation were evaluated prior to the dental treatment.


A compact, portable machine (Quantiflex MDM, USA) permitting continuous flow of N 2 O and oxygen, with monitored dial mixer for N 2 O-O 2 was used for the study. Well-fitted nonscented nasal hoods were used.

The technique [15],[16] was described to the patient as per the child's level of understanding using euphemisms. Group A: A flow rate (liter per minute) of 100% oxygen was established, and the nasal hood was secured on the patient's nose. The hood was adjusted suitably for child's comfort. The appropriate flow rate was established while the child was breathing 100% oxygen (5-6 l/min) for 1-2 min. Nasal breathing was encouraged, and the nasal hood was checked for leaks. The reservoir bag was monitored that it should remain uniform during breathing and should not expand or shrink. The percentage of N 2 O was started initially at 10%. Then, it was titrated in approximately 10% increment rise every 60 s. The N 2 O was titrated up to 30-40%. Constant communication with the child including physical, visual and verbal contact was maintained. Once the objective signs of sedation were observed (child became relaxed, spontaneous movements decreased, abduction of feet); the child was questioned how as to how he or she was feeling. When the child stated that he or she was feeling pleasant and relaxed, it was concluded that the ideal level of clinical sedation was achieved and the dental treatment was initiated. As the treatment ended and the need for sedation requirement ceased, the N 2 O flow was tapered and the child was given 100% oxygen at a flow rate equivalent to the established rate for him or her 3-5 min before terminating the sedation process to prevent diffusion hypoxia and allow complete recovery from sedation. The child was discharged if the presedation level of responsiveness or a level as close as possible to normal was achieved.

Group B: In the oxygen group, 100% oxygen was administered and appropriate flow rate was established as for the nitrous-oxide/oxygen group. After 5 min of administering oxygen, the procedure was initiated.

Local anesthesia administration

All the children selected for the study needed pulp therapy to be done under inferior alveolar nerve block. Children were explained regarding the procedure using euphemisms. Inferior alveolar nerve block was performed using the conventional technique after application of topical anesthesia. A volume of 1.5 ml of 2% lignocaine hydrochloride with 1:100,000 adrenaline (Neon, India) was used through a 30 gauge, 25 mm long needle. The rate of injection was standardized at 1 mm/min.

Data collection

The pain perception during and after administration of local anesthesia was assessed using face, legs, activity, cry, consolability (FLACC) [17] scale [Table 1] and [Table 2]. The child's behavior during and after administration of local anesthesia was recorded.
Table 1: FLACC behavioral pain assessment scale

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Table 2: Interpretation of the FLACC scores

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Once optimal sedation was obtained, the depth of sedation was assessed using Observer's Assessment of Alertness/Sedation (OAA/S) scale [18] [Table 3] and [Table 4]. The depth of sedation for the Group B was analyzed after administering oxygen for 5 min.
Table 3: OAA/S Scale

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Table 4: Interpretation of the OAA/S Scale

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The vital signs (pulse, respiratory rate), oxygen saturation were recorded every 3 min from the start of the sedation process to the end of local anesthesia administration. All the recordings were done for both the groups.

Statistical analysis

The obtained data were compiled systematically and analyzed using SPSS for Windows release 19.0 (SPSS Inc., Chicago, IL, USA). The level of significance was kept at P < 0.05. The analysis of the behavior rating, level of sedation and pain felt by children was done using Pearson Chi-square test.

The physiologic parameters-partial pressure of oxygen, heart rate and respiratory rate were evaluated using repeated measures of ANOVA.

   Results Top

Of 40 children involved in study, 24 (60%) were females, 16 (40%) were males. The duration of local anesthesia administration of ranged from 9 to 15 min depending on the behavior management and requirement of sedation for each child.

Baseline demographic and clinical characteristics are explained in [Table 5]. Behavior recording, OAA/S, FLACC scale and vital sign recordings during the procedure is given in [Table 6], [Table 7], [Table 8].
Table 5: Baseline demographic and clinical characteristics

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Table 6: Behavior recording during and after administration of local anesthesia

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Table 7: OAA/S and FLACC Scale scores during the procedure

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Table 8: Average scores of the vital signs recorded during the procedure

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Frankl behavior rating

Local anesthesia was administered successfully to all the children in both the groups. Chi-square test revealed that at baseline, there was no statistically significant difference between the groups (P = 0.204). However, there was a statistically significant difference in the behavior of children during and after the procedure in the two treatment groups (P < 0.01). Few children remained uncooperative till the end of the procedure but continued to hold the hood over the nose.

Level of discomfort/pain/both

The level of discomfort or pain was assessed using the FLACC scale. Significant difference was observed in the level of discomfort experienced by children between both the groups (P < 0.01).

Level of sedation

The level of alertness or sedation was evaluated using the OAA/S scale. In the N 2 O/O 2 group, 2 children were alert, 13 lightly sedated, and 5 were moderately sedated during the treatment. In the O 2 group, 19 children were alert and 1child appeared sedated. The difference was significant.

Vital signs and oxygen saturation

The values of all the physiologic parameters were in the normal clinical range throughout the sedation period. There was no statistically significant difference found in either of the groups as measured by the repeated measures of ANOVA. (P = 0.894, 0.774, 0.894 respectively for partial pressure of oxygen , heart rate, respiratory rate).

   Discussion Top

The present study examined the effect of N 2 O-O 2 on the behavior pattern, level of sedation attained and pain experienced by children during dental procedures. Children between 7 and 10 years of age were chosen for the study because at this age they can understand the verbal explanation given to them regarding enrollment to the study. Total of 16 males and 24 females subjects were part of the study. Gender is not known to influence subjective response to N 2 O sedation. [19]

All the children who participated in the study had not been exposed to N 2 O sedation earlier. This and allocation concealment shielded the participants from being influenced to the effects of past experience. Plain oxygen group was used as a placebo-controlled parallel design in the study. Cross over design was not chosen as this may influence the child's behavior. Administering inferior alveolar block was chosen as this procedure is found to be less tolerated in children compared to other dental procedures. About 90-95% of the children were co-operative (Frankl rating 3 or 4) during and at the end of local anesthesia administration.

In a clinical study by Houpt et al., [20] 100% of the children became cooperative exhibiting Frankl 3 or 4 rating. From the clinical standpoint, adequate improvement in children's behavior was observed in the present study with N 2 O-O 2 .

In the present study, Frankl behavior rating was used to assess the child's behavior. Frankl rating has been found to be efficient in clinical practice and revealed a direct relationship between the predicted behavior and the actual manifested behavior during dental appointments. [21]

Inadequate relief of procedural pain and distress affects the experience of children and their parents, and also adversely affects the procedural success. N 2 O analgesia works by anxiolysis that allows the patient to tolerate unpleasant procedures by reducing discomfort, thereby expediting the delivery of procedures. [5]

Pedersen et al. [22] reviewed the safety and efficacy of N 2 O and found it to be effective during brief, but mild to moderately painful pediatric procedures.

In our study, most of the children in N 2 O-O 2 group were relaxed (45%) or exhibited mild discomfort (45%) during local anesthesia administration.

Several studies in literature have used visual analog scale (VAS) which children rate their pain at the end of the procedure. However, owing to its subjective nature; this can be inconsistent in children especially after an episode of sedation. In the present study, the FLACC scale was thus used as it is observed by an independent observer. The FLACC behavioral pain tool has excellent reliability and validity in assessing pain in children. The scale has five criteria, which are each assigned a score of 0, 1 or 2. Each of the five categories (F) face; (L) legs; (A) activity; (C) cry; (C) consolability is scored from 0 to 2, which results in a total score between 0 and 10. [23]

The OAA/S scale used in the study is reliable and valid relative to the VAS. It is simple and quick to administer and requires little training. Thus, it is a useful tool in measuring the degree of sedation over time. Chernik et al. [18] found that depth of anesthesia is best assessed clinically and with OAA/S scale, which is reliable and valid.

Rampil et al. [24] evaluated the bispectral electroencephalogram (EEG) index during administration of N 2 O at several concentrations (10, 20, 30, 40, 50%) on 13 healthy adult volunteers. The spectral content of the EEG changed during administration of N 2 O, but not significantly affecting the index. No significant change in OAA/S scale was detected during the study. In the present study, 65% of the children were mildly sedated, 25% showed moderate sedation and 10% remained alert. The difference in the OAA/S score in the 2 studies could be in the difference in the age group of the subjects and OAA/S score that was recorded at different concentrations of N 2 O.

Pulse-oximetry was used to measure the oxygen saturation and the heart rate. No significant difference was found in either of the groups. All patients had oxygen saturation levels of more than 92% throughout their treatment. The heart rate reduced from baseline during administration of N 2 O-O 2 and thereafter but was well within the normal clinical range. This may be due to the anxiolytic effect of N 2 O. The heart rate that was within the clinical range in oxygen group may be due to the placebo effect. There was no change in the respiratory rate from baseline recording until the end of the observation period.

Most of the inhalation agents have a tendency to increase respiratory rate but decrease tidal volume and produce a dose-dependent reduction in mean arterial pressure. N 2 O is distinguished from other agents in that it does not reduce net ventilation or produce any change in arterial pressure. [25],[26] In the present study, also there was no much changes in the heart and respiratory rate and oxygen saturation.

No adverse events occurred in our study. The safety of this technique lies in the ability to titrate N 2 O to the desired concentration. N 2 O was delivered in the range of 30-40% for all the children and was adequate for successful completion of the procedure. The main factors that justify the use of N 2 O are its well-defined indications, the rapid onset of action and brief resolution of the effects in addition to the absence to any kind of nephrotoxicity, hepatotoxicity etc. [11],[27]

Many studies focus on the use of N 2 O-O 2 in combination with other agents justifying that the outcome is better. A study by Fukuta et al. [28] found better patient compliance to wear the nasal hood in children who were given N2O/O 2 subsequent to intranasal administration of midazolam. But in the present study, all the children accepted the hood after appropriate nonpharmacological behavior management technique.

It is also convinced in the present study that over 90% of children undergoing dental treatment under local anesthesia was completed successfully under sedation with N 2 O-O 2 sedation administered at 30-40%. N 2 O alone in suitable dose is found to be well-tolerated by pediatric patients, making it possible to perform treatments with mild anesthesia. [27] Higher dose of N 2 O may produce deep sedation or general anesthesia like effect [10],[11]

In the present study, assessment was done only during administering local anesthesia. The observation period could have been extended for the entire procedure to obtain a more consistent readings.

Reasons - why this paper is important to pediatric dentists.

  • Nitrous oxide-oxygen inhalation sedation when used alone also produces mild to moderate sedation to complete dental procedures in anxious children with all the vital signs within normal physiologic limits.
  • Pain experienced by children receiving N 2 O-O 2 sedation was significantly lower than children who received O 2 alone during the administration of local anesthesia with significant improvement in the behavior of children during and after the procedure.
  • Since the treatment scheduled for the appointment was completed in all children, the efficacy of N 2 O/O 2 or O 2 has been proven.

   References Top

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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]

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