Physiological Effects, Psychomotor Analysis, Cognition, and Recovery Pattern in Children Undergoing Primary Molar Extractions under Nitrous Oxide Sedation Using Two Different Induction Techniques: A Split-mouth Randomized Controlled Clinical Trial.

Nitrous oxide inhalation sedation (NOIS) has been in use as a tool for pharmacological behavior modification and relative analgesia (RA) for well over 170 years now since its discovery in 1844 by the American Dentist Horace Wells. Advantages include raising of the pain reaction threshold, alteration of both pain sensitivity and pain reaction, reduction of fatigue, and time awareness that helps to handle stress and lengthy appointments. In addition, the most important clinical consequences of Nitrous Oxide (N2O) pharmacokinetics are rapid induction and recovery, reversibility, titrability, and adjustability. The goal of the current investigation was to analyze the safety aspects of nitrous oxide sedation. It was carried out on 25 patients within the age group 7-10 years requiring extractions of two primary molars in each patient. Split-mouth design was followed, with the first extraction done under traditional slow induction while the second extraction was done following the rapid induction technique of NOIS. N2O was studied for its physiological effects, psychomotor analysis was done, cognition and recovery patterns were analyzed utilizing the two different induction techniques. Based on the results obtained, it was found that N2O is a very safe and useful drug that delivers a comfortable patient for dental treatment. How to cite this article: Khinda V, Rao D, Sodhi SPS, et al. Physiological Effects, Psychomotor Analysis, Cognition, and Recovery Pattern in Children Undergoing Primary Molar Extractions under Nitrous Oxide Sedation Using Two Different Induction Techniques: A Split-mouth Randomized Controlled Clinical Trial. Int J Clin Pediatr Dent 2021;14(S-2):S131-S137.

Introduction

Delivery of dental care without causing adverse psychological impact upon the child is a challenge that all pediatric dentists face. One of the primary responsibilities of the dentist is to eliminate the anxiety and fear of the patient. Dental fear and anxiety (DFA) is experienced by many patients, which results in a considerable amount of stress in dentists who are under an obligation to treat such patients.[1,2,3] In patients with severe DFA, the non-pharmacological methods may not work. Pharmacological methodologies which include sedation and general anesthesia (GA) may be the only way forward with such patients.[4]

‘Sedation and analgesia’ is a continuum of states and it ranges from minimal sedation (anxiolysis) through general anesthesia. The states have been defined by the American Dental anesthesia.[5]

In GA the patient's cooperation is not essential for its success. The patient is unconscious, is amnesia is present and there is no response to pain, and it may be the only technique that will prove successful for certain patients, such as medically compromised children. The disadvantages that limit its use are the depression of the vital signs and the protective reflexes (can cause laryngospasm). Also, the patient is unconscious which may not be the ideal requirement in certain situations. For administrating general anesthesia, special equipment, advanced training, and an ‘anesthesia team’ are required. Due to greater risks involved in elective GA procedures, laboratory tests, chest X-rays, and ECG are frequently a requirement. A recovery area must be available for the patient due to the involvement of long recovery times. All these factors increase the effective cost of the procedure done under general anesthesia. Also, it is not recommended for dental work involving routine procedures.

Conscious sedation using a gaseous mixture of nitrous oxide and oxygen (N2O:O2) is one technique that has been overwhelmingly successful in reducing fears, anxiety, and apprehensions associated with dental visit.[6] This is a technique of choice for procedures that require light conscious sedation, irrespective of their length.[7] The pain reaction threshold is increased and fatigue reduced when this technique is used.[7] Pain sensitivity and pain reaction are both altered.[7] Time awareness is reduced. The ability of coping with stress and lengthy appointments is enhanced.[7] These characteristics are a huge help in dealing with pediatric patients.

The advantages of nitrous oxide sedation are manifold. Rapid onset of action and rapid recovery, precise control on the duration of action, ability to quickly reverse an overdose are few of them.[8] N2O:O2 is the only sedation technique in which the clinician can employ judgment as to whether a patient may be discharged unaccompanied.[9] All other sedation procedures demand that the patient be discharged only when accompanied by a responsible adult. Metabolism of N2O is essentially non-existent, and excretion occurs primarily through the lungs at a rapid rate, similar to its rate of absorption. In nutshell, the most important clinical consequences of N2O pharmacokinetics are rapid induction and recovery, reversibility, titrability, and adjustability.[10]

The assessment of recovery from anesthesia deals mostly with the measurement of physiological parameters and their comparison with baseline values, and also the tests of cognition, perceptual proficiency, and psychomotor ability. The postoperative measurements of blood pressure, pulse, respiratory rate, and oxyhemoglobin saturation (SPO2) are good physiological indicators of recovery. In addition, the Number Cancellation Test [Appendix II] is useful test of cognitive pattern, attention, and concentration and is utilized to assess the existence and severity of visual scanning deficits.[11] The Trieger Dot Test [Appendix III], which measures perceptual-motor ability, is a modified version of Design 4 of the Bender-Gestalt Test.[12] This test has been found to be most reliable for psychomotor analysis during recovery from sedation. With the aid of this test, the patient's return to his own preanesthetic baseline becomes more evident and objective.[13]

Nitrous oxide can be administered by two different techniques:

Conventional slow induction

Rapid induction

Conventional slow induction begins with the administration of 100% O2. In children, a flow rate of 4-5 L/min (6-7 L/min in adults) is utilized to settle the minute volume followed by raises in the N2O concentration of 5-10% for every 1-3 minutes.[7] Generally, between 15 and 20% N2O, first cortical signs of sedation are observed, referred to as baseline sedation. Adequate sedation and analgesia obtained for carrying out the dental procedure are usually achieved by administering around 30%-40% N2O.[7] An incremental increase of N2O by 10% for every 3 minutes till a desired level of consciousness is generally considered safe, thus preventing unintended over sedation. However, the amount of time taken, and gases consumed during induction are a liability and can contribute to occupational hazards.

During rapid induction,[7] concentrations of ≥50% N2O are administered directly as a STAT dose in an uncooperative child till he/she gains his/her composure. After the child settles down, N2O concentrations are appropriately adjusted either upward or downward.

The goal of the current investigation was to analyze the safety aspects of nitrous oxide sedation. The results and their interpretation could be a valuable addition to the one already available in literature and help the clinicians gain a better understanding of NOIS.

Materials and Methods

Materials

Armamentarium

A continuous flow type conscious sedation unit (World Wide Sedation, Unicorn Dentmart, Ltd), a finger pulse oximeter (Oxee Check, Romsons, SN-113026 301212, Model-MD300C26), (Fig. 1), Trieger Dot Test cards[7] (Appendix III) and Single Number Cancellation Test Sheets[23,24] (Appendix II).

Fig. 1

Continuous flow sedation unit and pulse oximeter

Patients between ages 7-9 years.

Patients requiring extractions of primary molars.

Patients categorized under Physical status I and II of the American Society of Anesthesiologists (ASA) and Frankl behavior rating scale of 3 and 4.

Patients with upper respiratory tract infections i.e., cough, common cold, sinus problems (acute and chronic), chronic mouth breathing, bronchitis, and tuberculosis.

Patients with compulsive personalities.

Patients having claustrophobia.

Patients who are not willing to undergo nitrous sedation.

A total number of 25 patients within the age group 7-10 years requiring extractions of two primary molars each were selected for the study. Parents/guardians were supplied with an informed consent form[8] [Appendix I] to read, ask, understand and sign. A thorough health history of the subjects was recorded. In the first appointment for extraction, the induction was done by the traditional method of slow induction. Calculation of the minute volume is the first step and was achieved in the following manner. The flow of O2 was started at 5 liters per minute (LPM), the nasal hood was positioned over the nose of the patient (Fig. 2), and the patient was reminded to breathe through nose. The hoses of hood were wrapped around the headrest and secured in place by adjusting the slip ring. Patient was enquired of any discomfort if present while breathing and was made comfortable. In case the patient had difficulty in breathing, the minute volume was be increased by one liter a minute. Patient was allowed to breathe 100% O2 for 2 minutes as part of the preoxygenation procedure after which the titration of nitrous oxide was started. The titration was carried out at a rate of 0.5 mL of N2O every 20 seconds. A similar decrease of 0.5 LPM of O2 was done. The titration continued till adequate sedation was achieved. The flow of gases was maintained for few minutes. At the adequate sedation level, local anesthesia was administered, and the extraction was carried out.

Fig. 2

Placement of nasal hood

When the same patient reported back for the extraction of another primary molar, rapid induction was done with a preadjusted mixture of 50% oxygen and 50% nitrous oxide. In both the groups, the physiological parameter evaluations (pulse and respiratory rates, blood pressure and oxygen saturation) for the patients were recorded in three stages, as follows: 1. P1 (presedation): the patient's baseline physiological parameters when the patient was seated in the chair; 2. P2 (induction): measured after placing the mask and achieving the optimal titration with which to sedate the patient; 3. P3 (end): 5 minutes following the discontinuation of N2O (at the end of postsedation oxygenation).

Psychomotor skill evaluation[7] (Trieger Dot Test) was performed in two stages, 1. M1 (presedation): at the moment the patient was seated in the chair and 2. M2 (end): immediately upon the end of postsedation oxygenation of 5 minutes. Cognitive pattern evaluation including that of attention and concentration was done with help of Letter Cancellation Test.[23,24] This was also carried out in two stages, 1. R1 (presedation): at the moment the patient was seated in the chair and 2. R2 (end): immediately upon the end of postsedation oxygenation of 5 minutes. Clinical record[8] was maintained [Appendix IV].

Results and Discussion

The present study was conducted in the Department of Pedodontics and Preventive Dentistry, Dasmesh Institute of Research and Dental Sciences, Faridkot, India with the goal to assess and compare for the parameters for physiological effects, psychomotor skills, cognition, and recovery pattern post nitrous oxide sedation in 25 children aged between 7 and 9 years.[14,15] The same patients were subjected to two different techniques of induction, slow induction, and rapid induction, during separate appointments.

Statistical Analysis

The results are displayed in frequencies, percentages and mean ± SD. The Paired t -test was used to compare change in continuous variables. The Pearson correlation coefficient was calculated. The p -value < 0.05 was considered significant. Analysis was carried out on IBM SPSS version 23.0. The studied sample consisted of 13 males (52%) and 12 females (48%) with a mean age of 7.96 years (±0.84) Figure 3.

Fig. 3

Distribution of patients according to age and gender

Usually the blood pressure is not influenced by the N2O concentrations commonly used in ambulatory setting.[8] In the present study, a statistically significant difference was found between the systolic blood pressure (SBP) and diastolic blood pressure (DBP) from presedation to induction and end (p = 0.0001) in both the groups. In group A, presedation SBP was 107.04 ± 5.17 which became 102.88 ± 3.20 at induction and 103.80 ± 3.25 at the end. In group B, presedation SBP was 106.60 ± 4.94 which became 102.76 ± 3.30 at induction and 103.40 ± 3.17 at the end. There was significant (p = 0.0001) mean change in SBP from presedation to induction and end in both the groups. DBP in group A was 60.28 ± 3.07 which became 56.92 ± 1.68 at induction and 57.40 ± 1.93 at the end. In group B, the DBP 61.20 ± 5.76 which became 56.84 ± 2.11 at induction and 56.92 ± 3.13 at the end. In both the groups, there was significant (p = 0.0001) mean change in DBP from presedation to induction and end. These findings were in conformity with the results obtained by Eger et al.[23] in their clinical trial involving nitrous oxide. NO does not have any direct effect on the myocardium or voluntary skeletal muscles and this probable decrease in blood pressure is a consequence of relaxation.[8]

Changes in heart rate cannot be directly accredited to N2O.[7] However, as with blood pressure, as the anxiety is reduced, the heart rate may also decrease.[8] Also, as part of the preoxygenation procedure, the patient is made to breathe hundred percent oxygen at the start of the procedure. Inhalation of hundred percent oxygen is connected with a slight fall in both heart rate (3-4 beats/min) and cardiac output (10%-20%).[24] There was significant (p = 0.0001) mean change in pulse rate (PR) from presedation to induction and end in both the groups. In Group A, presedation PR was 98.12 ± 6.05 which became 93.36 ± 3.68 at induction and 94.24 ± 3.82 at the end. In group B presedation PR was 97.44 ± 5.71 which became 92.84 ± 3.57 at induction and 93.44 ± 3.66 at the end Figure 4.

Fig. 4

Comparison of hemodynamic parameters from presedation to induction and end

Bloch M found that the fall of blood pressure, reduction of the heart rate, and loss of muscle tone may be produced by N2O when it is used in surplus of a 50% mixture with O2.[24] In case the blood pressure readings lie within 10 mm Hg (both systolic and diastolic) compared with preoperative readings, these are deemed to be within a range regarded as acceptable.[8] Similarly, postoperative PR within 10 beats and respiration rate (RR) within 5 breaths are acceptable parameters for comparison.[8]

There was significant (p = 0.0001) mean change in RR from presedation to induction and end in both the groups. In group A, the presedation RR was 18.96 ± 0.73 which became 18.00 ± 0.40 at induction and 18.12 ± 0.44 at the end. In group B, the presedation RR was 18.60 ± 0.81 which became 17.68 ± 0.90 at induction and 17.68 ± 0.74 at the end. N2O does not irritate the pulmonary epithelium. Variations in RR or depth are possibly a result of the reduction in anxiety due to sedation (slower, deeper) or as the excitement stage approaches (Guedel anesthesia stage 2) (rapid, shallow); direct action of N2O on the respiratory system is not the reason.[7]

In group A, the presedation SpO2 was 98.80 ± 0.45 which became 99.76 ± 0.43 at induction and 99.08 ± 0.27 at the end. In group A, the presedation SpO2 was 98.78 ± 0.45 which became 99.79 ± 0.43 at induction and 99.06 ± 0.27 at the end. In both the groups, there was significant (p < 0.01) mean change in SpO2 from presedation to induction and end. There was no significant (p > 0.05) difference in SpO2 between group A and group B at both time periods.

Improved oxygen saturation can be attributed to the fact that in addition to N2O, the patient is flooded with a very high concentration of O2 throughout the procedure. This included 100% O2 delivery at the start and termination of procedure. Even at its worst, when the patient is receiving N2O as high as 70%, at 30%, the patient is still receiving O2 which is approximately 1.5 times that of the one which is being breathed through the atmospheric air (20.9%) (Fig. 5).

Fig. 5

Comparison of SpO2 from presedation to induction and end

Trieger Test is a useful measure in ascertaining recovery from sedation. It evaluates patient's motor coordination, it being an objective measurement of the patient's capability to execute fine motor movements. The patient is instructed to carefully join all the dots on a figure. Based on the number of dots that are missed completely, the scoring of the test is decided. Time taken and general quality of the lines are also factored in. Five dots missed preoperatively while seven missed after sedation is not significant.[7,8] There was no significant (p > 0.05) mean change in number of dots missed from presedation to end in both the groups. In group A, the presedation number of dots missed was 3.80 ± 1.29 which became 4.36 ± 1.70 at the end. In group B, the presedation number of dots missed was 3.68 ± 1.10 which became 4.12 ± 1.74 at the end. There was no significant (p > 0.05) mean change in number of dots missed from presedation to end. There was no significant (p > 0.05) different in number of dots missed between group A and group B at both the time periods.[16,19] Positive results obtained for this test of psychomotor analysis during recovery from sedation indicates good recovery of the patients’ perceptual-motor ability and return to their own pre-anesthetic baseline (Fig. 6).

Fig. 6

Comparison of number of dots missed from presedation to end (Trieger Test)

The presence and severity of visual scanning deficits is evaluated with the Single Letter/Number Cancellation Test (SLCT) (Fig. 7). Otherwise known as Visual Perceptual Motor Deficit, Visual Perceptual Disorder affects a child's ability to understand visual information. The score is calculated by subtracting the number of omissions (3's that were not crossed out) from the possible perfect score of 124. Higher scores indicate better performance. Omissions of four or more have been found to be pathological.[20,24] The group A presedation net score was 120.24 ± 2.55 which became 118.04 ± 5.10 at the end. The group B presedation net score was 119.96 ± 2.40 which became 117.24 ± 3.71 at the end. There was no significant (p > 0.05) different in net score between group A and group B at both the time periods. Also, there was no significant (p > 0.05) correlation of number of dots missed with net score at presedation and end.

Fig. 7

Comparison of Net score from presedation to end (Single Number Cancellation Test)

The omissions were found to be within the acceptable limit of 4 dots in both groups. Also, there was absence of statistically significant difference in the net score between the two groups. These parameters indicate that good recovery took place in both the groups regarding the cognitive pattern, attention and concentration and absence of any visual scanning deficits. The discharge was uneventful as well. Only two of the patients missed 8 dots each and were provided with additional O2 for 5 minutes after which the test was repeated and was found satisfactory.

Conclusion

Based on the results obtained in this study, the following conclusions can be drawn:

There was a significant drop between the systolic and diastolic blood pressure, mean heart and respiratory rates from presedation to induction and end. The decreased blood pressure resulting from relaxation lowered anxiety provided by N2O coupled with preoxygenation is of major benefit when providing dental treatment to hypertensive patients. Drop of heart and respiratory rates is attributable to the relaxation and decrease of anxiety that the N2O produces and is not a direct result of the drug itself. The significant improvement in the mean change in SpO2 from presedation to induction and end can be attributed to the fact that in addition to N2O, the patient is flooded with very high concentration of O2 throughout the procedure. Oxygen is a universal drug in majority of emergencies encountered in dental setting and good SpO2 lessens the chances of the patient landing in an emergency during the course of the treatment. The patients had good recovery postsedation. The good of recovery was verified by the positive results of the tests for psychomotor skill evaluation and cognitive pattern evaluation. The discharge was uneventful. Based on the present study, it can be concluded that falling under the class of stress reduction protocol drugs, N2O is a very safe and useful drug that delivers a comfortable patient for dental treatment. At the same time, it impacts the physiological parameters in a positive manner resulting in a quick and uneventful discharge. NOIS has been the mainstay of dental fear and anxiety modification in pediatric patients but still remains underutilized as a tool for pharmacological behavior modification and relative analgesia especially in adult, geriatric and special needs patients. Our patients are now much more informed and demanding compared with those of earlier times. NOIS has the potential of developing into a major tool of patient safety and comfort. Greater research is required in further exploring the potential of NOIS.