|Year : 2016 | Volume
| Issue : 3 | Page : 217-222
Comparative evaluation of diffusion hypoxia and psychomotor skills with or without postsedation oxygenation following administration of nitrous oxide in children undergoing dental procedures: A clinical study
Vineet Inder Singh Khinda1, Parvesh Bhuria1, Paramjit Khinda2, Shiminder Kallar1, Gurlal Singh Brar1
1 Department of Pedodontics and Preventive Dentistry, Genesis Institute of Dental Sciences and Research, Ferozepur, Punjab, India
2 Department of Periodontology and Oral Implantology, Genesis Institute of Dental Sciences and Research, Ferozepur, Punjab, India
|Date of Web Publication||25-Jul-2016|
Vineet Inder Singh Khinda
Department of Pedodontics and Preventive Dentistry, Genesis Institute of Dental Sciences and Research, Ferozepur, Punjab
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Diffusion hypoxia is the most serious potential complication associated with nitrous oxide. It occurs during the recovery period. Hence, administration of 100% oxygen is mandatory as suggested by many authors. Aim: The aim of this study is to evaluate the occurrence/nonoccurrence of diffusion hypoxia in two groups of patients undergoing routine dental treatment under nitrous oxide sedation when one group is subjected to 7 min of postsedation oxygenation and the second group of the patients is made to breathe room air for the similar period. Materials and Methods: A total of sixty patients within the age group of 7–10 years requiring invasive dental procedures were randomly divided into two groups of 30 each using chit method. In the control group, patients were administered 100% oxygen postsedation, whereas, in the study group, patients were made to breathe room air postsedation. Various parameters (pulse rate, respiratory rate, blood pressure, and oxygen saturation [SpO2]) were recorded pre- and post-operatively. Data were collected and then sent for statistical analysis. Results: The mean postoperative SpO2 at measurement times 1, 3, 5, and 7 min in both the groups was higher than the mean preoperative SpO2. This increase was statistically significant. No significant difference was found between the Trieger test scores. Conclusion: This study proves that clinical occurrence of diffusion hypoxia is not possible while following the routine procedure of nitrous oxide sedation.
Keywords: Diffusion hypoxia, nitrous oxide inhalation sedation, Trieger test
|How to cite this article:|
Khinda VI, Bhuria P, Khinda P, Kallar S, Brar GS. Comparative evaluation of diffusion hypoxia and psychomotor skills with or without postsedation oxygenation following administration of nitrous oxide in children undergoing dental procedures: A clinical study. J Indian Soc Pedod Prev Dent 2016;34:217-22
|How to cite this URL:|
Khinda VI, Bhuria P, Khinda P, Kallar S, Brar GS. Comparative evaluation of diffusion hypoxia and psychomotor skills with or without postsedation oxygenation following administration of nitrous oxide in children undergoing dental procedures: A clinical study. J Indian Soc Pedod Prev Dent [serial online] 2016 [cited 2021 Jan 19];34:217-22. Available from: https://www.jisppd.com/text.asp?2016/34/3/217/186751
| Introduction|| |
Nitrous oxide inhalation sedation is the most widely used pharmacological modality for the management of fear and anxiety. It has excellent safety record with no serious complications. Diffusion hypoxia also known as fink effect is one complication that has been associated in the literature of past with inhalation sedation and general anesthesia. It occurs during the recovery period when there is rapid nitrous oxide washout. Nitrous oxide has low blood: Gas solubility coefficient, therefore it diffuses out of the blood in large volumes which dilutes oxygen in lung alveoli and reducing alveolar oxygen tension, which then produces hypoxia. This hypoxia may be manifested as clinical signs and symptoms of systemic hypoxia. Literature review shows that the occurrence of diffusion hypoxia alone with nitrous oxide is only possible at very high concentrations (>70%)., Furthermore, the chances of this complication increase when nitrous oxide is combined with other drugs. Routine administration of nitrous oxide in pediatric dentistry does not employ polypharmacy, and moreover, higher concentrations are not used. Hence, it is worth an investigation whether the routine practice of making the patient undergo few minutes of postsedation oxygenation is required or not.
Postoperative vital signs (blood pressure, pulse rate, oxygen saturation [SpO2], and respiratory rate) are an objective measure of recovery. Pulse oximetry is a noninvasive method for monitoring SpO2. SpO2 is a gold standard in the nitrous oxide inhalation sedation to keep a check on patient sinking into diffusion hypoxia. During sedation procedure, it allows the operator to control the saturation levels.
Physiological and psychomotor well-being has been used as the criteria for recovery from sedation. Earlier studies recommended pre- and post-operative drawing/sketching tests to determine visual-motor coordination and recovery. Jastak and Orendurff investigated psychomotor recovery by using a driving simulation test. Other psychomotor tests are hand-eye coordination test, straight line walk, tweezer dexterity test, a matching-color pegboard, etc., Letourneau and Denis stated that Trieger test is a reliable test. Trieger test is a simple, direct, self-administered, and objective test to measure recovery time from ambulatory anesthesia. In general, emergence (recovery) is a mirror image of induction. Rapid recovery of the patient following sedation cessation is a stated advantage.
This study was undertaken to comparatively evaluate diffusion hypoxia and psychomotor skills with or without postsedation oxygenation following administration of nitrous oxide in children undergoing dental procedures.
| Materials and Methods|| |
The armamentarium comprised continuous flow type conscious sedation unit (World Wide Sedation, Unicorn DentMart Ltd.), a finger pulse oximeter (Oxee Check ™, Romsons, SN-113026301212, Model-MD300C26) [Figure 1] and [Figure 2], and Trieger Dot Test cards.
Totally 60 children aged between 7 and 10 years were included in the study. They were randomly divided into two groups of 30 each using chit method. A prior consent was taken, and parents were informed regarding the merits/demerits of inhalation sedation. Inclusion criteria for the subjects consisted of the absence of any contraindication to nitrous oxide inhalation sedation, children within the ages 7–10 years, patients requiring at least 55% nitrous oxide for adequate sedation, willingness to participate and healthy physical status (ASA I and II). A thorough health history of the subjects was recorded. The subjects were made to complete a preoperative, written psychomotor skill test (Trieger Dot Test, [Figure 3]). Preoperative SpO2, respiratory rate, pulse rate, and blood pressure were recorded for each subject.
The unit was prepared by opening both O2 and N2O cylinder. The patient was made to lie on the dental chair in a comfortable supine position. A pulse oximeter was attached to the subject's finger to record the SpO2 and pulse. Exhalation tubes of the scavenging hood were connected to the vacuum system, and the scavenger was switched on.
Calculation of the minute volume is the first step and was achieved in the following manner. The flow of O2 was started at 5 L/min, the nasal hood was placed over the patient's nose, and the patient was reminded to breathe through the nose [Figure 4]. The hoses of hood were wrapped around the headrest and secured in place by adjusting the slip ring. The patient was asked about the ease/comfort of breathing. In all the sixty patients, the flow of 5 L/min was found to be adequate and was finalized as the minute volume. The patient was allowed to breathe 100% O2 for 2 min as a 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 every 20 s till it reached 2.5 L/min. A similar decrease of 0.5 L/min of O2 was done as part of titration. A final addition of 0.25 L of nitrous oxide was carried out taking the flow to 2.75 L/min along with a similar decrease in the flow rate of 0.25 L/min of O2 thus maintaining the minute volume constant at 5 L/min [Figure 5]. This accounted for 55% of nitrous oxide and 45% of oxygen. The percentage of 55% of nitrous oxide was not exceeded in this study. This flow of gases was maintained for few minutes. Once adequate sedation was achieved the required clinical procedures were carried out.
|Figure 5: Titration to reach the final concentration of 55% nitrous oxide oxygen saturation at 1, 3, 5 and 7 min postsedation|
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In Group A (control group), patients were made to breathe 100% oxygen for 7 min after the completion of the treatment phase. In Group B (study group), patients were made to breathe room air after the completion of the treatment phase. SpO2 was recorded at the end of 1, 3, 5, and 7 min in both the groups [Figure 6]. All the subjects were made to complete a postoperative Trieger test [Figure 7] again to evaluate psychomotor skills. Mean length for the operative procedure was 33.16 min for the control group and 28.00 min for the study group.2
| Results|| |
Pre- and post-sedation SpO2 values were compared between groups using Student's nonpaired t-test, P < 0.05 significance [Table 1] and [Graph 1 [Additional file 1]]. At no time, did any subject experience clinical hypoxia as assessed by pulse oximetry because the postsedation mean SpO2 was higher than mean pre-SpO2 at measurement time 1, 3, 5, and 7 min after the cessation of the flow of nitrous oxide and oxygen in both the groups. Postsedation SpO2 was significantly higher in the control group than study group at measurement time 1, 3, 5, and 7 min after the cessation of the flow of nitrous oxide and oxygen (P < 0.05). It was due to the reason that 100% oxygen was given in the control group. There were no clinically significant changes in pulse rate, blood pressure, and respiratory rate in any of the subjects at any time.
In the control group, there was a significant difference between the presedation SpO2 values when compared with the postsedation SpO2 values at 1, 3, 5, and 7 min, respectively, in the groups using Student's paired t-test (P < 0.05). This was because of the 100% oxygen given to the patient postsedation. Similarly, in the study group, there was a significant difference between the presedation SpO2 values when compared with the postsedation SpO2 values at 1, 3, 5, and 7 min, respectively, in the groups using Student's paired t-test, P < 0.05 significance. This was because the patients were being administered a mixture of 55% N2O and 45% O2. Thus, the body stores were saturated with excess oxygen. Results showed that diffusion hypoxia did not occur even if the patients were made to inhale room air postsedation.
Patient's recovery was assessed by psychomotor skill analysis test (Trieger test). A score of 2 was given for each missed dot. [Table 2],[Graph 2 [Additional file 2]] show the comparison of pre- and post-operative scores between the two groups and within the groups. There was no significant difference between the preoperative scores of two groups, P = 0.244 (P > 0.05). Similarly, there was no significant difference between the postoperative scores of two groups, P = 0.675 (P > 0.05). Pre- and post-operative scores were compared using Wilcoxon signed ranks test and no significant difference was found, P = 0.340 and 0.303 for control and study group, respectively (P > 0.05). Hence, the patient's recovery was normal in both the groups.
| Discussion|| |
Diffusion hypoxia is one of the most serious complications that can occur after nitrous oxide inhalation sedation. Diffusion hypoxia can occur with the administration of inadequate amounts of oxygen during or immediately after N2O anesthesia. The Fink effect, also known as “diffusion anoxia,” “diffusion hypoxia,” or the “third gas effect,” is a factor that influences the partial pressure of oxygen (PO2) within the alveolus. It is associated with nitrous oxide sedation because of its high blood: Gas coefficient (0.46), which is 30 times greater than nitrogen (0.014). When inhalation of high concentrations of nitrous oxide is discontinued, the high partial pressure in blood transfers nitrous oxide to the alveoli rapidly. This dilutes the PO2 in the alveoli and may lead to hypoxemia. However, this concern is more theoretical than clinical. Hypoxemia is significant for only a matter of minutes and has been documented only when high concentrations (70%) have been delivered by full mask or by the endotracheal tube. Even though machine settings may indicate up to 70% nitrous oxide, the actual concentration delivered to alveoli is unlikely to exceed 30–50%. Dead space, mouth breathing, and the ventilatory status of the patient are some of the factors that could account for such discrepancy.
In the control group, there was a slightly significant increase in the postsedation SpO2. The explanation for this is that the patient was breathing 100% oxygen postsedation and thus, the postsedation SpO2 at measurement times 1, 3, 5, and 7 min was higher than preoperative SpO2. Furthermore, the postoperative SpO2 was slightly greater in the study group because 45% oxygen was delivered to the patient during the procedure which is more than physiological atmospheric oxygen (21%). Diffusion hypoxemia of any degree can be seen only if a patient is breathing a gas mixture containing no more than 21% oxygen. Cheney studied 18 healthy, spontaneously breathing patients during the change from breathing 79% nitrous oxide to 21% oxygen to breathing air and observed SaO2 values above 90 and usually above 93%. It was concluded that anoxia was not a clinically significant phenomenon in healthy patients who maintained normal ventilation. Selim et al. studied the relationship of ventilation to diffusion hypoxia and concluded that diffusion hypoxia is clinically insignificant when ventilation is adequate, and PaO2 is at least 100 mm of Hg before N2O washout. Quarnstrom et al. also supported the results of this study that postsedation 3–5 min 100% oxygen is not necessary. Frumin and Edelist found that alveolar dilution caused by N2O diffusion in healthy patients produced clinically insignificant changes in SpO2, concluded that diffusion hypoxia did not occur clinically.
Dunn-Russell et al., Jeske et al. conducted similar studies and concluded that breathing room air postoperatively made no difference in SpO2 pre- and post-operatively. Various studies have advocated the use of 100% oxygen postsedation for 3–5 min to prevent diffusion hypoxia. Hypoxia attributed to N2O elimination and diffusion may not be clinically significant for healthy pediatric dental patients, whether they receive room air or oxygen postoperatively. There was no significant difference in the blood pressure, respiratory rate, and pulse rate between the two groups as well as within the group.
In this study, Trieger test was used to evaluate psychomotor skills to assess postsedation recovery of the patients. There was no significant difference observed between the pre- and post-operative scores of Trieger test between the groups as well as within the group (P > 0.05). Jeske et al. conducted a similar study found no significant difference between the pre- and post-operative scores of Trieger test between the groups as well as within the group (P > 0.05).
The limitations of this study were that (a) Although, the patients can be taken to concentrations of nitrous oxide as high as 65–70% if it is deemed necessary and is considered to be safe, but 55% nitrous oxide mark was not crossed in this study so as to standardize the sedation levels being experienced by the subjects in the two groups. Further studies are recommended at a higher concentration; (b) SpO2 values were used to measure SpO2 which was not confirmed by SaO2. SaO2 values have higher accuracy, but it being an invasive procedure with in-line monitoring was not preferred in pediatric patients for this study. SpO2 values were instead chosen to record SpO2 for instant and convenient measurements. However, this is consistent with reports from the medical literature.
| Conclusion|| |
The results of this study suggest that diffusion hypoxia does not occur irrespective of the fact that the patients are administered 100% oxygen postsedation or not. Mean postsedation SpO2 was higher in both control and study group at all the measurement times. This study further advocates and underlines the safety of nitrous oxide inhalation sedation. The investigation stresses on the fact that clinical occurrence of diffusion hypoxia is not possible within the parameters of moderate sedation employing nitrous oxide and oxygen for providing conscious sedation relative analgesia. It can be safely postulated that even in an unlikely scenario of oxygen supplies depleting during the course or toward the end phase of a sedation appointment, the patients will not slip into diffusion hypoxia even if they are returned to breathing room air instead of the routine of few minutes of 100% oxygen. The results of the present study go a long way in corroborating the well-documented safety aspects of the technique of nitrous oxide – oxygen inhalation sedation analgesia. The conclusion drawn from this study encourage the authors to advocate the greater usage of nitrous oxide-oxygen conscious sedation analgesia for behavior modification and pain control in place of more invasive and relatively unsafe modalities such as intravenous/intramuscular/oral routes of sedation and general anesthesia.
Why this research is important to pediatric dentists?
- This research proves that diffusion hypoxia is not a clinically possible while following the routine procedure of nitrous oxide sedation
- This research further supports the well-documented safety of nitrous oxide inhalation sedation
- Results of the present study encourage the pediatric dentists to use nitrous oxide for the management of fear and anxiety in a pediatric patient.
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Conflicts of interest
There are no conflicts of interest.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/ their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2]