The effects of nitrous oxide on behavior and physiological parameters during conscious sedation with a moderate dose of chloral hydrate and hydroxyzine.

The purpose of this study was to determine differences in heart rate (HR), blood pressure (BP), peripheral oxygen saturation (pO2), expired CO2 (CO2), and behavior (using two scales) comparing nitrous oxide/oxygen (N2O) with oxygen (O2) alone in 20 children (mean age 45 +/- 5.1 months) sedated with chloral hydrate (CH) and hydroxyzine in a double-blind crossover design. Administration of CH (40 mg/kg) and hydroxyzine (2 mg/kg) was held constant for each patient visit; however, N2O (50%) was administered during one visit and O2 (100%) at the other in a randomly determined manner. Physiologic and behavioral parameters were collected during eight specific procedural events (e.g., administration of local anesthesia). Data were analyzed with a repeated-measures ANOVA, one-way ANOVA, t-test, Kruskal Wallis ANOVA, and descriptive statistics. There was no statistically significant difference in any physiologic or behavioral parameter as a function of inhalation agent. However, significant differences were found for certain physiological parameters (i.e., HR [F = 5.41, P < 0.001], pO2 [F = 6.04, P < 0.001], and CO2 [F = 2.33, P < 0.027]) and all behavioral measures (% crying [F = 2.82, P < 0.008], % quiet [F = 5.38, P < 0.001], % movement [F = 3.88, P < 0.001], and % struggle [F = 2.83, P < 0.007]) of one scale (Ohio State University Behavioral Rating Scale [OSUBRS]) as a function of procedural events. Although no statistically significant differences were attributable to inhalation agent, evidence suggests that N2O resulted in less crying and struggling and more quiet behaviors than O2. Significant correlations existed between sub-categories of the two behavioral rating scales, suggesting some association between the scales. One may conclude from the results of this study that moderate doses of CH and hydroxyzine in combination with nitrous oxide are not associated with any significant potentiation effects on physiologic parameters compared with the same oral agents with oxygen alone. Certain procedural events (e.g., administration of local anesthesia) do result in patient responses that affect specific behaviors and physiology. Although the effects of N2O may not be statistically significant, generally it produces an attenuation in physiological and behavioral responses as measured under the conditions of this study.