Arterial blood sampling in male CD-1 and C57BL/6J mice with 1% isoflurane is similar to awake mice

Figures

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  Fig. 1.. Timeline figure for all protocols. A: arterial blood sampling was conducted in both CD-1 and C57BL/6J male mice under conscious (NO ISO) and 1% isoflurane (1% ISO) conditions in air. Data are presented in Table 1. B: pulse oximetry used to monitor oxygen saturation when the mouse was on the surgical table [2% isoflurane (2% ISO) and 1% ISO] followed by recovery (NO ISO) in air. This measure was to confirm that the NO ISO sample was taken at an appropriate point in recovery. *First 3 min were with 3% isoflurane (3% ISO) for induction of anesthesia; 2% ISO reported value was averaged for the last 5 min of exposure. Data are presented in Fig. 2. C: piezoelectric breathing frequency collected on the surgical table to simulate the ISO blood sampling setup. This experiment was used to quantify breathing frequency during 2 and 1% ISO. *First 3 min were with 3% ISO for induction of anesthesia; 2% ISO reported value was averaged for the last 5 min of exposure. Data are presented in Fig. 3. D: breathing frequency, tidal volume, minute ventilation, and tidal volume/inspiratory time collected with barometric plethysmography. These experiments were a proof of concept to confirm no changes in…

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  Fig. 2.. Arterial blood oxygen saturation in C57BL/6J mice was not different among conscious (NO ISO), 2% isoflurane (2% ISO), and 1% isoflurane (1% ISO) exposures. A: mean pulse oximetry data for C57BL/6J mice (n = 7). Mice were exposed to 3% isoflurane (3% ISO) for induction of anesthesia, then 2% ISO for 27 min followed by 5 min of 1% ISO and monitored for ≤4 h during recovery with air. Five-minute averages of 2 and 1% ISO are represented. After isoflurane (Post ISO) is a 1-h average, using minutes 90–120 from the start of the experiment (60 min of ISO “washout” were allowed before this average). There were no significant differences among 2% ISO, 1% ISO, and Post ISO (1-way ANOVA, P = 0.64). Variance was not different between 1% ISO (5 min) and Post ISO (5 min) arterial blood oxygen saturation (F test, P = 0.18). Five of seven mice showed higher variation with NO ISO (4 h) vs. 1% ISO when comparing individual responses using Levene’s test. Data are represented by means ± SD. B: continuous pulse oximetry data for a single C57BL/6J mouse over a 12,000-s span (200 min). On the tracing, the mouse was exposed to 2% ISO from 0 to 1,095 s and 1% ISO from 1,096 to 1,395 s. At this time, the…

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  Fig. 3.. Breathing frequency for C57BL/6J mice over the course of 2% isoflurane (2% ISO) and a longer duration of 1% isoflurane (1% ISO) exposure displays a plateau in frequency at approximately 10–11 min of 1% ISO. Breathing frequency (breaths/min; BPM) was measured using a Piezoelectric Disk with the surgical setup for C57BL/6J mice. Mice were administered 3 min of 3% ISO for induction and then 27 min of 2% ISO in air through the nose cone followed by 1% ISO. The last 5 min of 2% ISO (n = 6) were averaged, and the duration of 1% ISO was analyzed and averaged for each minute. One animal was only exposed to 10 min of 1% ISO, so a sample size of 5 is represented for minutes 16–20 during 1% ISO. Data are represented by means ± SD.

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  Fig. 4.. Breathing frequency, tidal volume, minute ventilation, and tidal volume/inspiratory time were not different in conscious (NO ISO) and 1% isoflurane (1% ISO) C57BL/6J mice breathing air. Baseline NO ISO and 1% ISO breathing measures for C57BL/6J mice (n = 8/group) are shown. Breathing frequency (A; breaths/min; BPM), tidal volume (B; TV; ml/breath), minute ventilation (C; MV; ml/min), and tidal volume/inspiratory time (D; TV/Ti; ml/s) are shown for NO ISO and 1% ISO mice breathing air. No statistically significant differences in frequency (P = 0.47), TV (P = 0.67), MV (P = 0.83), or TV/Ti (P = 0.69) were found between groups using Student’s t-tests. Data are represented as means ± SD. E: a representative tracing of NO ISO and 1% ISO augmented breaths for a single C57BL/6J mouse. Windows depict the same timeframe for both. Augmented breaths were quantified for each mouse for the 5-min NO ISO baseline and the 5-min 1% ISO exposure. These values were not different (P = 0.33) when using a Student’s t-test, although the typical postsigh apnea was not present in 1% ISO.

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  Fig. 5.. Breathing frequency, tidal volume, and minute ventilation were not different in conscious (NO ISO) and 1% isoflurane (1% ISO) C57BL/6J mice exposed to air, but the pattern of breathing was different between NO ISO and 1% ISO when mice were exposed to hypoxia and hypercapnia. NO ISO and 1% ISO breathing measures across gas exposures. Breathing frequency (A; breaths/min; BPM), tidal volume (B; TV; ml/breath), and minute ventilation (C; MV; ml/min) for gas exposures administered to C57BL/6J mice (n = 8 total) are shown. Final minute of each gas exposure is represented on the graph except for baseline (BL), which is a 5-min average. Representative breathing trace from a single mouse is shown for baseline (D), hypoxia (E), and hypercapnia (F); all scales are the same. Data were analyzed using repeated-measures analysis of variance (ANOVA; BPM, P < 0.001; TV, P = 0.004; MV, P < 0.001). *P < 0.05, NO ISO vs. 1% ISO. Hyper, hypercapnia = 5% CO2-balance air; Hypo, hypoxia = 10% O2-balance N2; P Hyper, posthypercapnia recovery period (air); P Hypo, posthypoxia recovery period (air). Data are represented as means ± SD.