FIGURE 5.

Monitoring of vital signs during long-term anesthesia and imaging. An oximeter probe attached to the thigh of the mouse is used to measure (A) the heart rate (beats per minute, bpm), (B) the arterial oxygen saturation of the blood (percent, %), and (C) the distension of blood vessels caused by the pulse and the breathing (micrometers, μm). Traces are 3-min long, originating from a single 9-h image session. (A) Under stable anesthesia (0.9%–1.1% isoflurane), the heart rate is steady and typically between 300 bpm and 450 bpm. With acute excess anesthesia, 1.25%–1.5% isoflurane, the heart rate lowers and becomes erratic. Recovery is achieved by reducing isoflurane concentration to 0.9%, and the heart rate stabilizes. At chronic excess anesthesia levels (2.5% isoflurane), the heart rate declines to critically low levels (yellow, <210 bpm). (B) Oxygen saturation stays at ~97% at anesthesia levels of 0.9%–1.25% isoflurane. It falls toward 90%–95% at 1.5% isoflurane and is slower to recover than heart rate when isoflurane is restored to 0.9%. At chronically high anesthesia levels, oxygen saturation dips to <90%. (C) Under stable anesthesia, the vascular distension caused by the pulse is relatively constant and is of higher amplitude than the vascular distension caused by breathing. At 1.25% isoflurane, the breath distension increases in amplitude, and, at 1.5% isoflurane, the mouse begins gasping, and the distension caused by breathing becomes irregular and exceeds pulse distension. At 0.9% isoflurane, the mouse recovers. Chronic exposure to excess isoflurane (2.5% isoflurane) results in a decline in the distension caused by pulse and breathing. (For color figure, see doi: 10.1101/pdb.top97 online at www.cshprotocols.org.)