The Suitability of Propofol Compared with Urethane for Anesthesia during Urodynamic Studies in Rats

Abstract

Urethane anesthesia preserves many reflex functions and is often the preferred anesthetic for urodynamic studies in rats. Because of the toxicity profile of urethane, its use as an anesthetic typically is limited to acute and terminal investigations. Alternative anesthetic options are needed for longitudinal studies of micturition reflexes in rats. In this study, we evaluated propofol anesthesia administered at constant rate infusion at different planes of anesthesia in rats for combined cystometrography and external urethral sphincter (EUS) EMG in rats. No reflex micturition was noted after rats received 100%, 80%, or 60% of a previously reported anesthetic dose of propofol. At 40% of the standard propofol dose, a subset of rats showed reflex voiding, with bladder contractions and associated EUS EMG activity. In contrast, urethane anesthesia at a surgical plane allowed for reflex voiding with bladder contractions and EUS activation. Latency to leaking or voiding was longer in rats under propofol anesthesia than in those under urethane anesthesia. In a subset of rats with reflex voiding under propofol anesthesia, voiding efficiency was decreased compared with that of rats anesthetized with urethane. We conclude that propofol anesthesia suppresses micturition reflexes in rats more efficiently than did urethane. Propofol is a suitable anesthetic for longitudinal studies in rats, but its use for urodynamic evaluations is limited in these animals due to its marked suppression of both bladder contractions and EUS EMG activation.

Figure 1.

Representative examples of cystometrographic and EUS EMG activity in a rat under urethane anesthesia. Two consequent voiding contractions (A, upper tracing) by saline infusion associated with EUS EMG activity (A, lower tracing) are shown. A more rapid time scale indicates the expulsion time (ET) during voiding (B, upper tracing) as well as the tonic and bursting EUS activity (B, lower tracing); RP, resting pressure: PT, pressure threshold; ET, expulsion time; ICI, intercontraction interval; CD, contraction duration; max IVP, maximal intravesical pressure.

Figure 2.

Representative examples of micturition reflexes in urethane and propofol groups. The graphs show the cystometrograms from 6 experimental conditions during the infusion of saline into the bladder of rats anesthetized by using (A) urethane, (B)100% propofol dose, (C) 80% propofol dose, (D) 60% propofol dose, (E) 40% propofol without voiding contractions, and (F) 40% propofol dose with voiding contractions. Note the onset of reflex voiding in the urethane group (A) and in the subgroup of rats under 40% propofol dose with voiding contractions (F); the other groups lack reflex micturition but instead show a bladder leak response at a later time of onset (B through E).

Figure 3.

Statistical analysis of the (A) latency to the first void or leak and (B) voiding efficiency (B) for the urethane and propofol groups. Value differs significantly (*, P < 0.05; †, P < 0.001) between groups.