Effects of Analgesic and Anesthetic Medications on Lower Urinary Tract Function

Sammy E. Elsamra, MD; Pamela Ellsworth, MD, FAAP, FACS

Disclosures

Urol Nurs. 2012;32(2):60-67. 

In This Article

Neuraxial Anesthesia

Intrathecal local anesthetics, spinal or epidural administered, are techniques in regional anesthesia that depend on the instillation of nerve-blocking agents with or without analgesics into the epidural space and interrupt afferent and efferent nerve impulses from and to that region's nerve supply. Two main bladder considerations are the inhibition of the afferent and efferent fibers as they enter and exit the spinal cord that are a part of the micturition reflex arc and the inhibition of the upward relaying of these signals to higher centers (PMC) within the spinal cord (Darrah et al., 2009; Kamphuis et al., 1998).

Blockade of afferent nerves results in bladder analgesia, while lack of transmission in efferent fibers causes a detrusor blockade that outlasts motor blockade by as much as several hours. Most patients will be incapable of spontaneous voiding until the sensory level has regressed to the S3 level (Darrah et al., 2009; Kamphuis et al., 1998). The use of longer-acting local anesthetics for spinal injection results in a duration of detrusor blockade sufficient for the bladder volume to significantly exceed preoperative bladder capacity. This over-distention can impair voiding function (Darrah et al., 2009; Kamphuis et al., 1998).

The effect of neuraxial opioids on voiding function may reflect peripheral, spinal, or supraspinal activity. Healthy volunteers given intrathecal morphine or sufentanil (Transdur®) demonstrate impaired bladder contraction within 15 to 60 minutes (Kuipers et al., 2004). The rapid onset suggests that intrathecal opioids affect micturition primarily by inhibiting the spinal reflex responsible for detrusor contraction. A primary lumbarspinal site of action is also supported by the increased incidence of urinary retention associated with lumbar compared with thoracic epidurals (Basse, Werner, & Kehlet, 2000). Intrathecal opioids depress preganglionic neurons in the sacral parasympathetic nucleus, decreasing pelvic nerve activity. They also activate gamma, mu, and delta receptors in the dorsal horn of the spinal cord, inhibiting bladder afferents and decreasing bladder sensation. As a result, bladder capacity and compliance are increased, and the initiation of the micturition reflex is delayed (Dray, 1988).

The liphophilicity of intrathecal opioids affects POUR. Urodynamic studies have demonstrated that hydrophilic opioids, such as morphine, adversely affect bladder function to a greater degree than more lipophilic opioids (such as sufentanil). Enhanced systemic uptake of lipophilic agents limits local activity at the sacral level, which accounts for the difference (Baldini, Bagry, Aprikian, & Carli, 2009; Kuipers et al., 2004). In a prospective double-blinded, randomized, placebo-controlled trial, sufentanil was associated with a lower risk of POUR compared to morphine (Kim et al., 2006).

Many authors have identified an association between spinal anesthesia with long-acting local anesthetics and POUR. Ryan, Adye, Jolly, and Mulroy (1984) demonstrated a decrease in the need for catheterization among patients undergoing herniorrhaphy with lidocaine spinal anesthesia (6%) compared to bupivacaine (Marcaine®, Sensorcaine®) or tetracaine (Ponto caine®, Dicaine®) (30%). In another study, two of 201 ambulatory patients receiving short-acting epidural or spinal anesthesia developed urinary retention (Mulroy, Salinas, Larkin, & Polissar, 2002).

In male patients undergoing inguinal herniorrhaphy, the risk of POUR was greater after spinal anesthesia than epidural anesthesia (Faas et al., 2002). Other factors in addition to local anesthetic dose and duration of action may affect the likelihood of neuraxial anesthesia-related POUR (Darrah et al., 2009). A prospective, randomized trial demonstrated that the use of epidural anesthesia did not increase the incidence of retention after hemorrhoidectomy when intra-operative IV fluids were limited to 200 ml +/- 2 ml/kg/hour of Lactated Ringers (Kau et al., 2003).

Patients undergoing lumbar spinal surgery experience increased rates of POUR when intrathecal local anesthetics are administered with opioids. The addition of fentanyl to spinal anesthesia and the choice of spinal over epidural anesthesia were found to significantly increase time to discharge of ambulatory surgical patents (Mulroy et al., 2002). Local anesthesia does not affect bladder function and is associated with a lower incidence of POUR than neuraxial or general anesthesia. A review of 72 studies found that urinary retention occurred in only 0.37% of patients undergoing hernia repair when local anesthesia was used, as opposed to an incidence of 2.42% with regional anesthesia and 3.0% with general anesthesia (Darrah et al., 2009; Jensen, Mikkelsen, & Kehlet, 2002).

The incidence of POUR after anorectal surgery ranges between 1% and 52% (Lau & Lam, 2004; Zaheer, Reilly, Pemberton, & Ilstrup, 1998). Injury to the pelvic nerves and pain evoked reflex increase in the tone of the internal sphincter and are thought to account for the high incidence of POUR in patients undergoing anorectal surgery (Benoist et al., 1999; Cataldo & Senagore, 1991; Hojo, Vernava, Sugihara, & Katumata, 1991). The duration of spinal and epidural anesthesia can affect how long it takes to void postoperatively. Longer operations may increase the risk of urinary retention because more IV fluids may be administered or higher total doses of opioids and anesthetic agents may be used (Darrah et al., 2009; Wynd, Wallace, & Smith, 1996).

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