Micturition

What are the spinal cord segments that control micturition and are they sympathetic or parasympathetic?

L1-L4 (sympathetic — storage)

S1-S3 (parasympathetic — peeing)

What does hypogastric n do?

1. Stimulates beta receptors = relaxes detrusor m

2. Stimulates alpha receptors = constricts internal urethral sphincter m

What does pelvic n do?

Stimulates via ACh to contract detrusor m

What does S3/pudendal n do?

Somatic control = sensory, motor, contraction of external urethral sphincter m

NORMAL FILLING

Brainstem modulates this activity — pudendal n contracts external sphincter, hypogastric n contacts internal sphincter, pelvic n inhibits detrusor. As the bladder fills, pressure stimulates the sensory of the pelvic n which send info to the hypogastric n.

NORMAL MICTURITION

UMN from pons/medulla signal micturition — inhibition hypogastric and pudendal n, facilitation of pelvic n to contract detrusor

Where is lesion in LMN dysfunction?

S1-S3, which decreases tone of detrusor and external sphincter

LMN dysfunction clinical signs

-urine dribbling

-flaccid bladder

-easy to express bladder but hard to fully get all the pee out

-large and distended bladder

Where is lesion in UMN dysfunction?

Cranial to L7, which causes a lack of nerve inhibition

UMN dysfunction clinical signs

Bladder will be firm and palpable due to inability to coordinate micturition and can be difficult to express

Autonomic dysfunction

-common in the midwest

-dysuria (attempts to urinate but dribbles)

-nonresponsive PLR, ileus, ME, dec anal tone

Alpha antagonists

Phenoxybenzamine & Prazosin

Phenoxybenzamine

-48-72 hr to onset of activity

-relaxes internal sphincter

-side effect = hypotension

Prazosin

-short onset

-same action and side effect as phenoxybenzamine

Striated mm relaxant

Valium: short duration, relaxes external sphincter

Parasympathomimetic (ACh stimulation)

Bethenacol

Bethenacol

-short onset

-stimulates detrusor and external sphincter contraction

-side effects = V/D, salivation

What should you ALWAYS do before starting bethenacol?

Treat with meds to relax urethral sphincter tone

Alpha antagonists

Not really used in neuro cases because you want to make sure that the bladder empties fully in neuro cases.

PPA & estrogen

PPA

Increases alpha activity at internal sphincter and inc tone

Estrogen

Upregulates alpha receptors at NMJ of internal sphincter and inc tone

Common complications to monitor for in patients with bladder dysfunction

-bacterial infection/cystitis

-urine scald

-bladder atony

-bladder rupture

When can bladder atony occur

24 hours of bladder over-distention! This is irreversible

UMN bladder prescription drugs

-alpha antagonists

-striated muscle relaxants

LMN bladder prescription drugs

Parasympathomimetics (supportive care alone?)