Ch 7 - SCI: Medical Complications Flashcards
What are SCI T6 and above patients at risk of?
Autonomic dysreflexia
Orthostatic hynpotension
What are SCI T8 and above patients at risk of?
Cannot regulate and maintain normal body temperature
What is orthostatic hypotension?
State of transient reflex depression caused by a lack of sympathetic outflow and triggered by tilting the patient upright >60°
What are levels T1-L2 sympathetics responsible for?
Tachycardia
Vasoconstriction
Increased arterial pressure.
What are levels T1-T7 sympathetics responsible for?
Heart and blood vessels supplied by T1–T7
Which receptors sense decrease in BP?
Aortic and carotid baroreceptors
What blood pressure management pathway is blocked following SCI?
Efferent pathway to increase sympathetic outflow
What are non-pharmaceutical managements of hypotension?
– Trendelenburg/ recliner WC
– Elastic stocking/ abd binder/ace wrap LE
– Tilt table
– Fluid resuscitation
What are pharmaceutical managements of hypotension?
■ Na tabs 1 gram QID
■ Midodrine (ProAmatine) (α-1 adrenergic agonist): 2.5 to 10 mg TID
■ Florinef® (mineralocorticoid): 0.05 to 0.1 mg daily
What is Autonomic Dysreflexia?
Syndrome of massive imbalanced reflex sympathetic discharge in patients with SCI above the splanchnic outflow (T5–L2)
What does a noxious stimulus cause in Autonomic Dysreflexia?
Increases sympathetic reflex spinal release
When does Autonomic Dysreflexia appear?
2 to 4 weeks post-injury
W/in 1st year in >90% of cases
Classically in complete SCI
What are the MCC of Autonomic Dysreflexia?
– Bladder: Blocked catheter/distended bladder – Bowel: Fecal impaction – Abd emergency (appendicitis, cholecystis, pancreatitis) – Labor – PUs – Fractures – Ingrown toenails – Orgasm – Urinary tract infections – Epididymitis – Bladder stones – Gastric ulcers
What are signs of Autonomic Dysreflexia?
– Headache – Sweating/ flushing above level of SCI – Elevated BP – Piloerection – Pupillary constriction – Sinus congestion
What is initial treatment for Autonomic Dysreflexia?
- Sit upright, loosen clothing and devices
- Identify and remove noxious stimulus
- Monitor BP ~2 to 5 min during the episode and monitor for symptoms for at least 2 hours after resolution
- Meds if BP is >150 mmHg, unable to find source quickly and prior to checking for fecal impaction
What are pharmacologic treatments for Autonomic Dysreflexia?
■ Nitropaste: ½ to 2 inches, and removed once noxious stimulus is corrected
■ Clonidine: 0.3 to 0.4 mg
■ Procardia® 10 mg chew and swallow
What are pharmacologic treatments for Autonomic Dysreflexia in the ICU setting?
■ Diazoxide
■ Nitroprusside
■ Hydralazine
■ Labetalol
What is recommended during delivery in patients with T6 or above SCI?
Spinal anesthesia
What are complications of Autonomic Dysreflexia?
■ Retinal hemorrhage ■ CVA/SAH ■ Seizure ■ MI ■ Death
What does the Corticopontine mesencephalic nuclei in the frontal lobe control?
– Inhibits PNS sacral micturition center
– Allows bladder storage
What does the Pontine mesencephalic nuclei in the Pons control?
– Coordinates bladder contraction and sphincter relaxation
– Loss of control from this center can result in detrusor sphincter dyssynergia
What does the Pelvic and pudendal nuclei: Sacral micturition control?
– Integrate stimuli from cephalic centers
– Mediate PNS sacral (S2–S4) micturition reflex
What does the Motor cortex to pudendal nucleus control?
Voluntary control (contraction/inhibition) of external urethral sphincter
Where is the origin of PNS efferents for voiding control?
Detrusor nucleus in intermediolateral gray matter at S2–S4 levels
Where is the course of PNS efferents for voiding control?
Travel through pelvic nerves to PNS receptors of detrusor muscle
What is the function of PNS efferents for voiding control?
Stimulation of cholinergic receptors causes bladder contraction and emptying
Where is the origin of SNS efferents for voiding control?
Intermediolateral gray matter from T11–L2
Where is the course of SNS efferents for voiding control?
Travel through hypogastric nerves to alpha (α-1) and beta (β-2) adrenergic receptors within the bladder and urethra
What is the function of SNS efferents for voiding control?
Stim of β-2 adrenergic rec w/in bladder body causes smooth muscle relaxation (compliance) + stim of α-1 adrenergic rec w/in bladder base; prostatic urethra causes smooth muscle contraction (increase outlet resistance) = urine storage
Where is the origin of somatic efferents for voiding control?
Pudendal nucleus of sacral segments (S2–S4)
Where is the course of somatic efferents for voiding control?
Travel through pudendal nerve to innervate striated muscle of external urethral sphincter
What is the function of somatic efferents for voiding control?
Voluntary contraction of external urethral sphincter prevents leakage or emptying
Where is the origin of afferent fibers for voiding control?
Detrusor muscle stretch receptors, external anal and urethral sphincters, perineum, genitalia
Where is the course of afferent fibers for voiding control?
Travel through the pelvic and pudendal nerves to the sacral cord
What is the function of afferent fibers for voiding control?
Myelinated A-delta (A-δ) fibers respond to bladder distention stim PNS emptying of bladder and unmyelinated C-fibers are silent
What innervates the internal urethral sphincter?
T11–L2 hypogastric nerve (sympathetic)
Large number of α-adrenergic receptors
What is the function of the internal urethral sphincter?
– Contracts sphincter for storage
– Smooth muscle, involuntary
What innervates the external urethral sphincter?
Innervated by pudendal nerve (S2–S4)
What is the function of the external urethral sphincter?
– Prevents leakage or emptying
– Skeletal muscle, voluntary
Where are Cholinergic muscarinic receptors located?
Located within the bladder wall, trigone, bladder neck, and urethra
Where are b-2 adrenergic receptors located?
Concentrated in the body of the bladder, also some in bladder neck
What happens when Norepinephrine (NE) binds to b-2 adrenergic receptors?
Cause relaxation to pormote bladder expansion and promote storage
Where are a-1 adrenergic receptors located?
Located within the base of the bladder and prostatic urethra
What happens when Norepinephrine (NE) binds to a-1 adrenergic receptors?
Cause contraction of internal sphincter to prommote storage
What does the bladder wall lack?
Baroreceptors
What happens when Ach binds to muscarinic receptors?
Stimulates cholinergic receptors in the bladder wall, trigone, neck, and urethra, causing bladder contraction and emptying