Autonomic nervous system
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AUTONOMIC NERVOUS SYSTEM. DR. MUNISHA AGARWAL DR. SAURABH TANEJA. www.anaesthesia.co.in [email protected] PARASYMPATHETIC Long preganglionic fibers Short postganglionic fibers Function : Conserves energy 1 preganglionic synapses with 1 postganglionic fibre . SYMPATHETIC

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AUTONOMIC NERVOUS SYSTEM

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Autonomic nervous system

AUTONOMIC NERVOUS SYSTEM

DR. MUNISHA AGARWAL

DR. SAURABH TANEJA

www.anaesthesia.co.in

[email protected]


Symp parasymp ns

PARASYMPATHETIC

Long preganglionic fibers

Short postganglionic fibers

Function : Conserves energy

1 preganglionic synapses with 1 postganglionic fibre

SYMPATHETIC

short preganglionic fibers

long post ganglionic fibers

Function : fight/ flight response

one preganglionic synapses with many postganglionic fibres

SYMP. & PARASYMP. NS.


Symp parasymp ns1

PARASYMPATHETIC

Neurotransmitter : acetylcholine

Both @ preganglionic

& postganglionic

SYMPATHETIC

acetylcholine @ preganglionic &

norepinephrine @ postganglionic except sweat glands & some skeletal muscle blood vessels : norepinephrine

SYMP. & PARASYMP. NS.


Autonomic nervous system

PARASYMPATHETIC

Cranial nerves III, VII, IX, X, bulbar portion of XI , S2,3,4 (craniosacral)

CN III to eye,

CN VII to lacrimal, nasal and submaxillary glands.,

CN IX to parotid glands;

vagus to heart, lungs, oesophagus, stomach, small intestine, liver, gall bladder pancreas & upper part of the uterus

the sacral part innervates distal colon, rectum, bladder, lower portions of uterus & external genitalia

SYMPATHETIC

T1 – L2 (thoracolumbar)

22-24 ganglia on each side

cervical (3),

thoracic (10-12), lumbar (4),

sacral (4,5)

ganglion impar

T1 to head,

T2 to neck & heart,

T3- T6 to chest,

T7-T11 to abdomen, T12-L2 to legs


Effects

EFFECTS


Effects1

EFFECTS


Effects2

EFFECTS


Non invasive tests for assessing the autonomic nervous system

NON INVASIVE TESTS FOR ASSESSING THE AUTONOMIC NERVOUS SYSTEM

  • PARASYMPATHETIC

    Tests involving changes in the heart rate measure injury to parasympathetic system

  • SYMPATHETIC

    After changes in HR, changes occur in the measures of Blood pressure that reflect sympathetic injury.


Heart rate pns

HEART RATE : PNS


Blood pressure sns

BLOOD PRESSURE : SNS


Heart rate pns1

HEART RATE : PNS


Valsalva manouver

VALSALVA MANOUVER

  • checks baroreflex control of HR (parasympathetic) & the BP (adrenergic)

  • PHASES I & II ARE DURING BREATH HOLDING

  • PHASES III & IV AFTER RELEASE

  • The BP & HR responses are mirror images

  • Phase I : brief rise in BP due to increased intrathoracic pressure constricting the great vessels

  • Phase II : gradual fall in BP

    impaired venous return,

    causing decreased stroke volume & decreased BP that reaches a plateau because of peripheral vasoconstriction i.e. increased systemic vascular resistance, with a compensatory tachycardia


Autonomic nervous system

  • Phase III : brief fall in BP because of removal of intrathoracic pressure constricting the great vessels

  • Phase IV : occurs after valsalva is released & patient resumes normal breathing, BP begins to rise.

    After 15-20 sec. there is a rebound overshoot of BP to above baseline

    (due to persistent peripheral arteriolar vasoconstriction and increased cardiac adrenergic tone),

    accompanied by reflex bradycardia, with heart rate below baseline for about 1 min.


Autonomic nervous system

  • Valsava ratio can be calculated & age specific references seen. It is a measure of cardiovagal function.

  • A lack of rebound overshoot of BP during phase IV is an early indicator of autonomic dysfunction.

  • Practical help :

    this rebound overshoot in phase IV, however, can be detected by inflating a cuff to just at SBP and then having the patient valsalva.

    Without changing the cuff pressure, the sounds will disappear during breath holding , and on release the sounds will reappear and can be followed up to detect the rebound overshoot in BP.


Orthostatic hypotension

ORTHOSTATIC HYPOTENSION

  • Defined as a sustained drop in SBP (≥ 20 mm Hg) or DBP (≥ 10 mm Hg) within three minutes of standing.

  • In non neurogenic causes, it is accompanied by a compensatory increase in HR > 15/min.

    an important clue to a neurogenic cause is aggravation or precipitation of symptoms by autonomic stressors (meal, hot bath, exercise, alcohol consumption).

  • allow 20 minute period of supine rest before assessing changes in BP during tilting.


Bladder

BLADDER

  • detrusor muscle innervated by parasympathetic neurons located at S2-S4 level.

  • internal urethral sphincter innervated from T12-L1 level via sympathetic prevertebral plexus and the hypogastric nerve.

  • Normal micturition requires

    intact autonomic nervous system

    spinal pathway

    cerebral inhibition

    control of external sphincter


Lesions

LESIONS

CEREBRAL CORTEX :

  • Loss of inhibition. Bladder tone is normal.

  • Micturition occurs by stretch reflex.

  • Signs & symptoms are frequency, urgency, hesitancy, incontinence. Bladder sensation is normal.

  • There is no residual urine.


Autonomic nervous system

REFLEX NEUROGENIC BLADDER:

  • Occurs with severe myelopathy & extensive brain lesions causing interruption of both the descending autonomic tracts to the bladder & ascending sensory pathways above the sacral segments of the cord.

  • Bladder capacity is small & micturition reflex is reflex & involuntary. Residual urine volume is variable.


Autonomic nervous system

AUTONOMOUS NEUROGENIC BLADDER

  • It is without external innervation.

  • Sensation is absent. There is destruction of parasympathetic supply.

  • no reflex or voluntary control of the bladder. Contractions occur as the result of stimulation of the intrinsic neural plexuses within the wall.

  • Amount of residual urine is large but the bladder capacity is not greatly increased.


Autonomic nervous system

SENSORY PARALYTIC BLADDER

  • Lesions in the posterior root or the posterior root ganglia of the sacral nerves or the posterior columns of the spinal cord.

  • Sensation is absent and there is no desire to void.

  • There may be distension, dribbling, and difficulty both in initiating micturition & emptying the bladder.

  • There is large amount of residual urine.


Autonomic nervous system

MOTOR PARALYTIC BLADDER

  • Motor nerve supply is interrupted.

  • The bladder distends & decompensates but sensation is normal.

  • The residual urine & bladder capacity may vary.


Sexual function

SEXUAL FUNCTION

  • Erection is a parasympathetic function, S2-S4

  • Ejaculation is a sympathetic function, lumbar nerves.

  • Autonomic insufficiency usually causes impotence but pathological exaggeration of sexual reflex may occur as a part of mass reflex which may produce priapism.

  • In autonomic neuropathy, especially from diabetes, retrograde ejaculation (lack of closure of internal vesical sphincter during ejaculation; producing milky white urine ) may procede the development of impotence.


Rectum

RECTUM

  • If sacral segments or pelvic nerves involved; laxity of the sphincters & incontinence may occur

  • Gripping of the gloved finger by the internal sphincter will be absent.

  • Stroking the skin near the external sphincter will not produce reflex contraction

  • Higher spinal or pontine lesions : tonic contraction of the sphincters & result in constipation


Impaired glandular activity

IMPAIRED GLANDULAR ACTIVITY

  • Difficulty in food intake due to decreased salivation

  • Eye irritation due to decreased lacrimation

  • Decreased sweating causing temperature elevation and vasodilation


Sudomtor thermoregulatory function

SUDOMTOR & THERMOREGULATORY FUNCTION

  • Abnormal dryness of skin may be sign

  • Lack of normal moisture in the socks may indicate

  • Localized : peripheral nerve injury

  • Generalized : diffuse dysautonomia

  • Simple bedside test : stroking of the skin with the finger/ pen or spoon

    Smoothly : dry (sympathectomised)

    Irregularly/ unevenly : moist, perspiring skin


Autonomic nervous system

  • Various tests are sympathetic skin response (SSR), Quantitaive sudomotor axon reflex test (QSART), sweat imprint, thermoregulatory sweat test (TST)

  • SSR assesses peripheral sympathetic function by detecting changes in skin resistance in response to sudomotor discharges.

  • TST assesses both the central & peripheral sympathetic components by analyzing the sweating response to rise in body temperatures


Autonomic nervous system

  • QSART assesses the postganglionic sudomotor fibers by measuring the sweat output in response to iontophoresis of acetylcholine into the skin.

  • sweat imprint test quantifies the sweat output by visualizing the imprints sweat droplets make on a plastic or silicon mould.

  • TST combined with a test of postganglionic function can localize the site of process causing anhidrosis.

  • If the postganglionic function test is abnormal, the cause is postganglionic. But if the postganglionic test is normal and the TST is abnormal, the cause is preganglionic


Tear production

TEAR PRODUCTION

  • SCHIRMER TEST :

    placing a strip of sterile filter paper in the lower conjunctival sac and measuring the degree of wetting over 5 minutes.


Pharmacological tests

PHARMACOLOGICAL TESTS

  • Measurement of plasma NE first with patient supine and then after standing for atleast 5 min.

    supine values are decreased in postganglionic disorders (autonomic neuropathy or pure autonomic failure) and may fail to increase in preganglionic or postganglionic disorders (e.g. multiple system atrophy).


Autonomic nervous system

  • To evaluate postganglionic adrenergic function,

    tyramine (releases NE from postganglionic terminals) and phenylephrine (denervation supersensitivity- directly acting α1 agonist) used.

    In a postganlionic lesion, the response to tyramine is reduced & there is excessive response to subthreshold doses of phenylephrine.

  • Other strategies include ganglionic blockade with trimethaphan (greater fall in resulting BP with a preganglionic lesion) or administration of arginine vasopressin (to evaluate afferent central pathways).


Diabetes mellitus

DIABETES MELLITUS

  • Most common cause of autonomic neuropathy

  • Earliest autonomic instability is loss of vagal controlled heart rate variability with deep breathing, decreased peripheral sympathetic tone with increase in blood flow & loss of distal sudomotor function, detected by QSART.

  • In advanced disease, signs of autonomic dysfunction involving cholinergic, noradrenergic & peptidergic systems


Autonomic nervous system

  • CVS : resting tachycardia, orthostatic hypotension (loss of baroreceptor reflex), sudden death,

    ↓ BP @ induction  ↑ need for vasopressors

  • GIT : gastroparesis, nocturnal diarrhea common

    (parasympathetic dysfn  RSI required)

  • GU : Cystopathy (inability to sense full bladder and failure to void completely leading to urinary

    hesitancy, decreased voidingfrequency, incontinence & UTI);

    erectile dysfunction

    (increases with age and duration of disease);

    retrograde ejaculation


Autonomic nervous system

  • SUDOMOTOR : hyperhidrosis in the upper limb & anhidrosis in the lower limbs leading to cracking & increased chances of foot ulcers.

    in diabetic foot; pain & temp senses are lost before loss of touch & vibration senses.

  • METABOLIC : typical signs & symptoms of hypoglycemia may not appear because damage to sympathetic innervation of the adrenal gland can result in lack of epinephrine release

    (hypoglycemia unawareness)


Aging

AGING

  • Orthostatic hypotension common (dec. baroreceptor reflexes)

  • Decreased vagal function & increased NE conc. are balanced by compensatory downregulation of β1 adrenoreceptors

  • Loss of control leading to increase in CHF incidence


Spinal cord transection

SPINAL CORD TRANSECTION

  • In paraplegic patients, small stimuli may evoke exaggerated sympathetic discharges

  • remember the vagus is intact in quadriplegics; may stimulate it by tracheal suctioning & response ↑ by hypoxemia

  • as Symp NS inactive; overactivity of RAA system; so use ACEI cautiously.


Autonomic nervous system

  • bladder or bowel distension  mass reflex

    ↑ BP, ↓ flow to periphery, flushing & sweating above

    the lesion & ↓ HR

  • over sensitive to angiotensin & catecholamines

  • monitor temperature during anesthesia as hypothermia due to inabiity to shiver & cutaneous vasodilation or

    hyperthermia due to loss of normal sweating response, may occur


Autonomic nervous system

THANKS

www.anaesthesia.co.in

[email protected]


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