2. • Introduction
• Anatomy
• Physiology
• Drugs acting on ANS
• Tests for Autonomic integrity
• ANS Dysfunction
• Anesthesia implications in patients with autonomic dysfunction
• Autonomic reflexes during anesthesia and surgery
3. Introduction
• The autonomic nervous system (ANS) regulates involuntary functions. Anesthesia, surgery,
and critical illness lead to a varied degree of physiological stress that alters the ANS.
• The organization of ANS is on the basis of the reflex arc and it has an afferent limb, efferent
limb, and a central integrating system.
• Neurotransmitters and receptors are an integral part of the ANS.
• Autonomic neuropathy refers to damage to the autonomic nerves and diabetes mellitus is the
most common cause.
• Autonomic neuropathy involves a number of organs and has serious clinical consequences in
the perioperative period and during their management in the critical care unit
4. ANATOMY
Anatomical Division
1. Central Nervous System
2. Peripheral Nervous System
Functional Division
1. Somatic Part
Skin & most Skeletal Muscles
2. Visceral Part
Organ System, Smooth Muscles & Glands
5. ANATOMY
Visceral Part of Nervous System
1. Sensory Nerves
Monitor changes in Viscera
2. Motor Nerves
Smooth Muscle, Cardiac Muscle, Glands
Autonomic Nervous System
6. AUTONOMICNERVOUS SYSTEM
SYMPATHETIC SYSTEM
Associated with Spinal Levels :
• T1 to L2
Controls ‘Fight or Flight’ Response
PARASYMPATHETIC SYSTEM
Associated with :
• Cranial Nerves : III, VII, IX, X
• Spinal Level : S2 to S4
7. AUTONOMICNERVOUS SYSTEM
TWO TYPES OF EFFERENT NEURONS
Preganglionic Neurons
Cell body in Spinal Cord or Brain Stem
Postganglionic Neurons
Cell body in Ganglia
Terminates in effector organs
8. SYMPATHETIC SYSTEM
Preganglionic Neurons
• Nerve fibers extend to Paired ganglia
• Lie immediately lateral to vertebral
column
Postganglionic Neurons
• Runs a long course before innervating
effector organs
24. ASSESSMENT OF AUTONOMIC FUNCTION
A panel of five tests of cardiovascular function was developed to evaluate
autonomic function in diabetic patients
Parasympathetic:
1. HR response to a Valsalva maneuver :
STEP 1) The seated subject blows into a mouthpiece (while maintaining a
pressure of 40 mm Hg) for 15 sec.
• Valsalva ratio: the ratio of the longest R-R interval (which comes shortly after
release of Valsalva maneuver) to the shortest R-R interval (which occurs
during the Valsalva maneuver)
25. ASSESSMENT OF AUTONOMIC FUNCTION
2. HR response to standing : HR is measured as the subject moves from a
resting supine position to standing
A normal tachycardic response is maximal around the 15Th beat after rising.
A relative bradycardia follows that is most marked around the 30th beat after
standing.
• the response to standing is expressed as :
• A 30:15 ratio and is the ratio of the longest R-R interval around the thirtieth
beat to the shortest R-R interval around the fifteenth beat.
26. ASSESSMENT OF AUTONOMIC FUNCTION
• 3. HR response to deep breathing : The subject takes six deep breaths
in 1 min.
• The maximum and minimum heart rates during each cycle are measured.
• the mean of the differences (maximum HR − minimum HR) during three
successive breathing cycles is taken as the maximum-minimum HR.
• Mean difference >15 beats/min.
27. ASSESSMENT OF AUTONOMIC FUNCTION
Sympathetic:
1. BP response to standing: The subject moves from resting supine to
standing, and standing SBP is subtracted from supine SBP
• Difference<10 mm Hg.
2. BP response to sustained handgrip: The subject maintains a handgrip of
30% of the maximum handgrip squeeze for up to 5 min.
• BP is measured every minute, and the initial DBP is subtracted from the DBP
just before release.
• Difference>16 mm Hg
28. ASSESSMENT OF AUTONOMIC FUNCTION
• Tests for sudomotor function
• Thermoregulatoey sweat test
• sympathetic skin response
• Quantitative sudomotor axon reflex test
• Vasomotor Test
• Laser doppler velocimetry for skin blood flow measurement
• cold pressor test
•
29. ASSESSMENT OF AUTONOMIC FUNCTION
• Tests for pupillary function
• cocaine test
• Adrenaline test
• Test for bladder function
• Test for sphincter-detrusor dyssynergia
• cystometrogram
30. Power spectral analysis
• Power spectral analysis
• New methods using analysis of biomedical signal variability to assess autonomic
function have been developed and are gaining popularity.
• Heart rate (R–R interval) or arterial pressure variability is analyzed using power
spectral analysis.
• Power spectral analysis consists of breaking down variability into its component
sinusoidal waves by means of fast Fourier transformation.
• Information derived from applying Fourier transformation on biomedical signal
variability is indirectly used to assess ANS activity.
31.
32. PLASMACATECHOLAMINES
• Normal plasma epinephrine and norepinephrine levels are typically in the
range of 100 to 400 pg/mL, and
• they can increase sixfold or more with stress.
• A striking relationship between mortality rates for patients with CHF and
elevated plasma norepinephrine levels, resulted in the use of β-adrenergic
antagonists to treat ventricular dysfunction.
• studies relying only on arterial and venous catecholamines suggested that the
hepatomesenteric bed contributes significantly to total-body clearance of
catecholamines, but only minimally (<8%) to spillover.
33. PLASMACATECHOLAMINES
• The Release of norepinephrine from the gut (≤25% of the total body) was
largely obscured by efficient extraction (>80%) in the liver. Similarly, selective
elevations in release of norepinephrine from the heart, which may be
associated with ischemia.
• significant increases in plasma catecholamine levels (>1000 pg/mL) in levels
are good markers of activation of the sympathetic nervous system.
34. Anesthesiaimplicationsin patientswithautonomicdysfunction
• Gastric emptying time is delayed in patients with uncontrolled hyperglycaemia.
Strict guidelines for NPO should be followed to avoid the chances of regurgitation
and aspiration. Metoclopramide is administered to decrease the gastric emptying
time. Aspiration is likely to get aggravated in diabetes due to stiff joint syndrome
and in such patients prokinetics-like cisapride may be ineffective in reducing the
volume of gastric content.
• Anaemia may be associated patients with AN; this needs to be optimised before
undertaking any intervention.
• Haemodynamic response to intubation is altered . Patients with AN may present
either with an exaggerated or an attenuated haemodynamic response. Careful
monitoring with titrated anaesthetic regimen, minimal airway manipulation, and
timely intervention is required to maintain stable dynamics.
35. Anesthesiaimplicationsin patientswithautonomicdysfunction
• Perioperative cardiovascular lability. The normal autonomic response of
vasoconstriction and tachycardia does not completely compensate for the vasodilating
effects of anaesthesia. This may result in severe degree of hypotension sometimes not
responding to vasopressors and inotropes.
• These patients are more prone to hypothermia and thus decreased drug metabolism
and impaired wound healing, and rarely with hyperthermia. Effective techniques to
prevent hypothermia and continuous temperature monitoring should be considered
• Insulin has paradoxical effects on cardiovascular system. At low doses, it has
vasoconstrictor effect but at high doses, which are often used for diabetes treatment, it
causes vasodilatation. That is the reason, in patients with AN, insulin causes a decrease
in supine arterial pressure and exacerbates postural hypotension
36. Anesthesiaimplicationsin patientswithautonomicdysfunction
• Evidence also suggests that there is increased risk of neuropathy after peripheral
nerve blocks
• Patients with AN have reduced hypoxic-induced ventilatory drive. Choice of
anaesthesia and dosage proper planning of perioperative management is essential to
decrease the incidence of complications. Judicious use of opioid should be done to
avoid postoperative respiratory depression .
• Risk of infection and vascular damage may be increased with the use of regional
techniques in diabetic patients, consequently increasing risk of development of
epidural abscess
37. Anesthesiaimplicationsin patientswithautonomicdysfunction
• The severity of AN can have adverse consequences in diabetic patients. Patients may
have uncontrolled cardiovascular instability, especially with central neuraxial
anesthesia. Nerve blocks preferably ultrasound guided is safe. The presence of
peripheral neuropathy must be well documented prior to any regional procedure.
• Slow controlled positioning is essential to avoid precipitous fall of blood pressure.
Padding of vulnerable area is properly done to avoid iatrogenic injuries during
positioning
• .
• Orthostatic hypotension may precipitate in the postoperative period. Continuous
monitoring of blood pressure, respiration with oxygen supplementation, and
adequate analgesia are mandatory at least for 24 h following any intervention
• .
38. Anesthesiaimplicationsin patientswithautonomicdysfunction
• Pneumoperitoneum in laparoscopic surgeries is again a concern in patients with AN.
This should be used with caution or avoided to negate its ischemic effects on the
adjacent viscera and blood vessels. Another major concern is postoperative
paralytic ileus, especially following abdominal surgeries.
• Several strategies need to be utilised for enhanced recovery of patients undergoing
surgery to promote earlier resumption of normal diet, earlier mobilisation, and
reduced length of stay.Adequate postoperative pain management, preferably with
ultrasound-guided regional blocks are helpful.
39. Anesthesiaimplicationsin patientswithautonomicdysfunction
• Central neuraxial block -Significant hypotension may be seen while establishing
central neuraxial block due to sympathetic block in the presence of autonomic
neuropathy.
• Central neuraxial anaesthesia may carry greater risks as profound hypotension may
have deleterious consequences if they are associated with coronary artery,
cerebrovascular, or renovascular disease.
40. ANS dysfunction relevant to critical care
• Autonomic changes in spinal cord injury
• Spinal shock describes the initial phase of neurological dysfunction, consisting of loss
of reflexes and autonomic control below the level of spinal cord injury.
• This leads to flaccid paralysis,areflexia, and associated loss of sensory and motor
activity below the injury.
• ‘Neurogenic shock=hypotension+bradycardia+peripheral vasodilatation
• Autonomic hyperreflexia -Supraspinal feedback and inhibition of many autonomic
reflexes are lost after spinal cord injury. Small stimuli below the level of injury can
cause exaggerated, disordered autonomic response seen between 3 weeks and 9
months of the initial injury.
41. ANS dysfunction relevant to critical care
• Guillian–Barré syndrome
• Autonomic dysfunction involving both sympathetic and para sympathetic systems is seen in
Guillian Barré syndrome. Sinus tachycardia is the most common manifestation. Orthostatic
and persistent hypotension, paroxysmal hypertension, fluctuations in heart rate, paralytic
ileus, urinary retention, and abnormalities of sweating are commonly present.
• Tetanus
• Basal sympathetic activity is higher and episodic sympathetic hyper responsiveness is seen in
tetanus. Features of autonomic dysfunction present in tetanus are hypertension,
tachycardia, arrhythmias, sweating, and fever.
• Epinephrine and norepinephrine levels are very high during episodes of autonomic
hyperactivity .
• Unopposed β-block can precipitate acute congestive cardiac failure and hence avoided.
Sedatives in the form of benzodiazepines and morphine are also used to decrease
catecholamine output. Magnesium sulphate is used in severe tetanus as an adjunct to
sedation and adrenergic block
42. ANS dysfunction relevant to critical care
• HIV infection
• Autonomic dysfunction is a common occurrence in HIV infection. Awareness
of this complication of HIV infection is import ant to decrease the morbidity
and mortality in this patient group
• Porphyria
• Sympathetic hyperactivity is a feature of autonomic dysfunction in porphyria.
• Hypertension, tachycardia, abdominal pain, and altered bowel movements
are some of the features present during
43. Autonomic reflexes during anesthesia and surgery
• oculocardiac reflex-traction on eyeball - bradycardi asystole
• Abdominal reflex- stretching of viscera - bradycardia ,hypotension,apnoea,laryngeal spasm
• Recto laryngeal reflex- anal sphincter dilatation-laryngeal spasm and apnoea
• Recto cardiac reflex -anal sphincter dilatation -bradycardia and hypotension
• Prevention
• These autonomic reflexes can be prevented by adequate depth of anesthesia
• Atropine prophylaxis
• ask surgeons to avoid manipulation and proceed gently
44. Surgical Stress Response
• Surgical Stress Response: Surgical stress, particularly that associated with
major operations, results in profound metabolic and endocrine responses.
• The combination of autonomic, hormonal and catabolic changes that
accompany surgery has been called the surgical stress response.
• Three separate lines of evidence suggest that attenuation of the surgical
stress response can lead to improved outcomes.
• Interruption of the sympathetic response to surgery, markedly reduced
surgical stress , intraoperatively and postoperatively.
45. Surgical Stress Response
• The use of continuous thoracic epidural infusions of local anesthetics
minimized the rise in plasma catecholamines, cortisol, and glucagon and
improved outcomes.
• Continuation of epidural infusions well into the postoperative period was
regarded as essential to improving outcome.
• Inflammatory and immunologic responses, which are necessary for infection
control and wound healing, appear to be unaffected.
46. Surgical Stress Response
• When neonates with complex congenital heart disease, underwent cardiac
surgery, those who received high-dose sufentanil infusions intraoperatively
and for the first 24 hours postoperatively to reduce the stress response had
lower β-endorphin, norepinephrine, epinephrine, glucagon,aldosterone, and
cortisol levels than did controls.
• The mortality rate in the high-dose opiate group was significantly lower than
in the study or historical controls.
47. Surgical Stress Response
• The perioperative β blockade: The ability to alter overall survival at 2 years
with a perioperative regimen of β blockade provided compelling evidence of
benefit of attenuating the stress response.
• Similar results were achieved when perioperative α2-agonists were given to
“at-risk” patients as well.
• β-blocker or the α2-agonist suppressed the stress response and improved
outcomes.
