Cardio protective reflexes

1. CARDIOPROTECTIVE REFLEXES
Moderator- Dr.Mallikarjun A.V

2. OBJECTIVES
 Cardiac reflex – Defnition
 Baroreceptor Reflex
 Chemoreceptor Reflex
 Bainbridge Reflex
 CNS Ischemic Response
 Cushing’s reflex
 Bezold Jarisch Reflex
 Valsalva Maneuver
 Abdominal Compression Reflex
 Oculocardiac Reflex
 Prevention
 Treatment

3. CARDIAC REFLEXES
 Cardiac reflexes are fast-acting reflex loops
between the Heart and CNS
 Contribute to
- regulation of Cardiac function
- maintenance of Physiologic Homeostasis
 Cardiac receptors are linked to the CNS by
myelinated or unmyelinated afferent fibres that
travel along the vagus nerve.

5.  Cardiac receptors - Atria,
Ventricles,
Pericardium
Coronary arteries
 Extracardiac receptors – Great vessels
Carotid Artery.

6. BARORECEPTOR REFLEX
 Spray-type nerve endings in
walls of large arteries
- ICA just above carotid
bifurcation
- Arch of aorta

7.  Changes in BP are monitored by Circumferential
and Longitudinal stretch receptors located in the
carotid sinus and aortic arch
 Respond rapidly to changes in BP , maintain
powerful moment-to-moment control of arterial
pressure
 Capable of regulating arterial BP around a preset
value through a Negative-feedback loop

8. BARORECEPTOR REFLEX CONT.
 Respond much more to a rapidly changing
pressure than to a stationary pressure
 Maintain relatively constant arterial pressure in the
upper body during Changes in Body Posture
 Reduce the minute by minute variation in arterial
pressure
 Pressure buffer system, Buffer nerves

10. BARORECEPTOR REFLEX

11. VASOMOTOR CENTRE IN MEDULLA

12. Vasoconstrictor
area
Vasodilator
area
Sensory area
Tractus solitarius
Location Bilaterally
Anterolaterally
Upper medulla
Bilaterally
anterolateral
Lower medulla
Bilaterally
posterolateral
medulla ,lower pons
Neurons
Function
All levels of the
spinal cord,
Excite
sympathetic
nervous system.
Inc. BP
Project upwards
Inhibit
vasoconstrictor
area
Vasodilation
Dec. BP
Receive sensory
signals through the
Vagus and
Glossopharyngeal
nerves
Controls both
vasoconstrictor and
vasodilator areas

14. Increase in MAP
↓
Stretch of BR
↓
Impulses to NTS
↓
Secondarysignals- Inhibit- Vasoconstrictor area
Excite - Vasodilator area
↓
Dec. Symp outflow
Inc. Parasymp outflow
↓
Vasodilatation,Dec HR,Contractility
↓
BP back to normal

15. BARORECEPTOR REFLEX CONT.
 Important role during - Acute blood loss
Shock.
 volatile anesthetics ( Halothane) inhibit the HR
component of this reflex
 Concomitant use of CCB’s, ACE inhibitors, or
PDE inhibitors will lessen the CV response of
raising BP through the baroreceptor reflex
- direct effects on the peripheral vasculature
- interference with CNS signaling pathways
(calcium, angiotensin)

16. BARORECEPTOR RESETTING
 Baroreceptor will adapt to the long term change of
blood pressure in 1-3 days
 Adaptation makes the baroreceptor system
unimportant for long-term regulation of arterial
pressure
 Patients with chronic hypertension often exhibit
perioperative circulatory instability as a result of a
decrease in their baroreceptor reflex response

17. CHEMORECEPTOR REFLEX
 Chemosensitive cells located in the carotid bodies and
the aortic body.
 Transduce chemical signals into nerve impulse
 Each carotid or aortic body is supplied with an abundant
blood flow through a small nutrient artery,so that the
chemoreceptors are always in close contact with arterial
blood
 Respond to - changes in pH (H+ ions excess)
- blood oxygen tension lack.
- blood Co2 tension excess

18. CHEMORECEPTOR REFLEX

19. CHEMORECEPTOR REFLEX CONT.
↓
↓
↓
↓

20. CHEMORECEPTOR REFLEX CONT.
 Do not respond strongly until BP < 80 mm of Hg.
 In the case of Persistent Hypoxia, the CNS will be
directly stimulated, with a resultant increase in
sympathetic activity.

21. CHEMORECEPTOR REFLEX CONT.
 Stimulates the respiratory centers and thereby
increasing ventilatory drive
 Ventilatory Response to Arterial Hypoximea
- Stimulates breathing when Pao2 <60 mm of Hg
- Inhibited by - Volatile Anaesthetics (0.1 MAC)
- Barbiturates
- Opiods

22. BAINBRIDGE REFLEX
 Both the atria and the pulmonary arteries have in
their walls stretch receptors called Low-
pressure receptors.
 They are similar to the baroreceptor stretch
receptors of the large systemic arteries
 Prevents damming of blood in the Veins, Atria, and
Pulmonary circulation

23. BAINBRIDGE REFLEX CONT.
Increase in right-sided filling pressure
↓
Stretch receptors in
RA wall,CavoAtrial junction SA node(15%)
↓
Vagal afferent signals
↓
Vasomotor center in the medulla
↓
Dec PS tone (40-60%) Inc HR
FOC

24. CNS ISCHEMIC RESPONSE
 Arterial pressure elevation in response to cerebral
ischemia
 CNS ischemic response is one of the most powerful
of all the activators of the sympathetic
vasoconstrictor system
 The degree of sympathetic vasoconstriction caused
by intense cerebral ischemia is often so great that
some of the peripheral vessels become occluded
and kidney caese urine production

25. CNS ISCHEMIC RESPONSE CONT.
 Does not become significant until the arterial
pressure < 60 mm Hg and reaching its greatest
degree of stimulation at a pressure of 15 to 20 mm
Hg
 Emergency pressure control system that acts
rapidly and very powerfully to prevent further
decrease in arterial pressure whenever blood flow
to the brain decreases dangerously close to the
lethal level.
 “Last ditch stand” pressure control mechanism

26. CUSHING REFLEX
Increased intracranial pressure(ICP = MAP)
↓
Cerebral ischemia at the Medullary VMC
↓
initial activation of the SNS
Inc HR, BP, and contractility Inc vascular tone
↓ ↓
improved cerebral perfusion BR reflex
( MAP > ICP)
↓
Reflex Brady

27. CUSHING REFLEX CONT.
 Cushings triad –Hypertension
- Bradycardia
- Irregular Respirations

28. BEZOLD-JARISCH REFLEX
Noxious ventricular stimuli ( Dec ventricular filling )
↓
Chemo, Mechano receptors within the LV wall
↓
Unmyelinated vagal afferent type C fibers.
↓
Reflex Inc in PS tone
↓
Triad Hypotension,
Paradoxical Bradycardia (cardioprotective)
Coronary artery dilatation.

29. BEZOLD-JARISCH REFLEX CONT.
 Cardioprotective in MI, Thrombolysis or
Revascularization and Syncope
 Spinal , Epidural
 Less pronounced in patients with Cardiac
hypertrophy or Atrial fibrillation

30. VALSALVA MANEUVER
Forced expiration against a closed glottis
↓
Increased intrathoracic pressure
↓
Venous return, CO and BP will be decreased
↓
BR reflex
↓
Inc HR , Contractility

31. VALSALVA MANEUVER CONT.
Glottis opens
↓
Inc venous return, HR , Contractility,BP
↓
BR reflex
↓
Para sym stimulation

32. ABDOMINAL COMPRESSION REflEX.
 When a BR or CR reflex is elicited, nerve signals
are transmitted simultaneously through skeletal
nerves to skeletal muscles of the body, particularly
to the abdominal muscles.
 This compresses all the venous reservoirs of the
abdomen, helping to translocate blood out of the
abdominal vascular reservoirs toward the heart.
 As a result , increased quantities of blood are made
available for the heart to pump

33. OCULOCARDIAC REFLEX
Pressure applied to the globe of the eye
Traction on the surrounding structures.
↓
Strech receptors on EOM
↓
Short ,Long ciliary N. ( Ophthalmic – Trigeminal )
↓
Gasserian ganglion
↓
Inc PS tone
↓
Bradycardia.

34.  Incidence during opthalmic surgery - 30% to 90%.
 Glycopyrrolate or Atropine reduce incidence

35. PREVENTION AND RX
 Atropine - most widely used and effective agent
in prevention and Rx of parasympathomimetic
reflex responses.
 Topical anaesthesia - can eliminate the reflex at
the afferent component.
 I.V Lignocaine is more effective than topical and
attenuates the cardiovascular responses to
noxious stimuli.
 Initial loading dose - 100 mg IV
 Continous infusion of lignocaine - 2mg / min

36. DURING SX…..
 Cessation of the applied stimulus
 Increase the depth of anaesthesia.
 IV Atropine - 5 – 10 μg/kg
 Vasopressors- Persistent hypotension

37. REFERENCES
 Guyton and Hall, Textbook of medical
physiology,11th Edition
 Miller’s Anaesthesia 8th Edition
 Stoelting’s Pharmacolgy nad Physiology in
Anaesthesia Practice 5th Edition
 Barash Clinical anaesthesia 7th Edition

38. THANK YOU