Deep hypothermic circulatory arrest (DHCA) is a technique used in cardiac surgery to facilitate operations on the aortic arch. It involves inducing circulatory arrest through deep hypothermia to prevent ischemic injury while working on the aortic arch. Various neuroprotective strategies are used like pharmacological neuroprotection, neurological monitoring, and cerebral perfusion techniques like antegrade cerebral perfusion and retrograde cerebral perfusion to extend the safe duration of DHCA. Optimal temperature management and the differences between unilateral versus bilateral cerebral perfusion are factors considered to reduce neurocognitive risks of DHCA.

1. Deep Hypothermic
Circulatory Arrest
Manu Jacob

2. • DHCA VS MHCA with SACP.
• Unilateral VS Bilateral ACP protection During DHCA.
• Optimal temperature Management in Aortic arch Surgery.
• DHCA & Neurocognitive functions.
• DHCA with RCP : How long is safe?
Insight..

3. HYPOTHERMIA
DEFINITIONS OF BODY TEMPERATURE
Term Temperature
Hyperpyrexia > 40 - 41.5 °C
Hyperthermia >37
Normothermia 35-37
Mild hypothermia 32-35
Moderate hypothermia 25-31
Deep hypothermia 18-24
Profound hypothermia <18
Hypothermia Temperature Use
Tepid 33 – 35 Good for short operation
Mild 31 - 32 Protection of beating heart and neurological system
Moderate 25 - 30 Protection of non beating heart and neurological system
Deep 15 - 20 DHCA for typically 40 - 60 minutes

4. Neuro protectant strategies during DHCA
Anaesthesia Glycemic control
External cranial cooling
Neurological monitoring
CSF drainage
Pharmacological Neuroprotection
Perfusion Acid base management strategy
Hemodilution
Leukocyte depletion
Surgical Intermittent Cerebral Perfusion
Selective Antegrade Cerebral Perfusion
(SACP)
Retrograde Cerebral Perfusion (RCP)

5. Effect of temperature on Cerebral Metabolic Rate
Temperature
(°C)
CMR
(% baseline)
Duration of safe
CA (min)
CMRO
(ml/100 g/min)
37 100 5 1.48
32 70 (66-74) 7.5 0.80
30 56 (52-60) 9 0.65
28 48 (44-52) 10.5 0.51
25 37 (33-42) 14 0.36
20 24 (21-29) 21 0.20
18 17 (20-25) 25 0.16
15 14 (11-18) 31 0.11
CMR Cerebral Metabolic Rate, CA Circulatory Arrest. CMRO, Cerebral Metabolic Rate for Oxygen

6. Retrograde Cerebral Perfusion (RCP)
Benefits:
Provides hypothermic blood and produces uniform cooling of the brain.
Flushes the air and particulate emboli out of arch vessels.
Provide some oxygen and substrates to the brain
Remove metabolic wastes.
Temperature of the perfusate 10-12°C
Flow rate for RCP.
Most surgeons flow 300-500 ml/min to SVC
pressure 15-25 mmHg
SVC pressures up to 40 mmHg.
Flow rates: up to 1,600 ml/ min with Neurophysiological monitoring

7. Antegrade Cerebral Perfusion
Aim:
To supply oxygenated blood to the brain during DHCA, prevents ischemic injury to brain.
To meet the metabolic demands of the brain.
To wash away the metabolic wastes.
To achieve selected temperature of the brain.
Temperature of the perfusate10-15°C
Flow rate:
10 ml/kg/min (600-1,000 ml/min). flow rates
increased 20-30% for patients at high risk for
postoperative neurologic dysfunction

8. Parameter
of Interests
Methodology ACP RCP
Blood
distribution
MRI -perfusion Uniform distribution Little or no detectable
distribution.
Micro embolization
India ink
Minimal Infraction
Minimal edema
Excessive Infraction
Excessive Edema
Massive embolization
Uniform allocation in
100% of capillaries
Trivial embolization
Trivial, in 10% of capillaries
Sequestration in brain venous
sinuses Deviation to IVC via
azygos vein
CBF in medulla Complete distribution Complete distribution
CBF in cortex 100% distribution 16% distribution
Tech99 albumine Dominant fixation in
brain capillaries
No fixation in brain capillaries

9. Parameter of Interests Methodology ACP RCP
Cerebral blood flow Fluorescence ,microscopy No significant changes
from baseline
Trivial Capillary flow
Brain edema Brain water content,
Fluid sequestration
Minimal water content
- 200ml
Excessive water content
+760 ml
Histopathology changes Histopathologic scoring No morphologic changes Neuronal injury varying
severity
Influence on SEPs SEP abolition recovery Complete abolition and
autonomic recovery by
interruption
Complete abolition after
application and no recovery
Acid-base changes Neural cells pH Unchanged pH levels Decrease to 6.4,
Recovery by reperfusion
Brain metabolism ATP levels phosp-31MRI
Cerebral O2 consumption
Light decrease in base line
Unchanged ATP levels
6.66 ml/min
2 to 3 % of base line High
decrese in ATP levels,
Recovery by perfusion
1.37 ml/min
Postoperative neurological
status
Behavioral scoring
Behavioral recovery
Gradually improved
Complete
No improvement
Complete

15. Conclusion.
• DHCA remains an important technique in Cardiac Surgery and
Anaesthesia.
• Circulatory arrest is induced to facilitate surgery on the Aortic Arch
whilst deep hypothermia is employed prevent ischemic injury.
• Neurological monitoring and pharmacological Neuroprotection are
used reduce the risk of Neurological injury.
• Anterograde and Retrograde Perfusion methods are increasingly
being used to extend the duration of DHCA.

16. Thank you.