DHCA

CARDIAC SURGERY
PERFUSIONIST
STUDENTS

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

10. 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.

11. Thank you.