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Fundamental questions. How does the brain damage occur? Can we select at risk patients? What therapies do we have? How do they work? What is the side effect? What is the risk –benefit picture?. CBF & CPP. CBF - 50ml/100g/min -750ml/min – 15-20% CO 20-25 ml/100g/min – cerebral impairment
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Fundamental questions • How does the brain damage occur? • Can we select at risk patients? • What therapies do we have? • How do they work? • What is the side effect? • What is the risk –benefit picture?
CBF & CPP • CBF-50ml/100g/min -750ml/min – 15-20% CO 20-25 ml/100g/min – cerebral impairment 15-20 ml/100g/min - isoelectric EEG <10 ml/100g/min - irreversible damage • CPP = MAP – ICP : 80-100 –normal <50 – slowing EEG ,cerebral impairment 25 - 40 – Flat EEG <25 - irreversible damage
CBF- Auto regulation CBF 50 MAP 60 mmHg 160 mmHg
CBF &Variables CBF depends on, • PaCO2 (20-80mmHg)-1-2 ml/100g/min /mmHg • T- 5-7%change/ 1 change • PaO2 <50 mmHg CBF 0
Cerebral protection -Strategies • Optimize CPP • Decrease CMR • Block the mediators of cell injury - at ischemic cascade - at reperfusion cascade
Protective techniques • Brain Shrinkage • Hyperventilation Optimize CPP • Appropriate BP • Hypothermia Decrease CMR • Burst suppression • Pharmacological protectors -Block the mediators of cell injury
ISCHEMIC CASCADE Na-K pump failure Na+ Ca+ Glutamate Phosholipases PL FFA
REPERFUSION CASCADE TAX LT PG OFR Endothelial damage&Platelet,WBC plugs Arachidonic acid PL FFA
Pharmacological intervention • CMR Reduction • Barbiturates: Decreases CMR Decreases Ca+ Decreases OFR Na+ channel blockade Decreases Glucose entry Decreases refractory ICP Inverse steal blood flow
Pharmacological intervention • CMR Reduction • Propofol, Etomidate • Morphine, Fentanil, Sufentanil, Remifentanil • Diazepam, Midazolam • Ketamine, Dexmedetomidine • Halothane, Enflurane, Isoflurane, Sevoflurane, Desflurane
Pharmacological intervention • Neuronal injury protectors A} pre synaptic level- SNX III –Ca+ blocker B} post synaptic level 1.Na+ blocker-All volatile anaesthetic agents -Barbiturates -Lamotrigine - Riluzole -Lubeluzole 2. Ca+ blocker-Nimodipine -Nicardipine 3.NMDA antagonists: Competitive blocker-Selfotel Non Competitive blocker-Dizoclypine -Dexromethorphan -ketamine
Pharmacological intervention 4.Glycine site analogues-felbamate, Licostinel 5.NO synthase inhibitors –lifarizine, 7nitroindazole 6.Mg+-Ca+ blockade, NMDA antagonist 7.steroids-anti inflammatory action, ?neuronal protection -MPS, Tirilazad 8.OFR scavengers- Vit-E, PBN{phenyl derbuyl nitrone}, Tirilazad,Mannitol 9.Cytokinin inhibition-TNF Receptor I, TNF alfa mab 10. Anti adhesion molecule Ab