Neurologic Trauma

1. Neurologic Trauma Bryan E. Bledsoe, DO, FACEP

2. Neurologic Trauma

3. Neurologic Trauma “Suppose you were an idiot. And suppose you were a member of Congress. But I repeat myself.” Mark Twain

4. Traumatic Brain Injury (TBI) • Defined as a blow or jolt to the head or a penetrating head injury that disrupts the function of the brain.

5. Statistics • 1.4 million people sustain a TBI each year in the United States: • 50,000 die, • 235,000 are hospitalized, • 1.1 million are treated and released from the ED.

6. Statistics • Causes: • Falls (28%) • MVCs (20%) • Struck by/against events (19%) • Assaults (11%)  Blasts are the leading cause of TBI for active duty military personnel in war zones.

7. Statistics • Males are about 1.5 times more likely to sustain a TBI as a female.

8. Statistics • Highest risk for TBI: • 0-4 years • 15-19 years • African Americans have the highest death rate from TBI.

9. Statistics • Estimated $60 billion lost from TBI (medical costs and lost productivity).* * 2000

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22. Physiology • Brain Metabolism: • Like all tissues, the brain requires a constant supply of oxygen and nutrients.

23. Physiology • Brain accounts for 2% of total body mass. • Brain accounts for 15% of total metabolism in the body. • Brain metabolic rate 7.5 times the rate of other neurological tissues.

24. Physiology • Almost all of the brain’s energy needs are supplied by glucose. • Provided by capillaries in the brain.

25. Physiology • Insulin NOT needed for glucose delivery to brain tissues.

26. Physiology • The brain is among the most oxygen dependent organs in the body. • The brain is not capable of much anaerobic metabolism. • Primarily due the high metabolic rate of the neurons.

27. Physiology • Because of this, sudden cessation of blood flow to the brain can cause unconsciousness within 5-10 seconds.

28. Physiology • Neuroglobin: • Intracellular hemeprotein. • Reversibly binds oxygen with an affinity greater than that of hemoglobin. • Increases oxygen availability to brain tissue and provides protection under hypoxic or ischemic conditions, potentially limiting brain damage.

29. Physiology • Brain requires: • Oxygenation • Glucose • Perfusion • Any deficit in these results in immediate dysfunction.

30. Intracranial Pressure • The cranial vault is effectively a closed container. • Largest opening is the foramen magnum. • Limited room for brain swelling.

31. Intracranial Pressure • There is always some pressure in the brain. • Referred to as intracranial pressure (ICP). • Normal ICP: • Children: 0-10 mm Hg • Adults: 0-15 mm Hg

32. Intracranial Pressure • Volume of the cranial vault defined by the Monro-Kellie doctrine: Intracranial Volume (fixed) = Brain Volume + CSF Volume + Blood Volume + Mass Lesion Volume

33. Intracranial Pressure • Normally: • Brain = 80% of cranial vault space • Blood = 10% of cranial vault space • CSF = 10% of cranial vault space Space Available for Blood or MASS = 0%

34. Intracranial Pressure • To perfuse the brain, the pressure of blood delivered to the brain MUST be greater than the intracranial pressure. CPP = MAP - ICP

35. Intracranial Pressure • Mean Arterial Pressure: MAP  DP + 1/3 (SP–DP)

36. Intracranial Pressure • Perfusion of the brain is driven by the CPP. MAP - ICP = CPP • - 30 = 40 CPP of 60 is the critical minimum threshold. CPP of 40 is the critical minimum threshold for children < 8 years of age.

37. Intracranial Pressure • Injury to brain tissue causes: • Swelling • Bleeding • Edema • All cause an increase in the size and mass of the brain.

38. Intracranial Pressure • As the brain swells, it will eventually reach a critical volume where ICP increases to a point that perfusion is compromised.

39. Brain Injury • Etiology of TBI: • Primary injury: • Damage to the brain from mechanical effects of trauma causing: • Ischemia • Anoxia/hypoxia • Shear injury

40. Brain Injury • Secondary Injury: • Results from a traumatic event and changes in the brain or in the brain vasculature. • Hypoxia • Hypotension ( cerebral blood flow) •  ICP • Hyperglycemia/Hypoglycemia • Metabolic disturbances • Seizures

41. Brain Injury • 12-24 hours post-injury: • Hypoperfusion and decrease in CBF. • Results from increases in distal microvascular resistance and intravascular clot formation.

42. Brain Injury • 1-5 days post injury: • Increased CBF > CMRO2. • Vascular engorgement • Swelling • Increased ICP • Induction of free radicals and oxidative stress.

43. Brain Injury • 5/6-14 days post injury: • CBF slows due to vasospasm • Brain vulnerable to changes in ICP.

44. Brain Injury • Secondary Injury: • Impaired autoregulation: • Autoregulation is the ability of the brain to maintain CBF in light of changes in BP and CPP. • Impaired autoregulation causes: •  O2 delivery to the brain and cerebral ischemia. • Cerebral metabolism altered due to loss of, or a decrease in, CBF. • Conversion from aerobic to anaerobic metabolism.

45. Brain Injury • Secondary Injury (extracranial causes): • Hypotension (SBP < 90 worsens outcomes) • Hypoxia (significantly associated with increased morbidity and mortality) • Hypocapnia: • Low CO2 causes vasoconstriction • 1 mm Hg decrease on CO2 = 3% decrease in CBF. • Anemia • Hyperthermia

46. Brain Injury

47. Brain Injury • Compensatory mechanisms: • Brain shifts or is compressed. • Venous blood is shunted to heart. • CSP shunted to spinal SAS.

48. Secondary Injury

49. Signs and Symptoms • Early ( ICP): • Altered mental status • Agitation • Nausea and/or vomiting • Hemiparesis

50. Signs and Symptoms • Late ( ICP): • Coma • Hemiplegia • Posturing • Cushing’s Triad: • Widening pulse pressure • Bradycardia • Respiratory abnormalities