H Alex Choi, MD MSc Assistant Professor of Neurology and Neurosurgery The University of Texas Health Science Center Mischer Neuroscience Institute Memorial Hermann- Texas Medical Center
Learning Objectives 1. Discuss effects of TTM on ICP. 2. Discuss medical indications TTM. 3. Discuss medical management during TTM.
Does temperature affect ICP? Yes Therapeutic hypothermia will decrease ICP
No need for a RCT Hypothermia to ~35C brings down ICP by 10mm Hg. From: Schreckinger: Neurocrit care (2009) 11:427-436
Data from a RCT Eurotherm 3235 Preliminary analysis of 17 patients Control Hypothermia Flynn THTM 2015
The real question? How does it bring down ICP? When do you use it? How do you manage medically? Is it beneficial for my patient?
Intracranial Pressure (ICP) What is ICP and why do we measure it? We measure it because it is easy to measure.
ICP and TBI Chesnut R, NEJM 2012
ICP is just a surrogate marker Most of the things we equate with ICP is actually volume. Intracranial components (Total volume approx 1500 cc) 75-80% Parenchyma 10% CSF 10% Blood
How does it bring down ICP hypothermia
How does TH effect brain volume? 1) TH decreases cerebral edema 2) TH decreases cerebral metabolism and so cerebral blood flow
Cerebral Edema What is the evidence that Hypothermia brings down cerebral edema?
2 center trial: TTM after recanalization of large MCA strokes vs Standard care TTM to 34.5C Prophylactically intubated Cooled for 48 hours with 48 hours rewarming.
How about CBF? ICP decreases so CPP should increase?
Hypothermia brings down PbtO2 Flynn THTM 2015 Choi NCS 2013
Hypothermia CBF Decreases Cerebral Metabolism leading to a decrease in CBF and a decrease in ICP
Hypothermia ICP Hypothermia decreases ICP by decreasing cerebral brain volume Brain edema Decreasing brain metabolism
Uncertainties Hypothermia brings down ICP Hypothermia trials in TBI have been conflicting NABISH I, NABISH II Hypothermia trials in Cardiac arrest (once thought to be robust, is now unclear) Hypothermia trials in other brain injury disease are equivocal
Paradigm Switch RCTs Disease Specific (Population Driven) Treatment of Disease Patient Specific (Physiology Driven) Treatment of Disease
29 year old woman ICP control
Hypothermia for ICP Control
GCS 10 in the field. On presentation agitated but localizing with intact brainstem reflexes.
Has a seizure-like episode Unable to protect airway and exam deteriorated Intubation and an ICP monitor is placed later converted to EVD for CSF diversion. ICPs above 20, initially responsive to mannitol and hypertonic saline
HD2 Na >150, deeply sedated, paralyzed still in ICP crisis TTM to 33 started Dobutamine started for bradycardia HD5 Klebsiella pneumonia HD6-7 rewarmed slowly to 37 HD7 Repeated ICP spikes requiring re-cooling to 33 HD 10 finally able to rewarm to 37 without ICP issues Total of 9 days of hypothermia HD 23 Trach/PEG. Eye opening to voice, not following commands, localizing with arms, withdrawing legs.
3 months later
Case 2 35 yo W presented with flu like symptoms for several days, vomited and had a seizure. After a CT she had a decline in mental status and was intubated for airway protection.
Cerebral Venous Sinus Thrombosis On arrival Heparin drip started Emergent cerebral angiography: Occlusion of sagittal sinus and bilateral frontal and anterior parietal cortical veins. Recanalization of sagittal sinus but cortical veins remained occluded During angiography she started having ICP crises to 40s-50s HD2 TTM 35 for ICP control Left CN6 nerve palsy, flexing HD3 TTM 33 for ICP control Extending bilaterally, then paralyzed HD4 Decompressive hemicraniectomy Extending bilaterally
HD5-8: Post crani TTM to 35 for edema control and on going ischemia ICPs under 20 but continued TTM HD 9 TTM to normothermia HD 17 exam: eyes opening to pain, grimacing, posturing arms/leg.
4 months later.
Did TTM help? I don t know. I targeted the patients physiology. But trying something keeps physicians engaged and optimistic.
Outline When to cool? How to do it right? Things to look out for.
3 phases Practical aspects Details vary depending on reason for cooling.
Devices Intravascular ZOLL (Icy) Femoral triple lumen with cooling Philips Innercool Does not provide additional access Probably the most effective cooling device The most invasive (DVT causing) Surface Arctic Sun No need for additional procedure Non invasive Needs additional access
Maintenance Generally TH for ICP requires a prolonged period of hypothermia. ELECTROLYTES, EKG changes FLUID MANAGEMENT Hypovolemia BP MANAGEMENT Mild vasoconstriction INFECTIONS COMPLICATIONS Hypervolemia Hypotension
Electrolytes Induction: Reductions in Potassium, Mag, Phosphate Maintenance: Continued reductions in electrolytes including creatinine Rewarming: Rebound Hyperkalemia
Shivering First thing that someone is going to notice when starting TTM. Neuro patients Full range of mental status Neuro exam important
Stepwise Shivering Treatment Protocol STEP Intervention Dose 0 Acetaminophen 650-1000 mg Q 4-6 hours Buspirone 30 mg Q 8 hours Magnesium Sulfate IV replacement for goal serum level (2-4 mg/dl) Skin Counterwarming 43 C / MAX Temp 1 Opioid Meperidine 50-100mg IM or IV Fentanyl drip starting dose 25mcg/hr 2 Opioid and Propofol Propofol 50-75 mcg/kg/min 3 Vecuronium 0.1-0.15 mg/kg IV
Rewarming
Rewarming Should be directed by ICP changes Concerns/Precautions Rebound ICP Vasodilatation Dramatic changes in hemodynamic profile SIRS type syndrome increased catecholamines increased O 2 consumption Rebound electrolytes (hyperkalemia) Cardiac arrhythmias All avoided with very slow rewarm 0.1-0.2 C/hr
TTM Induction Maintenance Rewarming
TTM Summary Effective for ICP Needs to be Targeting a specific physiological process Cerebral Edema Cerebral Metabolism Need Advance TTM machine Watch electrolytes, fluid balance, infections Careful rewarming
Thank You