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TRANSCRIPT
12/18/2012
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Intubation/Hyperventilation Paradox: Implications for
Traumatic Brain Injury
Joshua Gaither, MD, FACEPAssistant Professor of Emergency Medicine
Daniel Spaite, MD, FACEPProfessor and Distinguished Chair
of Emergency Medicine
Disclosures
We will refer to the EPIC Study multiple times
Funded by the NIH-NINDS 1R01NS071049-01A1 (Adults)
3R01NS071049-S1 (EPIC4Kids)
Objectives Understand the physiological changes that
occur with hyperventilation
Recognize “inadvertent ventilatoryinattentiveness”
Become aware of the impact of hyperventilation on TBI outcomes
Understand the shift from focus on ETI as a procedure to proper post-intubation ventilation
Be able to prevent the intubation/hyperventilation paradox
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Impact
Leading cause of death / disability worldwide
In USA - TBI 5.3 million Americans or 2% of the population○ have moderate to severe disability
○ require long term assistance with daily activities
DIRECT cost○ 60 billion/year (2000)
Physiology & Pathophysiology
Normal CNS & cardiac physiology
Cardiac changes after hyperventilation
Vascular changes after hyperventilation
Cellular changes after hyperventilation
Normal Physiology
Global CNS PerfusionCPP = MAP – (ICP or JVP)
CNS Perfusion
Vaso-dilationHypovent or CO2/H+ vasodilation Perfusion
Vaso-constrictionHypervent or CO2/H+ vasoconstriction Perfusion
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Pathophys: 1° Brain Injury
Tissue Damage Occurs at the moment of impact
Essentially irreversible
No known treatments, many attempted: Beta-hydroxybutyrate
Hypothermia
Etc.
Pathophys: 2° Brain Injury
Tissue Damage Occurs after the initial trauma Possibly reversible Often preventable
Result of cellular hypoxia Systemic hypoxia Systemic hypoperfusion
○ Blood loss, spinal shock, etc.
Local hypoperfusion: ○ High ICP or JVP○ Changes in local CNS perfusion
The Historical Ironies:It’s ALL About Cerebral Blood Flow
Irony #1:
Decreasing ICP by “keeping them dry” does so by decreasing cerebral blood flow
Irony #2:
Decreasing ICP by hyperventilating does do by decreasing cerebral blood flow
Net effect: You feel good about lowering ICP… but you’ve done so by causing CNS ischemia
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The Historical Ironies: All About CBF
Irony #1: Decreasing ICP by “keeping them dry” does so by decreasing cerebral blood flow Dry = Low Central Venous Pressure (preload)
Pathophysiology: hyperventilation/PPV Increase interthorasic pressure
Preload
MAP
CPP
The Historical Ironies: ALL About CBF
Irony #2: Hyperventilation decreases ICP by decreasing cerebral blood flow!!! CO2
Vasoconstriction
Cerebral Blood Flow
CPP = MAP – ICP
CNS Vasoconstriction
How could something that decreases ICP cause an increase in mortality
Hypervent CO2/ H+
Vasoconstriction Perfusion
But that’s not All
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Hypocarbia Damages Cells Ca++ influx into cells depolarization release
of glutamate initiation of apoptosis
CO2 or pH increase cell membrane
permeability protein shifts loss of membrane potential, mitochondrial rupture.
left shift of the oxygen-hemoglobin local hypoxia
What does hyperventilation after ETI do?
From Pathophysiology to Patient Outcomes
Moderate hyperventilation: OR of mortality when arrival pCO2 <30
1.8 (CI: 1.1-3.0)
More severe hyperventilation = greater mortality Patients with severe hyperventilation had a higher
mortality rate 56% vs 30% (OR 2.9, CI 1.3-6.6)
One study showed a six‐fold increase
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Why is Hyperventilation So Bad??
How could something that decreases ICP cause a six‐fold increase in mortality?
The decreased ICP occurs because ofprofound cerebral vasoconstriction
All advantages gained from lower ICP are overwhelmed by the CNS ischemia
And Now…on to the Fistfight
Our opinion:
Much of the EMS intubation controversy has been fought on an overly‐simplebattleground.
Controversy: Should TBI Patients Be Intubated… At All? Numerous studies:
Poorer outcomes in TBI patients intubated in the field
Severity-adjusted outcomes (field vs. ED ETI) Death: aOR 3.99
Poor neuro outcome: aOR 1.61
Moderate/severe functional impairment: aOR 1.92
Wang, Peitzman, Cassidy: Ann Emerg Med 2004.
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Should TBI Patients Be Intubated… At All? San Diego RSI Trial Field ETI vs. non-intubated EMS controls
Risk of death: 33.0% vs. 24.2% (RI = 36.4%)
Trial was terminated early by the DSMB due to increased mortality with RSI
Davis, Hoyt, Ochs: J Trauma; 2003
Should TBI Patients Be Intubated… At All?
So…is prehospital ETI bad for TBI patients?
Many experts believe ETI should be delayed until arrival at the ED
ETI is Bad??? Studies showing worse outcomes with ETI
Stiell: CMAJ 2008;178:1141-52 Davis: J Trauma 2003;54:444-53 Davis: J Trauma 2005;58:933-9 Davis: J Trauma 2005;59:486-90 Denninghoff: West J Emerg Med 2008;9:184-9 Murray: J Trauma 2000;49:1065-70 Wang: Ann Emerg Med 2004;44:439-50 Wang: Prehosp Emerg Care 2006;10:261-71 Eckstein: Ann Emerg Med 2005;45:504-9 Bochicchio: J Trauma 2003;54:307-11 Arbabi: J Trauma 2004;56:1029-32
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But….Wait a Minute!!!
Studies showing better outcomes with ETI Winchell: Arch Surg 1997;132:592-7
Klemen: Acta Anaesthesiol Scand 2006;50:1250-4
Warner: Trauma 2007;9:283-89
Davis: Resuscitation 2007;73:354-61
Davis: Ann Emerg Med 2005;46:115-22
Bulger: J Trauma 2005;58:718-23
Bernard: Ann Surg 2010;252:959-965
So…Should TBI Patients Be Intubated in the Field???
The question isn’t nearly that simple!!!
Focusing solely on the procedure ignores an incredibly important factor
Should TBI Patients Be Intubated… At All? Randomized: PM RSI Vs. ED intubation
Meticulous ETCO2 management post‐ETI
Favorable Neuro Outcome (GOS‐E 5–8)
PM RSI: 51% (80/157)
ED ETI: 39% (56/142 )
aOR 1.28
Bernard, Nguyen, Cameron. Ann Surg; 2010
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So…Why the Dramatic Differences in the Studies??? The “Intubation-Hyperventilation Paradox” If done well, intubation has the potential to:
-Protect the airway
-Provide good ventilation and oxygenation
Ironically…it also makes it much easier to:
-Over-ventilate
-Hyper-ventilate
Gaither, Spaite, Bobrow: Ann Emerg Med; 2012
Three Major Problems With Manual Ventilation
1. Hyperventilation:
-Bagging faster than one breath every sixseconds (10 bpm)
-Even moderate hyperventilation kills brain cells and causes major, debilitating morbidity or death
-Davis: ETCO2 increments of 3 mmHg <32
Three Major Problems With Manual Ventilation
2. Over-ventilation: Squeezing the bag too hard/too aggressively/too deeply
-High airway pressure
-Increased JVP and ICP
-Decreases venous return
-Cardiac output/Cerebral perfusion
-Alveolar damage ARDS
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Three Major Problems With Manual Ventilation
3. Inadvertent Ventilatory Inattentiveness:
-A recent landmark discovery:
-Every healthcare provider has this neuro-psychiatric disorder
Inadvertent Ventilatory Inattentiveness (IVI) The syndrome: During manual ventilation…
without meticulous prevention…everyoneinevitably gets distracted and hyper/over-ventilates.
Studies: Typical rate: 24-40+ bpm
-Our epi level is higher than the patient’s
Inadvertent Ventilatory Inattentiveness (IVI) We cannot “wing it” Without adjuncts…everyone manually
ventilates…wrong
-Even anesthesiologists and RTs
Three things are unavoidable:
-Death, Taxes…and IVI
A recent hospital example:
-“Hey…pay attention…get bagging!!!!”
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Inadvertent Ventilatory Inattentiveness (IVI)
The Cure: Meticulous, multifaceted, active, adjuncts to prevent hyper- and over-ventilation Cadence devices RR = 10
Pressure-controlled bags
ETCO2 monitoring
The “V-EMT”
EPIC Study’s Plan to Prevent IVI:The “Ventilator EMT”
The V-EMT: Assigned to manual ventilation
The most important person on the team!!
-Equivalent to the “Compressor” in MICR
EPIC’s Plan to Prevent IVI:The “Ventilator EMT”
The V-EMT’s job:
Maniacal about ventilatory rate/depth
Meticulously uses ventilatory adjuncts
Should not be disturbed
If available, add a “spotter”
-Someone to watch the “watcher”
-That’s how important this is!!!
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Adjuncts for Preventing Hyperventilation
Until patient on a ventilator (EMS/hospital): Cadence Device
-Timed flashing light
-10 bpm/20-peds <15
-1 sec breath
Adjuncts for Preventing Hyperventilation Until patient on a ventilator: Pressure-controlled bag
-Helps prevent hyper and over-ventilation
Adjuncts for Preventing Hyperventilation Continuous ETCO2 monitoring
Target: 40 mmHg
Range: 35-45 mmHg
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Optimal Ventilation for TBI Best:
- Initial cadence device/PC bag followed by…
- ETCO2 monitoring to modulate ventilation rate asap followed by…
- Mechanical ventilator asap @ 7cc/kg (not 10)
Next Best:
- Cadence device/PC bag
- ETCO2 monitoring
Barely acceptable: CD/PCB
Ventilation for TBINOT ACCEPTABLE:
- Manual ventilation without a cadence device and PC bag
- Unfortunately, most agencies that intubate have neither of these devices
Early findings in EPIC Study: Many systems with ETCO2 monitoring simply use
them to confirm tube placement…and then nicely document that they are inadvertently hyperventilating!!!
Termed: “ETCO2 monitoring that isn’t”!!!
If you have ETCO2 monitoring…use it…check it…QI it…report it…ask about it…demand to see the waveforms…be maniacal.
Beware: ETCO2 That ISN’T!!!
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Early findings in EPIC Study: Don’t let ETCO2 monitoring be a tool that
simply documents you’re killing TBI patients!!!
Beware: ETCO2 That ISN’T!!!
Because of the universal syndrome of IVI…intubation with unaided manual ventilation is always harmful!!! Prehospital and in-hospital
ETI/ventilation as we often do it gives worseoutcomes than BLS
With ventilation adjuncts and meticulous attention to preventing hyper- and over-ventilation…ETI may improve TBI outcomes in the setting of a busy EMS system, active medical direction, and high success rates
SUMMARY
The days when it was acceptable to intubate TBI patients without the adjuncts that preventhyper/over-ventilation are gone!!!
ETI without meticulously-controlled post-intubation ventilation is a downgrade from BLS care.
Many systems with ETCO2 monitoring simply use them to confirm tube placement…and then document that they’re inadvertently hyperventilating!!!
If your system doesn’t have at least CDs/PCBs, you should not be intubating TBI patients.
Take Home Messages
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www.EPIC.Arizona.edu
Special thanks to the EPIC Partners
Historical Perspective:All About ICP
(josh…exactly redundant with slide #9)
Hyperventilation: Significantly decreases ICP…so…we thought it
MUST be good for TBI patients