Blogger PHW (@drph_w)
- Chair: Mervyn Singer, Luciano Gattinoni
- Following on from an interesting Q +A with Luciano we now get to hear more about the nuts and bolts of managing hypoxia.
Intravenous oxygen microparticles – a lifeboat?
- Clinical vignette about a 9mo girl admitted with RSV pneumonia, immuno-compromised because of liver transplant
- Sudden hypoxia secondary to pulmonary haemorrhage patient arrested
- Intubated and onto ecmo in 20 mins
- Patient suffered intracerebral bleed this is not uncommon.
- So John asked the question:
- Why can’t we just inject O2 into the blood stream?
- Coalescesnce of O2 prevents this as a Rx option
- Need something to stop this
- O2 microbubbles have a shell that unzips as gas diffuses out leading to very small micelles when it reaches the lung and thus same viscosity.
- Developed over 3 yrs to create a syringe of O2 gas
- Microbubbles easy to make by inducing high energy at lipid and gas interface
- Smaller bubbles more stable
- Higher shear creates smaller bubbles
- Phospholipds as powder add plasmalyte add to ‘kitchen aid’ pump emulsion thru bypass pump and mix emulsion with O2 gas
- Increases vol 30-40 vol %
- Get a 90 vol %
DOES THIS TRANSFER 02 GAS TO BLOOD?
- Experminentally yes
- In vitro at 37 degrees O2 transfer into a beaker of blood in less than 30 sec
- WHAT ABOUT IN PEOPLE?
- IN VIVO TESTING
- Create baseline animal model with hypoxic vent 12% O2
- Inject IV O2
- Showed rapid increase in SpO2 70 > 90 in approx 20 secs
- As soon as O2 consumed SpO2 went back down.
What about a model of asphyxia?
- With HIGH CO2
- Began infusion of microbubbles or placebo.
- CO2 during asphyxia rose over time unsurprisingly
- Acute hypercarbia well tolerated
- MABP over time preserved
- Severe hepatic and renal injury in control grp
Microbubbles not stable in storage
- Next generation is a particle that is stable but can breakdown.
- Short term support of oxygenation hopefully will become a reality!
- Reverse life threat hypoxia
- Stabilize at intubation
- Augment O2 during CPR
How far from market
- 5 yr green light pathway 2020 watch this space!!!
Is ECMO the answer? A North American perspective
- ARDS and ECMO support
- Berlin definition http://jama.jamanetwork.com/article.aspx?articleID=1160659
- ECMO in severe subset of ARDS
- Veno Venous ECMO
- Hollow fiber membrane lung
- Exponential explosion in ECMO use in adults since H1N1flu outbreak
- Case report in 1972 http://www.nejm.org/doi/full/10.1056/NEJM197203232861204
- Successful outcome centres in North America
- Survival dismal in 70s and it was thought ECMO won’t help
- 2009 ECMO for H1N1ARDS
- Australia and NZ ECMO 75% SURVIVED big difference from 10% survival in the 70s
- UK almost halved the mortality
- CESAR STUDY
- Transfer to Leicester showed significant improvement but no significant difference in mortality
- Was this just a trial of transport to an expert centre
- Not all had ECMO
- Not all in home unit had best treatment
- Cost effectiveness?
- Survival in NZ with ECMO vs UTAH without ECMO the same
- Indications and CI for ECMO http://www.nejm.org/doi/full/10.1056/NEJMct1103720
- Practical Advice
- 1 Try NMB
- 2 Higher PEEP
- 3 if P/F < 100
- 4 Prone
- 5 ECMO
Can you have too much oxygen?
- O2 creates free radicals
- Double O2 consumption doubles radicals
- PreO2 prolongs window of opportunity
- May lead to shunt
- O2 may increase or decrease inflammation
- Hypoxia promotes inflammation
- LAVOISIER Guinea Pigs > death from pulm haemorrhage and oedema
O2 as antibiotic
- Hyperoxia prevents periop infection OLD DATA
- NOW Still true in colorectal surgery
- 10mths after intervention
- Cancer had increased late mortality
- Non Cancer no diff
- O2 leads to DNA damage
- The more exposure the more damage
- Hyperoxia and ACS
- More problems
- But normoxia increased death
- Early phase benefit with hyperoxia
- Long term outcome poorer
- Lowest mort PAO2 150-200mmhg
- Studies slightly favour normoxia
- Results are limited
- Conservative O2 SaO2 88-95% prob best to avoid hyperoxia.
- Hyperoxia vs hyperoxaemia
- High FiO2 or high PaO2
- Prob both bad
- Inflam mediators in lung chicken or egg
WHAT WOULD PETER WANT?
- Until Cancer data he would want O2 but with cancer outcomes maybe not
- Keep me at low normal O2
- Is there difference in types if cancer eg lung vs bowel?
- Who knows???