Managing severe hypoxia

 

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?

John Kheir

Summary/Key messages

  • 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?

 

NEW PARADIGM

  • 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!

 

Uses

 

  • 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

Eddy Fan

Summary/Key messages

 

What changed?

 

  • 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

 

 

  • CONCERNS
    • 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

Can you have too much oxygen?

Peter Radermacher

  • 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
  • BUT
    • 10mths after intervention
    • Cancer had increased late mortality
    • Non Cancer no diff

 

 

 

  • 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

 

 

CONCLUSION

 

  • 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???