Myocardial tissue CO2 tension detects coronary blood flow reduction after coronary artery bypass in real-time†.
BACKGROUND
Coronary stenosis after coronary artery bypass grafting (CABG) may lead to myocardial ischaemia and is clinically difficult to diagnose. In a CABG model, we aimed at defining variables that detect hypoperfusion in real-time and correlate with impaired regional ventricular function by monitoring myocardial tissue metabolism.


METHODS
Off-pump CABG was performed in 10 pigs. Graft blood flow was reduced in 18 min intervals to 75, 50, and 25% of baseline flow with reperfusion between each flow reduction. Myocardial tissue Pco2 (Pt(CO2)), Po2, pH, glucose, lactate, and glycerol from the graft supplied region and a control region were obtained. Regional cardiac function was assessed as radial strain.


RESULTS
In comparison with baseline, myocardial pH decreased during 75, 50, and 25% flow reduction (-0.15; -0.22; -0.37, respectively, all P<0.05) whereas Pt(CO2) increased (+4.6 kPa; +7.8 kPa; +12.9 kPa, respectively, all P<0.05). pH and Pt(CO2) returned to baseline upon reperfusion. Lactate and glycerol increased flow-dependently, while glucose decreased. Regional ventricular contractile function declined significantly. All measured variables remained normal in the control region. Pt(CO2) correlated strongly with tissue lactate, pH, and contractile function (R=0.86, R=-0.91, R=-0.70, respectively, all P<0.001). New conductometric Pt(CO2) sensors were in agreement with established fibre-optic probes. Cardiac output was not altered.


CONCLUSIONS
Myocardial pH and Pt(CO2) monitoring can quantify the degree of regional tissue hypoperfusion in real-time and correlated well with cellular metabolism and contractile function, whereas cardiac output did not. New robust conductometric Pt(CO2) sensors have the potential to serve as a clinical cardiac monitoring tool during surgery and postoperatively.
The Intervention Centre, Division for Emergencies and Critical Care Medicine.
S E
SE
Pischke
The Intervention Centre.
S
S
Hyler
Department of Clinical and Biomedical Engineering.
C
C
Tronstad
The Intervention Centre.
J
J
Bergsland
The Intervention Centre, Institute for Clinical Medicine, University of Oslo, Oslo, Norway.
E
E
Fosse
The Intervention Centre.
P S
PS
Halvorsen
Clinic of Cardiology, Oslo University Hospital and.
H
H
Skulstad
Division for Emergencies and Critical Care Medicine, Institute for Clinical Medicine, University of Oslo, Oslo, Norway t.i.tonnessen@medisin.uio.no.
T I
TI
Tønnessen
D000818:Animals; D001784:Blood Gas Analysis / Q000379:methods; D002245:Carbon Dioxide / Q000378:metabolism*; D002302:Cardiac Output / Q000502:physiology; D047549:Coronary Artery Bypass, Off-Pump / Q000379:methods*; D003326:Coronary Circulation / Q000502:physiology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D008297:Male; D023421:Models, Animal; D008991:Monitoring, Physiologic / Q000379:methods*; D009206:Myocardium / Q000378:metabolism*; D012039:Regional Blood Flow / Q000502:physiology*; D013552:Swine
D002245:Carbon Dioxide
carbon dioxide; coronary artery bypass; diagnostic equipment; monitoring, intraoperative; monitoring, physiologic; perioperative care