Acute transient right ventricular (RV) failure after protamine administration is a common poorly understood problem in cardiac surgery. In 8 patients undergoing coronary artery bypass grafting under extracorporeal circulation (ECC) with aortic cross clamping. We observed changes in pulmonary artery (PA) and RV mechanics, before ECC, after ECC, immediately and 10 min after protamine administration. We determined PA resistance (PVR), RV end-systolic elastance (Ees) and PA effective elastance (Ea). RV pressure-volume loops were used to determine Ees and Ea. The ratio Ees/Ea was used to determine the RV-PA coupling.
|
Before ECC |
After ECC |
After Protamine |
10 min after Protamine | |
| Flow, L/min |
6.0 + 0.8 |
7.3 + 1.0 |
6.8 + 0.9 |
6.3 + 0.7 |
| Ppa, mmHg |
20 + 2 |
23 + 2 |
22 + 1 |
22 + 1 |
| PVR, dyn.sec.cm-5 |
279 + 33 |
273 + 28 |
281 + 37 |
293 + 29 |
| Ees mmHg/ml |
0.7 + 0.2 |
0.4 + 0.1* |
0.3 + 0.1* |
0.5 + 0.1 |
| Ea mmHg/ml |
0.2 + 0.04 |
0.4 + 0.04* |
0.3 + 0.04 |
0.3 + 0.02 |
| Ees/Ea |
2.6 + 0.6 |
1.1 + 0.1* |
1.2 + 0.1* |
1.9 + 0.3 |
* P < 0.05 vs Before ECC.
PVR are not affected after CABG under ECC, even after protamine administration. RV contractility after ECC and immediately after protamine administration show a marked decrease, and is associated with a marked RV-PA decoupling. Ten minutes after protamine administration, RV contractility is ameliorated and partially restore RV-PA coupling.
We conclude that RV-PA coupling is markedly affected after CABG under cross-clamping. However, protamine has little effects on PVR and does not prevent RV contractility recovery after CABG.