Central cardiovascular and oxygen variables during haemorrhage in the pig

Background: We evaluated the ability of the standards issued by the Danish Society of Anaesthesiologists to reflect a blood loss. Methods: In 9 pigs bled (0-24 ml kg(-1)) and retransfused (to 28 ml kg(-1)) during halothane anaesthesia, central cardiovascular, thoracic electrical impedance (TI), oxygen, acid-base and temperature variables were recorded. Results: With the recommendation for minor surgery (mean arterial pressure (MAP) and heart rate (HR)), the correlation to the blood loss was 0.74 (P< 0.001) and with that for major surgery (MAP, HR, central venous pressure (CVP) and rectal temperature (Temp(r))) it was 0.79 (P< 0.001). With the recommendation for extensive surgery (MAP, HR, CVP, pulmonary artery catheter variables and the central-peripheral temperature difference (Delta Temp,(r-t))), the correlation was 0.84 (P< 0.001). Non-invasive monitoring (MAP, HR, Delta Temp(r-t), TI and near-infrared spectroscopy of the brain (SinvosO2)) was only slightly better than basal monitoring (r=0.76, P< 0.001). However, adding arterial base excess (BE), TI and peripheral temperature (Temp(t)) to the recommendation for major surgery resulted in a correlation of 0.87 (P< 0.001), while adding BE and TI to the recommendation for extensive surgery raised correlation to only 0.88 (P<0.001). Conclusion: When the recommendations were followed the correlation to the blood loss ranged from 0.74-0.84. However, with the recording of MAP, HR, CVP, Delta Temp(r-t), BE and TI a correlation of 0.87 was achieved, indicating that a pulmonary artery catheter may not be in need for patients undergoing surgical procedures with expected haemorrhage.