Assessing Acid-Base Status in Circulatory Failure

Abstract

To assess arteriovenous differences in acid-base status, we measured the pH and partial pressure of carbon dioxide (PCO2) in blood drawn simultaneously from the arterial and central venous circulations in 26 patients with normal cardiac output, 36 patients with moderate and 5 patients with severe circulatory failure, and 38 patients with cardiac or cardiorespiratory arrest. The patients with normal cardiac output had the expected arteriovenous differences: venous pH was lower by 0.03 unit, and venous PCO2 was higher by 0.8 kPa (5.7 mm Hg). These differences widened only slightly in those with moderate cardiac failure. Additional simultaneous determinations in mixed venous blood from pulmonary arterial catheters were nearly identical to those in central venous blood. In the five hypotensive patients with severe circulatory failure there were substantial differences between the mean arterial and central venous pH (7.31 vs. 7.21) and PCO2 (5.8 vs. 9.0 kPa [44 vs. 68 mm Hg]). Large arteriovenous differences were present during cardiac arrest in patients whose ventilation was mechanically sustained, whether sodium bicarbonate had been administered (pH, 7.27 vs. 7.07; PCO2, 5.8 vs. 8.6 kPa [44 vs. 65 mm Hg]) or not (pH, 7.36 vs. 7.01; PCO2, 3.7 vs. 10.2 kPa [28 vs. 76 mm Hg]). By contrast, in patients with cardiorespiratory arrest, large arteriovenous differences were noted only when sodium bicarbonate had been given (pH, 7.24 vs. 7.01; PCO2, 9.5 vs. 16.9 kPa [71 vs. 127 mm Hg]). We conclude that both arterial and central venous blood samples are needed to assess acid-base status in patients with critical hemodynamic compromise. Although information about arterial blood gases is needed to assess pulmonary gas exchange, in the presence of severe hypoperfusion, the hypercapnia and acidemia at the level of the tissues are detected better in central venous blood.

Comparison and agreement between venous and arterial gas analysis in cardiopulmonary patients in Kashmir valley of the Indian subcontinent

“…However, Adrogue et al . [15] emphasized that both arterial and central venous sampling are needed in patients with critical hemodynamic compromise. Other investigators have also supported the use of venous measurements instead of arterial measurements for pH and gas analysis[1617] while others[18] have resisted the idea.…”

“…While analysis of central venous blood has been previously used for data comparison of VBG versus ABG[51526] sampled in central venous catheters in ICU patients, the sampling of peripheral blood allows greater flexibility in obtaining data in patients without central venous access. Our results fortify the sparse data[5727] regarding the view that peripheral VBG analysis can be used for fairly accurate assessment of arterial pH, pCO 2 , and bicarbonate values with clinically acceptable differences between the arterial and the venous values.…”

The Multimodal Concept of Hemodynamic Stabilization

“…The Fick principle adapted to carbon dioxide demonstrates the inverse relationship between the CO and dCO 2 (26). This postulate that increased dCO 2 reflects decreased flow was confirmed in several critically ill conditions such as severe sepsis, heart failure, and severe hypovolemia (27, 28). Furthermore, adding the dCO 2 to ScvO 2 for identifying VO 2 /DO 2 >30%, there was an improvement in specificity, positive predictive, and negative predictive values (29).…”

Acid-Base State in Patients after Cardiac Transplantation

“…The study demonstrates that mean values for plasma bicarbonate, carbon dioxide tension, and hydrogen ion concentration (or pH) in arterial blood, each examined independently, fall within their respective normal ranges in patients with ESHF [1][2][3][4][5][6][7][8][9][11][12][13][14][15][16][17][18][19]. This information should not be interpreted as indicating that their acidbase status is necessarily normal, for two fundamental reasons.…”