Medicine of the Future in America

The Oxyhemoglobin Dissociation Curve in Liver Cirrhosis: Results

The mean ODC was the same in the two groups (Fig 1). However, the dispersion of the Po2 values for the cirrhotic patients was significantly (p < 0.01 to p < 0.0001) increased: So2% of 20 to 80% (Table 1). Table 1 shows the SD of the Po2 values for 11 levels of oxygen saturation and related indexes (mean ± SD) for control subjects (n = 50) and cirrhotic patients (n = 50). Table 2 shows the effect of dispersion (1.96 X SD) of the Po2 values around the So2% in terms of oxygen content (volume percentage).
Significant relationships were found between P50, 2,3 DPG, Po2 in mixed venous blood, So2% in mixed venous blood, chloride, inorganic phosphates, and hydrogen ion concentrations, according to the equations given in Table 3. No correlation was observed between 2,3 DPG and hemoglobin concentration, or between Pa02 and oxygen saturation. Significant differences, reported in Table 4, were found between plasma ions of cirrhotic patients and of normal subjects: cirrhotic patients had hyperchloremia, hyperphosphatemia, hypocalcemia, and hyponatremia relative to normal subjects.
Although the mean ODC was identical in the two groups (Fig 1), in cirrhotic patients the dispersions of the Po2 values for different levels of So2% were significantly increased, from 20 to 80% saturation. In terms of oxygen transport, the maximal effect was not observed at P50 but at Po2 at 20% of saturation decreasing progressively to Po2 at 45% of saturation (Tables 1, 2; Fig 2). This was revealed by tracing the entire ODC, instead of just measuring the P50, a method that gives more information about the loading and unloading of hemoglobin.” Compared to previously published works, this study was performed on a much larger and more homogenous groups of subjects, both cirrhotic and normal, and this point is essential to allow valid statistical comparisons. Moreover, our cirrhotic patients were in a stable condition and did not have any other significant diseases.

Figure-1

Figure 1. ODC in 50 cirrhotic patients in stable condition who are candidates for liver transplantation and in 50 age- and gender-matched healthy nonsmoking subjects. The mean ODCs are the same in cirrhotic patients and in control subjects. The dispersion (1.96 X SD) of the Po2 values for a given level of oxygen saturation is significantly higher in cirrhotic patients (dotted lines) than in control subjects (shaded area), at least from 20 to 80% saturation.

Figure-2

Figure 2. Po2 vs oxygen content ([O2] vol%). The dotted lines illustrate the calculations developed in Table 2.

Table 1—SD of the Po2 Values for 11 levels of So2% and Related Indices

Variables, mm Hg SD of the Po2 Values, p Value
IControl Subjects (n = 50) ICirrhotic Patients (n = 50)
So2%
5 1.0 1.1 NS
10 1.0 1.3 ns
20 1.0 1.7 < 0.001
30 1.0 1.9 < 0.0001
40 1.1 1.9 < 0.001
50 1.2 2.1 < 0.001
60 1.4 2.5 < 0.0001
70 1.7 2.9 < 0.001
80 2.2 3.4 < 0.01
90 4.0 4.3 ns
95 8.3 10.5 ns
Hemoglobin, g/dL 14.4 (2.7) 10.5 (1.4) < 0.0001
Carboxyhemoglobin, % 1.7 (0.7) 1.9 (1.4) ns
2,3 DPG, |xmol/gHb 16.4 (4.1) 12.5 (2.7) < 0.0001
Pao2, mm Hg 88(5) 56(7) < 0.0001
Paco2, mm Hg 38(2) 33(3) < 0.0001
Blood oxygen content, volume % 19.5 (1.2) 13.0 (2.0) < 0.0001
Hydrogen ion concentration, nmol/L 36.3 (2.6) 34.2 (2.7) < 0.001

Table-2

Table 3—Significant Relationships Between P50, 2,3-DPG, Hydrogen Ions, Mixed Venous Oxygen Pressure and Saturation, Chloride, and Phosphates

P50 (mm Hg) = 21.92 + 0.28 X 2,3 DPG (^mol/gHb; p < 0.001)t
2,3 DPG (^mol/gHb) = 28.1 – 0.31 X H+ (nmol/L; p < 0.00001)
Pvo2 (mm Hg) = 58.5 – 1.0 X 2,3 DPG (^mol/gHb; p < 0.00001)
Svo2 (%) = 21.3 – 0.07 X 2,3 DPG (^mol/gHb; p< 0.00001)
P50 (mm Hg) = 7.11 + 0.14 X Cl (mEq/L;
p< 0.001) + 0.36 X Pi (mEq/L; p< 0.05) + 0.25 X 2,3
DPG (^mol/gHb; p < 0.00002)

Table 4—Significant Differences Between Plasma Ions in Cirrhotic Patients and Normal Subjects

Ions, mEq/L Cirrhotic Patients Normal Subjects
Chloride 105.0 ± 4.0 100.0 ± 4.3 (p < 0.0001)
Inorganic phosphate 3.1 ± 0.3 1.9 ± 1.2 (p < 0.0001)
Potassium 4.0 ± 0.5 4.3 ± 0.3 (p < 0.005)
Sodium 136.0 ± 6.0 142.0 ± 3.5 (p < 0.0001)
Calcium 1.8 ± 0.3 2.2 ± 0.2 (p < 0.0001)
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