title: Errors in calculated oncotic pressure of dog plasma.
abstract: Several equations to calculate plasma oncotic pressure (pi) from the total protein concentration (C) have been previously described. These equations were derived empirically from samples with a wide range of C obtained by diluting or concentrating normal plasma samples. To test these equations over a range of naturally occurring C, we measured C and pi of plasma samples from 40 dogs. C ranged from 5.3 to 8.7 g/dl and averaged 6.5 +/- 0.1 (mean +/- SE) and pi averaged 17.9 +/- 0.3 mmHg. The regression equation was pi = 78.14 + 1.67 C (r = 0.74). pi increased with C much less than predicted with the commonly used equations. The albumin-to-globulin concentration ratios (A/G), determined in 27 of the dogs, decreased with increasing C (A/G = 1.56-0.128 C, r = 0.62). The lower A/G at the higher C's could cause the lower than predicted increase in pi with C, because the equations were developed from data in which A/G was constant.
mesh_terms: D000818:Animals; D001794:Blood Pressure; D001798:Blood Proteins / Q000032:analysis*; D004285:Dogs; D009997:Osmotic Pressure; D012709:Serum Albumin / Q000032:analysis; D012712:Serum Globulins / Q000032:analysis
chemical_list: D001798:Blood Proteins; D012709:Serum Albumin; D012712:Serum Globulins