title: Effect of changes in ionized calcium concentration in arterial blood and metabolic acidosis on the arterial partial pressure of oxygen in dogs.
abstract: OBJECTIVE
  To evaluate the effects of metabolic acidosis and changes in ionized calcium (Ca2+) concentration on PaO2 in dogs.
  
  
  METHODS
  33 anesthetized dogs receiving assisted ventilation.
  
  
  METHODS
  Normal acid-base status was maintained in 8 dogs (group I), and metabolic acidosis was induced in 25 dogs. For 60 minutes, normocalcemia was maintained in group I and 10 other dogs (group II), and 10 dogs were allowed to become hypercalcemic (group III); hypocalcemia was then induced in groups I and II. Groups II and IV (5 dogs) were treated identically except that, at 90 minutes, the latter underwent parathyroidectomy. At intervals, variables including PaO2, Ca2+ concentration, arterial blood pH (pHa), and systolic blood pressure were assessed.
  
  
  RESULTS
  In group II, PaO2 increased from baseline value (96 +/- 2 mm Hg) within 10 minutes (pHa, 7.33 +/- 0.001); at 60 minutes (pHa, 7.21 +/- 0.02), PaO2 was 108 +/- 2 mm Hg. For the same pHa decrease, the PaO2 increase was less in group III. In group I, hypocalcemia caused PaO2 to progressively increase (from 95 +/- 2 mm Hg to 104 +/- 3 mm Hg), which correlated (r = -0.66) significantly with a decrease in systolic blood pressure (from 156 +/- 9 mm Hg to 118 +/- 10 mm Hg). Parathyroidectomy did not alter PaO2 values.
  
  
  CONCLUSIONS
  Induction of hypocalcemia and metabolic acidosis each increased PaO2 in anesthetized dogs, whereas acidosis-induced hypercalcemia attenuated that increase. In anesthetized dogs, development of metabolic acidosis or hypocalcemia is likely to affect ventilatory control.
authors.affiliation: Departmento de Medicina y Cirugía Animal, Universidad de Córdoba, Ctra Madrid-Cadiz, km 396, 14014 Córdoba, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Lopez
authors.forename: Arnold J
authors.initials: AJ
authors.lastname: Felsenfeld
authors.forename: Jose C
authors.initials: JC
authors.lastname: Estepa
authors.forename: Mariano
authors.initials: M
authors.lastname: Rodriguez
authors.forename: Escolastico
authors.initials: E
authors.lastname: Aguilera-Tejero
mesh_terms: D000138:Acidosis / Q000097:blood / Q000139:chemically induced / Q000662:veterinary*; D000818:Animals; D002118:Calcium / Q000097:blood*; D004283:Dog Diseases / Q000097:blood* / Q000139:chemically induced; D004285:Dogs; D005260:Female; D008297:Male; D010100:Oxygen / Q000097:blood*; D010313:Partial Pressure; D013997:Time Factors
chemical_list: D010100:Oxygen; D002118:Calcium