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- Author or Editor: Arnold J. Felsenfeld x
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Objective—To evaluate the effects of metabolic acidosis and changes in ionized calcium (Ca2+) concentration on PaO2 in dogs.
Animals—33 anesthetized dogs receiving assisted ventilation.
Procedure—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 and Clinical Relevance—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.