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Hypercalcemia attenuates blood pressure response to epinephrine
G P Zaloga1, S Willey, D Malcolm
1Department of Anesthesia/Critical Care and Medicine, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina.
The Journal of Pharmacology and Experimental Therapeutics
|December 1, 1988
Summary
Calcium chloride administration blunts epinephrine's hypertensive effects in rats, challenging its clinical use to augment cardiovascular responses. Hypocalcemia did not alter epinephrine's pressor effects, indicating calcium's role in modulating epinephrine action.
Area of Science:
- Pharmacology
- Cardiovascular Physiology
- Critical Care Medicine
Background:
- Epinephrine's alpha and beta adrenergic actions are linked to intracellular calcium.
- Clinicians often co-administer epinephrine with calcium to enhance cardiovascular effects, despite limited evidence.
- The interaction between calcium and epinephrine in modulating blood pressure requires further investigation.
Purpose of the Study:
- To investigate the effects of calcium on epinephrine's pressor response in normal and endotoxin-treated rats.
- To determine if calcium supplementation augments or diminishes epinephrine's hypertensive effects.
- To evaluate the clinical relevance of co-administering calcium and epinephrine.
Main Methods:
- Rats were made hypercalcemic with calcium chloride or hypocalcemic with EGTA.
- Epinephrine was administered in incremental doses (10, 20, 50 micrograms/kg).
- Mean arterial pressure was measured to assess the pressor response to epinephrine under varying calcium levels and in endotoxemic conditions.
Main Results:
- Calcium chloride significantly blunted epinephrine's hypertensive response in normal rats (50% decrease at 50 micrograms/kg EPI).
- In endotoxemic rats, calcium chloride significantly reduced the pressor response to epinephrine across all tested doses (30-73% decrease).
- EGTA-induced hypocalcemia had no significant effect on epinephrine's pressor response in either normal or endotoxemic rats.
Conclusions:
- Calcium chloride administration diminishes the hypertensive effects of epinephrine in both normal and endotoxin-treated rats.
- The common clinical practice of using calcium with epinephrine to augment cardiovascular effects lacks a strong experimental basis.
- Further research is needed to understand the complex interactions between calcium, epinephrine, and cardiovascular regulation, especially in critical illness.