Cardiovascular effects of acute changes in extracellular ionized calcium concentration induced by citrate and CaCl2 infusions in conscious, chronically instrumented dogs and their interactions with ganglionic blockade

Arterial Hypertension, Metabolic Syndrome and Subclinical Cardiovascular Organ Damage in Patients with Asymptomatic Primary Hyperparathyroidism before and after Parathyroidectomy: Preliminary Results

Background. Primary hyperparathyroidism (PHPT) is associated with high cardiovascular morbidity, and the role of calcium and parathyroid hormone is still controversial. Objective. To evaluate the prevalence and outcomes of metabolic syndrome, hypertension, and some cardiovascular alterations in asymptomatic PHPT, and specific changes after successful parathyroidectomy. Material and Methods. We examined 30 newly diagnosed PHPT patients (8 males, 22 females; mean age 56 ± 6 yrs), 30 patients with essential hypertension (EH) (9 males, 21 females; mean age 55 ± 4), and 30 normal subjects (NS) (9 males, 21 females: mean age 55 ± 6). All groups underwent evaluation with ambulatory monitoring blood pressure, echocardiography, and color-Doppler artery ultrasonography and were successively revaluated after one year from parathyroidectomy. Results. PHPT patients presented a higher prevalence of metabolic syndrome (38%) with respect to EH (28%). Prevalence of hypertension in PHPT was 81%, and 57% presented altered circadian rhythm of blood pressure, with respect to EH (35%) and NS (15%). PHPT showed an important myocardial and vascular remodelling. During follow-up in PHPT patients, we found significant reduction of prevalence of metabolic syndrome, blood pressure, and "non-dipping phenomenon." Conclusions. Cardiovascular and metabolic alterations should be considered as added parameters in evaluation of patients with asymptomatic PHPT.

Maximum acceptable infusion rate of citrate: relationship between blood ionized calcium levels and cardiovascular effects in anesthetized rats

BACKGROUND & AIMS

Citrate is a useful chemical as a stabilizer for infusion solutions. However, cardiovascular depression associated with ionized hypocalcemia has been observed during massive transfusion of citrated blood products. The goal of the present study was to determine the maximum acceptable infusion rate of citrate and safe blood ionized calcium (Ca(2+)) levels.

METHODS

Citrate was administered intravenously to anesthetized rats at infusion rates between 0.5 and 2.0 mmol/kg/h for 4 h. Changes in heart rate (HR), arterial blood pressure, and the concentrations of plasma citrate and blood Ca(2+) were measured.

RESULTS

Infusion of citrate caused decreases in arterial blood pressure and HR, but no severe cardiovascular depression was observed at infusion rates up to 1.0 mmol/kg/h. Plasma citrate levels reached a steady state within 1 h after the start of infusion at up to 1.0 mmol/kg/h. The concentrations of plasma citrate and blood Ca(2+) were 1.35 and 0.89 mmol/l, respectively, 4h after the start of infusion at 1.0 mmol/kg/h.

CONCLUSIONS

The maximum acceptable infusion rate of citrate was 1.0 mmol/kg/h in anesthetized rats, and no severe cardiovascular effects were observed when the blood Ca(2+) level was 0.89 mmol/l or above.

Effects of calcium chloride on grafted internal mammary artery flow after cardiopulmonary bypass

OBJECTIVE

To examine the effects of calcium chloride (CaCl2) administration on blood flow through the grafted left internal mammary artery (IMA) after cardiopulmonary bypass (CPB).

DESIGN

Single-arm prospective study.

SETTING

University-affiliated hospital operating room.

PARTICIPANTS

Twenty adult patients scheduled for coronary artery bypass graft surgery with IMA graft.

INTERVENTIONS

IMA flow was measured noninvasively with a laser Doppler flow probe placed around the IMA, and measurements were recorded for 10 seconds and averaged. After separation from CPB under stable hemodynamics, baseline IMA flow was measured. CaCl2, 15 mg/kg, was administered intravenously over 1 minute. Blood pressure, left atrial pressure, heart rate, and IMA flow were then measured at 1, 5, and 10 minutes. Coronary perfusion pressure and IMA vascular resistance were calculated.

MEASUREMENTS AND MAIN RESULTS

After CaCl2 administration, IMA blood flow significantly decreased from baseline at 1, 5, and 10 minutes (from 28+/-9 mL/min to 19+/-8 mL/min, 22+/-6 mL/min, and 25+/-4 mL/min), with gradual return toward baseline over time. Blood pressure, coronary perfusion pressure, and IMA vascular resistance significantly increased at 1 and 5 minutes after CaCl2. Left atrial pressure and heart rate remained unchanged. No systolic regional wall motion abnormalities were detected on transesophageal echocardiography.

CONCLUSIONS

CaCl2, administered as a bolus dose after separation from CPB, transiently but significantly reduces IMA flow and can potentially trigger vasospasm, increasing the risk for myocardial ischemia or infarction in susceptible patients. Further studies are needed to determine whether this effect also occurs with nitrosodilators or phosphodiesterase inhibitors.

Effect of calcium chloride and 4-aminopyridine therapy on desipramine toxicity in rats

BACKGROUND

Hypotension is a major contributor to mortality in tricyclic antidepressant overdose. Recent data suggest that tricyclic antidepressants inhibit calcium influx in some tissues. This study addressed the potential role of calcium channel blockade in tricyclic antidepressant-induced hypotension.

METHODS

Two interventions were studied that have been shown previously to improve blood pressure with calcium channel blocker overdose. CaCl2 and 4-aminopyridine. Anesthetized rats received the tricyclic antidepressant desipramine IP to produce hypotension, QRS prolongation, and bradycardia. Fifteen min later, animals received CaCl2, NaHCO3, or saline. In a second experiment, rats received tricyclic antidepressant desipramine IP followed in 15 min by 4-aminopyridine or saline.

RESULTS

NaHCO3 briefly (5 min) reversed hypotension and QRS prolongation. CaCl2 and 4-aminopyridine failed to improve blood pressure. The incidence of ventricular arrhythmias (p = 0.004) and seizures (p = 0.03) in the CaCl2 group was higher than the other groups.

CONCLUSION

The administration of CaCl2 or 4-aminopyridine did not reverse tricyclic antidepressant-induced hypotension in rats. CaCl2 therapy may possibly worsen both cardiovascular and central nervous system toxicity. These findings do not support a role for calcium channel inhibition in the pathogenesis of tricyclic antidepressant-induced hypotension.

Hemodynamic interactions when combining verapamil, acute changes in extracellular ionized calcium concentration and enflurane, halothane or isoflurane in chronically instrumented dogs

To assess the hemodynamic interactions when combining verapamil, acute changes in extracellular ionized calcium concentration [Ca2+] and enflurane (2.5%), halothane (1.2%) or isoflurane (1.6%), seven dogs were chronically instrumented to measure heart rate (HR), aortic, left atrial and left ventricular (LV) pressures, and cardiac output (CO). [Ca2+] was lowered 0.35 mmol.l-1 by citrate infusion and then increased 0.35 mmol.l-1 above control level by CaCl2 infusions. Verapamil was infused at 3 micrograms.kg-1 x min-1 (loading dose 200 (awake), 150 (isoflurane) or 100 (enflurane and halothane) micrograms.kg-1), giving mean verapamil concentrations around 75 (range of means: 66-84 ng.ml-1). Verapamil produced mostly minor changes in the cardiovascular effects of changing [Ca2+] in both awake and anesthetized dogs, indicating mostly additive effects. Verapamil induced a decrease in HR at high [Ca2+] and abolished an increase in mean aortic pressure at both low and high [Ca2+] awake. Verapamil exaggerated the decrease in CO and stroke volume (SV) induced by low [Ca2+] during enflurane anesthesia and abolished the increase in CO induced by low [Ca2+] and exaggerated the increase in SV and LV dP/dtmax induced by high [Ca2+] during halothane anesthesia.