Hemodynamic effects of a single dose of dopamine and L-dopa in pulmonary hypertension secondary to chronic obstructive lung disease

Effects of low-dose dopamine on ventilation in patients with chronic obstructive pulmonary disease

BACKGROUND

Dopamine plays an important role in the regulation of respiration and low-dose dopamine infusion is associated with a decreased respiratory drive response to hypoxia in animals and humans. The effects of dopamine on ventilation in patients with chronic obstructive pulmonary disease (COPD) is unknown. We tested the hypothesis that dopamine inhibits ventilation in patients with COPD.

MATERIALS AND METHODS

In a double-blinded, cross-over, placebo-controlled, randomized study we studied nine patients with decompensated COPD, ventilated in the pressure support mode in the intensive care unit (ICU) and five ambulatory patients with stable COPD. All patients received 5 micro g kg(-1) min(-1) of dopamine or an equivalent volume of 5% glucose solution.

RESULTS

In the mechanically ventilated COPD patients, there was no difference in the effects of dopamine compared with placebo on blood pressure, heart rate, minute ventilation (-0.5 +/- 1.1 vs. -0.2 +/- 0.9 L min(-1), P = 0.46, respectively), respiratory rate (-0.4 +/- 2.7 vs. -0.3 +/- 2.1 min(-1), P = 0.96), PaO(2) (-5 +/- 4 vs. -5 +/- 10 mmHg, P = 0.90, respectively), or PaCO(2) (-0.7 +/- 1.4 vs. -1.0 +/- 3.4 mmHg, P = 0.83, respectively). In spontaneously breathing stable patients, dopamine increased systolic blood pressure (P = 0.02) but did not influence other haemodynamic and respiratory variables.

CONCLUSION

Although low-dose dopamine has been shown to depress ventilation in a variety of conditions, it does not compromise ventilation in COPD patients either breathing spontaneously or when weaned using pressure support ventilation.

The actions of dopamine on the airways

BACKGROUND

Dopamine exerts inhibitory and excitatory effects on different systems. In the lungs, dopamine modulates respiratory functions through carotid bodies and modulates pulmonary blood vessel tone, alveolar liquids, and bronchial exchange, and possibly participates in the regulation of airways diameter. It has been reported that dopamine has no acute effect on human airways in normal subjects or those with asthma background. However, inhaled or infused dopamine decreased histamine-induced bronchoconstriction in both normal and asthmatic subjects. We have examined the possible modulating effect of dopamine on bronchial diameter by administering inhaled dopamine and the DA2 dopaminergic blocker metoclopramide to subjects with various degrees of bronchial tone.

METHODS

We examined 56 volunteers. Arterial blood pressure and heart rate were determined in every subject. By means of spirometry, we measured forced vital capacity, forced expiratory volume in the first second, maximal forced expiratory flow, and forced expiratory flow at 50% of vital capacity, before and after each treatment. By inhalation with a nebulizer, we administered dopamine (0.5 microg/kg/min) to 10 healthy subjects, 10 subjects with asthma without acute bronchospasm, and 16 subjects with acute asthma attack; intravenous metoclopramide (7 microg/kg/min) was administered to 10 healthy subjects and 10 subjects with asthma without acute bronchospasm. For ethical reasons, metoclopramide was not used in subjects with acute asthma attack.

STATISTICS

non-parametric Wilcoxon tests for paired samples, ANOVA tests, and Bonferroni multiple comparison tests were performed.

RESULTS

Inhaled dopamine increased forced expiratory volume in the first second, forced vital capacity, maximal forced expiratory flow, and forced expiratory flow at 50% of vital capacity in the acute asthma attack group, but there were no modifications in the healthy group or in the asthma without acute bronchospasm group. Metoclopramide did not induce changes in respiratory parameters in healthy individuals or in those with asthma without acute bronchospasm.

CONCLUSIONS

Inhaled dopamine was able to induce bronchodilatation when the bronchial tone was already increased by acute asthma attack, but it did not modify the resting bronchial tone in normals or in asthmatics without acute bronchospasm. DA2 blockade with metoclopramide did not modify resting bronchial tone either. We suggest that dopamine exerts a modulatory effect on bronchial tone of human airways depending on the degree of existing basal tone.

A randomized crossover trial of levodopa in congestive heart failure

BACKGROUND

The short- and long-term effects of levodopa (L-dopa), an oral dopaminergic prodrug, were assessed in patients with severe left ventricular dysfunction.

METHODS AND RESULTS

Initially, 26 patients were included in the study group. After clinical, radiographic, and radionuclide examination, each patient underwent right heart catheterization (Swan-Ganz thermodilution catheter). Plasma noradrenaline levels were measured. In two patients, a favorable hemodynamic response to L-dopa was not observed, another two required permanent pacemaker implantation. These four patients were excluded from the study. Two patients required permanent pacemaker implantation. The remaining 22 patients with favorable hemodynamic response to L-dopa (increase in cardiac index, stroke volume index, reduction in total systemic resistance) were randomized in a nonblinded fashion to the conventional (11 patients) or conventional plus L-dopa (11 patients) treatment groups. During the study period, two patients, one from each group, died. They were excluded from the analysis. The final analyzed study group consisted of 20 men, aged 33-69, in New York Heart Association functional class IV (9 patients) and III (11 patients). The cause of congestive heart failure was primary dilated cardiomyopathy in 11 patients and ischemic heart disease in 9 patients. After 3 months' treatment, all patients were crossed over. Clinical, radiographic, radionuclide, and hemodynamic evaluation was repeated at the end of the 3-month treatment period. After 3 months of therapy with L-dopa in each group (covariance analysis), there was improvement in clinical, radiographic (relative heart volume, -128 mL/m2), radionuclide (left ventricular ejection fraction, +4.6; right ventricular ejection fraction, +4.8%), hemodynamic (mean pulmonary wedge pressure, -8 mmHg; total systemic resistance, -1.8 Wu; total pulmonary resistance, -3.5 Wu), and neurohumoral (noradrenaline, -218 pg/mL) measures.

CONCLUSIONS

The addition of L-dopa to conventional therapy has beneficial short- and long-term effects in patients with severe left ventricular dysfunction.

Low-dose dopamine in severe right heart failure and chronic obstructive pulmonary disease

OBJECTIVE

To describe the beneficial effects of low-dose dopamine infusion (2-5 micrograms/kg/min) in a patient with severe cor pulmonale complicating chronic obstructive pulmonary disease (COPD).

CASE SUMMARY

A 53-year-old woman with severe cor pulmonale and generalized edema complicating COPD received low-dose dopamine to stabilize blood pressure and, perhaps, improve cardiac output. Low-dose dopamine also improved her renal function and enhanced the diuretic response to furosemide therapy.

DISCUSSION

Previous studies of dopamine in such patients were reviewed. Both dopamine infusion (4 micrograms/kg/min) and oral administration of its precursor, L-dopa, can increase the cardiac output, decrease pulmonary vascular resistance, and enhance oxygen delivery in patients who are stable with cor pulmonale secondary to COPD. In patients with COPD during acute respiratory failure, high-dose dopamine (10 micrograms/kg/min) has been shown to increase the diaphragmatic blood flow and contraction. Low-dose dopamine also has been reported to be useful in patients with congestive heart failure or cirrhosis of the liver.

CONCLUSIONS

Low-dose dopamine is useful in the acute management of patients with severe cor pulmonale complicating COPD because of the drug's beneficial effects on blood pressure, cardiac output, renal perfusion, natriuresis, and diuresis. Low-dose dopamine also may enhance the natriuretic and diuretic response to loop diuretics, decrease pulmonary vascular resistance, and enhance oxygen delivery.

Right ventricular dysfunction in chronic obstructive pulmonary disease. Evaluation and management

Cor pulmonale is an important consequence of COPD. Although the incidence is not precisely known, it is seen more frequently in patients with hypoxemia, CO2 retention and severely reduced FEV1. When present, it limits peripheral oxygen delivery, increases shortness of breath, and reduces exercise endurance. It is also associated with higher mortality rates independent of other prognostic variables. Numerous factors may contribute to the development of cor pulmonale in patients with COPD, but its primary cause is chronic alveolar hypoxia resulting in pulmonary vasoconstriction, vascular remodeling and pulmonary hypertension. The physical exam, chest radiograph and ECG may be helpful in detecting the presence of cor pulmonale, but because of anatomic changes that occur in the chest, these tests are often insensitive in patients with COPD. Noninvasive diagnostic techniques utilizing Doppler echocardiography and radionuclide angiography allow for detection of RV dysfunction at an earlier stage and in most cases, preclude the need for right heart catheterization. LTO2 is the only therapy shown to improve survival in patients with COPD. However, statistical proof correlating improvements in pulmonary hemodynamics with increased survival is lacking. Bronchodilators, such as the beta 2 agonists and especially theophylline, may have beneficial effects on pulmonary hemodynamics in addition to their effect on respiratory function and are useful in COPD when RV dysfunction is present. Diuretics and phlebotomy are also useful in improving symptoms in appropriate patients. Vasodilators such as calcium channel blockers and ACE-inhibitors may improve pulmonary hemodynamics acutely, but may lower arterial PO2 by worsening ventilation-perfusion matching or blunt the improvement in pulmonary hemodynamics seen with supplemental oxygen. The long-term benefits of these agents have not been proven and their routine use in patients with cor pulmonale due to COPD cannot be recommended.