Inhaled furosemide attenuates hyperpnea-induced obstruction and intra-airway thermal gradients

Furosemide impairs nasal mucociliary clearance in humans

Furosemide, a potent diuretic, affects ion and water movement across the respiratory epithelium. However, the effects of furosemide, as clinically used, on mucociliary clearance, a critical respiratory defense mechanism, are still lacking in humans. Fourteen young healthy subjects were assigned to three random interventions, spaced one-week apart: no intervention (control), oral furosemide (40mg), and furosemide+oral volume replacement (F+R). Nasal mucociliary clearance was assessed by saccharine test (STT), and mucus properties were in vitro evaluated by means of contact angle and transportability by sneeze. Urine output and osmolality were also evaluated. Urine output increased and reduced urine osmolality in furosemide and F+R compared to the control condition. STT remained stable in the control group. In contrast, STT increased significantly (40%) after furosemide and F+R. There were no changes in vitro mucus properties in all groups. In conclusion, furosemide prolongs STT in healthy young subjects. This effect is not prevented by fluid replacement, suggesting a direct effect of furosemide on the respiratory epithelium.

Nebulized furosemide for the management of dyspnea: does the evidence support its use?

Dyspnea is a common and distressing symptom associated with multiple chronic illnesses and high levels of burden for individuals, their families and health care systems. The subjective nature dyspnea and a poor understanding of pathophysiological mechanisms challenge the clinician in developing management plans. Nebulized furosemide has been identified as a novel approach to dyspnea management. This review summarizes published studies, both clinical and experimental, reporting the use of nebulized furosemide. The search criteria yielded 42 articles published in the period 1988 to 2004. Although nebulized furosemide appeared to have a positive influence on dyspnea and physiological measurements, caution must be taken with the results primarily coming from small-scale clinical trials or observation trials. Despite the limitations of the studies reported, given the range of conditions reporting effectiveness of nebulized furosemide, further investigation of this potential novel treatment of dyspnea is warranted.

Furosemide inhalation in dyspnea of mustard gas-exposed patients: a triple-blind randomized study

Dyspnea is the hallmark symptom of some respiratory diseases such as chronic obstructive pulmonary disease and bronchiolitis and is a major reason for which these patients seek medical attention. We performed a randomized triple-blind controlled crossover clinical trial in which we compared the efficacy of inhaled furosemide (4 ml equal to 40 mg in 10 min) with placebo (4 ml of 0.9% saline solution) in 41 mustard gas-exposed patients. Dyspnea index, visual analog scale (VAS), and pulmonary function test results were obtained before and 4 h after treatments. Results showed that both furosemide and placebo significantly decreased VAS and dyspnea index and increased FEV(1), FVC, and FEV(1)/FVC, while there was no difference between the two drugs in these effects (p values .23, .61, .81, .36, and .27, respectively). Our results failed to address the previously reported effects of inhaled furosemide on dyspnea. In fact, we suggest that patients with a previous exposure to sulfur mustard, in which chronic bronchitis and bronchiolitis are the most suggested underlying mechanisms, may not benefit from furosemide to alleviate their dyspnea.

Differential effects of furosemide on porcine bronchial arterial and airway smooth muscle

Furosemide attenuates airway obstruction in asthmatic subjects when administered as an aerosol pretreatment. This protective effect of furosemide could be related to relaxation of bronchial smooth muscle or to increased bronchial blood flow. To determine whether furosemide dilates bronchial smooth muscle, isometric contractile responses in distal bronchi from young pigs were studied. In bronchial smooth muscle rings that were precontracted with 10(-5) M acetylcholine, significant relaxation occurred with 10(-8) to 3 x 10(-6) M isoproterenol but not with 10(-8) to 10(-3) M furosemide. In contrast, bronchial arteries that were precontracted with either 10(-4) M norepinephrine or 10(-8) M vasopressin significantly relaxed in response to 10(-4) to 3 x 10(-3) M and 10(-3) to 3 x 10(-3) M furosemide, respectively. We conclude that furosemide, under the described experimental conditions, relaxes airway vascular smooth muscle but not bronchial smooth muscle. These results are consistent with previous suggestions that inhaled furosemide increases blood flow to airway tissues (Gilbert IA, Lenner KA, Nelson JA, Wolin AD, and Fouke JM. J Appl Physiol 76: 409-415, 1994).

Nasal obstruction improvement induced by topical furosemide in subjects affected by perennial nonallergic rhinitis

Inhaled furosemide decreases bronchial response to several physical and chemical irritants. To evaluate the effect of topical furosemide on nasal resistance in patients affected by perennial nonallergic rhinitis, we studied 12 patients. This diagnosis of perennial nonallergic rhinitis was based on the history of rhinorrhea, sneezing, and nasal obstruction, on anterior rhinoscopy and endoscopy, on negative allergic tests, and on the absence of eosinophilia in nasal secretion. The study was performed on two nonconsecutive days. On the first day, one puff (100 microliters) of 0.9% saline was sprayed into both nostrils and nasal resistance was measured by anterior rhinomanometry before the puff and 15 and 30 minutes later. On the second day, one puff (100 microliters) of a solution of furosemide (10 mg/mL) was sprayed into both nostrils and nasal resistance was measured before the puff and 15, 30, 45, 60, 90, 120, and 180 minutes later. Initial nasal resistance was abnormally high in all patients on both days. A slight but significant increase was observed after spraying isotonic saline (base: 1.38 +/- .69; 15 minutes: 1.47 +/- 0.72; 30 minutes: 1.44 +/- 0.73); by contrast a marked decrease was observed after spraying the furosemide solution. Nasal resistance was lowest between 30 and 90 minutes after giving furosemide. Then it progressively increased, but values at 180 minutes were still lower than the initial ones (base: 1.43 +/- 0.67; 15 minutes: 0.70 +/- 0.47; 30 minutes: 0.48 +/- 0.24; 45 minutes: 0.49 +/- 0.21; 60 minutes: 0.50 +/- 0.20; 90 minutes: 0.56 +/- 0.23; 120 minutes: 0.62 +/- 0.32; 180 minutes: 0.67 +/- 0.30). After topical furosemide, all patients had subjective relief of nasal obstruction that lasted more that 12 hours in 9 subjects.

Dilatory effect of furosemide on rat tracheal arterioles and venules

Furosemide pretreatment greatly reduces the severity of an asthmatic response to several types of bronchoconstrictor challenge. Indirect evidence suggests that furosemide exerts its protective effects by dilating the airway vasculature during thermal stress. To test the hypothesis that furosemide dilates airway microvessels, the tracheas of anesthetized rats were surgically exposed and continuously suffused with Krebs Ringer bicarbonate warmed to 37 degrees C. Tracheal adventitial arterioles (13.0 to 41.0 microns initial diameter, n = 47) and venules (50.0 to 99.0 microns initial diameter, n = 46) were visualized with a videomicroscope, and vessel diameters were measured using videocalipers. When vessels were preconstricted with 10(-4) M phenylephrine, a selective alpha 1-adrenergic agonist, and then treated with 10(-4) M furosemide, significant (p < 0.05) dilation was observed in both arterioles (from 64.6 to 79.5% of their initial diameter) and venules (from 52.1 to 65.4% of their initial diameter). When vessels were preconstricted with 10(-4) phenylephrine, after pretreatment with the cyclooxygenase inhibitor indomethacin (5.0 mg/kg), 10(-4) M furosemide significantly dilated arterioles (from 77.5 to 93.0% of their initial diameter) and venules (from 58.5 to 80.1% of their initial diameter). In vessels preconstricted with 10(-3) M L-NAME, an inhibitor of nitric oxide synthesis, addition of 10(-4) M furosemide to the suffusion still caused significant dilation in arterioles, from 77.4 to 88.8% of their initial diameter, and in venules from 79.5 to 86.7% of their initial diameter. These data confirm that furosemide, when applied topically, dilates tracheal arterioles and venules by cyclooxygenase- and nitric oxide-independent mechanisms.

Effect of furosemide on hyperpnea-induced airway obstruction, injury, and microvascular leakage

Furosemide attenuates hyperpnea-induced airway obstruction (HIAO) in asthmatic subjects via unknown mechanism(s). We studied the effect of furosemide on dry air-induced bronchoconstriction, mucosal injury, and bronchovascular hyperpermeability in a canine model of exercise-induced asthma. Peripheral airway resistance (Rp) was recorded before and after a 2-min dry-air challenge (DAC) at 2,000 ml/min. After pretreatment with aerosolized saline containing 0.75% dimethyl sulfoxide, DAC increased Rp 72 +/- 11% (SE, n = 7) above baseline; aerosolized furosemide (10(-3) M) reduced this response by approximately 50 +/- 6% (P < 0.01). To assess bronchovascular permeability, colloidal carbon was injected (1 ml/kg i.v.) 1 min before DAC, and after 1 h, the vehicle- and furosemide-treated airways were prepared for morphometric analysis. Light microscopy confirmed previous studies showing that DAC damaged the airway epithelium and enhanced bronchovascular permeability. Furosemide did not inhibit dry air-induced mucosal injury or bronchovascular hyperpermeability and in fact tended to increase airway damage and vascular leakage. This positive trend toward enhanced bronchovascular permeability in DAC canine peripheral airways is consistent with the hypothesis that furosemide inhibits HIAO in part by enhancing microvascular leakage and thus counterbalancing the evaporative water loss that occurs during hyperpnea.