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Effects of acute hypovolaemia by furosemide on tracheal transepithelial potential difference and mucus in dogs

¹ School of Physiotherapy, São Paulo City University, and Depts of ² Pathology, ³ Anesthesiology, and ⁴ Cardiopneumology, School of Medicine, São Paulo University, São Paulo, Brazil. ⁵ Pulmonary Research Group, Dept of Medicine, University of Alberta, Edmonton, AB, Canada.

CORRESPONDENCE: N.K. Nakagawa, Pulmonary Defense Group, School of Medicine of São Paulo University, Room 1223, Rua Dr. Arnaldo, 455, CEPP:01246-903, São Paulo, SP, Brasil. Fax: 55 1130680072. E-mail: naomikondo@uol.com.br

Keywords: Furosemide, hypovolaemia, mucociliary transport, respiratory mucus, rheology, transepithelial potential difference

Received: February 18, 2004
Accepted June 11, 2004

This work was supported by the São Paulo State Foundation (FAPESP) and the Medical Investigation Laboratory (LIM 5 and LIM 8) of the School of Medicine of São Paulo University.

Furosemide is a potent diuretic that affects water transfer across the respiratory epithelium, which is closely related to the transepithelial potential difference (PD). Water is a critical factor that determines mucus transport; an important lung defence mechanism that removes particles and microorganisms from the respiratory system.

The aim of the present study was to investigate the acute effects of furosemide and hypovolaemia on tracheal PD and mucus properties. A total of 36 male mixed-breed dogs were submitted to anaesthesia, mechanical ventilation and haemodynamic monitoring. They were randomly assigned to three groups consisting of: a control group, a furosemide (40 mg i.v.) + hypovolaemia group, and a furosemide (40 mg i.v.) + volume replacement group. Tracheal PD and mucus samples were collected at time 0, 1 and 2 h after intervention. Mucus properties were analysed by means of a magnetic microrheometer and in vitro mucociliary transportability on the frog palate.

Compared to controls, furosemide decreased PD to intermediate values, and only significantly when associated with hypovolaemia (–13±5 and –8±2 mV, time 0 and 2 h, respectively).

In addition to the direct effect of furosemide, these results indicate that hypovolaemia also affects ion transport in the tracheal membrane. Furosemide and hypovolemia have no acute effects on respiratory mucus properties.