Furosemide Administration Affects Mineral Excretion in Exercised Thoroughbreds

Abstract

This publication is a compilation of all Research Abstracts presented at the Ninth International Conference on Equine Exercise Physiology. Unlike previous ICEEP conferences there will not be a conference proceedings of full length manuscripts. These abstracts succinctly summarise a wide array of investigations relevant to the equine athlete, and will be useful to veterinarians and others involved in management of horses used for sport, work and competition. The abstracts encompass the topics of Applied Physiology; Biochemistry, Haematology, Endocrinology, and Thermoregulation; Cardiovascular and Respiratory; Muscle and Bone; Nutrition; Genomics, Proteomics, and Metabolomics; Biomechanics and Locomotion; as well as Physiotherapy, Rehabilitation, and Equitation science.The International Committee of ICEEP publishes these abstracts so that the most recent scientific information is available to a wide audience, including veterinarians, physiotherapists, trainers, owners and riders.The Introduction:The ability to accurately assess equine oxygen consumption (VO2) under field conditions has been limited by the need for unrestricted gas exchange.Methods: Two variations of a mask and an associated electronics control module (ECM) were designed to enable breath-by-breath measurement of airflows with two 8.0 cm diameter pneumotachometers located 7.5 cm in front of each narus and connected to differential pressure transducers mounted on the outside of the mask. The ECM was comprised of electronics for signal filtering to the flow transducers, an oxygen sensing cell, and an analog-to-digital converter all powered by a lithium-ion battery. The battery also powered a pump connected to gas sampling ports between the nares and pneumotachometers. Airflow and oxygen content of inspired and expired gases were recorded through the ECM and electronically transferred to a notebook. VO2 was determined from these recordings by an operator using a customized software analysis program. One mask encased the lower head (E). The other left the jaw free so horse could wear a bit and be ridden (R). Multiple treadmill exercise tests were undertaken by 6 horses to measure VO2max and blood gases. Each mask was worn twice and results compared to those from an open flow-through system (O) by 2-way RMANOVA (P<0.05). Utility of the system was evaluated using the intraclass correlation coefficient of 4 independent raters.Results: Blood gases and VO2max (152.0 ± 4.0 (mean ± SEM; O), 147.7 ± 4.3 (E), 150.7 ± 3.3 (R) ml/(kg.min) were not different between masks. VO2 measures were reproducible for each mask. Agreement between the 4 raters was excellent (intraclass correlation coefficient = 0.99). Conclusions:Masks capable of measuring VO2 during field exercise were developed, tested and found accurate by multiple users.Ethical Animal Research: Studies performed were approved by the Institution's Animal Care and Use Committee (protocol #3807). Sources of funding: Institutional sources. Competing interests: Washington State University has filed notice of i...

Furosemide administration results in a transient alteration in calcium balance in mature horses

“…While this hay was low in Ca 2+ , it still met the horses’ Ca 2+ requirements as they were all mature and sedentary prior to and during the study. Despite changes to amount of hay fed, CON Ca 2+ balance remained stable and right around zero with no differences among days, but FUR Ca 2+ balance was more negative on day 1 than later in the collection period which agreed with results from Pagan et al (2013, 2014). As mentioned previously, furosemide administration increases mRNA expression for ion‐specific transporters.…”

“…Freestone et al (1988) used a fluorescence‐based calcium analyser which can produce values much lower than those reported on the same samples with an atomic absorption spectrophotometer (Rodgerson & Moran, 1968). Values from Pagan et al (2013, 2014) were closer to those in the current study, but urine may not have been acidified at the same rate which can influence analysis (O’Connor‐Robison & Nielsen, 2006). However, pre‐administration values matched those reported for CON in this study (4.3 ± 0.1 g), so the acidification rate used in the current study likely ensured that more of the urinary Ca 2+ precipitate post‐administration was in solution and produced larger values.…”

“…Calculating from mEq/l, Freestone et al (1988) reported urinary Ca 2+ losses around 2.6 g after furosemide administration. In unpublished data shared in a personal communication from Pagan et al (2013, 2014), total urinary Ca 2+ excretion was 6.1 ± 0.6 g 24 hr post‐furosemide administration and remained above this value 72 hr post‐administration (6.9 ± 0.5 g). Differences in values from the current study and previous research may come from differences in handling methods and analysis.…”

“…In horses, Ca 2+ increases in the urine after furosemide administration (Freestone, Carlson, Harrold, & Church, 1988; Tobin, Roberts, Swerczek, & Crisman, 1978). While this Ca 2+ loss slows as the horse metabolizes the drug, the losses are so great that furosemide negatively impacts Ca 2+ balance for at least 72‐hr post‐administration (Pagan et al, 2013; Pagan, Waldridge, Whitehouse, Fuchs, & Goff, 2014). However, these previous studies did not determine when Ca 2+ balance returned to baseline nor did the researchers propose a potential mechanism to restore Ca 2+ balance after furosemide‐induced losses.…”

Science in brief: Highlights from the applied physiology, muscle and genetics abstracts at the International Conference on Equine Exercise Physiology

“…Two studies reported at ICEEP 9 examined the implications of furosemide administration in TB horses: furosemide induced a linear dose‐dependent increase in plasma total CO 2 concentration to near the threshold value used for screening of prerace administration of alkalising agents . A second study showed that a single dose of furosemide increased urinary and faecal mineral excretion (Ca, P, Na, Cl) and affected calcium balance for 72 h .…”