Effect of clenbuterol on tracheal mucociliary transport in horses undergoing simulated long-distance transportation

BACKGROUND

Pneumonia is observed in horses after long-distance transportation in association with confinement of head position leading to reduction in tracheal mucociliary clearance rate (TMCR).

HYPOTHESIS/OBJECTIVES

Clenbuterol, a beta-2 agonist shown to increase TMCR in the horse, will ameliorate the effects of a fixed elevated head position on large airway contamination and inflammation in a model of long-distance transportation model.

ANIMALS

Six adult horses.

METHODS

A cross-over designed prospective study. Horses were maintained with a fixed elevated head position for 48 hours to simulate long-distance transport, and treated with clenbuterol (0.8 μg/kg PO q12h) or a placebo starting 12 hours before simulated transportation. TMCR was measured using a charcoal clearance technique. Data were collected at baseline and 48 hours, and included TMCR, tracheal wash cytology and quantitative culture, rectal temperature, CBC, fibrinogen, and serum TNFα, IL-10, and IL-2 levels. There was a 18-21 day washout between study arms, and data were analyzed using regression analysis and Wilcoxon rank-sum tests.

RESULTS

Tracheal mucociliary clearance rate was significantly decreased after transportation in both treatment (P = .002) and placebo (P = .03) groups. There was a significant effect of treatment on TMCR, with the treatment group showing half the reduction in TMCR compared with the placebo group (P = .002). Other significant differences between before- and after-transportation samples occurred for serum fibrinogen, peripheral eosinophil count, quantitative culture, tracheal bacteria, and degenerate neutrophils, though no treatment effect was found.

CONCLUSIONS AND CLINICAL IMPORTANCE

Treatment with clenbuterol modestly attenuates the deleterious effects of this long-distance transportation model on tracheal mucociliary clearance.

Comparison of water manometry to 2 commercial electronic pressure monitors for central venous pressure measurement in horses

BACKGROUND

Central venous pressure (CVP) customarily has been measured in veterinary patients with water manometry. However, many institutions are now using stallside electronic monitors in both anesthesia and intensive care units for many aspects of patient monitoring.

HYPOTHESIS

Electronic stall side monitoring devices will agree with water manometry for measurement of CVP in horses.

ANIMALS

Ten healthy adult horses from the university research herd.

METHODS

Central venous catheters were placed routinely, and measurements were obtained in triplicate with each of the 3 methods every 12 hours for 3 days. Data were analyzed by a Lin concordance correlation coefficient and modified Bland-Altman limits of agreement, with all devices compared pairwise.

RESULTS

Compared with water manometry, agreement (bias) of the Passport was -1.94 cmH₂O (95% limits of agreement, -8.54 to 4.66 cmH₂O) and of the Medtronic was -1.83 cmH₂O (95% limits of agreement, -8.60 to 4.94 cmH₂O). When compared with the Passport, agreement of the data obtained with the Medtronic was 0.27 cmH₂O (95% limits of agreement, -4.39 to 4.93 cmH₂O).

CONCLUSIONS AND CLINICAL IMPORTANCE

These data show that both electronic monitors systematically provide measurements that are approximately 2 cmH₂O lower than water manometry, but differences between the 2 electronic devices are small enough (< 0.5 cmH₂O) to be considered clinically unimportant. This discrepancy should be taken into account when interpreting data obtained with these monitoring devices.

The effects of hypohydration on central venous pressure and splenic volume in adult horses

BACKGROUND

Central venous pressure (CVP) is used in many species to monitor right-sided intravascular volume status, especially in critical care medicine.

HYPOTHESIS

That hypohydration in adult horses is associated with a proportional reduction in CVP.

ANIMALS

Ten healthy adult horses from the university teaching herd.

METHODS

In this experimental study, horses underwent central venous catheter placement and CVP readings were obtained by water manometry. The horses were then deprived of water and administered furosemide (1 mg/kg IV q6h) for up to 36 hours. Weight, CVP, vital signs, PCV, total protein (TP), and serum lactate were monitored at baseline and every 6 hours until a target of 5% decrease in body weight loss was achieved. The spleen volume was estimated sonographically at baseline and peak volume depletion. Linear regression analysis was used to assess the association of CVP and other clinical parameters with degree of body weight loss over time.

RESULTS

There was a significant association between CVP and decline in body weight (P < .001), with a decrease in CVP of 2.2 cmH(2)O for every percentage point decrease in body weight. Other significant associations between volume depletion and parameters measured included increased TP (P = .007), increased serum lactate concentration (P = .048), and decreased splenic volume (P = .046). There was no significant association between CVP and vital signs or PCV.

CONCLUSIONS AND CLINICAL IMPORTANCE

These findings suggest that CVP monitoring might be a useful addition to the clinical evaluation of hydration status in adult horses.

Prostaglandin-H synthase-1 (PGHS-1) gene is expressed in specific neurons of the brain of the late gestation ovine fetus

Prostaglandin (PG) E2 acts on the brain stem to modulate breathing activity in the ovine fetus. The source of this PGE2 is unknown and we hypothesized that it is produced locally in the developing brain and functions in a paracrine and/or autocrine manner. The purpose of the present study was to establish whether prostaglandin-H synthase-1 (PGHS-1), a crucial enzyme in de novo prostaglandin synthesis, is present and its gene expressed in the ovine fetal brain. Immunohistochemical and molecular hybridization techniques were used to identify sites of PGHS-1 immunoreactivity and PGHS-1 mRNA expression respectively in the brain of the ovine fetus in late gestation (approximately 126 days gestation, term 145 days). PGHS-1 immunoreactivity was localized to specific regions of the fetal brain, including the cortex, hypothalamus, hippocampal formation, superior colliculus of the midbrain, parabrachial nucleus of the pons, and the reticular formation, raphe, nucleus of the solitary tract, and gracile and cuneate nuclei of the medulla. The relative abundance of PGHS-1 mRNA in selected brain regions, as determined by Northern blot analysis, correlated qualitatively with the number of PGHS-1 immunoreactive neurons identified in each region. In situ hybridization demonstrated PGHS-1 mRNA to be localized in the same neurons or nuclei as PGHS-1 immunoreactivity. These results indicate that PGHS-1 synthesized de novo in many brain regions including two that are important in respiratory control: the pneumotaxic center (parabrachial nucleus) and the dorsal respiratory group (nucleus tractus solitarius) suggesting that prostaglandins that modulate fetal respiratory activity are synthesized endogenously.

Establishing an outpatient anticoagulation clinic in a community hospital

The establishment of a pharmacist-managed out-patient anticoagulation clinic in a private community hospital is described. Discussions by pharmacy with office-based physicians at a 187-bed, private, nonprofit community medical center indicated that the traditional system of anticoagulation management was not ideal for the physicians or their patients. Development of a pharmacist-managed anticoagulation clinic began in fall 1993; operations began in spring 1994. Planning included analyzing existing practices, reviewing the relevant literature, obtaining physician input, visiting an established anticoagulation clinic, formulating a business plan, and developing clinical protocols. Collaborative relationships were established with the hospital laboratory, business office, and risk management, information services, and medical records departments. Two pharmacists were trained to work in the clinic and provide coverage 24 hours a day. Services include patient assessment, monitoring of anticoagulation, warfarin dosage adjustment, medication management, patient education, follow-up care, and providing feedback to referring and attending physicians. The clinic has met with physician and patient satisfaction, has reduced the number of admissions to treat warfarin-related bleeding, and has been able to cover its direct costs. A pharmacist-managed anti-coagulation clinic was successfully established in a private community hospital.

Cobalt-60: the heart of gamma-radiation sterilization

Currently, more than three million cubic metres of single-use medical devices are sterilized by gamma radiation each year. The wide use of this method of sterilization is a result of the lethal effects of ionizing radiation on microbial populations and the penetrative powers of cobalt-60. This article describes how cobalt-60 is produced and used in gamma-radiation sterilization, and how it is disposed of once it has reached the end of its useful life. Cobalt-60 sources typically have a life of 20 years, at which point they are returned to the suppliers for re-encapsulation, reprocessing, recycling, or disposal.

Prostaglandin E2 in cerebrospinal fluid of fetal and newborn sheep: central versus peripheral source

During the perinatal period, prostaglandin (PG) E2 levels show parallel changes in cerebrospinal fluid (CSF) and blood which may be important for the adaptation of the fetus to extrauterine life. It is not known, however, whether PGE2 in the CSF originates from a local or a peripheral source. Experiments were carried out in term fetal and newborn sheep chronically instrumented with a cannula inside the third ventricle and vascular lines. Indomethacin was given intracerebroventricularly (i.c.v.) (50 or 100 micrograms at hourly intervals), alone or in combination with intravenous (i.v.) PGE2 (1 or 1.5 micrograms/kg/min). In the fetus, i.c.v. indomethacin reduced PGE2 levels in both CSF and plasma. Conversely, no significant change was noted at either site when indomethacin was given i.c.v. to the newborn. At both ages, PGE2 increased in the CSF during i.v. infusion of the compound, but this elevation was proportionately smaller than in plasma. We conclude that, in the perinatal period, brain and peripheral circulation function as separate compartments with respect to PGE2, though there is passage of the compound across the blood-brain barrier. Results provide indirect evidence that perinatal brain produces PGE2 in measurable amounts.