Frontiers in veterinary science2026; 13; 1789443; doi: 10.3389/fvets.2026.1789443

Feasibility and safety of repeated 23% hypertonic saline boluses for electrical impedance tomography contrast enhancement in anaesthetised horses.

Smith, K
·
Raisis, A
·
Moreno-Martinez, F
·
Byrne, D
·
Mosing, M

Abstract: Hypertonic saline (HS) has been used to enhance electrical impedance tomography (EIT) cardiac-related signals associated with pulmonary perfusion in other species, but its suitability and physiological effects in horses are unknown. This exploratory study aimed to determine whether intravenous administration of 100 mL of 23% HS produces a detectable change in thoracic impedance in anaesthetised horses, and to evaluate the physiological effects of repeated bolus administration. Six adult horses were anaesthetised twice using total intravenous anaesthesia. Hypertonic saline 23% was administered via a jugular catheter every 15 min (T15-T60). End-expiratory lung impedance (EELI), tidal impedance variation (TIV), heart rate (HR), and mean arterial pressure (MAP) were recorded at pre-injection, post-injection and end-sample timepoints. Plasma sodium (Na) and chloride (Cl) concentrations were measured before each injection and 15 minutes after the final injection (T75), while urinary fractional excretion (FE) was calculated at T15 and T75. Changes over time were assessed using repeated-measures ANOVA, and FE was compared using paired t-tests. Following HS injection, there was a significant decrease in EELI ( < 0.01), and unanticipated haemodynamic effects were observed, including a significant decrease in MAP ( < 0.01) and increase in HR ( < 0.01), with hypotension (MAP below 70 mmHg) occurring in 62% of post-injection measurements. TIV decreased significantly ( = 0.02), and alterations in breathing pattern occurred in 24/47 post-injection sample times, including transient tachypnoea, expiratory pauses, and crown-like breaths. Plasma Na and Cl increased significantly over time (both < 0.01), and FE of Na and Cl increased between T15 and T75 ( = 0.01 and = 0.02, respectively). Injection of 100 ml of 23% HS reduced EELI, supporting potential use for enhancing perfusion-related EIT signals. Repeated boluses produced clinically relevant decreases in MAP. Concurrent changes in TIV and breathing pattern may complicate interpretation of EIT-derived ventilation-perfusion relationships. Accordingly, repeated 23% HS boluses cannot currently be recommended for EIT contrast enhancement in horses. Further work is required to determine whether single-bolus or lower-concentration protocols provide adequate signal enhancement with less physiological disturbance.

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Publication Date: 2026-06-15 PubMed ID: 42375514PubMed Central: PMC13310722DOI: 10.3389/fvets.2026.1789443Google Scholar: Lookup

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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

This study investigated whether giving repeated doses of highly concentrated saline (23% hypertonic saline) is safe and effective for improving heart and lung imaging signals in anaesthetised horses using electrical impedance tomography (EIT).
The research focused on both the detectability of imaging changes and the physiological effects on the horses, such as blood pressure and breathing patterns, after multiple saline injections.

Background

Electrical impedance tomography (EIT) is a non-invasive imaging technique that monitors lung ventilation and blood perfusion by measuring electrical impedance changes across the thorax.
Previous research in other species showed that hypertonic saline (HS) injections can enhance cardiac-related signals in EIT by temporarily altering thoracic impedance, improving the assessment of pulmonary perfusion.
In horses, the effects of HS on EIT signals and the safety of repeated injections had not been evaluated before this study.

Study Objectives

To determine if a 100 mL intravenous bolus of 23% hypertonic saline produces a measurable change in thoracic impedance in anaesthetised horses.
To evaluate the physiological effects, including cardiovascular and respiratory parameters, of repeated HS bolus administrations every 15 minutes over a one-hour period.

Methods

Six adult horses were anaesthetised twice using total intravenous anaesthesia.
Intravenous 23% hypertonic saline (100 mL) was administered via jugular catheter every 15 minutes from 15 to 60 minutes (time points T15 to T60).
Measurements taken included:
- End-expiratory lung impedance (EELI) – baseline lung impedance at end of exhalation.
- Tidal impedance variation (TIV) – changes in impedance during a normal breath.
- Heart rate (HR) and mean arterial pressure (MAP) – key cardiovascular parameters.
- Blood plasma sodium (Na) and chloride (Cl) concentrations before each injection and 15 minutes after last injection (T75).
- Urinary fractional excretion (FE) of Na and Cl at T15 and T75 to assess renal processing of electrolytes.
Data were analyzed using repeated measures ANOVA to assess changes over time, and paired t-tests compared FE values.

Key Findings

After HS injection, there was a significant decrease in EELI (p < 0.01), indicating the saline altered thoracic impedance and thus enhanced perfusion-related signals in EIT.
TIV significantly decreased (p = 0.02), suggesting changes in ventilation dynamics.
Unanticipated haemodynamic effects included:
- A significant decrease in mean arterial pressure (MAP; p < 0.01), with 62% of post-injection readings showing hypotension (MAP < 70 mmHg).
- An increase in heart rate (HR; p < 0.01), likely compensatory response to hypotension.
Breathing pattern alterations were frequent (24 out of 47 post-injection time points), including:
- Transient rapid breathing (tachypnoea).
- Expiratory pauses.
- “Crown-like” breaths, a specific abnormal breathing pattern.
Plasma sodium and chloride concentrations rose significantly over time (both p < 0.01), confirming systemic electrolyte changes from HS administration.
The fractional excretion of Na and Cl increased between early (T15) and late (T75) time points, indicating increased renal excretion of these ions in response to HS.

Interpretation and Implications

The reduction in end-expiratory lung impedance confirms that 23% hypertonic saline injections can enhance cardiac-related EIT signals, supporting its potential utility as a contrast agent for pulmonary perfusion imaging in horses.
However, repeated high-concentration HS boluses caused significant and clinically relevant decreases in arterial blood pressure, which may pose safety concerns during anaesthesia.
The concurrent decrease in tidal impedance variation and the observed alterations in breathing patterns complicate interpretation of ventilation-perfusion relationships derived from EIT measurements after repeated HS boluses.
Due to these adverse physiological effects, repeated 23% HS bolus injections currently cannot be recommended for contrast enhancement in equine EIT studies.

Recommendations for Future Research

Further studies should investigate whether administration of a single bolus or lower concentrations of hypertonic saline could provide sufficient EIT signal enhancement with fewer cardiovascular and respiratory side effects.
Exploration of alternative contrast agents or imaging protocols may also be necessary to optimize safe and effective EIT usage for pulmonary perfusion imaging in horses.

Cite This Article

APA

Smith K, Raisis A, Moreno-Martinez F, Byrne D, Mosing M. (2026). Feasibility and safety of repeated 23% hypertonic saline boluses for electrical impedance tomography contrast enhancement in anaesthetised horses. Front Vet Sci, 13, 1789443. https://doi.org/10.3389/fvets.2026.1789443

Publication

Frontiers in veterinary science

ISSN: 2297-1769

NlmUniqueID: 101666658

Country: Switzerland

Language: English

Volume: 13

Pages: 1789443

PII: 1789443

Researcher Affiliations

Smith, Kieran

Murdoch University School of Veterinary and Life Sciences, Perth, WA, Australia.

Raisis, Anthea

Murdoch University School of Veterinary and Life Sciences, Perth, WA, Australia.

Moreno-Martinez, Fernando

Murdoch University School of Veterinary and Life Sciences, Perth, WA, Australia.

Byrne, David

Murdoch University School of Veterinary and Life Sciences, Perth, WA, Australia.

Mosing, Martina

Anaesthesiology and Intensive Care, Clinical Centre for Small Animal Health and Research, Clinical Department for Small Animals and Horses, University of Veterinary Medicine Vienna, Vienna, Austria.

Conflict of Interest Statement

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author MM declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.

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