Background: The bedside diagnosis of acute pulmonary edema is challenging. This study evaluated the breath-by-breath information from electrical impedance tomography (EIT), respiratory mechanics and volumetric capnography (VCap) to assess acute pulmonary edema induced by xylazine administration in anesthetized sheep.Objective: To determine the ability and efficiency of each monitoring modality in detecting changes in lung function associated with onset of pulmonary edema.Methods: Twenty healthy ewes were anesthetized, positioned in sternal (prone) recumbency and instrumented. Synchronized recordings of EIT, spirometry and VCap were performed for 60 s prior to start of injection, during xylazine injection over 60 s (0–60 s) and continuously for 1 min (60–120 s) after the end of injection. After visual assessment of the recorded mean variables, statistical analysis was performed using a mixed effect model for repeated measures with Bonferroni’s correction for multiple comparisons, to determine at which breath after start of injection the variable was significantly different from baseline. A significant change over time was defined as an adjusted p < 0.05. All statistics were performed using GraphPad Prism 0.1.0.Results: Electrical impedance tomography showed significant changes from baseline in all but two variables. These changes were observed simultaneously during xylazine injection at 48 s and were consistent with development of edema in dependent lung (decreased end-expiratory lung impedance, ventilation in centro-ventral and ventral lung region) and shift of ventilation into non-dependent lung (decreased non-dependent silent spaces and increased center of ventilation ventral to dorsal and increased ventilation in centro-dorsal and dorsal lung region). All changes in lung mechanics also occurred during injection, including decreased dynamic respiratory system compliance and increased peak expiratory flow, peak inspiratory pressure and airway resistance at 48, 54 and 60 s, respectively. Changes in VCap variables were delayed with all occurring after completion of the injection.Conclusion: In this model of pulmonary edema, EIT detected significant and rapid change in all assessed variables of lung function with changes in regional ventilation indicative of pulmonary edema. Volumetric capnography complemented the EIT findings, while respiratory mechanics were not specific to lung edema. Thus, EIT offers the most comprehensive method for pulmonary edema evaluation, including the assessment of ventilation distribution, thereby enhancing diagnostic capabilities.

Electrical impedance tomography (EIT) is a non-invasive diagnostic tool for evaluating lung function. The objective of this study was to compare respiratory flow variables calculated from thoracic EIT measurements with corresponding spirometry variables. Ten healthy research horses were sedated and instrumented with spirometry via facemask and a single-plane EIT electrode belt around the thorax. Horses were exposed to sequentially increasing volumes of apparatus dead space between 1,000 and 8,500 mL, in 5–7 steps, to induce carbon dioxide rebreathing, until clinical hyperpnea or a tidal volume of 150% baseline was reached. A 2-min stabilization period followed by 2 minutes of data collection occurred at each timepoint. Peak inspiratory and expiratory flow, inspiratory and expiratory time, and expiratory nadir flow, defined as the lowest expiratory flow between the deceleration of flow of the first passive phase of expiration and the acceleration of flow of the second active phase of expiration were evaluated with EIT and spirometry. Breathing pattern was assessed based on the total impedance curve. Bland-Altman analysis was used to evaluate the agreement where perfect agreement was indicated by a ratio of EIT:spirometry of 1.0. The mean ratio (bias; expressed as a percentage difference from perfect agreement) and the 95% confidence interval of the bias are reported. There was good agreement between EIT-derived and spirometry-derived peak inspiratory [−15% (−46–32)] and expiratory [10% (−32–20)] flows and inspiratory [−6% (−25–18)] and expiratory [5% (−9–20)] times. Agreement for nadir flows was poor [−22% (−87–369)]. Sedated horses intermittently exhibited Cheyne-Stokes variant respiration, and a breath pattern with incomplete expiration in between breaths (crown-likebreaths). Electrical impedance tomography can quantify airflow changes over increasing tidal volumes and changing breathing pattern when compared with spirometry in standing sedated horses.

Neuromuscular blocking agents (NMBAs) are essential in intraocular surgeries to improve surgical conditions and ensure optimal ventilation. However, residual blockade can pose significant risks, particularly in pinnipeds due to their unique diving physiology. This case report describes the use of sugammadex for reversing rocuronium and AMG for monitoring neuromuscular block (NMB) in a California sea lion undergoing lensectomy. The objective is to evaluate the feasibility and safety of sugammadex for reversal of rocuronium-induced neuromuscular blockade and acceleromyography (AMG) for monitoring neuromuscular function in pinnipeds, with the goal of improving anesthetic management and recovery. Rocuronium (0.3 mg/kg IV) was used to achieve complete NMB, and an additional 0.1 mg/kg IV was administered to prolong the block. Sugammadex (1 mg/kg IV) reversed the NMB, with recovery within 90 s. Neuromuscular function was monitored using AMG, with the ulnar nerve of the foreflipper as the stimulation site. AMG allowed for an objective assessment of neuromuscular function, ensuring accurate titration of the NMBA and reversal agent. This is the first report documenting the use of sugammadex for the reversal of rocuronium and AMG for neuromuscular monitoring in a sea lion. This successful application highlights the potential of these techniques to improve anesthesia protocols, patient safety, and welfare in marine mammal medicine.

Neuromuscular blocking agents (NMBAs) are essential in intraocular surgeries to improve surgical conditions and ensure optimal ventilation. However, residual blockade can pose significant risks, particularly in pinnipeds due to their unique diving physiology. This case report examines the use of sugammadex for reversing the effect of rocuronium and the application of acceleromyography (AMG) for monitoring of neuromuscular block (NMB) in a California sea lion undergoing lensectomy. Rocuronium (0.3 mg/kg IV) was used to achieve complete NMB, and an additional 0.1 mg/kg to prolong the block. Sugammadex (1 mg/kg IV) effectively reversed the NMB within 90 seconds. Neuromuscular function was monitored using AMG, with the ulnar nerve in the front flipper serving as the stimulation site. The AMG allowed for objective monitoring of neuromuscular blockade, ensuring accurate titration of the NMBA and its reversal agent. This case represents the first report describing the use of sugammadex in a sea lion for reversing the effect of rocuronium and the use of AMG for monitoring of NMB, demonstrating its potential for improving anaesthesia protocols and patient safety in marine mammal anaesthesia.

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 ( p < 0.01), and unanticipated haemodynamic effects were observed, including a significant decrease in MAP ( p < 0.01) and increase in HR ( p < 0.01), with hypotension (MAP below 70 mmHg) occurring in 62% of post-injection measurements. TIV decreased significantly ( p = 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 p < 0.01), and FE of Na ⁺ and Cl ⁻ increased between T15 and T75 ( p = 0.01 and p = 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.