Hypoxemia in horses refers to a condition characterized by low levels of oxygen in the blood. It can occur due to various respiratory or circulatory issues, impacting the horse's overall health and performance. Causes of hypoxemia in horses may include pulmonary diseases, airway obstructions, or cardiovascular problems. The condition is identified through clinical signs and diagnostic tests, such as arterial blood gas analysis. Monitoring and managing hypoxemia are essential for maintaining equine health, particularly in athletic horses or those undergoing anesthesia. This page compiles peer-reviewed research studies and scholarly articles that explore the causes, diagnosis, and management of hypoxemia in horses.
Abrahamsen E, Hellyer PW, Bednarski RM, Hubbell JA, Muir WW.Arterial hypertension developed in a horse anesthetized for arthroscopy and lavage of an inflamed right carpal joint. Anesthesia was induced with xylazine HCl, butorphanol, guaifenesin, and thiamylal Na and was maintained with halothane in oxygen. Arterial hypertension and tachycardia developed within 15 minutes after a pneumatic tourniquet was placed 8 to 10 cm proximal to the right carpus and inflated to 800 mm of Hg. The surgical procedure was expedited, halothane was discontinued and anesthesia was maintained with guaifenesin to facilitate bandaging. Heart rate decreased from 72 to 42 beat...
McMurphy RM, Cribb PH.This study was designed to investigate the effect of the nasotracheal insufflation of oxygen at a flow rate of 15 L/min on the arterial partial pressure of oxygen during the recovery period following inhalation anesthesia in the horse. It has been stated that this is a suitable flow rate to prevent postoperative hypoxemia but without any experimental evidence to support those statements. Horses being used for the study of healing of cartilage were anesthetized on two separate occasions. Following one period of anesthesia they were allowed to recover breathing room air, and following the other ...
Forster HV, Pan LG.In humans alveolar ventilation (VA) is adjusted almost perfectly to the metabolic demands of mild and moderate exercise. For example, in exercise transitions and in the steady state, PaCO2 rarely deviates by more than 1 to 3 mmHg from the value at rest. This near-homeostasis contrasts to most other mammalian species; equines for example, demonstrate a progressive hypocapnia and alkalosis as exercise intensity is increased to moderate levels. In equines, the control systems seem programmed for a specific hyperventilation that contributes to maintenance of PaO2 homeostasis. Generally, during hea...
Bayly WM, Schultz DA, Hodgson DR, Gollnick PD.Experiments were undertaken to determine whether respiratory masks worn by horses exercising strenuously on a treadmill may interfere with normal gas exchange. Four collection systems, two flow-through systems and two incorporating one-way valve systems with subject-generated airflow were studied. Six horses performed standard treadmill exercise tests consisting of a 2-min warm up followed by galloping 1 min each at 8,9, and 10 m/s. Each horse exercised six times while wearing each of the four respiratory masks. Each flow-through system was used twice with flow rates of 2,360 and 3,840 l/min f...
Mason DE, Muir WW, Wade A.The effects of body position and postoperative oxygen supplementation on arterial blood gas tensions (PaO2 and PaCO2) and pH were examined in clinically normal adult horses during recovery from halothane anesthesia. Hypoxemia developed during recovery from anesthesia in spite of adequate alveolar ventilation in horses without postanesthetic oxygen supplementation. Hypoxemia developed in horses positioned in left lateral or right lateral recumbency, and in horses that were rolled to the opposite side during the recovery period. Arterial blood gas tensions were not significantly (P greater than ...
Moore JN, Garner HE, Shapland JE, Hatfield DG.Bacterial endotoxin injected intravenously into conscious ponies produced alterations in cardiopulmonary and gastrointestinal function. Specifically, tachypnoea, dyspnoea, hypoxaemia, colic, lactic acidosis and diarrhoea resulted from administration of 10 micrograms/kg Escherichia coli endotoxin. Pretreatment of the ponies with a potent prostaglandin synthetase inhibitor, flunixin meglumine, prevented these ill effects of endotoxin.
Moore JN, Garner HE, Shapland JE, Hatfield DG.Effects of a sublethal IV dose (10 micrograms/kg of body weight) of Escherichia coli endotoxin were studied in 7 conscious ponies. Arterial blood gases and plasma lactic acid were determined periodically throughout the 180 minutes of the study. Arterial hypoxemia occurred within 5 minutes despite intense hyperventilation. Colic and diarrhea occurred in all ponies within 30 minutes after endotoxin administration. Metabolic acidosis developed within 30 minutes and persisted throughout the study, indicating widespread reduced tissue perfusion.
Steffey EP, Wheat JD, Meagher DM, Norrie RD, McKee J, Brown M, Arnold J.Effects of body position and type of ventilation were determined on arterial blood gases (PaO2, PaCO2) and pH during and immediately following clinical halothane anesthesia in 36 young, physically conditioned horses. Horses in dorsal recumbency had a lower PaO2 than did similarly breathing horses in a lateral position. Predictably controlled positive-pressure ventilation inproved arterial oxygenation and permitted maintenance of a normal PaCO2. Most horses, regardless of type of ventilation and operative body positioning, were hypoxemic in the immediate postanesthetic period.
Forster HV, Bisgard GE, Rasmussen B, Orr JA, Buss DD, Manohar M.The present study was designed to provide further insight into the role of the carotid and aortic chemoreceptors in ventilatory (VE) acclimatization during sojourn at altitude. Measurements were made: 1) on 10 ponies near sea level (SL, 740 Torr) under normal conditions, 2) on 6 of these at SL following chemoreceptor denervation (CD), and 3) subsequently on all 10 during 4 days of hypobaric hypoxia (PaO2 = 40-47 Torr). CD resulteo in hypoventilation at SL (deltaPaCO2 = d8 Torr, P less than 0.05), and it prevented hyperventilation normally observed with injection of NaCN and acute exposure to h...
Hummer EV, Soares JHN, Crockett DC, Aguiar AJA, Tran MC, Cronin JN, Brosnan RJ, Braun C, Formenti F.The possibility of accurately and continuously measuring arterial oxygen partial pressure (PaO2 ) in horses may facilitate the management of hypoxaemia during general anaesthesia. Objective: The aim of this study was to evaluate the ability of a novel fibreoptic sensor to measure PaO2 (PaO2Sensor ) continuously and in real time in horses undergoing ventilatory manoeuvres during general anaesthesia. Methods: In vivo experimental study. Methods: Six adult healthy horses were anaesthetised and mechanically ventilated in dorsal recumbency. A fibreoptic sensor was placed in one of the facial arteri...
Milnes EL, Skelding AM, Larouche CB, Ferro A, Delnatte P, Dutton C, Anderson NE.To compare ketamine-butorphanol-azaperone-medetomidine (KBAM) to detomidine-etorphine-acepromazine (DEA) for field anesthesia in captive Przewalski horses (Equus przewalskii). Methods: 10 adult Przewalski horses. Methods: A prospective randomized crossover trial was conducted. Each horse was immobilized once with KBAM (200 mg ketamine, 109.2 mg butorphanol, 36.4 mg azaperone, and 43.6 mg medetomidine) and once with DEA (40 mg detomidine premedication, followed 20 minutes later by 3.9 to 4.4 mg etorphine and 16 to 18 mg acepromazine). Both protocols were administered by IM remote dart injection...
Drummond WH, Sanchez IR, Kosch PC, Webb AI.Adult ponies develop pulmonary hypertension at altitude (Bisgard, Orr and Will 1975), but the neonatal response to acute hypoxaemia is unknown. Seven foals aged five days were instrumented with a systemic and a Swan-Ganz pulmonary artery catheter while anesthetised and intubated. Cardiac index, pulmonary (PAP) and systemic (SAP) vascular pressures were measured as the foals breathed gas mixtures with FI02 of 8 to 94 per cent. Because foramen ovale or ductus arteriosus shunts might have altered thermodilution cardiac index measurements in the stressed foals, the ratio, PAP/SAP was calculated to...
Marchese GA, Crystal J, Louro LF.Prevalence and risk factors of severe hypoxemia in anesthetized horses undergoing emergency exploratory laparotomy are sparsely documented. The aim of this study was to report incidence of severe hypoxemia ( PaO2 < 60 mmHg) in horses undergoing emergency exploratory laparotomy and identify potential risk factors for this complication. A single center retrospective cross sectional designed was used. Clinical data of 714 horses undergoing general anesthesia for emergency explorative laparotomy were reviewed. A backward stepwise elimination procedure was used to determine the final multivariable ...
Aoki M, Wakuno A, Kushiro A, Mae N, Kakizaki M, Nagata SI, Ohta M.Anesthetic and cardiorespiratory effects of total intravenous anesthesia (TIVA) technique using propofol-guaifenesin-medetomidine (PGM) and alfaxalone-guaifenesin-medetomidine (AGM) were preliminarily evaluated in Thoroughbred horses undergoing castration. Twelve male Thoroughbred horses were assigned randomly into two groups. After premedication with intravenous (IV) administrations of medetomidine (5.0 µg/kg) and butorphanol (0.02 mg/kg), anesthesia was induced with guaifenesin (10 mg/kg IV), followed by either propofol (2.0 mg/kg IV) (group PGM: n=6) or alfaxalone (1.0 mg/kg IV) (group AGM...
Oku K, Yamanaka T, Ashihara N, Kawasaki K, Mizuno Y, Fujinaga T.To evaluate clinical usefulness of xylazine (1.0 mg/kg)-midazolam (20 microg/kg)-propofol (3.0 mg/kg) anesthesia in horses, 6 adult Thoroughbred horses were examined. The quality of induction varied from poor to excellent and 5 out of 6 horses presented myotonus in the front half of the body. However, paddling immediately after induction observed in other reports of equine propofol anesthesia was not observed. Recovery time was 35.3 +/- 9.3 min and the quality of recovery was calm and smooth in all horses. Respiration rate decreased after induction and hypoxemia was observed during lateral rec...
Guedes A, Aleman M, Davis E, Tearney C.To determine physiologic responses to apnea-induced severe hypoxemia in anesthetized horses. Methods: Prospective experimental study. Methods: Six university-owned horses with a median (range) body weight of 500 (220-510) kg and aged 13.5 (0.8-24.0) years scheduled for euthanasia. Methods: Xylazine-midazolam-ketamine-anesthetized horses breathing room air spontaneously were instrumented with a facial artery catheter for pressure measurement and blood sampling, and were made apneic with atlanto-occipital intrathecal lidocaine (4 mg kg ). Cardiopulmonary, biochemical and hematologic variable...
Clark-Price SC, Lascola KM, Auckburally A, Boone LH, Caldwell FJ, Weatherall KM, Hanson RR.Impairment of oxygen uptake can occur during general anesthesia in horses resulting in hypoxemia. Multiple treatments have been investigated for correction of hypoxemia with varying levels of success. In clinical trials, albuterol, a short-acting β2 adrenergic agonist, improved arterial oxygen partial pressure (PaO2) in anesthetized horses unresponsive to adjustments in mechanical ventilation and administration of positive inotropic drugs. However, controlled studies comparing the magnitude of change and duration of effect of albuterol on PaO2 in healthy, nonhypoxemic anesthetized horses are ...
Kaartinen MJ, Pang DS, Cuvelliez SG.CASE 1: A two-year old, 462 kg Standard bred horse was anesthetized for arthroscopy and castration. During anesthesia, hyperemia of the mucosal membranes and urticaria were noticed. During 5 hours of anesthesia subcutaneous edema of the eyelids and neck region developed. In the recovery box, the orotracheal (OT) tube was left in situ and secured in place with tape. Following initial attempts to stand, the horse became highly agitated and signs consistent with pulmonary edema developed subsequently. Arterial hypoxemia (PaO(2): 3.7 kPa [28 mmHg]) and hypocapnia (PaCO(2): 3.1 kPa [23 mmHg]) were ...
