How to Assess and Stabilize a Mare Suspected of Periparturient Hemorrhage in the Field

REPRODUCTION—PERINATOLOGY How to Assess and Stabilize a Mare Suspected of Periparturient Hemorrhage in the Field Charles F. Scoggin, DVM, MS; and Patrick M. McCue, DVM, PhD, Diplomate ACT Authors’ addresses: Pioneer Equine Hospital, Inc., 11501 Pioneer Avenue, Oakdale, CA 95361 (Scoggin); and the Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, B.W. Pickett Equine Center, Colorado State University, Fort Collins, CO 80523 (McCue); e-mail: [email protected]. © 2007 AAEP. 1. Introduction and subsequently died, rupture of a uterine artery The peripartum period is defined as the time period was determined to be the cause of death in 40 of just before, during, or immediately after parturition. these mares. A more recent report provided con- Although the vast majority of foalings proceed with- current evidence regarding uterine artery hemorrhage being the most common post-partum out complications, there are certain disease pro- 2 cesses that are more common and unique to the complication in mares. Rupture of the external iliac artery, utero-ovarian artery, and uterine artery peripartum period. One such concern is peripartu- 3 rient hemorrhage (PPH). Important causes of have all been attributed to the onset of PPH. Both hemorrhage in peripartum mares include arterial the external iliac artery and utero-ovarian artery rupture, uterine rupture, vaginal varicose veins, cer- branch directly off of the aorta and the uterine ar- vical lacerations, and other forms of perineal tery branches off of the external iliac artery. Re- trauma. PPH is a fairly broad term, but for the gardless of the site of rupture, PPH can lead to rapid purpose of this paper, it will be selectively used to and profound blood loss, which can result in hypo- refer to the process whereby rupture occurs to one or volemic shock and death. Consequently, suspected more of the arterial vessels supplying blood to the cases of PPH should be considered as true emergencies uterus and related structures. that require a timely evaluation and case assessment. A serious and often life-threatening condition, The objective of this report is to provide practitioners PPH is thought to be one of the most common causes with a brief overview of PPH and offer recommenda- of deaths in peripartum mares. A review of 98 tions regarding the diagnosis, stabilization, and management of mares with PPH in the field. records from central Kentucky during the 1992 and 1993 foaling seasons revealed that reproductive complications accounted for the majority (57 of 98 2. Pathogenesis cases) of deaths in peripartum mares.1 Of the 57 The exact mechanism by which PPH occurs is cur- mares that experienced reproductive complications rently unknown. Rooney3 has hypothesized that NOTES 342 2007 ր Vol. 53 ր AAEP PROCEEDINGS REPRODUCTION—PERINATOLOGY the onset of PPH is a result of certain physiologic the average age of mares whose cause of death was changes and increased mechanical forces that occur attributed to PPH was Ͼ18 yr (range ϭ 12–21 yr).3 during late gestation. Briefly, age-related degener- In a separate study, the average age of mares that ation of one of the aforementioned arterial vessels died because of PPH was 18.5 yr (range ϭ 15–22 yr), because of increased strain from the gravid uterus whereas the average age of mares experiencing PPH can form an aneurismal dilatation. Added stress but surviving the hemorrhagic event was 11.5 yr by a late-term fetus or uterine contractions further (range ϭ 9–15 yr).4 This latter report suggests compromises the endothelial lining of the vessel, that younger mares may have an increased chance which results in blood dissection and eventual rup- of survival after PPH compared with older mares, or ture. Profound hypovolemia usually ensues, which alternatively, mares over the age of 15 yr were more can lead to severe hypoxemia, multi-organ dysfunc- likely to die after PPH than younger mares Ͻ15 yr tion syndrome, and death. The right uterine artery old. has the highest frequency of rupture relative to the Another identified predisposing factor is copper other vessels.1,3 The predisposition of this vessel to deficiency. In 1968, Stowe6 reported that mares rupture could potentially be caused by displacement experiencing a fatal uterine-artery rupture had sig- of the uterus to the left abdominal wall by the ce- nificantly lower serum copper concentrations com- cum, which results in increased tension in the right pared with mares of similar age that were not broad ligament.4 Unfortunately, both the mecha- experiencing hemorrhage during the periparturient nism of PPH and the propensity to affect the right period. Copper is thought to aid in maintaining uterine artery is still a subject of conjecture, because elasticity and promoting integrity of vascular walls. there are no scientific reports that evaluate the Serum-copper concentrations have been shown to pathophysiology of PPH. increase in normal mares during late gestation.6,7 In the authors’ experiences, there are at least These observations are suggestive of the inherent three clinical scenarios that can cause PPH. The importance of adequate serum concentrations of this first scenario is that of direct hemorrhage into the trace mineral during the peripartum period. Con- peritoneal cavity. This particular form of PPH can sequently, pregnant mares with low serum-copper lead to peracute and extreme hypovolemia, and concentrations may be considered at risk for PPH. thus, carries a guarded to grave prognosis for sur- A previous episode of PPH could possibly be con- vival. The second scenario is that of hemorrhage sidered a predisposing factor. Unfortunately, there confined to the broad ligament or serosal layer of the is very little published literature evaluating the re- uterus, which often leads to the development of a currence of PPH in mares. Pascoe4 did report on hematoma. In general, hemorrhage confined to the one mare that had experienced a ruptured uterine broad ligament or serosal layer of the uterus carries artery but had survived the hemorrhagic event. a more favorable prognosis than direct hemorrhage The mare was bred again, and she conceived. The in the peritoneal cavity. Hematomas in these re- mare carried that foal to term, but she subsequently gions are occasionally incidental findings during re- died because of another episode of PPH. This reproductive evaluations early in the post-partum port suggests that a previous episode of PPH may period. Nevertheless, they can rupture days to predispose mares to a hemorrhagic event during weeks after the initial hemorrhagic event and future parturitions. However, anecdotal evidence thereby, result in death.5 The third scenario is that from large breeding farms in central Kentucky pro- of hemorrhage confined within the uterine lumen. vides a conflicting viewpoint in that many practitio- In all likelihood, this type of PPH does not affect one ners from these farms have not observed recurrent of the larger arterial vessels previously mentioned; episodes of PPH in individual mares. rather, it is thought to occur after rupture or lacer- Although not clearly delineated in studies evaluation of one of the smaller mural vessels. In gen- ating PPH, the parity of a mare could potentially eral, the prognosis for survival is fair to good; these serve as a risk factor for two reasons. First, the mares do not seem to experience profound hypovo- parity of a mare, in general, often increases with lemia like those with the other types of PPH. It increasing age, which is a known risk factor for PPH should be noted that mares can concurrently expe- (i.e., multiparous mares are often of a more ad- rience more than one clinical form of PPH. For vanced age than nulliparous or primaparous mares). example, a mare may experience direct hemorrhage Second, vascular degeneration or angiosis in uter- into the peritoneal cavity and direct hemorrhage in ine-biopsy specimens was shown to increase in se- the uterus at the same time. Therefore, careful verity as the number of foalings increased in mares.8 evaluation and timely treatment, as will be dis- This finding could be extrapolated to pathologic cussed below, is essential in the management of any changes that may occur in the greater arterial ves- mare experiencing any signs of PPH. sels supplying blood to the uterus. Therefore, this could possibly implicate increased parity as a pre- 3. Risk Factors disposing factor in the onset of PPH. Certain predisposing factors have been identified Last, dystocia, breed, body condition, and environ- that could cause mares to have PPH. Probably the ment could perhaps serve as additional risk factors most recognized factor is that of age. In one study, leading to PPH. Further studies would be neces- AAEP PROCEEDINGS ր Vol. 53 ր 2007 343 REPRODUCTION—PERINATOLOGY sary to determine the association between these risk confined area just outside the stall where the mare factors and PPH. can still see the foal. The authors have created such an area by using bales of straw or hay. It is 4. Diagnosis important to realize that some mares may become The severity and peracute onset of PPH constitutes, even more distressed or anxious if the foal is re- with very few exceptions, a true emergency situa- moved, thereby leading to unwanted and untoward tion. Consequently, a mare suspected of PPH ne- effects on the mare. Consequently, the disposition cessitates a rapid response, an accurate yet efficient and mentation of the mare should be carefully evalu- assessment, and proper therapy. The ability to re- ated before, during, and after removal of the foal. spond rapidly to a suspected case of PPH is depen- Last, the clinician may consider having the attendant dant on the clinician’s practice range and geography.

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