Chapter 47 Kevin Walters Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Starkville, Mississippi, USA The provision of obstetric services continues to be an important aspect of the large animal practice. Previous chapters have covered prevention and described and defined dystocia. A subsequent chapter will cover the surgical management of dystocia (cesarean section). The purpose of this chapter is to describe the nonsurgical obstetric management of a dystocia as well as the decision parameters utilized to abandon one technique and proceed to another. This begins with a basic list of equipment, restraint options, and then progresses through the management of progressively more difficult obstetric cases. Terminology that describes both normal and abnormal dystocia as well as techniques employed is valuable for effective case management discussion among both veterinarians and veterinary students. The following are accepted definitions of presentation, position, and posture, which serve to describe fetal orientation with respect to the dam. Definitions for various obstetric techniques are as follow. This is an area in which the opinions of obstetricians might vary. There are instruments that one individual might consider unnecessary that another would not approach an obstetric case without. Therefore the approach taken will be to first list obstetric tools that most would deem absolutely necessary and then add others and their potential uses. Basic obstetric kit needs include at least two obstetric chains, two handles, a fetal extractor, a Krey hook, and basic surgery pack. Obstetric chains can be obtained in lengths of 53, 76, 114, and 152 cm. Chains are preferred over straps made for obstetrics for at least two reasons. The chains are more easily cleaned and despite the appearance are less likely to cause damage to the fetus or dam. With respect to handle selection, the old Muir obstetric handles are time tested but with the caveat that the heavier models are best. The type or model of fetal extractor is usually based on operator preference and its use is not controversial from my perspective. The Krey hook, which is routinely used in fetotomies, is listed among the basics as it is often useful in the vaginal delivery of a fetal abnormality or dead calf in which only a partial fetotomy is performed. A basic surgery pack is needed for such procedures as an episiotomy, a single appendage removal (partial fetotomy), or cesarean section (Figure 47.1). Additional obstetric tools that are useful include the calf-saver snare, which is easier to place around the head than using chains, a de-torsion bar, and a double blunt eye hook (Figure 47.2). Although limbs as well as the head and neck can be removed without a fetotome, to perform the classic fetotomy the following tools are necessary: a fetotome (model selected based on operator preference), saw wire, a wire guide, an “embryotomy” knife, and if not already in the obstetric kit a Krey hook (Figure 47.3). Figure 47.1 Basic obstetric equipment: (a) 152-cm obstetric chain; (b) 76-cm obstetric chain; (c) Krey hook with attached chain; (d) T-bar obstetric chain handle; (e) Moore’s obstetric handle; (f) components of disassembled fetal extractor. Figure 47.2 Additional obstetric equipment: (a) fetal head snare; (b) de-torsion bar or rod; (c) wooden dowel for applying torque to de-torsion bar; (d) double blunt eye hooks or Vienna scissor eye hooks. Figure 47.3 Fetotomy equipment: (a) Utrecht fetotome; (b) threader or insertion coil and wire brush; (c) Lyss wire saw handles; (d) wire saw handles; (e) Shriever wire saw introducer or passer; (f) Hauptner wire saw introducer or passer; (g) Linde’s fetotomy palm knife; (h) Geunther’s fetotomy finger knife; (i) side cutters to sever wire saw; (j) T-bar obstetric handle; (k) Krey hook with obstetric chain attached; (l) wire saw; (m) Moore’s obstetric handle. The restraint approach utilized must be safe for obstetrician and patient. Both facilities available and patient temperament dictate the approach taken. Haul-in facilities are almost always superior to those found on farms and indeed if a significant percentage of a practice is devoted to bovine obstetric work, suitable facilities are a good investment. Although on-farm dystocia cases are often recumbent, most obstetric procedures and specifically mutation are easier on the well-restrained standing cow. Often a cow that has previously refused to stand will do so after the administration of an epidural, presumably due to the abatement from the pain associated with labor.1 A cattle chute is adequate for examination, preparation, and the administration of an epidural, but you must have the ability to open a side or otherwise get the cow out in case she goes down during the obstetric procedure. In virtually all cases, with the exception of a purpose-designed dystocia chute or stanchion, you will be better off with the cow haltered and tied in the corner of a stall/pen/lot. As the large animal practitioner must often utilize to some extent a form of triage in determining which client’s request or patient must be attended to first, the obstetric case begins with the perfunctory question of duration of labor. This may be of marginal value without an understanding on the part of the client of the stages of labor. For example, the time period that an owner relates is almost always from the time they first noticed the cow, without any respect to the stage of parturition. The stages of labor are as follows. Thus the appropriate question to ask the owner/attendant is whether or not fetal membranes or an extremity is visible, followed by queries to ascertain whether allantoic rupture has occurred (“Have the waters broke?”). Simply determining this provides the answer with respect to continued observation or immediate attention. Additionally, the knowledgeable stockman might be able to describe the presentation based on observation or their preliminary examination. Just as the knowledge that labor has progressed to stage 2 dictates prompt attention, so does a posterior presentation. Other questions relate to parity, past calving history, and sire. The young veterinarian must realize that extensive questioning is often off-putting to the cattleman and one may be wise to simply expedite matters and obtain necessary information during the course of the management. The relative value of the cow versus the calf may also be important and will often be a factor in the management approach. The examination begins as the cow is approached and as the animal is restrained. The temperament and physical condition are assessed. Prior to the obstetric examination the tail should be tied to her neck (or held by an assistant) and the perineum cleaned with soap and water. The obstetric examination can be performed before or after the administration of an epidural, but at any rate should be done quickly and with the purpose of guiding the direction of obstetric management. Thus fetal viability, the presentation, position, posture, and degree of fetus–dam disproportion are evaluated. Fetal viability and even how long a calf may have been dead are important determinants with respect to management. If the presentation and position are normal, but an extremity is malpostured, the fetus can be repulsed and the posture corrected, followed by traction for example. A very large and viable calf in a heifer or relatively small cow directs one to cesarean section, as in turn a large dead fetus may dictate a fetotomy. The presentation is easily assessed if the obstetrician can identify the head or conversely the tail/tailhead. When a determination must be made based on palpation of a limb, one should simply remember that the first two joints of the forelimb, the metacarpal joint (fetlock) and the carpus (knee) will both flex in the same direction, while the fetlock and hock flex in opposite directions. The examination must therefore be performed in an efficient thoughtful manner with the goal of directing the first or next obstetric procedure and avoidance of the creation of a potential complication. It is intertwined with management, and reassessment of the case may result following an unexpected finding or the inability to complete a prescribed plan of action. As the reader would hopefully surmise from the section on examination, obstetric management is fluid, but should follow a reasonable course that results in a successful outcome, which in turn is dependent on the initial findings. A common dystocia presentation is a fetus in anterior presentation with normal posture (for this and other dystocia images, see Chapter 46). If traction results in a severe and immediate crossing of the forelimbs as the shoulders engage the maternal pelvis, the calf is likely too large to be delivered vaginally. Thus the next step would be to move to a cesarean section or fetotomy. In the case that the fetus is of a size in relation to the dam that vaginal delivery should be possible, examination to determine the cause of dystocia should follow. Was there adequate cervical dilation? Is the heifer or cow exhausted or suffering uterine atony? Are there concurrent issues such as hypocalcemia? Is there inadequate dilation of the vulva? Depending on the answer, your next step could be to simply apply traction, but these issues should all be considered. An anterior presentation in which the fetus is rotated in position based on head or limb orientation, findings from your vaginal examination, or findings of a rectal examination should lead to a diagnosis or suspicion of torsion. Diagnosis and obstetric management of uterine torsion is discussed in Chapter 46 and surgical management is discussed in Chapter 48.
Obstetrics: Mutation, Forced Extraction, Fetotomy
Introduction
Obstetric terminology
Basic equipment
Case management
Restraint
History
Examination
Obstetric procedures and decision-making
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