The role of the RVN in treating dystocia in mares

Uterine torsion

Torsion of the uterus constitutes 5–10% of all serious equine dystocias, with 50% of uterine torsions occurring during parturition in the first stage of labour (Vandeplassche et al, 1993). The pathophysiology of uterine torsion is connected to rolling or sudden movement where the weight of the gravid uterus can cause a torsion and colic has been suggested as a contributing factor in this process (LeBlanc, 1999).

Nursing care for uterine torsions

Frazer et al (2002) stated that to correct a uterine torsion, a well lubricated arm may be passed into the uterine body, where it may be possible to grasp the fetus ventrolaterally. The fetus and uterus can then be rocked back and forth until sufficient momentum is achieved to roll both fetus and uterus back into a normal position. Restraint of the patient would be an important part of the role of the RVN during this procedure. Frazer et al (2002) recommended using a twitch as a useful way to quickly restrain a mare for reproductive examination (Figure 2). Twitches cause the release of natural endorphins, which then have a narcotic effect on the horse. Linnenkohl and Knottenbelt (2012), however, stated that a twitch works partially by causing pain and distracting the attention of the horse and should therefore only be used when absolutely necessary. On occasion a horse may react unexpectedly when a twitch is used and this is where the equine handling skills of the RVN become exceptionally important. Accurate observation of behaviour and swift action to remove the twitch can prevent potential stress to the patient and injury to the examining veterinary surgeon (VS).

Frazer et al (2002) also advocated the use of standing flank laparotomy to correct uterine torsions. In the standing flank approach, a grid incision is made on the same side as the direction of the torsion. The torsion is corrected by placing the forearm under the uterus and gently rocking back and forth to gain momentum until the torsion is resolved (Frazer et al, 2002). The RVN plays a role in the preparation for this surgery. In the author's practice the surgery site would normally be clipped for this type of surgery despite a report from Geraghty et al (2009) who found that chlorhexidine was just as effective at disinfecting surgical sites in horses whether the hair was left long, clipped or shaved. Some evidence suggested that clipping dislodges bacteria from hair follicles, increasing the bacterial colony forming units (CFUs) at the surgery site and this increases the risk of infection (Zubrod et al, 2004). However Geraghty et al (2009) still advocate that catheter sites should be clipped as this reduces the chance of introducing foreign material at the surgical site. This is a significant consideration as equine patients live either in a field or in a stable, both of which are particularly contaminated environments (McHugh, 2012). Clipping therefore should be included in the preparation of the surgical site of a standing flank laparotomy where a surgical site infection could have devastating consequences.

The next consideration for the RVN is what type of skin disinfectant to use to prepare the surgery site with. The two most commonly used skin disinfectants in veterinary practice are chlorhexidine and povidone-iodine (Gibson et al, 1997). Povidone-iodine is inactivated by organic material (Gibson et al, 1997) and this could be considered undesirable in equine patients which live in heavily contaminated environments (McHugh, 2012). Chlorhexidine is believed to have a residual antiseptic effect lasting up to 6 hours (Desrochers et al, 1996). This would be particularly useful in the preparation of mares with uterine torsions as it is likely that the discomfort of the torsion will have caused them to roll contaminating the surgical site. Osuna et al (1990) also found a significantly increased rate of skin reactions in dogs with the use of povidone-iodine, which could lead to wound breakdown and reduced healing. Wilson et al (2011) recommended the use of chlorhexidine as a preoperative skin preparation for ponies after comparing it with povidone-iodine. This would support the use of a 4% chlorhexidine solution for the preparation of surgical sites in horses. After clipping and scrubbing the surgical site the RVN plays a role in restraining the mare or being involved as a surgical assistant until the surgery is completed.

The RVN would then care for the mare post surgery. Uterine torsions are often associated with colic (LeBlanc, 1999), therefore an RVN should monitor for signs of this disease in order to prevent associated complications; increases in heart rate and pulse rate can suggest pain and dehydration (Taylor, 2006) and readings should be taken regularly. Abdominal auscultation should be carried out frequently as this enables appreciation of gut activity and is invaluable in colic assessment (Taylor, 2006). A mare that develops colic is likely to roll which could cause disruption to the incision site in a mare that has undergone a laparotomy. Trauma to the incision line could cause delayed wound healing and lead to infection, which would compromise both mare and foal health. The mare may need intravenous fluids to correct dehydration or to assist in the treatment of an associated impaction colic. The RVN should monitor the catheter site for heat, pain, discharge or swelling, which can indicate thrombosis formation and can lead to thrombophlebitis (Copas and Boswell, 2012). Self-disinfecting catheter caps and chlorhexidine gluconate impregnated dressings can also be used to reduce the risk thrombophlebitis in these patients (Rippingale and Fisk, 2013).

Malpresentation of the fetus

Malpresentation is a term often used to describe abnormalities in presentation, position and posture of the fetus during parturition (Lu et al, 2006). Postural abnormalities are a major contributor to dystocia and are common in foals due to their long legs and neck (Blanchard et al, 2011) (Figure 4). In normal mares 98% of fetuses present in anterior dorsosacral presentation (Figure 5), 1.0% in posterior presentation (Figure 6) and 0.01% are in transverse presentation (Figure 7) at parturition (Vandeplassche, 1987). Although multifactorial causes have been identified, LeBlanc, (1999) stated that fetal factors account for the aetiology of most malpresentations in the mare.

Nursing care for malpresentations

There are four procedures used to resolve dystocia due to malpresentation in the mare: assisted vaginal delivery (AVD), where the mare is assisted in vaginal delivery of an intact foal by a VS; controlled vaginal delivery (CVD), where the mare is anaesthetised and the VS is in complete control of delivering an intact foal vaginally; fetotomy, where a dead fetus is cut into more than one piece for removal from the uterus per vagina; and caesarean section, where the fetus is removed through an incision in the uterus (Embertson, 2003). Some malpresentations are resolved on the yard by a VS, however if a dystocia is not resolved quickly the mare is often sent to a referral hospital (Embertson, 2003). On notification of a dystocia being admitted in to the hospital an RVN should set up equipment and organise personnel for:

Assistance during the CVD would include handling the mare during induction of anaesthesia and helping to attach the hobbles to the hind feet of the mare once she is recumbent. An RVN would assist the VS by providing lubricant and ropes during the CVD. If the CVD was successful the RVN would be involved in resuscitating the foal and this process will be explained in more detail later on in this article. During the CVD the RVN would clip and surgically prepare the abdomen of the mare for a caesarean section if necessary. If CVD proves unsuccessful after 15 minutes a caesarean section will be performed if the foal is alive. Positioning the mare properly for a caesarean section is very important. Traditionally, it is recommended that the mare be tilted off the midline while in dorsal recumbency (Johnston and Taylor, 2002). This minimises the risk of compression of the vena cava, which would result in low venous return, leading to hypotension (Johnston and Taylor, 2002). However Hendrickson (2007) and Munroe et al (2011) both advocated that the mare should be placed in dorsal recumbency without tilting. It is therefore important that the RVN establishes how the surgeon would like the mare to be positioned well in advance to avoid unnecessary delay of the surgery.

If a live foal is delivered the RVN is likely to be involved with resuscitation. A detailed explanation of cardiopulmonary resuscitation in the foal is beyond the scope of this article. However the main nursing considerations are summarised as follows:

Specific care for a mare recovering from dystocia caused by a malpresentation would include regular assessment of temperature, pulse and respiration (TPR) (LeBlanc, 2007). An increased temperature may indicate infection which may be caused by assisted vaginal delivery (AVD) of the fetus or a uterine laceration caused during the delivery (Frazer, 2007). Cardiac and abdominal auscultation should be assessed and recorded to check for signs of colic. RFM are a complication commonly associated with caesarean in the mare (Pycock, 2012). Vaginal discharge should be monitored to check for the symptoms of RFM. This condition will be discussed in more detail in the next part of this article.

RFM

RFM is a common complication in the postpartum mare, with an incidence of 2–10% of all deliveries (Lopate et al, 2003). The high incidence of this condition makes it an important consideration for RVNs, as there is a high likelihood it will be encountered in equine practice. The equine placenta is characterised by branching chorionic villi that interdigitate with the endometrial epithelium to form microcotyledons (Wilsner and Allen, 2003). The pathophysiology of RFM in the mare is yet to be determined; however it is likely that some dysfunction of the initial separation process at the microcotyledons occurs (Frazer, 2002).

Nursing care for RFM

If RFM are not passed within 3 hours post parturition the condition is considered an emergency as failure to treat the mare may result in metritis, laminitis, endotoxic shock and possible death (Macpherson, 2010). The RVN would assist with intrauterine lavage and oxytocin administration, both of which encourage removal of RFM (Frazer, 2002). Considerations here would be to keep the mare calm and restrained for the procedure to commence. Oxytocin promotes uterine contractions and facilitates the release of microvilli from endometrial crypts (Macpherson, 2010). The mare should also be monitored for signs of toxic metritis which would include an elevated heart rate and dark red mucus membranes (Blanchard et al, 1985; Frazer, 2002). If endotoxaemia develops, the RVN would be involved in further uterine lavage and intravenous fluid set up and monitoring. Close monitoring and strict care of the catheter site should be considered as discussed previously. Laminitis is an inflammation of the sensitive laminae in the hoof (Katz and Bailey, 2012) and is significantly associated with endotoxaemia (Parsons et al, 2007). Continuous cryotherapy has been suggested as a potential preventative strategy for equine laminitis (Van Eps et al, 2013). Continuous cryotherapy is difficult to achieve in practice without the use of a commercially produced ‘ice boot’, however the benefits may out weigh the cost of purchasing such equipment. The RVN is in a perfect position to apply cryotherapy at a critical time to endotoxic patients at the practice (Pollitt, 1999). Nursing implications for RFM may also include administration of medication in the form of anti-inflammatories and antibiotics. The medication would be prescribed by a VS but nursing implications would include monitoring for allergic reactions, monitoring injection sites for signs of inflammation and preventing the foal from directly ingesting any of the medication prescribed.

Key Points