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Perinatology: time-lines and teamwork

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01 December 2010, at 12:00am

MARION McCULLAGH concludes her reports on papers presented at this year’s BEVA congress

DYSTOCIA in the mare is one of the true emergencies that occurs in equine practice.

Madeline Campbell, president of the BEVA, who practises in Sussex, outlined “Dealing with dystocia in the field” in a paper presented during the BEVA congress in September.

In thoroughbreds, about 4 % of parturitions give rise to dystocia with a higher incidence, around 10%, in draught mares. Normal birth in the mare happens rapidly and foal survival is inversely proportional to the length of second stage labour.

It is essential for the owner to recognise when the mare is in trouble so the practice needs to have done good work on client education well in advance of the expected date of foaling.

There are basic time-lines: the mare should foal within 24 hours of waxing up and second stage labour should take no more than 20 minutes. The owner needs to know that any dripping milk is abnormal, colostrum that is produced before foaling must be saved and given to the foal, which is at risk of insufficient intake of antibodies and energy.

Avoid suffocation

In normal circumstances the allanto- chorionic membrane ruptures at the beginning of second-stage labour. If the foal is born without rupture of the amnion, a human needs to break the membrane or the foal will suffocate.

The umbilical cord should not be broken as the foal needs all of the blood that drains from the placenta. If the cord is broken and bleeding it needs to be clamped.

In the condition known as “Red bag” there is premature placental separation and a red velvety membrane marked with the white cervical star appears at the vulva. The foal can be felt inside it and the membrane needs to be ruptured and the foal extracted quickly.

Advice covering this sort of situation needs to be given by the veterinary surgeon, perhaps while driving to the foaling, as rapid action is essential to save the foal. The mare’s future reproductive career is the other consideration: any intervention needs to treat the reproductive tract as gently and carefully as possible. The veterinary surgeon needs to have a full dystocia kit ready in the car. This should include foaling ropes and handles, a generous supply of obstetrical lubricant (complete with a stirrup pump and a sterile stomach tube to get it into the uterus), drugs for sedation and anaesthesia of the mare and revival of the foal, an “Ambibag” foal resuscitator, and a foal oro-tracheal cuffed tube. A fetotomy kit completes the picture.

There are four stages of intervention in dystocia. The first is assisted vaginal delivery (AVD). The mare is standing and may be sedated. Be aware of human safety when treating the mare: she can be distressed and may behave unpredictably.

Action plan

There needs to be an action plan agreed with the owner before the foaling. Is the priority to save the mare or the foal? What are the financial constraints? Will the owner want the mare referred for hospital treatment if the situation cannot be resolved by AVD?

Plans as to where the mare can be referred and how she is to be transported need to be made in advance. The referral hospital needs to be able to assemble a team for a caesarean at short notice. Delay and indecision can mean death to mare or foal or both.

The next stage is controlled vaginal delivery (CVD). The mare is anaesthetised, her hind legs are elevated and the delivery is totally under the control of the clinician. CVD is best done in the anaesthetic induction area of the hospital while the mare’s abdomen is being clipped and prepared for surgery.

If the foal can be delivered, all is well, otherwise no time is lost in going for the next stage which is caesarean section. If the foal is dead, the fourth stage, fetotomy, can be carried out in the standing, sedated mare.

Survival

Having delivered the foal, the next thing is to make sure that it survives. Peter Morresey of Rood and Riddle Equine Hospital in Kentucky gave us his views on “Identification and management of the high-risk foal in practice”.

It is important to establish the value of the foal before starting on intensive treatment as this is likely to be expensive and prolonged and the outcome is uncertain. The condition of the mare, her uterus and the environment in which the foaling took place all need to be considered.

It is useful to know the history of previous foalings and also to know whether the mare had suffered any illnesses during the pregnancy. Any deviations from normal in the foal need to be recognised and acted on quickly.

The normal foal should achieve sternal recumbency within 30 minutes of birth. It should stand and feed within two hours and it should have urinated and defaecated within six to 10 hours.

If the foal is seen to be straining with its back arched, it has problems with defaecation; if its back is dipped, the problems are with urination.

A weak foal that takes too long to get up is more exposed to pathogens from the ground, potentially leading to sepsis and is more likely to suffer hypothermia or trauma from getting trodden on.

Is the foal a potential athlete? Radiographs taken early on can determine whether the animal is structurally sound and worth working with. A foal with fractured ribs is in severe pain and will breathe shallowly.

Ultrasonographic examination should be used to monitor for haemorrhage. Ultrasound is also useful in evaluating the bladder. Healthy bladders do not rupture so if there is any leaking sepsis of the bladder wall should be suspected.

Don’t overfeed

In general, foals do not show pain as an adult would. If the foal appears to be depressed, look for sepsis, starvation, hypoxic ischaemic encephalopathy, neonatal isoerythrolysis, as well as surgical lesions.

Always look at the mare’s udder to establish whether the foal has sucked. A sick foal should not be overfed: it can only take 10% of its bodyweight daily as milk.

The sick foal demands close inspection: for example, it is necessary to examine its eyes and inside its mouth and ears. A septic foal may show haemorrhage in the sclera which may indicate thrombocytopaenia. Haemorrhage inside the mouth may be due to trauma. 

Any foal that shows lack of interest in its mother is a cause for concern. It may take eight days from being born for any evidence of the neurological dysfunction caused by hypoxia to become apparent, though this usually shows at around 24 to 48 hours.

Huge risk

The dummy foal that wanders off and hides its head in a corner and is not sucking is at huge risk, and this can be underestimated by the owner. Seizuring is obvious and, again, a major problem.

Several parameters that are reliable in the adult are not in the foal. The heart rate and respiratory rate, PCV and CBC are all untrustworthy though the blood lactate level is useful.

The foal must be kept warm, using blankets, insulated covers or bags of warmed fluid. It must not be overheated and if it is hypovolaemic this must be corrected with appropriate fluid therapy or the warming will increase the peripheral circulation at the expense of the blood pressure and so cause harm. Restoring the fluid volume also helps the brain.

Feeding needs to be parenteral if the foal is cold as the perfusion of the gut will be inadequate for proper absorption of the nutrients.

So, overall, care of the mare and new foal needs good strategy, a practical plan that can be put into action at speed and followed by dedication and co-operation from everyone concerned.