Caesarean section is usually performed as an emergency procedure, so getting to grips with both the anaesthesia and analgesia for this event is essential to ensure the best possible outcome for both mother and her offspring. Sheilah Robertson led last week’s webinar discussing this particular topic and talked us through how to devise an anaesthetic management plan so the whole veterinary team know exactly what to do as quickly and as effectively as possible when presented with a patient requiring a C-section.

The majority of the advice delivered by Sheilah was based on the changes in physiology of the dam during pregnancy. For example, when a patient is placed in dorsal recumbency, the weight of the uterus can push down on the diaphragm and significantly reduce the lung’s functional reserve capacity. Under these circumstances, it is possible for patients to desaturate very quickly under anaesthesia. For this reason Sheilah strongly recommends pre-oxygenating patients for at least three minutes and also raising their head and chest so they are higher than their hind limbs when placed in dorsal recumbency.

Humans also suffer from aortocaval compression when placed on their back which can cause a significant drop in blood pressure and, although this has been shown not to happen in the average sized dog, it is something we should be aware of in large breeds or in those patients with a large number of foetuses present within their uterus. For this reason Sheilah advises preparing a patient for surgery in lateral recumbency and only placing them in dorsal recumbency when absolutely necessary.

Monitoring of carbon dioxide levels using a capnograph can also be useful during surgery as over-zealous ventilation could lead to a drop in CO2 levels which has the potential to be detrimental. A reduction in CO2 levels below 22 mmHg can cause a decrease in uterine blood flow and oxygen delivery so care should always be exercised when ventilating these patients and as stated previously, these patients should ideally be monitored using a capnograph.

Sheilah discussed the requirement for premedication for patients undergoing a C-section which she believes can be useful in fractious animals or for fit and healthy patients which are undergoing an elective procedure. Sheilah, however, strongly advises against the use of alpha-2 agonists as they cause vasoconstriction and a drop in CO2 which can decrease the uterine blood volume by up to 50%. ACP should also be avoided in dehydrated and / or hypovolaemic patients. The use of opioids can cause respiratory depression in the offspring and potentially bradycardia in the dam, however there will also be a reduced requirement for the amount of inhalational anaesthetic. Sheilah advised a compromise could be met by administering opioids after the puppies or kittens have been removed during a C-section so the dam will at least benefit from their analgesic effects and offer a smoother recovery.

The induction of anaesthesia is a crucial stage in ensuring the safety of the dam as it is imperative that her airway is controlled as quickly as possible. During pregnancy, the dam’s oesophageal sphincter tone is lower, there is gastric compression of the uterus and prolonged gastric emptying which combined all lead to a greater risk of aspiration pneumonia and make early airway control during induction essential. The importance of this is emphasised by studies demonstrating that 50% of patients which died as a result of their C-section was secondary to aspiration pneumonia.  For this reason, Sheilah advises against mask induction using inhalational anaesthesia as there has been shown to be a greater mortality compared to other forms of induction probably as a result of the airway not being controlled as quickly. The intravenous administration of either propofol or alfaxalone is the induction method of choice and studies have shown there were no maternal deaths using either drug with no differences in puppy survival rates between either propofol or alfaxalone. However, one study did show that the puppy Apgar scores (a measure of puppy vigour) were higher and therefore the pups were more active in dams induced with alfaxalone compared to those induced with propofol. Sheilah also advised whether using propofol or alfaxalone as an induction agent, the patient should always then be switched over to an inhalational agent in order to maintain anaesthesia.

This webinar delivered an intelligent and evidence based approach to performing anaesthesia and analgesia in patients undergoing a C-section. All the information delivered by Sheilah was combined at the end of the webinar to demonstrate how the whole team can work together to effectively manage these cases from the moment they walk in right through to their recovery hopefully alongside a lively and healthy set of puppies or kittens. This is a webinar which would benefit the whole veterinary team and could prove invaluable the next time a whelping bitch or queen walk through the practice door.