Analgesia for the caesarean section is a hot topic which generates many questions. There are two recent references on this topic which I digest here. In 2016 Dr Sheilah Robertson authored an article for In Practice which comprehensively reviewed the topic. In 2019 Dr Ian Self wrote in Companion Animal on the same topic. I highly recommend each of these for you to use to review your practice protocol for anaesthesia. In addition to these resources, you can use the Dechra anaesthesia app for case planning. Here, I will discuss analgesia for caesarean section in the bitch and queen.
Providing analgesia to the mother prior to skin incision is our focus here. This can be through the use of opioids such as methadone, or the use of local anaesthetic techniques. Local techniques such as a line block or epidural will totally block signal transmission whereas opioids such as methadone will modulate incoming nociceptive transmission at the dorsal horn of the spinal cord.
Analgesia is essential and this should be provided in a pre-emptive manner. Self states that untreated pain causes a sympathetic response which will cause uterine vasoconstriction and reduced blood flow. Inadequate analgesia has also been associated with reduced milk production. So, we have clear reasons to provide analgesia to these cases.
One concern with the bitch is regurgitation, with the risk of subsequent aspiration of gastric contents. Without analgesia there is a risk that the bitch will respond to nociception. When this happens and the plane of anaesthesia lightens, there is a risk of regurgitation.
In people, inadequate pain management is associated with persistent pain, greater opioid use, delayed recovery and increased post-partum depression. If we consider options for analgesia used in humans, we have opioids, NSAIDs, incisional bupivacaine and paracetamol. To date, concerns with licensing specifics, lack of licensed options, an absence of randomised clinical studies and concerns of adverse effects have limited our use of these options in our veterinary patients.
This site here gives interesting insight into analgesic protocols in people. Note the inclusion of paracetamol and NSAIDs. What are we so afraid of?
Both Robertson and Self consider the use of methadone at doses between 0.1-0.2 mg/kg IV or IM (Self) and 0.3-0.5 mg/kg IM or IV (Robertson). Adverse effects with methadone are unlikely but should bradycardia result in hypotension, this can be treated with glycopyrrolate. Naloxone is a mu antagonist that can be used to antagonise methadone if required, for example if neonatal bradycardia is detected. Methadone is unlikely to cause adverse effects in the dam. The UK license for buprenorphine specifically states not to use this drug for caesarean section. The drive to avoid opioids in people is primarily to prevent opioid-naïve patients becoming persistent opioid users – which is not a concern in dogs and cats.
In support of using methadone as premedication, Romagnoli et al (2019) examined the use of systemic methadone 0.3mg/kg, epidural methadone 0.1mg/kg or epidural lidocaine 4.4mg/kg in bitches undergoing caesarean section. Methadone was administered 10 minutes prior to induction, intramuscularly. Neonatal vitality between groups was assessed within 5 minutes of birth using a modified Apgar score. In this study it was difficult to reliably assess mortality, because all bitches were undergoing emergency caesarean section due to foetal distress. Between puppy groups, heart rate, respiratory rate and Apgar scores did not differ.
The easiest effective local anaesthetic technique to use is a line block. Lidocaine gives the most rapid onset (5 minutes) and the aim in these cases is to remove the puppies or kittens as soon as possible after induction. Local anaesthetic is infused subcutaneously along the midline – illustrated in this video. A suitable lidocaine dose is 2-4mg/kg – which could be combined with bupivacaine (1mg/kg of each) for a longer duration of action. If you are not comfortable using opioids prior to delivery of the puppies, this is the best option for complete blockade of nociception.
For the experienced practitioner, placement of an epidural can be accomplished in minutes and provides excellent analgesia. Lidocaine (2-4mg/kg) has a rapid onset of action and can be combined with an opioid for a longer duration of effect. The use of neuraxial (spinal or epidural) morphine is advocated in people.
Attention must be paid to ensuring maternal blood pressure is maintained. Fluid therapy should be provided and mean arterial pressure kept above 70mmHg. If placental blood flow is reduced, foetal hypoxia may occur. The concurrent acidosis can cause ion trapping of drugs such as local anaesthetics.
Our third component of multimodal analgesia is NSAIDs. Debate exists over timing of administration and any hypotension or haemorrhage risk period should be avoided. Only 1-2% NSAID passes into the milk and so transfer to offspring is minimal. Another analgesic widely used in people is paracetamol. There is strong evidence that NSAIDs reduce opioid consumption after caesarean section and are even more effective when combined with paracetamol (Kehlet et al 2008).
This gives us plenty of options to take a Zero Pain approach and keep our caesarean patients as comfortable as possible, allowing them to look after their new-borns. I encourage you to use the references below to formulate your practice protocol for Caesarean sections.
References
Kehlet et al (2008) Multimodal approach to control post-operative pathophysiology and rehabilitation. British Journal of Anaesthesia 101(1) 77-86
Robertson (2016) Anaesthetic management for caesarean sections in dogs and cats. In Practice 38 327-339
Romagnoli et al (2019) Evaluation of methadone concentrations in bitches and in umbilical cords after epidural or systemic administration for caesarean section: A randomized trial. Veterinary Anaesthesia & Analgesia 46 375-383.
Self (2019) Anaesthesia for canine caesarean section. Companion animal 24 (2)
This post was written by Matt Gurney.
Matt & Carl established Zero Pain Philosophy to provide educational resources to veterinary professionals enabling optimal management of pain.
Matt Gurney is an RCVS & European Specialist in Veterinary Anaesthesia & Analgesia and works at Anderson Moores Veterinary Specialists. Matt is President of the European College of Veterinary Anaesthesia & Analgesia.
Carl Bradbrook is an RCVS & European Specialist in Veterinary Anaesthesia & Analgesia and is President of the Association of Veterinary Anaesthetists. Carl works at Anderson Moores Veterinary Specialists.