For many in general practice, the thought of monitoring a rabbit under anaesthesia might immediately instil a sense of discomfort and anxiety. These feelings may be due to the individual not knowing the basics of rabbit anaesthetic monitoring and not having enough experience, or it may be a result of knowing that, factually, rabbit mortality rates are usually higher compared to cats or dogs. However, with advances in veterinary surgery and medicine ever increasing and our client base becoming wider, it is imperative that the vet-led team is comfortable with, is knowledgeable about and has an understanding of the basics of anaesthesia when treating companion rabbits.
An introduction to anaesthetic monitoring in rabbits
Rabbits are a prey species, therefore everything we do from the moment they enter the veterinary practice must be tailored to meet their prey-specific needs. Keeping this fundamental principle in place will go a long way to ensuring your rabbit is stress free. This will, in turn, have positive effects on the procedure that lies ahead.
When the author views anaesthesia, they like to look at it with a multimodal approach in mind, thus ensuring every step of the anaesthetic process has been thought about and every phase has been covered. A multimodal approach to rabbit anaesthesia can be divided into five stages (Welsh, 2003): pre-anaesthesia, premedication, induction, maintenance (airway management and patient monitoring) and recovery (post-operative care). The pre-anaesthetic period is when the patient is checked, and an anaesthetic plan is put in place. Here, age and any underlying disease or illness that may compromise the anaesthetic are taken into consideration. The next stage involves premedication, where the most suitable patient-specific premedication is administered. Then follows induction, maintenance and recovery.
It is also worth remembering that rabbits are very good at hiding pain (Varga, 2016). Do not underestimate this factor when planning, preparing for and carrying out anaesthesia and providing appropriate analgesia for rabbit patients.
Pre-anaesthesia
When the client arrives at the practice, ensure that they are seated in an area free from predators and in a way that ensures predator and prey species cannot see each other: ideally, this would be a dedicated and protected area for exotics. If the client has not already done so, offer to cover the rabbit’s carrier with a blanket to help the rabbit remain calm. If a predator species has been in the area, ensure the area has been disinfected thoroughly, and make sure noise is kept to a minimum. The use of calming diffusers may also aid in keeping rabbits settled.
Keep noise to a minimum and only handle the patient when absolutely necessary. Too much restraint and unnecessary handling can exert undue stress and anxious behaviours
Carry out the consult in a separate room away from predators or have a dedicated consultation room for exotics. Once in the consult, keep noise to a minimum and only handle the patient when absolutely necessary. Too much restraint and unnecessary handling can exert undue stress and anxious behaviours (Bradbury and Dickens, 2016). Scruffing a rabbit is unnecessary and, for welfare reasons, is not advocated as it can be extremely traumatic by mimicking a predator, thereby causing more stress for the patient. Instead, allow the rabbit to relax and explore the consult room where possible.
Following this, the ward area should, again, be free of predator species and disinfected thoroughly to remove any predator scent if they have been hospitalised there. It is ideal for the rabbit to be hospitalised in a separate small mammal ward,where they can display their natural behaviours. If this is not possible, place them in other areas, such as isolation or the X-ray room, where noise is minimal and the number of people entering is low.
Prepping the patient for induction
Once settled in the ward, it is ideal to prepare the patient with an intravenous catheter. In the author’s experience, placing the catheter in the marginal ear vein works very well (Figure 1), but using the cephalic or saphenous vein can also be attempted. An important note: do not place the catheter in the auricular artery as this can lead to thrombosis and necrosis of the area (Girling, 2013) (Figure 2).
It is strongly recommended to use Emla cream (lidocaine 2.5 percent and prilocaine 2.5 percent) on the area to be catheterised. Applying Emla at least 20 to 30 minutes prior to placing the catheter will reduce discomfort (Chung et al., 2022). In addition, if the rabbit is particularly stressed and fractious, a benzodiazepine (such as midazolam) can be administered before catheter placement and premedication to reduce stress and allow for smoother placement.
Induction
It is vital to allow premedication drugs to take effect for at least 10 minutes, depending on the route of administration. During this time, the registered veterinary nurse (RVN) should ensure the rabbit is in a calm, quiet and dimly lit area and intermittently yet quietly check the patient to ensure it is stable. Commencing induction before this can lead to a stressed rabbit that is unamenable to induction and intubation.
It is vital to allow premedication drugs to take effect for at least 10 minutes, depending on the route of administration
Allowing the drugs to be absorbed for the full 10 minutes is also beneficial as it reduces the amount of induction agent necessary. In addition, due to the unique physiology of rabbits, they have different responses to various drugs. For example, because rabbits have high circulating volumes of atropinase, atropine is rapidly broken down, making it ineffective (Heskin, 2019). The author has found glycopyrrolate more effective.
Once premedication has taken effect, the nurse should provide flow-by oxygen and allow the vet to assess the depth of anaesthesia. At this stage, the patient will either be suitable for intubation (depending on the type of premedication)or not. If it is not, alfaxalone can be administered in small amounts; it can be diluted with saline to provide a safer, slower and much smaller incremental administration. When the necessary depth of anaesthesia is reached and the patient is ready for intubation, positioning the rabbit is the next step.
Airway management
It is important to position the patient in a way that allows intubation to be carried out the most smoothly (Figure 3). In order to achieve this, the patient’s body should sit sternally, its head should be held vertically with one hand and the practitioner should place the stethoscope under the thorax with the other hand to monitor heart rate and listen to any changes that may occur (Figure 4).
At this stage, it is crucial to monitor respiratory rate, heart rate and membrane colour continuously. Membrane colour can be checked by assessing the gums; however, a more practical way is to check the conjunctiva (Figure 5).
Once intubation has been achieved, capnography is important to ensure accurate ventilation status.
If intubation is not possible, placing a tight-fitting mask around the mouth is a suitable alternative (Figure 6). Ensure no inhalational gas leakage occurs – using vet wrap or cotton wool wedged around the mask can aid this.
Monitoring
Once under general anaesthesia, the RVN should ensure the patient’s body temperature is maintained within the range of 38.5 to 40°C. As well as keeping the room temperature warm, heat pads, bear huggers and bubble wrap can help maintain optimum body temperature. (When in theatre, the author’s warm air con is set at 25°C and above.) Monitoring and maintaining body temperature is crucial because rabbits have a high surface area to body ratio, so heat can be lost quickly (Cantwell, 2001). Carrying out minimal hair clipping and using warm scrubbing solution will also aid this. However, it is essential to remember that rabbits cannot sweat or pant to release heat (Varga, 2014a), so be mindful when using various heat sources.
If the patient is to receive fluids, it is imperative to warm the fluids before use – a Tommee Tippee warmer is very useful for this (Figure 7). The author’s hospital administers fluids at 10ml/kg to patients undergoing procedures such as neutering. When the patient is under general anaesthesia, fluids are given slowly and intravenously over 15 minutes (thus reaching 2.5ml/kg over this period). If the fluids are not completely given throughout the surgery, the remainder can be administered on recovery.
During the anaesthetic procedure, placing a small rolled-up towel under the thorax will help keep it, and the patient’s head, raised (Figure 8); this helps reduce the pressure from the gastrointestinal contents on the diaphragm. In addition, it is important to note that rabbits do not need to be starved prior to general anaesthesia as they cannot vomit (Varga, 2014b). Starving them can, instead, lead to ileus.
Clinical parameters in the rabbit undergoing anaesthesia
Parameters such as jaw tone, eye position and pedal reflex cannot be used to determine the depth of anaesthesia in rabbits. This is because rabbits’ jaw tone always remains a little taut and eye position is usually always central. Research shows thattesting pedal reflex is not an accurate representation of anaesthetic depth, especially in a prey species. However, pedal reflex may be present and can help, but carrying this out in a prey animal usually elicits a fear and flight response as opposed to representing anaesthetic depth, so be mindful when using this parameter and remain aware of the situation it is being used in.
The vitals that should constantly be monitored are:
- Temperature
- Heart rate, using a stethoscope or Doppler (Figures 9 and 10)
- Respiratory rate
- Mucous membrane colour
- Capillary refill time
- Pulse oximetry
- Blood pressure
- Capnograph readings
Baseline parameters are shown in Table 1. The patient can also be attached to a mechanical ventilator or be manually ventilated if respiration is unstable or apnoea occurs. Apnoea is common in rabbit patients and can occur for several reasons, including the type of drugs used, if the anaesthetic depth is too deep, breath holding or imminent cardiac arrest (Sibbald, 2018).
When extubating the patient, the RVN should monitor the patient’s heart and respiratory rates, which will begin to rise, and ensure the patient’s body temperature is within the appropriate range. A palpebral reflex may be present, and jaw tone will get tighter. The RVN does not need to wait for the tongue reflex to return before extubating and should not need to pull on the tongue “to check”. Rabbit patients may also exhibit a slight cough; if you hear this and the parameters are rising or within the normal range or the patient moves, then extubate the patient.
| Basic parameters | Domestic rabbit |
| Rectal body temperature (°C) | 38.5 to 40.0 |
| Respiratory rate (at rest) | 30 to 60 breaths per minute |
| Heart rate (at rest) | 130bpm (New Zealand Whites) to 325bpm (Netherland Dwarf) |
| Blood pressure | Systolic: 92 to 135mmHg Diastolic: 64 to 75mmHg Mean arterial: 80 to 90mmHg |
Post-operative care
Following extubation, the RVN should monitor the patient’s recovery closely, checking their vitals approximately every 5 to 10 minutes, or sooner if needed. Maintain the patient’s body temperature by placing them in an incubator and continue to administer the remainder of the fluids if not done so during surgery.
The rabbit should be syringe fed as soon as they are awake and able to swallow. The author’s hospital syringe feeds at a rate of 10ml/kg five times a day and stops feeds at midnight so the patient can rest. During this time, other foods, such as hay, fresh herbs and vegetables, are offered. For example, a 2.1kg rabbit will be fed 21ml of Oxbow recovery feed at 8am, 12pm, 4pm, 8pm and 12am. The author usually does not syringe feed patients prior to a general anaesthetic if the rabbit is healthy.
Following extubation, the RVN should monitor the patient’s recovery closely, checking their vitals approximately every 5 to 10 minutes
Lastly, ensure adequate analgesia is administered. Following neutering procedures at the author’s hospital, rabbits are hospitalised overnight and administered buprenorphine at 0.05mg/kg every six to eight hours, with regular pain scoring.
Take-home messages
- Remember this crucial fact at all times: rabbits are a prey species, so tailor everything you do within the hospital according to this simple species rule
- Where possible, place an intravenous catheter. Applying Emla cream 20 to 30 minutes prior to catheterisation will be beneficial for the rabbit. The marginal ear vein works well, but the cephalic or saphenous veins can also be attempted
- Calculate the patient’s emergency drugs before carrying out the procedure. If needed, draw up any drugs as well. This is imperative when an emergency occurs and will cause less stress and anxiety for the staff involved
- If you are using a premedication, such as a triple combination, allow a minimum of 10 minutes for it to take effect. During this time, ensure the room is quiet and dimly lit or with lights turned off, and that the patient is kept away from predators. Carry out intermittent checks on the rabbit calmly
- When monitoring the anaesthetic, keep a close eye on pulse rate, respiratory rate, temperature, mucous membrane colour, capillary refill time, capnograph values, blood pressure and pulse oximetry
- Maintain capnograph values: ETCO2 should be between 35 and 45
- In rabbits, eye position does not change during anaesthesia regardless of depth
- Lubricate the eyes regularly to prevent them from drying and corneal ulcers forming
- If administering fluids, ensure they are warmed and given slowly intravenously
- When extubating, do not rely on jaw tone or tongue reflex; do monitor pulse and respiratory rate, temperature, palpebral reflex (remember checking this constantly can exhaust the area) and any movement
