In 2012, Redondo et al published a study that indicated that over 80% of 1525 dogs suffered hypothermia postoperatively following a routine procedure. Throughout this article, the author discusses the nursing considerations during routine dental procedures, including thermoregulation, premedication and pain relief.
Veterinary surgeons and veterinary nurses should work together to ensure an appropriate anaesthetic plan is prepared and catered to each patient's needs. Reading the patient's clinical history and recording information from the owner will indicate if any drugs need to be altered before being administered to the patient. For example, if non-steroidal anti-inflammatory drugs (NSAIDs) were given perioperatively, there is an increased risk of depleted renal function as a result of the drug's side effects (Murrell, 2019); thus, if a patient already has low kidney parameters then NSAIDs should be avoided. Once a premedication has been chosen by the veterinary surgeon, the veterinary nurse needs to be aware of the contraindications of these drugs; for example, acepromazine interferes with temperature regulation as it causes vasodilation leading to heat loss, therefore, a heat source should be used to maintain the patient's temperature once premedicated (Aarnes and Muir, 2011; Pypendop and Ilkiw, 2012). This is particularly important during dental procedures, as a patient's body temperature will start to drop under general anaesthetic because the body cannot maintain it, while the water from the dental scaler or the dental high speed instrument used for extractions leads to heat loss (Quandt, 2018).
Pre-anaesthetic considerations
Patient history
Prior to the patient's admission, it is best practice to read the patient's history as this will direct the questions throughout the admission process. Responses to these, as well as to the comprehensive, standardised questions, will decrease the risk of mortality (Mitchell et al, 2018). A thorough patient history will enable an appropriate anaesthetic plan to be created, including the drugs required throughout the procedure, such as sedation and analgesia. The anaesthetist needs to be aware of concurrent health issues, previous anaesthetic problems, current medications and allergies, so that the appropriate measures are taken in order to decrease the risks of the anaesthetic (Browning and Tobias, 2016). The consent form is a crucial step in the admission process: without informed and signed consent by the owner the practice cannot carry out the procedure. Ensuring the owner has read the form thoroughly and is aware of general anaesthetic risks and the procedure itself is essential.
Pre-anaesthetic blood analysis
Within the consent form, the option of pre-general anaesthetic blood analysis will be offered. In the author's experience, best practice would be to carry out pre-general anaesthetic blood analysis in all patients as a precaution, this allows any abnormalities to be discovered and reduces the risk of potential peri-operative or postoperative difficulties; for example, if blood analyses are not run and the kidneys or liver parameters are abnormal, then the drugs used could worsen the parameters leading to further complications (Mitchell et al, 2018).
Most dental procedures are carried out on geriatric patients as dental issues worsen with age (Benney, 2017). For instance, if periodontal disease is untreated it progresses, so older patients are often seen with advanced stages of the disease. Davies (2012) carried out a study that found 80% of 45 geriatric dogs had undetected conditions identified on analysis of blood results, for example, liver disease, cardiac problems and metastatic lung disease. Therefore, pregeneral anaesthetic blood tests are highly recommended for most dental procedures.
Unfortunately, blood tests are not always carried out in patients undergoing routine dental procedures because some clients may not be able to afford them and do not deem them necessary (McKenzie, 2018). Mitchell et al (2018) found that 79% of patients' anaesthetic perioperative plans were altered because of the results retrieved from pre-general anaesthetic blood tests. It is unknown if these alterations perioperatively changed the patients' outcome. The American Association of Feline Practitioners (AAFP) Feline Anesthesia Guidelines suggest a minimum database of feline patients should be developed based on the individual. Some studies disagree. Alef et al (2008) concluded that taking pre-general anaesthetic blood produced little clinical relevance, which meant if nothing was detected in the history or physical examination, then the blood results were unlikely to change the anaesthetic plan. It is always the owner's choice to decide whether to perform pre-anaesthetic blood work or not but, as previously mentioned, most dental patients will be older so this option is highly advised and it is crucial for owners to know the benefits so they can make the best decision (Rigotti and Brearley, 2016).
Patient fasting
It is also important to take into consideration the prevention of gastro-oesophageal reflux. Fasting patients is essential to prevent gastro-oesophageal reflux, which can have repercussions, including but not limited to: oesophageal stenosis, oesophagitis and aspiration pneumonia (Rodriguez-Alarcon et al, 2015). This concerns all patients going under general anaesthetic, including for dental procedures. When admitting patients for any procedure involving a general anaesthetic, it is essential to determine if they have fasted. In most practices, owners are advised not to feed their dog or cat after midnight when scheduled for admission the following day, meaning 8 hours of fasting. Although, according to O'Dwyer (2016), only 2 to 4 hours of fasting is necessary to prevent gastro-oesophageal reflux. Patients that have been fasted for 12 to 18 hours or 24 hours have a higher risk of gastro-oesophageal reflux (O'Dwyer, 2016). Bradbrook (2011) suggested that fasting for more extended periods increases the risk of gastro-oesophageal reflux with the refluxed gastric content being more acidic, leading to an increased chance of damage to the oesophageal mucosa. Grubb et al (2020) explained how long food should be witheld from different patients before a general anaesthetic. For example, food should be witheld from a healthy patient for 4–6 hours whereas a puppy should not be fasted for longer than 1–2 hours. Breed predispositions also need to be taken into consideration. Brachycephalic breeds, for instance, are predisposed to many conditions, including brachycephalic obstructive airway syndrome and gastro-oesophageal reflux (Downing and Gibson, 2018). Gastro-oesophageal reflux commonly occurs in these breeds because of the high negative intrathoracic pressure required to overcome conformational partial upper airway obstruction (Shaver et al, 2016). Table 1 shows what the American Animal Hospital Association advises when fasting patients.
Table 1. Advice when fasting patients
| Health status | Withhold food for … | Withhold water for… | Feed pàté consistency wet food | Other | ||||
|---|---|---|---|---|---|---|---|---|
| 1–2 hours | 2–4 hours | 4–6 hours | 6–12 hours | 0* hours | 6–12 hours | |||
| Healthy | Yes | Yes | ||||||
| <8 weeks old or <2 kg) | Yes | Yes | YesIn pre-op period | Perform as first case of the day | ||||
| Diabetic | Yes | Yes | ¼ meal 2–4 hours prior | Perform as first case of the day | ||||
| History of, or at risk for, regurgitation | Yes | Yes | Consider feeding 10–25% of normal amount 4–6 hours before induction | |||||
Gastro-oesophageal reflux can also be stimulated by certain drugs used for premedication, such as morphine (Oramorph, GSK) (Waring, 2017). As a veterinary nurse, it is vital to be aware of the contraindications of the premedication drugs used to ensure the patient remains stable. In addition, during a dental procedure a patient can become wet and cold as a result of the water from the descaler or from the high speed drill when extracting the teeth; if acepromazine is also used as a premedication, the veterinary nurse needs to be aware of the high possibility of a rapid decline in temperature (Aarnes and Muir, 2011).
A premedication is crucial prior to general anaesthesia to provide a smooth induction and increase the chance of a stable anaesthetic (Waring, 2017). The adrenal glands produce hormones known as catecholamines when the body is in emotional or physical stress; the production of catecholamines is reduced when a premedication is administered leading to a reduced level or anxiety and problems associated with this hormone, namely, cardiac arrhythmias (Waring, 2017). A suitable premedication should ideally provide sedative and analgesic effects and be reversible, while having minimal effect on the respiratory and cardiovascular systems. This means that a combination of drugs is usually required.
Anaesthetic risk
Using an accredited physical status scale such as the American Society of Anaesthesiologists (ASA) Physical Status Classification System (Academy of Veterinary Technicians on Anesthesia and Analgesia, n.d.), is a system for assessing the fitness of patients before an anaesthetic and surgical procedure, so allows the anaesthetic risks to be quantified (Table 2)(Benney, 2017). The ASA status can be used to determine the safest general anaesthetic protocol. This should be carried out in all procedures, including dental procedures.
Table 2. American Society of Anesthesiologists (ASA) Physical Status Scale
| Status | Definition | Risk | Examples |
|---|---|---|---|
| ASA 1 | A normal healthy patient | Minimal risk | Ovariohysterectomy, castrate, orthopaedic patient |
| ASA 2 | A patient with mild systemic disease | Slight risk | Neonate or geriatric. Controlled diabetic |
| ASA 3 | A patient with obvious systemic disease | Moderate risk | Anaemia, low grade cariac disease, dehydration, liver disease |
| ASA 4 | A patient with severe systemic disease that is a constant threat to life | High risk | Shock, uncontrolled diabetes, emaciation, high fever, uncompensated heart disease |
| ASA 5 | A patient not expected to survive without the operation | Extreme risk | Severe trauma, profound shock, advanced heart disease |
Timing of the procedure
Benney (2017) explained that a dental procedure is classed as a ‘dirty’ procedure (non-sterile) meaning most veterinary surgeons include them as the last procedure of the day. Given that most dental procedures are carried out in geriatric patients, perhaps meaning a slower recovery, this is not ideal as it would be preferred for patients to have the day to recover in the practice. The preferred scenario would be to have a separate dental suite so that the ‘dirty’ procedure could be carried out first without compromising the patients undergoing ‘cleaner’ surgeries. If this is not possible, practices may benefit from having overnight staffing and facilities if a patient requires further care postoperatively, and staff should take this into account when booking in a dental procedure, especially in geriatric patients.
Perioperative care
As previously mentioned, it is crucial to know of any underlying health conditions before an anaesthetic. This includes breed-related diseases, in particular those seen in brachycephalic patients, as these breeds are more likely to suffer from airway-related anaesthetic complications (Grubb et al, 2020).
Tracheal intubation has many benefits, including preventing aspiration of any fluids and providing oxygen/anaesthetic gas to the patient (Benney, 2017). Endotracheal tubes (ET tubes) come in different shapes and sizes. Some may have a cuff which is inflated in the trachea to ensure the tube is secure and no gas can escape (Benney, 2017). It is preferred for an ET tube to be a snug fit and a cuff not to be required as this prevents overinflation of the cuff (Benney, 2017). It has been shown that 75% of tracheal ruptures occurred during dental procedures, meaning tracheal ruptures are more commonly seen in dental procedures than any other (Hardie et al, 1999). This may be for several reasons: during a dental procedure the patient needs to be repositioned as they need to be on both lateral sides, whereas sterile procedures require the patient not to be moved. If the anaesthetic circuit is not detached, the ET tube may twist or if the cuff has been inflated too much (as the veterinary team is cautious of fluid entering the trachea causing damage to the trachea) tracheal trauma could result (Adshead, 2011; Lewis, 2017). Consequently, it is best to find a tube that fits securely and make good use of a throat pack to prevent fluids from entering the trachea (Benney, 2017). Using armored ET tubes will reduce the chances of an obstruction as they have reinforced metal coils (Vijayakumar and Ganesamoorthi, 2017). Overinflation can be avoided by listening for escaping air when the patient takes a breath, when it is no longer possible to hear air escaping around the ET tube, the cuff does not need to be inflated further (Hung et al, 2020). Overinflation can cause tracheal mucosal irritation or necrosis (Hung et al, 2020).
As well as tight-fitting ET tubes, the prevention of fluid aspiration can be achieved with angling the patient's head lower than the chest in lateral recumbency and ensuring the head is angled so the fluid can flow out of the mouth rather than down the trachea, as well as the use of a throat pack (Hamlin, 2011). A throat pack is beneficial as it will prevent debris and fluid entering the trachea (Bloor, 2012). A throat pack that can absorb and release the fluid to then be used again for the same patient is preferred by the author (Figure 1) (Benney, 2017). Adshead (2011) supported the use of throat packs to prevent the risk of tracheal injury as this will reduce aspiration of fluid. For the throat pack shown in Figure 1, it is advised to remove the throat pack from the mouth and release the fluid every 15–30 minutes, depending on how often water is being used, to ensure that the airway and lungs are not compromised (Adshead, 2011). Figure 1 shows a throat pack appropriate for use in all dental patients — the water can be squeezed out of it, meaning only one throat pack is required per patient. Additionally, when it is required to be cut to a suitable size, it does not fray and ensures no material comes away from the throat pack. Some veterinary surgeons prefer not to use a throat pack as there is a worry they will be forgotten about and a patient will aspirate it on recovery, because of this it is advised to tie them to the ET tube (Bloor, 2012).
In some practices, mouth gags are not used, especially in felines, as they can occlude the blood flow. Martin-Flores et al (2014) explained that the development of central neurological deficits in felines can be associated with spring-loaded gags. In 2012 a study in feline patients by Stiles et al found a possible link between mouth props and blindness (Stiles et al, 2012). Berg (2015) noted that spring loaded gags create a constant force on the mandible and maxilla leading to a bulge in the soft tissues between the mandible and tympanic bulla, thus compressing the maxillary arteries, which are the main blood supply between the brain and retinae, increasing the risk of blindness. Smaller gags do not have the same risks, and instead of using spring-loaded gags, a smaller gag should be used, for example a 25G needle cap with the top cut off (Berg, 2015).
There are varied views on whether perioperative fluids are essential during routine dental procedures. Bloor (2012) explained that intravenous fluid therapy (IVFT) will always be beneficial to a patient undergoing surgery, especially a dental procedure, as they are usually geriatric and even a routine dental procedure can take several hours. It has been found that perioperative fluids assist in maintaining good systolic and diastolic blood pressure throughout the procedure (Bloor, 2012). IVFT promotes the supply of circulatory support to continue to provide oxygen to the tissues and continue to replace any current fluid loss or be prepared to replace fluids if required (Hill and Crompton, 2011). It is recommended to keep a dental patient on IVFT until they have fully recovered to ensure their body can control their own blood pressure (Bloor, 2012).
After considering underlying diseases and premedication used, the veterinary nurse can be better prepared on what to expect of the parameters of the patient under general anaesthetic. It is crucial to monitor patients using an electrocardiogram trace, capnography, blood pressure, pulse oximetry and temperature. The electrocardiogram trace indicates any arrhythmias and counts the heart rate. Capnography shows the inspired and expired CO2 as well as calculating the respiratory rate of the patient. It is essential to acknowledge the resting respiratory rate before the anaesthetic and when the patient is stable, as this can alter with each patient. When the respiratory rate increases, the patient should be looked at as a whole. For example, has the heart rate gone up, has the veterinary surgeon started an invasive procedure or has the temperature increased? It is often forgotten that if a patient is on fluids for several hours or has not passed urine before the procedure, the bladder may be full and need to be expressed, as this can be uncomfortable for the patient and cause an increase in respiratory rate. Blood pressure is measured using the appropriate cuff size for the patient allowing the systolic and diastolic blood pressure to be measured and the mean blood pressure to be calculated. Pulse oximetry measures the saturated oxygen within the body.
Methods to reduce heat loss should be applied after 20 minutes under general anaesthetic (Quandt, 2018); at this point the patient will already be falling into a state of hypothermia as the body cannot control its own temperature under general anaesthetic. When severe hypothermia occurs, it increases the likelihood of infection, slower recovery and death (Quandt, 2018). Best practice is to maintain the temperature between 38 and 39°C, rather than waiting for the temperature to drop further before rapidly heating the patient (Quandt, 2018). Temperature can be easily managed from the beginning of the procedure when the patient is at normal body temperature, but it can be difficult to warm up a patient when its temperature has dropped dramatically. Hypothermia can be detrimental to the cardiovascular system as well as affecting the temperature sensitive enzymes that moderate organ function and metabolise most drugs (Bowers, 2012). The author has found that using a Bair Hugger at a medium setting when a canine's or feline's temperature drops just below 38°C manages the patient's temperature throughout the procedure. There are a few ways of warming a patient, including heated tables, Bair Hugger, heat mat, and hot hands. When using hot hands and a heat mat, it is essential to not place them directly onto the patient as there is a risk of burning the patient. Hot hands can be placed on top of a blanket directly on the patient. It should also be noted that it is important that heat mats do not get wet as they are electric; this especially needs to be monitored during dental procedures as there is a lot of water involved. Intravenous fluids can be warmed up by wrapping the fluid line around the hot hands or using a fluid warmer and placing a hot hand on the anaesthetic circuit to warm up the oxygen flowing into the patient. However, Brady and Poppell (2020) carried out a study on veterinary orthopaedic patients, which found that warming up the fluids did not contribute to maintaining or increasing the patient's temperature, but a Bair Hugger did.
Intraoperative analgesia
It is crucial to provide pain relief when the patient wakes up to ensure the patient does not have a substandard recovery, especially geriatric patients and patients with mildly compromised organ function (Mills, 2016). NSAIDs are most commonly used during routine procedures and for acute pain relief (Mills, 2016). NSAIDs prevent the formation of prostaglandins leading to the reduction of inflammation and pain (Mills, 2016). Nevertheless, there are conflicted opinions on the perioperative uses of NSAIDs because of the risk of side effects, the most significant concern being that it can modulate renal perfusion (Mills, 2016). Murrell (2019) explained that there are advantages to using NSAIDs perioperatively, including as preventative and multimodal analgesia, and being the only class of drug licensed to be given at home by an owner. NSAIDs can come in liquid form, which is suitable for a dental patient following extractions, as it can be put into soft food (Mills, 2016). A patient undergoing anaesthetic has the risk of becoming hypotensive during a procedure, therefore, decreasing renal perfusion, meaning it is preferred for NSAIDs to be given postoperatively (Crompton and Hill, 2011). If NSAIDs were given perioperatively, there is an increased risk of depleted renal function because of the drug's side effects. Some veterinary surgeons will support this statement and give NSAIDs postoperatively once the patient is recovered to prevent intraoperative complications (Murrell, 2019). This then poses the question: should an opioid, for example, methadone, be used as a premedication, meaning there is a substantial pain relief on board? An opioid is a chemical that binds to receptors, which then spread out within the gastrointestinal tract and the central and peripheral nervous system, which produces analgesia effects including sedation (Ghelardini et al, 2015). Or are local anaesthetic nerve blocks an option?
Local anaesthetic nerve blocks are highly recommended to numb the extraction site area (Figure 2), as they can decrease the flow rate of the anaesthetic agent, leading to more manageable blood pressure and ventilatory depression. Local anaesthetics prevent the surgical site from conducting nerve impulses, therefore providing analgesic effects (Mills, 2016; Bellows, 2019). The most used sites for placing a nerve block are the middle mental foramen, the caudal maxillary region, infraorbital foramen and the inferior alveolar foramen (Mills, 2016). Mills (2016) confirmed that nerve blocks are essential in dental patients as they prevent nociception, meaning the patient does not experience changes in parameters, for example, heart rate and respiratory rate.
Multimodal analgesia should be recommended in patients undergoing dental procedures (McNerney and Burns, 2020). Multimodal analgesia is a combination of different analgesics that act by different mechanisms or at different sites to provide analgesic effects, while reducing the side effects for the patient by decreasing the dose of each drug (Yamaoka and Auckburally, 2013). In multimodal analgesia a NSAID, opioid and local anaesthetic nerve block are used together, reducing the patient's chances of feeling any discomfort on recovery, and in addition, eliminating vocalisation and thrashing (Mills, 2016).
Postoperative care
Patients should be discharged when clinical parameters have returned to normal, and when the patient is able to walk, eat and drink (Crompton and Hill, 2011). Knowledge of the postoperative care instructions needed to discharge the patient and inform the owner/carer after a routine dental procedure, is essential for registered veterinary nurses. Regular post-general anaesthetic instructions apply, for example, a bland diet on the day of surgery and rest for the remainder of the day. With a routine dental procedure, it is essential that the patient only eats soft food until the sutures have healed, and this also means the patient should not play with any toys or put anything else in its mouth (Hamlin, 2011). Following this, the veterinary surgeon should have dispensed some pain relief and possibly some antibiotics, depending on the surgery. Liquid pain relief is preferable for the ease of administration, but some patients may have to have tablets, at the veterinary surgeon's discretion (Hamlin, 2011). The veterinary nurse's job is to explain the dosage, frequency of administration, and how to administer (for example, with food or after food) the analgesic. Postoperative checks are completed 3 and 10 days after the dental procedure; after the last postoperative check and any extraction wounds have healed, it is vital to assist the owners in achieving a high standard of care of their pet's teeth, the current advice being daily teeth brushing (Hamlin, 2011; Stella et al, 2018). It is vital to mention that human toothpaste should not be used to brush a pet's teeth as it contains fluoride, which can lead to chronic toxicosis if ingested (Milella and Wilks, 2011). Daily brushing will prevent the progression of periodontal disease (Hamlin, 2011; Stella et al, 2018).
Conclusions
During a routine dental procedure there are multiple nursing considerations to consider. Among these are age of the patient, thermoregulation, drugs administered, and the risk of inhalation of fluids and debris.
Dental procedures are most commonly carried out on geriatric patients and there is an increased risk of hypothermia occurring as a result of the use of water during dental procedures. Veterinary nurses must be conscious of the potential risks associated with the use of throat packs and ensure they are removed before extubation.
By understanding and implementing the nursing considerations discussed in this article, veterinary nurses can optimise anaesthesia safety and improve recovery for all canine and feline dental procedures.
KEY POINTS
- It is essential for a dental patient to have a tight fitting endotracheal tube as well as a throat back to prevent aspiration of fluid and debris, the veterinary nurse needs to be aware to remove the throat pack before turning of the anaesthetic gas.
- The veterinary nurse needs to be aware of the adverse effects of premedication as some can lead to a decrease in heart rate/blood pressure or temperature which is important in a dental patient because the water used for dental procedures will cause the temperature to drop rapidly.
- Dental procedures are more commonly carried out on geriatric patients because periodontal disease develops with age. The veterinary nurse needs to be aware of this when preparing for the anaesthetic.
- Multimodal analgesia is recommended in dental patients to ensure appropriate analgesia is provided leading to a more stable recovery.
- Spring-loaded gags are not recommended, however, a 25G needle cap can be used to prop the mouth open for a short period of time. Ensuring a mouth gag is not used will prevent complications on recovery.