Recovery from anaesthesia begins when the maintenance agent is discontinued and the patient starts to regain consciousness. The importance of patient monitoring throughout the recovery period should not be underestimated, as numerous studies in both human and veterinary medicine have looked at the increased risk of morbidity and mortality during this part of the patient's anaesthetic experience.
The Confidential Enquiry into Perioperative Small Animal Fatalities (Brodbelt et al, 2008) is frequently referred to when discussing risk factors in anaesthesia that contribute to morbidity and mortality. Whilst this study was published over 15 years ago, it is still valuable to reference because of its large multi-species study population. It found that the postoperative period, or recovery period, was the highest risk period of the entire anaesthesia experience; with 47% of dog, 61% of cat and 64% of rabbit fatalities occurring during this time (Brodbelt et al, 2008).
A more recent study by Shoop-Worrall et al (2022) looked at over 157 000 dogs across 300 practices in the UK which underwent general anaesthesia or sedation in a 4-year period. During that period, 1396 dogs died within 2 weeks of the anaesthesia or sedation, with 219 (0.14%) having the anaesthesia itself as the potential contributor to the death. Of the 219 dogs where anaesthesia being the cause of death could not be excluded, 93 (42%) of them had died on the same day as the anaesthesia or sedation, with 40 (43%) of them dying in the postoperative period.
Another study by Lindsay et al (2020) looked specifically at the postoperative complication rate of brachycephalic dogs that had airway surgery and found a complication rate of 23.4% with an overall mortality rate of 2.4%. The most common complication was dyspnoea requiring either oxygen therapy, reintubation or temporary tracheostomy.
All of these studies involve cases from routine to advanced procedures, highlighting that no matter the patient or procedure, individual risks for the recovery period should be identified and mitigated.
Reducing risk in the recovery period
Although relatively new in veterinary medicine, anaesthesia checklists in human medicine have been shown to decrease complications and mortality rates (Hohenfellner, 2009) by reducing the occurrence of human error; they encourage communication within the team, develop action plans and structure individual patient monitoring plans.
The Association of Veterinary Anaesthetists (AVA) have a checklist that covers all phases of anaesthesia, including the recovery period, which can be downloaded from their website and is shown in Figure 1.
Communication between theatre staff and the recovery team member should be similar to what occurs in a ‘rounds’ discussion, confirming the patient's signalment, drugs administered, surgery performed and any complications that occurred, e.g. hypotension or hypercapnia. The most recent physiological parameters and the current status of the patient should also be handed over.
In addition to checklists, there are many scales available that can be used to assess the quality of a patient's induction and recovery experience; however, there is nothing validated in the current veterinary literature (Wolfe and Hofmeister, 2021).
Preparing to recover
Each patient will recover differently from their anaesthetic experience, even if the same drug and doses are given as a standard protocol in the practice. The variation occurs as a result of factors including patient temperament, breed, age, existing comorbidities and procedure type.
Patients should recover from anaesthesia in an area where they can be under constant observation. There should be access to warming and cooling equipment, monitoring equipment such as pulse oximetry, emergency drugs, airway equipment and the ability to provide oxygen therapy. It is understandable that this equipment is not always available in a dedicated recovery area, so in this instance, a patient requiring this type of monitoring may need to be moved, e.g. to the prep room.
To improve patient comfort and reduce stress before the recovery of the patient, their bladder should be expressed under anaesthesia while they are still relaxed.
While recovering, the patient should be positioned in sternal recumbency on padded and absorbent bedding. A ‘lazy lateral’ may be appropriate for patients who have had abdominal surgery with a midline approach where their hind legs are positioned laterally and their thorax is sternal to avoid laying them directly on the surgical site. This positioning supports a patent airway and allows any atelectasis that has formed to reverse (Cheyne, 2010). The patient may need to be supported by pillows or rolled-up towels to keep the head raised, as seen in Figure 2.
Monitoring in the recovery period
As with general anaesthesia, observing and recording physiological trends is important and should include monitoring of the heart rate and respiratory rate, with temperature taken frequently if it does not stress the patient. This should be performed every 15 minutes at a minimum for the first hour, while the patient is under constant supervision. The patient should be under constant supervision until they can lift their head, swallow and their temperature is within 20% of their normal pre-anaesthetic values. Brachycephalic patients may require more frequent and intensive monitoring and support, including pulse oximetry.
Some patients may also require additional monitoring for hypoxaemia, arrhythmias or haemodynamic instability.
Eye lubrication should be applied frequently throughout the recovery period, as many anaesthetic drugs can reduce tear production for up to 36 hours after administration. (Jolliffe, 2016). Some patients may require eye lubrication to be dispensed at the time of discharge for ongoing care if required.
Common complications in the recovery period
The previously mentioned studies which looked at the risks of morbidity and mortality during the recovery period found that in most cases either a respiratory or cardiovascular factor had contributed to the patient's death. These are discussed further below.
Respiratory-related complications
When a patient is orotracheally intubated during anaesthesia, the airway remains patent and the efficiency of ventilation can be monitored. However, there are two stages of the patient's anaesthesia experience where the airway may be less secure or patent: after premedication but before anaesthesia induction, and during recovery after extubation.
A partial or full airway obstruction may occur due to pre-existing disease, e.g. tracheal collapse, laryngeal paralysis, laryngospasm or from anaesthesia drugs themselves which relax the soft tissue around the airway. Signs include cyanosis, stridor or stertor, nostril-flaring, paradoxical breathing, snoring or apnoea. If you suspect your patient has an airway obstruction, they should be positioned in sternal with their head and neck extended forward. Additionally, the tongue may need to be pulled rostrally as seen in Figure 3.
If there is swelling of the airway structures, corticosteroids may need to be administered and/or the patient may benefit from being nebulised with diluted adrenaline, which causes vasoconstriction in the vessels of the upper airway mucosa and reduces its size. A patient being nebulised with adrenaline is shown in Figure 4, and different protocols for nebulising dogs are in Table 1.
Table 1. Successful nebulising protocol examples used to reduce soft tissue swelling of the upper airway
| Reference | Case scenario | Protocol |
|---|---|---|
| Ellis and Leece (2017) | Postoperative nebulising to manage laryngeal swelling and oedema following surgical correction of brachycephalic obstructive airway syndrome (BOAS) in a Pug | 0.3 mg (0.05 mg/kg) adrenaline diluted into 5 ml delivered for 10 minutes, every 6 hours for 24 hours |
| Franklin et al (2021) | Pre- and postoperative nebulising in several brachycephalic breeds that had surgical correction of their BOAS | 0.05 mg/kg adrenaline diluted into 5 ml with saline for 10 minutes |
| Fenner et al (2023) | Retrospective review of 90 brachycephalic dogs that had undergone corrective airway surgery and received nebulised adrenaline postoperatively (2014–2020) | 0.5 mg adrenaline diluted in 4.5 ml of saline nebulised for 10 minutes at a frequency of the clinician's discretion (ever 1 hour, 2 hours or 4 hours), with most patients (47.8%) requiring 12.1–24 hours of treatment |
The use of a pulse oximeter in the recovery period may detect hypoxaemia as a result of respiratory depression caused by hypoventilation or airway obstruction (partial or full). In the author's opinion, a dedicated hand-held pulse oximeter is valuable to use for recovery to monitor the patient's oxygen saturation alongside temperature measurements, as shown in Figure 5. If a patient's oxygen saturation is <95% during the recovery period, they may require oxygen supplementation to increase the fraction of inspired oxygen (FiO2) via flow by, a mask, nasal prongs or by being placed in an oxygen cage.
If it is anticipated that a patient may have problems oxygenating in the recovery period, a pre-anaesthesia measurement can be obtained to guide expectations during this period. This is especially useful in brachycephalic breeds who may be chronically hypoxaemic.
Cardiovascular-related complications
Monitoring of the cardiovascular system can be performed by auscultation, pulse palpation, blood pressure measurements and with the use of an electrocardiogram (ECG) during recovery.
Blood pressure is a product of cardiac output and systemic vascular resistance, or ‘the pump and the pipes’, and haemodynamic instability is where hypotension or hypertension affects the perfusion of tissue and organs. In the recovery period, a patient may become hypotensive from hypovolaemia from continued bleeding (including oozing), which may require treatment such as a crystalloid intravenous fluid therapy bolus or surgical intervention. Hypertension during recovery is most commonly as a result of inadequate analgesia. Other reasons for haemodynamic instability include bradycardia, tachycardia or arrhythmias. A flow chart to assist in the troubleshooting and treatment of haemodynamic instability is shown in Figure 6.
Other complications
In addition to respiratory and cardiovascular complications, other complications include hypo- or hyperthermia, inadequate analgesia, rough and delayed recoveries.
Hypothermia
A commonly observed complication in the recovery period is hypothermia, which can prolong the length of time it takes a patient to recover because it slows down drug metabolism.
Hypothermic patients who shiver have an increase in oxygen consumption and they may need oxygen therapy to support this, but as shivering can be a sign of pain, a pain score should also be performed.
Patient warming should start from premedication through to recovery. A patient sitting on a HotDog patient warming system during recovery is shown in Figure 7. Take care that other heating devices do not cause burns, especially if the patient is recumbent or moving around which can mean they have direct contact with the heat source.
Hyperthermia
Hyperthermia is less commonly seen and is typically caused by overzealous patient warming, in large dogs with thick fur, or when cats have been administered opioids (Bortolami and Love, 2015).
Rough and delayed recoveries
Emergence excitement, or a rough recovery, is a ‘transient state of confusion when emerging from general anaesthesia’ and is observed as vocalisation, aggression and uncontrolled and uncoordinated thrashing in the cage (Mosing, 2016). It can be caused when the volatile agent has been abruptly discontinued or in patients where the procedure took longer than the sedation given in the premedication. A dysphoric recovery may also occur in a patient who has a distended bladder or is hungry. Occasionally, dysphoric behaviours can look similar to those of animals in pain, are hypoxaemic or in those that have an airway obstruction.
These should be ruled out before the emergence excitement is managed with the administration of drugs.
As the patient is at risk of injuring themselves or staff, they may require a low dose of a fast-acting sedative such as medetomidine, or even alfaxalone or propofol if the patient is acutely unhandleable. Acepromazine can be given before recovery but may not be ideal for managing immediate emergence excitement as the onset of action is up to 15 minutes when given intravenously, but be mindful that this cannot be antagonised.
A delayed recovery is when the patient does not respond when stimulated an hour after the anaesthesia was terminated and may be caused by excessive drug administration (e.g. not increasing the dose of a sedative for an overweight patient), hypothermia, hypoxaemia, hypoventilation, hypoglycaemia and concurrent comorbidities.
Patients with renal and hepatic disease and those with endocrinopathies may require a tailored anaesthetic approach, which often prioritises a short recovery. Individual management for these cases is beyond the scope of this article, but they generally include careful dose selection of drugs that can be antagonised or do not have a long duration of action which may have a ‘hangover effect,’ providing intraveous fluid therapy and making sure they are as stable as possible preoperatively.
Inadequate analgesia
Patients should have a pain score performed every 30 minutes during recovery (Kata et al, 2015). Each patient will have different nociceptive thresholds, even for patients who have undergone the same procedure with the same dose.
Conclusions
While it may seem like the most stressful part of a patient's anaesthetic experience is over as soon as the volatile agent has been discontinued, the patient then enters another high-risk period. This is a period that should not be overlooked and monitoring of the patient should continue, despite the pressure to move on with the day.
The RCVS Code of Professional Conduct (2023) states that ‘monitoring a patient during anaesthesia and the recovery period is the responsibility of the veterinary surgeon but may be carried out on their behalf by a suitably trained person.’ Therefore, many veterinary team members can monitor the patient and report the findings and trends back to the veterinary surgeon.
Lastly, the patient's anaesthetic experience should be thought of holistically – how the pre-anaesthesia, induction and maintenance phases of the anaesthesia have been prepared and planned will contribute to how the patient will recover.
KEY POINTS
- The recovery period is a known high-risk period.
- Patients should be under constant observation into the recovery period and the monitoring should be documented.
- Monitoring of a patient can be done by a suitably trained person, highlighting the need to use everyone in the team, such as student veterinary nurses and patient care assistants.
- How the pre-anaesthesia, induction and maintenance phases of the anaesthesia have been prepared and planned will contribute to how the patient will recover. If the patient was anxious, frightened, aggressive or very excitable pre-anaesthesia – this may be how they are on recovery too.
- Sedation drugs are not just for premedication – they can be given in the recovery period.