Are you a vet?

To view our range of veterinary products please confirm that you are a veterinarian and you will be redirected to our product list.

Yes, I am    No, I am not

Anaesthetic recovery: How can we minimise complications?


The anaesthesia period involves four different phases: preanaesthesia, induction, maintenance and recovery. The recovery from anaesthesia begins once the agent used for maintenance has been discontinued, whether it is a volatile or an injectable agent, and is when the patient starts to regain consciousness.

Anaesthesia Risk

The Confidential Enquiry into Perioperative Small Animal Fatalities (CEPSAF; Brodbelt et al, 2008) identified risk factors in anaesthesia that contribute to morbidity and mortality. The study involved 117 practices across the UK, both primary practices, referral practices and teaching hospitals. Data was collected from over 98,000 dogs and 79,000 cats that were sedated or anaesthetised within a two year period. The study concluded that the overall mortality rate was 1:601 dogs and 1:419 cats, compared to the mortality rate of 1:12,641 that has been reported in human literature (Lagasse, 2002).

The postoperative recovery period was found to be the highest risk period; 47% of dogs, and 61% of cat fatalities occurred during this time, and half of them within the first 3 hours. The main causes of death were from cardiovascular and respiratory complications.

The CEPSAF study concluded that greater patient care is needed in the recovery period, and this can easily be managed with continued patient monitoring and observation.

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; encouraging communication within the team, developing action plans and structuring individual patient monitoring plans. The Association of Veterinary Anaesthetists (AVA) have a checklist that covers all phases of anaesthesia and can be downloaded here and the associated AVA Anaesthetic Safety Checklist Implementation manual can be downloaded here.

Image 1:  AVA Anaesthesia Safety Checklist

For further information please follow these links:
Are you using safety checklists in your practice? By Carl Bradbrook.

Preparing for Recovery

Recovery from anaesthesia is multifactorial and depends on the individual patient, breed, weight, age, any systemic illness and comorbidities, anaesthesia agents used, procedure type and procedure time.

The recovery area should be in an area of the hospital where the patient can be under constant close observation. This area should be:

  • Warm and quiet with dimmed lighting for patient comfort
  • Well ventilated to eliminate any residual expired anaesthesia gases
  • Have access to pulse oximetry and blood pressure monitoring equipment
  • Have access to emergency drugs such as adrenaline, atropine, induction drugs
  • Able to provide oxygen support e.g. flow by oxygen, airway equipment
  • Have access to airway suction equipment in case of regurgitation or airway obstruction. 

Before recovering a patient, ensure their bladder has been expressed. A full or distended bladder can contribute to postoperative pain (Mosing, 2016), discomfort, and be a source of anxiety. It is easier to express the bladder by applying pressure to the caudal abdomen of a patient prior to their recovery, before the abdomen becomes tense as they regain consciousness. A rigid urinary catheter can also be passed.

The patient should be positioned on padded and absorbent bedding in sternal recumbency if possible. This supports a patent airway and allows any atelectasis to reverse (Cheyne, 2010). Avoid laying patients directly on surgical incisions.

Ensure that the eyes are lubricated into and throughout the recovery period. Many opioids, sedatives and volatile agents can reduce tear production for up to 36 hours (Jolliffe, 2016).

Handover to the Recovery Team

There should be dedicated and trained members of staff who monitor the patients in the recovery period. The handover from anaesthetist to the recovery member should be similar to a rounds discussion, and cover:

  • Patient signalment
  • Anaesthesia information including protocols used (premedication, induction and maintenance drugs, any other drugs administered)
  • Any complications that occurred (e.g. mild hypotension or hypercapnia)
  • Surgical information including the procedure performed, blood loss, any drains or lines that were placed and any bandages that have been applied (these may need to be cut off in an emergency)

The current status of the patient should also be handed over:

  • The temperature, pulse and respiratory rate (TPR)
  • The patients haemodynamic status (even if it is the trend of the last blood pressure reading)
  • The patient’s oxygen status (e.g. ‘he has been saturating well on room air’)

The postoperative plan should discuss any anticipated events, when analgesia is due, how long to continue Intravenous Fluid Therapy (IVFT), when the patient can be fed, any other special requirements and who to call in an emergency.

If anything is missed in the handover, there may be a delay in troubleshooting any complications.

Monitoring in the Recovery Period

As with monitoring general anaesthesia, recording trends is important – at a minimum a TPR, mucous membrane (MM) colour and capillary refill time (CRT) should be performed every 15 minutes for the first hour. The patient should start to respond to external stimuli within an hour of anaesthesia being terminated. Depending on the individual patient or the procedure performed, monitoring of oxygen saturation and blood pressure (BP) may also be required.

The patient can be monitored less intently and can return to wards when they:

  • Are alert and can lift their head
  • Can swallow and show control of their airway
  • The TPR is subjectively normal or within 20% of pre anaesthesia values
  • Are ambulatory (excluding patients with fractures or local anaesthesia blocks affecting any limb/s)
  • Adequate analgesia has been provided until the next assessment is due

Ideally, the patient should recover with the intravenous (IV) catheter still in place and then it can be removed.

Common Complications

Some common complications that may occur in the recovery phase are:

  • Hypothermia
  • Airway Obstruction
  • Hypoxaemia
  • Haemodynamic Instability
  • Bleeding
  • Rough Recoveries and Emergence Excitement
  • Delayed Recovery
  • Inadequate Analgesia
  • Hyperthermia

These are listed below, alongside common questions and answers on how to troubleshoot them.


  • What are some complications from hypothermia?
    • Moderate hypothermia is a temperature between 34.0-36.5°c and is commonly seen in patients recovering from anaesthesia. Hypothermia can prolong recovery by decreasing the metabolic rate and therefore drug metabolism and clearance. It can also impair blood coagulation and reduces immune system function.
  • What are considerations from shivering?
    • Shivering only occurs when the patient is over the thermoregulatory threshold of 35°c and usually stops between 36.5°c and 38.1°c (Steinbacher et al., 2010). It increases oxygen consumption up to 400% so oxygen support may need to be provided, and ensure adequate analgesia has been given. Shivering is both painful and a sign of pain.
  • How can hypothermia be prevented?
    • Start patient warming from the time premedication has been administered, keep anaesthesia time to a minimal, clip appropriate surgical site margins and use warmed skin cleaning preparations. Keep the patient covered, if possible, with blankets and booties, and use warming aids appropriately.

Airway obstruction

  • What might cause an animal to have an airway obstruction?
    • Pre-existing diseases like tracheal collapse or laryngeal paralysis, laryngospasm, a decrease in pharyngeal tone from anaesthesia drugs and swelling or oedema following surgery or trauma.
    • Anaesthesia drugs like isoflurane, sevoflurane, sedatives like acepromazine, benzodiazepines and neuromuscular blocks relax the soft tissue structures around the airway.  
  • What clinical signs would an animal that has an upper airway obstruction display? 
    • Stridor, stertor, cyanosis, apnoea and snoring indicate a partial or full obstruction of the airway. Nostril flaring and paradoxical breathing may also be observed as airway resistance increases which increases intrathoracic pressure to try to pull oxygen into the lungs.
  • When should the endotracheal (ET) tube be removed in cats and dogs?
    • Dogs – When they swallow or no longer tolerate the ET tube.
      Cats – Topical lidocaine applied to the larynx for intubation has a duration of 15 minutes, so the larynx will be resensitised again at the end of the anaesthesia. To avoid laryngospasm, extubate when there is a palpebral reflex or ear twitch. Laryngospasms are usually self-limiting, however extend the neck and provide oxygen support. Rarely, the need to induce anaesthesia and apply local anaesthesia to the larynx +/- ET intubation may also be considered.
  • How can I maintain a patient’s patent airway due to relaxation of the pharyngeal tissue?
    • Extending the head and neck forward, pulling the tongue out of the mouth, placing a gag between the patient’s teeth to keep their mouth open (e.g. with a bandage role), placing the patient in a sternal position.
    • Pharyngeal tissue relaxation usually occurs as a result of the anaesthesia drugs used, so consider if there are any that can be antagonised.
  • What should you do if the patient regurgitates or vomits in recovery?
    • Many anaesthesia drugs relax the oesophageal sphincter which may predispose patients to gastroesophageal reflux or regurgitation.
    • Place the head below the level of the stomach to allow the material to drain from the mouth. Afterwards, position the patient’s head higher than their stomach.
    • If the patient has regurgitated during anesthesia, then the oesophagus should be flushed with water and suctioned to avoid accidental aspiration in recovery and avoid the formation of oesophageal strictures. The patient should also be extubated with the ET tube cuff partially inflated to draw any material from the trachea.
    • If you have a patient at risk of regurgitating or vomiting, they can be managed preanaesthesia with gastroprotection and antiemetics
  • How can airway swelling or oedema be managed?
    • Corticosteroids can be administered or nebulize saline with epinephrine.
    • Ellis & Leece (2017) reported a dilution of 0.3 mg epinephrine into 5ml of sterile saline (not water) and nebulising this for 10 minutes every 6 hours for 24 hours to manage a case of airway obstruction in a pug.

Image 2: An “airway box” for a patient that has a high risk of respiratory obstruction in the recovery period.


  • What is hypoxemia?
    • Hypoxemia is defined as an arterial Partial Pressure of Oxygen (PaO2) less than 60mmHg, which corresponds to an SpO2 <90%. This means there is a low amount of oxygen in arterial blood.
  • Why might a patient become hypoxemic in recovery?
    • Hypoventilation – from residual anaesthesia drugs, hypothermia or increased intracranial pressure.
    • Airway obstruction or airway disease (e.g. BOAS patients, feline asthma, Acute Respiratory Distress Syndrome (ARDS)).
    • Diffusion impairment or ventilation/perfusion mismatch – this is when there is a problem with how oxygen diffuses from the alveoli into the capillaries that surround them. Not all alveoli are being perfused, or not all perfused alveoli are being ventilated. It can occur in cases of atelectasis, pneumonia, airway disease and fluid overload.
    • Atelectasis, or the collapse of parts of the lung – this commonly occurs under anaesthesia because of patient positioning, and from breathing a high concentration of oxygen under anaesthesia, but it is usually self-limiting in the healthy patient. 
  • How can the hypoxaemic patient be supported?
    • Provide oxygen supplementation to increase the Fraction of Inspired Oxygen (FiO2) through flow-by, an oxygen mask or cage, or nasal prongs. Some anaesthesia drugs may need to be antagonised. Position the patient in sternal recumbency.
  • How can oxygen saturation and hypoxaemia be monitored?
    • Use a pulse oximeter to obtain an SpO2 reading or perform a blood gas analysis. Cyanosis is only visible when the SpO2 is <85%, but even still the human eye cannot detect it for some time.

Image 3: Pulse oximetry monitoring in a brachycephalic dog.

For further information please follow the links:
Practical pulse oximetry. By Courtney Scales
Considerations for anaesthesia of the brachycephalic dogs. By Matt Gurney

Haemodynamic Instability

  • What does haemodynamic instability mean?
    • Haemodynamic instability is defined as an unstable BP causing perfusion failure. The BP may be high or low.
    • As the BP is a product of Cardiac Output (CO) and Systemic Vascular Resistance (SVR); both the heart rate, contractility, preload and afterload should be considered alongside the tone of the blood vessels and the volume of circulating blood. 
  • What can affect the blood pressure in the recovery period?
    • Hypovolemia – this may be from bleeding or dehydration. A crystalloid IV fluid bolus may help with this, but after an hour most of that fluid will have shifted compartments and the patient may become hypovolemic again.
    • Electrolyte disturbances and pH changes – this can cause haemodynamic instability (e.g. hypo- or hyperkalemia causing bradycardia).
    • Bradycardia – this may be drug induced or caused by hypothermia.
    • Tachycardia – this can be due to hypovolemia, pain, shivering or excitement.
    • Arrhythmias – these may be drug induced (e.g. medetomidine), seen after a splenectomy or GDV surgery, or in the case of electrolyte disturbance or heart disease. Arrhythmias may cause bradycardia, or tachycardia which will not allow adequate filling time of the heart’s chambers. 


  • What can cause bleeding postoperatively?
    • A ligature that has slipped or a vessel that was not successfully ligated during surgery. Also consider if the procedure being performed may cause bleeding in general e.g. liver biopsies.
    • Coagulopathies – these should be investigated prior to anaesthesia and surgery e.g. 50% of Doberman Pinchers in the UK are affected by von Willebrand Disease (vWD; Brewer, 1998) which is when they lack a specific protein to make platelets stick together. Consider if the patient has other types of platelet dysfunction or thrombocytopenia. 
    • A BMBT (buccal mucosal bleeding time) can be easily performed in practice. A normal reading is less than 4 minutes. 
  • How can bleeding be monitored?
    • Look for any skin discolouration, and increase in HR and a decrease in BP, and MM colour becoming pale. Additional IVFT or blood products may need to be administered.

Rough Recoveries and Emergence Excitement

  • What is emergence excitement?
    • It is defined as 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 is commonly seen in geriatrics and some excitable breeds (e.g. Huskies, Staffordshire Bull Terriers), and in patients who did not receive suitable sedation in their premedication, or where the procedure was longer than its duration of action. 
    • It can be seen when there is a fast recovery from volatile agents (like isoflurane or sevoflurane) after they are terminated suddenly; this highlights that volatile agents should be tapered slowly towards the end of anaesthesia.
  • What behaviour also looks like emergence excitement?
    • Pain, the stress of hypoxia, and airway obstruction can look like emergence excitement, however this is considered a dysphoric recovery.
    • Is the patient anxious? This may stem from hunger or bladder distention; if so, offering a small amount of food if appropriate is an option and ensure the patient’s bladder is expressed prior to recovery.
  • How to manage emergence excitement?
    • The patient is at risk of injuring themselves or staff if it is not managed appropriately.
    • Assessment of the analgesia plan and a pain score should be performed immediately as this is will contribute to a dysphoric recovery.
    • If not contraindicated, a low dose of a fast-acting sedation/anaesthesia drug like medetomidine, alfaxalone or propofol can be given. Acepromazine (ACP) can be given prior to recovery, or after the fast-acting sedative to smooth the subsequent recovery; the onset of ACP is 15 minutes if given IV.
    • In the author’s hospital, ACP is given at a dose of 5mcg/kg IV, and medetomidine is given at a dose of 0.5-1mcg/kg as required.
    • Dim the lighting in the room if possible and reduce any exciting stimuli (e.g. excessive stimulation from personal, loud radio).

Delayed Recovery

  • What is a delayed recovery?
    • When a patient does not respond to external stimulation within an hour after the anaesthesia is terminated.
  • What contributes to a delayed recovery?
    • Delayed or slow recoveries can be multifactorial, but usually it is because of residual anaesthesia drugs. Recovery depends on the redistribution of the drug between blood and tissue, and elimination depends on their metabolism and excretion capabilities.
    • Consider if part or all of the sedation drugs can be antagonised e.g. an overweight patient may have received a higher dose than required, or does the patient have liver disease which may prolong the metabolism of anaesthesia drugs.
    • Hypothermia can decrease the metabolic rate and drug clearance.
  • What other factors may contribute to a delayed recovery?
    • Hypoxemia, hypoventilation and hypoglycaemia (neonates/paediatrics/diabetics). Comorbidities such as neurological disorders, endocrine disease, liver disease, renal disease may cause delayed recoveries.
    • If the patient has comorbidities, it is easier to prevent or prepare for problems from premedication than it is to try and manage them in the recovery period.
  • How can endocrinopathies affect recovery?
    • The anaesthesia aim with these patients is to get them back to their normal routine as soon as possible – use drugs that don’t have a ‘hangover effect’. Use short acting drugs (which ideally can be antagonised if required) and lower doses.
      • Diabetes Mellitus: ideally, they are stable prior to recovery. Take blood glucose readings every 30-60 minutes and get them back to their insulin and feeding regime as soon as possible. Provide water and allow them to void urine in a litter tray or outside as soon as it is suitable.
      • Hypothyroidism: these patients tend to be obese and have a slower metabolism, so lower drug doses should be used. They may have respiratory depression and weakened respiratory muscles, as well as peripheral neuropathies which may cause laryngeal paralysis. Monitor for bradycardia and hypotension.
      • Hyperthyroidism: monitor for tachycardia and hypertension, they may also have hypertrophic cardiomyopathy. Cats are usually underweight with reduced muscle and adipose tissue, so drug doses may need to be reduced. Include geriatric anaesthesia considerations. 
      • Addison’s Disease (Hypoadrenocorticism) – steroid replacement should be started prior to anaesthesia as these patients cannot tolerate stress. Monitor electrolytes (hyponatraemia, hyperkalemia) and treat accordingly. ECG and BP should be monitored due to bradycardia and hypotension. 
      • Cushing’s Disease (Hyperadrenocorticism) – these patients may have diabetes as a comorbidity. Monitor for respiratory compromise due to enlarged liver and weakened respiratory muscles. Hypertension is common. Patients with Cushing’s Disease are hypercoagulable and are at risk of pulmonary thromboembolism; monitor for acute dyspnea, tachypnea and cyanosis. They may also have fragile skin.

For further information on anaesthesia for canine Cushing’s patients please follow this link.

  • How can liver disease affect recovery?
    • Patients with liver disease may not have the ability to metabolise anaesthesia drugs effectively, so certain drugs should be avoided or doses should be lowered. They may also be hypoalbuminemic; as most anaesthesia drugs are highly protein bound, if there is lower protein available then there is more unbound drug in circulation which could cause a subjective overdose.
    • These patients should also be monitored for hypoglycemia as there is an impaired function to convert carbohydrates, fats and proteins into glucose.
    • Patients are prone to hypothermia as the liver usually generates heat with its metabolic activity and this is impaired.
  • How can kidney disease affect recovery?
    • Patients with kidney disease may have problems with maintaining fluid balance which can lead to dehydration and electrolyte imbalances during the entire anaesthesia period.
    • Continuing IVFT and maintaining perfusion into the recovery period will support a smoother recovery and can support excretion of some anaesthesia drugs.

Inadequate Analgesia

  • How often should a pain score be performed?
    • Every 30 minutes during recovery (Kata, Rowland and Goldberg, 2015), especially before analgesia is due and 15 minutes after it has been administered to ensure the dose was adequate. Individual patients may have different thresholds for common procedures, therefore the dose range of a drug and a multimodal approach to analgesia should be considered.
  • What are pain scoring considerations in recovery?
    • Has the patient received a sedation which means they may not respond appropriately (e.g. ACP)?
    • Some pain scales have a ‘lameness” or ambulatory score which should be discounted when there are fractures or local anaesthesia blocks affecting any limb/s.
    • Many validated pain scoring systems have a threshold at which analgesia should be administered – like a score of 6/24 for dogs when using the Glasgow Composite Measure Pain Scale. Some pain scoring systems have a behavioural section that gives a score for vocalisation – this can be affected by the breed or stress of the patient, and therefore affecting the overall result. Performing a pain score prior to the procedure may help to guide pain score monitoring in the post-operative period.
  • What are some of the side effects of opioids?
    • Bradycardia, depression of the respiratory center, urinary retention, panting in dogs (resets thermoregulatory set point), decreased gastric emptying time and gut motility, euphoria/dysphasia if animal is not in pain, sedation.

Image 4: Glasgow Composite Pain Scale–Short Form 

For further details on pain, pain scoring and management please follow these links:
The physiology of acute and chronic pain. By Ian Self
Practical Acute Pain Assessment. By Carl Bradbrook (includes links to download the Glasgow Composite Pain Scales and to order the Rabbit Grimace Scale).


  • Why does hyperthermia occur? 
    • Hyperthermia is a temperature over 39.2°c, but it is less commonly seen in the recovery period. It can occur in large dogs with thick fur, when low flow anaesthesia is used or the use of circle breathing systems which preserve heat and moisture, with overzealous patient warming, not monitoring temperatures during anaesthesia, and in cats given opioids (Bortolami and Love, 2015).
  • How can hyperthermia be treated?
    • Actively cool the patient; place them onto a cool floor, use fans and ice packs (do not trap the patient under a wet towel)
    • If opioid induced, stop administration and consider antagonising.
    • Stop active cooling when the temperature is 1°c from normal.


The recovery period is a high-risk period that should not be overlooked at part of the patient’s perioperative experience.

How the preanaesthesia, induction and maintenance phases of the anaesthesia are performed will contribute to how the patient will recover.

Article by
Courtney Scales
DipVN, NCert(Anaesth), RVN

Courtney is originally from New Zealand where she trained and qualified, and has been working as a Veterinary Nurse since 2007. After working in a number of small animal clinics there, an anaesthesia passion took her to a large referral hospital in Australia in 2015. In 2016 she came to the UK and is now an Anaesthesia RVN at the Royal Veterinary College.

Courtney completed her Nurses Certificate in Anaesthesia in 2017 and throughout her studies, she started Veterinary Anursethesia on various social media platforms to share anaesthesia tips. She has written a number of articles for journals and speaks at congresses for Student Veterinary Nurses and Registered Veterinary Nurses on anaesthesia.