Anaesthesia and Pain Management
Anaesthesia means the loss of consciousness and sensation. The role of the anaesthesia team is to maintain patient safety before, during and after this period.
Anaesthesia at AURA
Patients that visit AURA may require sedation or general anaesthesia for a number of reasons, including diagnostic procedures, interventional treatments or surgery.
The ideal anaesthestic aims to make the patient experience as stress-free, safe, and comfortable as possible. The anaesthetic assessment typically starts before the patient even reaches the clinical floor. Prior to meeting a patient, the anaesthesia team will have reviewed the clinical notes to ensure any other illnesses and prior clinical history has been considered. A complete physical exam is then performed. This allows the anaesthesia team to tailor the anaesthetic plan to the specific needs of the individual.
Whilst under anaesthesia, each patient receives one-on-one monitoring from a dedicated member of the anaesthesia team. Every patient is connected to an electronic monitor that continuously displays heart rate and rhythm, blood pressure, pulse oximetry and other respiratory measures. This equipment helps ensure that all vital parameters are kept within the normal ranges. Any deviations or fluctuations are detected immediately and can be promptly investigated and addressed.
The recovery period is an equally important part of every anaesthesia. Patients are monitored continuously until they are aware and responsive, and do not return to the ward until the team are satisfied the patient has made a good recovery. If necessary, continuation of close monitoring will be performed for as long as the patient requires, with staff available around the clock for critical patients requiring more intensive care.
The peri-anaesthetic period begins even before a patient has reached the clinical floor. The aim is to make their experience as stress-free, safe and comfortable as possible.
Management of Acute Pain
Analgesia means relieving pain. Most patients undergoing sedation or anaesthesia will also have an analgesic plan in place to ensure optimal pain control is on-board before starting any procedure that may potentially cause pain or discomfort.
Analgesia for acute surgical pain can be delivered in a variety of ways. There are numerous drugs that can be given intravenously directly into the bloodstream, either at intervals or by a continuous infusion. In addition to this, local anaesthetics can be injected into the tissues where the procedure is being performed, sometimes using ultrasound-guidance and/or nerve stimulation to reach deeper areas. ‘Local blocks’ like this help prevent pain signals from reaching the spinal cord or brain, reducing the need for other analgesic drugs (and their side-effects).
Providing the best pain plan possible promotes a rapid return to eating and normal behaviour. This supports the overall recovery, ensuring a faster recovery and swifter return home.
Management of Chronic Pain
Chronic conditions, such as osteoarthritis or some cancers, may require a longer pain plan to maintain an acceptable quality of life. At AURA a holistic approach to chronic pain may involve offering acupuncture or electro-acupuncture alongside medications. Acupuncture is the same as in people i.e. inserting fine needles into specific target points for pain relief. Electro-acupuncture involves applying a low-level current through the needles to intensify and extend any effects. Chronic pain treatment also involves understanding important behavioural factors and elements at home that may enhance day to day well-being and comfort.
Commonly used anaesthesia procedures
Our patients range in size from a 1kg Chihuahua to a 100kg+ Mastiff! During hospitalisation, and especially whilst under anaesthesia, we need reliable access to the blood stream to deliver drugs and fluids. We often use a superficial leg vein for catheter placement for shorter procedures. For patients undergoing more involved procedures, or if we are anticipating several days of intensive nursing, we place a catheter directly into one of the jugular veins in the neck. This ‘central line’ allows our clinicians to deliver medications and fluids into the patient, as well as painlessly collect blood samples. These central venous catheters can often be maintained in patients for many days, and are generally more comfortable and less disruptive to movement than typical peripheral catheters.
The prevention and reduction of pain is an important consideration in any procedure. A combination of drugs is given to minimise the conscious perception of pain. The most effective way to prevent pain however is to block the transduction and transmission of nerves responses from the surgical site. This is achieved by performing loco-regional nerve blocks. Dentists use a similar technique in people whereby a local anaesthetic is injected around the area being operated on. The nerve block can last up to 8 hours providing a sustained pain-free period, extending well into the recovery period. The major benefit is the prevention of acute pain signals from the surgical site being registered by the pain centres of the brain and spinal cord which prevents the patient from becoming overly sensitised to painful stimuli. Consequently any post-operative pain can be more effectively controlled without the need for intensive medications in most cases.
Peripheral nerve blocks we commonly perform include blocking specific nerves of the face, forelimbs and hindlimbs. These nerves are identified by ultrasound or a nerve stimulator to accurately targeted the soft tissues around the nerve.
In some cases, local anaesthetic is injected around the nerves as they exit the spinal cord – a procedure known as an epidural. Epidural injections allow us to block pain from both hindlimbs, as well as regions around the tail and perineum, even extending up to the abdomen.
Blood pressure monitoring
Constant measurement of blood pressure when a patient is anaesthetised provides important information about the demands of anaesthesia and surgery on the body. This is particularly important where blood loss is expected, or if underlying disease may be causing instability or alteration to their cardiovascular system.
All patients undergoing anaesthesia at AURA will have their blood pressure monitored throughout the procedure. In many cases, we use non-invasive methods that provide reliable data, and is suitable for predominantly healthy patients. More critical patients, or those undergoing complex surgery, require a catheter to be placed directly into a peripheral artery, typically in the foot. This ‘arterial line’ allows real-time blood pressure measurements during surgery and recovery. While this is a more invasive technique, it allows earlier recognition of potential problems developing under the anaesthetic, so that appropriate action can be taken.
Cell salvage is the process of collecting a patient’s own blood during a surgical procedure so that it can be recycled and given back to the patient. AURA is one of very few veterinary centres in the world to routinely use this technology for their surgical patients (https://hospital.haemonetics.com/cell-salvage).
For major surgery (including liver, splenic, adrenal, thoracic or head and neck procedures), a dedicated suction device is used to collect any blood lost during surgery and any swabs are gently washed to capture the blood they contain. This collected fluid is then centrifuged (spun rapidly) to separate the blood cells from other fluid and debris. The cells are then washed and pumped into a blood-transfusion bag ready for delivery back to the patient (see video, left).
The huge benefit to the patient is they receive their own blood rather than blood from another dog, meaning the blood is safe to re-administer rapidly without the risk of a transfusion reaction.
The arrival of the cell-saving device at AURA has hugely reduced the requirement for donated blood to be used on patients undergoing major surgery. The benefit of the cell saver machine has allowed blood transfusion at AURA to become safer, cheaper and less reliant on donor supplies.
The Cell Saver was kindly donated by The Rumba Foundation via the Veterinary Cancer Research Fund a the University of Surrey. The team at AURA have been active in research projects involving the Cell Saver and details of the published work can be found at https://www.auravet.com/innovation/