Recovery concerns and pain scoring (Proceedings)

Introduction

The recovery period is a very important period where vigilance is the key as complications such as hypoventilation; hypoxemia, hypothermia, pain, and excitation are not uncommon. It would be wrong for an anesthetist to think that his/her job is over once he/she turned off the anesthetic. In this chapter we will look at common complications, their cause and possible ways to prevent and/or treat them.

Recovery

There are many factors involving a safe smooth recovery for the small animal patient. If most recoveries are quite, some can go horribly wrong. All animals recovering from anesthesia must be monitored continuously for any potential complications. The environment should be quiet and comfortable; Cages should be padded with some form of cushion such as foam mats, towels, rubber pads, etc. It is desirable to use materials that are easy to clean as animals can defecate, urinate, reflux, vomit, as well as ooze from surgical wounds. Cleaning/disinfectant materials should be easily accusable. There should be items available such as body warming devices, thermometers, needles and syringes, heparinized saline, extra drugs such as analgesic, sedatives. It is desirable to have the recovery area be a separate room from the rest of the hospital that does not have much traffic. Some recovery areas have dimmer lighting for patient comfort as well. There should be an emergency cart around as well as oxygen for managing potential cardiopulmonary complications. This can be used to house all supplies necessary for patients recovering. If possible try also no to mixed species so that cats would not be stressed because of barking dog for example.

Recovery Complications

Patient not regaining consciousness

Causes for prolonged recovery are multifactorial. To list a few: drug overdosage, injection of an opioid (morphine) just before recovery, poor metabolism, and hypothermia.

Extubation Concerns

When the patient begins to regain certain reflexes as well as muscle tone, the anesthetist needs to be aware of the timing of extubation; the removal of the endotracheal tube. In preparation for this, deflate the cuff of the tube and try to position the animal in a position where ventilation is easy for the patient. Open up the airway by hyper-extending the head. Remove the tie used to hold the tube to the head. A strong swallow usually indicates the time for extubation. If airway obstruction does occur, injectable drugs should be close by to administer to the patient to aid in re-intubation. This is critical time as there are many potential complications that may arise. Some complications associated with extubation are damage to the larynx (more common in small species such as cat, ferret and rabbit). This can come from pulling out a cuffed tube, or frequent manipulation of the tube as it is being pulled out. You may also see hematoma formation and edema. A patient with increased jaw tone may make it difficult to pull the tube out. The tube can be chewed in half if the patient becomes too light; patient can then aspirate the distal portion. If the procedure involved blood or if there is reflux material in the mouth, the larynx needs to be flushed with saline, and dried prior to extubation so as to avoid aspiration. Visually examine the larynx with a laryngoscope before patient begins to regain jaw tone. In consideration of upper airway obstruction; patients that have brachycephalic syndrome or any other disease process that inhibits proper function of the upper part of the respiratory system should be considered an increased risk and delivery of oxygen via face mask should take place in recovery. Try to keep the tongue pulled forward out of the mouth as this may obstruct the airway. These patients may also need ventilatory support. The use of steroids and non-steroidal inflammatory drugs has been used to keep inflammation/ swelling down in the upper airway to protect patients from obstruction and reversal of anesthetic drugs may be necessary to expedite recovery. Cats can laryngospasm if they become too light, so do not delay the extubation process. Emergency tracheotomy may be necessary to gain access to an airway if there is obstruction for any reason.

Vocalization and Excitement

After extubation, the patient should slowly come to an awake state. This may take anywhere from minutes to hours. Ideally, this stage should not take too long as the longer the recovery, the more potential for problems such as respiratory depression and hypothermia. A comfortable animal should ideally wake up quickly and calmly. Sometimes they may vocalize. This may be coming from one of many reasons. An animal may wake up excited due to the rapid metabolism of certain drugs or there may be drugs on board causing excitement without there being enough sedation for the patient If there is much stimulation such as noise, touching, bright lights, etc, this may stress out the patient causing them to vocalize and thrash around. Sometimes this will last a short time. If it's prolonged or dangerous to the patient or recovery person, sedation should be considered to slow down the excitement. Animals can wake up painful, stressed, uncomfortable or a combination of all three. If the correct analgesic was not used or if analgesia has worn off or has not been administered at all, Dogs can wake making all kinds of sounds from a small whimper to loud screams. Cats may growl, or purr. There should be relief analgesia available. Patients may wake up dysphoric. This is not uncommon. It's usually an effect from opioid administration. This may cause them to vocalize. Careful monitoring is essential. If a dysphoric animal is given more opioid because it was thought they were painful; the delirium can become worse. They may just need to extra sedation and a quiet cage or drug reversal.

Shivering

It is common to see shivering in the post-operative period. Most commonly this effect is due to anesthesia induced hypothermia, but it can also be from fear, pain or a combination of all three. It is important to remember that shivering will increase the patient's oxygen consumption, therefore try to resolve the issue causing the patient to shiver and monitor the patient's oxygenation

Hypoventilation

In the recovery period, it is common for patient's to have respiratory depression induced by anesthetic drugs, respiratory disorders or a combination of the two. Monitor ventilation visually. Make sure patients can comfortably move their chest wall. Auscultate for any abnormal respiratory sounds. Ventilation and oxygenation can be supported with an Ambu bag (if still intubated) and or oxygen insufflation. This will increase a patient's PaO2. (arterial oxygen pressure). Excessive increases in PaCO2 (arterial carbon dioxide pressure) or moderate hypoxemia can contribute to poor organ function and can lead to anesthetic fatalities. If the respiratory depression is due to the anesthetic drugs, consider partial or full reversal (while still providing analgesia). Make sure the patient can comfortably move his/her chest wall; nothing is impeding airflow coming in and out of the upper and lower parts of the respiratory system. If the patient has had thoracic surgery, make chest tube is checked for drainage frequently and there is no evidence pain or discomfort. Both of these can cause hypo/hyperventilation and or hypoxemia if not monitored appropriately.

Hyperventilation

An increase in ventilation can be from many different problems including pain, stimulation, excitement, respiratory/ metabolic acidosis. Again, monitor mucous membranes, supply oxygen as necessary and monitor ventilation. Try to find the cause of the hyperventilation and choose appropriate action.

Pale Mucous Membranes (MM)

Pale mucous membrane color can be indicative of pain, anemia, poor circulation, and hypoxemia. When patients begin to wake up, they can regain vasomotor tone; this may cause pale mucous membranes. Some breeds will also appear to look pale but the coloring is normal for them.

Cardiovascular Changes

There will be anesthetics remaining in your patient. This will alter the cardiovascular physiology. In recovery, the patient will usually go through an excited stage. An increase in sympathetic tone will occur when recovering. This will increase heart rate (HR) along with blood pressure (BP). There will be an increase in cardiac output (CO). There may be an increased risk of arrhythmias as well as impair cardiovascular function. If the patient is respiratory depressed, this may make the situation worse. Careful monitoring of pulse quality, HR, mucous membrane color as well as cardiac auscultation will help you recognize any problems.

Pain and Discomfort

Animals have similar pain pathways as humans; therefore you MUST assume an animal is in pain. Response to pain is influenced by factors such as:

1. Species

2. Area or location affected on body

3. Animal's age

4. Environment (new place/together with other species/ noisy room)

5. Breed

6. Gender

7. Any conditioning the animal might be predisposed to

8. The temperament

9. Disease process and or medication

10. Comfort (clean bandage & cage).

Pain Scales

As pain is a very subjective matter and as animals do not speak, pain scales have been developed to help us evaluating pain in a more objective way

Numerical rating scales are not very sensitive. The observer put a number from 1 to 5 or 1 to 10, 1 being no pain at all while the other side of the scale corresponds to the worse pain possible.

Visual Analogue Scale (VAS)

This is a more sensitive scale. On a 10 cm line the observer will put a cross where he/she thinks the level of pain is. On the left no pain is observed while on the right is the worse pain ever. To assess the level of pain, we measure the distance between the left side and the cross from the observer. The longer the distance, the worse the pain is.

VAS

Composite Pain Scale

As all these scoring systems are not very precise, some groups like the one from Glasgow in the UK (see below) have worked on composite scale. These scales are often a group of numerical rating scales. Each of them focusing on a specific aspect of pain.

Glasgow Composite Pain Scale

References

Greene, Stephen A: Veterinary Anesthesia and Pain Management Secrets, Philadelphia, Hanley & Belfus, Inc., 2002

Tranquilli W, Thurmon J, Grimm K: Lumb, Jones', Veterinary Anesthesia and Analgesia 4th ed. Iowa, Blackwell Publish, 2007

Tranquilli W, Grimm K, Lamont, L: Pain Management for the Small Animal Practitioner, Jackson, WY, Teton Media, 2000