Thursday

POST-OPERATIVE CARE

LEARNING OBJECTIVES

• To outline the general post-operative course for patients
• To outline the potential post-operative complications that may occur
• To demonstrate an understanding on the basic principles of post-operative analgesia
• To outline the key drugs used in analgesia and to explain the basic pharmacology of these drugs
• To explain the physiology of post-operative nausea and vomiting
• To outline the management of post-operative nausea and vomiting

A co-ordinated team, concentrating on the fundamentals of good patient care and encouraging a simple and consistent approach, best supports effective post-operative recovery.

Analgesia

A tailored, multimodal apporach using the analgesic laddder is ideal for most patients. Remember to include ‘as required’/PRN analgesia on the drug chart or breakthrough pain.

Pain: An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.

Analgesic site of action:

• They may act at the site of injury and decrease pain associated with an inflammatory reaction (e.g. non-steroidal anti-inflammatory drugs)
• They may alter nerve conduction (e.g. local anaesthetics)
• They may modify transmission in the dorsal horn (e.g. opioids and some antidepressants)
• They may affect the central component and the emotional aspects of pain (e.g. opioids and antidepressants)

Benefits of treating acute pain

Reduces:

• sympathetic activity
• incidence of acute coronary syndromes
• risk of tachycardia and dysrhythmias
• respiratory complications
• thromboembolic events
• chronic pain syndrome

Improves

• patient satisfaction
• wound healing, mobilizaiton
• earlier hospital discharge

Analgesia ladder

The ‘analgesia ladder’ is a tool used to systematically increase (or decrease) the amount of analgesic given to a patient. Initially devised for cancer pain, this method has been widely adapted for managing perioperative pain on the wards. Immediately after surgery, patients will need strong analgesia with the aim of ‘stepping down the ladder’ as the postoperative days progress.

The three broad categories of analgesics are:

1. Simple analgesics (e.g. paracetamol and diclofenac)
2. Weak opioids (e.g. codeine and tramadol)
3. Strong opioids (e.g. morphine and oxycodone)

There are other analgesic modalities, which include reassurance and explanation, nitrous oxide, ketamine, gabapentinoids and local anaesthetics (wound infiltration, nerve blockage, spinal or epidural).

NSAIDS

The non-steroidal anti-inflammatory drugs (NSAIDS) represent a widely used group of drugs, e.g. aspirin, paracetamol, ibuprofen, and diclofenac. Paracetamol is included but has very weak anti-inflammatory effects. These drugs are mainly used to treat mild to moderate pain associated with the inflammatory process. It is believed that the analgesic/antipyretic/anti-inflammatory effects of NSAIDS are largely dur to inhibition of cyclo-oxygenase (COX), and the resulting inhibition of the synthesis of prostaglandins, which are pro-inflammatory.

Many NSAIDS are not selective for the COX enzyme types and it is the inhibition of COX-1 that underlies the majority of unwanted effects of NSAIDS, such as gastrointestinal irritation and bleeding, and nephrotoxicity.

Opioids

Opioids bind to G-protein coupled receptors. These receptors have been subdivided into three main categories: Mu, Delta and Kappa receptors. Opioids act as agonists at opioid receptors, and generally have limited selectivity for a given receptor type.

The activation of the opioid receptors is associated with inhibition at the cellular level reducing neuronal excitability by inhibiting neurotransmitter release. Most of the opioid drugs presently used (in particular morphine) are agonists with significant affinity at Mu receptors. If used appropriately, the relief of pain can be significant, but is often accompanied by unwanted effects, some of which may become life-threatening, such as the significant respiratory depression seen at high doses of morphine. Naloxone is used in the management of opioid overdose to rectify respiratory depression.

Tolerance to a drug is the necessity to increase the dose in order to achieve the same effect. It may develop during chronic administration of drugs. Tolerance to opioids can develop rapidly. Physical and psychological dependence can also develop. Physical dependence is associated with withdrawal syndrome when the administration of the drug is stopped abruptly. Psychological dependence leads to craving for the drug.

Side effects of opiates:

• Constipation – give regular laxatives
• Confusion – especially in the elderly, but check for other causes first, e.g. hypoxia, infection, etc.
• Nausea – give antiemetic
• Respiratory depression – classified as less than 8 breaths per minute. In an emergency, give naloxone.

Patient Controlled Analgesia (PCA)

A PCA is an effective way of providing analgesia whereby the patient titrates the amount of opiate to meet his or her needs by pressing a button that delivers a small bolus (e.g. 1mg morphine/10mcg fentanyl/1mg oxycodone) via a syringe driver. It is safe, has a high patient satisfaction and is set up by the anaesthetist in theatre. For safety, a separate IV line is required with a non-return valve and crystalloid infusion to the line patent.

Epidurals

An epidural infusion of local anaesthetic (often with fentanyl) provides site-specific pain relief and also reduces the risk of venous thrombosis. An epidural is sited by the anaesthetist immediately before induction of anaesthesia and left in for a maximum of three days. Coagulation must be normal before insertion and removal, to prevent an epidural haematoma. Insertion/Removal of epidural catheter must also be timed appropriately to any anticoagulation including DVT prophylaxis (See https://anaesthetists.org/Portals/0/PDFs/Guidelines%20PDFs/Guideline_regional_anaesthesia_patients_abnormalities_coagulation_2013_final.pdf?ver=2018-07-11-163756-520&ver=2018-07-11-163756-520 ). The acute pain team usually manages the infusion. Before removal, alternative analgesia needs to be started.

Recovery discharge

The patient must

• Be fully conscious – responding to voice or light touch
• Be able to maintain a clear airway and have a normal cough reflex
• Have a satisfactory respiration rate and oxygen saturations
• Be cardiovascularly stable with a normal (or back to pre-operative) pulse and blood pressure
• Have pain and emesis adequately controlled, with suitable analgesic and anti-emetic regimens charted
• Have oxygen and fluid therapy appropriately prescribed where required

Levels of care

• Level 1 – Ward (minimum one trained nurse)
• Level 2 – HDU (usually one nurse to two patients)
• Level 3 – ICU (one-to-one care)

Post-operative confusion

Common causes:

• Hypoxaemia
• Hypercarbia
• Sepsis (e.g. infection of chest, urinary tract, wound, IV cannula site, or intra-abdominal collection)
• Sedative drugs
• Hypoglycaemia
• Biochemical abnormality (e.g. urea, sodium, potassium, calcium)
• Acute neurological event
• Myocardial infarction
• Urinary retention
• Alcohol/drug withdrawal
• Hepatic encephalopathy

Stress response

The stress response to surgery is the neuroendocrine, metabolic and inflammatory response to tissue injury. It is probably a protective mechanism that evolved to aid survival in a more primitive environment. It results in substrate mobilisation, muscle protein loss, and sodium and water retention. There is also activation of the sympathetic nervous system, immunological and haematological changes. The benefits of the stress response are not obvious in modern medicine and may even be detrimental, given that we cannot correct some of the physiological changes that occur.

Anaesthesia can influence some aspects of the stress response, by the use of regional anaesthesia or high dose opioids; surgical technique, nutrition and steroid therapy may also play a role.

Enhanced recovery

Traditional practices such as prolonged pre-operative fasting (“NBM from midnight”), bowel preparation and the use of post-operative nasogastric decompression are fast becoming outmoded. The newer regimens are being formulated into protocols called Enhanced Recovery after Surgery (ERAS) pathways, which aim to expedite recovery after surgery. To achieve maximum benefit, ideally the changes have to be implemented together; a summary of the typical recommendations is given below:

Pre-operative

• Counselling and training
• A curtailed fast, with pre-operative carbohydrate loading
• Avoidance of bowel preparation
• Deep vein thrombosis prophyalxis
• A single dose of prophylactic antibiotics

Intra-operative:

• Prevention of hypothermia
• “Goal-directed” intra-operative fluid therapy
• Preferable use of short and transverse surgical incisions
• Avoidance of post-operative drains and nasogastric tubes
• Short duration of epidural and regional analgesia

Post-operative:

• Avoidance of opiates
• Early commencement of post-operative diet
• Early and structured post-operative mobilisation
• Restricted amounts of intravenous fluid
• Regular audit