Anaesthetics and Peri-op Care Flashcards
Describe the American society of anaesiologists classification for surgery
- ASA I – normal health patients – non-smoking and no or minimal alcohol use
- ASA II – mild systemic disease – current smoker, social alcohol drinker, pregnancy, obesity (30-40), well controlled diabetes/hypertension and mild lung disease
- ASA III – severe systemic disease – poorly controlled diabetes/hypertension, COPD, morbid obesity (>40), hepatitis, alcohol dependence or abuse, pacemaker, , MI within last 3 months, CVA, ESRD undergoing dialysis and moderate reduction in ejection fraction.
- ASA IV – severe systemic disease that is constant threat to life – MI in last 3 months, CVA, severe valve dysfunction, severe reduction in ejection fraction, sepsis, DIC, ARD, and ESRD not undergoing dialysis.
- ASA V – moribund patient who is not expected to survive without the operation – ruptured AAA, massive trauma, intracranial bleed, ischaemic bowel with significant cardiac pathology or multiple organ/systemic dysfunction
- ASA VI – declared brain dead patient where organs are being removed for donor purposes
What pre medications might you consider for a nervous or young patient prior to surgery?
In particularly nervous patients or young patients a benzodiazepine is sometimes used to help calm their nerves around 2 hours prior to commencing surgery.
Why might ranitidine or an PPI be given to patients prior to surgery?
In those at high risk of aspiration antacids may be necessary such as a PPI or ranitidine.
What common side effect from epidurals can also be a sign of something much more dangerous?
Heavy leg feeling is a relatively normal side effect, but you must be very careful
This is also a sign of epidural abscess or haematoma which compresses the spinal cord and causes ischaemia. If heavy legs do not go away upon stopping the epidural, then must call anaesthetist.
What are the two main contraindications to epidurals?
Note epidurals and spinal blocks are contraindicated by use of anticoagulants and local infections.
What is propofol and what are its adverse effects?
Propofol – GABA receptor agonist causing rapid onset anaesthesia. Rapidly metabolised with proven anti-emetic properties. Moderate myocardial depression and widely used for maintaining sedation on ITU total IV anaesthesia and day case surgery.
What is sodium thiopentone and what are its adverse effects?
Sodium thiopentone – GABA agonist with extremely rapid onset so used for rapid sequence induction, marked myocardial depression, metabolites build up quickly, unsuitable for maintenance infusion and little analgesic effect. Can cause laryngospasm.
What is ketamine and what are its adverse effects?
Ketamine – NMDA receptor antagonist and can be used for induction of anaesthesia. Has moderate-strong analgesic properties and produces little myocardial depression so is suitable for those who are haemodynamically unstable. Can induce dissociative anaesthesia resulting in nightmares.
What is etomidate and what are its adverse effects?
Etomidate – GABA agonist with favourable cardiac safety profile but no analgesic properties, unsuitable for maintaining sedation as use may result in adrenal suppression. Post-operative vomiting Is common.
What is halothane and what are its adverse effects?
Halothane – inhaled – GABA and Glycine agonist. Adverse effects include hepatotoxicity, myocardial depression and malignant hyperthermia
What is Suxamethonium and what are its adverse effects?
Suxamethonium – depolarising neuromuscular blocker that inhibits action of acetylcholine at neuromuscular junction. Degrades by plasma cholinesterase and acetylcholinesterase. Fastest onset and shortest duration of all muscle relaxants. Causing one generalised muscular contraction prior to paralysis. Adverse effects include hyperkalaemia, malignant hypertension, and lack of acetylcholinesterase.
Name some non depolarising neuromuscular blockers and their side effects
Atracurium – non depolarising neuromuscular blocker, duration of action is 30-45 minutes, not excreted by kidney or liver but by tissues and can be reversed via neostigmine.
Vecuronium – non depolarising neuromuscular blocker, duration of action is 30-40 minutes, degrades by liver and kidney and effects prolonged in organ dysfunction. Can be reversed by neostigmine
Pancuronium – non depolarising neuromuscular blocker, onset of action in 2-3 minutes and duration of 2 hours, effects partially reversed with neostigmine.
What is a depolarising vs non depolarising muscle relaxants
Depolarising – binds to nicotinic acetylcholine receptors resulting in persistent depolarisation of the motor end plate. Cannot be reversed.
Non depolarising – competitive antagonist of nicotinic acetylcholine receptors. Can be reversed and cause hypotension.
What is malignant hyperthermia?
Occurs after administration of anaesthetic agents that result in hyperpyrexia and muscle rigidity. Occurs due to excessive release of Ca from sarcoplasmic reticulum of skeletal muscles. Susceptibility is inherited in autosomal dominant pattern.
What are the common causative agents of malignant hyperthermia?
Halothane
Suxamethonium
Antipsychotics causing neuroleptic malignant syndrome has a similar aeitiology
What are the clinical features of malignant hyperthermia?
Muscle rigidity
Hyperpyrexia
Raised creatinine kinase
How should you investigate for malignant hyperthermia?
Contracture test with halothane and caffeine - muscle biopsy
How is malignant hyperthermia managed?
Dantrolene – prevents Ca release from sarcoplasmic reticulum
What is the ERAS protocol?
This was designed to help patients recover more quickly from surgery
Pre-operative
• Patient education regrding their surgery and what to expect
• Ensuring good health prior to surgery
• Optimal pre-operative fasting guidelines
Intra-operative
• Using multimodal and opioid sparing analgesia
• Multimodal postoperative nausea and vomiting prophylaxis
• Minimally invasive surgery
• Goal directed fluid regime
Post-operative
• Ensure adequate pain control and early ambulation
• Early oral intake
• Multi-disciplinary patient follow up including in the post-acute phase
What should be done in the pre admission clinical appointment prior to surgery?
Pre admission clinic appointment to address medical issues
• History – PMHx, DHx and SHx (including anaesthetics history) most important, also neck and jaw mobility for intubation
• Examination – cardio respiratory (inlcuding airway classification), neck and jaw
• Baseline blood tests – FBC, U&Es, LFTs, Clotting screen and group and save
• Urine analysis
• Pregnancy test
• MRSA swab – all patients (nasal and skin lesions or wounds)
• ECG/Chest X-ray
What are the rules regarding food and liquid prior to surgery?
• Stop eating – 6 hours before
• Stop dairy products (including tea and coffee) – 6 hours before
• Stop clear fluids – 2 hours before
If aspiration were to occur this can lead to aspiration pneumonitis (due to the gastric acid) or pneumonia.
What drugs need to be modified prior to surgery?
Drugs to stop can be remembered using the phrase CHOW
- Clopidogrel – 7 days before (aspirin usually continued unless large bleeding risk)
- Hypoglycaemic medication (see below)
- Oral contraceptive pill or HRT – 4 weeks before, restart 2 weeks after
- Warfarin and DOACs– stopped 5 days prior and commenced on enoxaparin. INR must be less than 1.5 for surgery to go ahead otherwise reverse with vitamin K
- Anticonvulsants – give as normal pre-op then IV or NG until able to take orally again
- Beta-blockers and Digoxin – continue as normal
- Thyroid medication – must be euthyroid prior to surgery
- Omit all ACEi., ATBs and NSAIDs but continue other hypertension medications
- Lithium – omit
Never stop dual antiplatelet/anticoagulation therapy without specialist advice.
What should be done with steroids prior to surgery?
Steroids must be continued as if stopped this could lead to Addisonian crisis, may even require extra doses
Are there any drugs that need starting prior to surgery?
Enoxaparin and TED stockings (unless vascular patient)
Antibiotic prophylaxis for any surgery involving orthopaedic, vascular or GI.
How should a type 1 diabetic be managed prior to surgery?
Should be on the morning list
Night before surgery give all normal insulin and continue giving 80% of basal insulin including morning of the surgery
Morning of surgery withhold bolus short acting insulin (unless on PM list) and start on sliding scale insulin infusion
While nil by mouth give 125ml/hour of 5% dextrose and check BM every 2 hours.
Continue this until they can eat again and then give their SC insulin just before a meal and stop their IV insulin just after their meal.
How should type 2 diabetes be managed prior to surgery?
If controlled with diet, then no action required
If on oral medications then stop metformin on the morning of the surgery and stop oral hypoglycaemic drugs 24 hours before the op. Patient commenced on IV insulin pump for surgery and given IV 5% dextrose and post operatively managed same as type 1.
When is bowel prep required prior to surgery?
Bowl prep should only be given if surgery involves left colon, sigmoid or rectum/anus. They should be given a phosphate enema the morning of the op.
Who are the high risk VTE groups in surgery?
High risk VTE surgical groups
• Hip/knee replacement
• Hip fracture
• General anaesthetic and surgical duration> 90mins
• Surgery of the pelvis or lower limb with general anaesthesia and surgical duration > 60mins
• Acute surgical admission with inflammatory or intra-abdominal condition
• Surgery with significant reduction in mobility
What are the risk factors for VTE intra- or post surgery?
- Active cancer/chemotherapy
- Aged > 60
- Known blood clotting disorder
- BMI > 35
- Dehydration
- One or more significant medical comorbidities such as heart, metabolic, endocrine, respiratory, infections and inflammatory conditions
- Critical care admission
- Use of hormone replacement or COCP
- Varicose veins
- Pregnant or less than 6 weeks post-partum
How can VTE prophylaxis be administered mechanically?
Mechanical
- Correctly fitted anti-embolism stockings 9 thigh or knee height (CI in peripheral vascular disease)
- Intermittent pneumatic compressions device
- Mobilising as soon as possible
How can VTE be administered pharmacologically?
Pharmacological
- Fondaparinux SC injection
- LMWH – enoxaparin (reduce doses in severe renal impairment)
- Unfractionated heparin – used in chronic kidney disease
All surgical patients should at least have anti-embolism stockings
High risk patients require pharmacological methods in conjunction
How are elective hip, knee and fragility fractures of the pelvis managed in regard to VTE prophylaxis?
- Elective Hip – LMW heparin for 10 days followed by aspirin for 1 month OR LMWH for 1 month combined with anti-embolism stockings until discharge OR Rivaroxaban.
- Elective knee – Aspirin for 14days OR LMWH for 14 days with anti-embolism stockings until discharge OR rivaroxaban
- Fragility fractures of the pelvis – LMWH for a month after surgery OR fondaparinux starting 6 hours after surgery
Why is perioperative thermoregulation required?
Patients at particular risk of hypothermia due to large areas of body and internal body exposed, anaesthesia prevents normal physiological reactions to cold and anaesthetic drugs directly.