Pre-operative assessment

NB Many trusts will have a preassessment form which will guide you through the assessment and cover all the questions needed to be asked

• WIPE 
  • wash hands, introduce self, check patient details and explain
    • NB When checking patient details, you should also check what operation they are to have (and what kind of anaesthesia) and when this is going to be
• History
  • Ask about present health:
    • Presenting complaint and history
    • General systems history (CVS; Resp; GI; GU; Endo/Diabetes; Neuro)
    • Any recent or current illness
    • Current exercise tolerance
    • Any smoking? Any alcohol? Who is with them at home?
    • Any sleep apnoea?
  • Ask about PMHx and Rx
    • In particular any diabetes, epilepsy, any CVD, asthma/COPD, hypertension (and how well each is controlled)
    • What medication is the patient taking?
      • Some medications may require advice re: stopping before surgery (and when to restart)
      • Make sure to ask about aspirin, clopidogrel, rivaroxiban (and other NOACs), warfarin… in particular
    • ANY ALLERGIES?
    • Previous surgical history
  • Anaesthetic Hx
    • Previous general anaesthetics; reactions/complications
      • If the patient has not had any GAs, ask about family history of reactions/complications
    • Dental prosthesis
  • Social
    • Smoking and Drinking
    • Exercise tolerance
    • Support (independent/family/care etc)
  • Family Hx
  • Full systemic review (cardiorespiratory; gastrointestinal; neurological; musculoskeletal; urological/gynaecological etc)
• Examination
  • Anaesthetic assessment
    • Examine neck movement and any limitation in ROM
    • Examine how wide the patient can open their jaw and grade this (Mallampati grading)
      1. See all of soft palate and uvula
      2. See half of uvula
      3. See a small gap at end of soft palate
      4. Only see hard palate
  • Multi-system assessment (Head to toe)
    • Examine Cardiorespiratory system fully; abdomen; calves +/- any systems involved in the surgery

NICE recommends various investigations based on the severity of the surgery (minor; intermediate; major and major +; as well as cardiovascular surgery and neurosurgery) as well as patient baseline function and comorbidities (ASA graded depending on severity of co-morbidity).

In general, an investigation is only required to confirm a diagnosis or exclude a differential; assess the appropriateness of the surgical intervention; assess fitness for surgery.  In short- will the investigation alter the surgical management of the patient.  Investigations may include (if they have not been requested a week prior to surgery)

• CXR
• ECG
• Bloods (FBC; U&Es; clotting +/- others e.g. LFTs; glucose; amylase)
• Urinalysis
• Blood gases
• Lung function tests

Other things to consider pre-operatively

• VTE Prophylaxis
• Drugs
  • In particular, diabetes drugs e.g. oral antihyperglycaemics (see also Diabetes and Surgery)
  • When to stop antiplatelets and anticoagulants
  • Antihypertensives (diuretics and ACEIs usually withheld on the day of surgery)
• Fasting information
• Consent

Evaluating Cardiac Murmurs

Once you have identified which murmur…

• A murmur is (technically) NOT a diagnosis but a sign.  Therefore you should ask WHY is there a murmur.  This may involve further investigation e.g.
  • Echocardiogram – will often further evaluate the severity and impact of a murmur but may not provide a cause.
  • Imaging- e.g. CTPA (particularly if SOB and pulmonary regurgitation- to rule out PE as cause)
  • ECG- may show signs of past infarction which may explain a murmur
• Management of murmurs really depends on the underlying cause and whether it is reversible.  It also depends on the impact of the murmur on cardiac function.  A large number are managed conservatively (particularly idiopathic aortic stenosis), although it is a good idea to manage any underlying risk factors for cardiac disease e.g. cholesterol, blood pressure, weight, etc.

Pain Control

Assessment of pain

• You should try and always review the patient before prescribing analgesia
  • Ideally take a focused history and examination of the pain to try and discover the underlying cause (may not always be the obvious cause)
    • Treat the cause where possible
  • Review also what the patient has been taking prior to review (see below)

In an ideal world you would do this for every patient.

• Other factors to review/consider prior to prescribing analgesia include:
  • Is the patient allergic to anything OR had any reactions/contraindications to analgesic drugs (IMPORTANT)
    • Particularly considering NSAIDs (and GI bleeds/renal failure)
    • Others include liver failure (a reduced dose of opiate analgesia may be advised)
  • What is the weight/size/reserve of the patient?
    • Whilst this is not a reason not to give strong analgesia, be weary that old, frail, small patients may be more susceptible to opiates and their side effects
  • What is the best way to give pain relief?
    • Analgesia can be given locally as well as systemically and, for some pain (e.g. bone pain), this may be more appropriate.  Similarly, patient controlled analgesia will not be appropriate for some patients (e.g. confused)

The Pain/Analgesic Ladder

1. Step 1- Paracetamol (up to 1g QDS) – for mild to moderate pain
2. Step 2- Substitute paracetamol with low-dose ibuprofen (400mg TDS)
   1. If necessary increase the dose to a maximum of 2400mg daily (i.e. 800mg TDS)
   2. Alternatively, if the patient is unable to take an NSAID, use a full-dose of weak opioid- Codeine (60mg every 4-6 hours max 240mg daily)
3. Step 3- Add paracetamol back in with ibuprofen/codeine
4. Step 4- Continue paracetamol and switch ibuprofen to a strong/alternative NSAID e.g. naproxen (250-500mg BD)
5. Step 5- Start full dose of weak opioid (Codeine) + paracetamol + NSAID
6. Step 6- Stop the weak opioid and consider starting an intermediate strength opioid e.g. Tramadol (50-100mg 4-6 hourly, max 400mg in 24 hours)
   1. NB Dihydrocodeine is rarely used in the management of acute pain (limited mainly to use in obstetrics) but is an alternative to codeine.
   2. Note also that tramadol is now a controlled drug like strong opiates- it can be useful for management of worsening pain in the short term but is less commonly used longer term or pain expecting to worsen more (due to its relatively low ceiling of care)
   3. In practice, this step is commonly skipped due to the limited use of the drugs in this category.
7. Step 7- Consider PRN strong opioid e.g. oramorph or morphine sulphate
8. Step 7- Stop the intermediate/weak opioid and start 4-hourly oral morphine (either tablet or solution)
   1. A dose of 5mg every four hours is a reasonable starting dose for an opiate naive individual (2mg in elderly/frail patients)
      1. NB  For patients who have been on weak opioids- they may require a higher dose.  Calculate the equivalent dose of morphine and adjust as appropriate:
         1. Tramadol – oral morphine : divide by 5 (e.g. if taking maximum dose of tramadol (400mg)- equivalent to 80mg of oral morphine in 24 hours (or 13.3mg/4 hours))
         2. Codeine – oral morphine : divide by 10 (i.e. max daily dose is 24mg morphine; 4mg/4 hours)
   2. Note also to prescribe breakthrough PRN doses (equal strength initially; up to 2 hourly)
   3. Once 24 hours has passed, calculate total 24 hour dose (regular + breakthrough) NB exclude incident analgesia (i.e. pain relief for moving/washing/dressing etc)
      1. Adjust regular oral dose to this (e.g. if total 24 hour dose was 90mg; the new regular dose would be 15mg)
         1. Keep PRN breakthrough as required (usually continued as one tenth of the daily dose e.g. 10mg in this case) and continue to calculate and adjust every 2-3 days until the analgesia is sufficient (not taking more than 2 breakthroughs a day)
         2. At this point- you may change the preparation to longer acting morphine (OD/BD doses)
            1. Divide total daily dose by 2 (for 12-hourly preparations; if 24 hour preparation, keep the same dose)
         3. Keep breakthrough PRN as a sixth of the daily dose.
   4. If the patient requires increasing pain relief- it is recommended to increase the long acting morphine dose by 30% (maximum) at a time to avoid toxicity.
      1. Alternatively, you can switch to another strong opioid
         1. Usually done under specialist advice.  Make sure to calculate the correct dosages based on conversion tables.
      2. Be aware of unwanted side effects: drowsiness, hallucinations, drop in conscious level, confusion, nausea/vomiting 

When prescribing pain relief…

• Consider side effect profiles e.g.
  • NSAIDs and gastritis- consider prescribing a PPI (especially if PMHx of GORD/ulcer/reaction to NSAID)
  • Codeine, morphine and constipation- good practice to prescribe ‘symptomatic relief’ i.e. usually senna and lactulose
  • Morphine and nausea- some patients suffer from bad nausea with strong opiates.  Good practice to co-prescribe an antiemetic e.g. metoclopramide (10mg) PRN or regular (haloperidol is also recommended); at least for the first few days and reassess
• Also consider other ways of settling pain/agitation which can be either pharmacological or not e.g. heat pressure/bottles; antispasmodics (rarely can also use benzodiazepines to aid relief); even changing position in bed may help.

Basic Principles of Neuroanaesthesia

Goals of neuroanaesthesia

• On top of the triad of anaesthesia (hypnosis; paralysis; and analgesia); there are other goals, some particular to neurosurgery, some important to anaesthesia in general
  1. Haemodynamic stability- adequate cerebral perfusion pressures must be maintained, or there is risk of cerebral ischaemia.  Conversely, hypertension should be avoided as it increases the risk of cerebral oedema or worse, haemorrhage.
     • Many anaesthetic agents, particularly inhaled agents, reduce the cardiac output by causing myocardial depression (decreased rate) and by decreasing systemic vascular resistance.
  2. Maintaining cerebral perfusion
  3. Keep Intracranial pressure down (avoid a ‘full’ skull)
     • Hyperventilation can be used to decrease ICP (causes vasoconstriction- note can lead to hypoperfusion if done inappropriately i.e. should only be used in short bursts for patients with significantly raised ICP unresponsive to mannitol)
     • Intra-operative mannitol
       • An osmotic diuretic, it draws water out of the tissue into the vasculature.  High dose is recommended (2g/kg over ~30 mins) provided the patient is not hypovolaemic or hyperosmolar.
     • Positioning with the head up has been shown to significantly decrease ICP without affecting CPP.
     • The use of dexamethasone prior to surgery is often used to reduce cerebral oedema.  However, be aware that it can increase blood sugars, which can have significant implications for patients in neurocritical care.
  4. Protect the cerebral tissue where possible
     • Some advocate the use of ketamine, propofol and volatile agents for their neuroprotective effects (i.e. preventing cell death)- however, the evidence for this in patients suggest these effects are short lived)
  5. Ensure rapid recovery
     • Managing analgesia with suitable opioid (e.g. remifentanyl) as well as using quick onset/offset volatile agents e.g. sevoflurane, is important for rapid recovery and assessment of function

Drugs

• Note that the choice of anaesthetic agents used in neurosurgery is controversial, as all have theoretical disadvantages.  The choice of drug is less likely to affect outcome than measures highlighted above.  Raised ICP prior to surgery, degree of midline shift and diagnosis (malignant tumour) are all more likely to cause intraoperative swelling.
• Inhaled agents
  • These have the potential to increase ICP due to vasodilation.  However, in practice, if given appropriately (low concentrations) and there is no rise in ICP prior to surgery, the effect is minimal.
  • Sevoflurane seems to be superior for its comparative effect on CBF and ICP, causing the least vasodilation and least effect on the autoregulation of blood flow
• Intravenous agents
  • Propofol is often used in combination with an inhaled agent.  It appears to have a theoretical effect of reducing ICP and increased CPP when compared with sevoflurane alone.
  • Some operations require evoked potential monitoring which can be affected by volatile agents.  In these operations, total IV anaesthesia (TIVA) may be advised