Pre-op

Question 1

Discuss consenting a patient for surgery

Answer 1

Question 2

Define the term ‘material risk’.

Answer 2

A risk is material if a ‘reasonable’ person (in same position) if warned of the risk is likely to attach significance to it, or if the medical practitioner is, or should reasonably be, aware that the particular patient, if warned of the risk, would be likely to attach significance to it

• Therefore, a known risk should always be disclosed to the patient when:
  
  • an adverse outcome is common, even if the detriment is minimal
  • an outcome is severe, even if its incidence is rare

Question 3

List the mechanisms to ensure surgery is performed on the correct anatomical site

Answer 3

Sign in (before induction of anaesthesia) → pt has confirmed site and site is marked

Time out (before incision) → surgeon, anaesthesia professional and nurse verbally confirm site

Question 4

What are specific perioperative risks for diabetic patients?

Answer 4

Hypoglycaemia, hyperglycaemia, ketoacidosis

Increased susceptibility infection, poor wound healing

Increased susceptibility to skin pressure necrosis and pressure sores

Underlying diabetes related comorbidties are often unrecognised e.g., mild renal impairment, coronary and cerebrovascular disease, mild autonomic neuropathy with associated reduced homeostatic responses

Question 5

General management of diabetic management pre-operatively

Answer 5

1. Inform anaesthetist, endocrinologist and relevant specialists
2. Optimise glycaemic profile before procedure if possible
3. Is pt: oral controlled? insulin controlled? brittle insulin controlled? (increasing risk)
4. Pre-op Ix to check for comorbidities (ECG, ACR)
5. 1st on operating list so timings can be as predictable as possible for blood sugar control
6. If HbA1c is > 9% delay non-urgent elective procedures until glycemic profile is optimised

Question 6

Specific peri-operative Mx of T1DM pt

Answer 6

INSULIN Mx

Minor procedures: continue basal insulin before and during procedure
- withholding basal insulin even when fasting –> DKA
Long/complex: IV insulin infusion + IV glucose infusion
Omit mealtime rapid- or short-acting bolus insulin while fasting.

MONITORING

• Frequent blood glucose concentration monitoring after procedure
• Blood ketone concentration if medically unstable or prolonged fasting (hourly from waking from time of 1st missed meal)

CORRECTIONS

If hyperglycaemic consider rapid insulin bolus and recheck
If hypoglycaemic take glucose gel or tablets or, if able to take fluid, a glass of clear apple juice or cordial

POST-OP

Patients should not be discharged until:
- able to tolerate food and oral fluids
- be well enough to self-manage insulin
- have immediate access to a fast-acting glucose source
- have an emergency number to ring for advice about glycaemic management over the next 24 to 48 hours

If pt is not eating normally:
- hourly blood glucose conc
- basal insulin
- unstable: IV insulin infusion

Question 7

Specific peri-operative Mx of T2DM pt

Answer 7

METFORMIN
Pt w/ T2DM and CKD stage 3+: stop metformin the day before surgery or procedure using radiocontrast

SGLT2 INHIBITORS
Increased risk of DKA (+ even higher risk with fasting)
Stop pre-operatively
- At least 3 days (2 days before and day of): procedures requiring bowel prep or involving an overnight stay
- Day of: day procedures

OTHER ANTIHYPERGLYCAEMIC DRUGS
Stop on day of procedure

POSTPROCEDURE

Extensive surgery: noninsulin antihyperglycaemic drugs should always be temporarily replaced with insulin treatment (easier to tailor to achieve glycaemic targets)

Minor surgery: antihyperglycaemic drugs (except metformin or SGLT2 inhibitors) can usually be restarted when oral intake resumes

Metformin: if at risk of periprocedural kidney dysfunction, metformin should not be restarted until kidney function returns to baseline and the patient is eating and drinking normally

SGLT2 inhibitors: withhold to reduce risk of DKA and do not restart until eating and drinking normally, kidney function has returned to baseline, and the patient is close to discharge
- usually 3 to 5 days after a procedure
- unwell in week following procedure: check blood ketone concentration, even if blood glucose concentrations are not elevated and SGLT2 inhibitor was withheld periprocedurally

Question 8

Pre-operative assessment of pt with respiratory disease

Answer 8

Pts current respiratory status should be compared with their ‘normal state’.

Gather info in Hx: regular Tx, PEFR records, steroid use, home oxygen and CPAP ventilation

Ex: check for evidence of RH failure

Pulmonary function tests will indicate type and severity of disease and response to Tx

Refer pt to respiratory physicians if:
- Severe disease or significant deterioration from usual condition
- Major surgery is planned in a pt with significant respiratory comorbidities
- RH failure is present: dyspnoea, fatigue, tricuspid regurgitation, hepatomegaly and oedema of feet
- Pt is young with COPD (indicates a rare and life-threatening condition)

Question 9

General pre-operative Mx of pt with respiratory disease

Answer 9

1. Encourage pts to be compliant with medications, exercise, balanced diet, and stop smoking
2. Give regular medications with additional bronchodilator dose just prior to surgery (esp. if reversible obstructive airway disease)→ reduces chances of untoward events
   - +/- starting or increasing steroids
3. Pts taking > 10 mg prednisolone undergoing high-risk surgery will need peri-operative steroid supplements
4. Consider regional anaesthetic techniques and less invasive surgical options in severe cases
5. Elective surgery should be postponed until acute exacerbations are treated or to allow for medical optimisation
6. Smoking information should be provided to indicate perioperative risks → stopping smoking reduces carbonmonoxide levels and pt is better able to clear sputum
7. Optimise nutritional status

Question 10

Additional specific peri-operative considerations for patient with asthma

Answer 10

Establish severity, precipitating causes, frequency of bronchodilator and steroid use, PEFR and any previous ICU admissions

Pts should continue to use regular inhalers until start of anaesthesia

Brittle asthmatics may also need extra steroid cover

Question 11

Additional specific peri-operative considerations for patient with COPD

Answer 11

Pre-op CXR or scans useful in pts with known emphysematous bullae, pulmonary ca, metastasis or effusions

ABG analysis may be useful for indication of carbon dioxide retention → increased risk of perioperative respiratory complications

Optimisation of condition by respiratory physician in pts with significant COPD undergoing major surgery

Question 12

What should be done if pt booked for surgery has resp. infection

Answer 12

Postpone elective surgery if pt has chest infection → Tx with ABx and physiotherapy → reschedule after 4–6 weeks

Question 13

Post-operative Mx of pt with respiratory disease

Answer 13

• Consider physiotherapy for postural drainage
• Consider deep breathing exercises or incentive spirometry for pts at increased risk of respiratory complications
• Delay extubation until analgesia, hydration and acid–base status have been corrected → avoidance of hypoxaemia and CO2 retention leading to reintubation
• Supplemental oxygen may allow certain patients to be extubated earlier
• Possible ICU admission

Question 14

Surgical complications for pt with respiratory disease

Answer 14

Surgery (esp. open abdominal procedures unde GA) result in changes to respiratory physiology

• functional residual capacity of the lungs is reduced
• anaesthetic agents have espiratory depressant effects
• pt’s mobility is limited
• pain from surgery increases risk of atelectasis (failure of gas exchange due to alveolar collapse) and predisposes to postoperative respiratory infection (why does pain causes this?)
• other complications → bronchospasm, pneumothorax and ARDs

→ significant morbidity and increased length of hospital stay

→ respiratory failure (PaO2 <8 kPa in air, PaO2/FiO2 <40 kPa or inability to extubate pt 48hrs after surgery) = most significant complication → mortality of ~30-40%

COPD: Severe disease: pts on steroids or O2 therapy with FEV1 < 30% of predicted value (for age, weight and height) → increased risk of respiratory failure in postoperative period

Question 15

Intra-operative Mx for pt with respiratory disease

Answer 15

Intra-Operative Management: regional anaesthesia where possible (GA → more respiratory complications)

Question 16

What is surgical fitness

Answer 16

Pts who can climb a flight of stairs without SOB, chest pain, or stopping → lower risk of perioperative morbidity and mortality of CV origin than those who can’t

Question 17

Pre-operative assessment for pts with CVD

Answer 17

Important to ID pts with high perioperative risk of MI and make appropriate arrangements to reduce risk

• Increased risk: pts with CAD, CCF, arrhythmias, severe PVD, cerebrovascular disease or renal failure esp. if undergoing intra-abdominal or intrathoracic surgery
• Stress test to evaluate LV status of IHD pts (high NPV and low PPV i.e., negative test → test is pt unlikely to have IHD; positive test → chances of pt actually having IHD is not high)
• Echo for pts with symptomatic valvular heart disease or poor LV function
  
  • determine pressure gradients across valves, dimensions of, chambers and contractility
  • EF < 30% → poor patient outcomes.
• Cardiopulmonary exercise testing = non-invasive assessment of combined pulmonary, cardiac and circulatory function if performed
• Cardiology referral → symptomatic pt with audible murmur, pt known to have poor LV Fx or cardiomegaly, ischaemic changes seen on ECG (even if pt not symptomatic; silent MI), abnormal ECG rhythm, tachy/bradycardia or a heart block that may lead to CV compromise

Question 18

Peri-operative Mx of pts with HTN

Answer 18

BP should be controlled to ~ 160/90 mmHg prior to elective surgery → if new antihypertensive is introduced, a stabilisation period of at least 2wks should be allowed

Question 19

Peri-operative Mx of pts with IHD

Answer 19

Pts with unstable/poorly controlled angina should be further investigated by cardiologist

• May need thrombolysis, percutaneous coronary balloon angioplasty, statins, coronary artery bypass surgery or coronary stenting prior to non-cardiac surgery
• Perioperative MI associated with high mortality (15–25%) → occurs when oxygen demand of myocardium exceeds supply
  
  • Myocardial ischaemia can be precipitated by hypotension, tachycardia and procoagulant states (e.g., inflammatory response to surgery)
  • Optimise myocardial oxygen supply and demand ratio: may require further Ix and elective surgery should be postponed for 3-6 months after proven MI to reduce risk of peri-operative reinfarction (high mortality)
  • Consider prophylactic b-blockade → reduced deaths and MIs combined, but increased risk of hypotension, strokes and deaths overall (controversial)
    
    • Pts already on b-blockers should continue taking them in the perioperative period
    • When b-blockers added preoperatively, they must be titrated to HR and BP over at least a week before surgery

Question 20

Peri-operative Mx of pt with coronary stents

Answer 20

Pts may have had coronary stents inserted for IHD → ask pt about effectiveness of Tx and concurrent antiplatelet medications (e.g. clopidrogel and/or aspirin)

• Risk of stent thrombosis → MI and death reduced if elective surgery delayed until after dual antiplatelet therapy is stopped (~6wks after bare metal and 12 months after drug-eluting stent insertion)
• If surgery cannot be postponed and risk of significant perioperative bleeding is low, dual antiplatelet therapy can be continued during surgery
  
  • If surgery poses significant risk (spinal, intracranial, cardiac, posterior chamber of eye and prostate surgery), clopidrogel may be stopped and aspirin continued with cardiology consult

Most long-term cardiac medications should be continued over perioperative period → ongoing Tx with betablockers and statins reduces perioperative morbidity and mortality

Question 21

Perioperative Mx of pt with dysrhythmia

Answer 21

• AF pt → start beta-blockers, digoxin or calcium channel blockers preoperatively (or continue if already on them) to control the rate +/- rhythm
  
  • CO can increase by 15% if sinus rhythm restored → reduces risk of perioperative myocardial ischaemia and infarction
• Warfarin in AF pts should be stopped 5 days preoperatively → INR of 1.5 or less is safe for most surgery (alternative anticoagulation not needed)
• Implanted pacemaker and cardiac defibrillator checks and appropriate reprogramming should be done preoperatively
• Bipolar diathermy activity during surgery may be sensed by pacemaker as VF so cardioversion and overpace modes may be turned off (switch on after surgery) or converted to ‘ventricle paced, not sensed with no response to sensing’ (VOO) mode esp. if bipolar diathermy cannot be used
• Symptomatic heart blocks and asymptomatic second- (Mobitz II) and third-degree heart blocks discovered at preoperative assessment clinic → cardiology consultation and temporary pacemaker insertion

Question 22

Peri-operative Mx of pt with valvular disease

Answer 22

• Anaesthetic and cardiology consultation in pts w/ moderate valvular diseases → anaesthetic management altered to achieve haemodynamic stability
• Pts with severe aortic and mitral stenosis may benefit from valvuloplasty before undergoing elective non-cardiac surgery (cardiology consult)
• Mechanical heart valves → stop warfarin 5 days before surgery → when INR falls below 1.5 start unfractionated heparin infusion → monitor APTT to keep it at 1.5x normal → stop infusion 2hrs before surgery

Question 23

Peri-operative Mx of pt with LV dysfunction

Answer 23

end result of several conditions including IHD, HTN, cardiomyopathies and valve dysfunction

• decompensated heart failure puts patients at risk of multiorgan failure
• highest risk = pts with EF < 35% or pts with undiagnosed or underestimated failure
• must assess functional capacity → surgery may have to be delayed for Ix (e.g., echoc) and/or
  for optimisation of medical therapy
• drugs used in chronic heart failure have significant implications for perioperative care → continue b-blockers and ACE inhibitors (unless renal perfusion is to be significantly affected)

Question 24

Intra-operative Mx of pt with cardiac disease

Answer 24

• Use anaesthesia techniques that dampen stress response to surgery (esp. minimising pain) and provide good degree of cardiac stability
• Anaesthesia should avoid tachycardia, systolic HTN and diastolic hypotension
• LV failure → anaesthesia should ensure minimal myocardial depression and change in afterload during surgery
• Use invasive central venous and arterial blood pressure monitoring (esp. if large fluid shifts excepted to occur)
• Accurately monitor blood loss and maintain Hb at level suitable for pt’s cardiac risk factors
• Arrhythmias must be rapidly brought under control esp. AF → correcting electrolyte imbalance is crucial

Question 25

Post-operative Mx of pts with cardiac disease

Answer 25

• Admission to a HDU should be considered for patients with IHD
• Supplemental oxygen therapy for 3 to 4 days (IHD pts)
• Troponin testing allows early diagnosis of perioperative MIs but limited reperfusion options due to risk of bleeding from surgical site
• Mechanical heart valves: heparin and warfarin should be started post-op → heparin stopped when full effect of warfarin is realised

Question 26

Minimising myocardial ischaemia perioperatively

Answer 26

Question 27

Pre-operative prevention of thromboembolic disease

Answer 27

Risk-assess all pts preoperatively for risk of venous thromboembolism (VTE) vs risk of bleeding
- consider type of procedure and need for GA
- consider bleeding risks e.g., PUD, liver failure, stroke, thrombocytopaenia etc.
- consider clinical consequences of bleeding

Avoid dehydration of pt

Question 28

Intra-operative prevention of thromboembolic disease

Answer 28

Avoid dehydration of pt

Mechanical VTE prophylaxis → graduated compression stockings, foot impulse devices, intermittent pneumatic compression devices

Regional anaesthesia (spinal or epidural) carries a lower risk of VTE than general anaesthesia
- If used, plan timing of pharmacological VTE prophylaxis to minimise risk of spinal haematoma

Question 29

Post-operative prevention of VTE

Answer 29

Avoid dehydration of pt

Early mobilisation and adequate pain management

Pharmacological prophylaxis: start anticoagulant ~ 6-12 hours post-op as long as risk of bleeding is low
- LMWH most common
- neurosurg: consider UFH due to risk of bleeding and reversibility

GCS or IPC or foot pump until fully mobile