Pre-operative medicine

Question 1

Fitness for surgery - initial introductory spiel?

Answer 1

I am concerned about the risks that this major procedure poses for this patient, both short-term peri-operative health as well as post-operative recovery and morbidity.

Question 2

6 categories of Revised Cardiac Risk Index (RCRI) - what is the % risk of major CV complications depending on no. of risk factors present? (MI, cardiac arrest, CHB, VF, pulmonary oedema)?

Answer 2

Revised Cardiac Risk Index:

• History of IHD (q-wave on ECG, current angina, active use of nitrates, Hx of AMI, +ve EST, but not hx of revascularization on it’s own)
• High-risk surgery (vascular/aortic)
• HF
• Diabetics with insulin use
• CRF - Cr >177
• Stroke/TIA

The risks are:

• None = 0.5%
• 1 = 1%
• 2 = 4%
• ≥3 = 9%

Question 3

What is MET and how can it be used to assess perioperative morbidity/mortality?

Answer 3

Metabolic Equivalent Time.

1 MET = basic ADLs only

4 = able to climb a flight of stairs without symptoms.

Max = 10 (can do strenuous exercise).

<4 MET is an indicator of high-risk

So a key question to ask the patient: can you climb a flight of stairs without any symptoms? If answer is no, high-risk.

Question 4

What do you think the risk of this patient’s perioperative morbidity/mortality is?

Answer 4

Approach: Spiel then 1) MET, 2) RCRI.

Recall that patient has <4 MET if he/she cannot climb a flight of stairs without symptoms.

Revised Cardiac Risk Index:

1. History of IHD (q-wave on ECG, current angina, active use of nitrates, Hx of AMI, +ve EST, but not hx of revascularization on it’s own)
2. High-risk surgery (vascular/aortic)
3. HF
4. Diabetics with insulin use
5. CRF - Cr >177
6. Stroke/TIA

“This patient has a poor functional capacity as evidenced by development of SOB on walking up the stairs, objectively eqivalent with MET <4.

Furthermore, he/she has (significant IHD requiring nitrates, hx of HF, diabetic with insulin use) therefore has a significant risk of major cardiovascular complications - according to RCRI of 3 equating to almost 10%”

In order to further assess the peri-operative risk for this patient, I would…

Question 5

In which clinical situations would you defer elective surgery in order to stabilise the patient from Cardiovascular view point? (5)

Answer 5

1. Unstable coronary syndrome - Recent MI or unstable angina within last 6 weeks (optimal > 3 months)
2. Recent PCI within 6 weeks (optimal > 3 mnth)
3. Decompensated heart failure, significant valvular disease, or arrhythmia (high-grade)

Question 6

What are the key factors to consider when you are assessing the risk of perioperative pulmonary complications? (4)

Answer 6

Key facts to consider:

1. Thoracic & Upper abdominal surgery → impairs pulmonary physiology with reduction in VC by 50%, FRC by 30%. Risk further increased by underlying COPD/Asthma.
2. Smoking increases post-op pulmonary complication by 70%
3. Functional status (if poor, doubles pneumonia risk)
4. Malnutrition, especially recent weight loss >10kg (doubles the risk)

Question 7

Do you have any concerns regarding this patient’s pulmonary status for a planed Bariatric surgery? (Hx of active smoking, SOBOE on walking up the stairs)

Answer 7

Key facts to consider:

1. Thoracic & Upper abdominal surgery → impairs pulmonary physiology with a reduction in VC by 50%, FRC by 30%. Risk further increased by underlying COPD/Asthma.
2. Smoking increases post-op pulmonary complication by 70%
3. Functional status (if poor, doubles pneumonia risk)
4. Malnutrition, especially recent weight loss >10kg (doubles the risk)

“I am concerned about his/her risk of perioperative pulmonary complications too as Bariatric surgery will further challenge the lungs already restricted by significant obesity which would impair VC by 50%.

Furthermore, there is more than twice the risk of post-operative pneumonia as he/she still smokes, and has a functional status.

In the first instance, I would like to confirm her pulmonary status by reviewing/organizing a formal PFT (or at least spirometry) to confirm my suspicion. “

Question 8

Do you think this patient needs Stress testing or TTE? (what are the key facts to know?). What about 24h Holter?

Answer 8

In general, these tests are only indicated (even in patients with known or suspected CAD, valve, arrhythmia disease) if there was another indication (other than surgery).

This is because there is no evidence that further diagnostic or prognostic evaluation improves surgical outcomes.

So, if the patient is symptomatic (e.g. angina, unexplained SOB, syncope…etc) I would do them but otherwise, probably do an ECG looking for any ischaemic changes or new BBB…etc.

Would do TTE if new murmur or if patient in HF but otherwise as above.

Likewise for Holter monitor - generally not indicated unless it was indicated already with hx of significant bradycardia or tachycardia previously not evaluated.

However, of course, if patient had symptoms of angina or SOBOE, I would organise stress test and if positive I would strongly consider PCI.

Question 9

Would you perform a spirometry or PFT for this patient prior to elective surgery?

Answer 9

Would generally perform if:

1. Known lung disease: e.g. to assess if patient has COAD and has airflow obstruction optimally reduced (i.e. identifies patient who will benefit from more aggressive tx)
2. Unexplained SOB, especially if cardiac cause is ddx (again changes Mx)
3. Useful to triage patient for b-blocker use.

However, should not be ordered routinely in the absence of respiratory symptoms.

Question 10

What is your approach to optimizing this patient’s cardiorespiratory status prior to operation?

Answer 10

Confirm dx: would review prior investigations & confirm my clinical suspicions.

A: identify & treat other reversible causes such as anemia, infection, thyroid.

S: would perform a baseline bloods, ECG (looking for new changes), CXR (pulmonary oedema/infection) that would change management. In this case, I would perform MIBI/TTE/PFT because… (or why otherwise)

T: non-pharm

• Smoking cessation at least 8 weeks prior (to reduce post-op pulmonary complications)
• Exercise as functional capacity is the single most important factor a/w peri-op issues
• Moderation of ETOH, weight loss, diet to optimise BSLs.
• Educate on lung expanding maneuvers, initiate Chest PT - best time to teach patient is at pre-op (breathing exercise, inspiratory muscle training, incentive spirometry)

T: pharm

• Start Statin ASAP (1A) if untreated with high CV risk factors
• ACEi: WH for a day - minimises perioperative hypotension.
• B-blockers: generally don’t start, unless it was indicated from previously (in which case consider, start at least 1 month prior). If was on it already, continue (no benefit in stopping it or changing to other BB)
• Antiplatelets: continue if prior coronary revascularization but if just won’t for primary/secondary prevention, can cease 5-7d prior.
• Optimise COAD (if patient has it)
• Angiogram only if high-risk features in non-invasive testing and OT can be deferred during the crucial time of DAPT after stenting

Involve

• Discuss with anaesthest/surgeon to minimise operative risk factors
• Regional anaesthesia?
• Shorter procedure possible?
• Avoiding long-acting neuromuscular blocking agent

Ensure follow-up and monitor Complications

• Reassess the patient post-op
• Avoid long-acting opioids (risk of respiratory depression)
• Avoiding NSAIDs
• Assess for any angina symptoms and HF and investigate as appropriate
• Ensure PT is involved and the patient is having appropriate chest PT

Question 11

What are the key management issues you must identify and bring-up as an issue for peri-op medicine Long-case? (6)

Answer 11

1. Cardiovascular risk
2. Pulmonary risk
3. Diabetes Mx
4. Stress dosing steroids
5. Anticoagulation
6. Device Mx

Question 12

What is your approach to managing this patient’s anticoagulation in preparation for surgery?

Answer 12

The aim is to minimise the period of anticoagulation interruption whilst minimising risk of bleeding peri/post op.

Firstly I would quantify the risk of TE and major bleeding.

This patient’s CHADS2VASC score is (…), indicating a low/high/very-high risk of VTE without anticoagulation, equivalent of (…)% risk of stroke per-year.

On the other hand, (operation type) is a procedure with low/intermediate/high-risk of bleeding. The risk of bleeding is further contributed by (risk factors for bleeding).

Thus this patient has

low/intermediate/high/very high risk of TE and;

low/im/high/v.high risk of bleeding.

Based on this, I would/would not bridge (Warfarin/rarely NOAC) with Heparin or LMWH

I would recommence anticoagulant as soon as able once hemostasis is secured, ensuring that the period interruption is shortened as much as possible.

Question 13

CHADS2VASC? Max score, % risk of ischaemic stroke per year (low vs. high risk, rough % stroke risk per year).

Answer 13

CCF (1)

HTN (1)

Age≥75 (1)

Diabetes (1)

Stroke (2)

Vasc (IHD, PVD, VTE) - (1)

Age ≥65 (1)

Sex (female - 1)

Max = 9

Low-risk = 0-1 (~0.5% per-year)

High-risk = 2-5 (2 to 7% per-year)

Very high-risk = ≥6 (at least 10% per-year)

Question 14

What are high-risk procedures (i.e. 2-day risk of major bleed 2-4%)? (4 categories) + (2 exceptions)

Answer 14

Long operation (>45 minutes) - any.

Biopsies: only kidney biopsy is high-risk. Biopsies of majority of tissues (bladder/prostate/thyroid/breast/LN are not high-risk). Note endoscopic/bronchoscopic biopsy, stent are not high-risk as long as no sphincterotomy or polypectomy.

Bloody procedures: Endoscopic FNA, dilatation, polypectomy, ERCP (sphincterotomy).

Any major cardiac, vascular, neuro, orthopaedic or general surgery

Exception = hysterectomy, hernia repair, cholecystectomy

Question 15

Other than type of operations, are there any risk factors for perioperative bleeding that this patient may have? (HASBLED score)

Answer 15

HASBLED score

HTN

Abnormal renal (Cr >200) or liver function.

Stroke

Bleeding disorders or previous major bleeding (requiring hospitalisation or transfusion)

Labile INR

Elderly (>65)

Drugs & Alcohol

Question 16

• A 76-year-old female with non-valvular atrial fibrillation, hypertension, and prior stroke three months ago, receiving warfarin, requires elective hip replacement with neuraxial anesthesia; renal function is normal, and weight is 75 kg.
• What is your anticoagulation strategy? – both pre & post op

Answer 16

This patient has a very high thromboembolic risk (CV score = 6) and a high bleeding risk (major orthopaedic surgery) - hence I would bridge her warfarin in this case.

• Cease warfarin 5 days before procedure (last dose on OT day -6)
• Commence treatment dose LMWH 3 days prior (e.g. clexande 75mg BD)
• Omit PM dose of clexane a day before surgery

Post-op

• Start warfarin within 24 hours of surgery (usual dose)
• Prophylactic clexane within 24 hours (e.g. 40mg SC Clexane)
• Once haemostasis is secured, start treatment dose clexane in day 2-3 post op – continue until INR is therapeutic

Question 17

•A 70-year-old male with non-valvular atrial fibrillation, diabetes, and hypertension receiving dabigatran who requires a colon resection for cancer; renal function is normal.

Answer 17

This patient has a moderate thrombotic risk (CV score = 3) and a high bleeding risk (major abdominal surgery).

• Omit dabigatran for two days before the procedure (last dose of dabigatran on day minus 3).
• No bridging.
• Use prophylactic-dose LMW heparin for VTE prophylaxis for the first two to three postoperative days.
• Resume dabigatran on day +2 or +3 after surgery, when patient is able to take medication by mouth.

Question 18

•A 55-year-old male with an unprovoked deep vein thrombosis (DVT) four months ago, receiving apixaban 5 mg twice daily, who requires a colonoscopy because of a personal history of premalignant colorectal polyps; renal function is normal.

Answer 18

This patient has a high thrombotic risk and a low bleeding risk (procedure with low-risk).

• Omit apixaban for one day before the procedure (last dose of apixaban on day minus 2).
• No bridging.
• Resume apixaban the day after the procedure, after at least 24 hours have elapsed when hemostasis secured.
• If the patient requires polyp removal, delay resumption of apixaban for one to two more days.

Question 19

Anticoagulation and surgery: timing of WH NOACs and recommencement?

Answer 19

Apixaban, Rivaroxaban, Dabigatran

• Low bleeding risk: WH for 1 day (last dose OT day -2)
• High bleeding risk: WH for 2 days (last dose OT day -3)
• Dabigatran: if CrCl 30-50, WH for 4 days (if high bleed risk) or 2 days (if low bleed risk)

Recommence

• Low bleed risk: day 1 post-op (24 hours post-OT)
• High bleed risk: day 2-3 post-op

Question 20

In which situations would you bridge warfarin (regardless of AF and CHADS2VASC) - (3)

Answer 20

Mechanical mitral (always) or aortic (with additional stroke RFs) valves

VTE/Stroke/TIA within last 3 months

Recent coronary stenting

Question 21

Patient on warfarin for AF, undergoing cardiac implantable device or catheter ablation. Would you continue or cease anticoagulation?

Answer 21

Continuing warfarin was associated with a lower risk of bleeding in patients on the BRUISE CONTROL trial who were undergoing implantation of a cardiac implantable electronic device (eg, pacemaker, implantable cardioverter-defibrillator) and patients on the COMPARE trial who were undergoing catheter ablation for atrial fibrillation.

Question 22

What is your approach to managing this patient’s warfarin who is on it for mechanical heart valve?

Answer 22

Generally, bridging is required unless the valve is AV and patient has no TE risk factors (majority will have it) or AV is very new.

Approach

• Cease warfarin 2-4 days prior to the procedure (aim = INR <1.5 for major surgical procedure)
• If on Aspirin, continue unless v. high risk of bleeding (NSx, prostate – if so cease 5 days before)
• Start UFH or LMWH when INR <2 (usually ~2 days prior to OT)
• LMWH – last dose = 24 hours before, UMH 4-6 hours before
• Recommence warfarin 12-24 hours post op (when adequate haemostasis)

Post op bridging (basically approach depends on bleeding risk post-op)

• Start UFH or LMWH in 24 hours if haemostasis achieved, low risk bleeding
• If high risk of bleeding: start 2-3 days after procedure and when haemostasis is secure
• Consider completely avoiding giving UFH or LMWH

Question 23

Peri-operative management of diabetic, type II, who are only on OHGs with no insulin. Mx?

Answer 23

WH OHG on the day of operation and sliding scale insulin until patient can eat.

Question 24

Your approach to type II diabetic who are on insulin (or type I diabetic)? if patient is on pre-mixed insulin or intermediate acting insulin, what would you do?

Answer 24

If the procedure is long/complex (>2 meals skipped) - IV insulin + Glucose infusion as per local protocol. Watch BSL 1-2 hourly, monitor K and Bicarbonate.

If short/simple procedure;

1. A night before, consider reducing evening basal insulin by 25% if history of hypo or low baseline BSL levels.
2. WH rapid/short-acting insulin mane.
3. I would prefer changing intermediate-acting or pre-mixed insulin to long-acting (e.g. Lanctus)
4. Give 1/2 or 2/3 of total morning dose insulin (short+intermediate+long) as long-acting in the morning
5. Start 4% dex 1/5th NS at 100mls per hour to avoid metabolic changes of starbation
6. Monitor BSLs hourly and supplemental insulin as required
7. Reinstate back to usual insulin once patient is eating well.

Question 25

Patient who are on insulin infusion – when would you recommence SC insulin and the timing of 1st SC insulin?

Answer 25

• Should be continued until patient eating solid foods at which point the insulin can be switched to SC
• The 1st dose of SC must be given before cessation of IV infusion because the short t1/2 of IV insulin is very short.
• For long-acting insulin – should be given 2-3 hours before cessation
• Short/rapid acting: 1-2 hours before stopping infusion
• Should continue with IV dextrose to prevent hypo

Question 26

What are potential problems of surgery & implantable cardiac device? (2)

Answer 26

•Risk from electromagnetic interference (EMI)

1. Inhibition of pacing due to ventricular oversensing of EMI – where devices senses EMI that should be ignored as native R-waves
2. Excitation: misinterpretation of EMI as a tachyarrythmia → inappropriate shocks
3. Direct damage to device

Question 27

What is the potential problem with ILR?

Answer 27

•Unlikely to cause any harm but interrogation of the device is necessary because all recorded data may be lost during exposure to strong EMI

Question 28

Why is AICD/PPM check necessary prior to surgery? (3)

Answer 28

• To confirm appropriate function
• To determine if patient is pacing dependent (since pacing might be inhibited by EMI) – if so should be reprogrammed to an asynchronous pacing mode – i.e. pacing at fixed rate
• If patient has ICD - to prevent inappropriate shock from overseeing, can we use the magnet or does it have to be reprogrammed?

Question 29

So when would you use the magnet in patient with PPM/AICD? When would you NOT use it?

Answer 29

If the patient is pacing dependent and/or there is risk of inappropriate sensing of EMI and shock.

• Magnet: for most PMs, magnet application will initiate asynchronous pacing at a fixed rate with a fixed AV delay & for most ICDs a _magnet will suspend tachyarrythmia detection/shoc_k. This occurs without needing to change the mode of ICD – so easy to use
• However reprogramming is necessary when an asynchronous pacing may result in cardiac compromise → requires reprogramming to optimal setting or where magnet may interfere with surgical sterile field

Question 30

So what are the key questions to ask when assessing functional status for fitness for operative Mx?

Answer 30

1. Can you walk up the flight of stairs/walk up the hill without symptoms?
2. Can you do gardening without getting to tired?
3. Can you run a short distance?

If can’t do, MET <4, hence poor functional capacity.