# Clinical Cases: Perioperative Medicine

## Case 1: Preoperative Cardiovascular Risk Assessment

### Patient Presentation
A 68-year-old man with a history of coronary artery disease (stents placed 8 months ago on dual antiplatelet therapy), type 2 diabetes, and hypertension is scheduled for elective right total hip replacement. He walks 2 blocks on flat ground without symptoms but gets short of breath climbing a flight of stairs. He had an MI 2 years ago and underwent PCI with drug-eluting stents. Current medications include aspirin 81 mg, clopidogrel 75 mg, metoprolol 50 mg BID, lisinopril 20 mg, atorvastatin 40 mg, and metformin 1000 mg BID.

### Vital Signs
- Blood Pressure: 138/82 mmHg
- Heart Rate: 68 bpm
- Respiratory Rate: 14/min
- Oxygen Saturation: 98% on room air

### Physical Examination
- General: Well-appearing
- Cardiovascular: Regular rhythm, no murmurs, no JVD
- Pulmonary: Clear
- Extremities: No edema, right hip pain with movement

### Recent Studies
- **ECG**: Normal sinus rhythm, Q waves in V1-V3 (old MI)
- **Echocardiogram (6 months ago)**: EF 50%, mild anterior wall hypokinesis
- **Hemoglobin A1c**: 7.2%
- **Creatinine**: 1.1 mg/dL

### Clinical Image
![RCRI Calculation](image_01.png)
*Figure 1: Revised Cardiac Risk Index (RCRI) calculator for perioperative cardiovascular risk assessment.*

**Image Source**: Educational illustration for teaching purposes.

### Questions

1. **Calculate this patient's Revised Cardiac Risk Index (RCRI) score. What does it indicate?**
   - A) Score 0-1 = low risk
   - B) Score 2 = intermediate risk
   - C) Score 3-4 = high risk
   - D) Score ≥5 = prohibitive risk

2. **What is the recommended management of antiplatelet therapy for this patient?**
   - A) Stop both aspirin and clopidogrel 7 days before surgery
   - B) Continue aspirin; stop clopidogrel 5-7 days before surgery if >6 months post-DES
   - C) Continue both through surgery
   - D) Bridge with heparin

3. **Should this patient undergo preoperative cardiac stress testing?**
   - A) Yes, all cardiac patients need stress testing
   - B) Only if functional capacity is <4 METs AND RCRI ≥3 AND it will change management
   - C) No, if stable CAD and adequate functional capacity
   - D) Only if EF <40%

4. **What is the perioperative management of metformin?**

5. **What beta-blocker management is recommended?**

### Answers

1. **RCRI calculation** (1 point each):
   - High-risk surgery (intraperitoneal, intrathoracic, suprainguinal vascular): No (orthopedic = intermediate risk)
   - Ischemic heart disease: Yes (+1)
   - History of CHF: No
   - History of cerebrovascular disease: No
   - Diabetes on insulin: No (on metformin)
   - Creatinine >2 mg/dL: No
   - **Total: 1 point = low risk** (estimated major cardiac event risk ~1%)

2. **B) Continue aspirin; stop clopidogrel 5-7 days before surgery if >6 months post-DES** - Guidelines:
   - After DES, dual antiplatelet therapy (DAPT) required for minimum 6 months
   - For elective surgery after 6 months: Continue aspirin, hold P2Y12 inhibitor 5-7 days
   - High bleeding risk surgery may require holding both
   - Bare metal stent: Minimum 1 month of DAPT before elective surgery
   - Never stop DAPT within first month post-stent (high stent thrombosis risk)

3. **C) No, if stable CAD and adequate functional capacity** - Stress testing approach:
   - Assess functional capacity: Can climb 1 flight of stairs = ≥4 METs
   - This patient has ≥4 METs functional capacity
   - If functional capacity adequate and stable CAD, proceed to surgery without testing
   - Stress testing only if: poor functional capacity (<4 METs) AND elevated risk AND results would change management

4. **Metformin perioperative management**:
   - Hold metformin on day of surgery and for 48 hours postoperatively
   - Resume once eating normally AND stable renal function confirmed
   - Concern: Risk of lactic acidosis with contrast exposure, hypoperfusion, or AKI
   - Monitor glucose; use insulin sliding scale as needed perioperatively

5. **Beta-blocker management**:
   - **Continue** beta-blockers in patients already taking them (abrupt withdrawal increases cardiac risk)
   - Do NOT start beta-blockers on day of surgery
   - If initiating beta-blocker for heart rate/BP control, start 2-7 days before surgery and titrate
   - Target heart rate 60-80 bpm; avoid bradycardia and hypotension

---

## Case 2: Perioperative Anticoagulation Management

### Patient Presentation
A 72-year-old woman with a history of atrial fibrillation, mechanical mitral valve replacement (3 years ago), and hypertension is scheduled for elective colon surgery for a recently diagnosed adenocarcinoma. She takes warfarin with an INR consistently 2.5-3.5. She has no history of stroke or TIA. Her CHA₂DS₂-VASc score is 4.

### Vital Signs
- Blood Pressure: 132/78 mmHg
- Heart Rate: 72 bpm (irregularly irregular)

### Physical Examination
- General: Well-appearing
- Cardiovascular: Irregularly irregular rhythm, mechanical valve click
- Abdomen: Non-tender, palpable mass in RLQ

### Current Medications
- Warfarin 5 mg daily
- Lisinopril 10 mg daily
- Metoprolol 50 mg BID

### Laboratory Results
- **INR**: 2.8
- **Creatinine**: 0.9 mg/dL
- **Hemoglobin**: 11.8 g/dL

### Clinical Image
![Bridging Anticoagulation](image_02.png)
*Figure 2: Algorithm for perioperative bridging anticoagulation based on thromboembolism risk.*

**Image Source**: Educational illustration for teaching purposes.

### Questions

1. **Does this patient require bridging anticoagulation?**
   - A) No, bridging is never indicated
   - B) Yes, because of mechanical mitral valve (high thromboembolism risk)
   - C) Only for atrial fibrillation alone
   - D) Depends on bleeding risk only

2. **What is the appropriate bridging protocol?**
   - A) Stop warfarin; no bridging needed
   - B) Stop warfarin 5 days before surgery; start therapeutic LMWH 3 days before; hold LMWH 24 hours before surgery
   - C) Continue warfarin through surgery
   - D) Switch to aspirin only

3. **When should anticoagulation be resumed postoperatively?**
   - A) Immediately after surgery
   - B) Resume LMWH 24-72 hours post-op if adequate hemostasis; restart warfarin when tolerating oral intake
   - C) Wait 7 days
   - D) Never resume, switch to antiplatelet

4. **How would management differ for a patient with atrial fibrillation alone (no mechanical valve)?**

5. **What is the role of DOACs in perioperative management?**

### Answers

1. **B) Yes, because of mechanical mitral valve (high thromboembolism risk)** - Bridging indications:
   - **High risk (bridge indicated)**: Mechanical mitral valve, mechanical aortic valve with additional risk factors, recent VTE (<3 months), AF with CHA₂DS₂-VASc ≥5 or recent stroke
   - **Moderate risk (individualize)**: Mechanical aortic valve, AF with CHA₂DS₂-VASc 3-4
   - **Low risk (no bridging)**: AF with CHA₂DS₂-VASc ≤2, VTE >12 months ago
   - Mechanical mitral valves have highest thromboembolism risk

2. **B) Stop warfarin 5 days before surgery; start therapeutic LMWH 3 days before; hold LMWH 24 hours before surgery** - Protocol:
   - Stop warfarin 5 days before surgery (INR should be ≤1.5)
   - Start therapeutic LMWH (enoxaparin 1 mg/kg BID) 3 days before surgery
   - Last dose of LMWH 24 hours before surgery
   - Check INR day before surgery; give vitamin K if still elevated
   - Surgery with INR ≤1.5

3. **B) Resume LMWH 24-72 hours post-op if adequate hemostasis; restart warfarin when tolerating oral intake** - Postoperative management:
   - Colon surgery is high bleeding risk - wait 48-72 hours for LMWH
   - Resume warfarin when tolerating oral intake (usually post-op day 1-2)
   - Continue LMWH until INR therapeutic for 24 hours
   - Balance thromboembolism risk against surgical bleeding risk

4. **Management for AF alone (no mechanical valve)**:
   - BRIDGE trial showed NO benefit of bridging for most AF patients
   - For AF with CHA₂DS₂-VASc ≤4: No bridging recommended
   - For AF with CHA₂DS₂-VASc ≥5 or recent stroke: Consider bridging
   - CHA₂DS₂-VASc 4: This patient would NOT need bridging for AF alone
   - The mechanical valve is the indication for bridging, not the AF

5. **DOAC perioperative management**:
   - Simpler than warfarin - predictable offset, no bridging needed
   - Hold based on half-life and renal function:
     - Normal renal function: Hold 24-48 hours before low bleeding risk surgery; 48-72 hours before high risk
     - CrCl 30-50: Hold 36-48 hours (low risk) or 48-96 hours (high risk)
     - CrCl 15-30: Hold 36-48 hours (low risk) or 96 hours (high risk)
   - Resume 24-72 hours postoperatively depending on bleeding risk
   - No bridging anticoagulation required for DOACs

---

## Case 3: Perioperative Glycemic Management

### Patient Presentation
A 56-year-old woman with type 2 diabetes, obesity, and obstructive sleep apnea is scheduled for laparoscopic sleeve gastrectomy. Her diabetes is managed with insulin glargine 40 units at bedtime and insulin lispro sliding scale with meals. She monitors her glucose at home with readings typically 140-200 mg/dL. Her HbA1c is 8.4%.

### Vital Signs
- Blood Pressure: 142/88 mmHg
- Heart Rate: 82 bpm
- BMI: 46 kg/m²

### Physical Examination
- General: Obese, well-appearing
- Cardiovascular: Regular rhythm, no murmurs
- Pulmonary: Clear but decreased breath sounds at bases
- Abdomen: Obese, non-tender

### Current Medications
- Insulin glargine 40 units nightly
- Insulin lispro per sliding scale
- Lisinopril 20 mg daily
- CPAP nightly

### Laboratory Results
- **HbA1c**: 8.4%
- **Fasting glucose**: 168 mg/dL
- **Creatinine**: 0.9 mg/dL

### Clinical Image
![Perioperative Glucose](image_03.png)
*Figure 3: Perioperative glucose management algorithm showing target ranges and insulin adjustment strategies.*

**Image Source**: Educational illustration for teaching purposes.

### Questions

1. **What is the target blood glucose range in the perioperative period?**
   - A) 80-120 mg/dL (tight control)
   - B) 140-180 mg/dL (moderate control)
   - C) 180-250 mg/dL
   - D) No specific target

2. **How should basal insulin be managed on the day of surgery?**
   - A) Hold completely
   - B) Give 50-80% of usual dose the night before/morning of surgery
   - C) Give full dose
   - D) Switch to oral medications

3. **What is the management of the prandial (mealtime) insulin?**
   - A) Continue as usual
   - B) Hold while NPO
   - C) Increase dose
   - D) Convert to basal insulin

4. **What are the risks of perioperative hyperglycemia?**

5. **What additional considerations apply to this patient given her obstructive sleep apnea?**

### Answers

1. **B) 140-180 mg/dL (moderate control)** - Target glucose:
   - ADA recommends 140-180 mg/dL for most hospitalized patients
   - Tighter control (110-140) may be appropriate in select patients if achievable without hypoglycemia
   - Avoid hypoglycemia (<70 mg/dL) - associated with worse outcomes
   - Severe hyperglycemia (>180-200) increases infection risk and impairs wound healing

2. **B) Give 50-80% of usual dose the night before/morning of surgery** - Basal insulin management:
   - Insulin glargine: Give 50-80% of usual dose
   - Some give full dose if glucose typically well-controlled; 50% if prone to hypoglycemia
   - For this patient: 20-32 units (50-80% of 40 units) the night before
   - NPH or intermediate insulin: Give 50% of dose
   - Never completely hold basal insulin in type 1 diabetes

3. **B) Hold while NPO** - Prandial insulin:
   - Hold rapid-acting/short-acting insulin when patient is NPO
   - Resume with meals postoperatively
   - Use correctional insulin (sliding scale) for hyperglycemia while NPO
   - Insulin infusion may be needed for poorly controlled patients or major surgery

4. **Risks of perioperative hyperglycemia**:
   - Increased surgical site infections
   - Impaired wound healing
   - Electrolyte abnormalities
   - Dehydration (osmotic diuresis)
   - Increased length of stay
   - Cardiovascular complications
   - Mortality (especially in cardiac surgery)
   - DKA or HHS risk (especially if insulin-deficient)

5. **OSA considerations**:
   - High risk for perioperative respiratory complications
   - Continue CPAP perioperatively
   - Minimize opioid use (increased apnea risk)
   - Consider monitored setting postoperatively
   - Positioning: Avoid supine position
   - Difficulty with intubation anticipated
   - Risk of postoperative oxygen desaturation
   - Bariatric surgery patients with OSA need careful monitoring

---

## Learning Points

1. **RCRI** estimates perioperative cardiac risk; functional capacity ≥4 METs often allows proceeding without further testing.

2. **Antiplatelet management**: Continue aspirin for most surgeries; hold P2Y12 inhibitors 5-7 days before; never stop DAPT within 1 month of bare metal stent or 6 months of DES.

3. **Bridging anticoagulation** is indicated for mechanical heart valves (especially mitral) and high-risk thromboembolism; most AF patients do not require bridging (BRIDGE trial).

4. **Target glucose 140-180 mg/dL** perioperatively; give 50-80% of basal insulin; hold prandial insulin when NPO.

5. **Beta-blockers** should be continued in patients already taking them; do not initiate on day of surgery.