9.2 Cardiac & Pulmonary Risk Stratification, Diagnostic Testing & Optimization

9.2 Cardiac & Pulmonary Risk Stratification, Diagnostic Testing & Optimization

Perioperative cardiovascular and pulmonary complications are leading causes of morbidity, prolonged hospitalization, and mortality after noncardiac surgery. An evidence-based risk assessment allows the anesthesia provider to identify high-risk patients, initiate targeted preoperative optimization, guide intraoperative monitoring, and plan appropriate postoperative disposition.

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1. ACC/AHA Perioperative Cardiovascular Evaluation Algorithm

The American College of Cardiology / American Heart Association (ACC/AHA) guidelines establish a stepwise algorithmic approach to assess cardiovascular risk prior to noncardiac surgery.

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|                ACC/AHA STEPWISE CARDIAC EVALUATION PATHWAY              |
+-------------------+-----------------------------+-----------------------+
| Step 1: Urgency   | Step 2: Active Conditions   | Step 3: Risk & METs   |
| - Emergency:      | - Unstable angina           | - Low risk (<1%): Go  |
|   Proceed to OR   | - Decompensated HF          | - Elevated risk +     |
| - Elective:       | - Significant arrhythmia    |   METs >=4: Go        |
|   Evaluate Active | - Severe symptomatic AS     | - METs <4: RCRI &     |
|   Conditions      |   --> CANCEL/OPTIMIZE FIRST |   selective testing   |
+-------------------+-----------------------------+-----------------------+

Step 1: Surgical Urgency

• Emergency Surgery: If the procedure is an emergency (life or limb threatening), proceed immediately to the operating room with appropriate invasive hemodynamic monitoring, perioperative surveillance, and postop optimization.
• Elective / Urgent Surgery: Proceed to Step 2.

Step 2: Active Cardiac Conditions (The "Big 4" Red Flags)

If any of the following active cardiac conditions are present, elective noncardiac surgery must be cancelled or delayed for urgent cardiology consultation, diagnostic evaluation, and medical therapy:

1. Unstable Coronary Syndromes:
   • Unstable or severe angina (Canadian Cardiovascular Society [CCS] Class III or IV).
   • Recent myocardial infarction within 30 days with evidence of ongoing ischemic risk.
2. Decompensated Heart Failure:
   • New-onset heart failure, worsening chronic heart failure, or New York Heart Association (NYHA) Functional Class IV dyspnea at rest, paroxysmal nocturnal dyspnea, or pulmonary edema.
3. Significant Cardiac Arrhythmias:
   • High-grade atrioventricular block (Mobitz Type II second-degree AV block, third-degree / complete heart block).
   • Symptomatic ventricular arrhythmias.
   • Supraventricular tachyarrhythmias (including atrial fibrillation) with uncontrolled, rapid ventricular response ($HR > 100\text{ bpm}$ at rest).
   • Symptomatic bradycardia or newly recognized ventricular tachycardia.
4. Severe Symptomatic Valvular Heart Disease:
   • Severe Aortic Stenosis: Characterized by aortic valve area $<1.0\text{ cm}^2$, mean transvalvular pressure gradient $>40\text{ mmHg}$, or peak aortic jet velocity $>4.0\text{ m/s}$, accompanied by classic triad symptoms: angina, syncope, or dyspnea. Severe symptomatic AS carries a catastrophic risk of sudden perioperative cardiac collapse and warrants surgical or transcatheter aortic valve replacement (TAVR) prior to elective noncardiac surgery.
   • Severe Symptomatic Mitral Stenosis: Mitral valve area $<1.5\text{ cm}^2$ with pulmonary hypertension or heart failure.

Step 3: Surgical Risk & Functional Capacity Assessment

If active cardiac conditions are excluded, surgical procedural risk is categorized based on expected 30-day Major Adverse Cardiac Event (MACE) risk (death or nonfatal MI):

• Low-Risk Procedures ($<1%$ MACE Risk): Ambulatory surgery, superficial surgery, cataract extraction, breast surgery, endoscopy. Patients can proceed directly to surgery without further cardiac testing.
• Elevated-Risk Procedures ($\ge 1%$ MACE Risk): Intraperitoneal, intrathoracic, vascular, major orthopedic, or major urologic/gynecologic procedures.
  • Assess functional capacity: If functional capacity is $\ge 4\text{ METs}$ without symptoms, proceed to surgery.
  • If functional capacity is $<4\text{ METs}$ or unknown, evaluate clinical risk factors using the Revised Cardiac Risk Index (RCRI).

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2. Revised Cardiac Risk Index (RCRI / Lee Criteria)

The RCRI is the most widely utilized and validated clinical risk prediction tool for perioperative cardiac morbidity in noncardiac surgery. It assigns 1 point for each of 6 independent clinical predictors.

The 6 Independent RCRI Predictors

RCRI Risk Stratification & 30-Day MACE Rates

NCE Management Guideline: If an elevated-risk surgical patient has poor functional capacity ($<4\text{ METs}$) and elevated RCRI score ($\ge 2$ predictors), pharmacologic stress testing (dobutamine stress echocardiography or dipyridamole/adenosine myocardial perfusion imaging) is recommended only if the results will change clinical management (e.g., cancel elective surgery, trigger coronary revascularization, or alter monitoring strategy).

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3. Postoperative Pulmonary Complications & The ARISCAT Score

Postoperative pulmonary complications (PPCs)—including atelectasis, pneumonia, acute respiratory failure, bronchospasm, and aspiration pneumonitis—occur in up to 5–10% of all noncardiac surgical patients and rival cardiac complications in incidence and cost.

The ARISCAT Risk Model (Canet et al.)

The ARISCAT (Assess Respiratory Risk in Surgical Patients in Catalonia) score calculates PPC risk based on 7 independent factors:

1. Age: $\le 50\text{ yrs}$ (0 pts), $51-80\text{ yrs}$ (3 pts), $>80\text{ yrs}$ (16 pts).
2. Preoperative $SpO_2$ on Room Air: $\ge 96%$ (0 pts), $91-95%$ (8 pts), $\le 90%$ (24 pts).
3. Respiratory Infection in Past Month: Yes (17 pts).
4. Preoperative Anemia ($Hb \le 10\text{ g/dL}$): Yes (11 pts).
5. Surgical Incision Site: Peripheral (0 pts), Upper abdominal (15 pts), Intrathoracic (24 pts).
6. Duration of Surgery: $\le 2\text{ hours}$ (0 pts), $2-3\text{ hours}$ (16 pts), $>3\text{ hours}$ (23 pts).
7. Emergency Surgery: Yes (8 pts).

• ARISCAT Risk Tiers: Low risk ($<26\text{ pts}$, PPC risk $\approx 1.6%$); Intermediate risk ($26-44\text{ pts}$, PPC risk $\approx 13.3%$); High risk ($\ge 45\text{ pts}$, PPC risk $\approx 42.1%$).

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4. Obstructive Sleep Apnea (OSA) & The STOP-Bang Screening Tool

Undiagnosed obstructive sleep apnea is highly prevalent among surgical patients. Repetitive upper airway collapse during sleep produces nocturnal hypoxemia, hypercapnia, systemic and pulmonary hypertension, polycythemia, and biventricular strain. Anesthetic agents, sedatives, and opioids exacerbate upper airway collapsibility and suppress arousal reflexes.

+-------------------------------------------------------------------------+
|                     THE STOP-BANG SCREENING CRITERIA                    |
+-------------------------------------------------------------------------+
| S - Snoring: Do you snore loudly (louder than talking/through door)?   |
| T - Tired: Do you often feel tired, fatigued, or sleepy during daytime? |
| O - Observed: Has anyone observed you stop breathing during sleep?      |
| P - Pressure: Do you have or are you being treated for hypertension?   |
| B - BMI: Body Mass Index > 35 kg/m²?                                    |
| A - Age: Age > 50 years?                                                |
| N - Neck Circumference: > 43 cm (17 in) male, > 40 cm (16 in) female?   |
| G - Gender: Male?                                                       |
+-------------------------------------------------------------------------+

STOP-Bang Risk Stratification

• Low Risk: 0 – 2 points (High negative predictive value for moderate/severe OSA).
• Intermediate Risk: 3 – 4 points.
• High Risk of Moderate-to-Severe OSA:
  • Score $\ge 5$ points, OR
  • $\ge 2$ "STOP" criteria positive PLUS Male gender, OR
  • $\ge 2$ "STOP" criteria positive PLUS BMI $>35\text{ kg/m}^2$, OR
  • $\ge 2$ "STOP" criteria positive PLUS Neck circumference $>43\text{ cm}$ (male) / $>40\text{ cm}$ (female).

Perioperative Anesthetic Management of High-Risk OSA Patients

1. Preoperative: Instruct patients to bring their home continuous positive airway pressure (CPAP) machine to the surgical center on the day of surgery.
2. Intraoperative: Utilize regional anesthesia or peripheral nerve blocks whenever feasible. For general anesthesia, avoid or minimize long-acting opioids; employ multimodal analgesia (acetaminophen, ketorolac, ketamine, dexmedetomidine, lidocaine infusions). Elevate head of bed / ramp position for preoxygenation, induction, and extubation.
3. Postoperative: Fully reverse neuromuscular blockade (document TOF ratio $>0.9$ or utilize sugammadex). Extubate only when fully awake and following commands. Initiate immediate postop CPAP in recovery.

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5. Smoking Cessation Physiology & Perioperative Time Course

Cigarette smoking exposes the body to thousands of toxic compounds, principally carbon monoxide, nicotine, cyanide, and particulate irritants. Understanding the exact physiological time course of smoking cessation is a heavily tested NBCRNA topic.

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|                   PHYSIOLOGICAL TIMELINE OF SMOKING CESSATION           |
+--------------------+----------------------------+-----------------------+
| 12 - 24 Hours      | 1 - 2 Weeks                | > 4 - 8 Weeks         |
| - CO elimination   | - Decreased airway         | - Normal ciliary beat |
| - P50 shifts right |   hyperreactivity          | - Sputum vol drops    |
| - Nicotine drops   | - Transient cough increase | - PPCs significantly  |
| - HR & BP normalize| - Sputum mobilization      |   reduced             |
+--------------------+----------------------------+-----------------------+

Time Course of Smoking Cessation

NCE Pearl — The Old "48-Hour Cessation Paradox": Historical dogma suggested that stopping smoking 24–48 hours preoperatively was harmful due to increased mucus plugging and uncoordinated ciliated clearance. Modern evidence confirms that stopping smoking at ANY time prior to surgery is beneficial: 12–24 hours optimizes oxygenation and cardiovascular parameters, while $>4-8$ weeks optimizes pulmonary parenchyma and reduces PPCs.

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6. Evidence-Based Indications for Preoperative Diagnostic Testing

Routine, untargeted screening tests ("routine panel batteries") in healthy, asymptomatic patients are wasteful, generate false positives, and fail to alter management or improve clinical outcomes. Preoperative testing must be ordered selectively based on specific clinical indications.

Indication Matrix for Diagnostic Tests