# Perioperative Medicine: Risk Assessment Beyond the Heart

## Introduction

Perioperative medicine encompasses the comprehensive evaluation and management of patients undergoing surgical procedures. While cardiac risk assessment has traditionally dominated preoperative evaluation, **non-cardiac complications** account for significant morbidity and mortality. A holistic approach to risk assessment improves outcomes and reduces preventable harm.

## Preoperative Pulmonary Risk Assessment

### Risk Factors for Postoperative Pulmonary Complications

- **Patient-related factors**: age > 60, COPD, current smoking, obesity (BMI > 40), obstructive sleep apnea, functional dependence
- **Procedure-related factors**: upper abdominal or thoracic surgery, duration > 3 hours, emergency surgery, general anesthesia
- The **ARISCAT score** stratifies patients into low, intermediate, and high risk for postoperative pulmonary complications
- Preoperative spirometry is **not routinely recommended** unless evaluating unexplained dyspnea

### Risk Reduction Strategies

- Smoking cessation at least **4-8 weeks** before surgery
- Preoperative inspiratory muscle training and **incentive spirometry** education
- Lung-protective ventilation strategies intraoperatively
- Early mobilization and aggressive pulmonary toilet postoperatively

![Preoperative pulmonary risk stratification algorithm](images/preop-pulmonary-risk.png)

## Renal Risk Assessment

- Preoperative **estimated GFR (eGFR)** is a strong independent predictor of postoperative complications
- The **KDIGO guidelines** recommend identifying patients with CKD stage 3 or higher for enhanced monitoring
- **Nephrotoxin avoidance**: minimize contrast, NSAIDs, and aminoglycosides perioperatively
- Adequate volume status and avoidance of prolonged hypotension reduce acute kidney injury risk
- Patients on dialysis require coordination of dialysis timing relative to surgery

## Hepatic Risk Assessment

### Child-Turcotte-Pugh and MELD Scores

| Classification | Perioperative Mortality | Surgical Decision |
|---------------|------------------------|-------------------|
| Child-Pugh A (5-6 pts) | ~2% | Generally acceptable risk |
| Child-Pugh B (7-9 pts) | ~12% | Elevated risk; optimize first |
| Child-Pugh C (10-15 pts) | ~50% | Prohibitive for elective surgery |
| MELD > 15 | Significantly increased | Avoid elective procedures |

- **Child-Pugh Class A**: generally acceptable surgical risk
- **Child-Pugh Class B**: elevated risk; optimize before elective procedures
- **Child-Pugh Class C**: prohibitive risk for most elective surgeries
- **MELD score > 15** is associated with significantly increased perioperative mortality
- Acute hepatitis is a contraindication to elective surgery

## Hematologic Considerations

- Assess bleeding risk with a focused **bleeding history** rather than routine coagulation studies
- Manage **anticoagulation bridging** based on thromboembolic risk (CHA2DS2-VASc, mechanical valves)
- **Thrombocytopenia**: platelet count > 50,000/mcL is generally adequate for most procedures
- Develop a perioperative **venous thromboembolism (VTE) prophylaxis** plan using the Caprini score

![Perioperative anticoagulation management decision tree](images/periop-anticoag-mgmt.png)

## Nutritional and Functional Assessment

- **Malnutrition** increases surgical site infections, delayed wound healing, and length of stay
- Screen with tools such as the **Malnutrition Universal Screening Tool (MUST)** or **Subjective Global Assessment**
- Preoperative **albumin < 3.0 g/dL** is a strong predictor of 30-day morbidity and mortality
- Consider **prehabilitation** programs combining exercise, nutrition optimization, and psychological support
- Frailty assessment using tools such as the **Clinical Frailty Scale** identifies patients at high risk for poor outcomes

## Endocrine and Metabolic Optimization

- **Perioperative glucose control**: target glucose 140-180 mg/dL; avoid hypoglycemia
- **Thyroid disease**: severe hypothyroidism and thyroid storm must be addressed before elective surgery
- **Adrenal insufficiency**: stress-dose steroids for patients on chronic corticosteroids undergoing major surgery
- Manage **diabetes medications** perioperatively: hold metformin day of surgery, reduce insulin doses

![Perioperative glucose management protocol](images/periop-glucose-protocol.png)

## Integrated Risk Calculators

- The **ACS NSQIP Surgical Risk Calculator** provides procedure-specific risk estimates for multiple outcomes
- Incorporates patient comorbidities, procedure type, and functional status
- Facilitates **shared decision-making** by presenting individualized risk information
- Does not replace clinical judgment but adds objective data to the preoperative discussion

## Key Clinical Pearls

- Perioperative risk assessment must extend beyond cardiac evaluation to include pulmonary, renal, hepatic, hematologic, nutritional, and endocrine systems.
- Preoperative albumin and functional status are among the strongest predictors of postoperative outcomes across all surgical specialties.
- Frailty assessment and prehabilitation are emerging as essential components of preoperative optimization.
- Use validated risk calculators like ACS NSQIP to support shared decision-making with patients.
- A multidisciplinary perioperative medicine team improves care coordination and reduces complications.

## References

1. Fleisher LA, Fleischmann KE, Auerbach AD, et al. 2014 ACC/AHA Guideline on Perioperative Cardiovascular Evaluation and Management of Patients Undergoing Noncardiac Surgery. *Journal of the American College of Cardiology*. 2014;64(22):e77-e137.
2. Canet J, Gallart L, Gomar C, et al. Prediction of Postoperative Pulmonary Complications in a Population-based Surgical Cohort. *Anesthesiology*. 2010;113(6):1338-1350.
3. Bilimoria KY, Liu Y, Paruch JL, et al. Development and Evaluation of the Universal ACS NSQIP Surgical Risk Calculator. *Journal of the American College of Surgeons*. 2013;217(5):833-842.
4. Rockwood K, Song X, MacKnight C, et al. A Global Clinical Measure of Fitness and Frailty in Elderly People. *CMAJ*. 2005;173(5):489-495.