What is the Kirklin/Barratt-Boyes (KBB) system used for in cardiac surgical procedures?

The Kirklin/Barratt-Boyes (KBB) System in Cardiac Surgery

The Kirklin/Barratt-Boyes (KBB) system is a risk stratification tool used to predict mortality and morbidity in patients undergoing cardiac surgical procedures, helping surgeons make informed decisions about patient selection and perioperative management.

Purpose and Development

The KBB system was developed to address the need for standardized risk assessment in cardiac surgery. It serves several key functions:

• Predicts operative mortality and major complications
• Allows for objective comparison of surgical outcomes across institutions
• Helps inform patients about their individual surgical risks
• Guides clinical decision-making for high-risk patients

Components and Scoring

The KBB system evaluates multiple risk factors including:

• Patient demographics (age, sex)
• Cardiac function parameters (ejection fraction, NYHA class)
• Comorbidities (pulmonary disease, renal dysfunction, neurological status)
• Procedural complexity
• Urgency of operation

Each factor is assigned a weighted score, with the cumulative score correlating with predicted mortality and major morbidity risk.

Clinical Application

The KBB system is particularly valuable in:

1. Preoperative risk assessment: Identifying high-risk patients who may benefit from additional optimization before surgery

2. Informed consent: Providing patients with personalized risk information based on their specific profile

3. Quality assurance: Allowing for risk-adjusted comparison of outcomes between surgeons and institutions

4. Resource allocation: Helping to determine appropriate level of postoperative care (e.g., ICU vs step-down unit)

Comparison with Other Risk Stratification Tools

While several cardiac surgical risk models exist, the KBB system has distinct characteristics:

• The EuroSCORE has shown higher predictive value for mortality in some populations 1
• The Society of Thoracic Surgeons (STS) score is widely used in North America and offers procedure-specific risk models 2
• The Aristotle Score (complexity score) is more commonly used in congenital heart surgery 3

Limitations and Considerations

• Risk models generally predict mortality better than morbidity 4
• Most scoring systems require periodic recalibration as surgical techniques and outcomes improve
• No single scoring system is perfect for all patient populations or procedures
• The KBB system, like other risk models, should be used as a tool to inform clinical judgment, not replace it

Recent Advances

Recent developments in risk stratification include:

• Integration of machine learning approaches for more accurate prediction
• Development of the American Association for Thoracic Surgery Quality Gateway (AQG) that uses advanced analytics to predict outcomes across the spectrum of cardiac surgery 5
• Incorporation of frailty indices and functional status measures

Practical Implementation

For optimal use of the KBB system:

1. Calculate the risk score preoperatively using validated calculators
2. Discuss results with the patient as part of informed consent
3. Use the score to guide perioperative management decisions
4. Compare risk-adjusted outcomes as part of quality improvement initiatives

Conclusion

The KBB system remains an important tool in cardiac surgery for risk stratification, allowing surgeons to better predict outcomes and tailor perioperative management strategies to individual patient risk profiles.