Ep 39 - Prof. Tim Harris on Shock Assessment (LTC 2014)

At the recent London Trauma Conference, Iain Beardsell from the St Emlyn's podcast interviewed Professor Tim Harris, an expert in Emergency Medicine at Bart's Health, who provided critical insights into the concept of shock. This discussion challenged traditional notions and emphasized the importance of understanding shock beyond simple metrics like blood pressure.

Redefining Shock: Beyond Blood Pressure

Professor Harris argued that shock should not be narrowly defined as a state of low blood pressure but rather as a condition of inadequate oxygen delivery to meet the body's needs. Traditional medical training often emphasizes measurable parameters such as pulse, blood pressure, and respiratory rate. However, these indicators do not fully capture a patient's physiological state, particularly the crucial aspect of cardiac output—the volume of blood the heart pumps per minute. Cardiac output is difficult to measure directly, especially in emergency settings, yet it is a vital determinant of whether a patient is experiencing shock.

Relying solely on blood pressure can be misleading. For instance, young, healthy individuals might maintain a systolic pressure of 80-90 mmHg while adequately perfusing their organs, whereas older patients with normally high blood pressure may experience organ dysfunction even with moderate drops in pressure. Therefore, a comprehensive assessment of shock must consider more than just blood pressure readings.

The Importance of Cardiac Output and Oxygen Delivery

A significant portion of the interview focused on the role of cardiac output and oxygen delivery. The body's oxygen needs vary based on physiological stressors such as physical activity or trauma. In trauma situations, patients often face substantial physiological stress, akin to "running for the bus," which increases their oxygen requirements. However, emergency assessments frequently emphasize visible signs like pulse and blood pressure, neglecting the more critical issue of oxygen delivery.

The traditional approach, which targets a specific blood pressure (often 90 mmHg systolic) as the threshold for shock, fails to account for individual differences in physiological response. For example, hypertensive patients with a baseline blood pressure of 200 mmHg may enter shock if their pressure drops to 120 mmHg. Conversely, young and fit individuals may tolerate much lower pressures without exhibiting shock symptoms.

Practical Implications for Trauma Care

In clinical practice, especially in trauma care, these insights necessitate a broader approach to patient assessment and management. Professor Harris emphasized the need to consider the mechanism of injury and other contextual factors in addition to traditional clinical signs. Understanding the energy transfer involved in an incident, such as a motorbike accident, can provide crucial information about potential internal injuries and blood loss.

Professor Harris advocates for a comprehensive approach that includes assessing the mechanism of injury, physiological responses, and potential complications. This method helps in making informed decisions about subsequent actions, such as whether a patient should go for a CT scan or directly to surgery. One key concept he highlighted was hemostatic resuscitation. In cases of major trauma, the priority may not always be to restore normal organ perfusion immediately but to maintain sufficient blood volume and prevent further deterioration. This approach often involves the use of blood products like fresh frozen plasma (FFP) and packed red cells, guided by a massive transfusion protocol.

Challenges and Considerations in Clinical Practice

Professor Harris also discussed the challenges of strictly adhering to guidelines. While guidelines provide valuable frameworks, they may not always apply perfectly to individual patient scenarios. The Advanced Trauma Life Support (ATLS) classification of shock into stages based on blood loss and physiological parameters often does not reflect real-world patient presentations. Factors such as medications, past medical history, pain, and anxiety can significantly alter a patient's physiological response to trauma.

This discrepancy underscores the importance of clinical judgment and experience in trauma care. Professor Harris emphasized that guidelines should be seen as tools to aid decision-making rather than rigid rules. Medical professionals must adapt these guidelines to the specific circumstances of each patient, taking into account their age, comorbidities, and overall clinical picture.

The Art and Science of Medicine

The conversation concluded with a reflection on the balance between the art and science of medicine. While evidence-based guidelines are essential, the true skill lies in applying these principles to individual patients. This requires a deep understanding of human physiology, extensive clinical experience, and the ability to think critically in high-pressure situations.

Professor Harris stressed the importance of continuous learning and professional development in mastering the complexities of trauma care. The more we learn about shock and trauma, the more we understand that simplistic models are insufficient. A holistic approach, considering the entire patient and their context, is crucial for effective care.

Key Takeaways

1. Redefining Shock: Shock should be viewed as inadequate oxygen delivery rather than just low blood pressure.
2. Cardiac Output and Oxygen Delivery: These are critical components of assessing shock, yet challenging to measure in real-time.
3. Beyond Blood Pressure: Clinicians must consider the whole patient, including the mechanism of injury and physiological responses, rather than relying solely on blood pressure.
4. Hemostatic Resuscitation: In major trauma, the focus may shift to maintaining blood volume and managing coagulopathy.
5. Guidelines as Aids: While guidelines are useful, they should be adapted based on clinical judgment and the specific patient scenario.
6. The Art of Medicine: The practice of medicine involves applying scientific knowledge with a nuanced understanding of each unique clinical situation.

Professor Tim Harris's insights challenge traditional approaches to shock and highlight the importance of a comprehensive, patient-centered approach in trauma care. This nuanced understanding of shock and trauma management is essential for improving patient outcomes and advancing the field of emergency medicine.