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 param