PhD defence R.A. (Ricardo) Castro Lopez

Below is a brief summary of the dissertation: 

Managing severe infections that lead to life-threatening low blood pressure (septic shock) requires careful balance in fluid treatment. Doctors must give enough fluids to support vital organs while preventing dangerous fluid buildup in the body. This research examines the best ways to manage fluids during both the initial treatment phase and the recovery phase.

In the early stages of treatment, quick recognition and action are essential. While doctors traditionally relied on blood pressure measurements and blood tests to guide treatment, new research shows that checking how quickly blood returns to the skin after pressing it (called capillary refill time) may be a better way to guide fluid treatment. Using this method has helped more patients survive and recover faster from organ problems. During this critical period, the infection causes blood vessels to become leaky, allowing fluid to escape into surrounding tissues. Since doctors cannot accurately assess this fluid leakage by physical examination alone, this research explores better ways to measure it.

Once the patient stabilizes, removing excess fluid becomes important. This is particularly crucial for patients on breathing machines, as too much fluid can make it harder to breathe independently. By carefully monitoring how well the patient's body responds to fluid removal, and how it affects their heart function, doctors can make better decisions about fluid management, leading to better recovery.

This research emphasizes that each patient needs personalized monitoring and treatment plans, considering both immediate needs and long-term effects on their heart, lungs, and other organs. It provides a scientific approach to managing fluids in patients with septic shock, aiming to improve their chances of recovery.

Septic shock management requires a delicate balance between adequate resuscitation and preventing fluid overload, with distinct phases requiring different therapeutic approaches and monitoring strategies. This thesis explores the critical endpoints for both the resuscitation and de-resuscitation phases of septic shock management.

In the initial resuscitation phase, early recognition and intervention are paramount. While traditional endpoints such as mean arterial pressure and lactate clearance have guided therapy, emerging evidence suggests that capillary refill time (CRT) serves as a superior resuscitation marker. Pursuing CRT-guided resuscitation has demonstrated improved outcomes, including reduced mortality rates and faster resolution of organ dysfunction. During this phase, septic shock-induced hyperpermeability leads to significant fluid leakage, a phenomenon that clinical examination alone fails to assess adequately. More objective methods to evaluate fluid transudation are discussed in this thesis.

The subsequent de-resuscitation phase, which focuses on removing excess fluid, becomes crucial once the acute shock period stabilizes. A key consideration during this period is the successful weaning from mechanical ventilation, which depends on achieving optimal balance between cardiac loading conditions and function. The implementation of physiology-based endpoints, remarkably fluid responsiveness, enables a more rational approach to fluid management and has been associated with improved patient outcomes.

The thesis emphasizes that monitoring strategies must be tailored to individual patient needs, with careful consideration of both immediate and long-term consequences, especially regarding cardiopulmonary interactions and organ dysfunction. This work presents a physiology-driven framework for fluid therapy in septic shock.