SU1.1-3 | Metabolic Response and Surgical Homeostasis — Assignment

CLINICAL SCENARIO

A 34-year-old previously healthy man is brought to the emergency department two hours after a high-speed motorcycle crash. He has a closed fracture of the right femoral shaft and a grade III splenic laceration managed non-operatively at first but now requiring emergency splenectomy. On arrival he is cool and clammy, drowsy but rousable, with a heart rate of 122/min, a blood pressure of 108/86 mmHg (narrowed pulse pressure) and a urine output that has fallen to 15 mL/h. Over the next five days he is resuscitated, taken to theatre, and recovers in the surgical high-dependency unit, where he becomes warm, vasodilated and persistently catabolic before slowly turning the corner.

Describe the metabolic and physiological state you would expect in this patient in the first hours after injury. Explain, using Cuthbertson's model, why he is cool, drowsy, tachycardic and oliguric with a near-normal systolic pressure but a narrowed pulse pressure. Identify the neuroendocrine mediators (catecholamines, cortisol, glucagon, ADH, aldosterone) responsible and state what each is doing to defend his circulation.

Explain why, once resuscitated, he becomes warm, vasodilated and hypermetabolic with a high cardiac output. Distinguish the catabolic component (negative nitrogen balance, muscle protein breakdown, post-injury hyperglycaemia — 'the diabetes of injury') from the later anabolic component. Name the principal mediators of the catabolic flow phase and the inflammatory cytokines involved.

Identify at least four factors that could amplify or prolong this man's metabolic response (for example the magnitude of tissue injury, sepsis, hypothermia, uncontrolled pain, hypovolaemia, pre-existing nutritional state). For each, state the specific perioperative action you would take to attenuate it.

Map his care onto the preoperative, intraoperative and postoperative phases. Address preoperative assessment and risk (assign and justify an ASA grade given the emergency context), the role and three steps of the WHO Surgical Safety Checklist around his splenectomy, and the postoperative measures (analgesia, normothermia, euvolaemia, nutrition, early mobilisation) that blunt the stress response. Reference ERAS principles where they apply to emergency surgery.

In a short closing paragraph, explain in your own words why an understanding of the metabolic response to injury changes how you would interpret his observations day to day — in particular why a single 'normal' blood pressure was not reassurance, and how good perioperative care is, in effect, an attempt to control the stress response.