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SU1.1-3 | Metabolic Response and Surgical Homeostasis — Graded Quiz
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Five days after a severe burn, a patient who is being adequately resuscitated is now warm and vasodilated with a high cardiac output, a raised resting energy expenditure, and laboratory evidence of net muscle protein breakdown with a negative nitrogen balance. Which phase of the metabolic response to injury does this picture represent?
Correct. Hypermetabolism, raised energy expenditure, net protein catabolism and negative nitrogen balance in a warm, well-perfused, high-output patient define the catabolic component of the flow phase. The anabolic component, with restoration of stores and positive nitrogen balance, comes later.
Flow phase: an early catabolic component (hypermetabolism, protein breakdown, negative nitrogen balance) precedes a later anabolic component (restoration of stores).
Hypermetabolism with net protein breakdown and negative nitrogen balance is the catabolic flow phase. The ebb phase is hypometabolic and cool; the anabolic flow phase restores stores with positive nitrogen balance.
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Which single statement BEST captures why understanding the metabolic response to injury matters at the bedside in the early phase of major trauma?
Correct. In early compensated shock, intense catecholamine-driven vasoconstriction and tachycardia defend the blood pressure even as perfusion fails. A single 'normal' BP is therefore falsely reassuring; the trajectory (rising heart rate, falling urine output, rising lactate) is what reveals the failing circulation.
Catecholamine-driven compensation can maintain a normal blood pressure in early shock; read the trajectory (heart rate, urine output, lactate), not a single snapshot.
The key bedside lesson is that the neuroendocrine response can hold the blood pressure normal in early (compensated) shock while perfusion is already failing — so a single normal BP is not reassurance. The response causes hyperglycaemia, not hypoglycaemia, and does not remove the need for resuscitation.
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Which set of perioperative measures is MOST likely to ATTENUATE the magnitude of the metabolic response to a major elective operation?
Correct. The afferent triggers of the response include pain, cold, hypovolaemia and sepsis. Blunting them — good analgesia, active warming, avoiding hypovolaemia and controlling infection — reduces the size and duration of the catabolic response. These are core ERAS principles.
Attenuate the metabolic response by minimising its afferent triggers — pain, cold, hypovolaemia and sepsis — the foundation of ERAS.
Attenuate the response by removing its triggers: treat pain, keep the patient warm, avoid hypovolaemia and control sepsis early. Cold, prolonged fasting and untreated pain amplify it; routine steroids and deliberate hypothermia are not used for this.
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During the WHO Surgical Safety Checklist, the entire team pauses immediately before the skin incision to verbally confirm the correct patient, the correct procedure and the correct site. Which formal step of the checklist is this?
Correct. The Time-Out is the team pause immediately before skin incision, confirming patient, procedure and site (and other safety items). Sign-In occurs before induction; Sign-Out occurs before the patient leaves theatre.
WHO Surgical Safety Checklist has three pauses: Sign-In (before induction), Time-Out (before incision), Sign-Out (before leaving theatre).
The pre-incision team pause confirming patient/procedure/site is the Time-Out. Sign-In is before induction of anaesthesia; Sign-Out is before the patient leaves theatre.
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An Enhanced Recovery After Surgery (ERAS) pathway aims to reduce the surgical stress response and speed recovery. Which intervention is consistent with ERAS principles?
Correct. ERAS bundles minimise the stress response and accelerate recovery: avoid prolonged fasting (clear-fluid carbohydrate loading to 2 h), use multimodal opioid-sparing analgesia, maintain normothermia and euvolaemia, and mobilise and feed early. Prolonged fasting, bed rest and fluid excess all work against recovery.
ERAS attenuates the surgical stress response: no prolonged fasting (carbohydrate loading to 2 h), multimodal opioid-sparing analgesia, normovolaemia, early mobilisation and feeding.
ERAS avoids prolonged fasting and bed rest. Its hallmarks are carbohydrate loading to 2 h, multimodal opioid-sparing analgesia, goal-directed (not excessive) fluids, early mobilisation and early feeding.
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Which statement BEST describes the role of pro-inflammatory cytokines (such as IL-1, IL-6 and TNF-alpha) in the metabolic response to major injury?
Correct. The inflammatory (cytokine) arm — IL-1, IL-6, TNF-alpha and others released from injured tissue and immune cells — drives the acute-phase protein response, fever and components of catabolism, working in concert with the neuroendocrine arm to produce the integrated response to injury.
The injury response has two interacting arms: a neuroendocrine arm (cortisol, catecholamines, glucagon, ADH, aldosterone) and an inflammatory cytokine arm (IL-1, IL-6, TNF-alpha) driving the acute-phase response.
Cytokines (IL-1, IL-6, TNF-alpha) are released early from damaged tissue and immune cells and drive the acute-phase response, fever and catabolism alongside the neuroendocrine hormones. They do not replace ADH, and they amplify rather than suppress metabolism.
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