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

CLINICAL SETTING

Mrs L is a 68-year-old woman with type 2 diabetes (on metformin), hypertension and a 30-pack-year smoking history, admitted for an elective open right hemicolectomy for a caecal carcinoma. She is independent but becomes breathless climbing two flights of stairs. Her surgery is scheduled for a Monday morning list. The team must take her safely from the decision to operate, through theatre, to recovery — anticipating and attenuating the metabolic stress that the operation will provoke.

Trigger 1: The preoperative clinic

In the preoperative assessment clinic two weeks before surgery, Mrs L's HbA1c is at the upper acceptable limit, her blood pressure is controlled on two agents, and she can manage two flights of stairs slowly. The nurse asks you to document her ASA grade and to plan her optimisation and fasting instructions. Mrs L asks whether she should 'stop eating and drinking from midnight the night before, like last time'.

DISCUSSION POINTS

  • What ASA physical status grade would you assign Mrs L, and what is your reasoning?
  • What preoperative optimisation would you consider for her diabetes, blood pressure, smoking and functional capacity?
  • What fasting instructions are correct for a morning list, and why is the old 'nil by mouth from midnight' advice now discouraged?
Click to reveal Trigger 2: In theatre and the first hours after (discuss previous trigger first!)

Trigger 2: In theatre and the first hours after

On the day of surgery the team performs the WHO Surgical Safety Checklist. During the operation she loses an estimated 600 mL of blood and the procedure lasts three hours. In recovery she is cool peripherally, with a heart rate of 104/min, a blood pressure of 118/82 mmHg and a urine output of 20 mL/h. The recovery nurse is reassured by the 'normal' blood pressure.

DISCUSSION POINTS

  • Identify the three formal pauses of the WHO Surgical Safety Checklist and what is confirmed at each.
  • How would you interpret her recovery-room observations in terms of the ebb phase and compensated hypovolaemia? Is the 'normal' blood pressure reassuring?
  • Which neuroendocrine mediators are defending her circulation at this point, and what are they doing?
Click to reveal Trigger 3: Day three on the surgical ward (discuss previous trigger first!)

Trigger 3: Day three on the surgical ward

By the third postoperative day Mrs L is warm and well perfused but her blood glucose is persistently raised at 12-14 mmol/L despite her usual metformin being withheld, she has lost appetite, and the dietitian notes she is in negative nitrogen balance. She is reluctant to get out of bed because of pain.

DISCUSSION POINTS

  • Explain her hyperglycaemia and negative nitrogen balance in terms of the flow phase and its mediators.
  • What specific measures (analgesia, mobilisation, nutrition, glycaemic control) would attenuate her catabolic response, and which ERAS principles do they reflect?
  • What factors in Mrs L's case might amplify or prolong her metabolic response, and how would you address each?

Group Task Assignments

  • Group A: Build a one-page preoperative optimisation and risk-assessment plan for Mrs L, including ASA grading rationale and fasting instructions for a morning list.
  • Group B: Produce an annotated timeline of Mrs L's metabolic response from incision to day five, labelling the ebb and flow phases and their mediators against her observations.
  • Group C: Draft an ERAS-aligned postoperative bundle for Mrs L and justify how each element attenuates the surgical stress response.

Learning Issues

Research these questions and bring your findings to the discussion.

  1. [SU1.1] What are the phases of the metabolic response to injury (ebb and flow) and which neuroendocrine and inflammatory mediators drive each?
  2. [SU1.2] Which factors modify the magnitude and duration of the metabolic response to injury, and how can each be influenced perioperatively?
  3. [SU1.3] What are the principles of perioperative care, including ASA grading, the WHO Surgical Safety Checklist, fasting guidance and ERAS, and how do they reduce the stress of surgery?