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IM23.1-12,IM24.1-5 | Mineral Fluid Electrolyte Acid Base and Nutrition — Assignment

CLINICAL SCENARIO

This assignment presents a composite clinical scenario involving a hospitalised adult patient with concurrent acid-base disturbance, electrolyte abnormalities, and nutritional compromise — as commonly encountered in internal medicine wards in India. You will systematically analyse an arterial blood gas, interpret electrolyte data using a structured diagnostic algorithm, construct a safe management plan respecting correction-rate limits, and formulate a nutritional support plan addressing the risk of refeeding syndrome. The exercise integrates the major domains of this module into a realistic clinical reasoning task aligned with final-year MBBS practice.

Instructions

Work through each section in order. Show all calculations explicitly — write out the formula and the numbers you substituted. For management plans, use numbered steps. Do not use bullet points in Sections 1 and 2 — write in full clinical prose. Word limit: 1,100–1,500 words total across all sections. Do not copy SDL text verbatim — synthesise and apply.

Length: 1,100–1,500 words across all five sections

What to Submit

Section 1: Arterial Blood Gas Interpretation

Guidance: You are given the following ABG result from a 45-year-old man admitted with a 3-day history of profuse diarrhoea, vomiting, and poor oral intake: pH 7.26, PaCO2 28 mmHg, HCO3 12 mmol/L, Na 138 mmol/L, K 2.8 mmol/L, Cl 116 mmol/L. Apply the six-step ABG interpretation framework: (1) Is there an acidosis or alkalosis? (2) Is it metabolic or respiratory (identify the primary disorder)? (3) Is there appropriate compensation — apply the correct formula? (4) Calculate the anion gap. (5) If anion gap is elevated, apply Winter's formula and delta-delta ratio. (6) Is there a mixed disorder? State your final acid-base diagnosis clearly. Approximately 300 words.

Section 2: Electrolyte Diagnosis and Mechanism

Guidance: Using the same patient: on examination he is clinically hypovolaemic (dry mucosa, reduced skin turgor, postural hypotension). Serum potassium is 2.8 mmol/L. ECG shows flattened T waves and prominent U waves. Serum sodium is 129 mmol/L. Urine sodium is 8 mmol/L. (a) Apply the hyponatraemia diagnostic algorithm (serum osmolality → volume status → urine sodium) and state the category and most likely cause of his hyponatraemia. Explain the mechanism. (b) Classify his hypokalaemia by the ECG changes. Explain how diarrhoea produces both hypokalaemia and the acid-base disorder identified in Section 1. Approximately 300 words.

Section 3: Management Plan

Guidance: Construct a prioritised, step-by-step management plan for this patient covering: (a) immediate resuscitation — which IV fluid and why; (b) correction of hyponatraemia — state the target rate of correction (mmol/L per 24 hours), the fluid choice, and when to reassess; (c) potassium replacement — state route, rate, monitoring, and the co-electrolyte that must also be checked; (d) acid-base management — does the metabolic acidosis require bicarbonate? Justify your answer. For each intervention, state at least one monitoring parameter and the frequency of reassessment. Approximately 350 words.

Section 4: Nutritional Assessment and Support

Guidance: The same patient is found to have been homeless and malnourished for the past 3 months. BMI is 15.8 kg/m2. He appears cachectic with prominent ribs. Serum albumin is 22 g/L. His diarrhoea has settled after 48 hours of IV fluids and antibiotics. (a) Apply the ABCD nutritional assessment framework to this patient and classify the type and severity of malnutrition. (b) Calculate his estimated daily caloric requirement (use 25–30 kcal/kg/day with actual body weight). (c) Is he at risk of refeeding syndrome? List three specific preventive measures, including starting caloric rate, electrolyte supplementation, and vitamin supplementation. (d) What route of nutritional support is most appropriate, and why? Approximately 300 words.

Section 5: Integration and Clinical Synthesis

Guidance: In a brief concluding paragraph (100–150 words), explain how the acid-base disorder, electrolyte disturbances, and malnutrition in this patient interact with one another — for example, how hypokalaemia and hyponatraemia both relate to the same underlying problem, and how refeeding syndrome risk is related to the metabolic state. Demonstrate that you understand this patient as a whole, not as a collection of isolated abnormalities.

Grading Rubric — Fluid, Electrolyte, Acid-Base, and Nutrition Case Analysis Rubric

Criterion	Points	Full-marks descriptor
ABG Interpretation and Acid-Base Reasoning (Section 1): Applies a systematic six-step framework; correctly identifies primary disorder, calculates expected compensation using the correct formula, detects any concurrent disorder, and calculates anion gap with delta-delta where indicated.	25 pts	Six-step framework applied completely and correctly; appropriate formula used for compensation check; anion gap and delta-delta ratio calculated with correct interpretation; concurrent disorder identified or correctly excluded; Winter's formula applied where relevant.
Electrolyte Diagnosis and Mechanism (Section 2): Correctly diagnoses the electrolyte disorder from clinical and laboratory data; explains the pathophysiological mechanism; identifies the causative category using the appropriate diagnostic algorithm (e.g., volume status and urine sodium for hyponatraemia; ECG changes for hyperkalaemia).	25 pts	Correct diagnosis with full mechanistic explanation; appropriate diagnostic algorithm applied step-by-step; correct category identified (e.g., SIADH vs hypothyroidism vs adrenal insufficiency); ECG changes or clinical signs correctly interpreted where present.
Management Plan (Section 3): Constructs a safe, evidence-based, step-by-step management plan for both the acid-base and electrolyte disorder; correctly applies correction-rate limits; states the correct sequence (e.g., cardiac membrane stabilisation before shifting in hyperkalaemia; correction-rate limit in hyponatraemia); identifies monitoring parameters.	25 pts	Correct management sequence with explicit step-by-step plan; correction-rate limits stated correctly (e.g., Na correction ≤8–10 mmol/L/24h; K IV rate ≤20 mmol/hr peripherally); rationale for each intervention given; monitoring plan (electrolytes, ECG, GCS) specified.
Nutritional Assessment and Support (Section 4): Applies the ABCD nutritional assessment framework; correctly identifies the type and severity of malnutrition; proposes a safe, appropriate nutritional support plan; addresses refeeding syndrome risk if relevant; justifies enteral vs parenteral choice.	20 pts	ABCD framework applied to the case; severity and type of malnutrition identified; appropriate route (EN vs PN) justified; refeeding syndrome risk addressed with specific preventive steps (starting rate, phosphate/thiamine supplementation) if applicable; monitoring plan for nutritional response stated.
Clinical Reasoning Integration and Written Quality (Section 5): Integrates acid-base, electrolyte, and nutritional findings into a coherent clinical synthesis; identifies how the disorders interact; uses precise clinical language; work is correctly cited (where relevant) and stays within word limit.	5 pts	Disorders integrated into a clinical narrative — the interaction between acid-base and electrolyte findings is explicitly discussed; language is precise and professional; within word limit.

PEER REVIEW

Review your peer's assignment using the rubric. For Section 1, verify that the correct compensation formula was applied (Winter's for metabolic acidosis) and that the anion gap was calculated correctly. For Section 2, check that the hyponatraemia algorithm was applied in the correct sequence (osmolality → volume status → urine sodium) and that the STUDENT correctly classified this as hypovolaemic hyponatraemia, not SIADH. For Section 3, confirm that a sodium correction-rate limit was stated explicitly. For Section 4, check that the starting caloric rate for refeeding-risk patients is correctly stated as approximately 10 kcal/kg/day, not the maintenance target. Write one specific comment per section explaining your score — do not copy the rubric descriptor. Complete the review within 72 hours.