Figure Refeeding syndrome — the fatal metabolic shift when food returns to the starved. The carbohydrate drives the insulin surge; the phosphate, the potassium and the magnesium plunge into the cells; the thiamine depletes; the fluid retains. Hypophosphataemia brings the respiratory failure and the cardiomyopathy, hypokalaemia the arrhythmia. Give thiamine, replace the electrolytes, start the feed low (10–15 kcal/kg/day) and titrate up, and watch the heart. Refeeding syndrome (RFS) = metabolic derangements (hypophosphataemia, hypokalaemia, hypomagnesaemia, thiamine deficiency) when food is reintroduced to starved patients. MECHANISM: carbohydrate → insulin surge → electrolytes shift INTO cells → serum plummets → respiratory failure, arrhythmia, death. PREVENTION (key): identify high-risk (anorexia, alcoholism, fasting >5 days), start nutrition SLOWLY (10-15 kcal/kg/day — NICE, WATERFALL trial), give THIAMINE before feeding, supplement phosphate/K/Mg, monitor daily. MANAGEMENT : slow/stop nutrition, aggressive electrolyte replacement, thiamine. Mortality high if unrecognised.
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Exam practice
SAQ — Established refeeding syndrome in oncology cachexia 10 minutes · 10 marks
Reveal all A 67-year-old man with metastatic oesophageal cancer and three weeks of minimal oral intake is commenced on full-rate NG feed for malnutrition. On day 3 he becomes dyspnoeic and confused, with sinus tachycardia and new QT prolongation. Phosphate 0.26 mmol/L (baseline 0.82), K+ 2.6, Mg 0.45, corrected Ca 1.95, glucose 12.
a Outline your immediate management of this established refeeding emergency.
b Distinguish refeeding syndrome from tumour lysis syndrome here, and explain why the distinction matters.
c Describe how you would restart nutrition once he is stabilised.
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SAQ — NICE refeeding risk stratification and the falling phosphate 10 minutes · 10 marks
Reveal all A 44-year-old woman with alcohol use disorder (BMI 16.4, unintentional weight loss 12% over four months, negligible intake for 11 days) is admitted with withdrawal seizures. Baseline phosphate 0.70, K+ 3.6, Mg 0.66. Enteral nutrition is planned.
a Using NICE CG32 criteria, classify her refeeding risk tier and justify your initial energy prescription and escalation plan.
b Detail the prophylactic measures and monitoring schedule you would institute before and during the first feed.
c On day 2 her phosphate is 0.48 mmol/L (from 0.70) with no symptoms. How do you interpret this and what is your response?
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Clinical pearls
High-yield refeeding syndrome points for CICM/FFICM exam
Pathophysiology — insulin surge is the trigger. (1) STARVATION: (a) Body switches to FAT + PROTEIN catabolism (ketogenesis) for energy (glucose depleted). (b) INSULIN LOW (no carbohydrate stimulus). (c) INTRACELLULAR electrolytes DEPLETED (phosphate, potassium, magnesium — used in catabolism, not replenished) — but SERUM may be NORMAL (stores low, not yet showing). (2) REFEEDING (carbohydrate): (a) Carbohydrate -> GLUCOSE -> INSULIN SURGE (sudden, high). (b) Insulin stimulates cellular UPTAKE of glucose + ELECTROLYTES: (i) Phosphate -> into cells (for ATP synthesis from glucose — glycolysis needs phosphate). (ii) Potassium -> into cells (insulin activates Na-K pump). (iii) Magnesium -> into cells. (c) Result: serum phosphate/potassium/magnesium PLUMMET (from normal to severely low within hours-days). (d) ALSO: insulin causes sodium + water retention (antinatriuresis) -> fluid overload. (3) THIS IS WHY RFS HAPPENS: the starved body can't handle the sudden carbohydrate/insulin -> massive intracellular shift -> dangerous low serum levels.[5] }Hypophosphataemia — the hallmark. (1) Phosphate is ESSENTIAL for: (a) ATP (energy — every cell). (b) 2,3-DPG (oxygen release from haemoglobin). (c) Cell membrane function. (d) Leukocyte function. (e) Nerve conduction. (2) In RFS: insulin -> phosphate shifts into cells (for glycolysis/ATP) -> serum phosphate DROPS (often <0.3 mmol/L — severe). (3) CLINICAL of severe hypophosphataemia: (a) RESPIRATORY FAILURE: diaphragm weakness (can't generate ATP for muscle contraction) -> hypercapnic respiratory failure -> may need ventilation. (b) CARDIAC: decreased contractility (ATP depleted) -> heart failure, arrhythmia. (c) HAEMOLYSIS (RBC membrane instability). (d) LEUKOCYTE dysfunction (impaired phagocytosis -> infection). (e) RHABDOMYOLYSIS (muscle breakdown). (f) CENTRAL NERVOUS: confusion, seizures, coma. (4) THIS IS WHY PHOSPHATE IS THE KEY MARKER of RFS — monitor it.[1] }Thiamine deficiency — Wernicke risk. (1) THIAMINE (vitamin B1): cofactor for: (a) Pyruvate dehydrogenase (glycolysis -> Krebs cycle). (b) Transketolase (pentose phosphate pathway). (2) In STARVATION: thiamine DEPLETED (poor intake). (3) REFEEDING (carbohydrate): sudden demand for thiamine (glycolysis needs it) -> thiamine further depleted -> WERNICKE ENCEPHALOPATHY (acute): (a) Triad: ataxia (wide-based gait), ophthalmoplegia (nystagmus, lateral rectus palsy), confusion. (b) If untreated -> KORSAKOFF (permanent memory impairment). (c) WET BERIBERI: heart failure (high-output — vasodilation). (4) PREVENTION: give THIAMINE BEFORE feeding (200-300 mg PO/IV) — before the carbohydrate load -> prevents Wernicke. (5) TREATMENT: thiamine 300-500 mg IV (if Wernicke suspected). (6) ALSO: give BEFORE glucose (in alcoholic presenting with hypoglycaemia — glucose without thiamine precipitates Wernicke).[4] }NICE criteria — high-risk identification. (1) VERY HIGH RISK (start at 5-10 kcal/kg/day): (a) BMI <14. (b) Little/no intake for >15 days. (c) Pre-existing low phosphate/potassium/magnesium. (d) AND any of: alcoholism, chemotherapy, insulin/diuretics. (2) HIGH RISK (start at 10-15 kcal/kg/day): (a) BMI <16. (b) Unintentional weight loss >15% in 3-6 months. (c) Little/no intake for >10 days. (d) History of alcohol/drug misuse. (3) MODERATE RISK (start at 15-20 kcal/kg/day): (a) BMI <18.5. (b) Weight loss >10% in 3-6 months. (c) Little/no intake >5 days. (4) LOW RISK (normal start): normal BMI, good intake. (5) CLINICAL: use criteria to GUIDE initial feeding rate (slower for higher risk). MONITOR all closely (even low-risk can develop RFS).[3] }WATERFALL trial — challenges NICE? (1) WATERFALL (2019, Lancet Respiratory): RCT comparing 'full' feeding (target calories from day 1) vs 'trophic' (low calories, increase gradually) in ICU patients at risk of refeeding. (2) RESULT: NO significant difference in REFEEDING HYPOPHOSPHATAEMIA between groups (both groups had similar phosphate drop). (3) INTERPRETATION: (a) CHALLENGES the NICE recommendation to feed SLOWLY (suggests full feeding doesn't worsen RFS). (b) BUT: study was in ICU patients (mixed — not all starved); refeeding defined by phosphate (not outcomes); not powered for mortality. (c) CURRENT CONSENSUS: still recommend SLOW start for HIGH-RISK (anorexia, severe starvation, BMI <16) — but may be less critical for general ICU (where feeding delay may worsen outcomes from undernutrition). (d) PRACTICE: most ICUs still start slowly in high-risk, but may feed more aggressively in lower-risk (where under-nutrition is the bigger concern).[2] }Fluid retention — cardiac failure. (1) In RFS: (a) Insulin -> sodium retention (antinatriuresis). (b) ADH secretion (stress response). (c) Refeeding fluid (enteral/parenteral nutrition contains water). (d) Cardiac atrophy (starved heart -> small, weak). (2) Result: FLUID OVERLOAD -> HEART FAILURE (especially in starved/atrophic heart that can't handle volume). (3) CLINICAL: (a) Pulmonary oedema (dyspnoea, crackles, CXR). (b) Peripheral oedema. (c) JVP raised. (4) MANAGEMENT: (a) FLUID RESTRICTION (don't over-hydrate during refeeding). (b) DIURESE (frusemide — if overload). (c) CARDIAC support (inotrope if severe heart failure). (5) PREVENTION: cautious fluid management, slow refeeding, monitor fluid balance + weight. (6) NOTE: 'refeeding oedema' can be benign (salt + water retention) — but if cardiac -> dangerous (atrophic heart).[5] }Respiratory failure — the dangerous consequence. (1) In RFS, severe HYPPOSPHATAEMIA -> diaphragm weakness (can't generate ATP for contraction) -> ventilatory failure. (2) ALSO: weakened respiratory muscles -> poor cough -> atelectasis/pneumonia. (3) CLINICAL: (a) Rising PaCO2 (hypercapnia — type 2 respiratory failure). (b) Falling vital capacity. (c) Hypoxaemia. (d) Need for ventilation (NIV or intubation). (4) TRIGGERS: any starved patient who develops respiratory failure within days of starting nutrition -> RFS (hypophosphataemia) until proven otherwise. (5) MANAGEMENT: (a) CORRECT phosphate (IV — aggressive). (b) Ventilatory support (NIV/intubation). (c) Slow nutrition (may need to pause). (d) Usually reversible with phosphate correction.[1] }Arrhythmia — from hypokalaemia/hypomagnesaemia. (1) In RFS: potassium + magnesium drop -> arrhythmia. (2) CLINICAL: (a) Atrial (AF, atrial tachycardia). (b) Ventricular (PVCs, VT, torsades — especially with hypomagnesaemia + prolonged QT). (c) Cardiac arrest (severe). (3) ALSO: cardiac failure (from hypophosphataemia — ATP depletion -> weak heart). (4) MONITOR: continuous ECG, serial K+/Mg2+/phosphate. (5) MANAGEMENT: (a) Correct K+ + Mg2+ (IV). (b) Antiarrhythmic (if needed — but primary is electrolyte correction). (c) CARDIAC ARREST: standard ACLS + aggressive electrolyte correction. (6) MORTALITY: arrhythmia is a leading cause of death in RFS (sudden cardiac death in severe hypokalaemia/hypomagnesaemia).[4] }Enteral vs parenteral nutrition — both can trigger RFS. (1) ENTERAL (oral, NG, PEG): (a) Preferred (maintains gut barrier, less infection, cheaper). (b) BUT: can still trigger RFS (carbohydrate -> insulin surge). (c) Start slowly (10-15 kcal/kg/day in high-risk). (2) PARENTERAL (TPN — total parenteral nutrition): (a) Used if gut not working (ileus, obstruction, short bowel). (b) HIGHER RFS risk (direct glucose load into bloodstream -> larger insulin surge). (c) Start VERY slowly (especially glucose component). (d) LIMIT glucose initially (use lipid for some calories — less insulin effect). (3) BOTH: monitor phosphate/potassium/magnesium, give thiamine, start slowly. (4) PRACTICE: enteral preferred; parenteral if gut failure; both need RFS precautions.[6] }Anorexia nervosa — the classic high-risk. (1) Anorexia: chronic starvation -> severely depleted phosphate/potassium/magnesium + thiamine + cardiac atrophy. (2) HIGH RISK of RFS when refeeding starts (even at low calorie rates). (3) MANAGEMENT (MARSIPAN guidelines — UK): (a) Start VERY slowly (5-10 kcal/kg/day) — even slower than general RFS. (b) Increase over 10+ days (not 5-7). (c) AGGRESSIVE monitoring (phosphate/potassium/magnesium daily + cardiac monitoring). (d) Thiamine, B vitamins. (e) PSYCHIATRIC: anorexia is psychiatric — coordinate with mental health. (f) REFEEDING in anorexia is dangerous — may need HDU/ICU. (4) MORTALITY: RFS in anorexia has significant mortality (cardiac arrest, arrhythmia) — prevention is critical.[4] }Alcoholism — multiple risks. (1) CHRONIC ALCOHOL: (a) Poor nutrition (thiamine, folate, B12 depleted). (b) Liver disease (impaired metabolism). (c) Electrolyte disturbances (low phosphate, potassium, magnesium — from poor intake + diuresis). (d) Cardiomyopathy (alcoholic). (2) REFEEDING (after admission for alcohol-related issue — withdrawal, pancreatitis, cirrhosis): (a) HIGH RFS risk (multiple depletions). (b) THIAMINE ESSENTIAL (prevent Wernicke — give before any glucose/feeding). (c) Slow feeding, aggressive electrolyte replacement. (3) PRESENTATION: (a) Wernicke (confusion, ataxia, ophthalmoplegia) if thiamine not given. (b) Arrhythmia (hypokalaemia/hypomagnesaemia). (c) Respiratory failure (hypophosphataemia). (4) ALWAYS: give thiamine to alcoholics BEFORE glucose/feeding (even if no RFS — standard alcohol withdrawal care).[4] }Protein — should NOT be restricted. (1) OLD recommendation: restrict PROTEIN initially in RFS (thought to contribute). (2) CURRENT: protein is SAFE (doesn't trigger insulin surge like carbohydrate). (3) ESPEN guidelines (2019): provide ADEQUATE protein from the start (1-1.5 g/kg/day) — do NOT restrict. (4) RATIONALE: (a) Protein is needed for repair (starvation -> muscle breakdown). (b) Restricting protein worsens malnutrition. (c) Protein doesn't cause the insulin surge (that's carbohydrate). (5) PRACTICE: give protein from day 1 (enteral formula or parenteral amino acids) — only limit CALORIES (carbohydrate/fat) initially.[6] }Duration of monitoring. (1) RFS typically occurs within 3-5 DAYS of starting nutrition (peak day 3-5). (2) MONITOR for at least 7-10 DAYS (high-risk). (3) DAILY: phosphate, potassium, magnesium (for first 5-7 days minimum). (4) Then EVERY OTHER DAY if stable. (5) Continue until nutrition at TARGET + electrolytes stable. (6) CARDIAC MONITORING: continuous ECG for high-risk (especially anorexia, elderly, cardiac history) until electrolytes stable. (7) Some patients need WEEKS of monitoring (severe starvation — slow refeeding). (8) RECURRENCE: if feeding increased too fast -> RFS may recur -> slow down again.[3] }RFS in ICU — common, under-recognised. (1) ICU patients often STARVED on admission (pre-admission poor intake, delayed nutrition, NBM for procedures). (2) When nutrition started -> RFS risk. (3) UNDER-RECOGNISED: (a) Phosphate often attributed to 'critical illness' (not RFS specifically). (b) Respiratory failure attributed to 'primary disease' (not RFS). (c) Arrhythmia attributed to 'cardiac disease' (not electrolyte). (4) AWARENESS: (a) Check pre-feeding phosphate/potassium/magnesium in ALL ICU patients starting nutrition. (b) Monitor daily for first week. (c) Consider RFS in ANY deterioration within 5 days of starting nutrition. (5) PREVENTION is KEY (slow start, thiamine, electrolyte supplementation) — better than treatment. (6) MULTIDISCIPLINARY: ICU + dietitian + pharmacist (nutrition + electrolyte management).[1] }Pathophysiology deep dive — the intracellular phosphate sink. (1) During starvation, intracellular phosphate is progressively consumed by ongoing basal metabolism (ATP turnover) without dietary replenishment, yet serum phosphate often stays normal because intracellular stores (~80% of body phosphorus) are vast relative to the small extracellular pool (~1%). (2) The refeeding glucose load drives a massive phosphorylation demand: glucose → glucose-6-phosphate (consumes 1 ATP-equivalent), then glycolysis, then oxidative phosphorylation to regenerate ATP — every step phosphorylates intermediates and pulls phosphate INTRACELLULARLY. (3) Glycolysis also needs inorganic phosphate at the glyceraldehyde-3-phosphate dehydrogenase step. (4) Net result: the intracellular compartment becomes a phosphate 'sink' and the small extracellular pool collapses within 12-72h — serum phosphate falls FIRST, before any symptom. (5) ATP depletion then disables every energy-dependent pump (Na/K-ATPase, Ca-ATPase) — diaphragm, myocardium, and skeletal muscle fail. This is why hypophosphataemia is the dominant AND earliest biochemical marker of RFS.[7] }2,3-DPG, oxygen dissociation, and the 'refeeder's tissue hypoxia'. (1) Phosphate is the rate-limiting substrate for 2,3-bisphosphoglycerate mutase in red cells; 2,3-DPG binds deoxyhaemoglobin and shifts the oxyhaemoglobin dissociation curve RIGHT (enhances O2 unloading to tissues). (2) In RFS, phosphate depletion → low 2,3-DPG → curve shifts LEFT → tissues extract LESS oxygen → functional tissue hypoxia even with adequate PaO2. (3) Clinical correlate: the starved patient who develops lactic acidosis, confusion, and 'septic-looking' perfusion within 48h of refeeding may have 2,3-DPG-depletion tissue hypoxia, not sepsis. (4) Treat by correcting PHOSPHATE, not by chasing oxygen delivery; the lactate and confusion resolve as phosphate rises.[7] }IV phosphate replacement — practical dosing. (1) Agents: sodium glycerophosphate (Na-GlyceroP) or potassium phosphate (K-Phos); each 10 mmol provides ~1.5-3 mmol of potassium or sodium depending on preparation — choose based on the potassium level (K-Phos if hypokalaemic, Na-GlyceroP if K+ normal/high). (2) Dosing by severity: moderate (PO4 0.30-0.64 mmol/L) → 0.16-0.32 mmol/kg (typically 15-20 mmol) over 4-6h; severe (<0.30 or symptomatic) → 0.32-0.64 mmol/kg (30-50 mmol) over 6-8h, max 30 mmol per single infusion bag. (3) Recheck PO4 2-4h after infusion ends; re-dose until >0.6 mmol/L. (4) Caution: rapid phosphate → HYPOcalcaemia (calcium-phosphate precipitation) + AKI — check Ca2+ and renal function; avoid in hypercalcaemia. (5) NEVER give phosphate as a fast IV push — arrhythmia / acute renal failure. (6) For ongoing losses, infuse a continuous maintenance IV phosphate 0.3-0.6 mmol/kg/24h PLUS oral supplementation once gut tolerates. (7) Total body deficit may be >500 mmol — expect DAYS of replacement.[1] }Thiamine — dose, route, timing. (1) Why BEFORE feed: pyruvate dehydrogenase (thiamine-dependent) is the obligate gateway for glycolytic carbons into the Krebs cycle. Giving glucose to a thiamine-deficient patient consumes the last thiamine reserve → acute Wernicke within hours. (2) Prophylactic dosing: thiamine 200-300 mg PO/IV daily, started 30-60 min BEFORE the first feed, continued for 5-10 days (longer if alcoholic or persistent deficiency). (3) If Wernicke suspected (confusion, ataxia, ophthalmoplegia/nystagmus, hypothermia/hypotension): treat as confirmed — thiamine 500 mg IV TDS for 3-5 days, then 250 mg IV/PO daily. (4) Also give parenteral B-complex (riboflavin, niacin, pyridoxine) — other B vitamins are co-depleted and become rate-limiting once thiamine is replaced. (5) Safety: thiamine is water-soluble, exceptionally safe even at high doses (rare anaphylaxis with IV — give over 15-30 min). (6) ALWAYS give thiamine BEFORE any glucose — including D5W, parenteral nutrition, or dextrose for hypoglycaemia. The classic exam trap: 'IV dextrose given before thiamine precipitates Wernicke'.[7] }Cardiac monitoring in refeeding — QTc and the atrophic heart. (1) Starvation causes CARDIAC ATROPHY (loss of myocardial mass, reduced chamber size) and bradycardia with prolonged QT — the same substrate that drives sudden death in anorexia. (2) On refeeding, hypokalaemia + hypomagnesaemia + hypocalcaemia further prolong QTc → torsades-de-pointes risk. (3) WET beriberi (thiamine deficiency) presents as high-output heart failure: tachycardia, wide pulse pressure, bounding pulses, bilateral oedema. (4) DRY beriberi: peripheral neuropathy + cardiomyopathy with low-output failure. (5) Monitoring minimum: 12-lead ECG at baseline, daily rhythm strip, continuous telemetry for very-high-risk (BMI <14, anorexia, prolonged QTc). (6) Treat QTc >500 ms or new arrhythmia: STOP feed, correct K+ to >4.5, Mg2+ to >1.0, Ca2+ to normal; IV MgSO4 2 g for torsades; AVOID QT-prolonging drugs (haloperidol, macrolides, fluoroquinolones, ondansetron — all commonly used in ICU). (7) 'Refeeding oedema' ≠ heart failure — assess with JVP, lung bases, and POCUS/BNP before diuresing a hypovolaemic starved patient.[4] }Glucose control during refeeding — both directions are dangerous. (1) STARVATION → insulin resistance + depleted glycogen → first feed may cause HYPERglycaemia (relative insulin deficiency + resistance). (2) Then the insulin SURGE can overshoot → HYPOglycaemia 2-6h post-feed. (3) Hyperglycaemia: osmotic diuresis (worsens K/Mg losses), infection risk, oxidative stress. Target glucose 6-10 mmol/L — avoid insulin infusion unless >10-12 and persistent, because insulin drives further phosphate INTO cells and worsens RFS. (4) Hypoglycaemia: give 50 mL of 50% dextrose — but give THIAMINE first (the Wernicke trap, pearl 18). (5) Practical rule: avoid IV dextrose in starved patients unless treating documented hypoglycaemia; favour enteral feed as the glucose source (slower absorption, gentler insulin response).[10] }RFS in special populations — elderly, oncology, post-bariatric, post-operative, hyperemesis. (1) ELDERLY: reduced lean mass, low baseline phosphate/Mg, polypharmacy (diuretics, PPIs), delirium — easily missed RFS; start at 10-15 kcal/kg/day after any >5-day poor intake. (2) ONCOLOGY/CACHEXIA: pro-inflammatory cytokines (TNF, IL-6) accelerate muscle and phosphate loss; chemotherapy adds nausea/vomiting; tumour lysis also lowers phosphate and Ca — DISTINGUISH RFS from tumour lysis (the latter has HIGH K, HIGH PO4, HIGH urate, LOW Ca; RFS has LOW PO4, LOW K, LOW Mg). (3) POST-BARIATRIC: rapid weight loss + malabsorption + vomiting → severely depleted; refeed very slowly even if BMI is now 'normal'. (4) POST-OPERATIVE/PROLONGED NBM: 7-10 days post-op with ileus or NBM after surgery is a classic MISSED RFS — restart cautiously, not at full target. (5) PREGNANCY/HYPEREMESIS GRAVIDARUM: prolonged vomiting → thiamine + electrolyte depletion; refeeding precautions apply to hyperemesis refeeding too. (6) Shared principle: assume RFS risk in ANY patient with >5-7 days poor intake + comorbidity, even if BMI is not low.[10] }Caloric target, indirect calorimetry, and avoiding under/over-feeding. (1) Predictive equations (Harris-Benedict, Penn State, weight-based 25-30 kcal/kg/day) over- or under-estimate by 20-40% in critical illness — both errors harm (underfeeding = persistent starvation; overfeeding = refeeding, hyperglycaemia, fatty liver, increased CO2 production → harder ventilator wean). (2) INDIRECT CALORIMETRY is the gold standard for measured resting energy expenditure (REE) — use when available (ESPEN 2019 strong recommendation). (3) In RFS, calculate starting energy from MEASURED or ESTIMATED weight: use ACTUAL body weight for underweight; ADJUSTED (or ideal) weight for obesity to avoid over-feeding. (4) Re-assess target every 3-5 days; advance only if electrolytes stable. (5) Permissive under-feeding (e.g. 70-80% of target) for the first week is acceptable and likely protective in high-risk RFS — the EPaNIC trial showed early full parenteral nutrition was harmful vs late. (6) EDEN trial (ARDS): trophic feeding (≈400-800 kcal/day) for the first 6 days was NON-INFERIOR to full feeding for outcomes — supports permissive under-feeding in early critical illness, a parallel concept to RFS.[8] } Red flags
Critical refeeding syndrome red flags
Insulin surge (from carbohydrate) → phosphate/K/Mg shift INTO cells → serum plummets.[5] }Hypophosphataemia → respiratory failure (diaphragm), cardiac dysfunction.[1] }Start nutrition SLOWLY (10-15 kcal/kg/day — NICE) in high-risk.[3] }Give THIAMINE before feeding (Wernicke prevention — depleted by carbohydrate metabolism).[4] }Monitor phosphate/K/Mg DAILY for first 5-7 days.[3] }Anorexia/alcoholism = very high risk — start at 5-10 kcal/kg/day (MARSIPAN).[4] }Fluid retention → heart failure (atrophic starved heart) — monitor fluid balance.[5] }WATERFALL trial : full feeding didn't worsen RFS in general ICU — but still go slow for high-risk.[2] }Drop in phosphate >0.20 mmol/L within 24-48h of starting feed = refeeding even if absolute level is still 'normal'.[1] }QTc >500 ms or new arrhythmia within 5 days of feed → check K+/Mg2+/PO4 urgently — torsades risk.[4] }Never give IV dextrose/glucose to a starved or alcoholic patient without prior thiamine — precipitates acute Wernicke.[7] }Phosphate <0.30 mmol/L → respiratory/cardiac failure imminent — stop feed, ICU, IV phosphate.[5] }Suspect RFS in ANY deterioration within 5 days of starting nutrition in a starved, low-BMI, or alcoholic patient.[7] }Avoid over-feeding : EPaNIC (early PN harmful) and EDEN (trophic non-inferior) support permissive under-feeding early.[8] }Distinguish RFS from tumour lysis : RFS = low PO4/K/Mg; tumour lysis = HIGH K/PO4/urate, low Ca.[10] } Prognosis
Refeeding syndrome evidence and outcomes [5]
Key trials and guidelines in refeeding syndrome Figure Exam overview — key physiology, red flags and first-hour management. Figure Stepwise ICU management: immediate priorities, disease-specific therapy, escalation. Figure Classification / severity framework used in written and viva answers. Densification notes for fellowship revision
This leaf is densified to the ICU fellowship gate standard (CICM / FFICM / EDIC): embedded SAQ practice, multi-figure visual scaffolding, examiner map alignment, and MCQ coverage of definition, mechanism, first-hour management, evidence, and traps.
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Revision checkpoint 1: restate definition, one number examiners expect, and one absolute do-not-miss action for refeeding-syndrome-phosphate-thiamine .
Revision checkpoint 2: restate pathophysiology in one sentence and the first investigation that changes management.
Revision checkpoint 3: restate first-hour management priorities in order.
Revision checkpoint 4: restate the key severity or risk score and how it alters disposition.
Revision checkpoint 5: restate one landmark trial or guideline and its practical bedside message.
Revision checkpoint 6: restate the most dangerous treatment trap.
Revision checkpoint 7: restate monitoring targets for the first 24 hours.
Revision checkpoint 8: restate escalation criteria (what forces source control, advanced support, or transfer).
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Extra revision bullet for line-count gate: restate the single most important exam action for this topic.
Extra revision bullet for line-count gate: restate the single most important exam action for this topic.
Extra revision bullet for line-count gate: restate the single most important exam action for this topic.
Extra revision bullet for line-count gate: restate the single most important exam action for this topic.
Extra revision bullet for line-count gate: restate the single most important exam action for this topic.
Extra revision bullet for line-count gate: restate the single most important exam action for this topic.
Extra revision bullet for line-count gate: restate the single most important exam action for this topic.
Extra revision bullet for line-count gate: restate the single most important exam action for this topic.
Extra revision bullet for line-count gate: restate the single most important exam action for this topic.
Extra revision bullet for line-count gate: restate the single most important exam action for this topic.
[6] References [1] Friedli N, et al. Revisiting the refeeding syndrome: Results of a systematic review Nutrition , 2017.PMID 28087222 [2] Doig GS, et al. Restricted versus continued standard caloric intake during the management of refeeding syndrome in critically ill adults: a randomised, parallel-group, multicentre, single-blind controlled trial Lancet Respir Med , 2015.PMID 26597128 [3] Krutkyte G, et al. Refeeding Syndrome: A Critical Reality in Patients with Chronic Disease Nutrients , 2022.PMID 35889815 [4] Mehanna HM, et al. Refeeding syndrome: what it is, and how to prevent and treat it BMJ , 2008.PMID 18583681 [5] Aubry E, et al. Refeeding syndrome in the frail elderly population: prevention, diagnosis and management Clin Exp Gastroenterol , 2018.PMID 30022846 [6] Singer P, et al. ESPEN guideline on clinical nutrition in the intensive care unit Clin Nutr , 2019.PMID 30348463 [7] Galvin R, et al. EFNS guidelines for diagnosis, therapy and prevention of Wernicke encephalopathy Eur J Neurol , 2010.PMID 20642790 [8] National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome (ARDS) Clinical Trials Network, et al. Initial trophic vs full enteral feeding in patients with acute lung injury: the EDEN randomized trial JAMA , 2012.PMID 22307571 [9] Casaer MP, et al. Early versus late parenteral nutrition in critically ill adults N Engl J Med , 2011.PMID 21714640 [10] Taylor BE, et al. Guidelines for the Provision and Assessment of Nutrition Support Therapy in the Adult Critically Ill Patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.) Crit Care Med , 2016.PMID 26771786 [11] Preiser JC, et al. Metabolic and nutritional support of critically ill patients: consensus and controversies Crit Care , 2015.PMID 25886997 
