Post-laparotomy shock gut with AKI and falling phosphate — dose, route, protein, refeeding and glucose

Model answer

(A) Trophic enteral now, no parenteral top-up — tolerate the early deficit (4 marks). Start EN early but run it trophic-to-moderate: EDEN randomised 1000 lung-injury patients to about 400 versus 1300 kcal per day for 6 days with ventilator-free days 14.9 versus 15.0 and 60-day death 23.2 versus 22.2 percent — no difference — and full feeding caused more vomiting, high residuals and constipation.^[1] PermiT confirms in 894 medical, surgical and trauma patients: 40-to-60 versus 70-to-100 percent of requirements (delivered 835 versus 1299 kcal per day with equal protein) gave 90-day death 27.2 versus 28.9 percent with no differences in intolerance, diarrhoea, infection or stay.^[3] Do not add PN on day 2 to chase targets: EPaNIC randomised 2312 early-PN (within 48 hours) against 2328 late-PN (day 8) patients and late initiation brought faster live discharge, fewer ICU infections (22.8 versus 26.2 percent), less cholestasis, less prolonged ventilation and 3 fewer renal-replacement days.^[6] His shock gut strengthens the wait: NUTRIREA-2 showed early isocaloric EN in ventilated shock raised bowel ischaemia without cutting death — bridge with PN only if EN proves impossible as shock resolves, and advance EN as perfusion returns.^[11]

(B) Usual-dose protein for the AKI — and restrict calories for the falling phosphate (3 marks). At 2.2-plus versus 1.2-or-less g per kg per day, EFFORT showed discharge alive 46.1 versus 50.2 percent with 60-day death 34.6 versus 32.1 percent and harm concentrated in AKI and high organ-failure scores.^[13] The AKI post-hoc makes it a decision, not a debate: 312 AKI patients — high protein slowed discharge alive (HR 0.5) and raised 60-day death (RR 1.4) across all stages, with harm disappearing only on replacement therapy.^[14] His phosphate fall is restriction physiology: relative hypophosphatemia over the first 2 ICU days marks patients harmed by early PN, and the refeeding trial in 339 ICU adults showed restriction versus standard support giving day-60 survival 91 versus 78 percent with longer overall survival.^[9][21] Restrict macronutrients temporarily — protein first — replete electrolytes, and recheck phosphate before advancing.

(C) Cap glucose at 180 or less, prokinet the intolerance, place postpyloric only for delivery (3 marks). NICE-SUGAR randomised 6104 patients to 81-to-108 versus 180-or-less targets: intensive control raised 90-day death (27.5 versus 24.9 percent, OR 1.14) with severe hypoglycaemia 6.8 versus 0.5 percent, and the operative subgroup trended worse — so cap at 180 or less, measure often, treat every low reading as the emergency.^[25] For his high residuals, prokinetics carry moderate-certainty benefit: 13 trials with 1341 patients — intolerance down (RR 0.73, 17.3 percent absolute), high residuals down (RR 0.69), post-pyloric placement success up — with no change in vomiting, diarrhoea, stay or death.^[29] If gastric delivery still fails, postpyloric routing raises delivered energy by 12 percent and cuts residuals — but changes nothing on death, pneumonia or aspiration, so place it for delivery, never as pneumonia prevention.^[27]