Enteral Nutrition in Septic Shock With Refractory Hypotension and Severe Obesity
52-year-old man (weight 128 kg, height 1.77 m, BMI 41) is admitted with perforated diverticulitis and septic shock. He underwent damage-control laparotomy and has an open abdomen. He is intubated and receiving norepinephrine 0.35 mcg/kg/min, which has increased over the past 2 hours; lactate is 4.8 mmol/L and creatinine is 2.1 mg/dL. He is on continuous renal replacement therapy. The ICU team has placed a nasogastric tube and asks whether to start enteral nutrition now. There is no evidence of bowel ischemia or obstruction, and the abdomen is being managed with a temporary closure device. The team wants a specific plan for initiation, energy and protein targets, formula choice, and what to do if gastric residual volume is high while vasopressor requirements are rising.
1. Should enteral nutrition be initiated now? State your decision and the physiologic reasoning, including what you would do if the norepinephrine requirement continues to rise.
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Do not start full enteral nutrition while the patient is in active, escalating shock. The combination of norepinephrine 0.35 mcg/kg/min and rising, lactate 4.8 mmol/L, and acute kidney injury on CRRT indicates inadequate perfusion and ongoing resuscitation. Early enteral nutrition is preferred in critical illness, but the caveats are unresolved shock, escalating vasopressors, and suspected bowel ischemia. Feeding a hypoperfused gut can increase the risk of ischemia and intolerance.
The practical plan is to continue resuscitation and reassess frequently. If the mean arterial pressure stabilizes and the norepinephrine dose is stable or decreasing, start trophic enteral nutrition at 10-20 mL/h rather than full targets. If norepinephrine continues to escalate, hold enteral nutrition and reassess after perfusion improves. Do not withhold nutrition indefinitely: once shock is controlled, early trophic feeding is appropriate. Parental nutrition is generally not started in the first week in a patient who is not malnourished at baseline, so the answer is not to switch immediately to TPN.
Document the reassessment criteria: MAP, vasopressor dose trend, lactate trend, urine output, abdominal exam, and signs of bowel ischemia. If the open abdomen is being managed without ischemia and the patient stabilizes, enteral nutrition can proceed.
2. Calculate a reasonable energy and protein target for this patient and choose an enteral formula. Show your assumptions.
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Use ideal body weight (IBW) for the protein target and a hypocaloric-high-protein strategy because BMI is 41. A simple IBW estimate for a 1.77 m man is about 72 kg. Energy can be estimated at 11-14 kcal/kg actual body weight or about 22-25 kcal/kg IBW. Using actual weight: 128 kg x 11-14 kcal/kg = about 1,400-1,800 kcal/day. Using IBW: 72 kg x 22-25 kcal/kg = about 1,580-1,800 kcal/day. These converge on roughly 1,500-1,800 kcal/day.
Protein in obesity and critical illness should be higher: about 2.0 g/kg IBW/day, and up to 2.5 g/kg IBW/day with CRRT because of amino acid losses. That is roughly 144-180 g/day. This is a high protein target, so choose a high-protein enteral formula, often 1.5 kcal/mL with a protein content near 6-7 g/100 mL, or use a standard 1.0 kcal/mL formula plus protein modulars if the pharmacy can compound safely. A 1.5 kcal/mL formula helps limit free water in a patient on CRRT, but monitor sodium, glucose, and triglycerides.
Start at trophic rate 10-20 mL/h and advance every 4-8 hours as tolerated toward the energy target, prioritizing protein. Do not try to reach full energy in the first 24 hours during active shock.
3. The nurse reports a gastric residual volume of 350 mL, abdominal distention, and a norepinephrine increase to 0.50 mcg/kg/min. What is your next step, and how would you prevent recurrent intolerance?
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Treat this as intolerance plus worsening perfusion, not as a reason to simply increase the feeding rate. Hold enteral nutrition, decompress the stomach, and reassess the abdomen for distention, tenderness, and signs of ischemia. Check for constipation, ileus, or obstruction with imaging if the clinical picture is unclear. Because norepinephrine has increased to 0.50 mcg/kg/min, the patient is not in the stable low-dose vasopressor state in which trophic feeding is usually continued.
If the residual volume is 350 mL with symptoms and rising vasopressors, holding feeds is appropriate. Do not routinely check gastric residual volumes in all patients, but when checked and accompanied by distention or instability, act on it. Once perfusion improves, consider a prokinetic such as metoclopramide 10 mg every 6 hours or erythromycin per institutional protocol, and consider post-pyloric feeding if gastric intolerance persists. Recheck electrolytes, glucose, and abdominal exam.
Prevention: use trophic initiation, advance slowly, avoid overfeeding, keep the head of bed elevated, review sedatives and opioids that slow motility, and use a feeding protocol with clear hold parameters. If intolerance persists despite prokinetics and stable perfusion, discuss post-pyloric access and whether supplemental parenteral nutrition is needed after the first week. In this patient, do not start TPN immediately during active shock.