Anesthesiology APPLIED Exam › Critical care, resuscitation and trauma

Fluid management: crystalloid, colloid, goal-directed

Critical care, resuscitation and trauma·~5 min read· Physician-reviewed✓ Sourced · 5

Stem

A 63-year-old man, 84 kg, is scheduled for an open pancreaticoduodenectomy on an enhanced-recovery pathway. He drank a carbohydrate drink 2 hours before arrival. After induction his blood pressure falls from 138/80 to 88/52. He has a radial arterial line with a monitor that displays pulse-pressure variation, currently 8%, and he is ventilated at 8 mL/kg.

Question

What is your fluid strategy for this case, and how will you treat this blood pressure?

Ideal answer

HeadlineThis post-induction hypotension is anesthetic vasodilation: a vasopressor, not fluid. For the case, euvolemia and perfusion, not a fixed number of liters.

Not dry, not preload-responsive: clear fluids are allowed up to 2 hours before, ERAS includes carbohydrate loading, and PPV is 8% on controlled ventilation.
Balanced crystalloid, modest maintenance rate: lactated Ringer's or Plasma-Lyte, replacing measured losses, without the old large "third space" volumes.
Goal-directed 250 mL boluses, because this is major surgery with large shifts: given when SVV or PPV says preload-responsive, stopped when stroke volume stops rising.
Moderately liberal, modest positive balance, because a truly restrictive regimen increased kidney injury in RELIEF.¹
Blood for blood loss when hemoglobin and physiology call for it; never hydroxyethyl starch.

Watch for: urine output, lactate, stroke-volume trend; abdomen open, the stroke-volume response to a challenge beats PPV.

Breaking down the answer

Balanced over normal saline — saline causes hyperchloremic acidosis and, in SMART (15,802 critically ill adults), slightly more major adverse kidney events (15.4% vs 14.3% balanced).² Changes if: hypochloremic alkalosis, or hyponatremia or brain edema where LR's lower tonicity matters; then saline.
Albumin — reasonable in sepsis after large crystalloid volumes³ and in cirrhosis with paracentesis or spontaneous bacterial peritonitis; not superior for routine surgery. Avoided in traumatic brain injury: SAFE-TBI 24-month mortality 33.2% vs 20.4% with saline.⁴
No hydroxyethyl starch — the FDA boxed warning, strengthened in 2021, cites mortality, kidney injury and excess bleeding: not to be used unless adequate alternative treatment is unavailable;⁵ Surviving Sepsis recommends against starches.³
Dynamic over static markers — CVP does not predict fluid responsiveness, and Surviving Sepsis prefers dynamic measures;³ SVV or PPV over 12–13% does, but only with controlled ventilation, tidal volume about 8 mL/kg, sinus rhythm and a closed chest.
Restrictive is not zero — RELIEF (3,000 major abdominal patients): a restrictive regimen (median 3.7 L vs 6.1 L over surgery and the first 24 hours) did not improve disability-free survival and raised acute kidney injury, 8.6% vs 5.0%.¹
Glycocalyx — hypervolemia releases ANP and sheds the endothelial glycocalyx, so more fluid leaks into the interstitium: why excess fluid harms, and why third-space loss is largely a myth.

Follow-up question

The case runs 6 hours and he has received 7 L of crystalloid. At the end his PaO2/FiO2 is 180, he has bilateral crackles and a swollen face, and urine output is 20 mL/h. The surgeon asks you to give more fluid for the oliguria. Do you?

Follow-up answer

HeadlineNo. This is iatrogenic fluid overload with pulmonary edema; I tell the surgeon more fluid worsens the lungs and the anastomosis.

I keep him intubated, apply PEEP, and check an echo and a lung ultrasound for B-lines. I support the pressure with norepinephrine rather than volume, and give furosemide once perfusion is assured, because volume overload is now the indication. Bowel-wall edema raises leak rates, so I review the anastomotic risk with the surgeon. I reassess oxygenation, urine output and lactate over the next hours and plan ICU care.

Pitfalls that cost points

Calculating a "third space" replacement of 6–8 mL/kg/h.
Saying "restrictive" without defining it: too little and too much both harm, and under-resuscitation costs kidneys.

Rapid-fire

Q: Why does PPV lose meaning in laparoscopy and with low tidal volumes? A: High intra-abdominal pressure and small tidal volumes change the heart-lung interaction; the thresholds were validated at 8 mL/kg with a closed abdomen.

Q: Is lactated Ringer's safe in renal failure? A: Yes; its potassium of 4 mEq/L raises serum potassium less than saline's acidosis does.

Q: Why does crystalloid not stay in the vessels? A: It distributes across the whole extracellular space, and it leaks faster when inflammation or hypervolemia has damaged the glycocalyx.

Q: What tells you a fluid bolus worked? A: A rise in stroke volume or cardiac output of 10–15%; a rise in blood pressure alone is not enough.

Numbers to know

Item	Value
Maintenance (4-2-1 rule)	4 mL/kg/h first 10 kg, 2 next 10, 1 thereafter
Clear fluids before surgery	Up to 2 h (ASA)
Fluid challenge	250 mL over 5–10 min
SVV/PPV responsiveness	> 12–13%
Responsiveness endpoint	Stroke volume rise ≥ 10–15%
Normal saline chloride	154 mEq/L

Sources

1.RELIEF trial: restrictive versus liberal fluid therapy in major abdominal surgery · ANZCA Clinical Trials Network, 2018 · anzca.edu.auMyles et al., NEJM 2018; restrictive 3.7 L vs liberal 6.1 L; AKI 8.6% vs 5.0%.
2.Balanced Crystalloids versus Saline in Critically Ill Adults (SMART) · NEJM, 2018 · pubmed.ncbi.nlm.nih.gov
3.Surviving sepsis campaign: international guidelines for management of sepsis and septic shock 2021 · SCCM / ESICM, 2021 · pmc.ncbi.nlm.nih.gov
4.Saline or albumin for fluid resuscitation in patients with traumatic brain injury (SAFE-TBI) · NEJM, 2007 · pubmed.ncbi.nlm.nih.gov
5.Labeling Changes on Mortality, Kidney Injury, and Excess Bleeding with Hydroxyethyl Starch Products · FDA, 2021 · fda.gov

Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.