Critical Care Mailbag: Fluid Resuscitation and Responsiveness
Scott Weingart and Anand Swaminathan
- Fluid responsiveness is the concept that a patient who receives a fluid bolus (typically 500 ml over 10 minutes) will have a significant increase in their stroke volume (at least 10%).
- During the early days of early goal directed therapy (EGDT), most clinicians in the U.S. were pushing large volumes of crystalloid in patients with septic shock.
- In this paradigm, checking fluid responsiveness wasn’t an issue because the answer was always “just give more fluids.”
- In recent years, this approach has started to fade as we learn more about the response to fluids in septic states.
- Current thoughts on fluids in sepsis:
- Most patients with sepsis have modest insensible losses (from increased work of breathing, fever, etc).
- Septic patients have systemic vasodilation and leaky vessels leading to third spacing of fluids.
- Infused crystalloid does not stay intravascularly for long periods of time in septic patients because of the leaky vessels.
- New fluid paradigm #1- fluid responsiveness:
- Before administering additional fluids to a patient with septic shock, check for fluid responsiveness.
- If the patient is responsive, continue to administer fluids.
- If the patient is not responsive, hold fluids and administer vasopressors.
- A review of fluid responsiveness measures.
- IVC variation: If a patient has a plump IVC without respiratory variation, fluids should be held.
- IVC variation is inaccurate in determining if a patient is fluid responsive.
- Passive leg raise (PLR): Passive leg raise is similar to bolusing 500 ml of fluid. After performing a leg raise, the following may be measured to see if stroke volume has increased:
- Blood pressure increase (via an arterial line): specific but not sensitive. If there is no increase in blood pressure, the patient may still benefit from fluids.
- Velocity Time Integral (VTI): ultrasound measurement of stroke volume.
- If VTI increases with PLR, the patient is fluid responsive.
- Cardiac output monitor: “Gold” standard is use of Swan-Ganz catheter
- Bioreactance monitors are relatively simple to use and, overall, give reliable numbers.
- Cons: Expensive and there is no data showing improved outcomes.
- New fluid paradigm #2 (Dr. Weingart’s approach)
- Give an initial fluid bolus and then stop. No additional fluids needed. Fluids are administered solely to replace losses.
- Consider early administration of vasoactive substances to maintain perfusion.
- In this paradigm, fluid responsiveness measures aren’t needed because additional fluid is not given.
- Case: A 55-year-old woman presents with pneumonia. She is initially tachycardic (130-140 bpm) and hypotensive (SBP 80/40 mmHg) with an O2 saturation of 88% on room air.
- Administer a fluid bolus for insensible losses. Approximately 500 - 1000 ml of fluid is a good amount, but in a young patient with a good heart you can even go to 20 ml/kg.
- After the initial fluid bolus, perform point-of-care ultrasound (POCUS) evaluating the heart, lungs, and IVC.
- If the IVC is plump without respiratory variation, the central venous pressure is already high and additional fluids are not useful. Added fluids may be harmful.
- If the lungs show prominent B-lines, there is already vascular congestion and additional fluids won’t be tolerated well.
- If the heart is hyperdynamic and the left ventricle (LV) is empty, additional fluids may be helpful.
- If the left ventricular squeeze is poor along with a plump IVC and B-lines, vasoactive substances are indicated.
- Case continued: The patient remains hypotensive after fluid bolus.
- Fluid responsiveness paradigm: check for fluid responsiveness and administer fluids if indicated. This is predicated on the belief that additional fluids can be helpful in select patients. Additional fluids should ONLY be given if the patient is determined to be fluid responsive.
- With the new fluid paradigm #2 (Dr. Weingart’s approach), vasopressors are started and there is no need to check for fluid responsiveness. This is predicated on the belief that additional fluids will not give lasting effects on hemodynamic parameters.
CorePendium chapter - Sepsis:
EM:RAP HD Fluid Resuscitation
EM:RAP Critical Care Mailbag August 2020 (Part 1)
EM:RAP Critical Care Mailbag August 2020 (Part 2)