An Empty “Tank” Can Be Bad, Maybe Worse Than You Think

fluid resuscitation

Today we are faced with a new disease challenge, a novel corona virus with no definitive widely accepted treatment. In the era of COVID-19 we may not be able to discern which patient has COVID, and which one does not. Even if a PCR is run, the test can take hours and accuracy is questionable. Recently we have all been taught to keep patients dry, especially ones with septic shock. The driver for this is the concern of over-resuscitation with IV fluid, potentially resulting in ARDS or other morbidity. The risk is real and the injury to those patients can be real as well.

However, persistent shock and hypotension can also cause harm. Whether your patient was previously healthy or is someone with chronic conditions or acute respiratory failure from COVID-19 or other diseases, an empty tank can be dangerous. It’s helpful to step back to medical school physiology to understand why. The human cardiovascular system is a reasonably closed circuit powered by a pump which circulates fluid and helps maintains adequate pressure. In this system, no fluid means no pressure (death), too little fluid and you can get very low pressure (trouble). Much like a piece of excavating equipment that relies on hydraulic fluid to move the digging arm, the human body relies on a certain amount of pressure in the circuit as well. If an excavator leaks hydraulic fluid, the digging arm will move but the engine will be under more and more strain until it gets so weak and that the digging arm can no longer move at all.

The human circulatory system is somewhat similar, if the tank is too empty, the heart works harder to pump blood and keep up with demands. Unlike the excavator we can squeeze capacitance vessels to push more fluid into the effective circulatory system, or actually just change the volume of the circulatory system – making it smaller and therefore hopefully increasing pressure. However, if the tank is empty or severely under-filled, no amount of vasopressors (to increase peripheral vasoconstriction) or inotropes (to improve cardiac output) will help.

Interestingly, while it can be hard to predict whose tank is empty, many septic shock patients present with significant hypovolemia. Combine several days of high fever, a good amount of vomiting and/or diarrhea, and minimal PO intake and you are likely to encounter a patient who has lost a lot of fluid. Even those we consider at risk for fluid overload such as CHF or dialysis patients often present with hypovolemia and need adequate fluid resuscitation just as much as patients without chronic disease. The reality is that this is not a decision of fluids versus no fluids, but how, when and how much.

In the resuscitation or “salvage” phase, hypotension needs to be treated as soon as possible to reduce the risk of organ injury. A rapid infusion of 250-500 ml of LR or Plasmalyte followed by immediate bedside reassessment is a common-sense strategy. POCUS can be used to differentiate between patients who will tolerate fluid and those are already volume overloaded. A quick check of the patient’s lungs to see if they are wet or dry (through evaluation of B-lines) and then a peek at the IVC and heart is sufficient. Is the left ventricle squeezing normally? If not, how abnormally? Is the IVC bulging and not changing with spontaneous respiration or does it collapse >50% with inspiration? If function is severely depressed and the IVC has minimal variation, great caution should be used with fluid. But a patient in shock with normal or moderately depressed function and a collapsible IVC will likely benefit from fluid. Based on available literature, POCUS can accurately select patients who will tolerate fluid from those who are already tanked up enough and will need pressors instead. Even patients with depressed left ventricular systolic function may be volume depleted, as reflected by a collapsing IVC, and respond nicely to fluid infusion; normalizing their blood pressure without pressors or increased lung water. It turns out that septic shock patients with perceived risk factors for fluid overload (CHF, renal failure, etc) actually have lower mortality and less need for mechanical ventilation when they receive early fluids in the course of their disease.1-4 In fact they may benefit more from earlier and adequate fluid resuscitation for septic shock than patients without chronic conditions.4

An interesting article just published in CHEST discusses how COVID-19 relates to pre-antibiotic era sepsis resuscitation.5  Without an obvious and ubiquitously used antimicrobial (in this case antiviral) treatment, only supportive care can make an impact on outcomes and this is where precise, thoughtful and early fluid resuscitation can make a bigger difference than ever for a COVID-19 patient with shock or sepsis. A new study from the International Fluid Academy also highlighted the use of precision fluid resuscitation while avoiding fluid overload.6  The article stresses an early and rapid fluid challenge to correct hypotension and determine fluid responsiveness, followed by fluid bolus administration or vasopressors as needed.

Whether the critically ill patient in front of you is hypotensive due to COVID-19, sepsis, hemorrhage, or some other cause, immediate fluid resuscitation is often the only way to rapidly increase their blood pressure to a safe range until other measures, if needed, can be employed. An active resuscitation approach – fluid bolus administration followed by immediate bedside response testing – is critical and may be best when coupled with widely available ultrasound guidance.

References

  1. Khan RA, Khan NA, Bauer SR, et al. Association Between Volume of Fluid Resuscitation and Intubation in High-Risk Patients With Sepsis, Heart Failure, End-Stage Renal Disease, and Cirrhosis. Chest. 2020;157(2):286-292. doi:10.1016/j.chest.2019.09.029
  2. Kuttab HI, Lykins JD, Hughes MD, et al. Evaluation and predictors of fluid resuscitation in patients with severe sepsis and septic shock. Crit Care Med. 2019;47(11):1582-1590. doi:10.1097/CCM.0000000000003960
  3. Leisman DE, Doerfler ME, Ward MF, et al. Survival Benefit and Cost Savings From Compliance With a Simplified 3-Hour Sepsis Bundle in a Series of Prospective, Multisite, Observational Cohorts. Crit Care Med. 2017;45(3):395-406. doi:10.1097/CCM.0000000000002184
  4. Liu VX, Morehouse JW, Marelich GP, et al. Multicenter Implementation of a Treatment Bundle for Patients with Sepsis and Intermediate Lactate Values. Am J Respir Crit Care Med. 2016;193(11):1264-1270. doi:10.1164/rccm.201507-1489OC
  5. Yataco A, Simpson S. Coronavirus Disease 2019 Sepsis: A Nudge Toward Antibiotic Stewardship. CHEST. 2020 July 28.
  6. Malbrain MLNG, Langer T, Annane D, Gattinoni L, Elbers P, Hahn RG, De Laet I, Minini A, Wong A, Ince C, Muckart D, Mythen M, Caironi P, Van Regenmortel N.Intravenous fluid therapy in the perioperative and critical care setting: Executive summary of the International Fluid Academy (IFA). Ann Intensive Care. 2020 May 24;10(1):64.