Fluid Responsiveness: How non-invasive hemodynamic monitoring can prevent the danger of overloading
We’re all familiar with the scene: a critically ill patient is rushed into hospital and wheeled through the corridors on a gurney, a team of doctors running alongside. A clear bag of fluid is hooked up and the fluid drips intravenously into the patient’s bloodstream.
We assume this fluid is helping to keep the patient alive, to keep their organs functioning, but do we know that the patient is benefitting from this fluid intervention? Do we know if it’s the right fluid composition for this patient? Is it being administered at the right rate and in the correct quantity?
These decisions often have to be made under extreme pressure in emergency wards and acute admission units. However, in many cases they are little more than guesswork, with insufficient information to go on, and this is putting patients at risk.
Non-invasive beat-by-beat monitoring can give medical staff the insight they need to be far more precise with fluid loading and thus eradicate the risk currently posed to patients.
Risks associated with IBP
When a patient moves out of intensive care and onto the general ward, their blood pressure is monitored using a sphygmomanometer, or arm cuff – a device familiar to most patients from visiting their local doctor, as well as any hospital experiences. This non-invasive method is used in place of IBP for reasons of cost and patient comfort.
While IBP is the criterion standard for measuring blood pressure, providing the continuous accuracy and consistency required in critical care situations, it is not without its drawbacks. Cannulation of an artery must be carried out by a trained operator and can be time-consuming, as well as uncomfortable for the patient.
Furthermore, there is an associated risk (albeit small) of complications including hematoma, embolism, thrombosis, arterial damage, nerve damage, and infection. In very rare cases patients can develop ischemia, pseudo aneurysm or arteriovenous fistula.
The knife-edge of fluid administration
Fluid administration should be guided by an assessment of fluid responsiveness combined with the determination of the potential benefits and harms of fluid administration. Fluid loading is a common procedure administered by physicians to test the fluid responsiveness of hemodynamically unstable, critically ill patients. A 500mm bolus of crystalloid will be loaded intravenously (IV) into the patient’s bloodstream and the cardiac output assessed. A 10-15% increase in stroke volume is the standard indicator that the patient is fluid responsive and further fluids can be safely administered.
But in half of all cases fluid loading fails to improve cardiac output. That means 50% of patients put on IV fluids are at risk of developing complications as a result. More than 80% of hospitalized patients receive IV fluids in this way; one in five suffer complications because the fluids were delivered in the wrong volume or at the wrong time.
Giving non-fluid responsive patients additional fluids (extended fluid loading) is associated with increased morbidity and mortality. It will accelerate a rise in cardiac filling pressures, leading to pulmonary and general oedema. On the other hand, insufficient resuscitation is associated with organ hypoperfusion and ischemia.
In 1999, the National Confidential Enquiry into Perioperative Deaths reports highlighted that a significant number of hospitalized patients were dying as a result of infusion of too much or too little fluid. The report recommended that fluid prescribing should be given the same status as drug prescribing.
So it’s incredibly important to give medical teams a fast, accurate and unobtrusive method of determining fluid volume status in hemodynamically unstable patients.
Accurate assessment of fluid responsiveness
So how can physicians more accurately assess a patient’s fluid status and predict their fluid responsiveness during those hectic minutes of clinical examination? To successfully predict fluid responsiveness, a change in preload must be generated, e.g. through passive leg raising (PLR), while measuring the subsequent changes in stroke volume or its derivatives such as pulse pressure.
It has been shown that this combination of PLR and continuous tracking of stroke volume enables the prevention and treatment of organ hypoperfusion at any time, while avoiding inappropriate fluid loading.
VitalStream™ is a wearable, wireless device that provides immediate and continuous non-invasive evaluation of hemodynamics and fluid responsiveness via a simple finger sensor. Its beat-by-beat monitoring of key cardiovascular parameters heart rate, blood pressure, stroke volume and cardiac output is ideal for immediately picking up hypotensive events, even short durations of which are associated with acute kidney injury and myocardial injury.
A simple solution to a complex problem
For doctors attending to hemodynamically unstable, critically ill patients, deciding on the optimal amount, composition and delivery rate of IV fluids can be a stressful and complex challenge. If decisions can be based on accurate assessment of the patient’s individual condition and needs, then severe complications can be avoided and the associated human and financial costs saved.
Continuous non-invasive beat-by-beat hemodynamic monitoring is a game changer for physicians who find themselves in this precarious position on a daily basis, for the hospitals that employ them and, most importantly, for their patients.