Determining Fluid Status in Patients

Maintaining the correct fluid balance in the body is crucial to the health of our patients. Knowing how to check for fluid status in patients will help determine if they are overhydrated or dehydrated. 

That said, learning how to determine fluid status in your patients is essential, and you will learn all about it in this post.

Assessing a patient’s fluid status is a critical skill you will regularly do as a nurse. It involves evaluating if a patient is hypovolaemic, euvolemic, or hypervolaemic.

Hypovolaemia vs Hypervolaemia 

Hypovolaemia refers to a deficit of fluid in the body. Causes include:

• Poor fluid intake.
• Excessive fluid loss (e.g., vomiting, diarrhea, hemorrhage, excessive diuretic therapy).
• Third, space loss of fluid.

Hypervolaemia refers to an excess of fluid in the body. It is also known as fluid overload. Hypervolaemia is expected in the elderly and those with renal or cardiac failure.

It can be caused by excessive fluid intake or inappropriate fluid retention (e.g., heart failure, renal failure). It is also why checking patients’ fluid status is crucial. 

Assessment Findings Determining Fluid Status in Patients

• Bleeding from any source
• Vomiting: frequency, volume, presence of blood
• Stools: frequency, volume, presence of blood
• Fever and diaphoresis
• Urine output: color and volume
• Heart rate
• Lung sounds
• Pre-syncope/syncope
• Mucous membrane – Wet or dry?
• Skin tugor – skin tenting 
• Capillary refills <3 seconds
• Oral intake
• Daily weight 
• Fluid restrictions
• Fluid overloaded symptoms:
  • shortness of breath
  • Orthopnoea
  • paroxysmal nocturnal dyspnea
  • leg swelling

Labs of Fluid Status in Patients

• Full blood count – May reveal raised hematocrit in hypovolaemia  
• Urea and Electrolytes – Urea/creatinine will be raised in hypovolaemic patients and those with acute or chronic renal disease. Electrolytes such as sodium may be low in hypervolaemic patients (e.g., dilutional hyponatremia).
• Urine and Serum osmolality – consider if suspected SIADH or DI. 
• BNP is a marker of cardiac stretch under the effect of fluid overload.

Passive leg raise

If a patient has a blood pressure cuff, and you want to see if the patient will be fluid responsive, a passive leg raise is easy to check. Passively raise the patient’s legs to at least 45 degrees and check a patient’s blood pressure before and after the leg raise.

You can also lift the foot of the bed and see if there are changes in the blood pressure. This motion acts as a mini fluid bolus because you are forcing the blood to go from the legs into the core. 

Orthostatic 

Orthostatic hypotension, also called postural hypotension, is a form of low blood pressure that happens when standing after sitting or lying down. To check orthostatic:

1. Have the patient lie down for 5 minutes.
2. Measure blood pressure and pulse rate.
3. Have the patient stand.
4. Repeat blood pressure and pulse rate measurements after standing for 1 and 3 minutes.

A drop of 20 mmHg in the systolic is supportive of hypotension.  

Jugular venous pressure (JVP)

JVP provides an indirect measure of central venous pressure. The Internal jugular vein runs between the medial end of the clavicle and the ear lobe. 

To check this position, see that the patient is in a 45-degree place, turn their head slightly to the left, and assess the vein. 

A raised JVP indicates the presence of venous hypertension/hypervolemia. It can also be indicative of Right-sided heart failure. 

Patients with a Central Venous Pressure (CVP) 

These patients have access to the central venous system and peripheral arterial line. When you have a Central Venous Pressure (CVP), you can measure the patient’s preload. That will directly correlate with the patient’s fluid status. 

A CVP is good for checking where your patient’s fluid level is moving. A normal CVP is between 8 to 12 mmHg. 

Systemic Vascular Resistance (SVR)

If you don’t have a Swan, you can still check an SVR by Non-Invasive Continuous Measurement. SVR is the afterload, the pressure the heart is working against to push blood across the body.

A normal SVR is between 900 and 1440 dyn/s. If your SVR is below 900, you will be more dilated vascularly; if above 1500, you will be more clamped down. 

So if you have a patient that needs fluids, you will have someone with a high SVR because the body is clamping down to increase volume to help maintain blood pressure.

Maybe your patient is low BP, but the SVR is down, well, that can be a sepsis issue, and we can fix the SVR with vasopressors. 

Swan-Ganz catheterization

Swan-Ganz catheterization is also known as right heart catheterization. The tiny catheter is placed into the right side of the heart and the arteries leading to the lungs.

This catheter monitors the heart’s function, blood flow, and pressures in and around the heart. 

One way to check fluid status on a Swan is by looking at the cardiac index. The index relies on cardiac output and turns cardiac output into a normalized value that accounts for the patient’s body size. A normal Cardiac Index is 2.5 – 4.0L/min/m2

Here’s how you can determine the fluid status in your patients correctly. Click here for the full episode 👇

TIMESTAMP:

00:00 Introduction
01:21 Hypovolaemia vs Hypervolaemia
03:36 Assessment findings to determine fluid status
13:28 Passive leg raise
15:13 Orthostatic
17:02 Jugular Venous Pressure
18:06 Central Venous Pressure
24:55 Systemic Vascular Resistance
28:24 Swan-Ganz catheterization
33:07 Wrapping up the episode