IV Fluids

Bindu Swaroop, MDInpatient Medicine Core CurriculumVA Long Beach Health Care System

Objectives

• Understand daily fluid and electrolyte requirements for an average adult

• Understand the major components of replacement fluid

• Maintenance versus Resuscitation

• Complications of fluid therapy

Input and Outputof the “Normal” Adult

• Minimal Obligatory Daily input:– Ingested water: 500mL – Water content in food: 800mL– Water from oxidation : 300mL

» TOTAL: 1600mL• Minimal Obligatory Daily water output:

– Urine: 500mL– Skin: 500mL– Respiratory tract: 400mL– Stool: 200mL

» TOTAL: 1600mL

On average, an adult input and output is 30-35mL/kg/day (about 2.4L/day)

Electrolyte Requirements

• Sodium: 100-250meq (western diet)– mostly excreted in urine

• Potassium: 50-100meq– mostly excreted in urine, 5% in feces

• Chloride: 60-150meq

• Bicarb: 1-3meq/kg/day

Contents of IV Fluid PreparationsNa(mEq/L)

K(mEq/L)

Cl(mEq/L)

HCO3(mEq/L)

Dextrose(gm/L)

mOsm/L

D5W 50 278

½ NS 77 77 143

NS 154 154 286

D51/2NS 77 77 50 350

D5NS 154 154 50 564

Ringers Lactate (RL)

130 4 109 28 50 272

Case Vignette

58 y/o male with h/o HTN, dyslipidemia, admitted for cough and atypical chest pain. Found to have abnormal CXR and CT Thorax concerning for malignancy . Kept NPO overnight for possible bronchoscopy with biopsy in the morning. He is placed on NS @ 75cc/hr.

1. Was the right solution picked?2. Is the rate correct?

Maintenance Therapy

• Replaces the ongoing losses of water and electrolytes under NORMAL physiological conditions

• Used when the patient is not expected to eat or drink normally for prolonged period of time

• Patients who are afebrile, not eating, not physically active require less that 1 L of electrolyte free water per day

Maintenance Therapy• Initial approach:

– 2-3L/day (30-35cc/kg/day) of D51/2NS with 20meq of KCL • averages to 90-125mL/hr• This provides 3.4 g of sodium (similar to a hospital diet)

– Dextrose containing solution should be used in patients with hypoglycemia or ketoacidosis; avoid in patients with uncontrolled DM or hypokalemia

– There is not much data to suggest addition of D5 is beneficial, however can be added to prevent catabolism

Maintenance Therapy• Alternative Approaches: •4/2/1” rule

-4 ml/kg/hr for the first 10 kg2ml/kg/hr for the next 10kg then 1 ml/kg/hr for remaining weightORWeight in kg + 40

For the Clinical Vignette:– Pt weight 85kg

• 85kg x 35cc/kg/24hr= 3L / 24 hr= 125cc/hr• 40+20+65=125cc/hr (using “4/2/1”)• 85+40=125cc/hr

-Fluid choices: 1/2NS or D51/2NS would be appropriate choices

Fluid Resucitation

• Correct existing abnormalities in volume status or serum electrolytes

• Parameters used to assess volume deficit:– Blood pressure– Jugular venous pressure– Urine sodium concentration– Urine output– Pre and post deficit body weight

Rate of Repletion• Severe volume depletion or hypovolemic shock: rapid

infusion of 1-2L isotonic saline (NS)• Mild to moderate hypovolemia:

– Choose a rate that is 50-100mL/h greater than estimated fluid losses

• urine output 50ml/h• insensible losses = 30ml/h • additional loss such as GI, high fever (additional

100ml/day for each degree of temp >37C, etc)– Choice of fluid: based on type of fluid that has been lost

and any co-existing electrolyte disorders

Clinical Vignette 86y/o female admitted with nausea and vomiting and c/o

rectal bleeding. She has a history of recent admission for CHF exacerbation. Weight 45kg. SBP 80’s in the ED. She is started on IV pantoprazole.

1. What is your initial choice of fluids?-Normal Saline

She is kept NPO for EGD and colonoscopy the next morning. After receiving 2u PRBC and normal saline you decide to start maintenance fluids. What rate and type of fluid do you choose?

-D51/2NS

-45kg x 35cc/kg/24hr= 67cc/hr-4/2/1= 40+20+25=85cc/hr-45kg +40= 85cc/hr

Complications of IVFThe team decides to put her on D51/2NS @ 125cc/hr. Her repeat serum sodium level is 130 the next morning and she is complaining of some SOB. She is thought to have an infiltrate on CXR and started on IV Zosyn and Vancomycin for hospital acquired pneumonia.

3. What could be contributing to the hyponatremia?-think about composition of IV fluids

4. What is likely contributing to the SOB?

-fluid overload (too high rate of fluids, composition type)-additional fluids from IV Abx and PPI (50-100cc per medication,

either D5W or NS)

Understanding Salt and Water

Normal saline has no free water and is confined to ECF space

Where is the Fluid Going?

Where is the Fluid Going?

Free water content

ICF ECF Interstitial Intravascular

D5W 1000cc 660cc 340cc 226cc 114cc (11%)

½ NS 500cc 500cc 500 330cc+ 55cc from free water content

170cc + 55cc=225cc (22%)

NS 0 0 1000cc 660cc 330cc (33%)

Summary

• Treat IV fluids as “prescription” like any other medication• Determine if patient needs maintenance or resuscitation• Choose fluid type based on co-existing electrolyte

disturbances • Don’t forget about additional IV medications patient is

receiving• Choose rate of fluid administration based on weight and

minimal daily requirements• Avoid fluids in patients with ECF volume excess• Always reassess whether the patient continues to require IVF