Mini Lecture: IV FluidsWilliam Graham, PGY2

January 2014Department of MedicineUC Irvine Medical Center

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Objectives

• Understand daily fluid and electrolyte requirements for an average adult

• Understand the major components of replacement fluid

• Maintenance vs. Resuscitation

• Complications of fluid therapy

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Water Input and Output of the “Normal” Adult

• Minimal Obligatory Daily Water 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

→ Average adult input/output is 30-35mL/kg/day (2.4L/day)

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Contents of IV Fluid Preparations

Na(mEq/L)

K(mEq/L)

Cl(mEq/L)

HCO3(mEq/L)

Dextrose(gm/L)

mOsm/L

D5W 50 278

½ NS 77 77 143

D51/2NS 77 77 50 350

NS 154 154 286

D5NS 154 154 50 564

Ringers Lactate (RL)

130 4 109 28 50 272

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Daily Electrolyte Requirements

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

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

• - Chloride: 60-150meq– Example: 1/2NS @ 100cc/hr provides ~180mEq of sodium and chloride/day!

- this is why NS should not be used for maintenance fluid in patients with normal renal function- risk of hyperchloremic metabolic acidosis

• - Bicarb: 1 meq/kg/day

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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?

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Maintenance Therapy

Purpose: Replace 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

- In general, patients who are afebrile, not eating, not physically active require less that 1 L of free water daily

- Patient’s with ESRD or edematous states (ex. cirrhosis, heart failure) require less maintenance due to decreased output and/or altered fluid distribution

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Maintenance Therapy3 approaches to determine the appropriate rate:

1) Calculate maintenance based on average requirement of 35cc/kg/day

2) “4/2/1” rule

4 ml/kg/hr for the first 10 kg (0-10kg)

2 ml/kg/hr for the next 10kg (11-20kg)

1 ml/kg/hr for remaining weight (21 kg and up)

3) Weight in kg + 40

Vignette: Pt weight 85kg.– 85kg x 35cc/kg/24hr= 3L/24 hr= 125cc/hr– 40 + 20 + 65 = 125cc/hr– 85 + 40 = 125cc/hr

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Maintenance Therapy

What type of fluid for maintenance?

- D51/2NS + 20 mEq KCl provides:

a) ~180 mEq/day sodium and chloride (100-250 sodium and 60-150 chloride needed/day)

b) ~50 mEq/day potassium (50-100 mEq needed/day)- avoid dextrose in patients with uncontrolled DM or hypokalemia- not much data to support addition of D5, however can be added to prevent

muscle catabolism

- Therefore, 1/2NS or D51/2NS + 20 mEq KCL would be appropriate choices.

- adjust maintenance fluids based on serum sodium concentration (ex. Change from 1/2NS to NS or D5NS if hyponatremia develops)

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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 is 45kg. SBP 80’s in the ED. She is started on IV pantoprazole.

1. What is your initial choice of fluids?

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Fluid Resuscitation

Purpose: Correct existing abnormalities in volume status or serum electrolytes

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

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Rate of Repletion

Severe volume depletion or hypovolemic shock? -> Rapid infusion of 1-2L isotonic saline (NS), then reassess parameters

- use Lactated Ringers if concern for re-expansion acidosis (ex. acute

pancreatitis)

Mild to moderate hypovolemia?1) Estimate fluid losses:

– Recall: Average output 2.4L/day for 70kg patient– estimate additional losses such as GI (diarrhea, vomiting) and high fever

-> add 100ml/day for each degree of temp > 37C

2) Choose rate 50-100mL/h greater than estimated losses

3) Select fluid based on type of fluid that has been lost and any co-existing electrolyte disorders

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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 is 45kg. SBP 80’s in the ED. She is started on IV pantoprazole.

1. What is your initial choice of fluids?

2. 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?

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Complications of IVF

The 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?

4. What is likely contributing to the SOB?

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Where is my bolus going?

1L D5W distributed into Total Body Water

Interstitial

226cc

Intra-vascular

114cc!!

Normal saline has no free water and is confined to ECF space; this is why it is the preferred IVF for resuscitation!

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%)

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Summary

• Treat IV fluids as a prescription just like any other medication, with consideration of renal function and clinical picture

• 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• Assess DAILY whether the patient continues to require IVF