1. Mini Lecture: IV Fluids
D.Mahammed Hussein
General Surgeon
Azadi Teaching Hospital

2. Understand the major components of replacement fluid
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 *

3. TOTAL: 1600mL 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
→ Average adult input/output is 30-35mL/kg/day (2.4L/day)
Emphasize the minimal intake/output of an average daily adult in order to understand rate and goal of fluid administration we order for our patients *

4. Contents of IV Fluid PreparationsNa
(mEq/L) K Cl
HCO3
Dextrose
(gm/L)
mOsm/L
D5W 50
278
½ NS 77
143
D51/2NS
350 NS
154
286
D5NS
564
Ringers Lactate (RL)
130 4
109 28
272
Important to understand the differences between the types of fluid we administer and the osmolality of each solution. Recognize that although D5 appears isotonic, the dextrose is metabolized quickly and therefore becomes a hypotonic solution rather rapidly. *

5. Daily Electrolyte Requirements
- Sodium: meq (western diet)
mostly excreted in urine
- Potassium: meq
mostly excreted in urine, 5% in feces
- Chloride: meq
Example: 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
No need to memorize, just to understand where the content of electrolytes in different fluid solutions comes from *

6. 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 edematous states (ex. cirrhosis, heart failure) require less maintenance due to decreased output and/or altered fluid distribution

7. 3. approaches to determine the appropriate rate:
Maintenance Therapy
3. 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
= 125cc/hr
= 125cc/hr
Initial approach is based on the average adult daily intake as explained on slide #3. *

8. What type of fluid for maintenance? - D51/2NS + 20 mEq KCl provides:
Maintenance Therapy
What type of fluid for maintenance?
- D51/2NS + 20 mEq KCl provides:
a) ~180 mEq/day sodium and chloride ( sodium and chloride needed/day)
b) ~50 mEq/day potassium ( 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)
Have the team go through the exercise of calculating the appropriate rate based on each approach. *

9. 1. What is your initial choice of fluids?
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?
Have the team recognize that this is a case of resuscitation (in contrast to the first case of maintenance therapy). *

10. Objective parameters used to assess volume deficit:
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
Transition from fluid administration for purpose of maintenance therapy to recognizing when fluids are being given for the purpose of resuscitation. Have the team come up with answers regarding the parameters used to assess volume deficit. *

11. Severe volume depletion or hypovolemic shock?
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 mL/h greater than estimated losses
3) Select fluid based on type of fluid that has been lost and any co-existing electrolyte disorders
Think about minimal intake/output and add ml/hr based on additional losses for each patient
Fluid of choice is generally normal saline. Lactate Ringer’s will be used in primarily in cases where you are trying to prevent re-expansion acidosis (as in acute pancreatitis). *

12. 1. What is your initial choice of fluids?
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?
Answers: 1) Initial choice of fluids would be bolus of Normal Saline (1-2L) while awaiting PRBC transfusion and reassess parameters.
2) D51/2NS:
- 45kg x 35cc/kg/24hr= 67cc/hr
- 4/2/1= =85cc/hr
- 45kg +40= 85cc/hr
Have the team recognize that the second part of the question is now a focus on maintenance therapy. Initially calculate the rate based on the three approaches previously discussed. The next slides will discuss adjusting the rate and type of fluids based on co-morbid conditions (CHF, etc) *

13. 3. What could be contributing to the hyponatremia?
Complications of IVF
The team decides to put her on 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?
Answers: 3) Think about composition of IV fluids
4) Fluid overload (too high rate of fluids, composition type), additional fluids from IV Abx and PPI (50-100cc per medication, either D5W or NS)
Recognize that the rate and type of fluids needs to be adjusted for co-morbid conditions such as CHF. In addition, IV medications often are mixed in NS or D5W, and when added up can account for unrecognized significant additional amounts of fluids that the patient is receiving. Transition to the next series of slides by stating that now we need to understand where in the body the fluid is going (i.e. intravascular versus extravascular space). *

14. Where is my bolus going? 1L D5W distributed into Total Body Water
Interstitial
226cc
Intra-vascular
114cc!!
Free water
content
ICF
ECF
Interstitial
Intravascular
D5W
1000cc
660cc
340cc
226cc
114cc (11%)
½ NS
500cc
500
330cc
+ 55cc from
free water content
170cc + 55cc
=225cc (22%) NS
330cc (33%)
To understand what happens to the IV fluids we give our patients- recognize that if D5W is given, only 10% of it will end up in the intravascular space. This is the reason we don’t give D5W for resuscitation. Normal saline has no free water and is confined to ECF space.
Normal saline has no free water and is confined to ECF space; this is why it is the preferred IVF for resuscitation! *

15. Determine if patient needs maintenance or resuscitation
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 *