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

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 *

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 *

Contents of IV Fluid Preparations Na (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. *

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 No need to memorize, just to understand where the content of electrolytes in different fluid solutions comes from *

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

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 40 + 20 + 65 = 125cc/hr 85 + 40 = 125cc/hr Initial approach is based on the average adult daily intake as explained on slide #3. *

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 (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) Have the team go through the exercise of calculating the appropriate rate based on each approach. *

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). *

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. *

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 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 Think about minimal intake/output and add 50-100ml/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). *

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= 40+20+25=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) *

3. What could be contributing to the hyponatremia? 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? 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). *

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! *

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 *