Fluids and Electrolytes September 10, 2008 Karen Koo, PGY5 Chief Critical Care Medicine Fellow Division of Critical Care Medicine McMaster University, Hamilton ON
Objectives Major Body Fluid Compartments Review of physiology of volume regulation Parenteral Fluid Therapy Cases of Electrolyte imbalances
Relationship between the volumes of major fluid compartments
Composition body fluid compartments Plasma (mmol/L) ICF Na+ 143 9 K+ 5 135 Ca2+ 1,3 <0,8 Mg2+ 0.9 25 Cl- 103 HCO3- 24 HPO42- 0,4 74 Sulphate- 19 Protein- 1,14 64
Daily Fluid Requirements Average Adult needs: H2O ~ 30-35ml/kg/hr (2-3 liters/day) Na+ ~ 1 ml/kg/hr K+ ~ 1 ml/kg/hr Cl- ~ 1.5 ml/kg/hr
Sources of daily water loss Urine 1200-1500 ml/d (30ml/hr) Sweat 200-400 ml/d Lungs 500ml/d Feces 100-200 ml/d
Composition of GI Secretions Source Volume (ml/24h) Na+* K+ Cl- HCO3- Salivary 1500 (500~2000) 10 (2~10) 26 (20~30) 10 (8~18) 30 Stomach 1500 (100~4000) 60 (9~116) 10 (0~32) 130 (8~154) Duodenum 100~2000 140 5 80 Ileum 3000 140 (80~150) 5 (2~8) 104 (43~137) Colon 100-9000 60 40 Pancreas 100-800 140 (113~185) 5 (3~7) 75 (54~95) 115 Bile 50-800 145 (131~164) 5 (3~12) 100 (89~180) 35 * Average concentration: mmol/L
Daily Electrolyte loss Na+ 100 mEq K+ 100 mEq Cl- 150 mEq
Quiz #1: True or False statements Concerning body fluid compartments: a) Water constitutes 70% of the total body weight b) Plasma constitutes a quarter of the ECF volume d) Interstitial fluid volume for a 70 kg man is approximately 9 litres e) The ECF/ICF volume ratio is smaller in infants and children than it is in adults FTTF
Regulation of Fluids
Regulation of Fluids Renal sympathetic nerves Renin-angiotensin- aldosterone system Atrial natriuretic peptide (ANP)
Parenteral Fluid Therapy Crystalloids Na+ main osmotically active particle useful for volume expansion (mainly interstitial space) for maintenance infusion correction of electrolyte abnormality
Crystalloids Isotonic crystalloids - Lactated Ringer’s, 0.9% NaCl - 25% remain intravascularly Hypertonic saline solutions - 3% NaCl Hypotonic solutions - D5W, 0.45% NaCl - < 10% remain intra- vascularly, inadequate for fluid resuscitation
Colloid Solutions Contain high molecular weight substancesdo not readily migrate across capillary walls Preparations - Albumin: 5%, 25% - Hydoxyethyl starches ie pentaspan - Red cell concentrates - platelets, plasma
Distribution of Parenteral Fluids Type of Fluid ECF=1/3 TBW ICF=2/3TBW IVF=1/4ECF ISF=3/4ECF 1000ml D5W 83 250 667 1000ml 2/3:1/3 139 417 444 1000ml R/L or 0.9%NS 750 500mL 5%albumin 500 100mL 25% albumin -400 500mL Pentaspan 1 unit RBC 450
Composition of Parenteral Fluids Solutions Volumes Na+ K+ Ca2+ Mg2+ Cl- HCO3- Dextrose mOsm/L ECF 142 4 5 103 27 280-310 Lactated Ringer’s 500 130 3 109 28 273 0.9% NaCl 154 308 0.45% NaCl 77 D5W D5/0.45% NaCl 50 406 3% NaCl 513 1026 6% Hetastarch 310 5% Albumin 250 130-160 <2.5 330 25% Albumin 100
Quiz #2: 70F has small-bowel fistula with output of 1.5L/d. Replacement of daily losses should be handled using the fluid solution that has the following composition: Na K Cl HCO3 a) 130 4 109 28 b) 154 0 154 40 c) 77 0 77 0 e) 513 0 513 0
Quiz #3: 68M admitted with diagnosis of partial SBO with Hx of Chrons Disease vomits bilious coloured emesis. His is lethargic. 37C, 88/50 mmHg, HR 110, RR 25, SpO2 99 on 2Lnp JVP flat, chest clear with normal heart sounds Abd distended & mild epigastric tenderness Na 130, Cl 108, K 5.1, Cr 110, BUN 10.2 Hg 100, WBC 9.9, Plts 400, INR 1.5, APTT 30
Quiz #3: Your staff asks you to see this patient. What is the most appropriate resusitation fluid: a) 1 unit of packed RBC b) 500 ml of Ringers Lactate solution c) 500ml 5% albumin d) 500ml Pentaspan e) 500ml 0.9% normal saline
SAFE Study (NEMJ 2004:350 Safe Investigators) RCT: 4% albumin vs normal saline for intravascular-fluid resuscitation Primary outcome: 28 day all cause mortality N = 6997 patients No significant differences 726 deaths albumin group vs 729 deaths saline group (RR 0.99; 95% CI 0.91 to 1.09; P=0.87 numbers of days spent in the ICU or in the hospital days of mechanical ventilation days of renal-replacement therapy
28% day Kaplan–Meier Estimates Probability of Survival: normal saline vs 4% albumin (NEMJ 2004:350 Safe Investigators)
RR of Death among the Patients in the Six Predefined Subgroups (NEMJ 2004:350 Safe Investigators)
Colloid solutions for fluid resuscitation (Cochrane Database Syst Rev Seventy RCTs comparing colloid solutions in critically ill and surgical patients thought to need volume replacement, N = 4375 participants Albumin versus hydroxyethyl starch pooled RR 1.14 (95% CI 0.91 to 1.43) for mortality albumin versus dextran (RR= 3.75 95% CI 0.42 to 33.09). no evidence that one colloid solution is more effective or safe than any other
Calculation of Maintenance Fluids For a 24 hr period, use 100/50/20 Rule 100ml/kg for first 10kg 50ml/kg for next 10kg 20ml/kg for every kg over 20 For hourly maintenance rate, use 4/2/1 Rule 4ml/kg for first 10kg 2ml/kg for next 10kg 1ml/kg for every kg over 20
Quiz #4 55M has been admitted for an elective resection of a pelvic mass. He is NPO for the next 12 hours. He weighs 70kg and has normal renal function. What is the most appropriate iv maintenance rate? 0.9% NS at 200ml/hr 0.45% NS/D5W at 100ml/hr D5W at 100ml/hr Ringer’s Lactate at 50ml/hr
Clinical Cases: Electrolyte Imbalances
Case 1 39M POD2 following ventral hernia repair. Background: HTN, DM nephropathy Meds: Ramipril 10mg daily, morphine prn Patient is weak, c/o paraethesia Post-op EKG: Sinus bradycardia 40bpm, peaked T waves, depressed ST with prolonged PR, wide QRS O/E DTR depressed What is electrolyte disturbance? What is ddx most likely surgical causes? What is the acute management strategy?
Case 1 What is electrolyte disturbance? Hyperkalemia What are the most likely surgical causes? RF, Drugs, Acidosis, Tissue injury blood transfusions What is the acute management strategy? Cardioprotection, shifting, elimination
Case 2 70F one week of constipation and vomitting. Background: DM, Dilated cardiomyopathy, Intestinal fistula Meds: Insulin, Lasix 80mg bid Patient c/o weakness, nausea/vomitting and abdominal tenderness O/E 36.4C 100/60 HR 110, RR12, SpO2 99% r/a JVP flat, chest clear, normal heart sounds, Abdominal distension, no bowel sounds EKG: Sinus tachycardia with occasional PVCs, diffuse flattening of T waves, U waves
Case 2 What is electrolyte disturbance? Hypokalemia What are the most likely surgical causes? Drugs (diuretics, steroids, Insulin etc), diarrhea, vomitting, intestinal fistula, NG aspiration, insufficient supplementation What is the acute management strategy? potassium supplementation iv/po
Case 3 67M unexplained 30lb wt loss over 6months and hemoptysis presents a GTC seizure Background: HTN, smoker Meds: HCTZ 25mg daily O/E 37C 110/70 HR 88, RR14, SpO2 98%/ra Lethargic & confused, No focal neuro deficits JVP 4cmASA, PPP chest clear, normal heart sounds Abd distended with faint bowel sounds CXR: speculated LLL nodule
Case 3 What is electrolyte disturbance? Hyponatremia What are the most likely surgical causes? Access clinical fluid status
Case 3 – Hyponatremia Management What is the acute management strategy? Depends on etiology & chronicity Be careful! Rate of correction should be <0.5mEq/h, <10mEq/24hr, <18Eq in first 48h Check lytes frequently during correction Use 3% NaCl ONLY if severe hyponatremia (Na+ <115) or if dramatically symptomatic with acute onset
Case 4 89F admitted with acute pancreatitis on ward for 2 weeks. Progressive confusion in last few days with new tremors Otherwise healthy, no meds. On TPN. Net fluid balance 24hrs –4L, u/o 200ml/hr O/E 36C 110/50 HR 110, RR 10, SpO2 98%r/a stupourous & clinically hypovolemic ++peripheral edema
Case 4 What is electrolyte disturbance? Hypernatremia What are the most likely surgical causes? Inadequate hydration, diabetes insipitus, diuresis, vomitting/diarrhea, iatrogenic (TPN) What is the acute management strategy? Depends on etiology & chronicity (D5W or 0.45% normal saline)
Case 5 26F with newly diagnosed primary hyperparathyroidism is referred for surgical assessment. She has had polydipsia, polyuria and constipation and abdominal discomfort. O/E 37C, 100/80, HR99, RR 14, SpO2100% Confused, JVP 1cm ASA weak pulses ABD unremarkable EKG: short QT, prolonged PR interval
Case 5 What is electrolyte disturbance? Hypercalcemia What are the most likely causes? Hyperparathyroidism, immobility, Pagets, Addisons, Neoplasms, xs Vitamin D, A, Sarcoidosis, Calcium supplementation, thiazides What is the acute management strategy? Volume expansion with NS +/- lasix, bisphosphonates, calcitonin, steroids
Case 6 45M presents with profound weakness in setting of chronic diarrhea. Background Alcohol Abuse P/E is unremarkable EKG: Prolonged QTc interval
Case 6 What are the possible electrolyte disturbances? Hypokalemia, hypomagnesiumia, hypophosphtemia, hypernatremia What is the acute management strategy? replace with supplemental magnesium and potassium phosphate fluid therapy
Things you don't want to hear during surgery: 5. Damn, there go the lights again... 4. "You know, there's big money in kidneys. Heck, the guy's got two of them." 3. Everybody stand back! I lost my contact lens! 2. This patient has already had some kids, am I correct? 1. Nurse, did this patient sign the organ donor card? Things you don't want to hear during surgery: 5. Damn, there go the lights again... 4. "You know, there's big money in kidneys. Heck, the guy's got two of them." 3. Everybody stand back! I lost my contact lens! 2. This patient has already had some kids, am I correct? 1. Nurse, did this patient sign the organ donor card?
The End