BASIC FLUIDS AND ELECTROLYTES

Douglas P. Slakey

Why ?

Essential for surgeons (and all physicians) Based upon physiology

Disturbances understood as pathophysiology

To Encourage Thought Not Mechanical Reaction

Most abnormalities are relatively simple, and many

iatrogenic

It’s All About Balance

Gains and Losses Losses

Sensible and Insensible Typical adult, typical day

Skin 600 ml Lungs 400 ml Kidneys 1500 ml Feces 100 ml

Balance can be dramatically impacted by illness and medical care

Fluid Compartments

Total Body Water Relatively constant Depends upon fat content and varies with age

Men 60% (neonate 80%, 70 year old 45%) Women 50%

TOTAL BODY WATER60% BODY WEIGHT

ICF

2/3

Predominant solute

K+

ECF

1/3

Predominant solute

Na+

H2O

I LOVE SALT WATER!

(mEq/L) Plasma IntracellularNa 140 12K 4 150Ca 5 0.0000001Mg 2 7Cl 103 3

HCO3 24 10Protein 16 40

Electrolytes

Fluid Movement

Is a continuous process Diffusion

Solutes move from high to low concentration Osmosis

Fluid moves from low to high solute concentration. Active Transport

Solutes kept in high concentration compartment Requires ATP

Movement of Water

Osmotic activity Most important factor Determined by concentration of solutes

Plasma (mOsm/L)

2 X Na + Glc + BUN

18 2.8

Third Space

Abnormal shifts of fluid into tissues Not readily exchangeable Etiologies

Tissue trauma Burns Sepsis

Fluid Status

Blood pressure Check for orthostatic changes Physical exam Invasive monitoring

Arterial line CVP PA catheter Foley

Case 1

6 month old boy, born full-term Developed worsening vomiting during the

past week Today he is listless, irritable, not tolerating

oral intake Pulse 145, BP 70/50 Diaper is dry, anterior fontanel depressed

Case 1 Labs

149 92 12

2.8 40 0.8

15

4520012.3

Case 1 F & E Problem List

Hypovolemia Hypernatremia Hypokalemia Alkalosis

149 92 12

2.8 40 0.8

Volume Deficit

Most common surgical disorder Signs and symptoms

CNS: sleepiness, apathy, reflexes, coma GI: anorexia, N/V, ileus CV: orthostatic hypotension, tachycardia with

peripheral pulses Skin: turgor Metabolic: temperature

DehydrationChronic Volume Depletion

Affects all fluid components

Solutes become concentrated

Increased osmolarity

Hct can increase 6-8 pts for 1 L deficit

Patients at risk:

Cannot respond to thirst stimuli

Diabetes insipidus

Treatment: typically low Na fluids

HypovolemiaAcute Volume Depletion

Isotonic fluid loss, from extracellular compartmentDetermine etiology

Hemorrhage, NG, fistulas, aggressive diuretic therapyThird space shifting, burns, crush injuries, ascites

Replace with blood/isotonic fluid» Appropriate monitoring

» Physical Exam» Foley (u/o > 0.5 ml/kg/min)» Hemodynamic monitoring

Treatment – Patient weight is 12 kg

Fluid choice? Replace volume Replace Cl

How to order “Bolus”

Think about rate over time Adequate access important

What would maintenance fluid choice and rate be? 4-2-1 rule

Why not replace K right away?

Acid – Base Balance

Acidosis May result from decreased perfusion i.e.

decreased intravascular volume K will move out of cells

Alkalosis Complex physiologic response to more chronic

volume depletion i.e. vomiting, NG suction, pyloric stenosis, diuretics K will move intracellular

Paradoxical Aciduria

Na

Cl

Na

H

K

Loop of Henle

HypochloremicHypovolemia

Case 1 When should we operate?

Need to wait until adequately resuscitated Why

Monitor by: Normalized vital signs Good urine output Normalized labs

Case 2

64 year old, had colon resection 5 days ago “doing well” ….until…. Suddenly develops atrial fibrillation with rapid

ventricular response P 120, irregular; BP 115/70; RR 20 Temp 38.7 Confused, anxious

Case 2 Labs

128 100 12

3.0 22 0.8

10

3018016.3

Mg 1.1

Case 2

Diagnoses?

New onset A fib, why?

Hypervolemia Hyponatremia Hypokalemia Hypomagnesemia Anemia

Case 2

Why does patient have hypervolemia?

Increased Antidiuretic Hormone (ADH)

Causes Surgical stress (physiologic) Cancers (pancreas, oat cell) CNS (trauma, stroke) Pulmonary (tumors, asthma, COPD) Medications

Anticonvulsants, antineoplastics, antipsychotics, sedatives (morphine)

Hyponatremia – how to classify

Na loss True loss of Na Dilutional (water excess) Inadequate Na intake

Classified by extracellular volume Hyovolemic (hyponatremia)

Diuretics, renal, NG, burns Isotonic (hyponatremia)

Liver failure, heart failure, excessive hypotonic IVF

Hypervolemic (hyponatremia) Glucocorticoid deficiency, hypothyroidism

Patient was receiving maintenance Fluids

D5 0.45NS + 20 mEq KCl/L at 125 ml/hr

How much Sodium is Enough???

NS 0.9% = 9 grams Na per liter

0.45 NS = 4.5 grams per liter 125 ml/hour = 3000 ml in 24 hours 3 liters X 4.5 grams Na = 13.5 GRAMS Na!

(If 0.2 NS: 3 liters X 2 grams Na = 6 grams Na)

Case 2 - How to treat

A fib: ACLS protocol Correct electrolytes

Replace Mg and K

Decrease volume, fluid restriction

Case 3

23 year old with jejunostomy Had colon and ileum resected due to injury

Tolerates some oral nutrition, but has high output from jejunostomy (2.5 liters per day), therefore requires TPN

P 118, BP 105/60

Case 3 Labs

154 114 28

3.2 16 2.4

9.7

2838010.3

Glucose 213Mg 1.4

Current Problems

Hypovolemia Increased plasma osmolarity

2 X 154 + (213/18) + (28/2.8) = 329.8

Hypernatremia Renal insufficiency Acidosis

Case 3 - Hypovolemia

Fistula output High volumes can rapidly lead to dehydration Electrolyte composition can be difficult to

estimate Can send aliquot to laboratory

May need to be replaced separately from maintenance (TPN) fluids

Hyperglycemia

Hypernatremia

Relatively too little H2O Free water loss (burns, fever, fistulas) Diabetes insipidus (head trauma, surgery,

infections, neoplasm) Dilute urine (Opposite of SIADH)

Osmotic diuresis Nephrogenic DI

Kidney cannot respond to ADH Too much Na, usually iatrogenic

Hypernatremia

[0.6 X wt (kg)] X [Serum Na/140 - 1]

Free water deficit:

Example:Na 154, 60 kg person

(0.6 X 60) X [(154/140) - 1]36 X [1.1 -1]36 X 0.1 = 3.6 Liters

Case 3 – How to Treat

Correct hyperglycemia Replace pre-existing volume deficits Reduce ostomy output if possible What to do with:

Acidosis? Hypokalemia?

154 114 28

3.2 16 2.4

Case 4

58 year old, had a recent kidney transplant Laboratory calls with critical value:

Potassium 5.9

What to do?

Case 4

Evaluate the patient Exam ECG Order repeat labs

Hyperkalemia - Common Causes

Spurious Blood drawn above running IV Underlying disease

Renal failure Rhabdomyolysis

Associated medications Too much K+, ACE inhibitors, beta-blockers,

antibiotics, chemotherapy, NSAIDS, spironolactone

Treatment Mild: dietary restriction, assess medications Moderate: Kayexalate

Do not use sorbitol enema in renal failure patients Severe: dialysis

Potassium and Ph

Normally 98% intracellular

Acidosis Extracellular H+ increases, H+ moves

intracellular, forcing K+ extracellular

Alkalosis Intracellular H+ decreases, K+ moves into cells

(to keep intracellular fluid neutral)

Hyperkalemia - Treatment

Emergency (> 6 mEq/l) Monitor ECG, VS Calcium gluconate IV (arrhythmias) Insulin and glucose IV Kayexalate, Lasix + IVF, dialysis

Mild to Moderate Mild: dietary restriction, assess medications Moderate: Kayexalate

Do not use sorbitol enema in renal failure patients Severe: dialysis

The End

Makani U’i

Remember JVD?