July 1

Fluids and electrolytes

Joel Topf, MDNephrology Attending

St. John Hospital

http://PBFluids.com

The lungs serve to maintain the composition of the extracellular fluid with respect to oxygen and carbon dioxide, and with this their duty ends. The responsibility for maintaining the composition of this fluid in respect to other constituents devolves on the kidneys. It is no exaggeration to say that the composition of the body fluids is determined not by what the mouth takes in but what the kidneys keep: they are the master chemists of our internal environment. Which, so to speak, they manufacture in reverse by working it over some fifteen times a day. When among other duties, they excrete the ashes of our body fires, or remove from the blood the infinite variety of foreign substances that are constantly being absorbed from our indiscriminate gastrointestinal tracts, these excretory operations are incidental to the major task of keeping our internal environments in the ideal, balanced state.

Homer W. Smith From Fish to Philosopher

Answer:The percentage of admissions that get either:

IV fluids or Diuretics

Question:What is 100%?

Answer:The percentage of hospital days that patients get electrolytes drawn

Question:What is 100%?

Fluids and electrolyte issues are ubiquitous

1324.4

10817

10634

3.8

The ability to screw up is ubiquitous

Fluids: Total body water

Ideal weight: Females: 45 kg Males: 50 kg

Adjusted weight: ideal weight + 0.4 (actual body weight – ideal weight)

+ 2.3 kg for every inch over 5 feet

67%28 L

25%11 L

8%3 L

Blood volume = 5 L

Hemoconcentration

Mr. Jones drank too much and puked his guts out.

On admission his hct is 65%. Up from a recent hematocrit of 40%.

How much water was lost from his vascular space?

€

RCVpre = RCVpostRCV = IVV ×Hct

IVVpre ×Hctpre = IVVpost ×Hctpost5L × 0.40 = IVVpost × 0.65

5L × 0.400.65

= IVVpost

3.1L = IVVpost

Intravenous fluids

Dextrose Saline Ringers Lactate

Plasma expanders

Crystalloids

Dextrose solutions The convention for naming dextrose

solutions is grams percent (g%) To convert this to conventional mg/dL

multiply the g% by 1,000 Example

D5W contains 5g of glucose per 100 mL or 50 g per liter (200 Kcal/liter) The glucose concentration of D5W is

5,000 mg/dL

Dextrose solutions The glucose concentration in D5W is so

high to make the fluid isosmotic to plasma To convert from mg/dL to mmol/L

Divide the mg/dL by the molecular weight of glucose (180) to get mmol/dL

Multiply by 10 to convert mmol/dL to mmol/L

5000 mg/dL180 mg/mmol

27.8 mmol/dL10 dL/L 277 mmol/L

Saline Isotonic saline is the primary fluid for

volume resuscitation Sodium concentration

154 mmol/L pH of 5.5

When given in large volumes can cause a non-anion gap (hyperchloremic) metabolic acidosis

Dilutional acidosis

Lactated ringers Contains Na, Cl, K, and

Ca at physiologic concentrations Do not use with

hyperkalemia Do not use with

hypercalcemia Lactate is used to

supply alkali Do not use with lactic

acidosis pH=6.6

The Contents Sodium: 130 mmol/L Chloride: 109 mmol/L Lactate: 28 mmol/lL Potassium: 4 mmol/L Calcium: 6 mg/dL

Dextrose

Saline

Ringers Lactate

Plasma expanders

Mr. Jones is down 1.9 L How much D5W will

it take to replace the intravascular volume?

Dextrose distributes in proportion to total body water. 8% of TBW is

intravascular 1.9/0.08 = 23.75 L

23.75 liters

Mr. Jones is down 1.9 L How much 0.9% NaCl

(or LR) will it take to replace the intravascular volume?

Saline distributes among extracellular compartments. 25% of ECC is

intravascular 1.9/0.25 = 7.6 L

7.6 liters

Mr. Jones is down 1.9 L How much

blood/albumin will it take to replace the intravascular volume?

Blood/albumin is limited to the intravascular space. 1.9/1.0 = 1.9 L

1.9 liters

What type of IVF would you use? Patient is post-op from a hysterectomy. She

had EBL of 280 mL and her current vitals are BP 113/78, HR 105.

Patient in the Shock-Trauma room of the ED after an MVA vs Peds. His BP is 78/40, HR 140 with a thready pulse.

Patient who is NPO due to resolving pancreatitis. Vital signs are stable. The patient is euvolemic.

Sodium is 163. The patient cannot tolerate oral liquid.

Bicarbonate drips Do not add bicarb to normal saline An amp of bicarb has 50 mmol Na per 50

mL (1000 mmol/L) Add bicarbonate to:

D5W: 3-4 amps per liter 0.45 NS: 1-2 amps per liter Sterile water: 3-4 amps per liter

Answer:The percentage of admissions that need both:

IV fluids and Diuretics

Question:What is very few?

Don’t give a drowning man a glass of water

Don’t use IVF and diuretics Except

Hypercalcemia Hyperkalemia

Proper use of diuretics: Loops Loop diuretics block the Na-K-2Cl co-

transporter in the thick ascending limb of the loop of Henle

They block chloride in the tubular fluid from binding So loop diuretics (like all diuretics except spironolactone)

must get from the blood into the tubular fluid Secretion in the proximal tubule Secretion is dependent on renal function

Must increase the dose as renal function deteriorates Age + BUN

Proper use of diuretics: Loops Loop diuretics block the Na-K-2Cl co-

transporter in the thick ascending limb of the loop of Henle

They block chloride in the tubular fluid from binding So the loop diuretic (like all diuretics except spironolactone)

must get from the blood into the tubular fluid Secretion in the proximal tubule Secretion is dependent on renal function

Must increase the dose as renal function deteriorates Age + BUN Cr x 20

Loop diuretic resistance Chronic use of loop diuretics results in

hypertrophy of distal convoluted tubule Increased distal reabsorption of sodium and

fluid attenuate diuretic response Addition of a thiazide diuretic can restore

loop sensitivity

SituationMechanism of diminished response

Therapeutic response

Renal failure Impaired delivery to tubular fluid Increased dose

Nephrotic SyndromeProtein binding in the urine. Sodium avid nephron

Increased dose

Heart Failure Sodium avid nephron Increased frequency

Cirrhosis Sodium avid nephron Increased frequency

Loop diuretic resistance

Furosemide drips High dose furosemide

causes Electrolyte abnormalities Ototoxicity Volume depletion

In a meta analysis Salvadore and Rey found continuous infusions for CHF: More diuresis Less ototoxicity No change in electrolyte

abnormalities

Give 40-80 mg bolus of furosemide

Start infusion at 20 mg/hour

Titrate drip to desired diuresis May need to repeat the

loading doses when titrating the drip

Maximum of 40 mg/hr

Salvador DR, Rey NR, Ramos GC, Punzalan FE.Cochrane Database Syst Rev. 2004;(1):CD003178

Proper use of diuretics: Thiazides Thiazide diuretics lose much of their

effectiveness with a GFR < 50 mL/min This can be overcome with higher doses 50-100 mg of HCTZ with GFR 30-50 200 mg of HCTZ with GFR < 30 Metolazone (Zaroxolyn)

2.5-20 mg daily Half-life is 2 days

Electrolyte Emergencies

Sodium is different Most ions must be regulated because of

direct effects of the ion. Arrhythmias from high (or low) potassium Weakness from high magnesium Tetany from low calcium

Sodium is not like that. The problems with high or low sodium have

little to do with direct effects of the ion. Disregulation of sodium causes changes in cell

volume.

The movement of water in the body

The movement of water into and out of cells is governed by tonicity (sodium):

intracellular compartment extracellular compartment

Why we care about osmolality Alterations in cell size disrupt tissue

function.

Low sodium: hyponatremia

Hyponatremia is defined as a sodium concentration less than 135 mEq/L. Pseudohyponatremia is when the

sodium concentration is low (< 135) but osmolality is high or normal.

True hyponatremia is when both the sodium and the osmolality are low.

Pseudohyponatremia: high osmolality Elevated glucose (or

mannitol) raise plasma tonicity which draws water from the intracellular compartment diluting plasma sodium.

Hillier TA, Abbott RD, Barrett EJ. Am J Med 1999; 106: 399-403.

Pseudohyponatremia: high osmolality

Correcting the sodium for hyperglycemia. Add 1.6 to the sodium for every 100 mg/dL the

glucose is over 100. Example: Na = 126 mEq/L. Glucose = 600 mg/dL:

600 - 100 = 500. So the glucose is five 100’s over 100 5 x 1.6 = 8 126 + 8 =134 True sodium equals 134 mEq/L To remember 1.6 think “Sweet 16”

Underestimates true adjusted sodium

Pseudohyponatremia: Normal osmolality Increased protein or lipids can cause a lab

error causing a falsely lowered sodium. Hyperlipidemia Hypercholesterolemia

TPN with lipids IV immunoglobulin infusions

True hyponatremia: water intake > water excretion

Intake Psychogenic

polydipsia

True hyponatremia: water intake > water excretion

Intake Psychogenic

polydipsiaExcretion

Renal failure ADH

SIADH CHF Volume depletion Cirrhosis Adrenal

insufficiency Hypothyroidism

Urin

e O

smol

ality

50

1200

Healthy Kidneys

Concentrated urine

Na+

Dilute urine

Na+

Urin

e O

smol

ality

50

1200

Healthy Kidneys

150

900

Chronic Kidney Disease

600

900

Excess ADH: • SIADH • CHF • Volume depletion

50

150

Absence of ADH: Diabetes insipidis

300

ESRD or acute renal failure

isosthenuria

Concentrated urine

Na+

600

900

Excess ADH: • SIADH • CHF • Volume depletion

Etiology of Hyponatremia: 3 steps to generating dilute urine

1.Delivery of water to the diluting segments of the nephron.2.Functional diluting segments.

3.Collecting tubule impermeable to water (lack of ADH)

1400

285

100 50

Failure to Generate dilute urine Lack of water

delivery to the diluting segments. Renal failure Volume deficiency Cirrhosis Heart failure Nephrotic syndrome

Failure to Generate dilute urine Ineffective solute

reabsorption in the diluting segments: Thick ascending limb

of the loop of Henle (TALH)

Distal convoluted tubule.

Diuretics Non-oliguric ATN

Failure to Generate dilute urine Permeable collecting

ducts (ADH) Volume related ADH SIADH

Drug induced Paraneoplastic CNS Pulmonary disease

Adrenal insufficiency Hypothyroidism

Implications of hyponatremia

Adrogué and Madias NEJM 2000;342:1581.

The problem with compensationThe starting point is after compensation has reduced the amount of intracellular solute and the ICPNow, an over-eager intern sees the low sodium and starts an infusion of 3% NaCl to raise the sodium to normal.

Sodium108Sodium134

The sodium draws water from the inside of the cells causing the brain to shrivel.

The problem with interns

This causes osmotic brain damage. Central pontine myelinolysis. This is lethal.

Damned if you do. Without treatment patients

have cerebral edema. Correction of sodium puts

patients at risk for OBD

To treat or not to treat?

T. BerlDamned if you don’t.

That is the question.

Symptomatic vs. Asymptromatic Uncompensated,

symptomatic Treat aggressively with

3% saline Critical care or

nephrology consult. Compensated,

asymptomatic Treat conservatively Water restriction Conivaptan / Tolvaptan Demeclocycline Lasix

Symptoms Mental status changes Nausea Vomiting Headache Movement abnormalities Seizures Hypoxia/respiratory failure

Symptomatic vs. Asymptromatic Use the etiology of hyponatremia as a clue to

duration of hyponatremia Patients with long standing disease processes are

more likely to be chronic: SIADH CHF Cirrhosis

Likely to cause acute hyponatremia: Psychogenic polydipsia (water intoxication) Thiazide diuretics Post-operative hyponatremia Marathons

COMMON

RARE

Clock and calendar are unreliable measures of

chronicity

Early aggressive therapy Late aggressive therapy Conservative therapy

Ayus JC, Arieff AI. JAMA 1999; 281: 2299-2304.

Chronic vs acute

Prospectively collected case series of 53 postmenopausal women. Average duration of hyponatremia: 5.2 days All had severe neurologic symptoms.

Symptomatic vs Asymptomatic

Conservative therapy for asymptomatic hyponatremia

Do no harm. Fluid restrict the patient.

Check the urine Na plus K If it is greater than the serum Na,

furosemide may help. Speed limit

0.5 mmol/L/hr No more than 12 mmol in the first day.

Renneboog B, Musch W, Et al. Am J Med 2006; 119: 71 e1-8.

151 consecutive euvolemic hyponatremic patients admitted to through the ED

Na from 115 to 132 Excluded patients with CHF, acute

hyponatremia, or seizures N = 122

9.45 67.43

Renneboog B, Musch W, Et al. Am J Med 2006; 119: 71 e1-8.

Acute symptomatic hyponatremia In patients with neurologic symptoms

due to hyponatremia: Use 3% NaCl. Increase sodium until symptoms abate

or 6 mmol/L, which ever comes first.

Increase Na 12 mmol/L in the first 24 hours.Increase Na 12 mmol/L in the first 24 hours.

12

Change in sodium formula: The formula predicts serum

sodium following one liter of any infusion. Works equally well in

hyponatremia 3% NaCl

and hypernatremia D5W

In adults, using 3% NaCl the ∆Na should be pretty close to 10 mmol/L per liter

€

ΔNa =Naiv − NasTBW +1

⎧ ⎨ ⎩

⎫ ⎬ ⎭

Change in sodium following one liter of any IVF.TBW = kg x 0.6Na in 3% NaCl: 513Na in 0.9% NaCl: 154Na in 0.45% NaCl: 77Na in 0.225% NaCl: 39

Adrogué and Madias NEJM 2000;342:1581.

Change in sodium formula: Examples 46 yo AA female 3

days post-op from TAH develops seizures and is unresponsive. Na = 108 Weight = 65 kg

You prescribe 3% NaCl

1. For every liter of 3% the Na will rise 10.1 mmol/L

So 1 mmol/L per 100 cc of 3%2. Raise Na 6 mEq in 2 hours give

300 ml/hr for 2 hours or until symptoms resolve.

3. After that 50mL for 12 will increase serum Na by 6 mmol/L to get you to 12 mmol/L.

4. Check frequent serum Na, recheck change in Na calc.

€

ΔNa = Naiv − NasTBW +1

⎧ ⎨ ⎩

⎫ ⎬ ⎭

ΔNa =513−10865× 0.6( ) +1

⎧ ⎨ ⎩

⎫ ⎬ ⎭

ΔNa = 10.125

Change in sodium formula: Limitations

Under estimates change in sodium

Assumes no urine output The greater the urine

output the more inaccurate the formula

In 40% of people who overcorrect, there is documented diuresis

Assumes accurate calculation of total body water

€

ΔNa =Naiv − NasTBW +1

⎧ ⎨ ⎩

⎫ ⎬ ⎭

Change in sodium following one liter of any IVF.TBW = kg x 0.6Na in 3% NaCl: 513Na in 0.9% NaCl: 154Na in 0.45% NaCl: 77Na in 0.225% NaCl: 39

Mohmand HK, Issa D, Et al. Abstract ASN 2006Adrogué and Madias NEJM 2000;342:1581.

Fluids: Total body water

Hyponatremia summary The primary issues:

Is it true hyponatremia Check a spot glucose

If it is true then: To treat or not to treat?

Symptomatic: Treat with 3% Asymptomatic: fluid restrict

Tolvaptan / Conivaptan Demeclocycline Lasix and /or salt tablets

Hypernatremia Hypernatremia is defined as a sodium > 145 mEq/L. Hypernatremia is associated with increased hospital

mortality. Patients who present with hypernatremia typically get appropriate

therapy. In patients who develop hypernatremia while hospitalized don’t

get therapy as often.

Causes of hypernatremia Water excretion exceeds

water intake Two step process

Generation

Generation Gain of sodium Loss of water

Maintenance Maintenance

Inability to ingest water Without both of these

processes there cannot be hypernatremia.

Consequences and compensation

Treatment Provide water

Enteral water is preferred

D5W results in hyperglycemia

Note on D5W, since D5W distributes through the total body water 1 liter of D5W increases the intravascular space by only 83 mL

Use the change in sodium formula to calculate the fluid volume.

The amount of fluid TBW= kg x % body

water 0.7 for well hydrated

young males 0.6 for well hydrated

young females reduce by 0.1 for:

Obesity Elderly Dehydration€

Initial Na =168 mmol/L

ΔNa = Naiv +K iv −NasTBW +1

ΔNa = 0 + 0 −16842 +1

ΔNa = 3.9 ≈ 4

Each liter of D5 or free water lowers Na 4, so 6 liters will reduce the Na to 144.

Treatment For routine hypernatremia correct the fluid

deficit over 48 hours. Patients with DI have large ongoing free water

losses (200-300 mL/hr). Failing to account for these losses will result in a

failure to correct the hypernatremia. Many of these patients have poor perfusion.

Treat the shock and compromised perfusion without worrying about the Na.

After perfusion is restored treat the hypernatremia.