Chapter 17 Fluid and Electrolyte Imbalances medsurge

Intracellular (ICF)

Prevalent cation is K+

➢ Prevalent anion is PO4 3

Plasma (ECF)

➢ Prevalent cation is Na+

➢ Prevalent anion is Cl−

Diffusion

Movement of molecules across a permeable membrane from high to low concentration

Facilitated diffusion

Uses carrier to help move molecules

Osmotic pressure

Amount of pull required to stop osmotic flow of water

➢ Osmolarity measures the total mOsm/L of solution

➢ Osmolality measures the number of mOsm/kg of water

Normal plasma osmolality

280- 295 mOsm/kg

water deficit

Greater than 295 mOsm/kg

water excess

Less than 275 mOsm/kg

Plasma Osmolality calculation

(2 × Na) + (BUN / 2.8) + (glucose /18)

Isotonic

same as cell interior

Hypotonic

solutes less concentrated than in cells/ hypoosmolar

Hypertonic

solutes more concentrated than in cells/ hyperosmolar

Hydrostatic pressure

➢ Force of fluid in a compartment

➢ Blood pressure generated by heart’s contraction

-Pushes water out of the blood vessel (like squeezing a water bottle).

Oncotic pressure

➢ Colloid osmotic pressure

➢ Osmotic pressure caused by plasma proteins

-Pulls water into the blood vessel (because proteins act like magnets).

IV Fluid and Electrolyte Replacement

Purposes

➢ Maintenance • When oral intake is not adequate

➢ Replacement • When losses have occurred or are ongoing

 Types of fluids categorized by tonicity

Edema

➢ Shifts of plasma to interstitial fluid

➢ Elevation of venous hydrostatic pressure

➢ Decrease in plasma oncotic pressure

➢ Elevation of interstitial oncotic pressure

First spacing

Normal distribution in ICF and ECF

-normal

Second spacing

Abnormal accumulation of interstitial fluid (edema)

-edema (swelling)

Third spacing

Fluid is trapped where it is difficult or impossible for it to move back into cells or blood vessels

-Fluid stuck somewhere it shouldn’t be (like belly swelling)

Hypotonic IV Fluids

➢ Lower osmolality when compared to plasma

• Dilutes ECF

➢ Water moves from ECF to ICF by osmosis

➢ Good maintenance fluids

➢ Also used to treat hypernatremia

➢ Monitor for changes in mentation

-(make water go into cells)

-Used for dehydration inside cells.
-Watch for confusion.

IV Fluids D5W

 Technically isotonic (when in bag but hypotonic once infused in the body)

➢ Dextrose quickly metabolizes

➢ Net result free water

 Provides 170 cal/L

 Used to replace water losses, helps prevent ketosis

IV Fluids Isotonic

➢ Similar osmolality to ECF

• Expands only ECF

➢ No net loss or gain from ICF

➢ Ideal to replace ECF volume deficit

(stay in bloodstream)

• Good for low blood volume

IV Fluids Normal Saline

0.9% saline, NSS

 Isotonic

 Slightly more NaCl than ECF

 Used when both fluid and sodium lost

 Only solution used with blood

IV Fluids Lactated Ringer’s Solution

 Isotonic

 Contains sodium, potassium, chloride, calcium and lactate

 Expands ECF—ideal for surgery, burns and GI losses

 Contraindicated with liver problems, hyperkalemia, and severe hypovolemia

Hypertonic IV Fluids

➢ Higher osmolality compared with plasma

➢ Draws water out of cells into ECF

➢ Require frequent monitoring of

• Blood pressure • Lung sounds • Serum sodium levels

-Use for low sodium or swelling.

IV Fluids D5 ½ NS

Hypertonic

 Common maintenance fluid

 Replaces fluid loss  KCl added for maintenance or replacement

IV Fluids D10W

Hypertonic  Provides 340 kcal/L  Provides free water but no electrolytes  Limit of dextrose concentration that may be infused peripherally

Colloids

Stay in vascular space and increase oncotic pressure

 Affect blood coagulation, by interfering with coagulation factor VII

Stay in bloodstream and pull water in

CVADs

Catheters placed in large blood vessels

➢ Subclavian vein, jugular vein

 3 main types ➢ Centrally inserted catheters ➢ Peripherally inserted central catheters (PICCs) ➢ Implanted ports

Useful for patients with limited peripheral vascular access or need for long-term vascular access

Centrally Inserted Catheter (CVC)

Inserted into a vein in the chest or abdominal wall with tip resting in distal end of superior vena cava

 Nontunneled or tunneled

 Dacron cuff anchors catheter and decreases incidence of infection

CVADs Advantages

Immediate access ➢ Reduced venipunctures ➢ Decreased risk of extravasation

CVADs disadvantages

➢ Increased risk of systemic infection ➢ Invasive procedure

longterm (tunneled) catheters

➢ Hickman ➢ Broviac ➢ Groshong

Groshong

Maintain with normal saline

Hickman & Broviac

Flushed with heparin solution

PICC

Central venous catheter inserted into a vein in arm

 Single- or multi-lumen, nontunneled

 For patients who need vascular access for 1 week to 6 months

 Cannot use arm for BP or blood draw

PICC Advantages

Lower infection rate ➢ Fewer insertion-related complications ➢ Decreased cost

PICC disadvantages

➢ Deep vein thrombosis ➢ Phlebitis

Implanted Infusion Port

Central venous catheter connected to an implanted, single or double subcutaneous injection port

 Port is titanium or plastic with self-sealing silicone septum  Port is accessed using a special non-coring needle with a deflected tip

Drugs are placed in the reservoir of the port through skin by a direct injection or through injection into an established IV line

• Used for chemotherapy

Implanted Infusion Port Advantages

Good for long-term therapy ➢ Low risk of infection ➢ Cosmetic discretion

Midline Catheters

Peripheral catheters

➢ 3 to 8 in long

➢ Single- or double-lumen

Like a PICC but doesn’t reach central veins

 Use and care similar to PICC

 May stay in place up to 4 weeks

Fluid shifts when

• Blood pressure is too high

• Protein is too low

• Pressure in tissues becomes higher

Hypovolemia

Fluid Volume Deficit

Abnormal loss of body fluids, inadequate fluid intake, or plasma to interstitial fluid shift • Can be r/t hemorrhage, vomiting, diarrhea, burns, pancreatitis, diuretics • Minimal urine output • Dehydration • Loss of pure water without corresponding loss of sodium

Sodium

136 to 145 mEq/L

Plays a major role in
• ECF volume and concentration
• Generating and transmitting nerve impulses
• Muscle contractility
• Regulating acid-base balance

Calcium

9.0 to 10.5 mg/d

Functions
• Formation of teeth and bone
• Blood clotting
• Transmission of nerve impulses
• Myocardial contractions
• Muscle contractions

Potassium

3.5 to 5.0 mEq/L

Major ICF cation
Necessary for
• Resting membrane potential of
nerve and muscle cells
• Cellular growth
• Maintenance of cardiac rhythms
• Acid-base balance

Magnesium

1.3 to 2.1 mEq/L
Cofactor in enzyme for metabolism of
carbohydrates
• Required for DNA and protein
synthesis
• Blood glucose control
• BP regulation

if high calcium high

Chloride

98 to 106 mEq/L

Phosphorus

3.0 to 4.5 mg/dL

Primary anion in ICF
• Essential to function of muscle (esp. cardiac), red blood
cells, and nervous system

-Involved in acid-base buffering system, ATP production,
cellular uptake of glucose, and metabolism of
carbohydrates, proteins, and fats

Reciprocal relationship with calcium (inverse relationship if high calcium low)

ECF volume deficit (Hypovolemia)

Fluid imbalance
• Impaired cardiac output
• Acute confusion
• Potential complication: Hypovolemic shock

ECF volume excess (Hypervolemia)

Fluid imbalance
• Impaired gas exchange
• Impaired tissue integrity
• Activity intolerance
• Disturbed body image
• Potential complications: Pulmonary edema, ascites

Hypernatremia Treatment

Causes hyperosmolality leading to cellular dehydration
• Primary protection is thirst
-Primary water deficit— replace fluid orally or IV with isotonic (NSS) or hypotonic fluids

-dilute with sodium-free IV fluids (D5W) and promote
sodium excretion with diuretics
• Decrease sodium level slowly to avoid
causing cerebral edema and neurologic
complications

Hyponatremia Treatment (If the cause is water excess)

Causes hypoosmolality

Fluid restriction may be only treatment
• Loop diuretics and demeclocycline
• Severe symptoms (seizures): Give small amount of IV hypertonic saline solution (3% NaCl)

Hyponatremia Treatment (If the cause is abnormal fluid loss)

Fluid replacement with isotonic sodium-containing solution
• Encouraging oral intake
• Withholding diuretics

Hyperkalemia implementation

Stop oral and parenteral K+ intake
• Increase K+ excretion (diuretics, dialysis, Veltessa and/or Kayexalate)
• Force K+ from ECF to ICF by IV insulin

Monitor BG level when giving insulin.
• Stabilize cardiac cell membrane by administering calcium gluconate
IV. Monitor BP for SE of hypotension.
• Use continuous ECG monitoring

Hypokalemia implementation

KCl supplements orally or IV
• Always dilute IV KCl
• NEVER give KCl via IV push or as a bolus
• Give slowly. Should not exceed 10 mEq/hr
• Use an infusion pump
• Continuous cardiac monitor
• Urine output should be 0.5mL/kg/hr to ensure renal efficiency

Hypercalcemia Treatments

Low calcium diet
• Increased weight-bearing activity
• Increased fluid intake (3 to 4L/day) to promote renal excretion
• Cranberry or prune juice to promote urine acidity to prevent stone formation
• Hydration with isotonic saline infusion
• Bisphosphonates IV—gold standard
• Calcitonin

Hypocalcemia treatment

Calcium and Vitamin D food and supplements
• IV calcium gluconate
• Rebreathe into paper bag to slow breathing and control muscle spasm and tetany
• Treat pain and anxiety to prevent hyperventilation-induced respiratory alkalosis

Hypermagnesemia Management

Restrict magnesium intake in high-risk
patients
• IV calcium gluconate, if symptomatic. CaGL will oppose the effects of Mg on heart
• Monitor cardiac status
• Fluids and IV furosemide to promote urinary excretion
• Dialysis, if impaired renal function

Hypomagnesemia Management

Oral supplements
• Increase dietary intake
• Parenteral IV or IM magnesium when severe. Monitor VS since administration can lead to hypotension and cardiac or respiratory arrest