Fluids, Solutions, and Serum Values

Fluids and Solutions

• Fluids are solutions containing a solvent and solute.

Fluid Compartments

• Extracellular fluid (ECF) accounts for 20% of body fluid.
  • The ECF includes Interstitial fluid (11-12L), Intravascular fluid (3L), and Transcellular fluid (1L).
• Intracellular fluid (ICF) accounts for 40% of body fluid.

Solutes: Serum Values

• Sodium normal range: 135-145 meq/L
  • Major cation in the ECF.
• Potassium normal range: 3.5-5.5 meq/L
  • Major cation in the ICF.
• Calcium normal range: 8.5-10.5 mg/dl
• Chloride normal range: 96-106 meq/L
  • Major anion in the ECF.
• Phosphate normal range: 2.5-4.5 mg/dl
  • Major anion in the ICF.
• Magnesium normal range: 1.3-2.5 mg/dl

Other Solutes

• Blood cells concentration of packed RBC: Hematocrit = 35-45%
• Glucose normal range: 70-110 mg/dl
• Creatinine normal range: 0.6-1.2 mg/dl
• BUN normal range: 10-20 mg/dl
• Includes Enzymes, Hormones, Nutrients and Gasses

Transport Mechanisms

• Simple diffusion is the movement of solutes from an area of higher concentration to lower concentration
• Facilitated diffusion is the movement of solutes from an area of higher concentration to lower concentration with the help of a carrier.
• Active transport is the movement of solutes from an area of lower concentration to higher concentration with the help of a carrier and energy (ATP).
• Osmosis is the movement of solvent from an area of lower concentration to higher concentration.
• Filtration is the movement of solutes and solvent from an area of higher pressure to lower pressure.

Hemodynamics

• Normal Hydrostatic Pressure (HP) is slightly higher than Oncotic Pressure (OP).
  • Fluid is pushed out of blood vessels (BV), increasing fluid in the interstitial space, which is then drained by lymphatics.
  • Lymphatics bring the fluid back to the BV.
  • Hydrostatic pressure (BP) pushes, while Oncotic pressure (proteins - albumin) pulls.

Fluid Regulation: Water Intake and Output (mL per 24 hours)

• Intake: Liquids (1600), Food (700), Metabolic water (200).
• Output: Urine (1500), Sweat (500), Exhaled air (300), Feces (200).

Fluid Disturbances

• Fluid Volume Excess (FVE)
• Fluid Volume Deficit (FVD)

Fluid Volume Excess (FVE)

• Defined as: excess fluid in the Extracellular Fluid (ECF).
• Etiology:
  • Decreased water loss (kidney failure, increased aldosterone, increased Antidiuretic hormone (ADH, SIADH)).
  • Increased water intake.
  • Increased Hydrostatic Pressure (HP), decreased Oncotic Pressure (OP), causing edema/fluid shifting.
• Results in edema, hypervolemia, hypertension, pulmonary edema, bipedal edema, ascites, and weight gain.
• Management:
  • Restrict fluid and sodium intake.
  • Monitor Input & Output (I&O) and Vital Signs (VS).
  • Weigh patient daily.
  • Administer diuretics (e.g., furosemide).
  • Dialysis
  • Manage the underlying cause.

Fluid Volume Deficit (FVD)

• Etiology:
  • Increased water loss (diarrhea, diuresis, diaphoresis, vomiting).
  • Decreased water intake.
  • Fluid shifting (burn patients).
• Leads to dehydration, causing dry skin and mucosa membranes, sunken eyes, tachycardia, poor skin turgor, and absence of tears.
• Management:
  • Increase fluid intake.
  • Monitor I&O and VS.
  • Weigh patient daily.
  • Manage the underlying cause.

Electrolyte Imbalances Include

• Hypernatremia and Hyponatremia
• Hyperkalemia and Hypokalemia
• Hypercalcemia and Hypocalcemia

Sodium Imbalances

• Hypernatremia, or increased serum sodium, is defined as more than 145 meq/L.
  • Etiology:
    • Hypernatremic Hypervolemia (FVE) is caused by sea drowning or increased aldosterone.
    • Hypernatremic Hypovolemia (FVD) is the most common.
    • Hypernatremic Euvolemia is when fluid volume is normal.
• Hyponatremia, or decreased serum sodium, is defined as less than 135 meq/L.
  • Etiology:
    • Hyponatremic Hypervolemia occurs in SIADH.
    • Hyponatremic Hypovolemia is caused by decreased aldosterone.
    • Hyponatremic Euvolemia is when fluid volume is normal.
• Management of Hypernatremia/Hyponatremia:
  • For FVE, restrict fluid and sodium, possibly increase sodium.
  • For FVD, increase fluid intake.
  • Monitor I&O and VS.
  • Weigh patient daily.
  • Promote safety.
  • Manage the underlying cause.

Potassium Imbalances

• Hyperkalemia, or increased serum potassium, is defined as a level more than 5.5 meq/L.
  • Etiology:
    • Decreased potassium excretion related to kidney failure or decreased aldosterone.
    • Increased potassium intake related to KCl IV bolus.
    • Potassium shifting out of the International Cellular Fluid (ICF) into the Extracellular Fluid (ECF) due to severe tissue damage (burn), prolonged surgery, or metabolic acidosis.
  • Affects muscles cells, causing cardiac arrest, peak, tall T waves (ECG readings), muscle weakness, diarrhea, and increased peristalsis.
• Management of Hyperkalemia:
  • Restrict potassium-rich foods.
  • Monitor potassium levels and ECG.
  • Administer calcium gluconate to antagonize the effect of potassium on cardiac cells.
  • Administer Glucose/Insulin IV to push potassium into the cells.
  • Administer Potassium excreting resin called Kayexalate.
  • Administer Sodium bicarbonate for metabolic acidosis.
  • Dialysis.
• Hypokalemia, or decreased serum potassium, is defined as a level less than 3.5 meq/L.
  • Etiology:
    • Increased potassium losses related to diarrhea, diuresis, or increased aldosterone.
    • Decreased potassium intake.
    • Potassium shifting from the ECF into the ICF in metabolic alkalosis.
  • Affects skeletal muscles, causing muscle weakness and paralysis Affects cardiac muscles, causing ECG presence of a U wave and affects smooth muscle.
• Management of Hypokalemia:
  • Increase potassium intake with fresh fruits.
  • Administer Potassium chloride (KCl) intravenously (IV) - incorporate with the IVF, monitor urine output, watch for phlebitis.
  • Monitor serum potassium and ECG

Calcium Imbalances

• Calcium functions include impulse transmission, muscle contraction, coagulation, bone formation, and teeth development.
• Calcium exists in two forms in the blood, including Ionized calcium (8.5-10.5 mg/dL = Ca++, this is the free form) and Unionized calcium which comes from calcium gluconate or calcium carbonate.
• Calcium regulation is dependent on Vitamin D to absorb calcium from the GastroIntestinal Tract (GIT).
  • Skin uses 7-hydroxycholesterol and sunlight to produce cholecalciferol (Vitamin D3) which is absorbed into blood, followed by conversion to 25-hydroxyvitamin D3 in the liver, followed by kidneys that activates 1,25-dihydroxycholecalciferol leading to calcium absorption in the GIT.
• Hypercalcemia, or increased calcium in the blood, is defined as calcium level more than 10.5 mg/dL.
  • Etiology includes tumor, hyperparathyroidism, and increased osteoclast activity.
  • Ionized Calcium results in irritability of nerves, therefore increased calcium can lead to decreased irritability of nerves leading to Central Nervous System (CNS) depression.
  • Decreased impulse transmission for the nerve to the muscle leads to muscle weakness and increased risk for stone formation (urolithiasis).
• Management of Hypercalcemia:
  • Restrict calcium-rich foods, manage the cause of hypercalcemia.
  • Increase oral fluid intake, promote safety, providing rest.
  • Prevent and manage complications.
• Hypocalcemia:
  • Etiology includes, decreased intake, decreased parathyroid hormone (PTH, total thyroidectomy), increased calcium loss (diuretics).
  • Decreased Vitamin D production/activation (kidney failure).
  • Massive blood transfusion increases citrate which binds with Calcium and respiratory alkalosis increases levels.
• Increased irritability of nerves leads to tetany (Chvostek's sign), carpopedal spasms (Trousseau's sign), paresthesia, and seizures.
• Management of Hypocalcemia:
  • Increase calcium rich foods, calcium supplements, Vitamin D, promote safety and manage the root cause.

Acid-Base Regulation

• Acid = with excess H+
• Base = with OH-
• Acids = Bases at Ideal Ratio of 1:20.
  • pH = 7.35-7.45
    • Low pH indicates acidosis.
    • High pH indicates alkalosis.
  • Regulation occurs via a Buffer system: a weak acid/weak base (blood with H2CO3 & HCO3) that Prevents sudden pH changes.
  • Kidneys compensate for respiratory acidosis by retaining HCO3 and removing HCO3 in respiratory acidosis.
  • Lungs compensate for metabolic acidosis by removing CO2 (hyperventilation - Kussmaul's breathing) and retain pCO2 in metabolic alkalosis (hypoventilation).

Acid-Base Imbalances

• Metabolic Acidosis Includes:
  • With high anion gap
  • With normal anion gap.
• Metabolic Alkalosis
• Respiratory Acidosis
• Respiratory Alkalosis

Metabolic Acidosis

• pH = low.
  • Decreased HCO3 occurs in normal anion gap.
  • Increased Acids occurs in high anion gap.
• Occurs from diabetic ketoacidosis, diarrhea, renal failure, shock, aspirin overdose, or sepsis.
• Signs and symptoms include headache, confusion, drowsiness, increased respiratory rate and depth, nausea, vomiting.
  • Peripheral vasodilation and decreased cardiac output when the pH drops to less than 7 and cold, clammy skin, dysrhythmias, and shock.

Metabolic Alkalosis

• pH = High, HCO3 = high, Acids = low.
  • Caused by Vomiting, Nasogastric suctioning, K wasting diuretics & Excessive alkali ingestion.
  • Primarily manifested by symptoms related to decreased calcium ionization with tingling of the fingers and toes, dizziness, and hypertonic muscles - The ionized fraction of serum calcium decreases in alkalosis because calcium combines with serum proteins.

Respiratory Acidosis

• Increased pCO2 related to COPD or lung disease
  • Low pH occurs with Increased PCO2, an increased ICP leads to altered LOC.

Respiratory Alkalosis

• Decreased pCO2 is caused by hyperventilation, shouting, crying, or panic attacks.

Urinary Tract Structures

• Structures: Kidney, Renal pelvis, Calyx, Ureter, Bladder, Internal sphincter, External sphincter, Urethra & Ureteral Orifice.

Renal Disorders

• Inflammatory.
• Obstructive.

Urinary Tract Infection (UTI)

• Upper UTI & Lower UTI

Lower Urinary Tract Infection

• Urethritis & Cystitis
  • Etiology: E. coli causes urethrovesical reflux leading to local inflammation, which results in irritative symptoms (dysuria, hypogastric pain, low back pain, frequency, and burning sensation on urination).
  • Diagnostic (Dtic) test results in a culture and sensitivity (C/S) and urinalysis with increased WBC and pyuria, bacteriuria.

Upper Urinary Tract Infection

• Pyelonephritis is inflammation of the renal pelvis.
• Glomerulonephritis is inflammation of the glomerulus.

Pyelonephritis

• Etiology: E. coli (lower UTI) that ascends into the renal pelvis.
  • Results in fever and chills, and pain along the costovertebral angle, flank.

Glomerulonephritis

• Inflammation of the glomeruli.

Kidney Stones (Urolithiasis, Nephrolithiasis, Renal Calculi)

• Appear when solutes in the urine precipitate and crystallize and depending on which solute precipitates a stone will form.
  • Could be Calcium Oxalate, Uric Acid, Struvite, Calcium Phosphate and/or Cystine

Urinary Tract Obstruction

• Nephrolithiasis causes CVA and flank pain.
• Ureter causes the most painful, colicky pain in the flank radiating to the thigh and genitalia.
• U. bladder causes low back or hypogastric pain.

Renal Impairment

• Acute Kidney Injury (AKI) is acute renal failure.
  • Sudden, reversible.
• Chronic Kidney Disease (CKD) is chronic renal failure.
  • Gradual and progressive impairment of kidney function and irreversible.

Chronic Kidney Disease (CKD) Stages

• Stage 1: GFR >/= 90 mL/min with normal or high GFR.
• Stage 2: GFR 60-89 mL/min (Mild).
• Stage 3: GFR 30-59 mL/min (Moderate).
• Stage 4: GFR 15-29 mL/min (Severe).
• Stage 5: GFR < 15 mL/min (End-Stage Renal Disease/ Renal Failure)

Management of CKD

• Medical Management.
• Dialysis.
• Renal Transplant.

Medical Management of CKD

• Anti-hypertensive (anti-HPN) drugs (ACE inhibitors, ARBs).
• Hyperkalemia management with calcium gluconate to antagonize the effect of potassium on the cardiac muscle, Kayexalate, Glucose IV, insulin IV to pull K into the cells, sodium bicarbonate for metabolic acidosis.
• Hyperphosphatemia management with Phosphate-binding agents such as AlOH (Amphojel).
• Hypocalcemia managed via calcium supplements.
• Anemia management includes erythropoietin and ferrous sulfate.

Dialysis

• Peritoneal Dialysis
• Hemodialysis