What Labs to Watch Out for as a Nurse

EP 108: What Labs to Watch Out for as a Nurse

We go through a lot of labs in the hospital, they are all important, but some are more important than others. As nurses face the pandemic, more and more people are getting sick [1].

It is important to check their labs to understand what is going on inside their bodies better. Here are nine of the most essential labs to watch out for.

We come up with a comprehensive list of the major lab values every nurse should know and why. 9 most important lab values

1. Potassium

Levels in adults: 3.5-5.2 mEq/L, Children: 3.4-4.7 mEq/L

    1. Potassium is important in maintaining electrolyte balance and is considered to be one of the labs to watch out for the most. It aids in nerve function and muscle contraction. It also helps our heartbeat stay regular.
    2. We use potassium levels to assess acidosis, AKI, CKD, dehydration, and certain therapeutic interventions.
    3. Hyperkalemia: K > 5.2
      • S&S: muscle weakness, nausea, vomiting, weakness, heart palpitations, cardiac dysrhythmias. 
      • Peaked T-waves, PR prolongation, and lose p waves.
      • Treatments:
        • IV glucose and insulin, NaHCO3, diuretics, Kayexalate, and dialysis.
    4. Hypokalemia: K < 3.5
      • S&S: Orthostatic hypotension, shallow respirations, confusion, decreased deep tendon reflexes (hammer on knee/elbow), loss of bowel sounds.
      • Depressed ST, flat or inverted T waves, U wave
      • Treatments:
        • IV/oral potassium, hold diuretics and digoxin.
  1. Magnesium

    1. 1.8 – 2.5 mg/dL
    2. Magnesium plays a role in nerve function, transferring and storing energy, regulation of parathyroid hormone PTH (which also plays a role in calcium levels).
    3. Hypermagnesemia: Mg > 2.5
      • S&S: lethargy, hypotension, Respiratory arrest, diminished deep tendon reflexes.
      • Prolonged PR and QT, widened QRS
      • Treatment: 
        • IV calcium, diuretics, and dialysis
    4. Hypomagnesemia: Mg < 1.8
      • Hypertension, irritability, hyperreflexia, and involuntary movements.
      • Torsades de pointes
      • Treatment:
        • Magnesium Sulfate, and Magnesium oxide. 
  2. Sodium

    1. 135 – 145 meq/L
    2. One of the most common labs to watch out for is sodium. It is important in nerve impulses, intracellular osmolality, promotes myocardial, smooth, and skeletal contractility. 
    3. Hypernatremia: Na > 145 meq/L
      • S&S: restless, agitation, fluid retention, edema, decreased urine output.
      • Treatment:
        • Isotonic or hypotonic solution (run slow because brain tissue is at risk for an intracellular fluid shift. 
    4. Hyponatremia: Na < 135 meq/L
      1. S&S: seizure, stupor, confusion, orthostatic hypotension, spasms, cramping.
      2. Treatment:
        • Hypovolemic Hyponatremia: give IV sodium chloride infusion to restore sodium and fluids. Hypertonic solution cal also be given, 3% Saline. 
        • Hypervolemic Hyponatremia: Restrict fluid intake, diuretics to excretion the extra water rather than sodium to help concentrate the sodium. 
        • Dialysis
  3. Calcium (serum)

    1. 8.6 – 10.3 mg/dL
    2. Helps regulate cardiac, smooth, and skeletal muscle contraction, impulse transmission, and cardiac automaticity and contractility.
    3. Hypercalcemia: Ca > 10.3
      • Muscle weakness, disorientation, absent reflexes, and kidney stones.
      • Shortened QT interval.
      • Treatment: 
        • Calcitonin, fluids, loop diuretics, IV bisphosphonates, and dialysis.
    4. Hypocalcemia: Ca < 8.6
      • Confusion, hyperreactive reflexes, muscle spasms, positive Trousseau’s (blow up BP cuff wait 3 min, is arm contracts it is positive), and Chvostek (Chvostek sign is a contraction of facial muscles provoked by lightly tapping over the facial nerve anterior to the ear as it crosses the zygomatic arch)
      • Treatment:
        • IV calcium Chloride, calcium gluconate
  4. Phosphorus

    1. 2.8 – 4.5 mg/dL
    2. Works as a buffer for acid-base balance, aids in muscle, neurological, and platelet function. 
    3. Hyperphosphatemia: P > 4.5 mg/dL
      • confusion, hyperactive reflexes, muscle spasms, positive Trousseau and chvostek.
      • Treatment: 
        • Phosphate binding drugs (PhosLo, removes P via stool), and dialysis.
    4. Hypophosphatemia: < 2.8 mg/dL
      • Respiratory depression, rhabdomyolysis, osteomalacia (weakened bones), irritability, decrease platelet aggregation, and immune suppression. 
      • Treatment:
        • IV Na2PO4 with vitamin D
  5. ALT/AST

    1. ALT

      • 29 to 33 units/L for males and 19 to 25 units/L
      • Part of the liver function test is used to evaluate the liver. 
      • The highest concentrations are found in the liver and in smaller concentrations in the kidneys, heart, spleen, pancreas, red blood cells, and skeletal muscle
      • A very sensitive test can increase as much as 50x
        • The rationale for the lab is to assess liver disease or damage. 
    2. AST

      • 20-40 units/L for males and 15-30 unit/L
      • AST is an enzyme catalyst that is part of the Krebs cycle. 
      • AST exists in large amounts in the liver and myocardial cells, in smaller amounts located in skeletal muscle, kidneys, pancreas, brain, and red blood cells
        • Used as an indicator of cellular damage in liver disease. 
  6. Creatinine

    • 0.6–1.2 mg/dL
    • Creatinine is another lab that you should watch out for. The byproduct of creatine which is needed to produce the energy to contract our muscles. 
    • The kidney should normally be filtering out the substance.
    • High creatinine
      • This shows that there is an issue with kidney function. 
      • The glomerulus is doing a poor job.
  7. BUN

    2. 7-21 mg/dL
    3. Measures the Blood Urea Nitrogen.
    4. Shows us how well the kidneys are functioning.
      1. When elevated it is a cause for concern.
      2. Can show kidney failure, shock, or heart failure. 
  8. PT/INR

    1. PT: 10-12 seconds
    2. INR: 0.9-1.1 
    3. Prothrombin time and the International normalized ratio. 
    4. PT/INR assesses the extrinsic and common pathways. This allows you the see how fast prothrombin gets turned into thrombin. 
      • Extrinsic: clot formation that is activated when there is an external injury resulting in blood loss.
      • Intrinsic: clot formation that is activated when there is an internal injury. 
      • Common: where the intrinsic and extrinsic pathways meet from the clot. 
    5. These labs show how fast your blood clots.

Learn about the important lab values by watching the full episode here 👇👇👇


00:00 Intro
01:15 Welcome everybody
01:20 We made it to the Top 25
02:17 Plugging our NCLEX Study Guide book
02:40 9 Most Important Lab Values
03:40 Why electrolytes are important
05:03 Potassium
10:58 Magnesium
12:50 Sodium
17:02 Calcium
20:45 Phosphorus
23:04 ALT & AST
26:56 Creatinine
29:21 BUN
32:31 PT/INR
37:22 It’s a jam-packed show
37:33 End of show


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