Analyzing Lab Results for Hospitalized Patients

Introduction to Lab Analysis

• This lecture begins a series about analyzing laboratory results, especially for hospitalized patients.
• Lab results offer objective data, complementing subjective observations.
• A core skill for healthcare professionals is understanding/acting on lab results.

Key Lab Tests

• Complete Blood Count (CBC) will be covered in the series.
  • CBC includes WBC, hemoglobin, hematocrit, platelet count, and MCV.
• Comprehensive Metabolic Panel (CMP) or Chem 7 will be discussed.
  • CMP includes sodium, potassium, chloride, CO2 (bicarbonate), BUN, creatinine, and glucose.
• Focus is on how to read, interpret, and act on objective measurements.

Analogy: Flying a Plane

• Lab analysis is like using instruments when flying a plane.
• The patient is the passenger, while the healthcare provider is the pilot.
• Labs become essential in challenging situations when clinical view is limited.
• Proficiency in lab analysis is like being instrument-rated as a pilot.
• Lab results offer insights into the patient's internal state.
• Labs must be interpreted with consideration of the patient's clinical condition.

Importance of Context and Trending

• Identical lab values can have different implications depending on context.
• A sodium level of 140 could mean opposite things if it’s trending up or down.
• Lab results give a snapshot in time.
• Trending lab values over time offer more valuable information than a single data point.
• A sodium of 144 may seem normal; however, if previous values were successively lower (135, 139), then it indicates a trend towards hypernatremia.
• Proactive monitoring through trend analysis is essential, especially in critical care settings.

Ordering and Frequency of Labs

• Healthcare providers choose labs to order/frequency, unlike the fixed instruments on planes.
• Knowing when to order specific tests is crucial for diagnosis.
• Pulmonary embolism diagnosis requires ordering a CT angiogram.
• Anemia diagnosis requires ordering a CBC.
• Hypercapnia diagnosis requires ordering an ABG.

Lab Errors

• Lab errors can occur, with a published error rate of about 0.45%.
• Errors often come from issues in blood drawing/sample mix-ups, not the lab machines.
• A sudden, clinically inconsistent lab result should raise suspicion of error.
• Unlike pilots, healthcare providers must correlate lab values with clinical findings.
• If a lab result doesn't align with the clinical picture, repeat the test to confirm.

Factors Affecting Lab Accuracy

• Drawing blood near an IV line can lead to inaccurate results.
  • Glucose levels can be falsely elevated when drawing blood near D5 infusion.
  • Potassium levels can be falsely elevated when drawing blood near potassium infusion.
• Drawing blood from a central line without discarding enough initial blood can skew results.
• Suspected hyperkalemia can be confirmed via EKG by looking for peaked T-waves.
• Acting on a false hyperkalemia result can lead to hypokalemia if treated unnecessarily.

Key Takeaways

• Objective measurements (labs) should complement clinical impressions.
• Trending lab data is more informative than single data points.
• Verify results that don't align with the clinical picture.
• Think about what you need to know from the patient, then order blood tests.
• Consider how often to monitor lab values, thinking about expected changes.
• There should definied outlier thresholds, specifically how low or high a result must be before intervention.
• A hemoglobin level below 7 may warrant a blood transfusion.