What labs should be ordered for a 50-year-old man involved in a motor vehicle accident?

Laboratory Testing for a 50-Year-Old Man in Motor Vehicle Accident

Order a complete blood count with serial hemoglobin/hematocrit measurements, comprehensive metabolic panel, serum lactate, arterial blood gas for base deficit, coagulation studies (PT/INR, aPTT, fibrinogen, platelets), and type and screen immediately upon arrival. 1

Essential Initial Laboratory Tests

Hematologic Assessment

• Complete blood count (CBC) with hemoglobin and hematocrit must be obtained immediately, but recognize that a single normal value does not exclude significant bleeding due to delayed fluid shifts from the interstitial space 2, 1
• Serial hemoglobin/hematocrit measurements are critical—repeat every 2-4 hours in unstable patients to detect ongoing hemorrhage, as initial values may be falsely reassuring 1
• Platelet count should be maintained above 100,000/mm³, particularly if traumatic brain injury is suspected or ongoing bleeding is present 1

Shock and Perfusion Markers

• Serum lactate is a highly sensitive marker for tissue hypoperfusion and hemorrhagic shock severity—levels above 4 mmol/l are associated with a four-fold increased mortality risk 2
• Base deficit from arterial blood gas provides complementary information about global tissue acidosis; values below -6 mEq/l significantly increase mortality risk 2
• Both lactate and base deficit should be measured independently as they do not strictly correlate with each other but together provide superior assessment of shock severity 2, 1
• Serial lactate measurements are prognostic—failure to normalize within 24-48 hours predicts organ failure and death 2

Coagulation Assessment

• PT/INR, aPTT, fibrinogen, and platelet count should be obtained early and repeated to detect trauma-induced coagulopathy, which occurs in 25-35% of trauma patients and dramatically increases mortality 2, 1
• Viscoelastic hemostatic assays (TEG/ROTEM) should be performed when available to better characterize coagulopathy patterns and guide targeted hemostatic therapy—these whole blood assays are superior to standard plasma-based tests for trauma patients 2, 1
• Do not rely on INR and aPTT alone to guide hemostatic therapy, as they only monitor the initiation phase of coagulation (first 4% of thrombin production) 2

Metabolic and Organ Function

• Comprehensive metabolic panel including electrolytes, creatinine with eGFR, glucose, liver enzymes (AST, ALT), and total bilirubin to assess for occult organ injury 1
• Ionized calcium should be monitored and corrected in bleeding trauma patients 1
• For suspected thoracoabdominal injuries, add pancreatic enzymes (amylase, lipase) and urinalysis 1
• For chest trauma, consider cardiac biomarkers (troponin, CK-MB) to evaluate for myocardial contusion 1

Critical Pitfalls to Avoid

Do not dismiss a normal initial hemoglobin/hematocrit—significant blood loss may not be reflected immediately due to the time required for fluid equilibration from the interstitial space 2, 1. This is the most common laboratory pitfall in trauma.

Do not use single measurements—serial assessments are essential for detecting ongoing bleeding and monitoring resuscitation adequacy 2, 1.

Do not overlook coagulopathy—25-35% of trauma patients present with coagulopathy on arrival, and this is associated with several-fold increased mortality 2. Early detection and correction are critical.

Special Considerations for This Patient

At age 50, this patient falls into a higher-risk category where:

• Systolic blood pressure <110 mmHg may represent shock (compared to <90 mmHg in younger patients) 2
• Occult hypotension with decreased perfusion may be present despite "normal" vital signs 2
• Lower-energy mechanisms can cause more severe injury than expected 2

If the patient is on anticoagulants or has bleeding disorders, he is at extremely high risk for rapid deterioration, particularly with any head injury—this mandates immediate coagulation studies and aggressive monitoring 2.

Timing and Interpretation

All initial laboratory tests should be obtained immediately upon arrival with results available rapidly to guide resuscitation decisions 1. Establish a protocol for serial measurements every 2-4 hours in unstable patients or those requiring massive transfusion 1.

Resuscitation fluids will dilute blood components and affect laboratory values, particularly hemoglobin/hematocrit, so interpret trending values in the context of fluid administration 2, 1.