Vital Signs -- DDx

Question 1

Your patient is Hypoxic –

What do you think is going on?

(DDx for Hypoxia?)

Answer 1

Causes of hypoxia – are classified into 5 groups

(then another one… low delivery of O2 – supply vs demand – decreased cardiac output):

1. Low inspired fractional concentration of oxygen (low Fio2)
   
   • nml D (A-a) O2
2. Alveolar hypoventilation
   
   • nml D (A-a) O2, increased PaCO2
     
     • Airway obstruction; kinked ETT, mucus plug
     • Ventilator failure/disconnect
     • Respiratory depression (drugs)
     • Respiratory failure (paralysis)
3. Diffusion impairment (aka Impairment of diffusion across blood-gas membrane)
   
   • increased D (A-a) O2
     
     • Emphysema
     • ILD
     • Pulm fibrosis
     • PPHTN
4. Shunt
   
   • increased D (A-a) O2, no change w/ increased Fio2
     
     • Atelectasis
     • Aspiration
     • decreased FRC (obesity) or increased CC (age)
     • One lung ventilation
     • Pneumonia
     • PTX
     • Pulm edema:
       
       • CHF, sepsis, IVF, NPPE, TRALI
     • PE/other embolus
     • Severe bronchospasm
     • R to L intracardiac shunts
       
       • Cyanotic defects: ToF, TAPVR, TGV
       • Eisenmenger’s
5. Ventilation-perfusion inequality (V/Q mismatch)
   
   • increased D (A-a) O2, nml Svo2, improves w/ increased Fio2
     
     • Airway (bronchospasm, asthma, COPD)
     • Alveolar (PNA, CHF)
     • Vascular (PE)
     • OLV
     • decreased FRC or increased CC
6. DO2/VO2 imbalance
   
   • increased D (A-a) O2
     
     • Low CO (venous admixture)
       
       • High SVR
       • EBL
       • Cardiogenic shock
       • Histotoxic hypoxia
         
         • SNP
       • Anemia
         
         • CO poisoning
         • Met-Hgb
       • Low P50

Question 2

Your patient is Bradycardic –

What do you think is the cause?

(DDx of Bradycardia)

Answer 2

• HTN/ICP
  
  • elevated ICP (?)
• Myocardial dz
• Hypoxia (O2 lack)
• Anesthesia
• Vagal
• Acidosis
• Drugs

Question 3

Your patient is Tachycardic –

What do you think is the cause?

(DDx of Tachycardia)

Answer 3

High Pulse FAST

• Hypoxia
• Hypovolemia
• Hypotension
• Hyperthermia
• Pain
• Pheo
• PE
• Fever
• Anemia
• Sepsis
• Thyroid

• VS –
  
  • Hypoxia, Hypotension, Hyperthermia, Fever
• Volume Status –
  
  • Hypovolemia, Anemia
• Pain
• Sepsis
• Lungs –
  
  • PE
• Endocrine –
  
  • Pheo, Thyroid