Question

A 52 year old woman weighing about 110 pounds) was admitted to the hospital for thrombophlebitis in her left leg. Her hospital course was uneventful until the second day, when she had an acute episode of shortness of breath and pain in the left chest. The patient had no previous history of cardiopulmonary disease. Her physical examination revealed bilateral expiratory wheezing and a tender, non-inflamed left calf. The chest radiograph was unremarkable. Vital signs were measured and an arterial blood gas sample was drawn. The results are shown in table 1 under sample 1. The patient was given 40% oxygen from a high flow system via face mask. Twenty minutes later, another arterial blood sample was drawn and the vital signs were measured. The results are shown in Table 1 under Sample 2. pH Paco PaO2 HCO3 BE Sample 1 (0945) FiO, 21% 7.46 34 51 Sample 2 (1005) FiO40% 7.43 37 81 24 23 SaO2 95% BP 87% 130/90 120 99.6 HR Temperature (F) 120/70 110 99.4 25 575 14.4 RR 30 500 V1 (ml) MVe (L/min) 15.0 Assessment 1. Classify the blood gas in Sample 1 2. How does the actual Paco, in Sample 1 compare with what might be expected from the patient's minute ventilation? 3. What are the possible causes of the arterial hypoxemia of Sample 1? 4. Classify the blood gas in Sample 2 Intervention 1. What is the probable diagnosis? 2. How could it be confirmed 3. Make specific recommendations for treatment

Answer 1

Asssesment

1)classifying or evaluating blood gas in sample 1 :

given pH - 7.46

PCo2 - 34

HCO3 - 24

Here,pH is very slightly increased (normal pH is 7.35-7.45) and PaCo2 is very slightly decreased (normal PaCo2 is 35-45) and HCO3 is within normal range (normal HCO3 is 22-26) . As pH is slightly high it is called alkalosis and PaCo2 is slightly low it is called as mild respiratory alkalosis, PaO2 is 51 (normal is 80-100) so there is arterial hypoxemia .

2)Normal minute ventilation is usually between 5-8 L/min at rest. Increase in minute volume occurs when arterial oxygen is low and arterial  PaCo2 is more. In sample 1 minute ventilation is 15L/min so we expect  PaCo2 to be more.

But as mentioned she had acute episode of SOB and chest pain that made her breath rapidly causing respiratory alkalosis. In respiratory alkalosis, PaCo2 would be less.

3) Possible causes of arterial hypoxemia in sample 1

• acute pulmonary embolism
• anxiety
• due to ventilator settings like MVe and tidal volume

4)classifying or evaluating blood gas in sample 2 :

given pH - 7.43

PCo2 - 37

HCO3 - 23

PaO2 - 81

As all the above values are within in normal range ,ABG is normal in sample 2.

Intervention

1)Here the etiology behind respiratory alkalosis has to be ruled out and it is possible due to acute pulmonary embolism as pulmonary embolism is the common complication with thrombophlebitis.

2)To rule out pulmonary embolism, a test called D- Dimer has to be done.

3)anticoagulation therapy is recommended for this patient like low molecular weight heparin or direct thrombin inhibitors like dabigatran or factor Xa inhibitors like rivaroxaban.