The following blood gases obtained  at 8am and 10 am from a patient  admitted to the ICU with Grade V Subarachnoid hemorrhage. Between the two sets of arterial blood gases a procedure was performed. Changes in gas tensions were not accompanied by changes in haemodynamic parameters.

Time

8 AM

10 AM

FiO2

0.3

1.0

pH

7.41

7.06

PCO2

39 mm Hg (5.2 kPa)

108 mm Hg (14.4 kPa)

PO2

103 mm Hg (13.7 (kPa)

425 mm Hg (56.6 kPa)

Peak airway
pressure

24 cm water

0 cm water

Tidal
volume

650 ml

0 ml

15.1     What procedure was performed? Give reasons.

[Click here to toggle visibility of the answers]

College Answer

Apnoea test (as peak pressure has dropped to zero and there is no recordable TV. Not likely to be bronchoscopy as peak pressures are high during bronchoscopy

Discussion

This patient is not breathing, and is demonstrating no respiratory drive in spite of a ridiculously high CO2. The 100% FiO2 suggests that an apnoea test for brain death is in progress.

 

References

References

Ropper, Allan H., Sean K. Kennedy, and Lisa Russell. "Apnea testing in the diagnosis of brain death: clinical and physiological observations." Journal of neurosurgery 55.6 (1981): 942-946.