Oxygenation strategy and neurologic damage after deep hypothermic circulatory arrest. I. Gaseous microemboli.
OBJECTIVE
Recent studies suggest that myocardial reperfusion injury is exacerbated by free radicals when pure oxygen is used during cardiopulmonary bypass. Partial replacement of the oxygenator gas mixture with nitrogen, however, such as has already been adopted clinically in many centers, could increase the risk of gaseous nitrogen microembolus formation and therefore of brain damage because of the low solubility of nitrogen, particularly under conditions of hypothermia.


METHODS
Ten 7- to 10-kg piglets were cooled for 30 minutes to 15 degrees C on cardiopulmonary bypass and then rewarmed for 40 minutes to 37 degrees C. In 5 piglets cardiopulmonary bypass was normoxic and in 5 it was hyperoxic. In each group 3 bubble oxygenators without arterial filters and 2 membrane oxygenators with filters were used. Cerebral microemboli were monitored continuously by carotid Doppler ultrasonography (8 MHz) and intermittently by fluorescence retinography.


RESULTS
Embolus count was greater with lower rectal temperature (P <.001), use of a bubble oxygenator (P <.001), and lower oxygen concentration (P =.021) but was not affected by the temperature gradient between blood and body during cooling or rewarming.


CONCLUSIONS
Gaseous microemboli are increased with normoxic perfusion, but this is only important if a bubble oxygenator without a filter is used.
Nollert
G
G
Department of Cardiac Surgery, Children's Hospital, Department of Surgery, Harvard Medical School, Boston, MA, USA.
Nagashima
M
M
Bucerius
J
J
Shin'oka
T
T
Jonas
R A
RA
D000818:Animals; D001831:Body Temperature; D002315:Cardiopulmonary Bypass / Q000009:adverse effects* / Q000379:methods; D004618:Embolism, Air / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000209:etiology*; D005451:Fluorescein Angiography; D006324:Heart Arrest, Induced; D007036:Hypothermia, Induced; D002542:Intracranial Embolism and Thrombosis / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000209:etiology*; D010100:Oxygen / Q000008:administration & dosage*; D010106:Oxygenators; D013552:Swine; D018608:Ultrasonography, Doppler
D010100:Oxygen