K. Canavesi

Arterio-jugular Difference of Oxygen Content and Outcome After Head Injury

This study investigated AJDo2 (arterio-jugular difference of oxygen content) in a large sample of severely head-injured patients to identify its pattern during the first days after injury and to describe the relationship of AJDo2 with acute neurological severity and with outcome 6 mo after trauma. In 229 comatose head-injured patients, we monitored intracranial pressure, cerebral perfusion pressure, and AJDo2. Outcome was defined 6 mo after injury. Jugular hemoglobin oxygen saturation (Sjo2) averaged 68%. The mean AJDo2 was 4.24 vol% (sd, 1.3 vol%). There were 80 measurements (4.6%) with Sjo2 <5% and 304 (17.6%) with saturation >75%. AJDo2 was higher than 8.7 vol% in 8 measurements (0.4%) and was lower than 3.9 vol% in 718 (42%) measurements. AJDo2 was higher during the first tests and decreased steadily over the next few days. Cases with a favorable outcome had a higher mean AJDo2 (4.3 vol%; sd, 0.3 vol%) than patients with severe disability or vegetative status (3.8 vol%; sd, 1.3 vol%) and patients who died (3.6 vol%; sd, 1 vol%). This difference was significant (P < 0.001). We conclude that low levels of AJDo2 are correlated with a poor prognosis, whereas normal or high levels of AJDo2 are predictive of better results.

Head injury, subarachnoid hemorrhage and intracranial pressure monitoring in Italy

Background.Intracranial pressure monitoring is recommended for the management of severe head injury and is increasingly used during intensive care for other pathologies, such as subarachnoid hemorrhage. However, it is still not uniformly applied in different centers. The objectives of this paper are to summarize the frequency and the modalities of intracranial pressure (ICP) monitoring in different centers in Italy; to describe its use in traumatic brain injury (TBI) and in subarachnoid hemorrhage (SAH); and to identify areas for improvement.Method. The medical directors of either the neurosurgical department or the intensive care unit, or both, of every Italian neurosurgical center were personally interviewed. They answered specific questions about TBI and SAH patients admitted, and ICP monitoring used, in their units. Data were cleared of any obvious inconsistencies and entered in a database for analysis. All analyses were based simply on the data declared.Findings. The clinical information was obtained from 9137 TBI cases, of whom 4240 severe, and 3151 SAH patients. Among the 106 participating centers, 15 did not use ICP monitoring at all. The remaining 91 had used 3293 ICP devices during the year 2001; 146 were used in tumor cases, 2009 in TBI, and 1138 in SAH. Twenty-two percent of TBI cases admitted to centers with ICP equipment were monitored. Restricting this analysis to severe cases, 47% of TBI with a GCS <8 had ICP. On average, 36% of SAH underwent ICP monitoring. The proportions of head injury and SAH cases who underwent ICP monitoring varied widely in the different centers. Dividing the country into three main areas (north, center and south), there were considerable differences both in the rate of admissions per million inhabitants and in the frequency of ICP monitoring.Interpretation. ICP monitoring in Italy is used in most, but not all, centers. ICP is measured fairly extensively in head injury cases, but a significant proportion of SAH patients is monitored as well. There are substantial differences in the frequency of ICP monitoring in different parts of the country. The use of ICP for both these indications, and the rates of admission to specialized centers, could be improved.

Oxygen and Carbon Dioxide in the Cerebral Circulation during Progression to Brain Death

Background:The authors propose that for a moderate reduction of perfusion during progressive irreversible ischemia, oxygen extraction increases to maintain aerobic metabolism, and arteriojugular oxygen difference (AJDo2) increases. Because of reduced carbon dioxide washout, venoarterial difference in carbon dioxide tension (DPco2) increases, with no change in the DPco2/AJDo2 ratio. With further reduction of cerebral perfusion, the aerobic metabolism will begin to decrease, AJDo2 will decrease while DPco2 will continue to increase, and the ratio will increase. When brain infarction develops, the metabolism will be abated, no oxygen will be consumed, and no carbon dioxide will be produced. Methods:The authors studied 12 patients with acute cerebral damage that evolved to brain death and collected intermittent arterial and jugular blood samples. Results:Four patterns were observed: (1) AJDo2 of 4.1 ± 0.7 vol%, DPco2 of 6.5 ± 1.9 mmHg, and a ratio of 1.55 ± 0.3 with cerebral perfusion pressure of 62.5 ± 13.4 mmHg; (2) a coupled increase of AJDo2 (5.8 ± 0.7 vol%) and DPco2 (10.1 ± 1.0 mmHg) with no change in ratio (1.92 ± 0.14) and cerebral perfusion pressure (57.9 ± 5.8 mmHg); (3) AJDo2 of 4.7 ± 0.4 vol% with an increase in DPco2 (11.8 ± 1 mmHg) and correspondingly higher ratio (2.7 ± 0.2); in this phase, cerebral perfusion pressure was 39.7 ± 10.5 mmHg; (4) immediately before diagnosis of brain death (cerebral perfusion pressure, 17 ± 10.4 mmHg), there was a decrease of AJDo2 (1.1 ± 0.1 vol%) and of DPco2 (5.3 ± 0.6 mmHg) with a further ratio increase (5.1 ± 0.8). Conclusions:Until compensatory mechanisms are effective, AJDo2 and DPco2 remain coupled. However, when the brains ability to compensate for reduced oxygen delivery is exceeded, the ratio of DPco2 to AJDo2 starts to increase.