TRANSCRANIAL DOPPLER SONOGRAPHY - AN IMPO RTANT DIAGNOSTIC-TOOL IN THE MANAGEMENT OF SEVERE CRANIOCEREBRAL TRAUMA

Transcranial Doppler sonography (TCD) is a simple, noninvasive bedside procedure that can be repeated any time for the measurement of cerebr al blood flow velocity in the great basal cerebral arteries. It is pra cticable in most severely head-injured patients in critical care. Flow patterns and pulsatility index (PI) resulting from maximal systolic a nd diastolic flow velocities and representing cerebrovascular resistan ce give quite an accurate impression of potential intracranial hyperte nsion and the dependent cerebral perfusion pressure (CPP). With increa sing intracranial pressure (ICP) and decreasing CCP, diastolic flow is progressively reduced. If ICP reaches the systemic diastolic blood pr essure level, diastolic flow disappears. Oscillating (reverberating) f low patterns are seen when ICP increases further up to the arterial me an pressure level. The authors' own studies on 20 comatose patients wi th raised ICP showed typical changes in TCD parameters following diffe rent therapies for intracranial hypertension. Under continuous TCD mon itoring of the middle cerebral artery, increases in maximal flow veloc ity (from 4% up to 102%, on average 27%) and mean flow velocity (from 18% up to 153%, on average 73%) were always observed after osmotherapy . In addition, a variable increase in negative frequencies was noted, probably due to increased turbulences. After barbiturate administratio n (thiopentone bolus of 0.3 g) a flow reduction was always seen [from - 2% up to - 25% (on average - 13%) for maximal flow velocity and from - 9% up to - 30% (on average - 19%) for mean flow velocity]. The effi ciency of all therapeutic measures for decreasing intracranial hyperte nsion, controlled by continuous ICP monitoring, was found to be closel y related to the degree of drop in Pl. In constant respiratory conditi ons with mild hyperventilation a clear, but only intraindividual, line ar relation between (raised) ICP over 20 mmHg and PI could be observed , in some cases over a period of several days. On the other hand, ther e was a large degree of interindividual variability in ICP and PI. Thu s, in patients with an ICP level of 30 mmHg, a wide range of PI, from 1.0 up to 3.5, was found. In conclusion, TCD proved to be a useful met hod for assessing the effectiveness of osmotherapy and barbiturate adm inistration in cases of intracranial hypertension, especially if ICP m onitoring is not available. TCD is also useful for the diagnosis of po sttraumatic vasospasm. Disturbed cerebrovascular autoregulation can be assessed by determination of CO, reactivity. Oscillating (reverberati ng) flow patterns and systolic spikes indicate intracranial circulator y arrest and can be used as an additional method of determining brain death.