J Nates, I Christou, A Alexandrov
ards, cardiac, cardio-pulmonary support, critical care, education, emergency medicine, hemodynamics, intensive care medicine, intensivecare unit, medicine, multiorgan failure, neuro, patient care, pediatric, respiratory failure, surgical i, ventilation
J Nates, I Christou, A Alexandrov. Case of the Month: Case 1. The Internet Journal of Emergency and Intensive Care Medicine. 1999 Volume 4 Number 1.
A white female, 71 y.o., was admitted to the neurological ICU due to subarachnoid hemorrhage secondary to a ruptured cerebral aneurysm. Patient developed hydrocephalus which was managed with a ventriculostomy after the clipping and her intracranial pressure (ICP) was continuously monitored.
The patient developed severe cerebral vasospasm with deterioration of her mental status requiring endotracheal intubation. This complication was followed by sepsis with ARD’S. After spasm resolution, patient developed systemic infection. The following hemodynamic and Transcranial Doppler (TCD) parameters were recorded (patient was sedated, paralyzed and on controlled mechanical ventilation):
TCD waveforms correspond to the segment between dotted arrows on the monitor screen above. The white arrows indicate waveforms with pulsatility index 1.4 (left) and 1.0 (right).
1. The diagnosis is intracranial hypertension. Note that the ICP raises from approximately 10 mmHg up to 25 mmHg. These ICP changes occurred along with hypovolemia, CVP 5 mmHg and wedge pressure 4 to 6 mmHg.
2. The variations are due to intravascular volume depletion. In this case, the “systolic pressure variation”, or SPV (SPV is the difference between the maximal and minimal systolic blood pressure during one ventilation cycle), is greater than 15 mmHg. On the monitor screen, the dDown is easily seen during the inspiratory phase on the ventilation cycle.
3. The ICP variations correspond to the blood pressure and cardiac output changes following the intra-thoracic pressure pattern during mechanical ventilation. Elevated ICP and cyclic ICP changes were present in a patient who had brain infarctions, hydrocephalus and hypovolemia showing systemic pressure dependency of the ICP.
4. Pulsatility index (Gosling PI = Peak systolic – end diastolic / mean flow velocities) shows resistance to blood flow in the intracranial cavity in relationship to systemic blood pressure. When ICP increases (or CPP decreases), PI increases to 1.4 and then decreases to 1.0 with ICP drops to less than 14 mm Hg. TCD showed time corresponding changes from high resistance to low resistance flow waveforms during meachanical ventilation. Note that mean flow velocity measurements can be affected by these factors (see the following figure).