Case of the Month
Case 1
Joseph L. Nates, MD*
Assistant Professor
Ioannis Christou, MD†
Visiting Clinician Scientist
Andrei Alexandrov, MD, RVT†
Assistant professor

Departments of Neurosurgery and Anesthesia-Critical Care Medicine*, and Neurology-Stroke Service†
The University of Texas-Houston
Health Science Center Medical School

Nates JL, Christou I, Alexandrov A: Case of the Month, Case 1. The Internet Journal of Emergency and Intensive Care Medicine 2000; Volume 4 Number 1: http://www.ispub.com/journals/IJEICM/Vol4N1/case1.htm . Published January 1, 2000; Last Updated January 1, 2000. (Please add "Date Accessed").

History

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.

Monitor Screen with Hemodynamic Changes

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).

Questions

1. What is your diagnosis?
2. Why is there a variation in all pressure waveforms of more than 15 mmHg?
3. What is your explanation for the cyclic variations in ICP?
4. What is your explanation for corresponding changes in TCD recordings?

click here for the answers

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 below).

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References

1. Pizov, Reuven MD. Cohen, Morris MD. Weiss, Yoram MD. Segal, Eran MD. Cotev, Shamay MD. Perel, Azriel MD. Positive end-expiratory pressure-induced hemodynamic changes are reflected in the arterial pressure waveform. Critical Care Medicine 1996; 24(8):1381-1387.
2. Perel A, Pizov R, Cotev S: Systolic blood pressure variation is a sensitive indicator of hypovolemia in ventilated dogs subjected to graded hemorrhage. Anesthesiology 1987; 67:498-502.
3. Newell D. Transcranial Doppler in head trauma and brain death. In: Tegeler CH, Babikian VL, Gomez CR. Neurosonology. St Louis: Mosby 1996.