Intracranial pressure - waveforms and monitoring

ICP waveforms

1. ICP waveforms & monitoring
Dr. Joe M Das

2. •Physiology
•Waveforms
•Monitoring

3. Physiology

5. V
intracranialvault=V
brain+V
blood+V
csf

8. •“compliance reflects the
ability of the intracranial
system to compensate for
increases in volume
without subsequent
increases in ICP. When
compliance is decreased,
even small increases in
intracranial volume
result in large increases
in ICP.”

9. Normal ICP
•It is difficult to establish a universal “normal
value” for ICP as it depends on age, body posture
and clinical conditions.
•The upper limit of normal ICP –15 mm Hg
(5 –10 mm Hg)
•Physiologic increase –Coughing, sneezing –30-50
mm Hg
•ICP = CSF pressure –The pressure that must be
exerted against a needle introduced into the CSF
space to just prevent escape of fluid

10. ICP waveforms

11. ICP monitoring waveforms
Flow of 3 upstrokes in one wave.
P1 = (Percussion wave) represents arterial pulsation
P2 = (Tidal wave) represents intracranial compliance
P3 = (Dicroticwave) represents venous pulsation
In normal ICP waveform P1 should have highest
upstroke, P2 in between and P3 should show lowest
upstroke.
On eyeballing the monitor, if P2 is higher than P1 -it
indicates intracranial hypertension.

13. Related to
•Cardiac cycle : within individual waves
•Respiratory cycle : between consecutive waves

15. •ICP waveform –pulsatile
•Baseline is referred to as ICP
•Magnitude of baseline, amplitude &
periodicity of pulsatilecomponents
•Earliest sign of ↑ ICP –Changes in pulsatile
components

16. Flat
•EVD clogged / kinked
•Patient expired

17. ↑⁄↓ amplitude
•Increasing CSF volume
(or decreased)
•If a large volume of CSF
is drained off, the
waveform will decrease
in amplitude.
•Missing bone flap

18. Prominent P1 wave
•The systolic BP is too
high

19. Diminished P1 wave
•If the systolic BP is too
low, P1 decreases and
eventually disappears,
leaving only P2.
•P2 and P3 are not
changed by this.

20. Prominent P2 wave
•The mass lesion is
increasing in volume
•The intracranial
compliance has
decreased
•An inspiratorybreath
hold (as ICP will also
rise)

21. Diminished P2 and P3 waves
•Hyperventilation

22. Rounded ICP waveform
•ICP critically high

23. Lundberg waves
Nils Lundberg

25. Lundberg A wave

26. Lundberg A waves
•Increases of ICP sustained for several minutes and
then return spontaneously to baseline, which is
slightly higher than the preceding one.
•Results from ↑ cerebrovascularvolume due to
vasodilatation (Lundberg)
•Results from normal compensatory response to
decreases in CPP. Hence give vasopressors.
(Rosner) –But may enhance lesion size & edema

27. 4 phases:
1.Drift phase : ↓ CPP → vasodilatation
2.Plateau phase : Vasodilatation → ↑ ICP
3.Ischemic response phase : ↓ CPP → Cerebral
ischemia → Brainstem vasomotor centres→
Cushing response
4.Resolution phase : Cushing response →
Restores CPP

29. Lundberg B wave

30. Lundberg B waves
•Short elevations of modest nature (10 –20 mm
Hg)
•0.5 –2 Hz
•Relate to vasodilatation secondary to respiratory
fluctuations in PaCO
2
•Seen in ventilated patients (?)
•Secondary to intracranial vasomotor waves,
causing variations in CBF
•Reflects ↑ ICP in a qualitative manner

31. Lundberg C waves

32. Lundberg C wave

33. Lundberg C waves
•More rapid sinusoidal fluctuation (0.1 Hz)
•Corresponds to Traube-Hering-Meyer
fluctuations in arterial pressure brought about
by oscillations in baroreceptor and
chemoreceptor reflex control systems
•Sometimes seen in normal ICP waveform
•High amplitude –pre-terminal, seen on top of
A waves

34. ICP monitoring

35. Why look at ICP waveform analysis?
“…provides information about intracranial
dynamics that can help identify individuals who
have decreased adaptive capacity and are at risk
for increases in ICP and decreases in CPP, which
may contribute to secondary brain injury and
have a negative impact on neurologic outcome.”
C.J Kirknesset. al; J NeurosciNurs. 2000 Oct; 32(5):271-7.

36. •The main indications for ICP monitoring are:
–Glasgow Coma Scale (GCS ) < 8
–Posturing (extension, flexion)
–Bilateral or unilateral pupil dilation (except with
Epidural Hematomas)
–CT Scan results showing edema and/or mid-line
shift
–Physical assessment /neurological assessment
findings which indicate a need for monitoring

37. •Contraindications:
–Awake patient
–Coagulopathy

38. Methods of ICP
measurement
•Technology
–external strain gauge
–catheter tip (internal)
–strain gauge
–fibre-optic
•Location
–Ventricular (EVD/IVC)
–Intraparenchymal
–Subarachnoid
–Subdural/Extradural
–External Fontanelle

39. External Ventricular Drain
•EVD connected to external strain gauge is the
gold standard for measuring ICP
•Tip in foramen of Monro
•Extensive history, low cost, reliability,
therapeutic
•Success rate of cannulation–82%

41. •Malposition: 4 –20%
–Did not have significant clinical sequelae
•Occlusion : By brain matter / blood clots
–Flush EVD
•Hemorrhage : 0 –15% (1.1%)
–Most asymptomatic
–Intervention in 0.5%

42. •Infection : 0 –22% (8.8%)
–Risk factors : IVH, SAH, craniotomy, CSF leakage,
systemic infection, depressed skull #
–Duration of catheterization & irrigation of catheter
–Venue of insertion –No difference
–Extended tunneling
•Sandalcioglu-<5 vs>5 cm –83% vs17%
•Leung –No difference
–Prophylactic catheter exchange : No difference

43. –Prophylactic antibiotics:
•Periproceduralvsnone –No difference
•Periproceduralvsentire duration –No difference
•Guidelines for the Management of Severe Traumatic
Brain Injury –No antibiotic prophylaxis
–Antibiotic impregnated catheter:
•Rifampin+ Minocycline(Zabramski) –9.4 to 1.3%
•Cost

44. When to pull the EVD out?
•CT evidence of resolution of cerebral oedema,
and
•Improvement of ICP (consistently under 20-
25)
•Or if the EVD is infected.

45. FibreopticICP monitor
•Catheter tip measures the amount of light
reflected off a pressure sensitive diaphragm
•IntraparenchymalCamino ICP monitor
–Ease of insertion –Right frontal
–Also in the region with pathology
–Can be inserted in severely compressed ventricles or
those with midline shift
–Low risk of hemorrhage and infection
–Zero drift: Recalibration cannot be performed
•2 mm Hg (first 24 hrs); 1 mm Hg (first 5 days) –Manufacturer
•0.5 –3.2 mm Hg drift -Actual

47. Miniature Strain Gauge
•Codman MicroSensorICP Transducer
–Microchip pressure sensor at the tip of a flexible
nylon cable that produces different electricity
based on pressure
•Intraventricular(Correlation coefficient 0.97 with EVD,
Drift 0.2 mm Hg)
•Intraparenchymal(Less accurate)
•Subdural space (Not enough studies)

48. •SpiegelbergParenchymalTransducer
–Air pouch at the tip that is maintained at constant
volume
–Pressure transducer located in ICP monitor
–Recalibration can be made easily
–Good correlation with ICP measured by
ventriculostomy

50. •Compliance Monitor
–Experimental stage
–Change in volume per unit change in pressure
–Spielberg compliance monitor injects small
amount of air into the air balloon pouch and
measures the pressure response to this change in
volume
–Inverse relationship between compliance and ICP

51. •Noninvasive ICP monitoring
–CT, clinical examination, monitoring pressure in
epidural space
–Optic Nerve Sheath Diameter (ONSD)
•Measured by ultrasound
•Critical value is different in different studies
–Venous Opening Pressure (VOP)
•Measured by venous ophthalmodynamometry
•Requires dilatation of pupil
•Performed intermittently –Only screening purpose
–Cochlear fluid pressure, Flow velocity in intracranial
arteries, Delay in VEPs

52. •Pediatric ICP monitoring
–ICP monitoring only as an option for treating
patients with severe traumatic brain injury
(GCS < 8)
–Similar complication rates as in adults

53. Summary
•V
intracranialvault =
V
brain+V
blood+V
csf
•P1 = (Percussion wave)
represents arterial
pulsation
P2 = (Tidal wave)
represents intracranial
compliance
P3 = (Dicroticwave)
represents venous
pulsation

54. •Lundberg waves
–A
•Plateau
•Results from ↑ cerebrovascularvolume due to
vasodilatation
–B
•Secondary to intracranial vasomotor waves, causing
variations in CBF
•Reflects ↑ ICP in a qualitative manner
–C
•Corresponds to Traube-Hering-Meyer fluctuations
•Sometimes seen in normal ICP waveform

55. Summary
•ICP monitoring & ICP-directed treatment remains the
cornerstone of neurocriticalcare
•EVD connected to external strain gauge remains the
most reliable, cost-effective and accurate method for
monitoring ICP
–Allows CSF drainage
–Infection and hemorrhage are the main problems
•Intraparenchymalmonitors are gaining popularity
–Easy to insert, low complication rates
–Zero drift, mechanical failure are the problems
•New technologies including the non-invasive ones are
emerging

56. References
•Handbook of Neurosurgery, Mark S Greenberg
•YoumansNeurological Surgery, 6
th
edition
•