Pressure reactivity: Relationship between ICP and arterial blood pressure (ABP). Pressure-reactivity index, computational methods. Clinical examples.

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Mildred Phelps
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1 Pressure reactivity: Relationship between ICP and arterial blood pressure (ABP). Pressure-reactivity index, computational methods. Clinical examples. Optimization of cerebral perfusion pressure: Relationship between Pressure Reactivity and CPP. Does optimal CPP exist always? Implications on management.

Optimization of cerebral perfusion pressure: Relationship between Pressure

2 Simultaneous analysis of slow changes in arterial pressure and ICP System with disturbed pressurereactivity Pressurereactivity works properly

4 Thanks to Dr.P.Smielewski PRx- Calculation principles Input signals ICP, ABP Ouput trend PRx ABP 10 sec window 5 min window MAP Mean(ABP) Mean(ICP) MICP ICP Correlation(MAP, MICP) Primary analysis Final Analysis

5 PRx is a rather noisy parameter Some smoothing is required PRx Smoothed PRx Thanks to Dr.P.Smielewski

6 Coherence Unknown origin of micp fluctuations Low coherence between ABP and ICP suggests limited contribution from ABP, however it could also be an evidence of strong nonlinearities MAP MICP Frequency [Hz] 1 Hz Thanks to Dr.P.Smielewski

contribution from ABP, however it could also be an

7 Detrended Thanks to Dr.P.Smielewski Confounding factors: trends MAP MICP MAP_dt MICP_dt MICP PRx = < 0! MAP MICP_dt PRx = 0.54 > 0! MAP_dt

8 Detrending example: raw signals ABP ICP 20 min period Thanks to Dr.P.Smielewski

9 Detrending example: after low pass filter MAP MICP 20 min period Thanks to Dr.P.Smielewski

10 Detrending example: high pass filter method MAP_dt MICP_dt 20 min period Thanks to Dr.P.Smielewski

11 Intracranial Hypertension

12 Plateau Wave

13 Arterial Hypertension

14 CT Scan 1 Scan 2 SROR (CPP = 74 mmhg) (CPP = 98 mmhg) 5 60% % % 0.4 Figure 5: PET vs. PRx PRx r 2 = 0.32 p = 0.02 (n = 17) PRx correlates with PET-static rate of autoregulation Global SROR PET Steiner LA, Coles JP, Johnston AJ, Chatfield DA, Smielewski P, Fryer TD, Aigbirhio FI, Clark JC, Pickard JD, Menon DK, Czosnyka M. Assessment of Cerebrovascular Autoregulation in Head-Injured Patients. A Validation Study.Stroke :

6 0 20 40 60 80 100 120 140 Global SROR PET Steiner LA, Coles JP, Johnston AJ, Chatfield DA, Smielewski P, Fryer TD,

rcbf CMRO 2 OEF 0-30 ml/100g/min 0-100 m/100g/min 0-75 % 0.8 0.8 0.6 r 2 = 0.34 p = 0.0022 0.6 r 2 = 0.61 p < 0.00005 0.4 0.4 PRx 0.2 PRx 0.2 0.0 0.

15 rcbf CMRO 2 OEF 0-30 ml/100g/min m/100g/min 0-75 % r 2 = 0.34 p = r 2 = 0.61 p < PRx 0.2 PRx global CMRO 2 (ml 100g -1 min -1 ) Global oxygen extraction fraction (%)

2-0.2-0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.

16 FLUX ICP ABP PRx and the LLA ABP lowered to zero in piglet LDF vs. CPP to find lower limit of autoregulation PRx compared against LLA Brady K, et al: Stroke 2008 Lee J, et al: Stroke 2009

17 Individual trends are most important

18 Monitoring of Pressure Reactivity Index ICM+ software:

19 Ups and downs... Final was not very optimistic

20 Deterioration of PRx precedes refractory intracranial hypertension?

$refractory$

21 Refractory intracranial hypertension (2) ABP mmhg ICP mmhg PRx CPP mmhg

22 Advancing intracranial hypertension- fatal outcome

23 Optimal CPP- oriented therapy PRx PRx Mx Both PRx and Mx show the U-shape relationship with mean CPP (200 patients!). This indicate that for low CPP and CPP above 90 mm Hg both autoregulation and pressure reactivity are defective. There is an optimal CPP from 70 to 90 mm Hg which helps to restore vascular functions after head injury a.) a.) Optimal CPP Cerebral Perfus ion Press ure (mm Hg) Cerebral Perfus ion Press ure (mm Hg) Steiner LA at al. Continuous monitoring of cerebrovascular pressure reactivity allows determination of optimal cerebral perfusion pressure in patients with traumatic brain injury. Crit Care Med Apr;30(4):733-8.

24 New results Thanks to Dr. M.Aries

25 If we can see it in statistical evaluation of big series of patients, can we see it in individual cases? 4 6 hours moving window The chart shows that lowest PRx values corresponding to the strongest autoregulation level fall in the CPP range of mmhg Thanks to Dr. P.Smielewski

26 Optimal CPP in individual cases Thanks to Dr.L.Steiner

27 Optimal CPP oriented therapy? CPPopt ADMISSION TO CRITICAL CARE UNIT START TREATMENT AT CPP 70 MM HG (OR HIGHER IN SEVERLY HEAD INJURED PATIENTS) MONITOR AND AVERAGE PRx FOR 2 HOURS Patient 1 IDENTIFY RANGE OF MINIMAL PRx BY VARYING CPP IN STEPS OF 10 mm Hg OVER 2 HOUR PERIODS CPP OPT IDENTIFIED CALCULATE CPP OPT NO CPP OPT Hours MINIMIZE CPP CPP OPT DURING THE FOLLOWING 2 HOURS MONITOR AND MINIMIZE PRx, POOL DATA AFTER 2 HOURS Steiner LA, Czosnyka M, Piechnik SK, Smielewski P, Chatfield D, Menon DK, Pickard JD. Continuous monitoring of cerebrovascular pressure reactivity allows determination of optimal cerebral perfusion pressure in patients with traumatic brain injury. Crit Care Med Apr;30(4):733-8.

28 CPP OPT and Outcome r = (Spearman rank test) p = Thanks to Dr. L.Steiner

29 What do we know so far about PRx in SAH? (statin trial, placebo branch). PRx agrees with Transient Hyperaemic Response Test and gets worse in vasospasm Tseng MY, Czosnyka M, Richards H, Pickard JD, Kirkpatrick PJ. Effects of acute treatment with pravastatin on cerebral vasospasm, autoregulation, and delayed ischemic deficits after aneurysmal subarachnoid hemorrhage: a phase II randomized placebo-controlled trial. Stroke Aug;36(8):

30 Prx SAH: Effect of Vasospasm CPP [mmhg] Thanks to Dr. P.Biljenga

31 PRx PRx SAH: Effect of Hypertonic Saline 1.0 PRx improvement N= Before HS perfusion During HS perfusion After HS perfusion CPP[mmHg] CPP opt increase N=7 CPP opt [mmhg] Thanks to Dr. P.Biljenga

33 Temporal profiles of cerebrovascular pressure reactivity in children with traumatic brain injury Prospective observational study, commenced 2006 Undertaken at the state of Victoria s tertiary paediatric hospital, the Royal Children s Hospital (RCH) Aims: Establish monitoring of PRx in children with TBI at the RCH Investigate PRx vs time PRx vs CPP PRx vs outcome Thanks to Mr. P.Lewis

34 Patients / Data n=23 patients Age range 4-16 years All severe TBI (GCS 3-8) on admission All received ICP monitoring via parenchymal or fluidcoupled monitoring (EVD) Continuous recording of ABP, ICP, EtCO2 from admission until removal of ICP monitor Range: 1-11 days Median recording length: 3 days Not all monitored days able to be analysed Continuous drainage from EVD ICM+ Codman Thanks to Mr. P.Lewis

35 PRx vs CPP (pooled) Thanks to Mr. P.Lewis

36 Summary Simple analysis of ABP-ICP interaction (low bandwidth) Positive association with outcome Detection of optimal CPP Good agreement with other more expensive methods Promising value of PRx after SAH

perfusion pressure: Definitions. Implication on management protocols. What happens when CPP is too low, and when it is too high? Non-invasive CPP?

7. Cerebral perfusion pressure: Definitions. Implication on management protocols. What happens when CPP is too low, and when it is too high? Non-invasive CPP? Definitions of CPP Thanks to Dr. E. Schmidt