How I do infusion test. Dr Zofia H. Czosnyka University of Cambridge, UK Infusion test: procedure to identify model of CSF compensatory reserve introduced in 1973 by Anthony Marmarou. Essential parameters: Resistance to CSF outflow and compliance of CSF space ICP Infusion 1 ml/min TIME ~30 minutes

What we need? Hardware Pressure transducer, tubing, needles Essential: sterile preparation of transducer and tubings

If pulse waveform of ICP is small or noisy, ABP (Finapress) pulse is helpful. See spectra, check peaks associated to heart rate in ABP and ICP

ICP HR AMP RAP Real time observation of trends of mean ICP, heart rate, pulse amplitude of ICP and RAP index during the study. Always mark start, end of infusion!

ICP AMP RESP RR Slow SD AMP/RESP ‘Waveforms trends’ – pulse amplitude, respiratory amplitude, respiratory rate (RR), power of SLOW ICP waves

ICP AMP AMP ICP Pulse amplitude/pressure line. Slope is usually positive. Higher slope (according to Professor Anile, J Neurosurg. 2010 Jul;113(1):64-73) => indicates better chance to respond to shunting: Slope above 0.15.

Lower breakpoint of AMP-P line- is it ‘optimal pressure? ICP AMP AMP ICP

ICP AMP After study is finished: Analysis of the model of Professor Marmarou: First: mark baseline, transition and end-plateau periods. Introduce infusion rate and press ‘calculate’

Click ‘more’ and you see: Interpolation of ICP trend with modelling curve Exponential pressure-volume curve Amplitude –pressure line Trend of amplitude in time I use this screen to assess visually quality of identification of the model

If everything looks OK, you can display report and copy/ paste it to WORD

Test ‘unfinished’- if pressure increases to 40 mm Hg without reaching plateau ICP HR AMP RAP

‘Dynamic’ analysis may predict plateau R= 77 mmHg/(ml/min) ‘Dynamic’ analysis may predict plateau

ICP AMP One needle test: we usually observe rapid increase of ICP just after start of infusion, not reflected by increase in AMP. Tick in ‘Parameters’ -> ‘one needle’ option and problem of higher resistance of the needle may be solved automatically...

Step-rise of ICP is accounted for and eliminated from its potential influence on CSF compensatory parameters

Now in situ: VP stratas @ 0.5 in line with Ommaya. ICP HR AMP RAP Hydrocephalus post SAH in 2006. Shunted - revisions. Last revision (09/10/12). Now in situ: VP stratas @ 0.5 in line with Ommaya. Headaches, tenderness over the tubing and the valve.

ICM+ has a database of shunt parameters from Cambridge Shunt Lab ICM+ has a database of shunt parameters from Cambridge Shunt Lab. Every shunt at given performance level has a limit above which pressure should not rise during infusion of given rate ( 1ml/min or 1.5 ml/min). If pressure exceeds this limit (blue horizontal line), it indicates that shunt underdrains. Shunt underdrains

If blue line is not crossed, shunt probably works properly

Final report sent to consultant neurosurgeon John John HospitalNo XXXXXXXX 28/10/2013 DateOfBirth XXXXXXXX Sex Male DateOfIctus 28/10/2013 DateOfAdmission SAH, delayed hydrocephalus, low OP in LP. Increase in ventricle size in CT. Low GCS (9). LP study on A5 ICP baseline [mmHg] 4.39 ICP plateau [mmHg] 25.52 AMP baseline [mmHg] 0.94 AMP plateau [mmHg] 2.79 Rcsf [mmHg*min/ml] 16.27 Elastance [1/ml] 0.14 PVI [ml] 17.07 Pss [mmHg] 0.00 CSF production rate [ml/min] 0.27 Volume infused [ml] 29.48 Infusion duration [min] 19.66 Normalised Error [%] 1.351 Final report sent to consultant neurosurgeon Normal baseline pressure with increased resistance to CSF outflow. Strong regular vasogenic waves recorded during the study. Overall: Disturbed CSF dynamics. Dr. Czosnyka CSF sample sent to bacteriology Y  CSF withdrawn at end of study as therapeutic test: N Should you require any assistance with these results, Professor Pickard, Dr’s Zofia or Marek Czosnyka will be happy to assist.  Contact details are: Dr Zofia Czosnyka – 72831764; Dr Marek Czosnyka – 3932; Professor Pickard – 6858 (Maria, secretary)

Happy infusion studies!