Potential error in ventriculocisternal perfusion method for determination of cerebrospinal fluid formation rate in cats [Moguća greška kod određivanja stvaranja cerebrospinalne tekućine pomoću metode ventrikulocisternalne perfuzije kod mačke]

Maraković, Jurica and Orešković, Darko and Jurjević, Ivana and Radoš, Milan and Chudy, Darko and Klarica, Marijan (2011) Potential error in ventriculocisternal perfusion method for determination of cerebrospinal fluid formation rate in cats [Moguća greška kod određivanja stvaranja cerebrospinalne tekućine pomoću metode ventrikulocisternalne perfuzije kod mačke]. Collegium Antropologicum, 35 (S. 1). pp. 73-77. ISSN 0350-6134

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Abstract

The cerebrospinal fluid (CSF) formation rate (Vf) has been extensively studied by the ventriculocisternal perfusion, a method still regarded as the most precise one. This method as well as the equation for the calculation of the CSF formation rate (Vf) was established by Heisey et al4 on indicator dilution in perfusate. They assumed that the dilution of the indicator substance in perfusion is a consequence of newly formed CSF i.e. a higher CSF formation rate would result in a higher degree of dilution of the indicator substance. Therefore, such method is indirect and any mistake in the interpretation of the degree of indicator dilution would lead to questionable and often contradictory results regarding CSF formation rates. According to Heisey’s equation, Vf shoud not depend on the rate of ventriculocisternal perfusion. However it has been shown that Vf is perfusion dependt value10, and also that during perfusion the indicator substance is partially absorbed into surrounding tissue. It is possible that obtained Vf dependence on perfusion rate was caused by observed absorption of indicator substances. For that reason, in anaesthetised cats ventriculocisternal perfusion was performed at higher (252.0 mL/min) and at lower perfusion rate (65.5 mL/min) and Vf was calculated at both experimental and corrected (just for absorbed amount) values of indicator substance. Since (inspite of the correction) the difference of 12.4 mL/min between lower (15.0 mL/min) and higher perfusion rate (27.4 mL/min) was obtained, it is obvious that ventriculocisternal perfusion method cannot be considered reliable for measuring CSF formation rate.

Abstract in Croatian

Količina stvorenog cerebrospinalnog likvora (CSF) se najčešće određuje pomoću ventrikulocisternalne perfuzije, metode koja se smatra jednom od najpreciznijih metoda. Tu metodu i jednadnadžbu za izračunavanje količine stvorenog likvora (Vf) su razvili Heisey i sur.4 na temelju razređenja indikatora u perfuzatu. Oni su predpostavili da je razređenje indikatora u perfuzatu posljedica novostvorenog CSF, tj. veća količina stvorenog CSF će dovesti do većeg razređenja indikatora. Zbog toga je ta metoda indirektna i bilo koja greška koja dovodi do krive interpretacij stupnja razređenja indikatora će dovesti do upitnih i često kontradiktornih rezultata vezanih uz količinu stvorenog CSF. U skladu s Heiseyevom jadnadžbom, Vf ne bi trebala ovisiti o brzini ventrikulocisternalne perfuzije. Međutim, pokazano je da Vf ovisi o brzini perfuzije10 i da se za vrijeme perfuzije indikator također djelomično apsorbira u priležeće tkivo. Moguće je da je opažena ovisnost Vf o brzini perfuzije uzrokovana upravo opaženom apsorpcijom indikatora. Zbog toga je na anesteziranim mačkama vršena ventrikulocisternalna perfuzija kod visokih (252,0 mL/min) i niskih brzina perfuzije (65,5 mL/min) i izračunavana je Vf pomoću eksperimentalnih, kao i korigiranih vrijednosti indikatora, korigiranih upravo za količinu apsorbiranog indikatora. Budući da je (usprkos korekciji) dobivena razlika od 12,4 mL/min između niskih (15,0 mL/min) i visokih (27,4 mL/min) brzina perfuzije, očito je da se metoda ventrikulocisternalne perfuzije ne može uzeti u obzir kao pouzdana metoda za mjerenje količine stvorenog CSF.

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