Cardiocirculatory effects of acutely increased intracranial pressure and subsequent brain death

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Abstract
Hemodynamic instability and functional impairment of the donor heart arecurrently reported problems in organ transplantation. Actual shortage ofpotential donor hearts continues to raise controversial discussion aboutadequate donor management with regard to graft quality. In an experimentalopen chest model, physiopathologic effects of acutely induced, irreversibleintracranial hypertension (AIIHT) were investigated in situ with respect tohemodynamics, cardiac pump and muscle function, and hormonal parameters.Acutely induced irreversible intracranial hypertension was induced by rapidinflation of a subdural balloon catheter in 10 anesthetized dogs, fouranimals serving as controls. The observation period in both groups was 300min. Cardiocirculatory stability was maintained by continuous crystalloidvolume substitution without the use of inotropic or pressor agents. AfterAIIHT, three characteristic hemodynamic response phases have been observed:1) The "acute hyperdynamic phase" lasting up to 15 min with markedincreases of heart rate (HR), left ventricular pressure (LVP), cardiacoutput (CO) and myocardial contractility indices, 2) At the end of the"early restabilization phase", (60 min), these parameters returned close tocontrol levels, except HR (+50%) and systemic vascular resistance (SVR)(-40%), 3) During the "late restabilization phase", filling pressures, LVPand CO remained within control limits at low SVR, contractility indicesshowed a decreasing tendency. All assessed plasmatic hormones(Catecholamines, triiodothyronine (T3), thyroxine (T4), adrenocorticotropichormone (ACTH), cortisol and anti- diuretic hormone (ADH) showed acontinuous fall to levels significantly below control over the phases ofrestabilization. Acutely induced irreversible intracranial hypertensionleads to multifactorial hemodynamic and hormonal changes. At low SVR,cardiac pump function was preserved exclusively by continuous volumesubstitution, while myocardial contractility indicated a slight decrease.From this observed hemodynamic and functional state within the donororganism, no reliable prediction on graft functional capacity can bemade.

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