Continuous Monitoring of the Monro-Kellie Doctrine: Is It Possible?

Abstract

The Monro-Kellie doctrine describes the principle of homeostatic intracerebral volume regulation, which stipulates that the total volume of the parenchyma, cerebrospinal fluid, and blood remains constant. Hypothetically, a slow shift (e.g., brain edema development) in the irregular vasomotion-driven exchanges of these compartmental volumes may lead to increased intracranial hypertension. To evaluate this paradigm in a clinical setting and measure the processes involved in the regulation of systemic intracranial volume, we quantified cerebral blood flow velocity (CBFv) in the middle cerebral artery, arterial blood pressure (ABP), and intracranial pressure (ICP), in 238 braininjured subjects. Relative changes in compartmental compliances C a (arterial) and C i (combined venous and CSF compartments) were mathematically estimated using these raw signals through time series analysis; C a and C i were used to compute an index of cerebral compliance (ICC) as a moving correlation coefficient between C a and C i . Conceptually, a negative ICC would represent a functional Monro-Kellie doctrine by illustrating volumetric compensations between C a and C i . Clinical observations show that Lundberg A-waves and arterial hypertension were associated with negative ICC, whereas in refractory intracranial hypertension, a positive ICC was observed. In subjects who died, ICC was significantly greater than in survivors (0.46 -0.027 versus 0.22 -0.017; p < 0.01) over the first 5 days of intensive care. The mortality rate is 5% when ICC is less than 0, and 43% when above 0.7. ICC above 0.7 was associated with terminally elevated ICP (chi-square p = 0.026). We propose that the Monro-Kellie doctrine can be monitored in real time to illustrate the state of intracranial volume regulation.

The correlation between pulsatile intracranial pressure and indices of intracranial pressure-volume reserve capacity: results from ventricular infusion testing

“…11,37 It remains a topic of debate as to how the various indices of pulsatile ICP analyzed with modern computerized methods are associated with the intracranial pressure-volume reserve capacity. 5,7,21,24 Hence, further studies are needed to determine the association between pulsatile ICP and ICE.…”

Modelling the Ability of Rheoencephalography to Measure Cerebral Blood Flow

“…We used this approach to calculate new values of the electrical parameters because, according to the Monro-Kellie relation, the internal volume of the skull remains constant during the cardiac cycle, so the relative volumes of the brain, blood, and CSF should vary. These variations can be modelled either using elasticity theory [11], or by direct modification of the electrical parameters of the finite elements. The complexity of the mechanical model of the brain, which takes into account elasticity and fluid flow, is very high.…”

Experimental model of intracranial hypertension with continuous multiparametric monitoring in swine

“…Kim et al 10 recently reported that changes in intracranial venous, arterial, and CSF compartments could be mathematically estimated using serial analysis, allowing the calculation of a cerebral complacency index (CCI) as a correlation coefficient of changes in compartments. The authors Figure 2.…”