Table 1.

Multimodality parameters: commonly used measurement devices, physiologic ranges, threshold at which early goal therapy should be considered, and clinical significance.

Modality	Means of monitoring	Physiologic range	Threshold	Clinical significance
Intracranial pressure	(1) Intraparenchymal monitor	<20 mmHg	>20–25 mmHg	Marker of cerebral edema and impending herniation.
	(2) Intraventricular monitor (EVD)
Cerebral perfusion pressure		60–70 mmHg	<60 mmHg	Indirect surrogate of CBF. Guide treatment of intracranial hypertension to optimize perfusion.
Cerebral blood flow	(1) TCD	Mean flow velocities	MCA mean flow velocity >200 cm/s	Detection of vasospasm and delayed cerebral ischemia in SAH.
		MCA 30–75 cm/s
		ACA 20–75 cm/s
		PCA 15–55 cm/s
		LR < 3	LR > 6	Differentiate hyperemia from vasospasm.
	(2) TDP	50 mL/100 g/min	<20 mL/100 g/min	Indicative of regional cerebral ischemia.
Cerebral oxygenation	(1) Juglar venous oximetry	50–80%	<50% or >80%	Indicative of global ischemia or hyperemia and tissue extraction of oxygen.
	(2) Licox™	35–40 mmHg	<20 mmHg	Indicative of regional hypoxia/hypoperfusion.
Cerebral metabolism	Microdialysis	Glucose 0.4–4.0 μmol/L	<0.4	Indicative of brain energy supply and demand.
		Lactate 0.7–3.0 μmol/L	>3.0
		Pyruvate unknown Lactate to pyruvate ratio <20	>40	Elevated LPR indicative of ischemia, anaerobic metabolism.
		Glutamate 2–10 μmol/L	>10	Increased glutamate and lactate earliest marker of ischemia followed by increased glycerol.
		Glycerol 10–90 μmol/L	>90

TCD: transcranial cranial doppler; TDP: thermal diffusion probe; MCA: middle cerebral artery; ACA: anterior cerebral artery; PCA: posterior cerebral artery; SAH: subarachnoid hemorrhage; LR: Lindegaard ratio; LPR: lactate to pyruvate ratio.