Cerebral perfusion

Certain neutral technetium complexes can be used to image cerebral perfusion (Fig. 4). Those in Figure 4a and 4b have been approved for clinical use. Two other complexes (Fig. 4c and 4d) were tested in early clinical trials, but were not developed further. An effective cerebral perfusion agent must first cross the blood brain barrier and then be retained for the period necessary for image acquisition. Tc-bicisate is retained owing to a stereospecific hydrolysis in brain tissue of one of the ester groups to form the anionic complex TcO(ECD) , which does not cross the barrier. This mechanism of retention is termed metaboHc trapping. 

Fig. 4. Structures of cerebral perfusion agents (a) Tc(V)0(HMPA0) ( " Tc-exametazine [103613-48-7]), whem...

Technetium-99m exametazime [(RR,3 3)-4,8-diaza-3,6,6,9-tetramethylundecane-2,10-dionebisoxime] is used as an adjunct in the detection of altered regional cerebral perfusion in stroke. The kit for the preparation of the radiopharmaceutical is suppHed as a single dose vial. 

Gottschalk C, Beauvais J, Hart R, et al Cognitive function and cerebral perfusion during cocaine abstinence. Am J Psychiatry 158 540-545, 2001... 

Hunter GJ, Hamberg LM, Ponzo JA, Huang-Hellinger FR, Morris PP, Rabinov J, Farkas J, Lev MH, Schaefer PW, Ogilvy CS, Schwamm LH, Buonanno FS, Koroshetz WJ, Wolf GL, Gonzalez RG. Assessment of cerebral perfusion and arterial anatomy in h3fperacute stroke with three-dimensional functional CT early clinical results. Am J Neuroradiol 1998 19 29-37. 

FurukawaM, Kashiwagi S, Matsunaga N, Suzuki M, Kishimoto K, Shirao S. Evaluation of cerebral perfusion parameters measured by perfusion CT in chronic cerebral ischemia comparison with xenon CT. J Comput Assist Tomogr 2002 26 272-278. 

Georgiadis D, Schwarz S, Kollmar R, Baumgartner RW, Schwab S. Influence of inspiration expiration ratio on intracranial and cerebral perfusion pressure in acute stroke patients. Intensive Care Med 2002 28(8) 1089-1093. 

Rosner MJ, Coley IB. Cerebral perfusion pressure, intracranial pressure, and head elevation. J Neurosurg 1986 65(5) 636-641. 

Fan JY. Effect of backrest position on intracranial pressure and cerebral perfusion pressure in individuals with brain injury a systematic review. J Neurosci Nurs 2004 36(5) 278-288. 

Meixensberger J, Baunach S, Amschler J, Dings J, Roosen K. Influence of body position on tissue-po2> cerebral perfusion pressure and intracranial pressure in patients with acute brain injury. Neurol Res 1997 19(3) 249-253. 

Chan K-H, Miller JD, Dearden NM, Andrews PJ, Midgley S. The effect of changes in cerebral perfusion pressure upon middle cerebral artery blood flow velocity and jugular bulb venous oxygen saturation after severe brain injury. J Neurosurg 1992 77(1) 55-61. 

Maintain cerebral perfusion pressure (CPP) between 60-80 mmHg... 

Iyo, M., Namba, H., Yanagisawa, M. et al. Abnormal cerebral perfusion in chronic methamphetamine abusers a study using 99MTc-HMPAO and SPECT. Prog. Neuropsychopharmacol. Biol. Psychiatry. 21 789, 1997. 

Measurements of regional cerebral blood flow by PET and of cerebral perfusion by SPECT often detect functional abnormalities before CT or MRI identifies morphological abnormalities 945 The PET method is a valuable tool for the estimation of regional glucose and oxygen metabolic rates and cerebral blood flow 946 PET and SPECT combined with principles of receptor binding permit imaging of receptors in the intact brain 946... 

Brain infarction was the first clinical application of SPECT. Decreases in relative cerebral perfusion were imaged by SPECT for diagnosis. Decreased rCBF is visualized in the form of decreased signal on SPECT and PET. The sensitivity and specificity of brain SPECT for infarct localization are 85.5% and 97.6%, respectively [99]. Blood-flow imaging is useful in the evaluation of response to therapy in patients with cerebrovascular diseases [100]. 

Baird, A. E., Austin, M. C., McKay, W. J. and Donnan, G. A. Sensitivity and specificity of 99mTc-HMPAO SPECT cerebral perfusion measurements during the first 48 hours for the localization of cerebral infarction. Stroke 28 976-980,1997. 

The goal of sympathomimetic therapy is to augment both coronary and cerebral perfusion pressures during the low-flow state associated with CPR. These agents increase systemic arteriolar vasoconstriction, thereby improving coronary and cerebral perfusion pressure. They also maintain vascular tone, decrease arteriolar collapse, and shunt blood to the heart and brain. 

To study the effect of PGDN on cerebral blood flow, Godin et al. (1995) injected male Sprague-Dawley rats (through a jugular vein cannula) with PGDN at 0.1 to 30 mg/ kg and measured cerebral blood flow with a fiberoptic laser-Doppler flow probe in contact with the brain. Following a small initial drop in cerebral perfusion that lasted 1 min, blood flow rapidly increased and reached a maximum 2 min after injection. The increase in perfusion was correlated with dose, but due to the small number of animals and individual variability, a clear dose-response relationship was not obtained. 

Complex 61 (99mTc(V)-D,L-HM-PAO, Ceretec) is an approved cerebral perfusion imaging agent for evaluation of stroke. The tetradentate... 

The lipophilic complex 99mTc(IV)-L,L-ECD (62) with a deprotonated L,L-ethylcysteine dimer as ligand, is clinically used as a cerebral perfusion imaging agent. It crosses the blood-brain barrier and... 

Fig. 10. X-ray crystal structure of the cerebral perfusion imaging agent 61 (Ceretec) the D,L-form of ligand HM-PAO is used. Adapted from (275).

Often, CVP is left out of this equation as it is normally negligible. In order to maintain cerebral perfusion when ICP is raised, the MAP must also be elevated. 

Rose JS, Branchey M, Buydens-Branchey L, Stapleton JM, Chasten K, Werrell A, Maayan ML. (1996). Cerebral perfusion in early and late opiate withdrawal a technetium-99m-HMPAO SPECT study. Psychiatry Res. 67(1) 39 7. 

Nordstrom CH. 2003. Assessment of critical thresholds for cerebral perfusion pressure performing bedside monitoring of cerebral energy metabolism. Neurosurg Focus... 

Nordstrom CH, Reinstrup P, Xu W, Gardenfors A, Ungerstedt U. 2003. Assessment of the lower limit for cerebral perfusion pressure in severe head injuries by bedside monitoring of regional energy metabolism. Anesthesiology 98(4) 809-814. 

Stahl N, Ungerstedt U, Nordstrom CH. 2001b. Brain energy metabolism during controlled reduction of cerebral perfusion pressure in severe head injuries. Intensive Care Med 27(7) 1215-1223. 

Alvarez, X.A., Mouzo, R., Pichel, V., et al. (1999) Double-blind placebo-controlled study with dticoline in APOE genotyped Alzheimer s disease patients. Effects on cognitive performance, brain bioelectrical activity, and cerebral perfusion. Meth. Find. Exp. Clin. Pharmacol., 21, 633-644. 

The symptoms of overdose are to some extent predictable from the antimuscarinic and adrenolytic activity of these drugs. Excitement and restlessness, sometimes associated with seizures, and rapidly followed by coma, depressed respiration, hypoxia, hypotension and hypothermia are clear signs of TCA overdose. Tachycardia and arrhythmias lead to diminished cardiac function and thus to reduced cerebral perfusion, which exacerbates the central toxic effects. It is generally accepted that dialysis and forced diuresis are useless in counteracting the toxicity, but activated charcoal may reduce the absorption of any unabsorbed drug. The risk of cardiac arrhythmias may extend for several days after the patient has recovered from a TCA overdose. 

Bonne O, Gilboa A, Louzoun Y, Brandes D, Yona I, Lester H, Barkai G, Freedman N, Chisin R, Shalev AY (2003b) Resting regional cerebral perfusion in recent posttraumatic stress disorder. Biol Psychiatry 54 1077-1086... 

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