Early experiences of vasodilators and hypotensive anesthesia in children.

The physiological application of OHMS LAW explains the basis of hypotensive anesthesia. V = IR translates into: Pressure = Flow × Resistance or Blood pressure = Cardiac Output × Peripheral Resistance. If peripheral resistance is reduced by a vasodilator such as sodium nitroprusside (a short acting, vascular smooth muscle relaxant) or phenoxybenzamine (a long acting α adrenoreceptor antagonist), blood pressure will fall and vasoconstriction and bleeding will be reduced. A less desirable alternative to lowering blood pressure could be to reduce cardiac output by suppressing myocardial contractility using a ß(1) adrenoceptor antagonist or an inhalational agent such as isoflurane.

Neuroradiology investigations before scanning.

Coaxial tomography (CT) and magnetic resonance imaging (MRI) scans are so much part of neurological investigation these days and provide such detailed information that even thorough neurological clinical examination may be neglected. The investigations in common use forty years ago were pneumoencephalography, ventriculography in babies with hydrocephalus, and carotid angiography with the injection of X-ray contrast to outline the arteries.