Intraoperative monitoring

Chapter 25 introduced some basic generic principles applicable to many measurement and monitoring techniques. Chapter 43 introduces those principles not covered in Chapter 25 and discusses in detail the clinical applications and limitations of the many monitoring techniques available to the modern clinical anaesthetist. It starts with non-invasive blood pressure measurement, including clinical and automated techniques. This is followed by techniques of direct blood pressure measurement, noting that transducers and calibration have been discussed in Chapter 25. This is followed by electrocardiography. There then follows a section on the different methods of measuring cardiac output, including the pulmonary artery catheter, the application of ultrasound in echocardiography, pulse contour analysis (LiDCO™ and PiCCO™), and transthoracic electrical impedance. Pulse oximetry is then discussed in some detail. Depth of anaesthesia monitoring is then described, starting with the electroencephalogram and its application in BIS™ monitors, the use of evoked potentials, and entropy. There then follow sections on gas pressure measurement in cylinders and in breathing systems, followed by gas volume and flow measurement, including the rotameter, spirometry, and the pneumotachograph, and the measurement of lung dead space and functional residual capacity using body plethysmography and dilution techniques. The final section is on respiratory gas analysis, starting with light refractometry as the standard against which other techniques are compared, infrared spectroscopy, mass spectrometry, and Raman spectroscopy (the principles of these techniques having been introduced in Chapter 25), piezoelectric and paramagnetic analysers, polarography and fuel cells, and blood gas analysis.