Deep hypothermic circulatory arrest (DHCA), either alone or in combination with other perfusion strategies, has become the mainstay of vital organ protection for a variety of pathologies and surgical procedures that necessitate the complete cessation of blood flow. DHCA provides a near blood-less operating field, albeit of limited duration, while ameliorating the major adverse consequences of vital organ ischemia.Cooling of the brain – the organ at greatest ischemic risk – reduces cerebral metabolic rate, extending the period of "safe" ischemia from 3-4 minutes at normothermia to >20 minutes.

Despite the widespread availability of investigational tests and imaging techniques for the diagnosis and management of cardiac disease, eliciting a comprehensive history and performing a systematic physical examination remain essential clinical skills.

Since its introduction into clinical practice in the early 1950s, the indications for CPB have broadened, from operations on or within the heart, to include non-cardiac thoracic, abdominal and neurological procedures. The indications for CPB for non-cardiac surgery are shown in Box 28.1.

In animals that maintain body temperature within a tight range (homeotherms), thermoregulation represents the balance between heat production (thermogenesis) and heat loss. Thermogenesis occurs as a result of metabolic activity, particularly in skeletal muscle, the kidneys, the brain, the liver and (in infants) adipose tissue. Body heat is lost by conduction, convection, radiation and evaporation (Table 24.1). Cold-induced hypothalamic stimulation activates autonomic, extra-pyramidal, endocrine and behavioural mechanisms to maintain the core temperature.

The AV is composed of three semilunar cusps left (posterior), right (anterior) and non-coronary cusp, which are related to the three sinuses of Valsalva. The main functions of the AV are to permit unimpeded LV systolic ejection and to prevent regurgitation of the LV stroke volume during diastole. The normal adult AV orifice area is 2-4 cm2.

A comprehensive review of the complications of cardiac surgery would fill an entire volume. This chapter covers the more common and life-threatening complications. The reader is directed to the publications list under further reading.

As the indications for these devices has widened, the prevalence of permanent pacemakers (PPMs) and ICDs has increased. The complexity of these devices makes them susceptible to perioperative interference and inadvertent reprogramming, placing patients at greater risk of perioperative morbidity. Management guidelines are largely based on case series and expert consensus rather than prospective, randomized studies.

Introduction

Among the many roles that the anaesthetist has, risk assessment and risk modification are perhaps the most important. In order to manage peri-operative risk, the anaesthetist must have an understanding of the impact of co-existing medical conditions and concomitant drug therapy on normal physiology, and an appreciation of their likely interactions with both anaesthesia and surgery. When conducted effectively, pre-operative assessment decreases the risk of cancellations on the day of surgery and has the potential to reduce peri-operative morbidity and mortality.

Taking a detailed medical history and performing a competent physical examination remain the most efficient and effective ways of predicting and detecting significant co-morbid conditions. Pre-operative investigations should therefore be considered an adjunct to, rather than a substitute for, basic medical vigilance. Many pre-operative clinical investigations are justifiable on the grounds that they aid diagnosis (e.g. CT scan), assist in surgical planning (e.g. coronary angiography), permit more accurate risk stratification (e.g. exercise testing), guide risk-modification strategies or provide a ‘baseline’ before major surgery. A significant number of tests, however, are ordered ‘routinely’ without any clinical indication or justification.