Heart disease, anaesthesia

For inhalational induction of anaesthesia in children, 6% sevoflurane in 50% nitrous oxide and oxygen is probably optimal. However, some anaesthetists consider it to be inferior to halothane for the management of the irritable or constricted airway and for anaesthesia for bronchoscopy. Sevoflurane is preferred for dental procedures as there is a lower risk of cardiac arrhythmias than with halothane, especially in children. In children with congenital heart disease, whereas the cardiac index is reduced by halothane it is preserved with sevoflurane. In adults, 8% sevoflurane is well tolerated and, provides rapid induction of anaesthesia without adversely affecting haemodynamic stability. 

Antihypertensives of all kinds hypotension may complicate anaesthesia, but it is best to continue therapy. Hypertensive patients are particularly liable to excessive rise in blood pressure and heart rate during intubation, which can be dangerous if there is ischaemic heart disease. Postoperatively, parenteral therapy may be needed for a time. 

Barankay A. Circulatory effects of pipecurium bromide during anaesthesia of patients with severe valvular and ischaemic heart diseases. Arzneimittelforschung 1980 30(2a) 386-9. 

Despite the obvious drawbacks of having to undergo an abdominal operation plus the associated dangers of anaesthesia in the very obese, most patients are pleased at the outcome. The results have been shown to be much better than for medical treatment in a randomised trial (Sjostrom et al. 1999). Surgery should be reserved for super-obese patients (BMI over 40), in whom the danger of associated morbidity from conditions such as diabetes mellitus and coronary heart disease are particularly high. The majority of obese subjects, who have a BMI between 30-40 should, in my view, be treated more conservatively. 

Nitrous oxide has both a direct depressant and sympthomimetic effect on the myocardium. In healthy patients these tend to counterbalance each other, the resultant effect being minimal cardiovascular depression. In patients with car-diovascular disease or who are taking conconcurrent medication with, e.g. 3 blockers, its depressant effect may be more obvious. Nitrous oxide supplementation of high-dose opioid-based anaesthesia may result in a reduction in cardiac output and heart rate although the mechanism of this is unclear. Nitrous oxide may have a venoconstrictor effect resulting in increased pulmonary vascular resistance, particularly in the presence of pulmonary hypertension. 

---