The Levels of Anaesthetics in Heart Muscle During Heart Surgery

Coronary Sinus Blood Isoflurane Concentration in Patients Undergoing Heart Surgery

In the last few years, anaesthetic agents, Isoflurane used in heart surgery have shown some benefits to reduce the risk of heart muscle damage. Many research studies have been conducted to reveal the benefit relationship between Isoflurane and the risk of heart muscle injury during heart surgery. However, there is a knowledge gap regarding the optimal level of Isoflurane concentration to confer the benefit of heart muscle-protective properties. Therefore, this study is conducted to answer that question by measuring the Isoflurane concentration in the blood vessels. It also assesses whether Isoflurane concentration in the blood is correlated to the oxygenator exhaust level of Isoflurane in the heart-lung machine.

All patients who scheduled for an elective heart surgery in Royal Infirmary of Edinburgh using a heart-lung machine and the administration of ether-like anaesthetic, isoflurane will be recruited in this study. This is a pilot study to determine the concentration of isoflurane in heart muscle. Isaac and Michael (2005), Hill (1998), Julious (2005) have conducted survey/research to conclude that 30 sample sizes are adequate for a pilot study. Thus, investigators aim to recruit at least 30 sample sizes to allow data (standard deviation, mean etc.) used in sample size estimation for future studies.

The medical and surgical care plans for participants remain as usual in this study. In a normal practise, surgeons will insert a catheter into the blood vessels coming from the heart to deliver solution to stop the contraction of heart for heart procedure. At this moment, two blood samples of about two-teaspoonful in volume will be collected from the in-placed catheters in vein and aorta. Then, the blood samples will be sent to lab to measure the concentration of isoflurane in vein and aorta. Also, the reading of exhausted isoflurane gas on heart-lung machine are routinely monitored and recorded.

Inclusion Criteria:

• Age 18 years or older
• Scheduled for elective cardiac surgery requiring cardiopulmonary bypass.
• Anaesthetised using isoflurane as part of a balanced anaesthetic technique during heart-lung machine
• Patient has consented to participate
• Cardioplegia technique involves insertion of a coronary sinus catheter.

Exclusion Criteria:

• Emergency surgery or patient with malignancy
• Heart surgery undertaken without heart-lung machine
• Age younger than 18 years
• Unable or unwilling to provide informed consent
• Cardiac surgery that does not require cardiopulmonary bypass
• Anaesthetised using an total intravenous-based technique