Relationship between propofol pharmacokinetic variation and haemodynamic changes during anaesthesia induction and knee-chest positioning in surgical patients with propofol TCI anaesthesia

Résumé

For long years, it was thought that anaesthetic management did not influence patient’s outcome. Surgical morbidity and long-term mortality were attributed to patient’s comorbidity, malignance of the disease, risk infection and type of surgery. Nowadays, there is an increasing evidence that intraoperative anaesthetic management can influence long-term patient outcomes. In the last two decades, surgical mortality rates have been falling and, in part, this is due to a huge improvement in anaesthesia related factors and safety. For an anaesthesiologist, perioperative care is no longer the simple fact of administrating the anaesthetic drug and maintaining the patient “asleep”. Direct-guided fluid therapy, maintaining intraoperative normothermia, minimizing blood transfusion and avoiding low mean arterial pressure and deep hypnotic level are additional procedures the anaesthesiologist is responsible for and that will probably improve patient’s outcome and decrease surgical mortality. Hypotension after induction of anaesthesia is quite common and more prevalent during the late post-induction period and before skin incision (5-10 minutes after), generally thought to be clinically irrelevant. Nowadays, there is some evidence that small haemodynamic changes, such as hypotension, even for small periods, are associated with poor patient outcomes, because they have the potential to cause an ischemia–reperfusion injury which may be manifested as dysfunction of any vital organ, like acute kidney and myocardial injury. Intra-operative management of hypotension is usually guided by conventional monitoring (systolic blood pressure and MAP) but these parameters could mask low levels of blood flow and oxygen delivery, even for short periods, leading to major surgical complications and longer hospital stays.