Comparison of the effects of atropine on haemodynamics and tissue oxygenation in anaesthesia with propofol and sufentanil versus propofol and remifentanil.

Induction of general anaesthesia with a combination of opiates and hypnotics
often induces vasodilation resulting in several haemodynamic effects such as a
decrease in blood pressure, heart rate and cardiac output. This haemodynamic
suppression may jeopardize tissue oxygenation, particularly cerebral
oxygenation. Previous research of our group (see attachments) has revealed that
atropine has an exceptionally beneficial effect on the determinants of tissue
oxygen delivery as well as on tissue oxygenation. We have demonstrated a
significant and clinically relevant increase in cardiac output (CO) and
cerebral tissue oxygenation (SctO2) for a desired increase in arterial blood
pressure. This is in steep contrast with the more usual clinical practice of
administrating classical vasoactive medication such as phenylephrine or
norepinephrine, since the two latter have an even negative effect on CO and
SctO2. In our previous research we used standardized target controlled
propofol/remifentanil infusions for induction and maintenance of anaesthesia.
It is known that remifentanil has more intense haemodynamic side-effects
compared to other opiates such as fentanyl, sufentanil or alfentanil. This
raises the question whether the beneficial effect of atropine is restricted to
propofol/remifentanil anaesthesia, or if this is equally valid during
anaesthesia of propofol combined with other opiates such as sufentanil.
Patients undergoing off-pump coronary artery bypass grafting (CABG) require a
long and deep general anaesthesia, which is usually performed with the
combination of drugs as mentioned above. Because these patients often
experience severe haemodynamic fluctuations they need to be closely monitored.

To investigate if there is a clinically important different effect of atropine
on haemodynamic variables, tissue oxygenation or microcirculation during
anaesthesia with either sufentanil and propofol or with remifentanil and
propofol.

Prospective, double-blind, randomized, interventional trial.

Patients will be randomised to receive anaesthesia with propofol and an
equipotent effect site concentration of either sufentanil or remifentanil
administered with target controlled infusion pumps.

In this study, we will provide standardized anaesthesia during routine
clinical practice. Both sufentanil are remifentanil are routinely used as
analgesic, with no definite advantage of either. Whether the patient will be
treated with sufentanil or remifentanil will be randomly determined. In these
patients an arterial catheter is routinely placed for continuous blood pressure
monitoring and blood sampling, consequently no additional punctures are
required for the use of the additional monitoring devices. This study will not
extent the burden for patients. As both agents are routinely used, patients
will have no additional risk or advantage compared to clinical practice.