Evaluation of the effects of the addition of atropine during propofol/remifentanil induction of anesthesia on hemodynamics, microvascular blood flow and tissue oxygenenation in patients undergoing ophthalmic surgery.

Remifentanil is a widely used potent intravenous opioid with the advantage of
having a short time of action. Compared to other opiates however remifentanil
generates more intense hemodynamic side-effects. In ophthalmic surgery the
specific anesthesiological challenges necessitate the administration of a
combination of relatively high doses of hypnotics and analgesics on the one
hand and a short time for postoperative recovery from anesthesia on the other.
A primary concern during this deep propofol/remifentanil anesthesia is
preserving hemodynamic stability and adequate tissue oxygenation. Previous
research of our group has revealed that atropine has an exceptionally
beneficial effect on hemodynamics as well as on tissue oxygenation. Our
research (included in the attachments) has demonstrated a clinically very
significant 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/or SctO2. In this former
research, we administered the atropine only after the onset of clinically
important hypotension, as is usual in clinical practice. However, since most
patients eventually require some type of pharmacological hemodynamic support,
we consider it beneficial to anticipate a decrease in blood pressure to pursue
maximal hemodynamic homeostasis. Therefore, we hypothesize that administration
of intravenous atropine during induction of propofol/remifentanil may have a
positive effect on the hemodynamic profile and peripheral and cerebral tissue
oxygenation during and after induction of anesthesia. Establishing the most
beneficial therapeutic intervention to reduce the hemodynamic side effects of
pharmacological hemodynamic support and improve tissue oxygenation during
propofol/remifentanil anesthesia may also improve our understanding of the
distinctive effects of remifentanil on the autonomous nervous system as well as
the interplay between macro- and microcirculation.

To determine whether there are clinically important beneficial effects of the
addition of atropine during induction of anesthesia with propofol/remifentanil
on the hemodynamic profile and on peripheral and cerebral tissue oxygenation
and microvascular blood flow in patients undergoing ophthalmic surgery.

Prospective double-blind randomized placebo-controlled study

All patients will receive a standard anesthesia based on propofol and
remifentanil. During the induction of anesthesia patients will randomly receive
either atropine (0.5 mg in 1ml) or saline (1 ml). If necessary, hemodynamic
support will be provided by continuous infusion of norepinephrine as in normal
clinical practice to maintain adequate perfusion pressure defined as mean
arterial pressure >= 60 mmHg. Hemodynamic parameters as well as peripheral and
cerebral tissue oxygenation and microvascular blood flow will be monitored
noninvasively and recorded

All patients will receive standardized anesthesia treatment with propofol and
remifentanil. In routine clinical practice for this anesthesia and procedure,
depending on the experience of the anesthesiologist, atropine is given
preventively at induction of anesthesia or not. The only intervention in this
study is that patients will be randomised to be preventively treated with
atropine or not. Both preventive administration of atropine or waiting for
clinical signs of bradycardia before atropine administration are considered
*good clinical practice*. If necessary, additional hemodynamic support will be
provided. All additional monitoring devices are noninvasive.
Therefore this study will not extent the burden or risks for patients