Dexmedetomidine Versus Propofol in Vitreoretinal Surgery

Alpha2 adrenergic receptor agonist have been used increasingly as a new armamentarium to
provide sedative/hypnotic, analgesic, anxiolytic and sympatholytic effects in the
perioperative settings. Dexmedetomidine, a selective and specific alpha2- adrenoceptor
agonist has unique properties that makes it an almost ideal sedative drug for monitored
anesthesia care in procedures under local or regional block. Unlike other drugs use for
sedation, dexmedetomidine induces sedation that is similar to natural sleep (readily
arousable) without causing respiratory depression. It attenuates the stress-induced
sympathoadrenal response seen with laryngoscopy and intubation. It has anesthetic and
opioid sparing effects, hence it may be a useful adjunct to general anesthesia and
monitored anesthesia care in patients susceptible to narcotic induced respiratory
depression. Another unique property of dexmedetomidine is that its sedative effect is
reversible with Atipamezole. A previous study wherein dexmedetomidine has been used in
procedures under local and regional block had shown that it provides effective sedation and
better operating condition without significant respiratory depression. As a supplement to
general anesthesia, it has been shown to provide stable hemodynamics. However, it is
associated with some adverse events such as hypertension, hypotension and bradycardia, these
commonly occur during bolus administration of the recommended dose of 1ug/kg.
Post-operatively it can cause nausea and vomiting. Vitreoretinal surgery requires either an
injection of local anesthetic within the muscle cone (retrobulbar block),or into the
periorbital space (peribulbar block). This can be done individually or in combination. This
surgery can also be done under a safer technique of retrobulbar block that is given using a
sub-tenon's approach through a snip peritomy; a blunt cannula can be used with this
technique mitigating the complications of retrobulbar hemorrhage or inadvertent injection
into the optic nerve sheath or perforation of the globe using a sharp needle. The anesthetic
goal is to provide an immobile and uncongested operative field. Hemodynamic stability of
the patient is also important since some patients that require this procedure are elderly
with co-morbid conditions such as hypertension, diabetes mellitus and CAD. In our study we
would like to investigate if Dexmedetomidine alone and in a reduced dose can prevent or
reduce the incidence of adverse effects, provide hemodynamic and respiratory stability,
provide adequate sedation with patient and surgeon satisfaction and compare it with
Propofol.

Objectives:

Primary:

1. Adequate sedation

2. Hemodynamic and respiratory stability

3. surgeon and pt satisfaction

Secondary:

1. Incidence of nausea and vomiting

2. Time to achieved " street fitness " status

3. Post op hemodynamic stability

Inclusion Criteria:

- ASA rating of I-III

- good renal and liver function

Exclusion Criteria:

- renal and hepatic insufficiency

- uncontrolled diabetes

- uncontrolled hypertension

- severe cardiac disease Class III or IV

- heart blocks

- chronic use of sedatives, narcotics, alcohol or illicit drugs

- allergy to either propofol or dexmedetomidine

- pregnancy or inability to tolerate technique of the study drugs