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The effect of prophylactic phenylephrine on systemic hypotension during induction of anaesthesia with propofol in patients over 55 years old.

BACKGROUND
Induction of anaesthesia with propofol is often associated with a significant decrease in arterial pressure, especially in the older population. The aim of this study is to determine the efficacy of phenylephrine in two different doses i.e. 100mcg and 200mcg, given during induction to counteract the anticipated hypotensive effect of propofol in older patients aged over 55 years.


METHODS
Seventy-two ASA physical status I - II patients aged 55 years or older were randomly allocated to group 1 (received propofol mixed with normal saline), group 2 (propofol mixed with 100mcg of phenylephrine) or group 3 (propofol mixed with 200mcg of pheynylphrine). Anaesthesia was induced with fentanyl 1.5mcg/kg and propofol 2mg/kg (mixed with the study drug). Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) were recorded at 1 minute intervals for up to 5 minutes after induction.


RESULTS
SBP, MAP and DBP decreased significantly after induction in the control group and group 2 (phenylephrine 100mcg). In contrast, SBP was maintained to near baseline for the first two minutes after induction using phenylephrine 200mcg in group 3, and similar trends were seen with MAP and DBP at a lesser magnitude.


CONCLUSION
Phenylephrine 200mcg is more effective than 100mcg in attenuating propofol induced hypotension, especially during the first two minutes after induction, in patients aged 55 years and above.