The PRST (pressure, rate, sweating, tears) score can be used to evaluate the depth of anesthesia. It uses physiologic responses to determine if sufficient anesthetic has been administered. The authors are from Oxford, England.
Limits of some classic measures for the depth of anesthesia:
(1) pupillary size may be affected by morphine, atropine or other medications
(2) muscle tone may be affected by use of muscle relaxants
Parameters:
(1) systolic arterial blood pressure
(2) heart rate
(3) sweating
(4) tears
Parameter
Finding
Points
systolic arterial blood pressure
less than control + 15 mm Hg
0
>= (control + 15) AND <= (control + 30 mm Hg)
1
greater than control + 30 mm Hg
2
heart rate
less than control + 15 beats per minute
0
>= (control + 15) AND <= (control + 30 beats per minute)
1
greater than control + 30 beats per minute
2
sweating
nil
0
skin moist to touch
1
visible beads of sweat
2
tears
no excess of tears in open eye
0
excess of tears in open eye
1
tear overflow from closed eyes
2
where:
• The control value is presumed to be the baseline levels prior to anesthesia.
• In Table III of Evans et al (1987) the values for systolic blood pressure and heart rate do not cover values equal to 15 or 30. I adjusted the table above to cover these values.
PRST score =
= SUM(points for all 4 parameters)
Interpretation:
• minimum score: 0
• maximum score: 8
• A score > 3 indicates an insufficient depth of anesthesia.
• During anesthesia the score is maintained in the range of 0 to 3.
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