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Propofol fails to attenuate the cardiovascular response to rapid increases in desflurane concentration
M Daniel1, E I Eger, R B Weiskopf
1Department of Anaesthesia, Glasgow Royal Infirmary, Scotland, United Kingdom.
Background:
A rapid increase in desflurane concentration to greater than 1 MAC transiently increases heart rate, arterial blood pressure, and circulating catecholamine concentration. Because propofol decreases sympathetic outflow, it was hypothesized that propofol would blunt these responses.
Methods:
To test this hypothesis, five healthy male volunteers were studied three times. After induction of anesthesia with 2 mg.kg-1 propofol, anesthesia was maintained with 4% end-tidal desflurane in oxygen (0.55 MAC) via an endotracheal tube for 32 min. On separate occasions, in random order, either no propofol or 2 mg.kg-1 propofol was administered either 2 or 5 min before increasing end-tidal desflurane concentration from 4% to 8%.
Results:
Without propofol pretreatment, the increase to 8% desflurane transiently increased heart rate (from 63 +/- 3 beats/min to 108 +/- 5 beats/min, mean +/- SEM; P < 0.01), mean arterial pressure (from 73 +/- 1 mmHg to 118 +/- 6 mmHg; P < 0.01), and epinephrine concentration (from 14 +/- 1 pg.ml-1 to 279 +/- 51 pg.ml-1; P < 0.05). There was no significant change in norepinephrine concentration (from 198 +/- 37 pg.ml-1 to 277 +/- 46 pg.ml-1). The peak plasma epinephrine concentration was attenuated by each propofol pretreatment (158 +/- 35 pg.ml-1, propofol given 2 min before, and 146 + 41 pg.ml-1, propofol given 5 min before; P < 0.05), but neither propofol pretreatment modified the cardiovascular or norepinephrine responses.
Conclusions:
Although able to blunt the increase in epinephrine concentration, propofol 2 mg.kg-1 propofol does no attenuate the transient cardiovascular response to a rapid increase in desflurane concentration to greater than 1 MAC.
Insights
Propofol blunts the epinephrine surge from desflurane but does not affect the transient cardiovascular response. This study investigated propofol
Area of Science:
- Anesthesiology
- Pharmacology
- Cardiovascular Physiology
Background:
- Rapid increases in desflurane concentration (greater than 1 Minimum Alveolar Concentration [MAC]) transiently elevate heart rate, blood pressure, and catecholamines.
- Propofol is known to decrease sympathetic outflow, suggesting a potential to mitigate these desflurane-induced responses.
Purpose of the Study:
- To investigate whether propofol administration attenuates the cardiovascular and catecholamine responses to a rapid increase in desflurane concentration.
Main Methods:
- Five healthy male volunteers received anesthesia with desflurane.
- Anesthesia was maintained with 4% end-tidal desflurane (0.55 MAC) after induction with propofol.
- On separate occasions, volunteers received either no propofol or 2 mg/kg propofol 2 or 5 minutes before increasing desflurane to 8% (greater than 1 MAC).
Main Results:
- Increasing desflurane to 8% significantly increased heart rate, mean arterial pressure, and epinephrine levels without propofol.
- Propofol pretreatment attenuated the peak plasma epinephrine concentration but did not significantly alter norepinephrine levels.
- Neither propofol pretreatment regimen modified the transient cardiovascular responses (heart rate and blood pressure) to the increased desflurane concentration.
Conclusions:
- While propofol (2 mg/kg) can blunt the epinephrine response to a rapid increase in desflurane concentration, it does not attenuate the associated transient cardiovascular effects.
- These findings suggest that propofol's sympatholytic effects may be insufficient to overcome the direct stimulation caused by high desflurane concentrations on the cardiovascular system.