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I.m. midazolam as premedication produces a concentration-dependent decrease in core temperature in male volunteers
T Matsukawa1, K Hanagata, M Ozaki
1Department of Anaesthesia, Yamanashi Medical University, Japan.
Abstract:
We tested the hypothesis that premedication with i.m. midazolam decreases core temperature dose-dependently. We studied six male volunteers, in random order, on 3 days: (1) no midazolam administration (control day), (2) midazolam 0.025 mg kg-1 i.m., (3) midazolam 0.075 mg kg-1 i.m. On the first day, subjects were maintained alert during a 30-min control period. On the second and third days, midazolam 0.025 or 0.075 mg kg-1 was administered i.m. Core temperatures were measured at the right tympanic membrane. Four adhesive skin surface probes were fixed on the chest, upper right arm, lateral calf and thigh. Finger tip perfusion was evaluated using forearm minus fingertip and calf minus toe, skin surface temperature gradients. Thirty minutes after midazolam i.m., the level of sedation in the volunteers was assessed. Peripheral venous blood was obtained immediately after the assessment of the level of sedation. Tympanic membrane temperatures after administration of midazolam 0.075 mg kg-1 i.m. were significantly lower than those on the control and midazolam 0.025 mg kg-1 i.m. days at 20 and 30 min. The decreases in tympanic membrane temperatures at 30 min after midazolam i.m. became larger as the volunteers were more deeply sedated. i.m. midazolam produced a concentration-dependent decrease in tympanic membrane temperature at 30 min after midazolam 0.025 and 0.075 mg kg-1 i.m. We conclude that midazolam impaired tonic thermoregulatory vasoconstriction, allowing core-to-peripheral heat redistribution in a dose-dependent manner after i.m. administration.
Insights
Intramuscular midazolam (intramuscular) reduces core body temperature in a dose-dependent manner. This effect is linked to impaired thermoregulatory vasoconstriction, leading to heat redistribution.
Area of Science:
- Anesthesiology and Pharmacology
- Thermoregulation and Physiology
Background:
- Midazolam is a common anesthetic agent.
- Its effects on core body temperature require further investigation.
Purpose of the Study:
- To investigate the dose-dependent effect of intramuscular midazolam on core body temperature.
- To explore the relationship between midazolam dosage, sedation levels, and thermoregulation.
Main Methods:
- A randomized, controlled study involving six male volunteers.
- Administration of intramuscular midazolam at doses of 0.025 mg/kg and 0.075 mg/kg, with a control day.
- Core body temperature measured via tympanic membrane; skin temperature and perfusion assessed using surface probes and gradients.
- Sedation levels evaluated 30 minutes post-administration.
Main Results:
- A significant decrease in tympanic membrane temperature was observed at 20 and 30 minutes after the higher midazolam dose (0.075 mg/kg).
- The reduction in core temperature correlated with increased sedation levels.
- Intramuscular midazolam demonstrated a concentration-dependent decrease in tympanic membrane temperature.
Conclusions:
- Intramuscular midazolam administration impairs tonic thermoregulatory vasoconstriction.
- This impairment facilitates core-to-peripheral heat redistribution in a dose-dependent manner.
- Midazolam's impact on body temperature is a significant consideration in clinical practice.