Meperidine and skin surface warming additively reduce the shivering threshold: a volunteer study

Table 2 Confounding factors and results

	Control	Skin warming	Meperidine	Combined
Ambient temperature (°C)	22.6 ± 0.46	22.3 ± 0.5	22.1 ± 0.7	22.3 ± 0.7
Mean arterial pressure (mm Hg)	89.3 ± 7.1	87.9 ± 10.9	87.8 ± 9.4	88.6 ± 5.4
Heart rate (beats per minute)	65.3 ± 7.8	67.9 ± 11.7	62.5 ± 8.2	69.4 ± 9.6
SpO₂ (percentage)	99.3 ± 0.8	99.1 ± 0.6	98.6 ± 1.0	98.6 ± 0.9
PCO₂ (mm Hg)	5.1 ± 0.3	5.1 ± 0.5	5.0 ± 0.4	5.2 ± 0.8
Ringer lactate (ml/kg)	22.0 ± 4.5	50.6 ± 13.0^a	58.4 ± 12.8^a	84.3 ± 6.8^a
Meperidine (μg/ml)	N/A	N/A	0.98 ± 0.20	0.96 ± 0.19
Thermal comfort VAS	26.9 ± 5.0	28.9 ± 9.3	34.8 ± 8.6^b	43.6 ± 9.6^c
OAA/S scale	20 ± 0	19.9 ± 0.3	19.5 ± 0.7	19.4 ± 0.7
Mean skin temperature start (°C)^d	35.7 ± 0.4	35.8 ± 0.3	35.8 ± 0.2	35.8 ± 0.2
Mean skin temperature end (°C)^e	34.3 ± 0.7	35.6 ± 0.3^a	33.8 ± 0.6	35.4 ± 0.3^a
Core temperature vasoconstriction (°C)	36.5 ± 0.2	36.1 ± 0.2^a	35.8 ± 0.3^a	35.6 ± 0.3^a
Core temperature shivering (°C)	35.5 ± 0.2	34.9 ± 0.5^c	34.2 ± 0.3^a	33.8 ± 0.2^a

^ap < 0.01, ^bp = 0.04, ^cp = 0.01 (versus control). ^dMean skin temperature measured immediately before intravenous cooling. ^eMean skin temperature measured at the end of cooling. N/A, not applicable; OAA/S: Observer's Assessment of Alertness/Sedation; PCO₂, partial pressure of carbon dioxide; SpO₂, oxygen saturation as measured by pulse oximetry; VAS, visual analogue scale.

ISSN: 1364-8535