Table 2.

Hemodynamic responses throughout fentanyl vs. placebo administration

	Time Points								P Values
	T1: Pre-LBNP (postinfusion)		T2: −40 mmHg LBNP		T3: −50 mmHgLBNP		T4: End LBNP		Interaction	Drug factor	Timing factor
	FEN	PBO	FEN	PBO	FEN	PBO	FEN	PBO
MCAv, cm/s	64 ± 18	62 ± 14	61 ± 18	62 ± 14	58 ± 20	52 ± 15	43 ± 15	41 ± 10	0.1042	0.1681	<0.0001
ScO2, % oxygen saturation	59 ± 14	59 ± 12	59 ± 12	59 ± 11	59 ± 12	57 ± 12	55 ± 11	53 ± 12	0.5379	0.7800	<0.0001
CRI (AU)	0.91 ± 0.13	0.92 ± 0.04	0.70 ± 0.21	0.59 ± 0.22	0.43 ± 0.22	0.41 ± 0.20	0.31 ± 0.20	0.27 ± 0.17	0.0833	0.1666	<0.0001
Plasma [E], pg/mL					111 ± 71	86 ± 103	174 ± 208	119 ± 213	0.4667	0.1511	0.1299
Plasma [NE], pg/mL					425 ± 190	462 ± 207	811 ± 635	675 ± 563	0.1425	0.3854	0.0201
Systolic blood pressure, mmHg	127 ± 18	132 ± 13	116 ± 18	118 ± 14	113 ± 16	112 ± 12	75 ± 15	77 ± 12	0.1587	0.5846	<0.0001
Diastolic blood pressure, mmHg	71 ± 10	74 ± 6	70 ± 9	71 ± 5	70 ± 10	69 ± 5	49 ± 12	50 ± 8	0.1162	0.6032	<0.0001
RR, breaths/min	14 ± 4	15 ± 4	11 ± 3	12 ± 4	11 ± 4	13 ± 3	15 ± 5	16 ± 5	0.8946	0.0074	<0.0001
End-tidal CO2, mmHg	44 ± 5	44 ± 5	42 ± 7	41 ± 5	43 ± 8*	39 ± 6	37 ± 10*	31 ± 7	<0.0001	0.0370	<0.0001

Values are means ± SD. CRI, compensatory reserve index; [E], epinephrine concentration; FEN, fentanyl trial; MCAv, middle cerebral artery velocity; MSNA, muscle sympathetic nerve activity; [NE], norepinephrine concentration; PBO, placebo trial; RR, respiratory rate; ScO₂, frontal cortex oxygen saturation. Mixed effects model used for statistical analysis. *Statistical differences in end-tidal CO₂ compared with PBO with Holm–Bonferroni multiple comparisons post hoc testing, P < 0.05.