Table 2.

Cardiorespiratory and sympathetic responses to systemic phenylephrine

	Baseline	Phenylephrine Dose 1	Phenylephrine Dose 2
Heart rate, beats/min	61 ± 2	60 ± 2	56 ± 3*†
Systolic blood pressure, mmHg	145 ± 4	144 ± 4	150 ± 4*†
Diastolic blood pressure, mmHg	77 ± 2	79 ± 2*	83 ± 2*†
Mean blood pressure, mmHg	98 ± 2	100 ± 2	106 ± 3*†
Respiratory rate, breaths/min	12 ± 1	12 ± 1	12 ± 1
Tidal volume, l/breath	0.51 ± 0.08	0.51 ± 0.08	0.57 ± 0.07
Minute ventilation, ml/min	5.8 ± 0.8	6.0 ± 0.7	6.7 ± 0.8
Epinephrine, pg/ml	58 ± 10	60 ± 7	54 ± 9
Norepinephrine, pg/ml	160 ± 18	132 ± 19*	132 ± 20
Burst frequency, bursts/min	24 ± 2	23 ± 2	11 ± 2*†
Burst incidence, bursts/100 heartbeats	41 ± 3	39 ± 4	21 ± 3*†
Mean burst area, AU/min	1.3 ± 0.4	1.2 ± 0.4	0.5 ± 0.1
Action potential frequency, APs/min	238 ± 73	222 ± 63	91 ± 25*†
Action potential incidence, APs/burst	8.9 ± 2.3	8.9 ± 2.0	7.7 ± 1.8
Action potential incidence, APs/100 heartbeats	406 ± 128	377 ± 102	166 ± 42*†
Mean cluster incidence, clusters/burst	4.6 ± 0.7	4.6 ± 0.7	3.9 ± 0.5
Max cluster incidence, clusters/burst	8.6 ± 1.0	8.6 ± 1.0	6.9 ± 0.7*†
Max cluster number	14.6 ± 2.3	15.1 ± 2.2	8.9 ± 0.8*†

Data are means ± SE from n = 9 unless otherwise noted (dose 2: epinephrine and norepinephrine, n = 6). Data are reported as a 3-min average during the final dose (phenylephrine dose 2, range 0.4–1.0, average 0.62 ± 0.08 µg·kg⁻¹·min⁻¹) and during approximately half of the maximum dose (phenylephrine dose 1, range 0.2–0.6, average 0.29 ± 0.05 µg·kg⁻¹·min⁻¹). Data were analyzed with a 1-way repeated-measures ANOVA. Normality was assessed with the Shapiro-Wilk test. If not normally distributed, a Friedman repeated-measures ANOVA on ranks was conducted [minute ventilation, mean burst area, action potential incidence (AP/burst), max cluster incidence]. Pairwise comparisons were done with the Holm-Sidak method.

^*P < 0.05 vs. baseline.

^†P < 0.05 vs. phenylephrine dose 1.