Table 1.

Cardiorespiratory and sympathetic responses to systemic nitroprusside

	Baseline	Nitroprusside
Heart rate, beats/min	61 ± 2	80 ± 3*
Systolic blood pressure, mmHg	146 ± 3	136 ± 4*
Diastolic blood pressure, mmHg	77 ± 2	73 ± 2*
Mean blood pressure, mmHg	99 ± 2	91 ± 2*
Respiratory rate, breaths/min	11 ± 1	11 ± 1
Tidal volume, l/breath	0.70 ± 0.14	0.81 ± 0.16
Minute ventilation, ml/min	6.7 ± 0.8	7.9 ± 1.0
Epinephrine, pg/ml	67 ± 11	82 ± 16
Norepinephrine, pg/ml	174 ± 14	215 ± 26
Burst frequency, bursts/min	25 ± 3	41 ± 3*
Burst incidence, bursts/100 heartbeats	41 ± 5	53 ± 4*
Mean burst area, AU/min	1.4 ± 0.2	2.8 ± 0.4*
Action potential frequency, APs/min	191 ± 35	439 ± 90*
Action potential incidence, APs/burst	8 ± 1	11 ± 2*
Action potential incidence, APs/100 heartbeats	326 ± 66	579 ± 129*
Mean cluster incidence, clusters/burst	4.5 ± 0.5	5.5 ± 0.7*
Max cluster incidence, clusters/burst	9.5 ± 1.0	10.9 ± 1.0*
Max cluster number	21.6 ± 2.7	24.4 ± 3.0*

Data are means ± SE from n = 13. Average final dose was 0.90 ± 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 [respiratory rate, minute ventilation, action potential (AP) incidence (APs/burst), max cluster number]. AU, arbitrary units. Pairwise comparisons were done with the Holm-Sidak method.

^*P < 0.05 vs. baseline.