Excess nitric oxide is a mediator of the hypotension in septic shock.
Nitric oxide dilates vascular smooth muscle through activation of solu
ble guanylate cyclase. We report the increase in blood pressure caused
by methylene blue (MB), a soluble guanylate cyclase inhibitor, in fiv
e neonates with presumed septic shock unresponsive to colloids, inotro
pic agents, and corticosteroids. MB was given intravenously at a dose
of 1 mg/kg during a 1-hour period. MB increased blood pressure in each
patient (average, 33% +/- 20%). Blood pressure subsequently decreased
to near baseline values in three patients, who then received a second
infusion of MB. Blood pressure again increased in these patients. Thr
ee of five patients were weaned from inotropic support within 72 hours
. Three of five patients survived and were discharged home. We suggest
that MB increased blood pressure in these neonates with refractory hy
potension.