Systemic and Pulmonary Effects of Vasopressors and Inotropes in the Neonate

A comparison of combination dopamine and epinephrine treatment with high-dose dopamine alone in asphyxiated newborn piglets after resuscitation

BACKGROUND

When asphyxiated neonates require additional cardiovascular support to moderate doses of dopamine infusion, controversy exists on the differential hemodynamic effects of two approaches (adding a second inotrope vs. increasing dopamine dosage). We hypothesized that high-dose dopamine (HD) would be detrimental to systemic and regional perfusion as compared with dopamine and epinephrine (D + E) combination therapy using a swine model of neonatal hypoxia-reoxygenation (H-R).

METHODS

Twenty-seven piglets (1-4 d, 1.5-2.5 kg) were used for continuous monitoring of systemic arterial pressure (mean arterial pressure, MAP) and pulmonary arterial pressure (PAP), cardiac output (cardiac index, CI), and carotid (carotid artery flow index, CAFI), superior mesenteric (superior mesenteric artery flow index), and renal arterial flows. H-R piglets underwent 2 h of hypoxia followed by 2 h of reoxygenation before drug infusion (2 h).

RESULTS

The hemodynamics of H-R piglets deteriorated gradually after reoxygenation. HD and D + E infusions improved CI similarly (both groups vs. control; P < 0.05). Both regimens increased MAP (P < 0.05) but not PAP, with decreased PAP/MAP ratio in D + E piglets. Both regimens improved CAFI and superior mesenteric artery flow index, with decreased mesenteric vascular resistance in HD-treated piglets. No significant effect on renal perfusion was observed.

CONCLUSION

In H-R newborn piglets treated with a moderate dose of dopamine, adding epinephrine or further increasing dopamine improved systemic hemodynamics similarly; these treatments have differential effects on the pulmonary and mesenteric circulations.

Effect of dopamine on peripheral perfusion in very-low-birth-weight infants during the transitional period

INTRODUCTION

Dopamine is one of the most frequently used inotropic drugs in neonatal intensive care units (NICUs); however, it does not seem to improve outcomes in premature infants. Given that the ultimate aim of cardiovascular management is to stabilize and maintain organ perfusion, an understanding of dopamine's effects on organ blood flow will help in judging when to use dopamine and how to titrate the dosage. Such an approach can lead to improved outcomes. This study aimed to evaluate the effects of dopamine on peripheral perfusion in very-low-birth-weight (VLBW) infants within 72 h of birth.

METHODS

This prospective observational study identified and sampled 44 instances of initiation of dopamine treatment or increase in dopamine dose in 29 VLBW infants. Blood pressure, heart rate, and skin and subcutaneous blood flow were measured and compared before and after each instance.

RESULTS

Blood pressure and skin and subcutaneous blood flow in the lower limbs increased after initiation of dopamine treatment or after dose increase.

DISCUSSION

Dopamine increases blood pressure as well as skin and subcutaneous blood flow in VLBW infants despite its supposed vasoconstrictive action, indicating that it increases both perfusion pressure and blood flow and is devoid of overwhelming peripheral vasoconstrictive effects.

Milrinone is preferred to levosimendan for mesenteric perfusion in hypoxia-reoxygenated newborn piglets treated with dopamine

INTRODUCTION

There is little information regarding the comparative hemodynamic effects of adding milrinone or levosimendan to dopamine infusion in hypoxia-reoxygenated (H-R) newborns.

RESULTS

Severely hypoxic piglets had cardiogenic shock with depressed cardiac index (CI) and mean arterial pressure (MAP). The hemodynamics deteriorated gradually after initial recovery upon reoxygenation. Heart rate and CI improved with milrinone (D+M) and levosimendan (D+L) administration (P < 0.05 vs. control). Both regimens improved carotid arterial flow and carotid vascular resistance; D+M additionally improved superior mesentric arterial flow (all P < 0.05 vs. control). No effect was found on renal arterial flow or elevated lactate state with either regimen. D+M piglets also had a lower myocardial oxidized/reduced glutathione ratio (P < 0.05 vs. control).

DISCUSSION

In conclusion, adding milrinone or levosimendan to dopamine similarly improved systemic hemodynamics in H-R newborn piglets. Milrinone also improved mesenteric perfusion and attenuated myocardial oxidative stress.

METHODS

Twenty-eight piglets (1-4 d, 1.5-2.5 kg) were instrumented for continuous monitoring of systemic MAP and pulmonary arterial pressure (PAP), CI, and carotid, superior mesenteric, and renal arterial flows. Piglets were randomized with blinding to sham-operated, H-R control (saline), and H-R dopamine (10 μg/kg/min) with D+M or D+L groups. H-R piglets underwent H-R followed by 2 h of drug infusion after reoxygenation. Tissue was collected for biochemical/oxidative stress testing and histological analysis.

Changes in skin and subcutaneous perfusion in very-low-birth-weight infants during the transitional period

BACKGROUND

Conventional parameters of circulation that are routinely used in neonatal intensive care units, including blood pressure, have been reported to be inadequate in improving prognosis of very-low-birth-weight (VLBW) infants. Recently, the importance of evaluating the blood flow to each organ, including both vital and nonvital organs, has been increasingly recognized.

OBJECTIVES

To study the changes in peripheral perfusion occurring in VLBW infants of less than 32 weeks' gestation during the extrauterine transitional period.

METHODS

In 32 VLBW infants of less than 32 weeks' gestation, forehead blood flow (FBF) and lower-limb blood flow (LBF) were measured for 48 h after birth using a novel laser Doppler flowmeter, and the indices of vascular resistance were estimated. Superior vena cava (SVC) blood flow was measured by echocardiography. Changes in these variables of circulation as well as the correlations were evaluated.

RESULTS

Both FBF and LBF significantly increased at 24 h, while the SVC flow remained unchanged over the same period. Both forehead and lower-limb vascular resistance indices significantly decreased at 24 h. LBF was negatively and positively correlated with estimated upper body vascular resistance and SVC flow, respectively.

CONCLUSIONS

The increase in the peripheral blood flow along with the decrease in the peripheral vascular resistance indices, without an increase in the systemic blood flow at 24 h of age, indicated vasodilation in skin and subcutaneous tissue during the transitional period in VLBW infants. FBF and LBF can be useful parameters as indicators of both peripheral and systemic circulation.