Altered intestinal microcirculation is the critical event in the development of necrotizing enterocolitis

Episodes of apnea, desaturation and bradycardia and the development of necrotizing enterocolitis in preterm infants: a case-control study

OBJECTIVE

To investigate for any association between episodes of apnea, desaturation and bradycardia and necrotizing enterocolitis (NEC).

METHODS

Case-control study in infants of gestational age < 30 weeks. For each NEC case we selected two controls. During the period from 2001 to 2007, data were extracted from the nurse's notes of the patient's medical records. A p < 0.05 was statistically significant.

RESULTS

A total of 38 out of 394 infants had NEC (9.6%). There were no significant differences in baseline characteristics between the 2 groups, except for a lower proportion of infants who were receiving breast milk in the NEC group (p = 0.02). There was no difference in the overall number of apneas & bradycardias or severe episodes of desaturation & bradycardia between the 2 groups.

CONCLUSION

No association between episodes of apnea, severe desaturations or bradycardia and development of NEC was observed in this preterm population.

Intestinal hemodynamics and oxygenation in the perinatal period

The neonatal gastrointestinal tract is a site of intense anabolic and metabolic activity, as it is responsible for the assimilation of nutritional intake and exhibits accelerated growth shortly after birth. The hypermetabolic state of the gastrointestinal tract requires sufficient blood flow and oxygen delivery to sustain adequate oxygen consumption to meet these metabolic needs. Therefore, an understanding of the mechanisms regulating intestinal vascular perfusion in the normal state and during pathophysiological conditions in the perinatal period is important to elucidate potential contributions to the development of intestinal pathologies in the neonate. The goal of this review is to summarize the available literature on the regulation of intestinal blood flow and oxygenation in the fetus and newborn in normal states and during pathological stress.

Intestinal Microcirculatory Flow Alterations in Necrotizing Enterocolitis are Improved by Direct Peritoneal Resuscitation

Vasoconstriction of the neonatal intestinal microvasculature is a central mechanistic event in development of necrotizing enterocolitis. We hypothesized that topical treatment of the intestine with dialysate fluid would ameliorate the vasoconstriction in necrotizing enterocolitis (NEC). NEC was induced in experimental groups. Control animals were delivered vaginally and dam-fed (control group). Neonatal pups underwent laser Doppler flow study of the terminal ileum to determine real-time blood flow in the intestinal microvasculature. After baseline flow was determined, dialysis solution was added to the peritoneal cavity and alterations in microcirculation were recorded. Baseline ileal blood flow in the control group was significantly higher than in NEC rat pups at 48 hours post delivery ( P < 0.05), but not at 24 hours ( P = NS). Ileal blood flow increased in all groups after adding dialysate ( P < 0.05), improving ileal blood flow in the 48-hour NEC group and reaching the baseline level of the 48-hour control group ( P < 0.05). Our data shows blood flow to be higher in 48-hour controls as compared with 24-hour controls suggesting a time-dependency in the development of intestinal vasoregulatory processes. All groups had an increase in blood flow with dialysate treatment. This may represent a novel initial therapy to improve intestinal ischemia in human necrotizing enterocolitis.

Direct peritoneal resuscitation augments ileal blood flow in necrotizing enterocolitis via a novel mechanism

PURPOSE

Endothelin-1, prostaglandins (PGs), and nitric oxide (NO) have been implicated in the intestinal microvascular dysfunction of necrotizing enterocolitis (NEC). We hypothesized that direct peritoneal resuscitation (DPR) dilates the intestinal microvasculature and improves blood flow independent of these mechanisms.

METHODS

Rat pups were assigned by litter to experimental NEC or CONTROL groups. Laser Doppler flowmetry evaluation of intestinal microvascular blood flow was studied at baseline, with mediator blockade (endothelin-A receptor, endothelin-B receptor, PG synthesis, or NO synthase) and with DPR. Repeated-measures analysis of variance test was applied with Tukey-Kramer honestly significant difference test (P < .05).

RESULTS

At baseline, NEC animals demonstrated significantly decreased ileal blood flow as compared with CONTROLs (P < .05). Endothelin-A receptor and PG inhibition increased flow in the intestinal microvasculature, but this was significantly augmented by the addition of DPR (P < .05). Blockade of NO synthase decreased intestinal blood flow, which was overcome with addition of DPR (P < .05).

CONCLUSION

Ileal blood flow was significantly reduced in NEC animals as compared with CONTROLs. The addition of DPR to the peritoneum increased ileal blood flow significantly in all groups in spite of blockade of these known vasoactive mechanisms. Direct peritoneal resuscitation may be a novel strategy to improve intestinal blood flow in NEC.