Intestinal and Femoral Blood Flow Autoregulation in Developing Swine

Buckley, N. M.; Brazeau, Paul; Frasier, I. D.

doi:10.1159/000242536

Cited by 15 publications

(24 citation statements)

References 18 publications

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“…However, existing evidence suggests that its effect on blood pressure and heart rate is small or negligible at the doses used (26). Also, this anesthetic dosage maintains baroreceptor and peripheral vascular constrictor responses (27). From our data, a comparison of the control heart rates and blood pressure against a population of unaesthetized piglets (28) of the same age showed a slight difference in blood pressure (80 versus 82 mm Hg) and a resting heart rate about 15% higher (170 versus 198 bpm).…”

Section: Apnea and Hypertension Hypertension Developed In Syn-supporting

confidence: 49%

Cardiovascular and Neurophysiologic Changes during Graded Duration of Apnea in Piglets

1988

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ABSTRACT. To examine the interrelationship between the duration of apnea and changes in oxygen saturation, blood pressure, electroencephalogram (EEG), and heart rate, reflex apnea of 10, 20, 40, and 60 s duration was induced by stimulating the superior laryngeal nerves. Piglets (n = 11, age 5-14 days) were chronically instrumented for continuous monitoring of SaOz and blood pressure and for sampling arterial blood. Ventilation was recorded using whole body plethysmography and EEG and electrocardiogram were measured by acutely placed subcutaneous electrodes. Central apnea produced an immediate rise in blood pressure and a decrease in SaOz by 20 s. By 30 s into the apnea, EEG amplitude had already decreased. Major cardiac slowing did not occur until 80 s after the start of apnea. Hyperoxia delayed the start of desaturation, hypertension, and EEG attenuation. These data suggest that during superior laryngeal nerve-induced apnea in young piglets: 1) desaturation can reach profound levels rapidly, 2) EEG amplitude decreases substantially and becomes nearly isoelectric within 1 min, and 3) bradycardia is a late manifestation when compared to changes in oxygen saturation, blood pressure, and EEG. Apnea is a common problem in neonatal intensive care units with an incidence of 80-90% in infants weighing less than 1000 g (1,2). The importance of this phenomenon stems from the fact that apnea has been associated with cyanosis, bradycardia, altered neurologic state (3-7), and recently, with decreased cereL-21 blood flow (8).Despite the importance of apnea as a potentially detrimental phenomenon (9), the time of onset and the sequence of physiologic changes associated with apnea are unclear. Some infants require intervention at 10-15 s into an apnea, whereas some observations suggest that hypotonia and other indications of cerebral dysfunction do not occur until 45 s (3, 10). Similarly, the latency of bradycardia and its relationship to oxygen satura- Received May 19, 1987; accepted December 11, 1987 4(tion is variable. Bradycardia may occur early into an apnea, at a time before significant desaturation (3, 1 1, 12), but also can occur late in 40% of protracted apneas (1 3) or after the onset of EEG supression (14).The purpose herein was to examine the sequence of neurologic and cardiovascular consequences of graded periods of apnea. Prolonged neonatal apnea can be of variable etiology such as central nervous system immaturity, infection, metabolic disturbances, IVH, airway obstruction, and vagal reflex. For our studies, we used laryngeal stimulation to induce a central apnea secondary to reflex effect. In this way, apnea duration could be controlled by the duration of stimulus presentation and the cause for central apnea was consistent among experimental animals. Experiments were conducted in piglets because they have a similar time course of brain development and cardiovascular control systems as infants. Inasmuch as unterminated respiratory pauses up to 80 s duration were examined, similar studies on human infants could ...

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Section: Apnea and Hypertension Hypertension Developed In Syn-supporting

confidence: 49%

Cardiovascular and Neurophysiologic Changes during Graded Duration of Apnea in Piglets

1988

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“…Characterization of intestinal blood flow and oxygenation in the developing animal, however, has only recently been initiated. The intestine of neonatal piglets appears to be more vulnerable than that of older piglets to reductions in perfusion pressure (12,13) and hemorrhage (14,15) yet it appears to be less susceptible to hypoxic damage induced by acute venous hypertension (1 6).…”

Section: Discussionmentioning

confidence: 99%

Characterization of Intestinal Collateral Blood Flow in the Developing Piglet

Granger

1988

Pediatr Res

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ABSTRAn. Interest in the pathogenesis of neonatal necrotizing enterocolitis has prompted study of the intestinal circulation in developing animals. It is conceivable that poorly developed collateral channels may predispose the neonatal intestine to ischemic insults. We therefore characterized intestinal collateral blood flow in anesthetized and ventilated 1-day and 1-month-old piglets. Intestinal blood flow was measured with radioactive microspheres (15 hm diameter) before and after either 1) total occlusion of the superior mesenteric artery (SMA) or 2) occlusion of a distal Cjejunoileal) branch of the SMA. After total SMA occlusion in 1-day and 1-month-old piglets, perfusion of the intestine via collaterals from the celiac and inferior mesenteric arteries was not evident. Jejunal, ileal, and colonic (except rectal) blood flows fell to zero 30 min after ligation of the SMA. Ligation of a distal branch of the SMA in 1-month-old animals significantly reduced total wall (by 25%) and mucosal/submucosal (by 25%) blood flows in the occluded segment. Similar experiments in 1-day-old piglets produced significantly greater reduction in total (70%) and mucosa/submucosa (70%) blood flows. MuscleJserosa blood flows in both groups were not significantly different from control values. In conclusion, collateral perfusion of the intestine via the celiac and inferior mesenteric arteries is insignificant during acute SMA occlusion in the developing piglet. Although there is significant collateral blood flow within the SMA vascular network, perfusion between adjacent gut segments is less effective in preventing intestinal ischemia after occlusion of a branch of the SMA in neonates than in 1-month-old piglets. (Pediatr Res 24: 473-476, 1988) Abbreviations SMA, superior mesenteric artery 46SC, scandium 46 85SR, strontium 85The importance of intestinal collateral blood flow in prevention of intestinal ischemia is well recognized in humans (1-3) and adult animals (4-6). Quantitative studies in adult animals have demonstrated that collateral channels among the major arterial trunks and between adjacent bowel segments both play a role in prevention of intestinal ischemia. In the adult cat perfusion through collateral vessels after occlusion of the superior mesenteric artery maintains flow to the small intestine and proximal colon to within 30-65% of preocclusion flow (4). However, the efficiency of collateral perfusion via the celiac and inferior mesenteric arteries is substantially lower in dogs after SMA occlusion (5). In adjacent segments of canine small bowel, collateral vessels maintain blood flow in one segment at approximately 55% of its control level when the artery to that segment is totally occluded (6).Interest in the pathogenesis of neonatal necrotizing enterocolitis in premature infants has prompted study of the intestinal circulation in developing animals. Although intestinal collateral blood flow has been extensively studied in adult animals, there are no anatomical descriptions or quantitative studies of the collatera...

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“…A broad tape ligature was placed around the ab dominal aorta above the celiac artery and the tip of the aortic pressure catheter and used to compress the aorta against a convex plastic plate, as reported in detail previously [1,12]. Autoregulatory capability was tested in all three circulations simultaneously by a single-step decrease in aortic pressure to 70-90% of control level, within the previously established auto regulatory ranges at different ages [ 1.…”

Section: Determination O F Autoregulatory Capability O F Regional Cirmentioning

confidence: 99%

“…We have reported that, during the first postnatal month, swine do not exhibit rest ing hindlimb blood flow autoregulation [1] but vigorous neural control of the femoral circulation [2], We next tested two hypothe ses: that hindlimb work would be accompa nied by the appearance of autoregulatory ca 1 Supported by National Heart. Lung and Blood Institutes, grant HL-21865.…”

Section: Introductionmentioning

confidence: 99%

“…Experiments on developing swine were designed to take advantage of our previous findings that the renal and intestinal circulations are also un der neural control at birth [10. 11] and that autoregulation of blood flow to resting tissue is demonstrable only at a later age in the kid ney [12] and still later in the small intestine [1], Distal sciatic nerve stimulation (SNS) was employed to produce metabolic work that would challenge femoral autoregulatory capability and renal and intestinal blood flow redistribution to the hindlimb. Evi dence was sought regarding maturational differences in these responses.…”

Section: Introductionmentioning

confidence: 99%

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Regional Circulatory Responses to Hindlimb Work in Developing Swine

Buckley

Frasier²

1990

Neonatology

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Circulatory effects of hindlimb work were studied in 29 swine (aged 1 day to 1 month) anesthetized with pentobarbital. Femoral, renal and intestinal blood flow, resistance and autoregulatory capability were determined at different levels of hindlimb oxygen consumption before and during distal sciatic nerve stimulation. Increases in oxygen consumption were accompanied by hyperemia at all ages, but by increased oxygen extraction only in 2-week and 1-month-old animals, without evidence of autoregulation. Blood flow was consistently redistributed from the kidney and small intestine only in neonates. Older animals generally sustained autoregulation of renal and intestinal blood flows throughout experiments. We concluded that hindlimb work evokes age-related adjustments in regional blood flow that reflect the balance of neural and autoregulatory control.

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Intestinal and Femoral Blood Flow Autoregulation in Developing Swine

Cited by 15 publications

References 18 publications

Cardiovascular and Neurophysiologic Changes during Graded Duration of Apnea in Piglets

Cardiovascular and Neurophysiologic Changes during Graded Duration of Apnea in Piglets

Characterization of Intestinal Collateral Blood Flow in the Developing Piglet

Regional Circulatory Responses to Hindlimb Work in Developing Swine

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