PubMed · 10602919
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J M Rubin. 1999. Power doppler.. https://doi.org/10.1007/pl00014064
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BACKGROUND: Blood flow parameters in the superior mesenteric artery (SMA) change with vasoconstriction or vasodilatation of the intestinal vascular bed. In cases of severe growth retardation as a result of haemodynamic disturbances, the blood flow changes persist into postnatal life. OBJECTIVE: To assess early changes of Doppler sonographic blood flow parameters in the SMA for prediction of later intestinal motility disturbances in preterm infants and tolerance of enteral feeding during the first week of life. MATERIALS AND METHODS: Doppler sonographic blood flow parameters in the SMA were measured on the first day of life and the following 5 days in 478 neonates with a birth weight below 1,500 g. According to the Doppler results, the neonates were divided into two groups-those with pathological parameters and those with normal blood flow parameters. Correlations between blood flow parameters, the development of intestinal dysmotility and the tolerated amount of enteral feeding were calculated. RESULTS: Pathological blood flow parameters were observed in 148 neonates (group 1) and normal blood flow parameters in 330 neonates (group 2). Intestinal motility disturbance occurred in 125 neonates (83%) of group 1 and 47 neonates (15%) of group 2. Neonates in group 2 tolerated significantly more feed by the fifth day of life than neonates in group 1. Postnatal adaptation did not differ between the two groups, although the majority of neonates with intestinal dysmotility were small for gestational age. The predictive value of blood flow parameters for prediction of intestinal motility revealed high sensitivity and specificity by the first postnatal day, 2 or 3 days before development of clinical signs of intestinal dysmotility. There was a strong negative correlation between pathological pulsatility index on day 1 and the quantity of tolerated enteral feeding on day 5. CONCLUSIONS: Pathological blood flow parameters in the SMA can predict problems of intestinal motility and tolerance of enteral feeding. With the early detection of these problems a prompt start of adequate therapy to avoid complications is possible.
OBJECTIVE: The objective was to evaluate cerebral hemodynamics in young children with acute subdural hematoma (SDH) and the impact of surgical treatment using transcranial Doppler (TCD). DESIGN: The design was a prospective study of infants with SDH requiring surgical evacuation. SETTING: The setting was the neuro intensive care unit of a university hospital. INTERVENTIONS: Indications for surgical evacuation were based upon clinical and radiological arguments. Surgery included emergency needle aspiration followed by external or/and internal shunting as required. A TCD evaluation was performed before needle aspiration, and after each surgical drainage procedure. It included a pressure provocation test to assess cerebral compliance. Preoperative and postoperative middle cerebral artery (MCA) velocities, Gosling pulsatility (PI) and Pourcelot resistivity (RI) indexes and compliance were compared with Student's t-test, or Fisher's exact test as indicated. MEASUREMENTS AND MAIN RESULTS: Out of 26 infants, 23 (88%) had injuries that had possibly been inflicted, and 3 had accidental injuries. Initial TCD evaluation demonstrated intracranial hypertension with decreased diastolic velocity, increased PI and RI, and decreased compliance. Surgical evacuation resulted in statistically significant improvement in cerebral hemodynamics (diastolic velocity: 17.2+/-10 cm/s vs. 31.1+/-10 cm/s, p<0.0015, PI: 2.5+/-1.3 vs. 1.4+/-0.8, p<0.002, RI: 0.8+/-0.2 vs. 0.6+/-0.1, p<0.005) in all but 3 infants, who eventually died. Surgical drainage (primary shunting or external drainage) was needed in 23 infants and resulted in further improvement in cerebral hemodynamics. Finally, 73% of the infants made a good recovery. CONCLUSIONS: Children with acute bilateral HSD have a high incidence of increased intracranial pressure as assessed by TCD. Surgical evacuation improves cerebral hemodynamics. TCD could be used for assessing the need for, and the efficiency of surgical drainage.
During exercise, reflex renal vasoconstriction maintains blood pressure and helps in redistributing blood flow to the contracting muscle. Exercise intolerance in heart failure (HF) is thought to involve diminished perfusion in active muscle. We studied the temporal relationship between static handgrip (HG) and renal blood flow velocity (RBV; duplex ultrasound) in 10 HF and in 9 matched controls during 3 muscle contraction paradigms. Fatiguing HG (protocol 1) at 40% of maximum voluntary contraction led to a greater reduction in RBV in HF compared with controls (group main effect: P <0.05). The reduction in RBV early in HG tended to be more prominent during the early phases of protocol 1. Similar RBV was observed in the two groups during post-HG circulatory arrest (isolating muscle metaboreflex). Short bouts (15 s) of HG at graded intensities (protocol 2; engages muscle mechanoreflex and/or central command) led to greater reductions in RBV in HF than controls (P <0.03). Protocol 3, voluntary and involuntary biceps contraction (eliminates central command), led to similar increases in renal vasoconstriction in HF (n=4). Greater reductions in RBV were found in HF than in controls during the early phases of exercise. This effect was not likely due to a metaboreflex or central command. Thus our data suggest that muscle mechanoreflex activity is enhanced in HF and serves to vigorously vasoconstrict the kidney. We believe this compensatory mechanism helps preserve blood flow to exercising muscle in HF.