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Biomedical subjects

L Cussen

Publications and source records attributed to L Cussen.

6 recordsLinked to original sources
PubMed1992

Organ weight/bodyweight ratios: growth rates of fetal organs in the latter half of pregnancy with a simple method for calculating mean organ weights.

Ratios for major organ weights compared with bodyweights of 1023 stillborn and liveborn babies who lived less than 72 h are presented. The ratios were calculated for 2 week increments of gestational age from 20 to 43 weeks and clearly depict the relative growth of fetal organs during the last half of pregnancy. The ratios for heart and for kidneys were virtually constant for the whole period of gestation examined. The ratios for thymus and spleen increased between 20 and 30 weeks gestation and then became constant, although the ratio for the spleen dropped slightly during the last 6 weeks. The ratios for liver, lungs and adrenals decreased between 20 and 30 weeks gestation, and then steadied. The ratio for brain declined very slowly throughout the period examined. An observation of practical importance was that all organ weight/bodyweight ratios were virtually constant after 30 weeks gestation. Approximate mean organ weight/bodyweight ratios between 30 and 43 weeks gestation were: heart 0.007, lungs 0.02, spleen 0.003, liver 0.04, kidneys 0.01, adrenals 0.003, thymus 0.004 and brain 0.13. By multiplying the mean ratio by the total bodyweight, the approximate mean weight for a particular fetal organ can be calculated in situations where charts of normal organ weights are not at hand.

Body Weight↗
PubMed1990

Mean organ weights of an Australian population of fetuses and infants.

Charts of organ weights for an Australian population of fetuses and infants are presented. The organ-weight charts were compiled from 1337 stillbirths and liveborn babies whose gestational age ranged from 20 to 43 weeks, and who lived less than 72 h. Macerated stillbirths, multiple births and malformed organs were excluded. Pathological conditions aside from malformations were not excluded, leading to higher standard deviations compared with currently used charts. The organ weights are presented in two-week increments from 20 to 43 weeks' gestation as means, with standard deviations.

Australia↗
PubMed1990

Regional cerebral blood flow after hemorrhagic hypotension in the preterm, near-term, and newborn lamb.

Developmental changes in regional cerebral blood flow (CBF) responses to hemorrhagic hypotension during normoxia and normocapnia were determined using radioactively labeled microspheres to measure flow to the cortex, brainstem, cerebellum, white matter, caudate nucleus, and choroid plexus in three groups of chronically catheterized lambs: 90- to 100-d preterm fetal lambs (n = 9); 125- to 136-d near-term fetal lambs (n = 9); and newborn lambs 5- to 35-d-old (n = 8). Heart rate, central venous pressure, and arterial blood pressure were monitored continuously and arterial blood gas tensions, pH, Hb, and oxygen saturation together with regional CBF were measured periodically. Hemorrhagic hypotension produced a mean decrease in arterial blood pressure of 27 +/- 4, 23 +/- 2, and 41 +/- 4% in the three groups, respectively, whereas reinfusion of the lamb's blood resulted in a return to control blood pressure within 3% in all three groups. In the pre-term fetal lamb, CBF decreased significantly in all regions during hypotension. In the near-term fetal lamb, only blood flow to the cortex decreased significantly during hypotension. In the newborn lamb, only the choroid plexus demonstrated a significant decrease in blood flow during hypotension. The lower limit of regional CBF autoregulation was identical to the resting mean arterial pressure in fetal life but significantly lower in newborn lambs. These experiments demonstrate for the first time that vulnerability to hypotension decreases with increasing maturity and that the brainstem, the phylogenetically oldest region of the brain, is the least vulnerable to the effects of hypotension at any age in the lamb model.

Animals↗
PubMed1988

Developmental changes in regional cerebral blood flow in fetal and newborn lambs.

Developmental changes in regional cerebral blood flow (CBF) were determined using radioactively labeled microspheres to measure flow to the cortex, brain stem, cerebellum, white matter, caudate nucleus, and choroid plexus in three groups of chronically catheterized lambs under physiological conditions: 90- to 100-day preterm fetal lambs (n = 14), 125- to 136-day near-term fetal lambs (n = 11), and newborn lambs 5-44 days old (n = 10). We continually monitored heart rate, central venous pressure, and mean arterial blood pressure (MAP) and periodically measured arterial blood O2 and CO2 tensions (PaO2, PaCO2, respectively), pH, hemoglobin, and oxygen saturation (SaO2). The regional CBF measurements (ml.100 g-1.min-1) revealed that in all three age groups the high flow areas are the choroid plexus and caudate nucleus, whereas the lowest flow area is the white matter. There is, however, a different hierarchy of regional CBF in utero (cortex less than cerebellum and brain stem) compared with extrauterine life in the newborn lamb (cortex and cerebellum greater than brain stem). Analysis of regional cerebral oxygen delivery [CBF times arterial oxygen content (CaO2)] demonstrated a progressively increasing oxygen transport to the cortex with increasing gestational maturity and after birth. Oxygen transport to the brain stem, cerebellum, and white matter increased with gestational age, but did not increase after birth. Relationships between regional CBF and natural physiological variations of cardiorespiratory parameters (PaO2, SaO2, CaO2, pH, PaCO2, and MAP) were assessed using regression analysis. Correlations of regional CBF with PaO2 and SaO2 suggest that cerebral perfusion is not primarily determined by CaO2 when variations occur within the physiological range.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗