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Biomedical subjects

B M Holland

Publications and source records attributed to B M Holland.

18 recordsLinked to original sources
PubMed1992

Optimization of the blood for oxygen transport and tissue perfusion in critical care.

In present practice, patients in intensive care are managed with subnormal haematocrit values and oligovolaemia. Optimization of the blood for oxygen transport in preterm infants in intensive care yields major benefits in their prognosis. A rational basis is described for this optimization in terms of the circulating blood volume and haematocrit, represented by circulating red cell volume (mass). Extrapolation of these lessons in haematological management is proposed for adult patients in critical care, so as to reduce dependence on respiratory support and minimize clinical complications and costs.

Adult↗
PubMed1990

Total circulating red cells versus haematocrit as the primary descriptor of oxygen transport by the blood.

Peripheral haematocrit (PCV) is the traditional target and monitor in many transfusion regimens. Without negating the importance of PCV as a determinant of whole blood viscosity, the present article outlines two important reasons why the red cell volume (RCV) should replace PCV in the central target role during blood transfusion in intensive care and other emergency situations: 1. PCV reflects both RCV and plasma volume (PV) and is therefore not directly proportional to the total blood oxygen carrying capacity. At best, the relationship between PCV and RCV is hyperbolic and this is often overlooked when relating the two parameters in practice. At worst, the hyperbolic relationship is unreliable because PV and RCV can vary independently and the PCV is a fluctuating ratio of variable numbers. 2. PCV is not a good indicator of blood volume (BV), which is another important determinant of oxygen delivery to tissues and a crucial parameter in intensively managed patients. BV is directly proportional to RCV and this relationship also is often overlooked in clinical practice. The recommended values for RCV are 30 ml/kg in men. 25 ml/kg in women and between 30 ml/kg and 45 ml/kg in neonates within the first week of life.

Adult↗
PubMed1990

Increased concentrations of D-dimers in newborn infants.

The concentrations of D-dimers (the D fragments of fibrinogen) were measured in blood from 15 preterm infants, and 45 born at full term, to establish normal ranges. The adult normal range is less than 0.25 mg/l; 31 of the 60 infants (52%) had values less than 0.25 mg/l, in 16 (27%) they were 0.25-0.5, in eight (13%) 0.5-1, in three (5%) 1-2, and in two (3%) 2-4. D-dimer concentrations measured during the neonatal period should be interpreted with caution.

Fibrin Fibrinogen Degradation Products↗
PubMed1990

Biotin labeling of red cells in the measurement of red cell volume in preterm infants.

Determination of circulating red cell volume (RCV) in anemic preterm infants is, in theory, a better indicator of transfusion needs than Hb concentration. Our study reports the results of RCV measurement using biotin labeling of red cells on 40 occasions in preterm infants of 25-34 wk gestation. In 20 infants, who had estimations made within 24 h of birth, the RCV varied between 17.7 and 66 mL/kg. Twenty measurements were made at a later age at the time of a blood transfusion. RCV values were between 13.1 and 41.5 mL/kg before transfusion. In 13 infants, RCV was determined simultaneously using two methods, biotin and dilution of autologous HbF with donor HbA at transfusion. There was no significant difference between the results of RCV estimations using these two methods. Our study demonstrates that biotin labeling is an effective method for determining RCV in preterm infants.

Biotin↗
PubMed1988

Definitive estimate of rate of hemoglobin switching: measurement of percent hemoglobin F in neonatal reticulocytes.

The transition from fetal to adult erythropoiesis starts at 32-36 wk postconception. The rate of this switchover has been controversial. Studies of globin chain synthesis by reticulocytes in vitro have indicated gradual switching with a time for 50% reduction in fetal Hb synthesis ("half-time") of more than 6 wk. This may not accurately reflect fetal/adult Hb synthetic balance in vivo. By contrast, histochemical studies and also indirect mathematical analysis of postnatal changes in circulating fetal Hb and adult Hb may imply abrupt patterns of switching with half-times of less than 1 wk. We have resolved this discrepancy by direct measurement of the changing proportions of fetal and adult Hb in reticulocytes prepared by flourescence activated cell sorting from 10 full-term cord and 45 preterm postnatal blood samples. This method overcomes problems both of extrapolation from in vitro measurements and of mathematical analysis. We find a gradual transition from fetal Hb to adult Hb synthesis. The half-time is approximately 16-18 wk. Values of fetal Hb in reticulocytes were on average higher than predicted from in vitro synthesis studies. We find considerable individual variation. Infants differ in their switching behaviour, many showing prolonged dependence on fetal Hb.

Age Factors↗
PubMed1987

Lessons from the anemia of prematurity.

In our view, three main lessons stem from consideration of the refractory early anemia of prematurity (REAP). These are: (1) Hemoglobin concentration is not enough to describe the anemia. (2) The REAP may be clinically very severe but is often easily missed. It interacts with and worsens other causes of anemia in preterm infants, such as blood losses. Its pathogenesis is multifactorial, but it is generally interrelated with short gestation and its other complications. (3) Prevention, prophylaxis, and if necessary, adequate management are very important.

Anemia, Neonatal↗
PubMed1986

Outbreak of Salmonella eimsbuettel in newborn infants spread by rectal thermometers.

Over a six-week period there were 25 episodes of Salmonella eimsbuettel infection in newborn infants, mothers, and staff in a modern maternity hospital with 3600 annual deliveries. The probable source was a mother and her child, and the organism was spread by rectal thermometers in the labour suite and one of the wings (wards). When the thermometers were withdrawn from use and correctly disinfected the outbreak in babies ceased. Environmental cross-infection of staff was halted by closure, cleaning, and disinfection of the clinical area mainly affected. Some babies had diarrhoea but quickly recovered, and none came to harm. The infected staff had no symptoms and returned to duty after three negative cultures. Measurement of temperature is still an important observation in the care of newborn infants, but for everyday care it is recommended that rectal thermometry be discontinued and replaced by axillary measurement.

Cross Infection↗
PubMed1986

Determination of red-cell mass in assessment and management of anaemia in babies needing blood transfusion.

A new method for the rapid determination of red-blood-cell mass (RCM) in infants needing blood transfusion is described. RCM is estimated from the fall in the baby's fetal haemoglobin level resulting from transfusion of a known mass of adult-haemoglobin-containing red cells. In severe blood loss and refractory anaemias in preterm infants, in addition to the red-cell deficit, the plasma volume is low, leading to a falsely high haematocrit of about 0.30, which conceals a deficiency of 50-70% in circulating red cells. Red-cell transfusion in such infants based on haematocrit often fails to restore RCM to normal, leading to repeated transfusions. The frequency of transfusions may be reduced by giving enough red cells fully to correct the deficiency based on RCM estimation.

Adult↗
PubMed1985

The flow of blood cell suspensions through 3 microns and 5 microns Nuclepore membranes: a comparison of kinetic analysis with scanning electron microscopic examinations.

This study was designed to investigate the effect of red and white cells on the flow of dilute suspensions of blood cells through 3 microns and 5 microns Nuclepore membrane filters. The rate of flow of blood cell suspensions through 3 microns or 5 microns membranes declines continually due to occlusion of pores by slow cells. The cells which occlude 3 microns pores exceed the number of white cells about seven-fold. Electron microscopic examination of a used membrane confirms that these slow cells are not white cells but are red cells which are visibly damaged. With 5 microns membranes, the number of slow cells is entirely consistent with them being white cells. Again, electron microscopic examination confirms that 5 microns pores are occluded by white cells. With both types of membrane, the same kinetic analysis is valid and yields information about the behaviour of red cells during the filtration procedure.

Blood Cells↗
PubMed1985

New insulating material in maintenance of body temperature.

Flectalon, web of aluminised polyvinylchloride fibres, has been formulated to minimise radiant heat losses and to provide conventional insulation. Critical temperature determinations were used to assess the insulating efficacy of this and other swaddling materials in infants. The critical temperature for a baby 2 to 10 days old was 31 degrees C when naked and 23 degrees C when wrapped in a Silver Swaddler or a sheet and two blankets. The use of a quilt made with Thinsulate or Hollofil with a mass per unit area of 160 to 180 g/m2 reduced the critical temperature to 19.5 degrees C, while Flectalon of comparable weight reduced the critical temperature to 13.8 degrees C: Flectalon is thus an efficient insulator. The risk of overheating was studied by monitoring swaddled babies, rectal temperatures at various ambient temperatures. Some forms of swaddling caused increases in rectal temperatures at "normal' hospital temperatures, implying risks from warmer environments and assessments of swaddling materials should, therefore, include medical evaluation of efficiency and safety. Flectalon merits assessment in other groups at risk from hypothermia.

Aluminum↗
PubMed1984

Evaluation of the contribution of red and white cells to the flow of suspensions of washed blood cells through 3 micron Nuclepore membranes.

This study was designed to investigate a method of analysis which can quantitate the contribution of white cells to the flow of washed suspensions of blood cells. Such an analysis would obviate the need to remove white cells when studying the filterability of normal and abnormal red cells. The flow of suspensions of washed blood cells through a 3 micron Nuclepore membrane declines continually due to the occlusion of pores and the degree of pore occlusion is reduced significantly by the removal of the 'buffy coat' during the preparation of the suspension. These findings are in complete agreement with many other reports. However, a detailed kinetic analysis of the results suggests strongly that the white cell population makes a small contribution to the degree of pore occlusion which is caused largely by approximately 1% of the total red cell population. Despite the phenomenon and extent of pore occlusion, a kinetic analysis of the complete non-linear flow profile allows a measure of the deformability of red cells from filtration studies of washed but unfractionated blood cells.

Blood Flow Velocity↗
PubMed1978

Nonphysiological anaemia of prematurity.

Clinical and haematological findings at the nadir of the refractory, early anaemia of prematurity were compared in a study of 95 preterm infants. 53% of 30 babies less than 32 weeks' gestational age at birth had abnormal clinical features resulting from anaemia at its nadir, with a combination of tachycardia, tachypnoea, dyspnoea and feeding difficulties, diminished activity, and pallor. The expression 'available oxygen', derived from the Hb concentration and Hb-O2 affinity, correlated more closely with clinical features of anaemia that did the Hb concentration alone. A formula is presented that predicts the 'available oxygen', provided the Hb concentration and post-conceptual age are known; this avoids the need for direct measurement of Hb-O2 affinity. Clinical anaemia is common in preterm infants with Hb concentrations of up to 10.5 g/dl, consequent on the high O2 affinity of fetal Hb. This is the first description of any common clinical consequence of high Hb-O2 affinity.

Age Factors↗
PubMed1978

Simple and versatile method for measuring oxygen consumption in infants.

A simple, rapid, and accurate method for measuring oxygen consumption in infants is described. Expired gas is entrained in a stream of air drawn through a gently applied face mask. Oxygen consumption is derived from (1) gas flow rate, measured with a flowmeter, and (2) the fall in oxygen concentration of the gas mixture, measured with a paramagnetic analyser. A measurement can be made at the bedside within 2 minutes without disturbing the infant. In 17 mature 2-day-old neonates mean oxygen consumption was 6.52 ml/kg per min, SD 0.90, similar to that previously reported using less simple methods,

Evaluation Studies as Topic↗