Blue blood

In a world of increasing immigration of a diverse range of nationalities, hereditary hemoglobin variants will be increasingly encountered, and should be considered in infants and children presenting with low saturations. We present a case report of an infant presenting with low oxygen saturations, who was extensively investigated before the correct diagnosis became apparent. Initial haemoglobin electrophoresis was normal, but subsequently abnormal on repeat testing. With further screening, a number of affected family members have since been identified.     

Peripheral circulation in the newborn: Interaction of peripheral blood flow,blood pressure,blood volume,and blood viscosity

Peripheral blood flow and systolic blood pressure (strain-gauge plethysmograph), blood volume (Evans blue) and whole blood viscosity (cone-plate viscometer) have been measured in 66 premature and full-term infants 6 to 144h of age. Blood flow and blood volume were moderately decreased in the infants with respiratory distress. Highly significant (P<0.001) correlations were found betwen blood flow and blood volume (r=0.77), blood pressure and blood volume (r=0.50), peripheral resistance and blood volume (r=-0.44), blood flow and blood pressure (r=0.50), blood flow and peripheral resistance (r=-0.67), peripheral resistance and blood viscosity (r=0.45), and blood viscosity and haematocrit (r=0.86). There was no correlation between peripheral blood flow and blood viscosity. However, at given blood volume, peripheral blood flow decreased with increasing blood viscosity. These results indicate that in newborn infants peripheral blood flow, blood pressure and peripheral resistance are influenced by blood volume, but also depend on blood viscosity.Supported by Deutsche Forschungsgemeinschaft (SFB 147)     

Short-term effects of blood transfusion on blood volume and resting peripheral blood flow in preterm infants

The effects of blood transfusion on cardiac output and blood pressure are variable, but resting peripheral blood flow (RPBF) may be a sensitive indicator of changes in blood volume. The purpose of this investigation was to study the effects of red cell transfusion on blood volume (Evans blue), blood pressure, RPBF in the leg (strain-gauge plethysmography) and blood viscosity (cone-plate viscometer) in preterm infants during the first week after birth. Fourteen infants with mean ± SD birth weight of 1658 ± 429 g, gestational age 33 ± 3 weeks and postnatal age 64 ± 40 h received 18 ±4 ml/kg of packed red cells (red cells 11±2 ml/kg, plasma 7± 1 ml/kg) because their hematocrit was less than 0.45 l/l. Mean blood volume before transfusion was 88±15 ml/kg. The increase in blood volume (9 ±4 ml/kg) measured 4 to 6 h after transfusion was smaller than the transfused volume (18 ± 4 ml/kg), due to a shift of plasma to the extravascular space. The plasma shift increased with increasing pretransfusion blood volume ( r = 0.70; p = 0.007). Red cell transfusion caused an increase in RPBF by 25% ( p <0.01), whereas systolic blood pressure (BP) increased by only 12%. Peripheral resistance (R = BP/RPBF) decreased by 9% (p<0.01). Blood viscosity (±) increased by 21'% ( p <0.001) and vascular hindrance (R/±) decreased by 24% ( p < 0.001), indicating vasodilatation of limb arteries. The increase in RPBF and the decrease in hindrance were particularly pronounced in infants with high pretransfusion blood volume. We conclude that the increase in blood volume after transfusion is not proportional to the transfused volume and that RPBF increases more than systolic blood pressure with increasing blood volume. The increase in RPBF can be explained by vasodilatation of limb arteries and by increased blood pressure.     

Autologous blood transfusions

Due to enormous risks of transfusion-transmitted diseases in allogenic blood transfusions, including dreaded AIDS, there has been constant endeavour to look for a safer alternative. Autologous transfusion which is transfusion of blood/component donated by intended recipient, has proved to be a safe and viable alternative. Initially tried in 1874 in the form of blood salvage, the process has become popular since 1971 with better PVC containers and storage facilities. Due to ignorance and lack of interest the procedure in still unpopular in India. It is very useful for preventing complications of allogenic transfusion and in rare blood group or patients for whom it is difficult to find compatible blood. Since 1980s the procedure is being widely used. Maximally used category is preoperative donation. Strict protocols regarding selection, storage and labelling are essential. There has been tenfold increase in the preoperative autologous donations in many centres. Isovolemic hemodilution and blood salvage are also being used. The procedure has also been used for preteenage and paediatric ages successfully. 1 to 5 units can be collected from single donor. Now the popularity of the procedure has increased due to awareness and interest.     

Comparison of blood gas values in arterial and venous blood

Objective : To compare pH and PCO₂ values of simultaneously obtained arterial, arterialized capillary, and venous blood samples and also to compare oxygen saturation (ASaO₂) measured in arterial blood and oxygen saturation by pulse oximetry (PSaO₂).Methods: Prospective study was done in the children admitted in the Pediatric Intensive Care Unit of Christian Medical College Hospital Vellore, requiring critical care. All the three blood gas samples (arterial, capillary and venous) were taken simultaneously and analyzed. Oxygen saturation by pulse oximetry was also recorded.Results: 50 children aged 14 days to 12 years were included in the study. Arterial and capillary pH values were highly correlated (r²=0.9024, p < 0.0001). Out of 16 children with arterial acidosis 9(56%) were identified by capillary blood gas. Arterial and venous pH values also showed good correlation (r²=0.8449, p eric 0.0001). The PCO₂ values of arterial and capillary blood gases were found to be highly correlated (r²=0.9534, p < 0.0001). The capillary blood gas accurately reflected the arterial PCO₂ in 41 (82%) patients. Arterial and venous blood gas PCO₂ values had less correlation (r²=0.5917, p=0.011). The arterial oxygen saturation (ASaO₂) and oxygen saturation by pulse oximetry (PSaO₂) were correlated moderately (r²=0.7241, p eric 0.0001).Conclusion: Even though arterial blood gas analysis is the gold standard, and when an arterial blood gas sample cannot be obtained, a combination of arterialized capillary blood gas and pulse oximetry can be effectively used in acutely ill children of all ages. Venous samples have a good correlation with arterial samples for pH but are not useful for monitoring blood gas status in acutely ill children.