Context.-Although concern over the risks of red blood cell transfusion has resulted in several practice guidelines for transfusion, lack of data regarding the physiological effects of anemia in humans has caused uncertainty regarding the blood hemoglobin (Hb) concentration requiring treatment.Objective.-To test the hypothesis that acute isovolemic reduction of blood Hb concentration to 50 g/L in healthy resting humans would produce inadequate cardiovascular compensation and result in tissue hypoxia secondary to inadequate oxygen transport.Design.-Before and after interventional study.Setting.-Academic tertiary care medical center.Participants.-Conscious healthy patients (n=11) prior to anesthesia and surgery and volunteers not undergoing surgery (n=21).Interventions.-Aliquots of blood (450-900 mL) were removed to reduce blood Hb concentration from 131 (2) g/L to 50 (1) g/L [mean (SE)]. Isovolemia was maintained with 5% human albumin and/or autologous plasma. Cardiovascular parameters, arterial and mixed venous oxygen content, oxyhemoglobin saturation, and arterial blood lactate were measured before and after removal of each aliquot of blood. Electrocardiogram and, in a subset, Holter monitor were monitored continuously.Main Outcome Measures.-"Critical" oxygen delivery (TO 2 ) as assessed by oxygen consumption (V O 2 ), plasma lactate concentration, and ST changes on electrocardiogram.Results.-Acute, isovolemic reduction of Hb concentration decreased systemic vascular resistance and TO 2 and increased heart rate, stroke volume, and cardiac index (each PϽ.001). We did not find evidence of inadequate oxygenation: V O 2 increased slightly from a mean (SD) of 3.07 (0.44) mL of oxygen per kilogram per minute (mL O 2 •kg −1 •min −1 ) to 3.42 (0.54) mL O 2 •kg −1 •min −1 (PϽ.001) and plasma lactate concentration did not change (0.81 [0.11] mmol/L to 0.62 [0.19] mmol/L; P=.09). Two subjects developed significant ST changes on Holter monitor: one apparently related to body position or activity, the other to an increase in heart rate (at an Hb concentration of 46-53 g/L); both occurred in young women and resolved without sequelae.Conclusions.-Acute isovolemic reduction of blood Hb concentration to 50 g/L in conscious healthy resting humans does not produce evidence of inadequate systemic TO 2 , as assessed by lack of change of V O 2 and plasma lactate concentration. Analysis of Holter readings suggests that at this Hb concentration in this resting healthy population, myocardial ischemia would occur infrequently.

A decrease in DO2 to 7.3+/-1.4 ml O2 x kg(-1) min(-1) in resting, healthy, conscious humans does not produce evidence of inadequate systemic oxygenation. The critical DO2 in healthy, resting, conscious humans appears to be less than this value.

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With acute reduction of hemoglobin concentration to 5 g/dl, ECG ST-segment changes developed in 3 of 55 healthy conscious adults and were suggestive of, but not conclusive for, myocardial ischemia. The higher heart rates that developed during hemodilution may have contributed to the development of an imbalance between myocardial supply and demand resulting in ECG evidence of myocardial ischemia. However, these ECG changes appear to be benign because they were reversible and not accompanied by symptoms.

BackgroundType 1 Diabetes Mellitus is a rapidly growing problem in Tanzania. Children and adolescents with type 1 diabetes have previously been found to have poor glycaemic control and high prevalence of complications. Strict glycaemic control reduces the incidence and progression of chronic complications. The aim of this study was to identify the factors associated with glycaemic control among children and adolescents.MethodsA cross sectional study was done at the diabetes clinic for children and adolescents. Data on socioeconomic, demographic and diabetes specific variables including adherence, diabetes knowledge, caregivers knowledge and their involvement in the care of the child was obtained. Glycaemic control was assessed by measuring glycosylated hemoglobin. (HbA1C). Linear regression analysis was done to determine factors associated with glycaemic controlResultsSeventy-five participants were recruited into the study (51 % males). The mean HbA1c was 11.1 ± 2.1 %. Children aged <10 years were found to have a significantly better glycaemic control (9.8 %) as compared to 10–14 year olds (11.5 %) and >14 year olds (11.4 %) (P value = 0.022). Sixty-eight percent of patients had good adherence to insulin while adherence to blood glucose monitoring regimen was 48 % and to diet control was 28 %.Younger age, having the mother as the primary caregiver, better caregiver knowledge of diabetes, better adherence to blood glucose monitoring regimen and diabetes duration of less than 1 year were associated with better glycaemic control.In multivariate analysis, age, adherence to blood glucose monitoring regimen and the mother as the primary caregiver were found to independently predict glycaemic control (R2 = 0.332, p value = 0.00).ConclusionsChildren and adolescents with type 1 diabetes in Dar es Salaam have poor glycaemic control. In order to improve metabolic control, adherence to blood glucose monitoring should be encouraged and caregivers encouraged to participate in care of their children especially the adolescents.