3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Lactate accumulation during exercise - the influence of body fluid shifts.(1999-06-25) Castleman, Barbara AnnDuring graded exercise, an intensity is reached where a subjects ability to remove lactate lags behind the rate of lactace production. The influence of body fluid shifts, during exercise of increasing intensity, on the pattern of the blood lactate response was studied. The maximal oxygen uptake (V02 max) was measured using a treadmill, on eleven subjects. Subsequently, lactate accumulation in venous blood was measured, in triplicate, up to an oxygen consumption greater than 90% V02max. During all exercise, oxygen consumption was measured using an online system. In addition, the blood samples at each workload were used to determine haematocrit (Hct) and haemoglobin (Hb) levels. The Hct and Hb values were used to calculate lactate accumulation (corrected for body fluid shifts) as opposed to the absolute or total lactate levels. The correction for body fluid shifts was done using two techniques. The one using haematocrit only and the other using both haematocrit and haemoglobin. The total and accumulated lactate levels were related to %V02max using two different models. Firstly, a lactate threshold (LT) was determined using the classic lactate turning point (LTP) concept, (ie. two straight lines fitted to the data points) . These Tines iii were computer generated. The intercept of the two lines (LT) was compared for total lactate against accumulated lactate (calculated using Hct alone and secondly Hct in combination with Hb. In the latter cases, both the LT intercepts were shifted slightly to the right (ie. to a higher % of V02max) . The average difference in LT when adjusting with Hb and Hct was 0,519 of %V02max (0,72% change) and when adjusting with Hct only was 1,17 of %V02 max (1,65% change). Secondly, an exponential curve was fitted by regression to the data (r=0.989+/-0.018). A substantial shift in the curve, both down and to the right, was obtained when adjusting total lactate to accumulated lactate. The %V02 max at a lactate concentration of 4 mmol/I was used to define the position of the curve. The difference when using Hct alone to calculate accumulated lactate corrected for fluid shift was - 9,20% of V02max (p<0.05), and when using Hb and Hct in combination, -8,71% of V02max (p<0,05) . It is concluded that expressing the lactate curve as an accumulated curve (corrected for body fluid shifts), rather than in absolute terms, significantly alters the construction of the curve during the exercise protocol used in this study. This is especially relevant when using the exponential model,Item The effect of preoperative apple juice on the prevalence of hypoglycaemia in paediatric patients(2013-01-24) Lee, Clover-AnnBackground: Children have historically been fasted for prolonged periods preoperatively to reduce the volume and acidity of their gastric contents and thus the risk of regurgitation and pulmonary aspiration. Evidence shows that this risk is not increased by following the current recommended fasting guidelines, and that prolonged fasting may be detrimental to children, who may present with hunger, thirst, depleted intravascular volume, metabolic acidosis and hypoglycaemia. A recent study at Charlotte Maxeke Johannesburg Academic Hospital showed a 18.5% prevalence of biochemical hypoglycaemia, defined as a blood glucose concentration of less than 3.5 mmol/l, in children from one to five years of age presenting for elective surgery. Aims: The aims of this study were to document the prevalence of biochemical hypoglycaemia in children from the ages of one to five years who were given apple juice to drink at least two hours preoperatively, and to compare these results to a historical control group. Methods: A prospective, contextual comparative study design was used. Approval was obtained from the University of the Witwatersrandʼs Human Ethics Committee and other relevant authorities. The groups were matched for age and weight. Consent was obtained from the guardians of all children who met the inclusion criteria before being enrolled in the study. A standard 200 ml carton of commercially available apple juice was offered to each participant. The volume and time of the juice consumed was documented, along with relevant demographic data. Inhalational induction of anaesthesia proceeded a minimum of two hours later, and a venous glucose concentration was measured. Results: The prevalence of biochemical hypoglycaemia was statistically significantly reduced in the intervention group (p = 0.0163), eliminating the effect of prolonged preoperative fasting. Conclusion: The consumption of clear apple juice on the morning of surgery is a safe, inexpensive, effective way to reduce the prevalence of hypoglycaemia in children presenting for elective surgery.