Cases reported "Hyperoxia"

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1/4. Hyperoxic myopia in a closed-circuit mixed-gas scuba diver.

    A myopic shift occurred in a closed-circuit mixed-gas scuba diver using a 1.3 atm abs constant partial pressure of oxygen in a nitrogen-oxygen mix. This change was noticed after approximately 18 days of diving with a mean dive time of 4.04 h each day. The observed myopic shift was due to hyperoxic myopia, one sign of lenticular oxygen toxicity, and resolved over a 1 mo. period after diving was completed. On a subsequent drive trip, a myopic shift was found in both the index diver as well as two other divers breathing the same gasmix on similar profiles. diving communities should be aware of the risk of both lenticular and pulmonary oxygen toxicity when conducting intensive diving at oxygen partial pressures in the 1.3-1.6 atm abs range. ( info)

2/4. Increased inspired oxygen concentration as a factor in improved brain tissue oxygenation and tissue lactate levels after severe human head injury.

    OBJECT: Early impairment of cerebral blood flow in patients with severe head injury correlates with poor brain tissue O2 delivery and may be an important cause of ischemic brain damage. The purpose of this study was to measure cerebral tissue PO2, lactate, and glucose in patients after severe head injury to determine the effect of increased tissue O2 achieved by increasing the fraction of inspired oxygen (FiO2). methods: In addition to standard monitoring of intracranial pressure and cerebral perfusion pressure, the authors continuously measured brain tissue PO2, PCO2, pH, and temperature in 22 patients with severe head injury. microdialysis was performed to analyze lactate and glucose levels. In one cohort of 12 patients, the PaO2 was increased to 441 /-88 mm Hg over a period of 6 hours by raising the FiO2 from 35 /-5% to 100% in two stages. The results were analyzed and compared with the findings in a control cohort of 12 patients who received standard respiratory therapy (mean PaO2 136.4 /-22.1 mm Hg). The mean brain PO2 levels increased in the O2-treated patients up to 359 /-39% of the baseline level during the 6-hour FiO2 enhancement period, whereas the mean dialysate lactate levels decreased by 40% (p < 0.05). During this O2 enhancement period, glucose levels in brain tissue demonstrated a heterogeneous course. None of the monitored parameters in the control cohort showed significant variations during the entire observation period. CONCLUSIONS: Markedly elevated lactate levels in brain tissue are common after severe head injury. Increasing PaO2 to higher levels than necessary to saturate hemoglobin, as performed in the O2-treated cohort, appears to improve the O2 supply in brain tissue. During the early period after severe head injury, increased lactate levels in brain tissue were reduced by increasing FiO2. This may imply a shift to aerobic metabolism. ( info)

3/4. One day old infant with acyanotic congenital heart disease: critical aortic stenosis.

    Congenital aortic stenosis accounts for about 5% of cardiac malformations recognized in childhood. It belongs to the category of acyanotic congenital heart disease. These lesions produce a load on the heart because of left ventricular outflow tract obstruction. Severe aortic stenosis in the newborn period (critical aortic stenosis) presents with signs of left sided heart failure (pulmonary edema, poor perfusion), right sided heart failure (hepatomegaly, peripheral edema) and may progress rapidly to total circulatory collapse. We present a case of an infant with critical aortic stenosis presenting with cyanosis, who was entirely dependent on ductal patency for systemic output. When oxygen was given, the ductus started to close, with a worsening of the left sided output and subsequent acidosis. With the right to left shunt across the ductus, the baby was cyanotic and dependent on prostaglandin to keep the ductus open. There was minimal flow across the aortic valve because of the stenosis and extremely poor left ventricular function prior to surgery. After relief of the aortic valvular obstruction, there was finally good antegrade flow across the aortic valve, terminating cyanosis. ( info)

4/4. blood gases, electrolytes and metabolic monitoring in children with acute failure of vital functions.

    The priority of direct monitoring of blood gases in Paediatric intensive care units (PICU) increased substantially after introduction of the Deep Picture method and oxygen Status Algorithm (OSA) (1) into medical practice. We used the advantages of these methods as a prerequisite for a more detailed and deeper analysis of the blood oxygen profile (2, 3). The aims of the present paper were: 1. To illustrate the applicability of the capacity coefficients beta 1.0, beta 2.3, beta 5-4 of the transported oxygen and the "Useful Ratio" (UR) index of the haemoglobin oxygen, previously described by us, and the benefit derived from differentiation of the states of hyperoxia, normoxia and hypoxia; hyperoxaemia, normoxaemia and hypoxaemia on the blood oxygen Binding Curve (BOBC) in critically ill newborns, infants and children. 2. To expand the diagnostic capacity of the blood Gas Map (BGM) used with the OSA in children and to supplement the arterial oxygen diagnostics with new indices that reflect the relationship between oxygen uptake and oxygen transported in the body. 3. To share our experience in PICU related to the acid-base-electrolytes relationship and to the possibility of assessing the reno-hepatic regulation according to the changes of the acid-base status in critically ill children. ( info)

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