(1/136) Carbon monoxide poisoning treated with hyperbaric oxygen: metabolic acidosis as a predictor of treatment requirements.

A retrospective case note analysis was made of patients who received hyperbaric oxygen for carbon monoxide poisoning and were admitted to the Royal Naval Hospital Haslar between 1991 and 1995. Males predominated (38 v 10) as did cases of deliberate self poisoning (31 v 17). The most common presenting feature was unconsciousness, which is an indication for hyperbaric oxygen and therefore reflects referral patterns. If patients had not recovered completely after one hyperbaric exposure further treatments were given. The initial hydrogen ion concentration of those requiring more than one treatment was significantly higher than those who recovered after the first treatment. The initial carboxyhaemoglobin (COHb) concentration showed only a trend to being higher in the multiple treatment group. Although metabolic acidosis is well recognised, its relationship to treatment requirements has not been shown previously. Initial COHb does not always correlate well with severity of poisoning which relates to the mechanism of toxicity of carbon monoxide: binding of carbon monoxide to the intracellular oxygen carrying proteins (for example cytochromes) rather than solely to haemoglobin. These findings are consistent with this mechanism and suggests that initial acidosis is a better predictor of treatment requirements and severity than initial COHb.  (+info)

(2/136) Renal responses of trout to chronic respiratory and metabolic acidoses and metabolic alkalosis.

Exposure to hyperoxia (500-600 torr) or low pH (4.5) for 72 h or NaHCO(3) infusion for 48 h were used to create chronic respiratory (RA) or metabolic acidosis (MA) or metabolic alkalosis in freshwater rainbow trout. During alkalosis, urine pH increased, and [titratable acidity (TA) - HCO(-)(3)] and net H(+) excretion became negative (net base excretion) with unchanged NH(+)(4) efflux. During RA, urine pH did not change, but net H(+) excretion increased as a result of a modest rise in NH(+)(4) and substantial elevation in [TA - HCO(-)(3)] efflux accompanied by a large increase in inorganic phosphate excretion. However, during MA, urine pH fell, and net H(+) excretion was 3.3-fold greater than during RA, reflecting a similar increase in [TA - HCO(-)(3)] and a smaller elevation in phosphate but a sevenfold greater increase in NH(+)(4) efflux. In urine samples of the same pH, [TA - HCO(-)(3)] was greater during RA (reflecting phosphate secretion), and [NH(+)(4)] was greater during MA (reflecting renal ammoniagenesis). Renal activities of potential ammoniagenic enzymes (phosphate-dependent glutaminase, glutamate dehydrogenase, alpha-ketoglutarate dehydrogenase, alanine aminotransferase, phosphoenolpyruvate carboxykinase) and plasma levels of cortisol, phosphate, ammonia, and most amino acids (including glutamine and alanine) increased during MA but not during RA, when only alanine aminotransferase increased. The differential responses to RA vs. MA parallel those in mammals; in fish they may be keyed to activation of phosphate secretion by RA and cortisol mobilization by MA.  (+info)

(3/136) In vitro metabolic and respiratory acidosis selectively inhibit osteoblastic matrix gene expression.

Clinically, a decrease in blood pH may be due to either a reduction in bicarbonate concentration ([HCO(-)(3)], metabolic acidosis) or an increase in PCO(2) (respiratory acidosis). In mammals, metabolic acidosis induces a far greater increase in urine calcium excretion than respiratory acidosis. In cultured bone, metabolic acidosis induces a marked increase in calcium efflux and a decrease in osteoblastic collagen synthesis, whereas isohydric respiratory acidosis has little effect on either parameter. We have shown that metabolic acidosis prevents the normal developmental increase in the expression of RNA for matrix Gla protein and osteopontin in chronic cultures of primary murine calvarial bone cells (predominantly osteoblasts) but does not alter expression of osteonectin. To compare the effects of isohydric metabolic and respiratory acidosis on expression of these genes, bone cell cultures were incubated in medium at pH approximately 7.2 to model metabolic ([HCO(-)(3)], approximately 13 mM) or respiratory (PCO(2), approximately 80 mmHg) acidosis or at pH approximately 7.4 as a control. Cells were sampled at weeks 4, 5, and 6 to assess specific RNA content. At all time periods studied, both metabolic and respiratory acidosis inhibited the expression of RNA for matrix Gla protein and osteopontin to a similar extent, whereas there was no change in osteonectin expression. In contrast to the significant difference in the effects of metabolic and respiratory acidosis on bone calcium efflux and osteoblastic collagen synthesis, these two forms of acidosis have a similar effect on osteoblastic RNA expression of both matrix Gla protein and osteopontin. Thus, although several aspects of bone cell function are dependent on the type of acidosis, expression of these two matrix genes appears to be regulated by extracellular pH, independently of the type of acidosis.  (+info)

(4/136) Oxygen therapy during exacerbations of chronic obstructive pulmonary disease.

Venturi masks (VMs) and nasal prongs (NPs) are widely used to treat acute respiratory failure (ARF) in chronic obstructive pulmonary disease (COPD). In this study, these devices were compared in terms of their potentiality to worsen respiratory acidosis and their capacity to maintain adequate (> 90%) arterial oxygenation (Sa,O2) through time (approximately 24 h). In a randomized cross-over study, 18 consecutive COPD patients who required hospitalization because of ARF were studied. After determining baseline arterial blood gas levels (on room air), patients were randomized to receive oxygen therapy through a VM or NPs at the lowest possible inspiratory oxygen fraction that resulted in an initial Sa,O2 of > or = 90%. Arterial blood gas levels were measured again 30 min later (on O2), and Sa,O2 recorded using a computer during the subsequent approximately 24 h. Patients were then crossed-over to receive O2 therapy by means of the alternative device (NPs or VM), and the same measurements obtained again in the same order. It was observed that both the VM and NPs improved arterial oxygen tension (p<0.0001) to the same extent (p=NS), without any significant effect upon arterial carbon dioxide tension or pH. However, despite this adequate initial oxygenation, Sa,O2 was < 90% for 3.7+/-3.8 h using the VM and for 5.4+/-5.9 h using NPs (p<0.05). Regression analysis showed that the degree of arterial hypoxaemia (p<0.05) and arterial hypercapnia (p<0.05) present before starting O2 therapy and, particularly, the initial Sa,O2 achieved after initiation of O2 therapy (p<0.0001) enabled the time (in h) that patients would be poorly oxygenated (Sa,O2 < 90%) on follow-up to be predicted. These findings suggest that, in order to maintain an adequate (> 90%) level of arterial oxygenation in patients with chronic obstructive pulmonary disease and moderate acute respiratory failure: 1) the initial arterial oxygen saturation on oxygen should be maximized whenever possible by increasing the inspiratory oxygen fraction; 2) this strategy seems feasible because neither the VM nor NPs worsen respiratory acidosis significantly; and 3) the Venturi mask (better than nasal prongs) should be recommended.  (+info)

(5/136) Inspiratory pressure support prolongs exercise induced lactataemia in severe COPD.

BACKGROUND: A physiological benefit from pulmonary rehabilitation in chronic obstructive pulmonary disease (COPD) is more probable if exercise is performed above the lactate threshold. This study was undertaken to investigate whether it was possible to extend the lactataemia of exercise using non-invasive inspiratory pressure support (IPS). METHODS: Plasma lactate levels were measured in eight men with severe COPD who performed two treadmill walks at an identical constant work rate to a condition of severe dyspnoea; the second walk was supported by IPS. RESULTS: Mean plasma lactate levels before the free and IPS assisted walks were 1.65 mmol/l and 1. 53 mmol/l, respectively (p = NS). Lactate levels increased during both walks to 2.96 mmol/l and 2.42 mmol/l, respectively (p = 0.01 for each) but the duration of the IPS assisted walk was significantly greater than the free walk (13.6 minutes versus 5.5 minutes, p = 0.01). CONCLUSIONS: Patients with severe COPD can sustain exercise induced lactataemia for longer if assisted with IPS. This technique may prove to be a useful adjunct in pulmonary rehabilitation.  (+info)

(6/136) One year period prevalence study of respiratory acidosis in acute exacerbations of COPD: implications for the provision of non-invasive ventilation and oxygen administration.

BACKGROUND: Non-invasive ventilation (NIV) reduces mortality and intubation rates in patients with chronic obstructive pulmonary disease (COPD) admitted to hospital with respiratory acidosis. This study aimed to determine the prevalence of respiratory acidosis in patients admitted with COPD, to draw inferences about oxygen therapy, and to determine the need for NIV services for acute COPD in typical UK hospitals. METHODS: This one year prospective prevalence study identified patients with COPD aged 45-79 years inclusive who were admitted to Leeds General Infirmary, St James's University, and Killingbeck Hospitals, Leeds between 1 March 1997 and 28 February 1998. The prevalence of respiratory acidosis and the relationship with oxygenation are described. Other outcomes included intensive care use and in hospital mortality. From this data population prevalence estimates were determined for respiratory acidosis, from which the need for NIV in a typical district general hospital was modelled. RESULTS: 983 patients were admitted, 11 of whom required immediate intubation. 20% of the remaining 972 had a respiratory acidosis. Acidosis was associated with subsequent admission to the intensive care unit (ICU): pH<7.25, OR 6.10 (95% confidence interval (CI) 1.19 to 31.11); pH 7.25-7.30, OR 8.73 (95% CI 2.11 to 36.06). pH was inversely correlated with arterial oxygen tension (PaO(2)) in the 47% of patients who were hypercapnic, with a PaO(2) of >10 kPa being associated with acidosis in most hypercapnic patients. 80% remained acidotic after initial treatment, giving an age/sex specific prevalence for England and Wales of 75 (95% CI 61 to 90)/100 000/year for men aged 45-79 years and 57 (95% CI 46 to 69)/100 000/year for women. Modelling the need for NIV for all COPD patients indicates that a typical UK hospital will admit 90 patients per year with acidosis of which 72 will require NIV. CONCLUSIONS: In patients with acute COPD the PaO(2) should be maintained at 7.3-10 kPa (SaO(2) 85-92%) to avoid the dangers of hypoxia and acidosis. If all COPD patients with a respiratory acidosis (pH<7.35) after initial treatment are offered NIV, a typical UK hospital will treat 72 patients per year.  (+info)

(7/136) Cardiovascular responses to calcium administered intravenously to man during halothane anesthesia.

Calcium chloride (7 mg/kg) was administered intravenously to six healthy volunteers anesthetized with halothane. Cardiovascular changes were measured during constant ventilation and anesthetic depth under three conditions: 1) respiratory alkalosis, 2) normocarbia, and 3) respiratory acidosis. At each Paco2, calcium infusion significantly increased cardiac index, left ventricular minute work index, and stroke index. Heart rate, total peripheral resistance, and cardiac pre-ejection period decreased. No significant change in mean arterial blood pressure or central venous pressure followed calcium administration, and no arrhythmias occurred. It is concluded that calcium administration increases myocardial performance, presumably by increasing the availability of intracellular calcium ion for actomyosin interaction.  (+info)

(8/136) Fumonisin B(1) increases serum sphinganine concentration but does not alter serum sphingosine concentration or induce cardiovascular changes in milk-fed calves.

Fumonisin B(1) is the most toxic and commonly occurring form of a group of mycotoxins that alter sphingolipid biosynthesis and induce leukoencephalomalacia in horses and pulmonary edema in pigs. Purified fumonisin B(1) (1 mg/kg, iv, daily) increased serum sphinganine and sphingosine concentrations and decreased cardiovascular function in pigs within 5 days. We therefore examined whether the same dosage schedule of fumonisin B(1) produced a similar effect in calves. Ten milk-fed male Holstein calves were instrumented to obtain blood and cardiovascular measurements. Treated calves (n = 5) were administered purified fumonisin B(1) at 1 mg/kg, iv, daily for 7 days and controls (n = 5) were administered 10 ml 0.9% NaCl, iv, daily. Each calf was euthanized on day 7. In treated calves, serum sphinganine concentration increased from day 3 onward (day 7, 0.237 +/- 0.388 micromol/l; baseline, 0.010 +/- 0.007 micromol/l; mean +/- SD), whereas, serum sphingosine concentration was unchanged (day 7, 0.044 +/- 0.065 micromol/l; baseline, 0.021 +/- 0.025 micromol/l). Heart rate, cardiac output, stroke volume, mean arterial pressure, mean pulmonary artery pressure, pulmonary artery wedge pressure, central venous pressure, plasma volume, base-apex electrocardiogram, arterial Po(2), and systemic oxygen delivery were unchanged in treated and control calves. Fumonisin-treated calves developed metabolic acidosis (arterial blood pH, 7.27 +/- 0.11; base excess, -9.1 +/- 7.6 mEq/l), but all survived for 7 days. We conclude that calves are more resistant to fumonisin B(1) cardiovascular toxicity than pigs.  (+info)

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