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Query: UMLS:C0085383 (hypocapnia)
 1,697 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Infusion of sodium lactate has been shown by a number of investigators to induce panic in patients with panic disorder, but the pathophysiology underlying this phenomenon is unknown. One theory to explain lactate's anxiety-producing effects involves its ability to induce alkalosis because of metabolic conversion to bicarbonate. To test this hypothesis, we administered both sodium lactate and sodium bicarbonate infusions in counterbalanced order to patients with panic disorder. Thirteen of 22 subjects panicked in response to lactate and nine of 20 subjects panicked in response to bicarbonate. Although the rate of panic between the two infusion responses was not significantly different, several aspects of response to the two infusions indicated that lactate may be a more potent producer of anxiety than bicarbonate. An unexpected finding was that bicarbonate panickers had a reduction in arterial carbon dioxide pressure during the infusion, while bicarbonate nonpanickers had an increase in arterial carbon dioxide pressure during the infusion. Induction of hyperventilation and subsequent hypocapnia appears to be a common denominator between lactate- and bicarbonate-induced panic.
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PMID:A comparison of sodium bicarbonate and sodium lactate infusion in the induction of panic attacks. 253 38

In this study, we tested the hypothesis that hypoxic pulmonary vasoconstriction may be enhanced in systemic hypertension. The hypothesis took origin from the following two considerations: alveolar hypoxia constricts the pulmonary vessels by enhancing the Ca2+ penetration across sarcolemma of the smooth muscle cells and systemic high blood pressure is associated with an elevation of tone and reactivity of the lung vessels, which seems to depend on an excessive cytosol free Ca2+ concentration due to alterations in sodium handling and in the Na+-Ca2+ exchange system. These considerations suggest the possibility that the disorders in the biochemistry of smooth muscle contraction in hypertension facilitate the rise of cytosol Ca2+ concentration during alveolar hypoxia, thus resulting in a potentiation of the vasoconstrictor properties of this stimulus. In 43 hypertensive and 17 normotensive men, pulmonary arteriolar resistance has been evaluated during air respiration and after 15 minutes of breathing 17%, 15%, and 12% oxygen in nitrogen. Curves relating changes in pulmonary arteriolar resistance to oxygen breathing contents had similar configuration in the two populations but in hypertension were steeper and significantly shifted to the left, reflecting a lower threshold and an enhanced reactivity. This pattern was not related to differences in severity of the hypoxic stimulus, plasma catecholamine concentration, or hypocapnia and respiratory alkalosis induced by hypoxia and probably was not mediated through alpha-receptor activation. Calcium channel blockade with nifedipine was able to almost abolish both the normotensive and the hypertensive pulmonary vasoconstriction reaction. These findings support the hypothesis that hypoxic pulmonary vasoconstriction may be enhanced in systemic hypertension.
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PMID:Enhanced hypoxic pulmonary vasoconstriction in hypertension. 256 42

A 34-year-old woman with a recent history of a influenza-like illness and signs of bronchopneumonia presented with many of the features of acute epiglottitis, a condition which still carries a high mortality in adults. Urgent laryngoscopy and bronchoscopy under inhalational anaesthesia were negative. The results of arterial blood gases, taken when stridor was at its worst, revealed marked hypocapnia and respiratory alkalosis. We conclude that the resultant acute reduction of serum ionised calcium produced stridor as a result of tetany of the vocal cords. Similar cases from the literature and the role of emotional factors in the aetiology are discussed.
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PMID:Stridor in an adult. An unusual presentation of functional origin. 265 May 74

Experiments on dogs have shown that hyperthermia intensifies respiration, increases oxygen consumption, induces pronounced discrepancy of the alveolar ventilation to carbon dioxide elimination, severe hypocapnia and decompensated respiratory alkalosis.
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PMID:[External respiration, gas exchange and blood acid-base status in dogs with hyperthermia]. 271 67

1. In systemic hypertension the pulmonary vessels show an excessive tone at rest and hyper-react to adrenoceptor stimulation. Alterations in Ca2+ handling by the vascular smooth muscle cells seem to underlie these disorders. Alveolar hypoxia also constricts pulmonary arteries, increasing the intracellular Ca2+ availability for smooth muscle contraction. This suggests the hypothesis that hypoxic pulmonary vasoconstriction depends on similar biochemical disorders, and that the response to the hypoxic stimulus may be emphasized in high blood pressure. 2. In 21 hypertensive and 10 normotensive men, pulmonary arterial pressure and arteriolar resistance have been evaluated during air respiration and after 15 min of breathing 17, 15 and 12% oxygen in nitrogen. Curves relating changes in pulmonary arterial pressure and arteriolar resistance to the oxygen content of inspired gas had a similar configuration in the two populations, but in hypertension were steeper and significantly shifted to the left of those in normotension, reflecting a lower threshold and an enhanced vasoconstrictor reactivity. 3. This pattern was not related to differences in severity of the hypoxic stimulus, degree of hypocapnia and respiratory alkalosis induced by hypoxia, and plasma catecholamines. 4. The association of high blood pressure with enhanced pulmonary vasoreactivity to alveolar hypoxia could have clinical implications in patients who are chronically hypoxic and have systemic hypertension.
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PMID:Enhancement of the pulmonary vasoconstriction reaction to alveolar hypoxia in systemic high blood pressure. 273 78

The similar localization of intracranial calcification in hypoparathyroidism and in Fahr disease without parathyroid gland disorder suggests that in these two disorders the pathomechanism of calcium phosphate deposition in the brain may be similar. It may be that in Fahr disease some factors, such as chronic respiratory alkalosis, could lead to hypoparathyroidism-like changes in the brain tissue. Abolition of the phosphaturic response to parathormone (PTH) was recently demonstrated in acute experimental hypocapnia. In three adult patients with Fahr disease, a tendency towards compensatory respiratory alkalosis and arterial hypocapnia was found. The parathormone test revealed a marked decrease in phosphaturia response to PTH, but normal cAMP response. In one patient, the parathormone test was repeated during propranolol administration and showed a considerable improvement in the phosphaturic response to parathormone. It is postulated that chronic hyperventilation and hypocapnia as well as phosphaturic resistance to PTH, intracellular increase of phosphate concentration and development of hypoparathyroidism-like intracranial calcification in patients with Fahr disease could all be caused by disturbance of adrenergic receptors and their relationship to PTH receptors.
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PMID:Abolished phosphaturic response to parathormone in adult patients with Fahr disease and its restoration after propranolol administration. 283 40

1. The effect of varying artificial respiratory volume (at a fixed rate of 54 min-1) on cardiac output, its distribution and tissue blood flows were determined with tracer microspheres in control pithed rats or during pressor responses to either the alpha 1-adrenoceptor agonist phenylephrine or the alpha 2-agonist xylazine. Phenylephrine was investigated in the presence of propranolol (3 mg kg-1). The rats were pithed under halothane anaesthesia. 2. A respiratory volume of 15 ml kg-1 produced modest hypercapnia (PaCO2 = 47 mmHg), hypoxia (PaO2 = 60 mmHg) and acidosis (pH = 7.35) relative to control animals respired at 20 ml kg-1 (PaCO2 = 32 mmHg; PaO2 = 77 mmHg; pH = 7.47). In rats respired at 15 ml kg-1, total peripheral resistance was lower, and cardiac output greater (due to increased stroke volume), than in the controls. Lowering respiratory volume reduced distribution of cardiac output to the kidneys, increased it to the large intestine and also increased blood flow through the gastrointestinal tract, skin and spleen. A respiratory volume of 30 ml kg-1 gave mild hypocapnia (PaCO2 = 19 mmHg), hyperoxia (PaO2 = 101 mmHg) and alkalosis (pH = 7.59) compared to 20 ml kg-1 but had no effect on cardiac output distribution or organ blood flow although heart rate was 29% greater at 30 ml kg-1. 3. Xylazine (500 micrograms bolus followed by 100 micrograms min-1 infusion) at all three respiratory volumes gave well-sustained mean pressor responses of 62-64 mmHg by increasing both total peripheral resistance and cardiac output (resulting from increased stroke volume). It increased the proportion of cardiac output passing to the liver, reduced that going to the spleen and gastrointestinal tract and increased cardiac, renal and hepatosplanchnic blood flows. 4. The secondary, relatively sustained, pressor effect of phenylephrine (5 micrograms bolus followed by 0.4 micrograms min-1 infusion, i.v.) varied at the 3 respiratory volumes with mean values from 32 to 53 mmHg. This response was due to both increased total peripheral resistance and cardiac output (resulting from greater stroke volumes and/or heart rates). Phenylephrine increased the proportion of cardiac output passing to the gastrointestinal tract, heart, kidneys and hepatosplanchnic bed and increased cardiac, hepatosplanchnic, renal and gastrointestinal blood flows. 5. Respiratory volume had no effect on the cardiovascular effects of xylazine. However, respiratory volume modified the effects of phenylephrine on heart rate and changed the relative contributions of stroke volume and heart rate to the increased cardiac output. It also influenced the effects of phenylephrine on cardiac output distribution to the liver, epididimides and hepatosplanchnic bed and on blood flow through skeletal muscle and the large intestine. 6. Changes in respiratory volume of air ventilated pithed rats thus influence cardiac output, its distribution and regional blood flows. Such changes can also differently influence the responses of various vascular beds to phenylephrine whilst having no effect on their responses to xylazine.
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PMID:Effect of artificial respiratory volume on the cardiovascular responses to an alpha 1- and an alpha 2-adrenoceptor agonist in the air-ventilated pithed rat. 289 57

Metabolic acidosis inhibits and alkalosis enhances ketoacid production in ketotic humans and animals. To compare these effects with those of superimposed respiratory acid-base disturbances, ketone output was evaluated in awake ketotic rats during metabolic (intravenous infusions of HCl or NaHCO3) or respiratory (hyper or hypocapnia) disorders. With decreases in blood pH of 0.1-0.2 units over 3 h, blood ketone concentrations significantly decreased an average of 1.9 mM (metabolic) and 1.1 mM (respiratory) and urinary ketone excretion rates significantly decreased by 1.3 mumol/min (metabolic). With increases in systemic pH, blood ketone concentrations and urinary ketone excretion rates were significantly increased. Changes in blood pH correlated with changes in urinary ketone excretion rates in both metabolic (r = 0.87) and respiratory (r = 0.67) acid-base disturbances. The alterations occurred promptly and were rapidly reversible. These findings indicate that modest changes in systemic pH from metabolic or respiratory acid-base disturbances modify net ketoacid production in ketotic rats, confirm pH control of endogenous acid output as an acid-base regulator, and show that systemic pH, not bicarbonate concentration, mediates the process.
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PMID:Ketoacid production in acute respiratory and metabolic acidosis and alkalosis in rats. 292 22

The sensation of disrupted sleep following ascent to high altitude is associated with frequent awakenings, which may reflect sleep disruption due to respiratory dysrhythmia consisting typically of monotonously repetitive periodic breathing. This seems to arise from the combined effects of hypocapnia, which leads to suppression of respiratory effort in NREM sleep, and hypoxia, which stimulates termination of apnea and hyperpnea with consequent hypocapnia, leading to perpetuation of periodicity. Sleep disruption and periodic breathing decrease with time at altitude but may also be considerably reduced by pretreatment with acetazolamide, which may act by correction of alkalosis or through some other mechanism. In long-term residents of high altitude less distinctive, undulating respiratory dysrhythmias are described with unstable and decreased arterial oxygenation.
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PMID:Sleep at high altitude. 293 58

Mechanically induced hyperventilation is used in the treatment of newborn infants with persistent pulmonary hypertension syndrome to induce respiratory alkalosis, which may attenuate their pulmonary vasoconstriction. Whether this treatment is effective because of the increase in arterial pH or the decrease in Paco2 was investigated in nine sedated, mechanically ventilated newborn lambs with hypoxia-induced pulmonary vasoconstriction. We found that respiratory alkalosis and metabolic alkalosis were equally effective in attenuating hypoxia-induced pulmonary vasoconstriction, but that hypocapnia (low Paco2 with a normal arterial pH) was ineffective. These results indicate that increased arterial pH, not decreased Paco2, attenuates hypoxia-induced pulmonary vasoconstriction in newborn lambs and possibly the pulmonary vasoconstriction in newborn infants with persistent pulmonary hypertension syndrome.
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PMID:Increased arterial pH, not decreased PaCO2, attenuates hypoxia-induced pulmonary vasoconstriction in newborn lambs. 308 Jul 25


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