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Multiple carboxylase deficiency/holocarboxylase synthetase deficiency
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
The metabolic hallmark of this disease is the excretion of 3-methylcrotonylglycine and 3-hydroxyisovaleric acid along with elevated amounts of lactic acid in the blood and urine. Thus, the first clinical chemical clue to the disease may be the documentation of lactic acidemia. Organic acid analysis at the time of acute acidosis also reveals methylcitric and 3-hydroxypropionic acids. The organic acidemia may be quite variable, particularly if first studied after intensive therapy with parenteral fluid and electrolytes and resolution of the acidosis. The excretion of 3-hydroxyisovaleric acid is virtually always greater than that of 3-methylcrotonylglycine [11, 20, 26]; but occasionally, the proportion of these values was reversed [1]. The excretion of 3-hydroxyisovaleric acid may be as high as 200 times that of normal [2]. The lactic aciduria may be enormous. These patients may also excrete tiglylglycine in the urine [11].
Brain death and ethical issues: Death by neurological criteria
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Essentials of Geriatric Neuroanesthesia, 2019
Brittany Bolduc, David M. Greer
After confirming the presence of irreversible coma and absent brainstem reflexes, the provider can move on to apnea testing. Apnea is defined as the absence of respiratory drive despite CO2 challenge. Acidemia from rising pCO2 provides the stimulus for an intact medulla to breathe. Thus, apnea testing requires a rise in CO2 while preserving oxygenation. Prerequisites for apnea testing include normotension (systolic blood pressure [SBP] >100 mmHg), normothermia, euvolemia, eucapnia (PaCO2 40–45 mmHg), absence of hypoxia, and no prior evidence of CO2 retention. In some patients, the apnea test is not safe or reliable, such as those with underlying acute or chronic pulmonary disease (18). In those cases, ancillary testing (discussed later) will be necessary. In those who meet criteria, patients should be pre-oxygenated with 100% oxygen to a PaO2 >200 mmHg. Ventilator frequency should be reduced to 10 breaths per minute. Positive end-expiratory pressure (PEEP) should be reduced to 5 cm H2O. Patient must remain clinically stable and maintain oxygen saturation >95% at these minimal ventilator settings to proceed with apnea testing (4). Desaturation or hemodynamic instability suggests that apnea testing may not be safe and should be performed with great caution, if at all.
SBA Answers and Explanations
Published in Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury, SBAs for the MRCS Part A, 2018
Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury
Metabolic acidosis occurs when the body produces excessive quantities of acid or when the kidneys fail to remove enough acid from the body. If unchecked, metabolic acidosis leads to acidaemia, (pH less than 7.35) due to increased production of hydrogen ions by the body or the inability of the body to form bicarbonate (HCO3−) in the kidney.
Estimation of the risk of local and systemic effects in infants after ingestion of low-concentrated weak acids from descaling products
Published in Clinical Toxicology, 2022
Arjen Koppen, Claudine C. Hunault, Regina G. D. M. van Kleef, Agnes G. van Velzen, Remco H. S. Westerink, Irma de Vries, Dylan W. de Lange
Moreover, it is difficult to predict the occurrence of systemic effects after such exposures. In case of a functional intestinal barrier, the rate of acid absorption, metabolism and excretion determines the acid load. At a steady state, blood pH is tightly regulated and buffered, since protein function is strongly dependent on pH. Mechanisms for pH auto-regulation include the carbonic acid–bicarbonate buffer system, renal bicarbonate homeostasis, renal excretion of ammonium ions, respiratory control of the partial pressure of carbon dioxide and buffering by bone [6,7]. Systemic effects may occur when acids enter the blood circulation after ingestion of large amounts. Damage to the gastrointestinal barrier promotes the absorption of larger amounts of acids. In some cases, the resulting acidemia (lowering of blood pH) cannot be corrected sufficiently and symptoms like hemolysis, thrombocytopenia, clotting disorders, changes in respiratory rate, Kussmaul respiration, kidney disorders, nausea and vomiting can be observed [8].
Approach to the patient presenting with metabolic acidosis
Published in Acta Clinica Belgica, 2019
Jill Vanmassenhove, Norbert Lameire
There is a difference between acidosis and acidemia. Acidemia refers to the abnormal laboratory value, while acidosis refers to the process causing the abnormal value. In other words acidemia refers to a low pH or a high concentration of free H+ in plasma. Acidosis is a process that adds H+ to or removes HCO3- from the body. A patient may have a significant acid-base disorder even if the pH is normal. Therefore, even if the pH is normal, one should verify that the partial pressure of carbon dioxide (pCO2), bicarbonate level, and anion gap (see below) are normal. If they are not, the patient may have a mixed acid-base disorder such as respiratory acidosis superimposed on metabolic acidosis. Alternatively, patients can have acidosis with a near normal HCO3- concentration if the ECF (extracellular volume) is very contracted. In the latter case there is a combination of metabolic acidosis due to a decrease in bicarbonate content, and a chloride depletion metabolic alkalosis (previously erroneously called ‘contraction’ metabolic alkalosis). A normal plasma H+ concentration implies that there is either no acid base disorder or more than one. If bicarbonate and pCO2 levels change in the same direction, there will be no change in pH (pH = 6.1 + log HCO3−/pCO2) and one has to consider a mixed acid base disorder [1].
Inhibition of sodium-glucose cotransporter 2 to slow the progression of chronic kidney disease
Published in Acta Clinica Belgica, 2022
Fabie Oguz, Nathalie Demoulin, Jean Paul Thissen, Michel Jadoul, Johann Morelle
A relatively rare but severe adverse effect is euglycemic ketoacidosis. Ketoacidosis related to SGLT2 inhibitors results from the decreased activity of the sodium/potassium-ATPase in the proximal tubule and from restoration of fatty acid oxidation, causing an indirect loss of sodium bicarbonate in the urine and metabolic acidosis in conditions of increased ketogenesis [57]. SGLT2 inhibitors also contribute to decrease insulinemia and to increase glucagon levels, thereby stimulating lipolysis. As a result, metabolism shifts toward fatty acids oxidation and ketoacids production, as observed during fasting. Patients with unrecognized type 1 diabetes, long-standing type 2 diabetes, or latent autoimmune diabetes of the adult, are particularly at risk. Ketoacidosis is usually triggered by a precipitating factor, such as reductions in insulin dose or increased insulin demand, infections, volume depletion, low carbohydrate intake, and excessive alcohol use. Diagnosis is challenging as glycemia is usually normal or only mildly elevated, and symptoms are non-specific, including malaise, nausea, anorexia or abdominal pain. Prevention is important, and patients should be advised to maintain appropriate fluid intake; ensure adequate carbohydrate intake and avoid low-carbohydrate diets; avoid skipping insulin and skipping meals; discontinue SGLT2 inhibitors and monitor for presence of urinary ketones in situations of acute illness, vomiting, diarrhea, inability to eat or drink, and before an elective surgical or invasive procedure [57]. Treatment relies on drug discontinuation, restoration of extracellular fluid volume, and insulin supplementation; alkali therapy might be useful in patients with CKD and in those with severe acidemia.