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Clinical Aspects of Acid–Base Control
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Base excess or deficit is defined as the amount of acid or base required to titrate whole blood at 37°C and a of 40 mmHg (5.3 kPa) to a pH of 7.4. An increase in buffer base (>50 mmol/L) or base excess indicates an increase in buffering capacity, and this may be from a decrease in metabolic acids or an increase in buffers ( , Hb and proteins). A decreased buffer base or base deficit may result from excess metabolic acids or a decrease in buffer content.
Fetal Circulation
Published in Miriam Katz, Israel Meizner, Vaclav Insler, Fetal Well-Being, 2019
Miriam Katz, Israel Meizner, Vaclav Insler
Another way to measure the degree of metabolic changes, particularly in bicarbonate concentration, is the assessment of the base excess. Base excess is the amount of plasma bicarbonate which is available in order to buffer an excess of nonvolatile acids. If the base excess is lower than the input of organic (nonvolatile) acids, it will lead to a base deficit. The readings will be the same for both of them, the excess presented as a positive and deficit as negative value. In order to evaluate the acid-base status and to identify the cause responsible for the imbalance it is necessary to determine the following parameters: pH, pCO2, total CO2, base excess, and/or the base deficit.
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
In metabolic acidosis, there is a negative base excess. Bicarbonate is the main extracellular buffer, not intracellular. The main intracellular buffers are phosphate and proteins. Compensation in metabolic acidosis occurs through hyperventilation (an increase in alveolar ventilation) and blowing off of CO2. The mainstay of treatment is to treat the underlying cause (e.g., treatment of hypoxia, shock, hypovolaemia, sepsis). Bicarbonate infusions are used as a last resort since they shift the oxygen–haemoglobin dissociation curve to the left.
Compensatory metabolic and central respiratory drive mechanisms in ALS
Published in Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2021
Susana Pinto, Michael Swash, Mamede De Carvalho
The ALS patients studied presented with high P0.1 values at first observation (normative values at rest in the range of 0.5–1.5 cmH2O) (7), in compensation for weakness of respiratory muscles as determined by MIP and MEP. This compensation was maintained in G1 patients, retested 6 months later. Even though P0.1 values decreased significantly, they were still higher at retest (T1), and the ratio of P0.1/MIP was similar between observations. The decrease in MIP was accompanied by a significant decrease in MeanPhrenAmpl. In this group, bulbar onset was more common than in our general ALS population. In addition to this functional compensation by increased central respiratory drive, metabolic compensation for respiratory failure was also observed, since bicarbonate and PCO2 also increased. The importance of evaluating bicarbonate and base excess in addition to PCO2 and pH in ALS is recognized (8). These compensatory respiratory and metabolic mechanisms maintained blood pH levels within normal values in these patients.
Surgical technique of uretero-ileal anastomosis in patients with bilateral duplex ureters undergoing radical cystectomy and ileal conduit urinary diversion: initial experience
Published in Acta Chirurgica Belgica, 2021
Kavaric Petar, Albijanic Marko, Rebronja Almir, Vukovic Marko
Postoperatively, all patients were placed on the identical treatment pathway and follow-ups were scheduled every 3–4 months during the first year and semi-annualy in the second [9]. Ureteral stents were removed two weeks after surgery. Routine follow-up examinations included laboratory studies, urinary cytology, abdominal ultrasound and intravenous urography. Abdominal/pelvic computer tomography and chest radiography were performed annually or in suspected cases of local or distal tumor progression. Patients were examined for UIS, high-grade VUR, hydronephrosis and other peri-operative outcomes during the follow-up period [10]. Renal function was measured by serum creatinine and GFR, hydronephrosis was examined by abdominal ultrasound or computed tomography, and VUR was assessed by loopography [11]. The acidosis was monitored using the base excess that was estimated by venous blood gas analysis, every three months initially, followed by yearly, depending on the blood gas values.
Heterogeneity of predictors of nocturnal hypoventilation in amyotrophic lateral sclerosis
Published in Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2021
Grazia Crescimanno, Alessandra Sorano, Francesca Greco, Maria Canino, Alessia Abbate, Oreste Marrone
Medicare rules, based on American guidelines, request to rely on a forced vital capacity (FVC) <50% of the predicted value or maximum negative inspiratory pressures ≤60 cm H2O as a criterion to start NIV (6). Instead, the European consensus of experts (ESFN) recommends starting NIV when FVC falls below 80% of predicted if this decrease is associated with signs or symptoms suggestive of hypoventilation (7). Both these criteria are far from being perfect. In fact, NH is often already present when FVC falls below 50% of predicted (8), while symptoms of hypoventilation are not specific and are poorly sensitive, especially in the early stages of the disease. It was reported that nocturnal desaturations, detected by pulse oximetry, could be an useful index to start NIV (9), and that they were associated with worse diaphragm function and NH (10). Besides, it was shown that base excess (BE) had a high specificity as an indicator of NH in Duchenne muscular dystrophy (11). However, a later study found that both overnight oximetry and early morning blood gases had a low sensitivity for NH in ALS (12). The sniff nasal inspiratory pressure (SNIP) is less commonly used than other tests of respiratory muscle function, although it may be able to reveal respiratory muscle weakness earlier than FVC (13,14). Some studies found that SNIP is correlated to nocturnal hypoxia (15,16) and to diurnal hypercapnia (17–19), but its relationship with NH, as assessed by nocturnal capnography, has been considered only in a small group of ALS patients (17).