Physiological changes occurring in pregnancy
William T. Blows in The Biological Basis of Clinical Observations, 2018
The maternal changes that occur in pregnancy are all adaptive to accommodate and sustain a developing child. Pregnancy is divided into three stages. The first trimester covers weeks 1 to 12, starting from the date of the last menstruation; the second trimester covers weeks 13 to 27; and the third trimester covers weeks 28 to birth. Cardiac output is fully back to pre-pregnant values by 14 days post-delivery in all women who have had no cardiovascular complications. Changes occur in the heart as well. It becomes slightly enlarged during pregnancy and provides a greater force of contraction. Serum bicarbonate also falls, and this leads to a mild respiratory alkalosis in normal pregnancy. Pregnant women may feel slightly breathless, usually during the third trimester, and this is considered normal. Renal changes in pregnancy include an increase in the glomerular filtration rate, sodium and water retention due to increased aldosterone, and the loss of some glucose in the filtrate.
Pulmonary Vascular Disease
G John Gibson in Clinical Tests of Respiratory Function, 2008
The most specific functional information in patients with suspected pulmonary embolism (PE) is obtained from isotope scans.With the wide availability of spiral computed tomography (CT) scanning, isotope scans are used less often than hitherto, but they still have a role in clinical investigation (see below). Simple spirometric volumes (FEV1, VC) are usually normal in uncomplicated pulmonary embolism, but they may be reduced if full inspiration is impeded by chest pain. Their main role is in differential diagnosis of acute breathlessness and in recognizing patients with coexisting airway obstruction (chronic obstructive pulmonary disease (COPD) or asthma). The characteristic pattern of arterial blood gases in acute pulmonary embolism is a reduction in both PaO2 and PaCO2 together with a respiratory alkalosis.
Practice Paper 1: Answers
J. Benton Pegna, Dominic Teichmann, Dominic Teichmann, Saran Shantikumar in Get Ahead! Surgery: 250 SBAs for Finals, 2015
D – Type I respiratory failure A simple interpretation of arterial blood gases is as follows. e pH value shows if the gas is acidotic ( 7.45). Next you need to nd out if the alkalosis or acidosis is due to a metabolic or respiratory cause – this is done by looking at the pCO2 and bicarbonate levels. ere are two things you need to bear in mind before continuing: (1) carbon dioxide is acidic and bicarbonate is alkaline; and (2) bicarbonate equates to ‘metabolic’ and pCO2 means ‘respiratory’. An alkalosis can be due to either a high bicarbonate (‘metabolic alkalosis’) or a low pCO2 (‘respiratory alkalosis’). Conversely, an acidosis can be caused by either a low bicarbonate (‘metabolic acidosis’) or a high pCO2 (‘respiratory acidosis’).
Acid-base Status in Liver Cirrhosis. Disturbances in Stable, Terminal and Porta-caval Shunted Patients
Published in Scandinavian Journal of Gastroenterology, 1976
Prytz, H. & Thomsen. Å. C. Acid-base status in liver cirrhosis. Disturbances in stable, terminal, and porta-caval shunted patients. Scand. J. Gastroent. 1976, 11, 249-256. Acid-base status was determined in 86 patients with cirrhosis of the liver. Group I comprised 55 patients living more than 3 months after examination (stable). Another 18 stable patients with a surgical porta-caval shunt (p.c.a.) formed group II. Group III consisted of 12 terminal patients without p.c.a. examined within the last week of life. With respect to liver function group II was intermediate between I and III. The most common acid-base disturbance in group I was compensated respiratory alkalosis (20 %) followed by compensated metabolic alkalosis (15 %). 50 % of group II presented compensated respiratory alkalosis. 85 % of group III showed metabolic acidosis, which was compensated in only half of the patients. Respiratory alkalosis seemed more related to impairment of liver function than to portasystemic shunting. The genesis of the terminal metabolic acidosis was complex. Renal function was reduced in 92% of group III. and lactic acidosis was found in 36 %. In this group hepatic function was most severely impaired, and 60 % were hypotensive. These disturbances were not related to aetiology or treatment of the liver disease.
Disturbances in acid-base metabolism
Published in Postgraduate Medicine, 1988
Preview By identifying and continuously monitoring the patient at risk for acid-base disorders, the primary care physician can start treatment early and prevent many complications. Dr Hobbs reviews the physiology of these disturbances and describes the four primary acid-base abnormalities: metabolic acidosis, metabolic alkalosis, respiratory acidosis, and respiratory alkalosis.
Common mistakes in managing metabolic disorders
Published in Postgraduate Medicine, 1988
Preview Can volume depletion be managed by pushing oral fluids? What are the consequences of hypophosphatemia? Does a low serum bicarbonate level indicate metabolic acidosis only? In this article, using hypothetical examples, Dr Elms gives tips on avoiding errors in the treatment of patients with volume depletion, hypophosphatemia, and respiratory alkalosis.
Related Knowledge Centers
- Alkalosis
- Hyperventilation
- Chronic
- Acute
- Acid–Base Homeostasis