Vomiting of gastric contents

Metabolic alkalosis is produced iatrogenically in the case of a subject who habitually swallows baking powder (sodium bicarbonate) to allay the pain of duodenal ulcer. The responses of the body to a simple metabolic alkalosis are the converse of those for metabolic acidosis. It is left as an exercise for the reader to follow the changes occurring in this disturbance. Metabolic alkalosis also occurs clinically as a result of vomiting of gastric contents, but here the... 

Let us now consider what happens when the effect which was secondary in the primary respiratory disorder is instead the primary disorder. This would then be a primary metabolic alkalosis, as in the vomiting of gastric contents. In the uncompensated condition, there is a positive base excess with a normal partial pressure of carbon dioxide already noted (Table 4.4C). The respiratory compensation is hypoventilation, brought about by the partial withdrawal of the normal stimulus of hydrogen ions to the peripheral chemoreceptors. The partial pressure of carbon dioxide rises, adding a respiratory component to the acid-base disorder (Table 4.4D). 

Vomiting of gastric contents. A common example occurs in the vomiting of gastric contents, which results in the loss of hydrogen ions. When the vomiting is mild to moderate, the metabolic alkalosis initiates the sequence of events which you followed in section A3. 

With persistent prolonged vomiting of gastric contents the loss of water and electrolytes becomes severe. The response to dehydration takes precedence over acid-base adjustments. This may lead to the condition of paradoxical aciduria. The remainder of this exercise conducts you through one of the mechanisms contributing to this situation. 

Persistent vomiting of gastric contents. There is a loss of HCl, NaCl, water. Hence the kidney is called upon to retain sodium and chloride and to restore fluid volume as well as respond to the disturbance of acid-base balance. 

Now we consider how the diagram is modiAed in a patient with persistent vomiting of gastric contents. Because of the loss of hydrochloric acid in the vomitus, the concentration of chloride in the plasma (falls, rises) and the amount of chloride Altered at the glomerulus is (more, less) than normal. The difference between the lengths of the chloride and sodium arrows is therefore (reduced, exacerbated). Consequently there will tend to be an (increase, decrease) in movement of HCOs", H", through the tubule wall in the directions of... 

Acid-base status and persistent vomiting of gastric contents... 

Metabolic alkalosis can occur when there is excessive H+ loss from the body, via loss of gastric contents in vomiting, or when a patient takes excessive quantities of antacid medication. 

The three consecutive phases of emesis include nausea, retching, and vomiting. Nausea, the imminent need to vomit, is associated with gastric stasis. Retching is the labored movement of abdominal and thoracic muscles before vomiting. The final phase of emesis is vomiting, the forceful expulsion of gastric contents due to GI retroperistalsis. 

To 10 ml of gastric contents, stomach washings, or vomit, add 10 mg of diphenylamine sulphate and dien carefully add 5 ml of sulphuric acid to form a separate layer. A blue ring at the interface is indicative of nitrites. 

Gastrointestinal water losses also can result in dehydration. We secrete approximately 8 to 10 L fluid per day into our intestinal lumen. Normally, more than 90% of this fluid is reabsorbed in the intestines. The percentage reabsorbed can be decreased by vomiting, diarrhea, tube drainage of gastric contents, or loss of water into tissues around the gut via bowel fistulas. 

The effect of vomiting on add-base status depends on whether there is a net loss of add or of alkali in the vomitus. In cases where the movement of chyme from the stomach to the duodenum is obstructed, the resulting vomiting will be of gastric contents which are add. In other cases of vomiting due, for instance, to irritation of the small bowel, the vomitus is a mixture of gastric contents, which are add, and of duodenal contents, which are alkaline. In this situation the vomitus is add if gastric juice predominates and alkaline if duodenal contents predominate. 

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