Metabolic acidosis in the elderly
Introduction
Introduction to metabolic acidosis in the elderly Metabolic acidosis (acid substitution) is the most common type in the elderly, which is caused by an increase in non-volatile acids in the body or a decrease in alkali in extracellular fluid. Its main feature is the decrease in plasma HC03-concentration and PaCO2 compensatoryness. Decline, its main compensatory mechanism is to rely on the kidneys to retain bicarbonate and respiratory excretion. basic knowledge The proportion of illness: 0.001% Susceptible people: the elderly Mode of infection: non-infectious Complications: arrhythmia heart failure coma shock
Cause
The cause of metabolic acidosis in the elderly
(1) Causes of the disease
1. Circulatory dysfunction, insufficient tissue perfusion.
2. Hypoxemia.
3. The low temperature causes the blood vessels to contract, and the microcirculation is poorly perfused.
4. High fever or prolonged hunger or diabetes, increased blood ketone.
5. "Alkaline" acidosis caused by severe diarrhea, intestinal fistula or extensive burns.
6. Advanced tumors with poor liver function.
7. Malnutrition, while intravenous high-nutrition treatment.
8. Renal insufficiency.
(two) pathogenesis
Non-volatile acids are mainly derived from the catabolism of sugars, fats and proteins. The main pathogenesis of acid substitution is the increase in the production of non-volatile acids and the reduction of renal excretion.
Prevention
Prevention of metabolic acidosis in the elderly
Replenishing alkali should pay attention to: Correct acid poisoning too quickly, so that free high calcium is rapidly reduced, leading to hand and foot sputum, acid deficiency in the cells, even if the blood potassium is normal, it should be appropriate potassium.
Complication
Complications of metabolic acidosis in the elderly Complications arrhythmia heart failure coma shock
Severe acidosis can be complicated by arrhythmia, heart failure, and even ventricular fibrillation, coma, shock and so on.
Symptom
Symptoms of metabolic acidosis in the elderly Common symptoms Arrhythmia, coma, metabolic acidosis, drowsiness, potential poisoning, cyanide burns, and combined poisoning
The main symptoms of acidosis are strong and deep breathing. In severe cases, central nervous system depression symptoms such as drowsiness, paralysis and even coma may occur. If accompanied by hyperkalemia or hypercalcemia, it may be characterized by increased cardiac stress. , arrhythmia and decreased neurogenic excitability and decreased sputum reflexes.
According to the performance of acidosis, combined with the primary cause of the disease, clinically suspected acid, must be analyzed by arterial blood gas to determine the presence of acid, development stage and compensation.
Decompensated acid
1pH value <7.35;
2PaCO2 is in the normal range; 3HC03- is decreasing;
The ratio of 4H2CO3 to HCO3- is increased from normal 1:20 to 1:15-10;
5BE negative value increases;
6 carbon dioxide binding capacity (CO2CP) <21mmol / L.
2. Compensatory acid
1pH is normal (7.35~7.45);
2HCO3-decline;
3PaCO2 drops;
The ratio of 4H2CO3 to HCO3- is normal (1:20).
Examine
Examination of metabolic acidosis in the elderly
Blood gas analysis
Blood gas analysis can obtain blood pH, PCO2, SB, AB, BB, BE and other values, which can basically clarify various simple and mixed acid-base balance disorders. Metabolic acidosis is characterized by pH lowering, SB, AB, BB, BE have fewer primary bases and AB equals SB, and PCO2 compensatory decreases.
2. Anion gap (AG) determination
The AG value of metabolic acidosis can be normal or increased, but it will not decrease. When AG is normal, it is hyperchloremia metabolic acidosis. When AG is increased, it is normal blood chlorine metabolic acidosis. The measurement of AG helps metabolism. Analysis of the causes of acidosis.
3. Other
If the AG value is high, there are diseases or factors causing lactic acidosis. Exogenous supplementation of HCO3- can not make the plasma HCO3-, the concentration is steadily increased, suggesting that the acid in the body is continuously produced, and the plasma is highly suspected of lactic acidosis. Lactic acid acidosis can be diagnosed by lactic acid levels above 4 mmol/L.
The diagnosis of ketoacidosis needs to prove the presence of ketosis. The ketone body can be tested with a nitroprusmate tablet. This reagent reacts with a 1:1 diluted serum. If it is "4+", it strongly indicates ketoacidosis. This reagent reacts only with acetoacetic acid and acetone, but does not react with -hydroxybutyric acid. When diabetic ketoacidosis occurs, -hydroxybutyrate accounts for about 75% of circulating ketone bodies, -hydroxybutyric acid. Difficulties in detection, an indirect way to reflect all ketone bodies is to add a few drops of hydrogen peroxide to the urine sample, convert the -hydroxybutyric acid to acetoacetate by non-enzymatic reaction, and then use the nitroprusside tablets. Methods Detection, diabetic acidosis is the most common ketoacidosis in the clinic.
At present, the domestic blood gas analyzer has been quite popular. It is convenient, fast and accurate to detect with this instrument. All the data can be obtained in a short time with a small amount of blood. Since the price of the instrument is still high, some hospitals fail to purchase, still separate Determination of blood pH, HCO3- and PCO2, and whether the results are accurate should be verified.
1. Calculation and verification method
The measured pH, HCO3- and PCO2, 2 of the 3 values are substituted into the equation:
[H+]=24×PCO2 The unit of HCO3- or medium [H+] is nmol/L, the unit of PCO2 is mmHg (calculated as kPa to mmHg, kPa=0.1333×mm-Hg), and the unit of HCO3- is mmoL/L The calculated third value is consistent with the actual measured value, indicating that the measurement result is reliable, otherwise the measurement result is inaccurate, and at least one of the measurement results is incorrect. In the detection of the blood gas analyzer, it is actually measured. It is [H+] and PCO2, and HCO3- is obtained by calculation.
2. Search verification method
Use the Siggaand-Andersen acid-base equilibrium nomogram to verify that if the three values determined above are connected in a straight line or an approximate straight line on the graph, the measured values are credible, otherwise at least one of them is wrong.
Diagnosis
Diagnosis and differential diagnosis of metabolic acidosis in the elderly
Once the acid-producing diagnosis is established, the anion gap (AG) should be calculated immediately to identify whether it is an AG-increasing acid or AG normal-acid. The etiology and characteristics are shown in Table 1, and the respiratory compensatory response is judged to be appropriate. Eliminate mixed acid-base imbalances.
1. Calculation of anion gap (AG)
Under normal circumstances, the sum of all the cations in the extracellular fluid is equal to the sum of all the anions. The so-called AG is the difference between the unmeasured anion and the unmeasured cation. The obvious increase of AG often indicates the accumulation of organic acid in the body. The AG can be calculated from the measurable ions. :AG=(Na++K+)-(Cl-+HCO3-), the normal value is 8-16 mmol/L.
2. Judgment of respiratory compensatory response when replacing acid
There is usually a fixed proportional relationship between the hydrogen ion concentration and the PaCO2 and bicarbonate measured by blood gas analysis.
PaCO2 (mmHg) = the last two digits of the pH value, or
PaCO2 (mmHg) = 1.5 [HCO3-] + 8 ± 2, or
PaCO2(mmHg)=HCO3-+15
If it is outside the range, it suggests that mixed acid-base imbalance exists. For example, acid substitution with sulphate often indicates hypoxemia associated with pneumonia or adult respiratory distress syndrome; if no hypoxemia, respiratory alkalosis is often The earliest signs of sepsis.
