Lecture on metabolic acidosis

2021-08-12 07:09 PM

Diagnose when pH decreases (decreased myocardial contractility, decreased blood pressure, decreased response to vasopressors (compensated from the lungs, rapid deep breathing to increase CO2 clearance)

Due to accumulation of insoluble acids or decreased alkaline reserves.

Cause

Acidosis with anion gap:

Normal anion gap: Na+ - (Cl- + HCO-3) = 12 + 4mEq/l.

Acute renal failure.

Ketoacidosis: diabetes, malnutrition.

Lactic acidosis:        

Infection shock.

Heart shock.

Shock due to volume reduction.

Cardiac arrest.

Diabetes.

Drug poisoning (Salicylate, Methanol, Ethylene glycol, Paraldehyde, Ethanol).

Normal anion gap acidosis:

Because loss of HCO3- is often accompanied by hypoK+ blood:

Diarrhea.

Treatment with Diamox.

Renal tubular acidosis.

Chronic acidosis due to renal failure:

Clearance <20ml/minute

HCO-3 <15mEq/l must give Sodium bicarbonate 1.8-4.8g/day to prevent bone softening.

Renal tubular acidosis:

Type I (dital): distal tubular acidosis for bicarbonate 1.5mEq/kg/day.

Type II (proximal): due to inadequate reabsorption of HCO-3, treat only when HCO-3 is <16-18mEq/l, restore 3-10mEq/l/day to replace urinary bicarbonate loss, If the HCO-3 concentration is still higher than >18mEq/l, there is no need to give bicarbonate because the kidneys are still able to acidify the urine, adding kalium because the K+ in the blood is severely reduced. Limit salt and add hydrochlorothiazide.          

Lactic acidosis type A: inadequate tissue oxygenation: septic shock, cardiogenic shock, hypovolemic shock.

Type B lactic acidosis: hypoxia to tissues and no obvious clinical manifestations in diabetes mellitus, major epileptic seizures, drug toxicity (salicylate, ethanol, methanol, ethylene glycol).

Diagnosis: when pH decreases (decreased myocardial contractility, decreased blood pressure, decreased response to vasopressors (compensated from the lungs, rapid deep breathing to increase CO2 clearance).

Clinical:

Breathe fast and deep.

Fast heart.

Blood pressure drops.

Consciousness disorder.

Subclinical:

HCO3- decreased, pH decreased, PaCO2 decreased.

Offset PCO2 =1.5 x HCO3- + 8 + 2.

Treatment:

Treat the cause.       

Bicarbonate supply:

HCO3- deficiency = (HCO3- desired- HCO3- measured) x 0.4 x P/kg body weight

Sodium bicarbonate 50-100mEq as hypertonic IV >30-60 min or in isotonic infusion fluids.

Adjust to pH = 7.2 then endogenous bicarbonate production will occur when the cause of acidosis is compensated.

Use of insulin to treat hyperglycemia in acidosis caused by hyper ketosis or lactic acidosis.

Causes: infection, diabetes.

Correct water and electrolyte disorders.

Dialysis.

Acute metabolic acidosis:

Occurs in patients with shock, cardiac arrest.

Kussmaul's breathing pattern (fast and deep).

pH<7,2.

Use NaHCO3-8.4% 1-2 ampoules intravenously at a dose of 1mEq/kg or NaHCO3-8.4% 2-3 ampoules/ Glucose 5% 1000ml: compensate in the first 3-4 hours if there is no congestive heart failure blood, the rest will be refunded when there is a response of the patient, remember to add more Potassium (when potassium is normal or decreased) if not noticed, it will lead to blood K + and blood Ca + decrease and do not give when pH> 7.2.

Complications from anti-acid therapy

Due to excessive use of Na+, the extracellular fluid volume overload can easily lead to acute pulmonary edema.

Tetany: due to too much and too fast infusion of SB not completely due to the reduction of ionized calcium.

Decrease blood K+.

Causes alkaline blood.