Acid Base Disturbance in Critically Ill Patients
Mohamed Abdel Aziz Abdel Fattah Abu Mostafa;
Abstract
Acid-base disturbances are very common in critically ill and injured patients as well as contribute significantly to morbidity and mortality. This essay will discuss the physiology, different approaches to understand and diagnose acid base disturbance and highlight on causes and general management of acid base disturbance in the intensive care unit.
There are three primary systems that regulate the H+ concentration in the body fluids to prevent acidosis or alkalosis. The chemical acid-base buffer systems of the body fluids is the first defense, which immediately combine with acid or base to prevent excessive changes in H+ concentration. Its power is determined by the amount and relative concentrations of the buffer components. While the respiratory center is the second, which regulates the removal of CO2 (and, therefore, H2CO3) from the extracellular fluid within a few minutes. The third and most powerful defense line is the kidney excreting either acid or alkaline urine, thereby readjusting the extracellular fluid H+ concentration toward normal during acidosis or alkalosis.
We have assessed three approaches for interpretation of acid base disturbance. The traditional approach is based on Handerson-Hasselbalch formula and includes Base Excess (BE), bicarbonate (HCO3-) based on work done by Ole Siggared-Anderson and Physicochemical (Stewart) Approach based on physical chemistry of water and bicarbonate have no role of acid base balance.
According to Stewart’s theory, pH is independently regulated by three variables: partial pressure of carbon dioxide, strong ion difference (SID), and total amount of weak acids (ATOT).
There are many diseases that lead to changes in acid base balance. These conditions occurred in critical care every day. Conditions such as asthma, chronic obstructive pulmonary disease (bronchitis or emphasaemia), diabetic ketoacidosis, renal disease or failure, any type of shock (sepsis, anaphylaxsis, neurogenic, cardiogenic, hypovolaemia), stress or anxiety which can lead to hyperventilation, and some drugs (sedatives, opoids) leading to reduced ventilation. In addition, some symptoms of disease can cause vomiting and diarrhea, which effects acid base balance. The treatment of any acid base disorder is usually directed to treatment of underlying cause.
There are three primary systems that regulate the H+ concentration in the body fluids to prevent acidosis or alkalosis. The chemical acid-base buffer systems of the body fluids is the first defense, which immediately combine with acid or base to prevent excessive changes in H+ concentration. Its power is determined by the amount and relative concentrations of the buffer components. While the respiratory center is the second, which regulates the removal of CO2 (and, therefore, H2CO3) from the extracellular fluid within a few minutes. The third and most powerful defense line is the kidney excreting either acid or alkaline urine, thereby readjusting the extracellular fluid H+ concentration toward normal during acidosis or alkalosis.
We have assessed three approaches for interpretation of acid base disturbance. The traditional approach is based on Handerson-Hasselbalch formula and includes Base Excess (BE), bicarbonate (HCO3-) based on work done by Ole Siggared-Anderson and Physicochemical (Stewart) Approach based on physical chemistry of water and bicarbonate have no role of acid base balance.
According to Stewart’s theory, pH is independently regulated by three variables: partial pressure of carbon dioxide, strong ion difference (SID), and total amount of weak acids (ATOT).
There are many diseases that lead to changes in acid base balance. These conditions occurred in critical care every day. Conditions such as asthma, chronic obstructive pulmonary disease (bronchitis or emphasaemia), diabetic ketoacidosis, renal disease or failure, any type of shock (sepsis, anaphylaxsis, neurogenic, cardiogenic, hypovolaemia), stress or anxiety which can lead to hyperventilation, and some drugs (sedatives, opoids) leading to reduced ventilation. In addition, some symptoms of disease can cause vomiting and diarrhea, which effects acid base balance. The treatment of any acid base disorder is usually directed to treatment of underlying cause.
Other data
| Title | Acid Base Disturbance in Critically Ill Patients | Other Titles | الإضطرابات الحمضية القاعدية لمرضى الرعاية المركزة | Authors | Mohamed Abdel Aziz Abdel Fattah Abu Mostafa | Issue Date | 2015 |
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