The following arterial blood gas and biochemistry results are from a patient with chronic cardiac and respiratory disease and recent profuse vomiting.
FiO2 | 0.4 | |
pH | 7.5 | |
PaO2 | 58.0 mmHg | |
PaCO2 | 47.0mmHg | |
HCO3- | 34.8 mmol/L | (22 - 27) |
BE | 10.2 mmol/L | (-2.0 to +2.0) |
Na+ | 137mmol/L | (135 - 145) |
K+ | 2.5mmol/L | (3.5 - 5.0) |
Cl- | 92mmol/L | (95 - 105) |
a) Describe the acid-base and the metabolic disturbance.
b) List the potential causes of these abnormalities in this patient.
c) Outline the management of the metabolic and acid-base disturbance
The major abnormalities are:
a) Metabolic alkalosis with respiratory compensation
b) Hypokalemia and hypochloremia
c) Normal anion gap
d) An increased apparent strong ion difference [(Na + K) – Cl] = 47
Possible causes in this patient include
a) Diuretic therapy
b) Steroid therapy
c) Vomiting from gastric outlet obstruction
d) Post hypercapnic alkalosis
Outline the management of the metabolic and acid-base disturbance.
1) Normal saline administration
2) K supplements
3) Acetazolamide
Let us dissect these results systematically.
Thus, this is a reasonably well compensated metabolic alkalosis.
There is also hypochloraemia and hypokalaemia.
The patient has chronic cardiac and respiratory disease, and has been vomiting.
Thus, the broad list of potential causes of metabolic alkalosis can be narrowed to the following:
The college then go on to suggest three uninspired management options. For instance, they want to replace potassium, which is a sensible reaction to a low potassium, but not an elegant solution to any underlying problem. Similarly, acetazolamide and sodium chloride may seem essentially cosmetic measures, as they only serve to improve the appearance of the blood gas.
Management of metabolic alkalosis is discussed in greater detail elsewhere. Most of the detail can be found in the following literature sources:
In brief:
Tripathy, Swagata. "Extreme metabolic alkalosis in intensive care." Indian journal of critical care medicine: peer-reviewed, official publication of Indian Society of Critical Care Medicine 13.4 (2009): 217.
Galla, John H. "Metabolic alkalosis." Journal of the American Society of Nephrology 11.2 (2000): 369-375.
Pahari, D. K., et al. "Diagnosis and management of metabolic alkalosis."JOURNAL-INDIAN MEDICAL ASSOCIATION 104.11 (2006): 630.
Palmer, Biff F., and Robert J. Alpern. "Metabolic alkalosis." Journal of the American Society of Nephrology 8.9 (1997): 1462-1469.
Gennari, F. John. "Pathophysiology of metabolic alkalosis: a new classification based on the centrality of stimulated collecting duct ion transport." American Journal of Kidney Diseases 58.4 (2011): 626-636.
Ferrara, A., et al. "[Physiopathological and clinical data on post-hypercapnic metabolic alkalosis. A case of severe hypercapnia treated with drugs and in an" iron lung"]." Minerva medica 70.1 (1979): 67-73.
Banga, Amit, and G. C. Khilnani. "Post-hypercapnic alkalosis is associated with ventilator dependence and increased ICU stay." COPD: Journal of Chronic Obstructive Pulmonary Disease 6.6 (2009): 437-440.
Webster, Nigel R., and Vivek Kulkarni. "Metabolic Alkalosis in the Critically III." Critical reviews in clinical laboratory sciences 36.5 (1999): 497-510.