Abstract
Numerous small books seeking to simplify the interpretation of blood gas analysis have been published over the years, presumably in response to the perceived complexity of the subject. As the author of this guide writes, ‘…many health care professionals find it difficult to get to grips with blood gas analysis. It often seems complex and daunting…’. Enlightenment, she suggests, can be attained by the reader if ‘…you work your way through the book and carry out all the exercises…’.
The book is primarily intended for nurses, particularly those working in critical care, and in addition to chapters on the pathophysiology of hydrogen ion homoeostasis and 19 sets of data for interpretation (with answers and explanations provided) includes a short account of how to take (though not, if it is necessary, to transport) an arterial blood specimen.
The account of pathophysiology is simple but unfortunately couched entirely in terms of pH rather than hydrogen ion concentration. In your reviewer's opinion, at least part of the perceived complexity of this topic is related to the use of a logarithmic expression (and negative, to boot) rather than hydrogen ion concentration per se. It is incorrectly stated that blood gas analysers measure (rather than calculate) bicarbonate (and standard bicarbonate) concentrations. Furthermore, the term ‘standard bicarbonate’ is not explained so that its purported value (to indicate a ‘metabolic’ component to an acid–base disturbance but without distinguishing between this being primary or compensatory) escapes comment.
The sets of data for interpretation are presented without any clinical information. This is regrettable (indeed, since the author comments that clinical data are ‘luxury you don't have in this workbook’, one wonders why it has not been provided). While it may be advantageous to expand the list of possible causes of each of the sets of data, it does not reflect clinical practice, where many blood gas analyses are done using point-of-care testing by the individual collecting the specimen. And the fact that two primary disorders (for example, co-existing respiratory acidosis and non-respiratory alkalosis) can result in data identical to that produced by the physiological compensation for a primary disturbance is not discussed. Although this is regrettable, it would not prevent readers from working out the additional possibilities for themselves, and the data-sets would be useful as a source of teaching material, while the simple diagram that provides a guide to interpretation based on the sequential consideration of pH and pCO2 emphasizes that enlightenment even when faced with a complex case lies in taking one step at a time.