Understanding blood gases

Key learning points Understand the sampling methods for arterial blood gases Understand and interpret arterial blood gas results. This will include: Oxygen transport in the body Mechanisms of normal acid-base balance Disturbances of acid-base balance Step-by-step guide to arterial blood gas analysis Clinical scenarios Introduction Arterial blood gas (ABG) analysis is now commonplace in perioperative and acute-care settings and is used to aid diagnosis and to monitor the progress of the patient and the response to any interventions. It is essential that staff working in the perioperative environment understand the key principles of ABG analysis so that results can be dealt with quickly and appropriately, thereby improving the safe management of the patient. Arterial blood gas analysis is often central to the management of the patient who is either already critically ill or is at risk of deterioration in their condition (Simpson, 2004). Many patients cared for within the perioperative environment will fall into one of these two categories and this makes ABGs one of the most common tests performed in theatres. Jevon and Ewens (2002) also suggest indications for ABG analysis may include respiratory compromise, evaluation of interventions such as oxygen therapy and respiratory support, as a preoperative baseline and following a cardio-respiratory arrest. It is imperative to note at the start of this chapter that, just as with any investigation, ABGs must always be interpreted in conjunction with other clinical information about the patient (Adam & Osborne, 1997).