[Invasive monitoring of arterial gases in intensive care. Indications, misuse and hazards].

Although arterial blood gas analysis remains the "gold standard" for oxygen (O2) and carbon dioxide (CO2) measurements during critical illness, several new techniques are now available for clinicians in this field, i.e. pulse oximetry, transcutaneous (PtcO2) and transconjunctival (PcjO2) O2 monitoring, CO2 continuous measurements in expired gases (capnography) and transcutaneous PCO2 (PtcCO2). While it seems too early to assign a definite role to all these techniques in the management of critically ill patients, several points can be emphasized: 1. pulse oximetry is a cheap, versatile device for monitoring of nonhypoxemic patients; 2. PtcO2 is a good index of poor skin oxygenation and is related to PaO2, but this index should be interpreted with caution in unsteady patients; perhaps its main value is as an early warning that "something is wrong with the patient". PcjO2 may be promising, but more data are needed; 3. PtcCO2 and capnography seem more suitable for research purposes or for patient monitoring in the operating theatre. Finally, it should be emphasized that invasive arterial blood gas measurements using an indwelliing arterial catheter are safe and provide with the best possible acid-base and hemodynamic monitoring. Noncontinuous monitoring of blood gases and, perhaps, the delay between arterial puncture and completion of the analysis seem to be the only drawbacks of this technique.