An electronic literature search for articles published between January 1990 and September 2011 was conducted by using the PubMed, CINAHL, SCOPUS, and Cochrane Library databases. The update of this clinical practice guideline is the result of reviewing a total of 124 articles: 3 randomized controlled trials, 103 prospective trials, 1 retrospective study, 3 case studies, 11 review articles, 2 surveys and 1 consensus paper on transcutaneous monitoring (TCM) for P(tcO(2)) and P(tcCO(2)). The following recommendations are made following the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria: (1) Although P(tcCO(2)) has a good correlation with P(aCO(2)) and is a reliable method to evaluate plasma CO(2) levels, it is recommended that arterial blood gas values be compared to transcutaneous readings taken at the time of arterial sampling, in order to verify the transcutaneous values, and periodically as dictated by the patient's clinical condition. (2) It is suggested that P(tcCO(2)) may be used in clinical settings where monitoring the adequacy of ventilation is indicated. (3) It is suggested that P(tcO(2)) and P(tcCO(2)) may be used in determining the adequacy of tissue perfusion and monitoring of reperfusion. (4) It is suggested that TCM should be avoided in the presence of increased thickness or edema of the skin and/or subcutaneous tissue where the sensor is applied. (5) It is recommended that sites used for a TCM be changed as often as necessary and that they be alternated and observed to avoid thermal injury. Manufacturer recommendations should be followed.