Arterial transducer placement and cerebral perfusion pressure monitoring: a discussion

To discuss existing disparity of practice and clinical implications of measuring cerebral perfusion pressure (CPP) from differing reference points thus highlighting the need for standardized benchmarks.

When managing traumatic brain injury (TBI), the arterial transducer level is a key to an accurate CPP reading; however, there is a lack of national standards about where to zero arterial transducers when monitoring CPP.

A systematized search using the Cochrane library database, Pubmed database, Medline, British Library on line, CINAHL and PROQUEST using key search terms was used to identify articles that could form a basis for a discussion. Papers published between 2000 and 2008 were included. Papers that did not discuss arterial transducer level placement and CPP were excluded. The Brian Trauma Guidelines 2007 were scrutinized for recommendations.

Of 57 empirical studies accessed, none reported or explored the placement of the arterial transducer during CPP measurement. Conflicting opinions were identified within the literature and there were no recommendations made for practice within the Brain Trauma Foundation Guidelines 2007.

At the present time, there is insufficient evidence for recommending standard placement for mean arterial pressure (MAP) measurements for patients with TBI. There are implications to consider as the treatment prescribed will differ depending on where the arterial transducer is placed because the MAP and CPP displayed will fall by 15 mm Hg at a head elevation of 30 degrees. This poses a number of questions: is the CPP underestimated with the arterial transducer placed at head level? Is the CPP overestimated if the transducer is placed at mid axilla level?

Further research is recommended. However, studies would be difficult to power as head-injured patients constitute a heterogeneous population. Professional consensus should be applied and standardized benchmarks agreed.