DISCUSSION
In this single center retrospective analysis, in whom hemodialysis was
performed or recommended by our PCC, when the EXTRIP and Paris criteria
are both in favor of hemodialysis, dialyzed patients generally had
favorable outcomes. When the two criteria are against hemodialysis,
non-dialyzed patients also had favorable outcomes. As reported by its
creators, application of the Paris guidelines prompts dialysis in fewer
patients overall, but when the criteria were discordant, the EXTRIP
criteria outperformed the Paris criteria at identifying potentially ill
patients who might benefit from hemodialysis. Of the cases of
deterioration not identified by the Paris criteria, two were not
identified by the EXTRIP “recommends” criteria, and all four were
identified by the EXTRIP “suggests” criteria. EXTRIP criteria were not
intended to be merged for comparative analysis, but this comparison is
presented here to reflect the merged EXTRIP analysis performed in the
original Paris validation study.
Descriptive data are unfortunately limited for these cases. We cannot
completely exclude processes unrelated to their lithium toxicity
contributing to patients’ deterioration. This qualification, however, is
equally applicable to all cohorts and reflects the typical quality of
data from poison control center databases. Furthermore, poison center
data can be limited by completeness and accuracy for coded clinical
effects and treatments.[10],[11] There may have been variability
between original PCC coders for clinical effects such as “confusion,”
“altered mental status,” and “other-miscellaneous.” Narrative
accounts can be selective in their inclusion/exclusion of relevant data
and can terminate in many cases before the outcome of interest is
determined in a subsequent retrospective study. Long term outcomes such
as SILENT cannot be extrapolated from poison center cases, for example,
as routine follow up on the order of months or years is seldom
performed.
Additionally, our cohort possibly suffers from two sources of selection
bias. There may have been cases in which EXTRIP or Paris criteria were
met, but dialysis was neither recommended nor performed. These cases
would not have been identified by our search criteria but were unlikely
to be significantly ill since most sources prior to EXTRIP suggest more
liberal indications for hemodialysis. Additionally, we only reviewed
cases reported to one regional metropolitan poison center in the United
States. Since poison center reporting is largely voluntary, we may have
missed cases in our catchment area not reported to our center.[12]