Peripheral intravenous cannula (PIVC) placement is often an essential emergency medicine precursor to lifesaving treatment, but it is not harmless. Patients frequently and without proper consideration of the consequences receive a 'just-in-case' PIVCs as part of their assessment and admission, which, in a not insignificant number of patients, remains unused or idle in situ. We reviewed the literature and performed a thematic analysis of data collated from 21 articles published in the past 24 years regarding redundant PIVCs. The following five common themes emerged: heterogeneous prevalence data on post-insertion PIVC usage, preventable intravascular complications, financial burden, loss of time and a culture of over-investigating. The prevalence of PIVC insertions and idle PIVCs was heterogeneous among these publications; the median ED idle PIVC prevalence value was 32.4%. This practice is associated with compromised patient safety, squandered finances and misdirected practitioner time. Cultures of convenience and shortfalls in PIVC-related education facilitate the prevalence of idle PIVCs.