Mistakes or omissions in obtaining patient weights caused almost 500 medication errors in Pennsylvania hospitals over 4.5 years, according to a state watchdog agency.

The Pennsylvania Patient Safety Authority received 479 reports between June 2004 and November 2008 that specifically mentioned incorrect weight measurement as a factor in a medication error. Six incidents (1.3%) resulted in additional care to treat the effects of the mistake, according to a report in Pennsylvania Patient Safety Advisory (2009;6:10-15).

Overall, 310 events (64.7%) led to either over- or under-dosages. Another 47 (9.8%) resulted in IV drips administered at the wrong rate. Five of the top 10 medications involved are high-alert medications, with a heightened risk of causing significant patient harm when used incorrectly. These were heparin (110 reports), enoxaparin (Lovenox; 84 reports), acetaminophen (20 reports), dobutamine (17), and dopamine (17).

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Most incidents involved failures to obtain accurate patient weight measurements or a misuse of that value. For example:

  • Failure to weigh upon arrival. These situations led to estimates that were often inaccurate.
  • Assumptions that documented weights were current or accurate. This was most often a problem among oncology, elderly, or pediatric/neonatal patients, whose weight may change frequently over a short period of time.
  • Mistakes in documentation, e.g. confusion between pounds and kilograms.

More incidents (20.7%) occurred in the emergency department (ED) than anywhere else, often because patients who arrived by ambulance were not weighed at all. “When looking at all patients in the ED, 12% are admitted and 1.3% are sent directly to the ICU,” the report noted. “Therefore, medication errors that occur because of wrong patient weight may perpetuate throughout the patient’s stay.”

The report offers several risk-reduction strategies for hospitals, as well as others for both inpatient and outpatient settings. “It is vitally important that an accurate weight is obtained when patients arrive at a healthcare facility,” the report emphasized.

It suggests standardizing all systems to kilograms to reduce arithmetic mistakes and that clinicians write the patient’s weight and age on every medication order.

“Prescribers need to confirm the patient’s weight is correct for weight-based dosages and write the weight and patient’s age on each order. This can help the dispensing professional double check the appropriate drug and dose,” the report noted.