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Using Order Entry for Alerts of Dose Conversion Between Potassium Salts to Prevent Physician Dosing Errors
The Joint Commission Journal on Quality and Patient Safety Letter to the Editor
Using Order Entry for Alerts of Dose Conversion Between Potassium Salts to Prevent Physician Dosing Errors
D
espite the widespread use of the various potassium salts, confusion over appropriate dosing of potassium phosphate persists,1,2 coincident with its continued listing as a high-alert drug product.3 This is due to the routine expression of the product in order-entry systems by its polyvalent phosphate anion [in millimoles (mM)] rather than by its monovalent potassium cation [in milliequivalents (mEq)]. Numerous errors can result because nurses and physicians typically understand potassium dosing only in terms of mEq. Furthermore, there is a tendency toward overdose, given that each milliliter of potassium phosphate contains 4.4 mEq of potassium versus 3 mMol of phosphate, if the physician mistakenly assumes a 1:1 equivalence. However, such dosing errors may not set off a dose alert in most systems because of the subtlety of the mEq-mMol differential. Of the two available salts of potassium, chloride is far more frequently prescribed than phosphate. At Upstate Medical University Hospital (UMUH) in 2007, 45,808 intravenous (IV) unit doses of potassium chloride were dispensed, compared with 2,446 of potassium phosphate. This disparity in the frequency of use of these two products by most physicians, coupled with a misunderstanding in dose-equivalence between the two salts, provided the setting for a near-miss overdose. In summer 2008, a 44-year-old woman with diabetic nephropathy and a baseline serum creatinine of 2.6 mg/dL presented to UMUH with diabetic ketoacidosis (DKA). Pertinent serum values were an anion gap of 22, glucose of 460 mg/dL, pH of 7.25, positive ketones, creatinine of 3.0 mg/dL and potassium of 3.7 mEq/L. Sodium chloride 0.9% with 40 mEq of potassium chloride added to each liter was infused at 250 mL/hr initially, along with IV regular insulin at 4 units per hour via continuous infusion. By the fifth hospital day, the anion gap normalized and creatinine returned to baseline, but the potassium remained at 3.2 mEq/L. The phosphorous at that time was 0.8 mM/L. The physician, intending to convert the amount of potassium in the chloride salt (40 mEq) in the maintenance intravenous infusion to the equivalent amount of potassium in the phosphate salt, mistook a 1:1 equivalence, and potassium phosphate 40 mMol was entered into our orderentry system (equivalent to 58.4 mEq of potassium chloride). The error was averted by the communication between the
April 2009
dispensing pharmacist and the physician at the time of the preparation of the admixture. The physician reported his error to the institutional pharmacy and therapeutics committee’s medication error task force for action on this one event. The notification came with the suggestion that the conversion of 1.46 mEq of potassium chloride to 1 mM potassium phosphate be “red-flagged” in a simple alert box (without the capacity to detect whether a dose was changed after display) at the point of prescribing every time IV potassium phosphate is selected for system entry. This rule was created and implemented systemwide within three weeks of the initial error, with no subsequent similar episodes. A hospitalwide atmosphere of a nonpunitive error reporting system promotes self-reporting.4 This milieu then creates an environment that encourages suggestions of corrective actions for systemwide implementation. As in this case, these suggestions can then result in actionable systems changes to bring critical information to the actual point of physician order entry, a process improvement documented to more favorably impact drug safety practices than by educational reminders that are removed from the actual time of prescribing.5 J David F. Lehmann M.D., Pharm.D., is Professor of Medicine and Pharmacology, SUNY Upstate Medical University, Syracuse, New York; Paul Lipinoga, B.S. Pharm., and John DeGrazio, B.S. Pharm., are pharmacists, Department of Pharmacy; and Neal Seidberg, M.D., is Associate Professor, Department of Pediatrics. Please address requests for reprints to David F. Lehmann, [email protected].
References 1. Institute for Safe Medications Practices: Dose confusion with phosphorus containing products. ISMP Medication Safety Alert! Dec. 1, 1999. http://www.ismp.org/ Newsletters/acutecare/articles/19991201.asp?ptr=y (last accessed Feb. 19, 2009). 2. Cornish P., Hyland S., Koczmara C.: Enhancing safety with potassium phosphates injection. Dynamics 18:34–36, 2007. 3. Institute for Safe Medications Practices: ISMP’s List of High-Alert Medications 2008. http://www.ismp.org/Tools/highalertmedications.pdf (last accessed Feb.19, 2009). 4. Lehmann D.F., et al.: Every error a treasure: improving medication use with a nonpunitive reporting system. Jt Comm J Qual Patient Saf 33:401–407, Jul. 2007. 5. Shannon R.P., et al.: Using real-time problem solving to eliminate central line infections. Jt Comm J Qual Patient Saf 32:479–487, Sep. 2006.
Volume 35 Number 4
Copyright 2009 Joint Commission on Accreditation of Healthcare Organizations
179
Using Order Entry for Alerts of Dose Conversion Between Potassium Salts to Prevent Physician Dosing Errors
D
espite the widespread use of the various potassium salts, confusion over appropriate dosing of potassium phosphate persists,1,2 coincident with its continued listing as a high-alert drug product.3 This is due to the routine expression of the product in order-entry systems by its polyvalent phosphate anion [in millimoles (mM)] rather than by its monovalent potassium cation [in milliequivalents (mEq)]. Numerous errors can result because nurses and physicians typically understand potassium dosing only in terms of mEq. Furthermore, there is a tendency toward overdose, given that each milliliter of potassium phosphate contains 4.4 mEq of potassium versus 3 mMol of phosphate, if the physician mistakenly assumes a 1:1 equivalence. However, such dosing errors may not set off a dose alert in most systems because of the subtlety of the mEq-mMol differential. Of the two available salts of potassium, chloride is far more frequently prescribed than phosphate. At Upstate Medical University Hospital (UMUH) in 2007, 45,808 intravenous (IV) unit doses of potassium chloride were dispensed, compared with 2,446 of potassium phosphate. This disparity in the frequency of use of these two products by most physicians, coupled with a misunderstanding in dose-equivalence between the two salts, provided the setting for a near-miss overdose. In summer 2008, a 44-year-old woman with diabetic nephropathy and a baseline serum creatinine of 2.6 mg/dL presented to UMUH with diabetic ketoacidosis (DKA). Pertinent serum values were an anion gap of 22, glucose of 460 mg/dL, pH of 7.25, positive ketones, creatinine of 3.0 mg/dL and potassium of 3.7 mEq/L. Sodium chloride 0.9% with 40 mEq of potassium chloride added to each liter was infused at 250 mL/hr initially, along with IV regular insulin at 4 units per hour via continuous infusion. By the fifth hospital day, the anion gap normalized and creatinine returned to baseline, but the potassium remained at 3.2 mEq/L. The phosphorous at that time was 0.8 mM/L. The physician, intending to convert the amount of potassium in the chloride salt (40 mEq) in the maintenance intravenous infusion to the equivalent amount of potassium in the phosphate salt, mistook a 1:1 equivalence, and potassium phosphate 40 mMol was entered into our orderentry system (equivalent to 58.4 mEq of potassium chloride). The error was averted by the communication between the
April 2009
dispensing pharmacist and the physician at the time of the preparation of the admixture. The physician reported his error to the institutional pharmacy and therapeutics committee’s medication error task force for action on this one event. The notification came with the suggestion that the conversion of 1.46 mEq of potassium chloride to 1 mM potassium phosphate be “red-flagged” in a simple alert box (without the capacity to detect whether a dose was changed after display) at the point of prescribing every time IV potassium phosphate is selected for system entry. This rule was created and implemented systemwide within three weeks of the initial error, with no subsequent similar episodes. A hospitalwide atmosphere of a nonpunitive error reporting system promotes self-reporting.4 This milieu then creates an environment that encourages suggestions of corrective actions for systemwide implementation. As in this case, these suggestions can then result in actionable systems changes to bring critical information to the actual point of physician order entry, a process improvement documented to more favorably impact drug safety practices than by educational reminders that are removed from the actual time of prescribing.5 J David F. Lehmann M.D., Pharm.D., is Professor of Medicine and Pharmacology, SUNY Upstate Medical University, Syracuse, New York; Paul Lipinoga, B.S. Pharm., and John DeGrazio, B.S. Pharm., are pharmacists, Department of Pharmacy; and Neal Seidberg, M.D., is Associate Professor, Department of Pediatrics. Please address requests for reprints to David F. Lehmann, [email protected].
References 1. Institute for Safe Medications Practices: Dose confusion with phosphorus containing products. ISMP Medication Safety Alert! Dec. 1, 1999. http://www.ismp.org/ Newsletters/acutecare/articles/19991201.asp?ptr=y (last accessed Feb. 19, 2009). 2. Cornish P., Hyland S., Koczmara C.: Enhancing safety with potassium phosphates injection. Dynamics 18:34–36, 2007. 3. Institute for Safe Medications Practices: ISMP’s List of High-Alert Medications 2008. http://www.ismp.org/Tools/highalertmedications.pdf (last accessed Feb.19, 2009). 4. Lehmann D.F., et al.: Every error a treasure: improving medication use with a nonpunitive reporting system. Jt Comm J Qual Patient Saf 33:401–407, Jul. 2007. 5. Shannon R.P., et al.: Using real-time problem solving to eliminate central line infections. Jt Comm J Qual Patient Saf 32:479–487, Sep. 2006.
Volume 35 Number 4
Copyright 2009 Joint Commission on Accreditation of Healthcare Organizations
179