In case we have forgotten:
pH – expression of acidity and refers to the amount of hydrogen ion concentration. The alkalinity or acidity of a solution depends on the degree of hydrogen ion concentration. An increase in the hydrogen ions results in a more acid solution, while a decrease results in a more alkaline solution.
pH of 7 – is considered neutral because it is at this concentration that the hydrogen ions balance the hydroxyl ions. Below 7 is acid, the lower the number, the stronger the acid. A pH above 7.0 is a base; the higher the number, the stronger the base. Blood pH is slightly alkaline (basic) with a normal range of 7.36-7.44.
Drug pH – is the product formulation pH and results in optimum solubility or stability. Significant variance from the ideal pH can lead to drug decomposition or precipitation. Ready-to-Use products are not neutral because optimum drug stability is usually found at the extremes of pH. Drug manufacturers all stated that their products are as close to physiologic norms as the pharmaceutical parameters permit.
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Many of us know the INS Standard of Practice statement regarding infusate pH – less than 5 or greater than 9. We have used this guideline to mean that if the pH is within 5-9, the infusate is safe to infuse via any peripheral device. However, if the pH is less or above, then infusion via a peripheral device is not recommended and may cause problems, such as phlebitis. So if an infusate has this pH, how should it be given? If not peripheral, next obvious choice is central access. Of course, there’s osmolarity to consider as well but for now, let’s focus on pH. Over the years, this pH statement became a strong and sole criteria for a central line placement especially for medications such as Vancomycin.
A recent article published in the Journal of Infusion Nursing reviewed and re-evaluated the evidence on pH of IV drugs alone as the sole factor driving the decision for central vascular access.
Gorski, LA.; Hagle, ME.; Bierman, S Intermittently Delivered IV Medication and pH: Reevaluating the Evidence Journal of Infusion Nursing. 38(1):27-46, January/February 2015.
Abstract: The Infusion Nurses Society’s Infusion Nursing Standards of Practice has treated pH as a critical factor in the decision-making process for vascular access device selection, stating that an infusate with a pH less than 5 or greater than 9 is not appropriate for short peripheral or midline catheters. Because of the Standards, drug pH is not an uncommon factor driving the decision for central vascular access. In this era of commitment to evidence-based practice, the pH recommendation requires reevaluation and a critical review of the research leading to infusate pH as a decisional factor. In this narrative literature review, historical and current research was appraised and synthesized for pH of intermittently delivered intravenous medications and the development of infusion thrombophlebitis. On the basis of this review, the authors conclude and assert that pH alone is not an evidence-based indication for central line placement.
Method: This article used a narrative literature review process (1943-2014) to address the evidence on pH as a factor in the development of infusion thrombophlebitis and the subsequent practice standard guiding vascular access device selection. The authors provided an evidence table of human studies and literature reviews on Intermittent Drug Delivery and pH.
Conclusion: For intermittently delivered IV medications, the authors assert that (1) pH alone is not an evidence based indication for central line placement, and (2) extremely low or high pH levels need further examination with regard to critical values that cause severe and damaging phlebitis. Decision making, as it relates to choosing the most appropriate vascular access site and device, is not simple and cannot be based on a single factor, such as drug/solution pH. Rather, it must be based on many factors, such as anticipated duration of infusion therapy, type and number of infusates, location of the peripheral IV catheter, catheter size, condition of the patient’s veins, and patient preference.
Now we know! A great article with an excellent evidence based table. One important note, as the authors did state, this article’s focus is on intermittent infusions (delivery) of IV medications.