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Vancomycin: An Infusion Staple

Twenty percent (20)% of bacterial infections are caused by Staphylococcus Aureus. Several of the S. Aureus strains are now resistant to penicillins, macrolides, tetracycline and aminoglycosides. Due to the increase in resistance and the potential for c. difficile, Vancomycin has become the preferred treatment for staphylococcal infections. The infusion of Vancomycin does present challenges and requires a knowledgeable, skilled nurse in collaboration with a pharmacist and physician.

The adult dose of Vancomycin is 15mg/kg, rounded to the nearest 250 mg increment. The frequency of each dose is determined by the creatinine clearance. This measures the amount of fluid the kidneys filter per minute. In order to infuse every 12 hours, a minimum creatinine clearance of 70mL/min is required. As creatinine clearance decreases, dosing intervals increase to every 24, 48 or 72 hours. Pediatric doses are 10mg/kg per dose infused every 6 hours. Dosing in neonates can also be done at an initial dose of 15mg/kg as a first dose and then 10 mg/kg every 12 hours during the first week of life. The frequency for 1 week to one month of age is every 8 hours.

When Vancomycin was first introduced, a dilution of 5mg/ml was used and infused in a peripheral vein, as this was the only access method at the time. As advances in infusion therapy were made, the use of subclavian and central venous veins were used. With the use of these veins central catheter tip placement and concentrations of 10mg-20mg/ml could be used. One of the challenges associated with the infusion of Vancomycin is vein irritation. Normal serum pH is 7.35-7.45. The pH of Vancomycin is less than 4.0, making it very acidic, which is significantly irritating to the vein. Changing the volume or the diluent does little to change the pH. Because of the acidic nature of Vancomycin, it is most appropriately infused via a central venous catheter, where the drug can be rapidly hemodiluted, thereby decreasing vein irritation. The Infusion Nursing Standards of Practice recommends that medication below a pH of 5 or above 9 is not appropriate through a short peripheral or midline catheter.

The osmolarity of the final solution is another characteristic that can affect vein irritation. The term tonicity is often interchanged with osmolarity when applied to IV fluids. Normal blood osmolarity is between 285 and 295mOsm/L. A solution with a higher osmolarity is more irritating to the vein. The infusion standards recommend solutions greater than 500mOsm/L are not appropriate for short peripheral or midline catheters. Vancomycin in doses between 1 to 2 grams in 100cc sodium chloride has an osmolarity between 328 and 348. Vancomycin in doses between 1 to 2 grams in 250cc sodium chloride has an osmolarity between 316 and 324. These osmolarities that are close to normal are not vein irritants.
 

The number one adverse drug reaction obtained from quality assessment data related to Vancomycin is Red Man's Syndrome (RMS), a side effect related to the immune system. It manifests as skin flushing, erythematous rash on race, neck, and chest; itching and even hypotension. RMS will usually occur with the first dose, but can occur with second or third doses as well. These reactions have been documented at all rates of infusion and are managed by premedication with antihistamines, especially H1 and H2 antagonists. Vancomycin can be given as a first dose in the alternate setting provided the patient is screened in advance, and medication for having anaphalytic medications reactions is available. Other adverse reactions to Vancomycin include renal toxicity. Ototoxicity has been associated with high serum levels, usually 80mg/l. Monitoring for these reactions is a component of the professional clinical monitoring done by an infusion pharmacist and infusion nurse. Infusion pharmacists are conscious of physiologic parameters and work closely with nursing and physicians to determine the appropriate route of administration and solution admixture. The ongoing monitoring of renal function through the creatinine clearance level is critical to adjusting dosing. There is no literature that supports correlation of peak and trough levels with therapeutic efficiency. Peak levels are dependant on the timing of the blood sample and are subject to many variables that could skew results. For these reasons trough levels are more reliable. Trough levels may be useful in monitoring specific patient populations:

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The articles herein are provided for general information and are not intended to provide specific advice or recommendations for any reader.