He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. On Twitter, he is precordialthump. This site uses Akismet to reduce spam. Learn how your comment data is processed. Reviewed and revised 6 March OVERVIEW obesity affects all four aspects of pharmacokinetics As drug administration based on total body weight can result in in underdosing or overdosing, depending on the characteristics of the drug, weight-based dosing scalars must be considered Lean body weight is the optimal scalar for most IV opioids and anaesthetics The pharmacodynamic profile of drugs may also be affected, e.
Critical Care Compendium. Chris Nickson. His one great achievement is being the father of two amazing children. Medication dosing is often calculated on the basis of a patient's weight, particularly for pediatric patients, who require individualized dose calculations based on their size. Certain drugs given to adults—including some high-alert medications, such as anticoagulants and chemotherapeutic agents—must be administered at doses calculated on the basis of the patient's weight.
Programming an intravenous medication dose and delivery rate for an infusion pump can also be dependent on the patient's weight. Mistakes can occur if the medication dose is calculated using an inaccurate patient weight. Therefore, healthcare organizations should have policies in place stipulating that a medication order can only be filled if information about the patient's weight is available and documented in the medical record.
Nevertheless, several event reports submitted to ECRI Institute PSO indicate that medication orders are sometimes filled even though information about the patient's weight is not provided. Additionally, many of the event reports submitted to ECRI Institute PSO indicate that weight-based dosing errors can occur even when information about a patient's weight is obtained or recorded.
Examples of such errors include the following:. In pediatric patients, weight is needed to accurately tailor a drug dose to the person's weight, age, body surface area, and clinical condition Levine et al. Many medications only come in adult formulations or limited pediatric concentrations and, therefore, need to be carefully reformulated for a smaller person.
Even small weight discrepancies can be significant in children. Because the therapeutic window for many medications is narrower in young patients than in adults, medication errors can affect pediatric patients more seriously than adults. Consequently, dosing errors, like those caused by inaccurate weight and height information, are among the most commonly reported drug errors in children Stucky.
Further complicating the problem, very young patients cannot communicate to their caregivers if something feels wrong when a drug is given. Although not all adult medications are tailored to the person's weight, some such as chemotherapeutic agents require weight-based dosing.
Also, certain patient groups—including those who are elderly, are immunocompromised, are extremely obese, or have impaired renal function—may require more careful attention to dosing. Yet breakdowns are occurring in obtaining the weight of adult patients—even when the information is needed for dosing. Patients who had not been weighed were more likely to have more serious complications than those who had been weighed. Hilmer et al. Ensuring that measures are in place to help clinicians and staff obtain accurate patient weights is essential to prevent patient harm.
Additionally, these measures can protect the organization from the cascade of effects e. For example, the Joint Commission's hospital accreditation standards for medication management stipulate the following Joint Commission :.
Not only can organizations be cited by accrediting agencies and CMS for failing to follow requirements to ensure medication safety, they could also face legal action if a patient is harmed. The analysis did not specify the reasons for the dosing errors; however, it does illustrate that dosing errors—which can occur as a result of weighing mistakes or other reasons—are among the top reasons for medical malpractice claims for medication errors.
Medication errors represented 6. This issue of the national PSO Navigator summarizes the types of weight-based medication dosing errors voluntarily reported to ECRI Institute PSO's event reporting program and recommends strategies to ensure patient weights are accurately obtained, documented, and communicated to the necessary staff involved in the patient's care. Three categories of weight-based dosing errors are summarized in Tables 1, 2, and 3 in this advisory.
Prevention strategies are summarized in the discussion Strategies to Prevent Weight-Based Dosing Errors and in Table 4, which appears later in this advisory. ECRI Institute PSO examined events of weight-based dosing errors that were reported to the event reporting system from September 1, , through August 31, , and that indicated the level of harm to the patient.
This index was originally developed by the National Coordinating Council for Medication Error Reporting and Prevention for reviewing medication errors. The review was limited to those events that resulted in patient harm scores of E results in temporary harm and requires intervention through I contributes to or results in patient's death.
Since the events are voluntarily reported by participating organizations, ECRI Institute PSO is unable to determine the rate of weight-based dosing errors; however, other studies provide insights, confirming the magnitude of these preventable mistakes in pediatric patients and adults. Dosing errors, like those that can occur when a wrong weight is documented, are among the most frequently occurring types of medication errors for pediatric and adult patients. An analysis of medication errors reported to the U.
Dosing errors were the most frequently reported type of medication error for pediatric patients and the second most frequently reported type of medication error in nonpediatric patients, following errors using an unauthorized drug.
Cowley et al. An examination of event reports submitted to the Pennsylvania Patient Safety Authority from June through November found that of the events identified as breakdowns in obtaining, documenting, and communicating patient weights, Other mistakes occurred as a result of incorrectly setting infusion pump rates or giving an extra drug. The report identified two general themes with weight-based dosing errors, similar to two of the three identified in the ECRI Institute PSO analysis: 1 breakdowns in obtaining an accurate patient weight and 2 errors from misusing the value for a patient's weight e.
As the reports submitted to ECRI Institute PSO demonstrate, errors can occur when there are failures to communicate or accurately document a patient's weight.
Refer to "Table 1. One event underscores the key role of the ED in obtaining an accurate weight because the value recorded by the ED often becomes the value used throughout the patient's stay if the patient is admitted from the ED. Understandably, some patients treated in the ED are not in any condition to be weighed.
But in this particular case, the ED provider's weight estimate did not closely match the patient's actual weight. Once the patient was admitted, other providers were unaware that the weight was estimated and used the information as the patient's actual weight. Because the weight was incorrect, too little medication was given to the patient. The ED record should indicate that the weight is estimated so that the actual weight is obtained as soon as feasible. As one researcher notes, clinicians are "notoriously bad" at guessing weights.
Two other events involved children. In one case, an inaccurate estimated weight was used; as a result, the child received too much insulin, a high-alert medication known for causing serious harm if used in error.
In the other event, the wrong weight for a child was documented in the electronic record. Although health information technology can provide clinical decision support to ensure accurate dosing by alerting the clinician when the dose entered is out of range for the patient's weight, no electronic system can compensate for an inaccurately documented weight.
Incorrect entries—whether documented on paper or electronically—can be perpetuated throughout the patient's stay unless the patient is reweighed and the entry is changed with the correct weight. Despite efforts to move the United States to a metric system, Americans remain committed to inches and pounds in their daily life.
In our homes, we weigh ourselves in pounds. Many healthcare settings also obtain patient weights in pounds. Some scales can be locked to obtain weights in one unit only—preferably metric, since medication dosing is based on the metric system. Because of our propensity to think in pounds and to calculate medication doses in metric units, numerous errors occur with recording a patient's weight as kilograms even though the value obtained was in pounds.
These mistakes can lead to doubling the appropriate dose for a patient because the value of a patient's weight in pounds is more than double that amount in kilograms. Say a patient weighs lb and that amount is mistakenly recorded as kilograms. The patient's actual weight is 50 kg, or more than half the recorded weight. This type of mistake is one of the most common weight-based dosing errors reported to ECRI Institute PSO, as indicated by the number of events in this category in "Table 2.
Several of the errors with recording a patient's weight as kilograms versus pounds occurred with electronic health record EHR entries. Although some systems will alert a clinician to double-check the weight entered if the value is out of range for a patient's age or height, other systems are not designed with these alerts or allow the alert to be optional, which may result in many mistakes going undetected. If the errors are not caught, the automated dose calculation features provided with many health information technology systems will end up calculating doses based on an incorrect value.
In addition to weight, a patient's height is sometimes used to calculate dosages, particularly with younger patients and patients receiving chemotherapy.
For these patients, body surface area may be used to calculate medication doses. Just as caregivers have confused pounds and kilograms when documenting a patient's weight, so too have they confused inches and centimeters when documenting height. One event summarized in Table 2 involved an error in recording a patient's height as centimeters, even though the value was obtained in inches.
The hospital recognized that the bedside monitors deployed in its care units recorded patient height in inches in some units and in centimeters in others. Recognizing that lack of standardization for documenting height contributed to an error in titrating a medication, the hospital adopted a policy to program the bedside monitors to document height only in centimeters. Even when a correct weight is obtained, calculation errors with the patient's weight can contribute to mistakes, as occurred with one of the events summarized in Table 2.
In fact, in one study, mathematical incompetence was a significant source of error in tenfold medication dose mistakes Doherty and McDonnell. Instead of relying on mathematical calculations, clinicians should use, whenever possible, standardized order sets, which provide the medication dose for a particular drug based on patient weight ranges, to prevent dosing mistakes.
Sometimes, the clinician should not use the patient's actual weight to calculate medication dose. For example, if a patient is dehydrated, the patient's actual weight may be significantly lower than the patient's typical weight.
By subscribing you agree to the Terms of Use and Privacy Policy. Health Topics. Health Tools. Reviewed: February 26, Medically Reviewed. In addition, medications that may lose effectiveness in heavy people include:. When your doctor breaks out a prescription pad during your next visit, take a moment to ask how much thought he or she gives your dosage.
According to Consumer Reports on Health newsletter, a study presented at a American College of Emergency Physicians conference found that emergency room physicians considered body mass index less than 10 percent of the time when they prescribed certain drugs. While that number might sound alarming, Dr.
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