Dose-Response Relationships - Clinical Pharmacology - MSD Manual Professional Edition
Dose-Response Relationships, p. 44 Basic Features of the Dose-Response Relationship, p. 44 Maximal Efficacy and Relative Potency, p. 44 Drug-Receptor . Dose-Response Relationships Basic Features of the Dose-Response Relationship Maximal Efficacy and Relative Potency Drug-Receptor Interactions . The nurse understands that the dose-response relationship is graded and therefore would expect to observe what? A) Once a drug is given, the response is .
Without reporting, many errors may not be known. Based on a survey of nurses on barriers to reporting, Wakefield and colleagues 62 suggested several strategies to increase the reporting of MAEs: Incident reports, retrospective chart reviews, and direct observation are methods that have been used to detect errors.
Incident reports, which capture information on recognized errors, can vary by type of unit and management activities; 73 they represent only a few of the actual medication errors, particularly when compared to a patient record review. There were two studies that compared detection methods. One of these studies of medication administration in 36 hospitals and skilled nursing facilities found errors made on 2, doses.Digoxin Nursing Considerations, Side Effects, and Mechanism of Action Pharmacology for Nurses
Direct observation was able to detect 80 percent of true administration errors, far more than detected through other means. A second study compared detection methods and found that more administration errors were detected by observation a When automated systems that use triggers are not in place, multiple approaches such as incident reports, observation, patient record reviews, and surveillance by pharmacist may be more successful.
State-based and nationally focused efforts to better determine the incidence of medication errors are also available and expanding Patient Safety and Quality Improvement Act of Research reported to date clearly reveals that medication errors are a major threat to patient safety, and that these errors can be attributed to all involved disciplines and to all stages of the medication process.
Unfortunately, the research also reveals that we have only weak knowledge of the actual incidence of errors. Our information about ADEs those detected, reported, and treated is better, but far from complete. Research Evidence—Medication Administration by Nurses The research review targeted studies involving medication administration by nurses.
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This excluded several studies that assessed medication administration errors without differentiating whether the errors were associated with physicians, assistants, or nurses. None of these studies included interventions. The incidence of MAEs was detected either formally through incident reports, chart reviews, or direct observation, or informally through anonymous surveys.
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Two studies conducted retrospective assessments, one using medical records 43 and the other malpractice claims. Eight studies assessed MAEs using direct observation of the medication administration process.
Using chart reviews, Grasso and colleagues 43 found that 4. Direct observation studies placed the estimate of total incorrect doses between 19 percent and 27 percent, 87 and when an extra review was done to separate the errors into stages of the medication process, between 6 percent and 8 percent of doses were in error because of administration. The majority of types of MAEs reported were wrong dose, wrong rate, wrong time, and omission. All of the studies reviewed here reported wrong drug and dose, but varied across the other types of MAE categories see Evidence Table 1 ; this was dependent upon the study methodology.
Of the reported contributing factors, 78 percent were due to the inexperience of the nurse. The Beyea and Hicks 8182 studies looked at errors associated with the operating room, same-day surgery, and postanesthesia; they found the majority of errors attributable to administration but did not classify them by error type. The other study reviewed 88 incident reports from a long-term care facility submitted during a month period. It found that the majority of MAEs were associated with errors involving interpreting or updating the medication administration record, delayed dose, wrong dose, or wrong drug.
Two other studies assessed the type of MAEs reported by nurses in nationwide surveys. Medication administration errors involving wrong time, omission, and wrong dose accounted for The most frequent types of medication errors were wrong time At the more advanced stage of incident reports, one study reviewed 68 malpractice cases involving MAEs in Sweden. When the nurses delegated the drug administration to subordinate staff, the majority of MAEs involved wrong drug or wrong concentration of a drug.
Errors, which were reported to the immediate supervisor, were also reported to the physician in 65 percent of cases. The reported causes of MAEs were lack of administration protocols, failure to check orders, ineffective nurse supervision when delegating administration, and inadequate documentation.
One study assessed medication errors using 31 medical records of patients discharged from a psychiatric hospital and found a total of 2, errors.
Table 1 Comparison of the Incidence of Medication Administration Errors by Type Categories The number of studies using direct observation of medication administration is increasing in response to the concern about the accuracy of other sources of data. Ten studies were found, only three of which were done in the United States. While we attempt to summarize across these studies, it is difficult to determine consistency across studies as each focused on different sets of errors some only intravenous errors, some included gastrointestinal tube technique and were conducted in different settings.
In many of the non-U. Three observational studies were conducted in pediatric units—one in France, 78 one in Switzerland, 25 and one in the United States.
Those 15 were nearly evenly divided among wrong dose, wrong time, wrong technique, and extra dose categories. Prot 78 reported nearly 50 percent more MAEs.
Of the 1, observed doses, 27 percent were in error, including wrong time; excluding wrong-time errors, the error rate was 13 percent of doses. Schneider and colleagues 25 reported an overall Common errors in addition to wrong time were wrong dose preparation and wrong administration technique. The incidence of intravenous drug errors was observed in three studies, one in England, 89 one in Germany, 90 and one in both countries.
Part of the explanation may come from institutional type of pharmacy support available and professional training factors. German nurses are not trained to do intravenous medications. Within the MAEs, most were omitted medications; the rest were evenly distributed among wrong dose, extra dose, and wrong technique. Few wrong-time errors were noted. Tissot 91 and van den Bernt 94 examined only administration stage errors and reported very different rates. It is likely that the differences in rates across these studies are due to the range of error types observed in each study as well as the varying responsibilities of nurses in the three countries.
The most extensive observation study, by Barker and colleagues, 87 conducted observations of medication administration in 36 randomly selected health care facilities acute and long-term care in two States in the United States.
Of the 3, doses observed, 19 percent contained at least one error. Nearly half of those errors were wrong-time errors. Other common types of errors included omission, wrong dose, and unauthorized unordered drug. In a much smaller study conducted in the Netherlands, Colen, Neef, and Schuring 88 found an MAE rate of 27 percent, with most of these wrong-time errors.
The rate of MAEs without wrong time was approximately 7 percent, and most of those were omissions. Information from these research studies forms a consistent picture of the most common types of MAEs. These are wrong time, omissions, and wrong dose including extra dose. Rates of error derived from direct observation studies ranged narrowly between 20 and 27 percent including wrong-time errors, and between 6 and 18 percent excluding wrong-time errors.
The alarming exception to this was the nearly 50 percent error rate in observation of intravenous medication in ICUs in Europe.
Impact of Working Conditions on Medication Errors Medication safety for patients is dependent upon systems, process, and human factors, which can vary significantly across health care settings.
A review of the literature found 34 studies that investigated some aspect of working conditions in relation to medication safety. Systems factors Systems factors that can influence medication administration include staffing levels and RN skill mix proportion of care given by RNsshift length, patient acuity, and organizational climate. There were 13 articles presenting research findings and three literature reviews.
Nurse staffing Medication administration is a key responsibility of nurses in many settings, and three studies assessed the relationship between nurse staffing, hours of nursing care in hospitals, RN skill mix, and medication errors. Two studies associated the total hours of care and the RN skill mix at a patient care unit to reported medication error rates in those units; one study used 42 units in a large Midwestern hospital 95 and the other used 39 units in 11 small hospitals.
In both studies the type of unit was controlled and the rate of reported medication errors declined as the RN skill mix increased up to an 87 percent mix.
A third study of nurses in ICUs in 10 hospitals found an inverse relationship between rates of medication errors and staffing work hours per patient day in specific settings e.
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A little over 30 percent of the variance in medication error rates resulted from the variance in staffing work hours per patient day. Three literature reviews, 303998 concluded that the direct evidence for a relationship between staffing and MAE rates was inconsistent. Workloads These findings are consistent with three studies and two literature reviews on the impact of heavy workloads, a component of nurse staffing, on errors. In one survey of nurses in 11 hospitals, both pediatric and adult nurses reported staffing ratios and the number of medications being administered as being the major reasons why medication errors occur.
Most of these errors involved nurses 64—76 percent and medication administration 59—68 percent. In all three sets of error reports, workload increases and insufficient staffing were noted to be causes of errors.
The effect of heavy workloads and inadequate numbers of nurses can also be manifested as long workdays, providing patient care beyond the point of effective performance. In a national survey by Rogers and colleagues, 99 self-reported errors by nurses found that the likelihood of a medication error increased by three times once the nurse worked more than Among nurses working more than Other findings support the importance of adequate nurse staffing and understanding the impact of shift work in decreasing medication errors.
However, there were more errors with nurses working rotating shifts. While it was not possible to determine the effect of organizational climate on violations, distress was positively associated with violations, while quality of working life, morale, and organizational climate had a negative association. The organizational climate was found to be linked with safety behavior. Higher overall safety climate was related to lower rates of medication errors and urinary tract infections.
Policies, procedures, and protocols Lack of appropriate policies, procedures, and protocols can impact medication safety, as seen in a few small studies.
In a study of malpractice cases, medication errors were associated with lack of administration protocols and ineffective nurse supervision in delegating administration.
For example, a review of two studies in the literature found that medication errors did not necessarily decrease with two nurses administering medications e. Double-checking policies are commonly used as a strategy to ensure medication safety. When errors occurred under such policies, failure to double-check doses by both pediatric and adult nurses 58 and nurses in a Veterans Affairs VA hospital were reported. However, research presented in two literature reviews offers somewhat conflicting information.
In the first review of three studies, following double-checking policies did not necessarily prevent errors. Distractions and interruptions Factors such as distractions and interruptions, during the process of delivering care can have a significant impact on medication safety. Nine studies, four with nationwide samples, and two literature reviews present information on the association between MAEs and distractions and interruptions. One survey of nurses in three hospitals in Taiwan found that they perceived distractions and interruptions as causes of errors.
These finding are furthered by research concerning self-reported errors from a nationwide sample of nurses. From a sample of 12 nurses in one hospital, one-third of progress notes were found to contain information about administered medications, yet only 30 percent of those progress notes included medication name, dose, and time of administration, and only 10 percent documented information about desired or adverse effects of medications.
Medication education, outcomes of administered medication, and assessment prior to administering were not documented in any progress note. Only half of withheld medications were documented. Communication Five studies and one literature review assessed the relationship between communication failures and medication errors. A small observational study of 12 nurses found that they communicated with other nurses about information resources on medications, how to troubleshoot equipment problems, clarification in medication orders, changes in medication regimens, and patient assessment parameters when handing over patients.
Nurses also communicated with pharmacists about information on medication administration and organizing medications for patient discharge. Another direct observational study of medication administration found opportunities for errors associated with incomplete or illegible prescriptions. When patients were transferred from across units, 85 percent of nurses reported that medication orders were rewritten at transfer, 92 percent that medication orders were checked against electronic medical records, 62 percent that it was time consuming to clarify medication orders, 66 percent that the reasons for medication changes were made at transfer, and 20 percent that blanket orders are often written as transfer orders.
The suggested explanation was that the mediations RN must administer in long-term care are those with more complexity. Another survey of RNs in 11 hospitals found that pediatric and adult nurses reported numbers of medications being administered as a major reason on why medication errors occur.
In two ICU studies, infusion pump problems were involved in 6. Monitoring and assessing An essential component of the medication process related to the administration of medications is monitoring and assessing the patient by the nurse. Only two studies provided information in this area, offering scant evidence. In the first, based on a small sample of nurses in one unit in one hospital, a qualitative analysis of observed medication administration found that participants monitored patients before, during, and after medication administration.
They also felt responsible for timing medication administration and providing as-needed e. In the second study, where ICU nurses were surveyed, no administration errors were found to be associated with inadequate monitoring or lack of patient information. These factors include characteristics of individual providers e. Four major themes emerged in the review: Effects of fatigue and sleep loss Five studies assessed the association between fatigue and sleep loss with MAE errors.
The first specifically investigated the effects of fatigue and sleep loss on errors using a national sample of nurses over a 2-week period. In this study, the rate of errors increased after working In one of these, a survey of 57 nurses, respondents reported that the majority of medication errors were attributable to fatigue.
A semistructured, qualitative interview of 40 hospital nurses prior to implementation of a bar-coding system explored the thinking processes of nurses associated with medication administration. The other study of nurses, using direct observation in a medical and surgical unit in Australia, found that participants used hypotheticodeductive reasoning to manage patient problems.
Thought process can also be distorted by distractions and interruptions. One study employed direct observation of medication administration to determine the effects of human factors on MAEs. During both the prescribing and administration of medications, the causes of errors were attributable to slips and memory lapses Another study using direct observation found causes associated with MAEs to include slips and memory lapses 40 percentrule violations 26 percentinfusion pump problems 12 percentand lack of drug knowledge 10 percent.
In one study of 40 student nurses and 6 nurses using a computerized program to assess the impact of dyslexia found that the greater the tendency towards dyslexia, the poorer the potential cognitive ability to effectively provide the skills associated with effective drug administration.
Of these reported contributing factors, 78 percent were due to the inexperience of staff. Twenty-six studies and descriptions of quality improvement projects were identified. Strategies used included recommendations from a nationwide voluntary organization to improve safety, education of nurses and other providers in safe practices, and system change and technology.
Eight types of strategies were successfully used, including documentation of allergies, nonpunitive reporting, and standardizing medication administration times. Effective leadership and appropriateness of intervention were associated with successful change implementation. The converse was associated with failure, as were unclear aims, poorly designed interventions, lack of focus on underlying system failures, unclear measures, too much focus on data collection, involvement from only some stakeholders, opposition from physicians and nurses, and conflicting time demands for team members.
The findings were limited by the lack of an analysis of the relationship between established safety policies and practices and the success of implementing new strategies, as well as the relationship between the implementation and the occurrence of ADEs. Of the recommended practices, there was high adoption of standardized labeling and storage of medications For-profit hospitals were more likely than not-for-profit hospitals to have unit-dose medication distribution systems Many medications are classified in terms of their half-lives.
For example the benzodiazepines are classified in terms of: Absorption Absorption from the site of administration permits entry of the therapeutic agent either directly or indirectly into plasma.
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Medicine-related factors include ionisation state, molecular weight, solubility, and formulation. Small, nonionised, lipid-soluble medicines permeate plasma membranes most readily.
Distribution Once absorbed, the medicine may then reversibly leave the bloodstream and distribute into the interstitial and intracellular fluids. Most medicines are protein bound to some extent; only an unbound medicine is free to carry out its pharmacological action s. Depot Storage refers to lipophilic medicines which store in fat, calcium-binding drugs, etc. This can result in changes in the volume of distribution Vdfor some medicines causing unpredictable effects, particularly in frail older people.
The volume of distribution is the extent to which a medicine distributes out of the bloodstream and into the tissues of the body i. A decrease in Vd will result in higher plasma concentrations for hydrophilic medicines such as gentamicin, digoxin and lithium. A higher proportion of body fat will increase Vd for lipophilic medicines such as diazepam causing an increase in plasma half-life. Metabolism Before being excreted, the medicine is metabolised by the liver, kidney or other sites.
It refers to the process of making the drug more polar more water-solublewhich may lead to medicine inactivation and excretion. Metabolites may be more or less prodrug active than the parent medicine. The liver is the major source of these enzymes P enzymesthough they may be present in the gastrointestinal tract, heart, lung, brain and kidney.
Phase I Reactions nonsynthetic Phase I reactions nonsynthetic involve minor structural modifications of the parent structure via oxidation, reduction or hydrolysis to produce smaller, more water-soluble metabolite. These are predominantly handled by enzymes known as the Cytochrom P enzymes.
The most common causes of medicine-to-medicine interactions are pharmacokinetics, particularly metabolic ones. These are known as the cytochrome P interactions. A large number of clinically important interactions arise from inhibition or induction of substrates medicines that are significantly metabolised by the given enzymes.