Patient perceptions of participation in emergency medicine research projects.

OBJECTIVE: To determine if ED research reflects patient expectations. METHOD: A cross-sectional ED patient survey. RESULTS: Three hundred and nine (98.1%, 95% confidence interval [CI] 95.7-99.2) of 315 patients believed that ED research was important. Two hundred and twelve (68.4%, 95% CI 62.9-73.5) would welcome involvement, only 26 (8.4%, 95% CI 5.7-12.3) felt pressured to do so. Two hundred and thirty-one (75.7%, 95% CI 70.5-80.4) and 279 (91.5%, 95% CI 87.6-94.3) believed consent was necessary for observational and experimental studies, respectively. One hundred and one (32.4%, 95% CI 27.3-37.9) disagreed with medical records being accessed without consent. CONCLUSION: Patient expectations are not always consistent with current practice. The expectation of consent prior to record access is worthy of further consideration.

Utility of calcium, magnesium and phosphate testing in the emergency department.

OBJECTIVE: To determine how frequently calcium (Ca), magnesium (Mg) and phosphate (PO4 ) tests change ED patient management. METHODS: We undertook a retrospective observational study in an Australian tertiary referral ED. We enrolled adult patients (aged ≥18 years) who presented between 1 January and 30 June 2017 and who had a serum Ca, Mg or PO4 test ordered and completed during their ED stay. Patient symptoms, medical history, electrolyte levels and ED management changes were extracted from the electronic medical record. RESULTS: Of the 33 120 adults presented during the study period, 1716 (5.2%, 95% confidence interval [CI] 5.0-5.4) had at least one Ca, Mg or PO4 test completed in the ED. This included 4776 individual electrolyte tests, of which 776 (16.2%, 95% CI 15.2-17.3) were abnormal. Fifty-six (7.2% [95% CI 5.5-9.3] of patients with abnormal tests, 1.2% [95% CI 0.9-1.5] of all tests) tests were associated with a change in ED management. Twenty-six out of 1683 (1.5%) Ca levels were low with six (23.1%) management changes; 203 (12.1%) were high with 10 (4.9%) management changes. One hundred and twenty-eight out of 1579 (8.1%) Mg levels were low with 33 (25.8%) management changes; 30 (1.9%) were high with no management changes. Two hundred and twenty-five out of 1514 (14.9%) PO4 levels were low with six (2.7%) management changes; 164 (10.8%) were high with one (0.6%) management change. Fifty (2.9%) patients had management changes despite normal electrolyte levels. CONCLUSION: Ca, Mg and PO4 testing is common. However, the yield of clinically significant abnormal levels is low and patient management is rarely changed. Testing of these electrolytes needs to be rationalised.

Risk variables associated with abnormal calcium, magnesium and phosphate levels among emergency department patients.

OBJECTIVE: The utility of calcium, magnesium and phosphate measurement in the ED is limited. We aimed to determine clinical risk variables for abnormal levels of these electrolytes in order to inform the development of an ordering guideline. METHODS: We performed a retrospective, observational study of patients who presented to a tertiary referral ED between January and June 2017. Adult patients who had serum calcium, magnesium or phosphate tests completed during their ED stay were included. Presenting symptoms and signs, comorbidities, medication use and laboratory values were extracted from the medical record. Patients with missing data items were excluded. Logistic regression models determined clinical risk variables associated with low and high levels of each electrolyte. RESULTS: A total of 33 120 adults presented during the study period. Of the 1679 calcium, 1576 magnesium and 1511 phosphate tests, 228 (13.6%), 158 (10.0%) and 387 (25.6%) were abnormal, respectively. Significant risk variables (P < 0.05) for abnormal levels were: hypocalcaemia - vomiting, perioral numbness, hand/foot spasm, calcium and phosphate supplements and chemotherapy (odds ratio [OR] range 5.9-17.3); hypercalcaemia - female sex, vomiting, polyuria, confusion, hyperparathyroidism, cancer and type 1 diabetes (OR range 2.3-9.7); hypomagnesemia - female sex, proton pump inhibitor use, tacrolimus use, alcohol abuse and type 2 diabetes (OR range 2.2-13.1); hypermagnesemia - lethargy, thiazide use and chronic kidney disease (OR range 4.3-4.5); hypophosphatemia - nausea, seizure and glucocorticoid use (OR range 1.7-2.1); and hyperphosphataemia - polyuria, diuretics and chronic kidney disease (OR range 1.9-5.0). CONCLUSION: A range of demographic, comorbid, medication and clinical variables are associated with abnormal calcium, magnesium and phosphate levels. These findings will inform the development of clinical guidelines to rationalise calcium, magnesium and phosphate testing. Justification may be required for testing patients with no risk variables.

The Differential Binding of Antipsychotic Drugs to the ABC Transporter P-Glycoprotein Predicts Cannabinoid-Antipsychotic Drug Interactions.

Cannabis use increases rates of psychotic relapse and treatment failure in schizophrenia patients. Clinical studies suggest that cannabis use reduces the efficacy of antipsychotic drugs, but there has been no direct demonstration of this in a controlled study. The present study demonstrates that exposure to the principal phytocannabinoid, Δ9-tetrahydrocannabinol (THC), reverses the neurobehavioral effects of the antipsychotic drug risperidone in mice. THC exposure did not influence D2 and 5-HT2A receptor binding, the major targets of antipsychotic action, but it lowered the brain concentrations of risperidone and its active metabolite, 9-hydroxy risperidone. As risperidone and its active metabolite are excellent substrates of the ABC transporter P-glycoprotein (P-gp), we hypothesized that THC might increase P-gp expression at the blood-brain barrier (BBB) and thus enhance efflux of risperidone and its metabolite from brain tissue. We confirmed that the brain disposition of risperidone and 9-hydroxy risperidone is strongly influenced by P-gp, as P-gp knockout mice displayed greater brain concentrations of these drugs than wild-type mice. Furthermore, we demonstrated that THC exposure increased P-gp expression in various brain regions important to risperidone's antipsychotic action. We then showed that THC exposure did not influence the neurobehavioral effects of clozapine. Clozapine shares a very similar antipsychotic mode of action to risperidone, but unlike risperidone is not a P-gp substrate. Our results imply that clozapine or non-P-gp substrate antipsychotic drugs may be better first-line treatments for schizophrenia patients with a history of cannabis use.