Prolonged sedation due to an accumulation of midazolam in an intensive care patient with hypothyroidism

The Impact of Suboptimal 25-Hydroxyvitamin D Levels and Cholecalciferol Replacement on the Pharmacokinetics of Oral Midazolam in Control Subjects and Patients With Chronic Kidney Disease

The aim of this study was to investigate the impact of suboptimal 25-hydroxyvitamin D (25-VitD) and cholecalciferol (VitD3 ) supplementation on the pharmacokinetics of oral midazolam (MDZ) in control subjects and subjects with chronic kidney disease (CKD). Subjects with CKD (n = 14) and controls (n = 5) with suboptimal 25-VitD levels (<30 ng/mL) were enrolled in a 2-phase study. In phase 1 (suboptimal), subjects were administered a single oral dose of VitD3 (5000 IU) and MDZ (2 mg). In phase 2 (replete) subjects who achieved 25-VitD repletion after receiving up to 16 weeks of daily cholecalciferol were given the identical single oral doses of VitD3 and MDZ as in phase 1. Concentrations of MDZ and metabolites, 1'-hydroxymidazolam (1'-OHMDZ), and 1'-OHMDZ glucuronide (1'-OHMDZ-G) were measured by liquid chromatography-tandem mass spectrometry and pharmacokinetic analysis was performed. Under suboptimal 25-VitD, reductions in MDZ clearance and renal clearance of 47% and 87%, respectively, and a 72% reduction in renal clearance of 1'-OHMDZ-G were observed in CKD vs controls. In phase 1 versus phase 2, MDZ clearance increased in all control subjects, with a median (interquartile range) increase of 10.5 (0.62-16.7) L/h. No changes in MDZ pharmacokinetics were observed in subjects with CKD between phases 1 and 2. The effects of 25-VitD repletion on MDZ disposition was largely observed in subjects without kidney disease. Impaired MDZ metabolism and/or excretion alterations due to CKD in a suboptimal 25-VitD state may not be reversed by cholecalciferol therapy. Suboptimal 25-VitD may augment the reductions in MDZ and 1'-OHMDZ-G clearance values observed in patients with CKD.

Hemodynamic Stability in Medically Treated Hypothyroid Patients Undergoing Intravenous Sedation

PURPOSE

To evaluate the hemodynamic stability of medically treated hypothyroid patients undergoing intravenous sedation for dentoalveolar surgery.

PATIENTS AND METHODS

A retrospective chart analysis of 20 consecutive white male patients actively being treated for hypothyroidism undergoing intravenous sedation for dentoalveolar surgery. Twenty consecutive normothyroid white male patients undergoing intravenous sedation for dentoalveolar surgery were used as controls. Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), pulse pressure (PP), peripheral oxygen saturation (S(p)O(2)) and pulse were recorded at 5-minute intervals during intravenous sedation.

RESULTS

Statistically significant lower average hemodynamic values were seen in hypothyroid patients compared to normothyroid patients in SBP (P = .05) and PP (P = .003). There were highly significant baseline changes for hypothyroid patients in DBP (P < .001) and MAP (P < .001) and significant baseline changes for normothyroid patients in DBP (P = .03), PP (P = .02) and pulse (P = .03). All changes were maintained within +/- 10% of baseline (range, -8.9% to +9.6%).

CONCLUSIONS

Intravenous sedation for dentoalveolar surgery in medically treated hypothyroid patients maintains hemodynamic stability.

Midazolam Therapeutic Drug Monitoring in Intensive Care Sedation

During a 5-year period, 1997 to 2002, therapeutic drug monitoring of midazolam plasma concentrations in combination with the level of sedation as assessed by the Ramsay sedation scale was performed in 648 critically ill patients requiring artificial ventilation. In a subgroup of 189 patients sepsis-related organ failure assessment procedure was additionally performed. A total number of 3354 samples were analyzed. Significantly reduced clearance of midazolam was observed within the first 4 days of midazolam treatment of critically ill patients. As a result, accumulation of midazolam and its metabolites occurred within the first week of treatment. In contrast, parameters such as serum bilirubin or creatinine, which are commonly used to adapt drug therapy to organ dysfunction, showed significant changes with a delay of more than 10 days as compared with the findings of midazolam monitoring. Midazolam plasma concentrations showed a good correlation with the sedative capacity of the drug (r2 = 0.906). However, a great variability of the drug effect between patients could be demonstrated, which, as a consequence, may complicate the development of dosing strategies based on midazolam plasma concentrations to better control sedation in critically ill patients. Furthermore, patient age seems to be an important factor for the considerable variability of the sedative effect of midazolam. To achieve a certain levels of sedation, significantly lower midazolam infusion rates as well as plasma concentrations were required as the patients age increased. No significant sex-related differences could be observed for any pharmacologic parameter obtained in this study. Our findings suggest that midazolam therapeutic drug monitoring might be a useful tool to individualize midazolam therapy, especially in critically ill patients developing organ dysfunction and requiring long-term sedation to minimize the risk of drug accumulation and excessive sedation.

Hypothyroidism

Hypothyroidism is common, potentially serious, often clinically overlooked, readily diagnosed by laboratory testing, and eminently treatable. The condition is particularly prevalent in older women, in whom autoimmune thyroiditis is common. Other important causes include congenital thyroid disorders, previous thyroid surgery and irradiation, drugs such as lithium carbonate and amiodarone, and pituitary and hypothalamic disorders. Worldwide, dietary iodine deficiency remains an important cause. Hypothyroidism can present with nonspecific constitutional and neuropsychiatric complaints, or with hypercholesterolaemia, hyponatraemia, hyperprolactinaemia, or hyperhomocysteinaemia. Severe untreated hypothyroidism can lead to heart failure, psychosis, and coma. Although these manifestations are neither specific nor sensitive, the diagnosis is confirmed or excluded by measurements of serum thyrotropin and free thyroxine. Thyroxine replacement therapy is highly effective and safe, but suboptimal dosing is common in clinical practice. Patient noncompliance, drug interactions, and pregnancy can lead to inadequate treatment. Iatrogenic thyrotoxicosis can cause symptoms, and, even when mild, provoke atrial fibrillation and osteoporosis. We summarise present understanding of the history, epidemiology, pathophysiology, and clinical diagnosis and management of hypothyroidism.