Cation metabolism during propofol sedation with and without EDTA in patients with impaired renal function

Massive Transfusion Increases Serum Magnesium Concentration

(1) Background: The massive transfusion of packed red blood cells (RBCs) is a lifesaving procedure, but it is associated with complications, e.g., dysmagnesemia. Since magnesium is an intracellular ion, the transfused RBCs can significantly influence the magnesium concentration in the recipient's blood. (2) Methods: A retrospective study was performed among 49 patients hospitalized in the Central Clinical Hospital of the Medical University of Warsaw who received a massive blood transfusion (≥4 units/h). Data on laboratory results and patient history were collected from the hospital database. The intracellular RBCs magnesium concentration was measured in 231 samples using the colorimetric method. (3) Results: There were statistically significant changes in the mean serum magnesium concentration preoperatively and 24 h postoperatively (0.87 ± 0.13 vs. 1.03 ± 0.14, p < 0.00001) and 48 h postoperatively (0.87 ± 0.13 vs. 1.06 ± 0.15, p < 0.00001). Patients who died had significantly higher serum magnesium concentrations (p < 0.05). The median intracellular magnesium concentration in RBCs was 0.91 (0.55-1.8) mmol/L, which is below the reference values of 1.65-2.65 mmol/L. (4) Conclusions: Transfused RBCs significantly increased the serum magnesium concentration 24 h and 48 h postoperatively. It could be a result of mild hemolysis, as the median intracellular magnesium concentration in RBCs was below the reference values.

New medications and techniques in ambulatory anesthesia

Novel anesthetic and analgesic agents are currently under development or investigation to improve anesthetic delivery and patient care. The pharmacokinetic and analgesic profiles of these agents are especially tailored to meet the challenges of rapid recovery and opioid minimization associated with ambulatory anesthesia practice.

Sedation for critically ill or injured adults in the intensive care unit: a shifting paradigm

As most critically ill or injured patients will require some degree of sedation, the goal of this paper was to comprehensively review the literature associated with use of sedative agents in the intensive care unit (ICU). The first and selected latter portions of this article present a narrative overview of the shifting paradigm in ICU sedation practices, indications for uninterrupted or prolonged ICU sedation, and the pharmacology of sedative agents. In the second portion, we conducted a structured, although not entirely systematic, review of the available evidence associated with use of alternative sedative agents in critically ill or injured adults. Data sources for this review were derived by searching OVID MEDLINE and PubMed from their first available date until May 2012 for relevant randomized controlled trials (RCTs), systematic reviews and/or meta-analyses and economic evaluations. Advances in the technology of mechanical ventilation have permitted clinicians to limit the use of sedation among the critically ill through daily sedative interruptions or other means. These practices have been reported to result in improved mortality, a decreased length of ICU and hospital stay and a lower risk of drug-associated delirium. However, in some cases, prolonged or uninterrupted sedation may still be indicated, such as when patients develop intracranial hypertension following traumatic brain injury. The pharmacokinetics of sedative agents have clinical importance and may be altered by critical illness or injury, co-morbid conditions and/or drug-drug interactions. Although use of validated sedation scales to monitor depth of sedation is likely to reduce adverse events, they have no utility for patients receiving neuromuscular receptor blocking agents. Depth of sedation monitoring devices such as the Bispectral Index (BIS©) also have limitations. Among existing RCTs, no sedative agent has been reported to improve the risk of mortality among the critically ill or injured. Moreover, although propofol may be associated with a shorter time to tracheal extubation and recovery from sedation than midazolam, the risk of hypertriglyceridaemia and hypotension is higher with propofol. Despite dexmedetomidine being linked with a lower risk of drug-associated delirium than alternative sedative agents, this drug increases risk of bradycardia and hypotension. Among adults with severe traumatic brain injury, there are insufficient data to suggest that any single sedative agent decreases the risk of subsequent poor neurological outcomes or mortality. The lack of examination of confounders, including the type of healthcare system in which the investigation was conducted, is a major limitation of existing pharmacoeconomic analyses, which likely limits generalizability of their results.

Effects of propofol on intraoperative parathyroid hormone monitoring in patients with primary hyperparathyroidism undergoing parathyroidectomy: a randomized control trial

PURPOSE

Serial measurements of parathyroid hormone (PTH) serum concentrations aid parathyroidectomy surgery. There are concerns that propofol may increase PTH concentrations and/or interfere with PTH assays. The primary purpose of this study is to determine the effects of propofol on PTH concentrations in patients with primary hyperparathyroidism and to determine its effect on PTH assays.

METHODS

Thirty patients with primary hyperparathyroidism were assigned randomly to induction and maintenance with either propofol or sevoflurane. Blood samples for PTH assays were obtained pre-induction, immediately after induction, ten minutes after induction, and after excision of parathyroid adenoma. The primary endpoint was the PTH concentration at ten minutes after induction. This endpoint was compared between groups using analysis of covariance adjusting for pre-induction PTH. An in vitro study was performed with four different pools of PTH concentrations that were spiked with increasing concentrations of propofol. Serum PTH was measured in duplicate in each sample and analyzed using repeated measures analysis of variance.

RESULTS

At ten minutes after induction, PTH concentrations did not differ significantly between groups (least square mean difference -7.0 pg·mL(-1); 95% confidence interval, -34.2 to +20.2). The PTH level in vitro did not change significantly with increasing propofol concentrations.

DISCUSSION

Parathyroid hormone concentrations in patients with primary hyperparathyroidism were not affected by the type of anesthesia (propofol vs sevoflurane). Furthermore, propofol was found not to interfere with PTH assays at clinically relevant concentrations. There is no evidence to support the avoidance of a propofol anesthetic for parathyroid surgery.

[Agents for sedation and analgesia in the intensive care unit]

Sedation-analgesia for critically ill patients is usually performed with the combination of a sedative agent and an opioid. Midazolam and propofol are the agents most commonly used for sedation in ICU. The quality of the sedation is quite comparable with both agents, but pharmacokinetic properties of propofol allow a more rapid weaning process from mechanical ventilation. However, implementation of algorithms to adjust drug dosages reduces ventilator days and limits the kinetic differences between propofol and midazolam. Among the adverse events associated with propofol, propofol infusion syndrome is a rare but lethal aspect of propofol therapy. Opioids are the mainstay of analgesic therapy. They interact synergistically with hypnotics. Sufentanil, fentanyl and morphine are the most frequently used opioids. Remifentanil is an ultrashort acting opiate that does not appear to accumulate with prolonged use. The advent of remifentanil has allowed the use of analgesia-based sedation.

Does propofol anesthesia affect intraoperative parathyroid hormone levels? A randomized, prospective trial

BACKGROUND

Intravenous propofol (2,6-diisopropylphenol) infusion is used commonly for sedation/anesthesia during operations. Several authors have reported that propofol can interfere with intact parathyroid hormone (PTH) testing in vitro. Therefore, many surgeons avoid propofol during parathyroidectomy.

METHODS

To determine whether propofol affects intraoperative PTH levels in vivo, we randomly assigned 34 patients (80% power; alpha < .05) with secondary hyperparathyroidism to undergo surgery for dialysis access. Patients were assigned randomly to local anesthesia with either propofol (n = 17 patients) or midazolam (n = 17 patients) sedation. PTH values were obtained before the procedure and at 10 minutes and 30 minutes after the start of the propofol or midazolam.

RESULTS

Median preoperative serum PTH and calcium levels were 175 pg/mL (range, 27-2646 pg/mL) and 9.2 mg/dL (range, 8.1-10.8 mg/dL), respectively. There was no statistically significant difference between the PTH levels in the 2 groups at each of our time points. There was also no difference in the percentage of change from baseline in the PTH values between our 2 groups. No patient in either group had a sustained drop in their PTH level of greater than 50%.

CONCLUSIONS

Intravenous propofol infusion does not alter PTH levels significantly during the operation. Therefore, we believe the intraoperative PTH assay can be used safely during propofol sedation when parathyroid surgical procedures are being performed.