Interaction of Propofol and Sevoflurane on Loss of Consciousness and Movement to Skin Incision during General Anesthesia

Background: Loss of consciousness (LOC) and immobility to surgical incision seem to be mediated at different levels of the central nervous system. Pharmacologic studies of hypnotic agents have previously focused on combinations of either volatile or intravenous anesthetics. This study examined the combination of inhaled sevoflurane and intravenous propofol at these two clinically relevant anesthetic end points.

Methods: Thirty-six elective surgical patients were initially enrolled. Conditions approximating steady state were obtained for sevoflurane and target-controlled propofol infusions. Patients were sequentially evaluated for LOC (loud voice plus mild prodding) and immobility to surgical incision. The study was designed using the Dixon up-down method.

Results: The observed propofol effect target with 50% response plus sevoflurane (0.46% end-tidal concentration) was 1.2 [mu]g/ml (95% confidence interval, 1.1-1.3 [mu]g/ml). It was not significantly different from that predicted (1.5 [mu]g/ml; 95% confidence interval, 1.2-1.7 [mu]g/ml) by simple additivity. The effective plasma concentration of propofol that suppressed movement to skin incision in 50% of patients was 5.4 [mu]g/ml (95% confidence interval, 4.8-6.0 [mu]g/ml) plus sevoflurane (0.86%) and was not significantly different from that predicted by additivity (5.4 [mu]g/ml; 95% confidence interval, 4.8-5.9 [mu]g/ml). Both analyses had adequate power (90%) to detect a significant change (+/-19 to 25%) from predicted value. Repeated-measures analysis of variance identified a Bispectral Index value of 70 as the break point between those who responded at LOC or did not.     

Levobunolol compared with timolol: a four-year study.

Fifty-one patients with raised intraocular pressure (IOP) were treated for up to four years with one of three ophthalmic solutions: 0.5% levobunolol, 1% levobunolol, or 0.5% timolol. The study was conducted as a double-masked, randomised trial in which medications were administered twice daily to both eyes. Levobunolol and timolol were equally effective in reducing overall mean IOP; reductions were greater than 8.8 mmHg in all three treatment groups. The study showed levobunolol to be as safe and effective as timolol in the long-term control of raised IOP.     

Bioethics for clinicians: 5. Substitute decision-making.

Substitute decision-making is a means of making health care decisions on behalf of people who are incapable of making these decisions for themselves. It is based on the ethical principle of respect for autonomy. Substitute decision-making poses two main questions: Who-should make the decision for the incapable person, and, How should the decision be made? Because the applicable statutory and common law varies across Canada, clinicians should become familiar with the legal requirements of their own province or territory.     

Prevention of prematurity: Haguenau perinatal survey, 1971-1985

A preterm birth prevention program was instituted in France in the early 1970s. Its effectiveness has been assessed through a perinatal study in Haguenau. A relationship between prenatal care improvement and preterm birth rate decrease was noted, but a causal interpretation cannot be derived from such an observational study. However, some arguments do support this interpretation: no satisfactory alternative explanation (such as biases in pregnancy duration measurement, change in the composition of the population of pregnant women, or secular trend), a plausible causal pattern, and a dose-response relationship between prenatal care and preterm birth rate. The Haguenau study results can be applied to other French regions, but extrapolation to other countries would depend on their social, medical and cultural contexts.     

Common bile duct calculi: updated experience with dissolution with methyl tertiary butyl ether

The authors describe their experience with methyl tertiary butyl ether (MTBE) in a larger series of patients than previously reported in order to acquaint physicians with both its effectiveness for dissolution of common bile duct calculi and the limitations of its use. Ten patients with 13 biliary calculi underwent percutaneous stone dissolution treatment with the experimental cholesterol solvent, MTBE. Three stones completely dissolved within 30 minutes, seven were reduced in size, and three were visibly unaffected. All stones not completely dissolved were easily extracted by means of a stone basket except for one in a patient taken to surgery. Although MTBE perfusion is an effective technique for management of biliary calculi, practitioners should be aware that its use is quite time consuming and its odor difficult to control.     

Optimizing Cancer Radiotherapy with 2-Deoxy-D-Glucose Dose Escalation Studies in Patients with Glioblastoma Multiforme

Background and Purpose:  

Higher rates of glucose utilization and glycolysis generally correlate with poor prognosis in several types of malignant tumors. Own earlier studies on model systems demonstrated that the nonmetabolizable glucose analog 2-deoxy-D-glucose (2-DG) could enhance the efficacy of radiotherapy in a dose-dependent manner by selectively sensitizing cancer cells while protecting normal cells. Phase I/II clinical trials indicated that the combination of 2-DG, at an oral dose of 200 mg/kg body weight (BW), with large fractions of γ-radiation was well tolerated in cerebral glioma patients. Since higher 2-DG doses are expected to improve the therapeutic gain, present studies were undertaken to examine the tolerance and safety of escalating 2-DG dose during combined treatment (2-DG + radiotherapy) in glioblastoma multiforme patients.