Edge Bleeding Artifact Reduction for Shape from Focus in Microscopic 3D Sensing

Shape from focus enables microscopic 3D sensing by combining it with a microscope system. However, edge bleeding artifacts of estimated depth easily occur in this environment. Therefore, this study analyzed artifacts and proposed a method to reduce edge bleeding artifacts. As a result of the analysis, the artifact factors are the depth of field of the lens, object texture, brightness difference between layers, and the slope of the object. Additionally, to reduce artifacts, a weighted focus measure value method was proposed based on the asymmetry of local brightness in artifacts. The proposed reduction method was evaluated through simulation and implementation. Edge bleeding artifact reduction rates of up to 60% were shown in various focus measure operators. The proposed method can be used with postprocessing algorithms and reduces edge bleeding artifacts.

Waist circumference and the risk of lumbar and femur fractures: a nationwide population-based cohort study

Although obesity is known to have an influence on fracture, the relationship between lumbar and femur fractures and weight or waist circumference is controversial. We investigated the incidence of fracture with regards to waist circumference using the customised database of the Korean National Health Insurance Service (NHIS). Among 8,922,940 adults who participated at least twice in the NHIS National Health Check-up Program in South Korea between 2009 and 2011, 1,556,751 subjects (780,074 men and 776,677 women) were extracted. Over a mean follow-up of 6.5 years, multivariate-adjusted logistic regression analysis demonstrated that higher waist circumference was associated with an increased risk of femur fractures in both males and females. Moreover, the incidence of lumbar fractures was also positively associated with an increased waist circumference in males and females. An increased waist circumference showed a positive linear relationship with the risk of lumbar and femur fractures in both males and females.

Humidification of inspired gases during mechanical ventilation

Humidification of inspired gas is mandatory for all mechanically ventilated patients to prevent secretion retention, tracheal tube blockage and adverse changes occurring to the respiratory tract epithelium. However, the debate over "ideal" humidification continues. Several devices are available that include active and passive heat and moisture exchangers and hot water humidifiers Each have their advantages and disadvantages in mechanically ventilated patients. This review explores each device in turn and defines their role in clinical practice.

Predicting response to recombinant factor VIIa in non-haemophiliac patients with severe haemorrhage

BACKGROUND

Despite increasing use of recombinant factor VIIa (rFVIIa) in non-haemophiliac patients, it is unclear when rFVIIa might be effective.

METHODS

A single centre review of consecutive non-haemophiliac patients receiving rFVIIa for the management of severe haemorrhage. Treatments with rFVIIa were at a dose of 90 mug kg(-1) repeated at three hourly intervals at the clinicians' discretion.

RESULTS

Eighteen patients received rFVIIa. Six patients survived to discharge and 12 patients died in hospital. The median (range) Sequential Organ Failure Assessment (SOFA) score at the time of administration of rFVIIa for the group that survived was 8.0 (5-12) compared with the group that died 12.0 (7.0-14.0) (P=0.03). One of the patients who survived (17%) had organ failure at the time of rFVIIa administration compared with 11 of those who died (92%) (P=0.004). Fifteen patients survived long enough to consider a second dose of rFVIIa, one patient who survived to discharge needed more than one dose (1/6, 17%), compared with seven of those who later died in hospital (7/9, 78%) (P=0.04). The survivors had a significant reduction in blood product requirements after rFVIIa, while patients who died did not. Neither the prothrombin time nor the activated partial thromboplastin time before or after rFVIIa predicted survival.

CONCLUSIONS

High SOFA score and failure to respond to one adequate dose of rFVIIa appear to identify patients with poor prognosis. These observations may help in determining when rFVIIa treatment is likely to be futile.

Who to report to the coroner? A survey of intensive care unit directors and Her Majesty's Coroners in England and Wales

We performed a postal survey to assess the ability of intensive care unit directors and Her Majesty's Coroners to recognise deaths that should be reported to the local coroner. The survey questionnaire consisted of 12 hypothetical case scenarios. Coroners were significantly better at identifying reportable deaths than intensive care unit directors (median correct recognition scores of 11 (interquartile range 9.25-11) vs. 8 (interquartile range 7-10), respectively, p < 0.01). Deaths associated with an accident, medical treatments, industrial disease, neglect and substance abuse were significantly under-reported by intensive care unit directors (p < 0.01). Results show that significant numbers of deaths on intensive care units in England and Wales may not be being referred for further investigation, and that wide variation in local coroners' practices exists. Improvements in postgraduate medicolegal education about deaths reportable to a coroner are required. National regulations need to be more detailed and standardised so that regional variation is eliminated.

Brain stem death and organ donation—11 years on

BACKGROUND

We studied previously patterns of organ donation in a teaching hospital. Eleven years later we repeated the study to investigate how patterns had changed. We also wanted to see whether non-heart beating donation was being practised in our intensive care units.

METHODS

All deaths were prospectively audited to identify potential heart beating and non-heart beating organ donors. The actual organ donors and reasons for not donating were identified.

RESULTS

Overall, there was a significant reduction in the number of potential organ donors in the 11-yr period. This was accompanied by an increase in refusal rates by relatives from 10 to 29%, and a decrease in refusal rates by the coroner from 28 to 11%.

CONCLUSIONS

In this hospital the number of potential and actual organ donors has fallen in 11 yr. This is a combination of decreasing numbers of patients becoming brain dead and increased relative refusal rate. It has only been partially offset by a more liberal attitude of the coroner and non-heart beating donors.

Sexual hallucinations during and after sedation and anaesthesia

Sexual hallucinations have been reported since the introduction of chloroform. Newer agents such as midazolam and propofol appear particularly prone to producing them. Some practitioners have been the victims of allegations resulting from the hallucinogenic effects of these drugs. Other individuals, including doctors, have used the amnesic effects of midazolam and other drugs to sexually assault victims. Clinicians should be aware of the risks to which they may inadvertently expose themselves if these drugs are not used carefully.

Reducing the demand for admission to intensive care after major abdominal surgery by a change in anaesthetic practice and the use of remifentanil

We have used a remifentanil-based anaesthetic for patients undergoing major abdominal surgery who would normally have gone to the intensive care unit in this hospital. Avoiding intensive care unit admission was considered an advantage as a shortage of intensive care unit beds was leading to the cancellation of operations. We first used remifentanil as part of a safety and efficacy study. The aim was to see if the rapid and complete awakening obtained when using this drug would allow us to avoid the need for admission to an intensive care unit and use a high dependency unit instead. This was shown to be practicable. In comparison with a group of patients matched retrospectively for the type of operation before remifentanil was used there was a reduction in the length of time (mean+/- SD) patients' lungs were ventilated (612+/-417 vs. 9.9+/-28.9 min P< 0.0001). There was no saving in cost ( pound808.71+/- pound187.06 vs. pound795.27+/- pound253.49). When remifentanil was used routinely (after the safety and efficacy study), there were significant reductions in the time to tracheal extubation (612+/-417 vs. 4+/-10 min P < 0.0001) and costs (808.71I vs. 392.10 I P < 0.0001) compared with other patients in whom it was not used. Patients waiting for a liver transplant were also being cancelled when a donor organ became available because of the shortage of intensive care unit beds. Based on our other experience with remifentanil, we used a similar anaesthetic technique for these patients. It proved possible to extubate the trachea in 12 of 15 patients at the end of the operation. No patient needed re-intubation. The need for intensive care and therefore cancellation of surgery was reduced. In contrast, only one patient's trachea was extubated immediately after surgery in the group of patients anaesthetized before the introduction of remifentanil. A remifentanil-based technique in combination with a change in organization has therefore enabled us to avoid admission to the intensive care unit for these patients.

Debate: Albumin administration should be avoided in the critically ill

The benefit of albumin administration in the critically ill patient is unproven. Epidemiological evidence suggests that there is an increase in death among patients with burns, hypoalbuminaemia, and hypotension treated with human albumin solution (HAS). In critical illness, hypoalbuminaemia is a result of transcapillary leak, decreased synthesis, large volume body fluid losses, and dilution caused by fluid resuscitation. When treating patients with hypoalbuminaemia, efforts must be centred around correction of the underlying disorder rather than reversal of hypoalbuminaemia. Problems with using albumin arise because it is an expensive blood product, and can result in systemic changes that include cardiovascular, haematological, renal, pulmonary, and immunological effects.

The effect of oxygen on propofol-induced inhibition of microsomal cytochrome P450 3A4

We have shown previously that both hypoxia and propofol may inhibit the metabolism of midazolam. We now wished to see whether there was any additive or synergistic effect when they occurred together. Microsomes were incubated with 20 microns midazolam for 60 min, and propofol 0, 50, 100 or 1000 microM was added. Incubates were further subdivided so that the environment contained 0, 10, 21 or 70% oxygen. The results confirmed our earlier study showing that propofol only had a significant inhibitory effect at a concentration greater than that seen clinically (1000 microM). Anoxia was the only environment in which significant depression of the metabolism of midazolam occurred at all concentrations of propofol. This reduced it to almost zero. Post hoc analysis of the data showed that, with the greatest concentration of propofol (1000 microM), there was increasing inhibition of metabolism of midazolam with increases of oxygen from 10 to 70%.

Utility of hepatocytes to model species differences in the metabolism of loxtidine and to predict pharmacokinetic parameters in rat, dog and man

1. The metabolism of loxtidine (1-methyl-5-[3-[3-[(1-piperidinyl) methyl] phenoxy] propyl] amino-1H-1,2,4-triazole-3-methanol) was studied in freshly isolated rat, dog and human hepatocytes. Metabolism in vitro was comparable with previously available in vivo data in all three species with the marked species differences observed in vivo being reproduced in the hepatocyte model. 2. The major route for the metabolism of loxtidine by rat hepatocytes was N-dealkylation to form the propionic acid and hydroxymethyl triazole metabolites. A minor metabolic route was the oxidation of loxtidine to a carboxylic acid metabolite. The major route of metabolism for loxtidine in dog hepatocytes was glucuronidation with oxidation to the carboxylic acid metabolite being of minor importance. Incubation of loxtidine with human hepatocytes resulted in the drug remaining largely unchanged but with the carboxylic acid metabolite being produced in minor amounts. 3. In vitro studies were undertaken with rat, dog and human hepatocytes to determine the Michaelis-Menten parameters Vmax and Km for the sum of all the metabolic pathways. These kinetic parameters were used to calculate the intrinsic clearance of loxtidine. Using appropriate scaling factors, the predicted in vivo hepatic clearance was then calculated. The predicted intrinsic clearances were 51.4 +/- 12.4, 8.0 +/- 0.8 and 1.0 +/- 0.6 ml/min/kg for rat, dog and human hepatocytes respectively. These data were then used to calculate hepatic clearances of 24.5, 3.1 and 0.2 ml/min/kg for rat, dog and man respectively. 4. In vivo hepatic and intrinsic clearances for loxtidine were determined in rat, dog and human volunteers. The hepatic clearances of loxtidine were 26.6, 6.6 and 0.4 ml/min/kg in rat, dog and man respectively and intrinsic clearances were 58.5, 18.6 and 2.0 ml/min/kg in rat, dog and man respectively. 5. The present studies demonstrate that the hepatocyte model may be a valuable in vitro tool for predicting both qualitative and quantitative aspects of the metabolism of a drug in animals and man at an early stage of the drug development process.

Sedation and analgesia

Sedation is a process of soothing. The concept of the ideal level of sedation is controversial and has changed over the last decade. A shift from deep sedation, often enhanced by muscle relaxants that completely detaches the patient from their environment, to light sedation rendering the patient sleepy but easily arousable has been widely accepted. This change in attitude has been brought about by sophisticated modes of ventilation allowing the ventilator to synchronize with the patient's own breathing pattern. In addition, the increasingly recognised adverse effects of over-sedation have contributed to the reduction in the depth of sedation.

Metabolism of remifentanil during liver transplantation

We have investigated the pharmacokinetics of remifentanil and its less potent metabolite, GR90291, in six adult patients undergoing orthotopic liver transplantation (OLT). A single bolus infusion of remifentanil 10 micrograms kg-1 min-1 was given at the beginning of the dissection and anhepatic phases of OLT. Remifentanil and GR90291 concentrations were measured in subsequent serial arterial and mixed venous blood samples. Mean arterial clearance of remifentanil was significantly greater (P = 0.02) in the dissection phase (79.54 ml min-1 kg-1) than in the anhepatic phase (39.57 ml min-1 kg-1). Steady state volumes of distribution were not significantly different. Clearance of remifentanil during the anhepatic phase was similar to that of healthy adult patients. Mean maximum concentration (Cpmax) of GR90291 was lower in the dissection phase than in the anhepatic phase (P = 0.026). There was no significant pulmonary metabolism of remifentanil.

Serum albumin and colloid osmotic pressure in survivors and nonsurvivors of prolonged critical illness

We retrospectively compared the changes in serum albumin concentration and colloid osmotic pressure between survivors and nonsurvivors of prolonged (> or = 7 days) critical illness over a 2-year period from 1 July 1995. All patients had serum albumin measured daily, and colloid osmotic pressure measured 5 days a week, throughout their ICU admission. They received crystalloid and colloid infusions as well as parenteral or enteral feeding. Infusions of albumin were not used to treat hypoalbuminaemia. One hundred and forty-five patients were included, 66 nonsurvivors and 79 survivors. Nonsurvivors were significantly older than survivors [mean (95% CI): 58 (3.8) and 49 (4.1) years, respectively] and had a greater risk of death [mean (95% CI): 0.44 (0.06) and 0.28 (0.05); p < 0.05]. There was no significant difference in gender, APACHE II score [mean (95% CI): 22 (2.7) (nonsurvivors); 18 (2.3) (survivors)] or length of stay [median (interquartile range): 14 (9-27) days (nonsurvivors); 15 (9-26) days (survivors)]. There was no difference between the two groups in the absolute minimum serum albumin concentrations reached, the time to reach that minimum or the minimum in the first 7 days. However, nonsurvivors had a significantly lower mean serum albumin concentration: [mean (95% CI): 15.7 (5.1) g.l-1 compared with 18.3 (4.6) g.l-1 in survivors; p < 0.05]. They also had a lower recovery mean (the weighted mean after the minimum value): [mean (95% CI): 13.3 (5.1) g.l-1 (nonsurvivors) and 18.6 (5.3) g.l-1 (survivors); p < 0.01]. Analysis of colloid osmotic pressure results showed no difference between the groups in mean, minimum or recovery mean. Regression analysis of mean colloid osmotic pressure and albumin revealed that albumin only contributed 17% of the colloid osmotic pressure in these patients. The similar decrease in albumin in nonsurvivors and survivors may reflect the acute inflammatory response and/or haemodilution. However, survivors showed an ability to increase serum albumin concentrations, possibly owing to resumption of synthesis. The colloid osmotic pressure varied little between or within either group of patients, possibly because of the use of artificial colloids. There was no relationship between death and colloid osmotic pressure.

Treatment of compulsive behaviour in eating disorders with intermittent ketamine infusions

We have previously shown that eating disorders are a compulsive behaviour disease, characterized by frequent recall of anorexic thoughts. Evidence suggests that memory is a neocortical neuronal network, excitation of which involves the hippocampus, with recall occurring by re-excitement of the same specific network. Excitement of the hippocampus by glutamate-NMDA receptors, leading to long-term potentiation (LTP), can be blocked by ketamine. Continuous block of LTP prevents new memory formation but does not affect previous memories. Opioid antagonists prevent loss of consciousness with ketamine but do not prevent the block of LTP. We used infusions of 20 mg per hour ketamine for 10 h with 20 mg twice daily nalmefene as opioid antagonist to treat 15 patients with a long history of eating disorder, all of whom were chronic and resistant to several other forms of treatment. Nine (responders) showed prolonged remission when treated with two to nine ketamine infusions at intervals of 5 days to 3 weeks. Clinical response was associated with a significant decrease in Compulsion score: before ketamine, mean +/- SE was 44.0 +/- 2.5; after ketamine, 27.0 +/- 3.5 (t test, p = 0.0016). In six patients (non-responders) the score was: before ketamine, 42.8 +/- 3.7; after ketamine, 44.8 +/- 3.1. There was no significant response to at least five ketamine treatments, perhaps because the compulsive drive was re-established too soon after the infusion, or because the dose of opioid antagonist, nalmefene, was too low.

The effect of propofol on midazolam metabolism in human liver microsome suspension

We have studied the inhibitory effects of propofol on the metabolism of midazolam using human liver microsomes. In addition, we also investigated whether the lipid in which propofol is solubilised inhibits the metabolism of midazolam. Only high concentrations of propofol (> 100 mmol), greater than those found in clinical practice, inhibited the metabolism of midazolam. The lipid had no effect on the metabolism of midazolam. This study differs from other laboratory studies looking at the inhibitory effects of propofol. These showed inhibition at concentrations similar to those seen in patients. The reasons for the differences may be explained by the use of different substrates or methodology. Propofol may be an enzyme inhibitor, but this remains to be shown to be important in patients.

Effects of inotropes on human leucocyte numbers, neutrophil function and lymphocyte subtypes

We have investigated the effects of inotropes with different adrenergic receptor specificity on differential white cell count, lymphocyte subtypes and neutrophil function in healthy volunteers. Six healthy, male volunteers were enrolled into this randomized, placebo-controlled pilot study. Each volunteer was studied on four separate occasions during a 2-h infusion of various agents, and for 2 h after stopping the infusion. The agents investigated were adrenaline 0.1 microgram kg-1 min-1, dobutamine 5 micrograms kg-1 min-1, dopexamine 2 micrograms kg-1 min-1 and 5% glucose 0.5 ml kg-1 h-1. Venous blood was sampled at 0, 30, 120 and 240 min. Haemodynamic monitoring was continued throughout the study. Full blood count, white cell differential count and enumeration of lymphocyte subtypes were performed. Neutrophil function tests included chemoluminescence, and assessment of neutrophil chemotaxis, phagocytosis and adhesion. The Wilcoxon signed rank test was used to compare differences between placebo and active drugs at each time compared with baseline. There was a significant increase in white cell count, lymphocyte count and neutrophil count with adrenaline, and a small but significant decrease in these variables with dobutamine and dopexamine. These changes were also apparent for absolute CD3+, CD4+ and CD8+ lymphocyte counts. Neutrophil respiratory burst in response to f-methionyl-leucyl-phenylalanine increased significantly only with adrenaline at 30 min (P = 0.046). There were no other significant changes in tests of neutrophil function. Infusion of inotropes was associated with changes in white cell numbers, lymphocyte subtypes and neutrophil respiratory burst. In healthy volunteers, adrenaline had effects different from those of dobutamine and dopexamine. The clinical relevance of such effects requires further investigation in critically ill patients.

The aliphatic oxidation of salmeterol to alpha-hydroxysalmeterol in human liver microsomes is catalyzed by CYP3A

Salmeterol xinafoate (Serevent) is a long-acting beta2-adrenoceptor agonist, used in the treatment of asthma, that has bronchodilator and anti-inflammatory action. Salmeterol is extensively metabolized by aliphatic oxidation in humans, with the major metabolite being alpha-hydroxysalmeterol. The aim of this investigation was to identify the specific cytochrome P450 (P450) isoform or isoforms involved in the formation of alpha-hydroxysalmeterol in human liver microsomes. [14C]Salmeterol was incubated with a pooled sample (N = 19) of human liver microsomes in the absence or presence of selective chemical inhibitors of the major human P450 isoforms. One microM ketoconazole, a selective inhibitor of CYP3A, substantially inhibited the metabolism of salmeterol to alpha-hydroxysalmeterol. Disulfiram caused a small but consistent decrease in the amount of alpha-hydroxysalmeterol formed, possibly reflecting less than total selectivity for CYP2E1 under the conditions used. Other selective inhibitors had no significant effect on the metabolism of salmeterol. The rates of formation of alpha-hydroxysalmeterol in 10 individual liver microsomal samples showed an approximately 10-fold variation and were found to be highly correlated (r2 = 0.94; p < 0.001) with rates of metabolism of midazolam to 1'-hydroxymidazolam, a marker of CYP3A activity, in the same microsomal samples. No significant correlation was evident for the metabolism of salmeterol with levels of total P450 or other markers of human P450 activities in the same microsomal samples, thus indicating that the formation of alpha-hydroxysalmeterol is catalyzed predominantly by CYP3A. Insect cell microsomes that coexpressed human CYP3A and NADPH-P450 reductase were able to metabolize [14C]salmeterol to alpha-hydroxysalmeterol, thus confirming the role of CYP3A in catalyzing this reaction. The therapeutic dose of salmeterol is very low, so it is unlikely that any clinically relevant interactions will be observed as a consequence of the coadministration of salmeterol and other pharmaceutical agents that are metabolized by CYP3A.

What changes drug metabolism in critically ill patients--III? Effect of pre-existing disease on the metabolism of midazolam

Liver samples were obtained at hepatectomy from patients with end stage alcoholic liver disease (n = 5), primary biliary cirrhosis (n = 5) and chronic rejection needing retransplantation (n = 5). Normal liver material was also obtained from five organ donors. From these samples microsomes were made containing cytochrome P450 3A. The amount of this enzyme was measured by Western immunoblotting and its function assessed by measuring the rate of production of two metabolites of midazolam, 1-hydroxy midazolam and 4-hydroxy midazolam. There was a wide range in all groups for both the expression and function of this enzyme. Liver tissue affected by cirrhotic disease showed greater preservation of enzyme function than that affected by hepatocellular disease. There was a good correlation between the expression of the enzyme and production of the 1-hydroxy metabolite, but a poor correlation between production of the 4-hydroxy metabolite and expression. This poor correlation may reflect the failure to measure the specific enzyme responsible for producing 4-hydroxy midazolam.

The plasma turnover of transfused antithrombin concentrate in patients with acquired antithrombin deficiency

Antithrombin concentrate, prepared from human plasma, has been used as replacement therapy in 35 patients with acquired antithrombin deficiency. The inhibitory activity of the concentrate, measured by chromogenic assay, correlates well with the manufacturer's quoted activity. The mean in vivo recovery of the product was 0.0124 iu mL-1 per iu of antithrombin (AT) concentrate administered by kilogram body weight. The recovery was similar in all diagnostic groups studied and did not vary during the course of treatment. Consumption of the antithrombin concentrate was monitored by measuring the production of thrombin-antithrombin complexes and the loss of plasma antithrombin activity. The mean concentration of thrombin-antithrombin complexes was elevated (23 ng mL-1) at the time of admission to the intensive care unit and fell progressively over the next 4 days. The mean time for the decay of half the antithrombin activity was 23 h during the first 24 h of therapy and rose to 42.1 h after day 1. The recovery and half-life measurements are necessary to plan an appropriate dosage regimen for the administration of this antithrombin concentrate in acquired deficiency states.

What changes drug metabolism in critically ill patients?--II Serum inhibits the metabolism of midazolam in human microsomes

Serum samples from five critically ill patients were incubated with microsomes prepared from three human livers. The activity of cytochrome P450 3A4 was assessed by measuring the disappearance of midazolam and the appearance of 1-hydroxy midazolam in the incubates. Significant inhibition of the ability of this enzyme to metabolise midazolam was seen. This occurred in incubates containing serum samples from critically ill patients and not in those containing serum from two normal volunteers. The mechanism of this inhibition is unknown, but several possibilities are discussed.

The role of flumazenil in the critically ill

Flumazenil is a specific benzodiazepine antagonist. It competitively inhibits the action of benzodiazepines at gamma aminobutyric acid (GABA) receptors in the central nervous system and thus reverses the sedative effects of benzodiazepines. Usually, it is given intravenously as a bolus dose or as an infusion. It has a short duration of action. Flumazenil is extensively metabolized to compounds that have minimal benzodiazepine antagonistic properties. Reversal of sedation can be useful in many conditions that are often encountered in the critically ill. The adverse effects of its use are usually predictable and, with sufficient clinical monitoring, are usually avoidable. These properties make it a useful and safe drug when used appropriately.

Anaesthetic drugs and bacterial contamination

We investigated the bacterial contamination of commonly used intravenous anaesthetic agents. Ten trainee anaesthetists drew up four syringes each of propofol, midazolam, thiopentone, 0.9% saline and a culture medium control using their normal practice. A set of syringes was cultured at the time of drawing up and at 2, 4 and 8 h afterwards. No anaesthetist washed his or her hands before drawing up the drugs. Six anaesthetists capped the syringes using sheathed needles. Eight syringes were contaminated with bacteria. Coagulase-negative staphylococci were isolated from six syringes (four sheathed and two unsheathed) and an Acinetobacter sp. from two syringes (one sheathed and one unsheathed). No bacteria were cultured from the midazolam syringes. However, two syringes from each of the other solutions were contaminated. This implies that one syringe was contaminated when it was drawn up, at 2 h a further two had detectable contamination, two more were contaminated at 4 h and three more at 8 h. We cannot recommend drawing up drugs at the start of a list for use later in the day. They should be used immediately after drawing up. Basic hand washing before drawing up drugs may reduce contamination.

Multiple forms of cytochrome P450 are involved in the metabolism of ondansetron in humans

Ondansetron is cleared primarily by metabolism in humans, with hydroxylation of the indole moiety in the 7- and 8-positions being the major identified phase I pathways. In vitro studies using lymphoblastoid cell lines expressing single human cytochrome P450 forms and hepatic microsomes were undertaken to investigate the forms involved in the metabolism of ondansetron in humans. The cell lines that expressed CYP1A1, CYP1A2, and CYP2D6 were shown to be capable of metabolizing [14C]ondansetron. Studies with human hepatic microsomes and the specific inhibitors furafylene, quinidine, and ketoconazole confirmed the role of CYP1A2 and CYP2D6 and also demonstrated the involvement of the CYP3A subfamily. The data in this study collectively indicate that multiple cytochrome P450 forms, including CYP1A1, CYP1A2, CYP2D6, and the CYP3A subfamily, are probably involved in the clearance of ondansetron in humans, with no single form of cytochrome P450 dominating the overall metabolism of ondansetron. The role played by CYP2D6 in the metabolism of [14C]ondansetron by human hepatic microsomes in vitro was shown to be minor. This finding is consistent with the lack of bimodality in the clinical pharmacokinetics of ondansetron. It is therefore concluded that ondansetron is metabolized by multiple forms of cytochrome P450, and this limits the likelihood of a clinically relevant interaction with ondansetron by a modulator of a single form of cytochrome P450.

Propofol versus propofol with midazolam for laryngeal mask insertion

We evaluated the addition of midazolam to propofol during induction of anaesthesia by assessing laryngeal mask tolerance, haemodynamic variables, recovery times and cost. Forty patients (ASA grades I-IV) undergoing elective surgery were allocated randomly to receive a standard dose of propofol or a smaller dose of propofol combined with midazolam. A laryngeal mask was inserted and any episodes of coughing or hiccuping during its insertion or removal were recorded. Anaesthesia was maintained with nitrous oxide and enflurane with fentanyl for analgesia. After surgery, recovery times, pain, shivering, nausea, vomiting and analgesic requirements were recorded. The cost of the drugs used was also calculated. No significant differences were detected in any variables, except that patients given propofol needed more morphine in the recovery ward. The average cost of propofol alone was 3.47 pounds per anaesthetic, while the midazolam plus propofol cost was 2.03 pounds. Adding midazolam to propofol allowed a reduced dose of propofol to be used without adverse effects, while reducing the anaesthetic costs.

Desflurane and the sensitivity of upper airway reflexes

Sixty consecutive patients who were given an anesthetic, not needing tracheal intubation, received desflurane as part of the anesthetic technique to assess the incidence of upper airway irritation. A variety of induction agents and artificial airways were used. The incidence of upper airway irritation was recorded. Eight patients coughed at induction. Five of these were related to insertion of a laryngeal mask and probably represent light anesthesia. One was unrelated to instrumentation, another caused by a partially obstructed airway and the final one occurred in a child with an upper respiratory tract infection. Six episodes of coughing and hiccoughs occurred after the end of anesthesia. Four were related to removal of an airway. Five episodes of coughing occurred in the ten smokers, confirming the importance of this as a risk factor. Six patients who coughed were given no premedication or were anesthetized before it could take effect. Coughing occurs during general anesthesia, but it is caused by many factors. In adults, using desflurane it does not appear to be a significant risk factor.