Atomised lidocaine for airway topical anaesthesia in the morbidly obese: 1% compared with 2%

Airway anaesthesia using atomised lidocaine for awake oral fibreoptic intubation in morbidly obese patients was evaluated using two doses of local anaesthetic. In this randomised, blinded prospective study, 40 ml of atomised 1% (n = 11) or 2% (n = 10) lidocaine was administered with high oxygen flow as carrier. Outcomes included time for intubation, patient tolerance to airway manipulation, haemodynamic parameters, the bronchoscopist's overall satisfaction, and serial serum lidocaine concentrations. Patients receiving lidocaine 1% had a longer mean (SD) time from the start of topicalisation to tracheal tube cuff inflation than those receiving lidocaine 2% (8.6 (0.9) min vs 6.9 (0.5) min, respectively; p < 0.05). Patients in the 1% cohort demonstrated increased responses to airway manipulation (p < 0.0001), reflecting lower bronchoscopist's satisfaction scores (p < 0.03). Haemodynamic responses to topicalisation and airway manipulation were similar in both groups. Peak plasma concentration was lower in the 1% group (mean (SD) 1.4 (0.3) and 3.8 (0.5) microg.ml(-1), respectively; p < 0.001). Airway anaesthesia using atomised lidocaine for awake oral fibreoptic intubation in the morbidly obese is efficacious, rapid and safe. Compared with lidocaine 1%, the 2% dose provides superior intubating conditions.

Airway topicalisation in morbidly obese patients using atomised lidocaine: 2% compared with 4%

We evaluated the technique of airway anaesthesia using atomised lidocaine for awake oral fibreoptic intubation in morbidly obese patients using two doses of local anaesthetic. Morbidly obese patients were allocated to receive either 2% or 4% lidocaine (40 ml) for oral airway anaesthesia using an atomiser with high oxygen flow. Patients were carefully sedated using midazolam and fentanyl. Outcomes included patient tolerance to airway manipulation, haemodynamic parameters, and serial plasma lidocaine concentrations. In all, 27 patients were enrolled in the study (2% cohort n = 14, 4% cohort n = 13). Patient characteristics and time for topicalisation and airway management were similar. Haemodynamic parameters did not change significantly. Tolerance to insertion of the Ovassapian airway, bronchoscopy, and tracheal tube positioning was excellent (12 vs 12 patients, 12 vs 12 patients, and 8 vs 12 patients had no response, respectively, 2% vs 4%). Differences did not reach statistical significance. Peak plasma lidocaine concentration was significantly lower in the 2% group (2.8 (0.8) microg.ml(-1) compared with 6.5 (1.0) microg.ml(-1), p < 0.05). Airway anaesthesia using atomised lidocaine for awake fibreoptic intubation in the morbidly obese is efficacious, rapid, and safe. Compared with 4% lidocaine, the 2% dose provides acceptable intubating conditions in most cases and produces lower plasma lidocaine levels.

In vivo higher glucuronidation of mycophenolic acid in male than in female recipients of a cadaveric kidney allograft and under immunosuppressive therapy with mycophenolate mofetil

Mycophenolate mofetil (MMF), an immunosuppressant drug used in organ transplantation to prevent rejection, is being used increasingly in association with cyclosporine and tacrolimus. Mycophenolic acid (MPA) is primarily metabolized in the liver to its 7-O-glucuronide (MPAG) derivative. The concentrations of MPAG in serum are many times the concentrations of MPA. Although MPAG has not shown immunosuppressant activity, it was postulated that it could displace MPA from its binding sites on albumin and hence increase the biologic effects of MPA. This effect could be important for patients with acute renal failure; under this condition, MPAG was shown to accumulate. The goal of this study was to document the MPAG/MPA concentration ratio in 100 renal transplant patients under a mixed immunosuppressive therapy. Further, the study addressed the question of whether MPAG can displace MPA in vivo from bound albumin in a representative renal transplant patient population under immunosuppressive therapy. Levels of MPAG and MPA were measured by high-performance liquid chromatography. The distribution of the ratios was not parametric as it tailed toward elevated values. After a square root transformation of the data, parametric analysis was possible. The average MPAG/MPA ratio was 15.0 +/- 2.2 for men versus 7.7 +/- 0.9 for women. Men treated with MMF and tacrolimus showed a lower ratio than patients treated with MMF and cyclosporine, confirming that tacrolimus inhibits glucuronidation of MPA. Further, it was determined that at physiologic concentrations, MPAG does not increase the amount of free MPA. Because MPAG can favor the elimination of MPA, it can be concluded that gender differences and cotreatment with tacrolimus must be taken into consideration when MMF is being administered.

Stability of PO2, PCO2, and pH in fresh blood samples stored in a plastic syringe with low heparin in relation to various blood-gas and hematological parameters

OBJECTIVE

To assess the stability of PO2, PCO2 and pH in fresh individual blood samples drawn in a plastic syringe with low heparin and stored at 22 degrees C or on ice in relation to various biochemical and hematological parameters of the samples.

METHODS

PO2, PCO2, and pH were measured at determined times in samples kept at 22 degrees C or on ice. The magnitude of change in blood-gas parameters over time for each group of samples was determined. The change in PO2 was examined according to its initial value, the oxygen content (CaO2), the hemoglobin concentration, the leukocyte and platelet counts of each sample.

RESULTS

The changes in PO2, PCO2, and pH over time were about three times lower in samples stored on ice than in the ones at 22 degrees C. Nevertheless, rapid increases in PO2 were observed for samples stored on ice with an initial PO2 between 50 and 250 mm Hg. Samples with PO2 over 250 mmHg exhibited a decrease in PO2 over time. No correlation was observed between the change in PO2 and the oxygen content, the hemoglobin concentration or the leukocyte and platelet counts for both groups of samples stored at 22 degrees C or on ice.

CONCLUSION

PO2 in samples with an initial PO2 between 50 and 250 mm Hg stored on ice should be analyzed within 30 min. However, PCO2 and pH didn't exhibit clinically significant changes within 60 min under similar conditions. The magnitude of change in PO2 for samples kept on ice was dependent on their hemoglobin capacity for buffering oxygen, which is in converse relation with the oxygen saturation level of hemoglobin (SatHbO2). It is believed that the alteration in PO2 for samples stored on ice is produced predominantly by diffusion of oxygen through the plastic wall of the syringe, whereas it would be mainly of metabolic origin in samples at room temperature.

Compromised allograft rejection response in transgenic mice expressing antisense sequences to retinoic acid receptor beta2

Transgenic mice expressing antisense sequences to retinoic acid receptor beta2 (AS-RARbeta2 mice) were generated. The transgene was expressed in T cells, macrophages, and non-T spleen cells. These AS-RARbeta2 mice had four- to sevenfold higher endogenous RARbeta2 messages in their macrophages, comparing with their nontransgenic littermates, but the RARbeta protein level was significantly lower in these cells. This suggests that the antisense message interferes with RARbeta2 translation, and there is a feedback control of the RARbeta2 mRNA level in the macrophages. The endogenous RARbeta2 message was not detectable in T and B cells of either the transgenic or nontransgenic mice. These mice appeared to be healthy upon visual inspection. When transplanted with allogenic cardiac grafts heterotopically, the mice showed significantly compromised rejection response. These mice had a decrease of the macrophage population in spleen, using the nontransgenic littermates as references. The generation of alloantigen-specific T cell cytotoxicity was decreased in these AS-RARbeta2 mice. These results suggest that macrophage development and T cell function are affected by antisense expression of RARbeta2, and that anomaly in these cells might be contributing factors to the compromised immune response observed in the AS-RARbeta2 mice.

Compromised allograft rejection response in transgenic mice expressing antisense sequences to retinoic acid receptor beta2

Transgenic mice expressing antisense sequences to retinoic acid receptor beta2 (AS-RARbeta2 mice) were generated. The transgene was expressed in T cells, macrophages, and non-T spleen cells. These AS-RARbeta2 mice had four- to sevenfold higher endogenous RARbeta2 messages in their macrophages, comparing with their nontransgenic littermates, but the RARbeta protein level was significantly lower in these cells. This suggests that the antisense message interferes with RARbeta2 translation, and there is a feedback control of the RARbeta2 mRNA level in the macrophages. The endogenous RARbeta2 message was not detectable in T and B cells of either the transgenic or nontransgenic mice. These mice appeared to be healthy upon visual inspection. When transplanted with allogenic cardiac grafts heterotopically, the mice showed significantly compromised rejection response. These mice had a decrease of the macrophage population in spleen, using the nontransgenic littermates as references. The generation of alloantigen-specific T cell cytotoxicity was decreased in these AS-RARbeta2 mice. These results suggest that macrophage development and T cell function are affected by antisense expression of RARbeta2, and that anomaly in these cells might be contributing factors to the compromised immune response observed in the AS-RARbeta2 mice.

Effects of reducing reagents and temperature on conversion of nitrite and nitrate to nitric oxide and detection of NO by chemiluminescence

To measure the concentration of nitrites and nitrates by chemiluminescence, we examined the efficiency of five reducing agents [V(III), Mo(VI) + Fe(II), NaI, Ti(III), and Cr(III)] to reduce nitrite (NO2-) and (or) nitrate (NO3-) to nitric oxide (NO). The effect of each reducing agent on the conversion of different amounts of NO2- and (or) NO3- (100-500 pmol, representing concentrations of 0.4 to 2 mu molar) to NO was determined at 20 degrees C for NO2- and at 80 degrees C for NO3-. The effect of temperature from 20 to 90 degrees C on the conversion of a fixed amount of NO2- or NO3- (400 pmol or 1.6 mu molar) to NO was also determined. These five reducing agents are similarly efficient for the conversion of NO2- to NO at 20 degrees C. V(III) and Mo(VI) + Fe(II) can completely reduce NO3- to NO at 80 degrees C. NaI and Cr(III) were unable to convert NO3- to NO. Increased temperature facilitated the conversion of NO3- to NO, rather than that of NO2- to NO. We evaluated the recovery of NO2- and NO3- from plasmas of pig and of dog. Recovery from plasma of both animals was reproducible and near quantitative.

The penetration of oral ciprofloxacin into the aqueous humor, vitreous, and subretinal fluid of humans

We examined ciprofloxacin levels in the aqueous humor, vitreous, or subretinal fluid in 40 patients undergoing cataract extraction, vitrectomy, or scleral buckling. Ciprofloxacin, 750 mg, was administered orally an average of 17 1/2 and 5 1/2 hours preoperatively. We obtained mean ciprofloxacin levels of 0.53 microgram/ml in aqueous humor, 0.51 microgram/ml in vitreous, and 0.71 microgram/ml in subretinal fluid. These vitreous levels exceed the minimum inhibitory concentration (MIC)90 of Staphylococcus epidermidis, Propionibacterium species, Pseudomonas aeruginosa, Proteus mirabilis, and Haemophilus influenzae, as well as the MIC70 of S. aureus and Bacillus cereus. Therefore, ciprofloxacin may have a role in the management and prevention of endophthalmitis.

Higher pentamidine levels in AIDS patients with hypoglycemia and azotemia during treatment of Pneumocystis carinii pneumonia

Trimethoprim-sulfamethoxazole (TMP-SMZ) and pentamidine are both licensed for the treatment of Pneumocystis carinii pneumonia (PCP). However, their use is associated with various adverse side effects. In this prospective study, 26 AIDS patients with 32 episodes of PCP were treated with pentamidine (4 mg/kg/d). Each patient was treated for 12 to 21 days, depending on the rapidity of onset of the clinical response. During the 32 PCP episodes, hypoglycemia occurred in 16 instances, azotemia in 12, liver toxicity in 10, and leukopenia in 8. The occurrence of thrombopenia, leukopenia, and liver toxicity was not related to age, pentamidine levels, or other complications. However, patients who had hypoglycemia during pentamidine treatment had higher serum pentamidine levels than patients who did not have hypoglycemia (107 +/- 40 versus 70 +/- 26 ng/ml, p less than 0.004). In addition, we observed that patients with azotemia showed higher pentamidine levels during treatment (120 +/- 35 versus 64 +/- 22 ng/ml, p less than 0.001). In fact, 100% (11/11) of patients with serum pentamidine concentration greater than 100 ng/ml had fasting hypoglycemia and/or azotemia, while 33% (7/21) of those with pentamidine levels less than 100 ng/ml had these side effects (p less than 0.001). The relative risk of these complications with pentamidine levels greater than 100 ng/ml was 3 (95% confidence interval, 1.6 to 5.5). Fine-tuning the dose of pentamidine may eventually prove useful to avoid toxicity and optimize therapy.

High pentamidine levels associated with hypoglycemia and azotemia in a patient with Pneumocystis carinii pneumonia

We report on a patient who presented with a Pneumocystis carinii pneumonia. Intravenous pentamidine (4 mg/kg/day) was given for 14 days without the occurrence of adverse effects. During this treatment, the mean (+/- SD) serum pentamidine trough concentration was 94 +/- 16 ng/ml. Three days later, the patient was admitted because of fever, and pentamidine (4 mg/kg/day) was again started. Fasting hypoglycemia and azotemia then occurred; the mean serum trough pentamidine level was 190 +/- 10 ng/ml during this week of treatment. We conclude that the occurrence of hypoglycemia and azotemia during pentamidine therapy may not be idiosyncrasic, but seemed associated in our patient with high levels of serum pentamidine.

Clinical usefulness of high-pressure liquid chromatographic determination of serum pentamidine in AIDS patients

We have developed a reproducible HPLC method to determine serum pentamidine, which demonstrates good chromatographic performance, and is sensitive enough to measure therapeutic doses. Pentamidine is first extracted from serum by passage through a C-18 extraction cartridge. Potential interfering substances are then removed by washing with 100% methanol. Pentamidine is eluted from the extraction cartridge with 1-heptanesulfonic acid. The extract is chromatographed on a highly deactivated column for basic compounds in the presence of minimal concentrations of 1-heptanesulfonic acid as the pairing agent. Detection is by fluorescence. The method can determine serum pentamidine levels in the range of 15-600 ng/mL free of interference from other drugs. In monitoring pentamidine levels in AIDS patients with Pneumocystis carinii, we found that trough serum levels over 100 ng/mL were associated with toxicity (hypoglycemia or azotemia) in 100% of patients. With levels under 100 ng/mL, signs of toxicity were observed in only 29% of the patients. We conclude that dose adjustment based on serum levels reduces the incidence of toxicity and enhances pentamidine therapy.

Effects of isoflurane, halothane, and enflurane on myocardial flow and energy stores in the perfused rat heart

The effect of three volatile anesthetics (halothane, enflurane, and isoflurane) on coronary flow and metabolic state of isolated rat hearts was studied. These anesthetics are coronary dilators and their effects are dose dependent. At 2 MAC (minimum alveolar concentration), isoflurane, enflurane, and halothane increase coronary flow by 114 +/- 5.9, 93 +/- 6.1, and 77 +/- 6.4%, respectively (p less than 0.001). At these concentrations, they also have a modest but significant metabolic effect causing a 30% reduction in myocardial ATP and phosphocreatine levels, with no significant modification in ADP and AMP concentrations. Energy charge and lactate/pyruvate ratio were also unaffected by these anesthetics. The vascular and metabolic effects were reversible within 2 and 30 min, respectively. Perfusion of the hearts with a Krebs-Henseleit solution without Pi did not interfere with the vascular and the metabolic effect of the anesthetics; however, in this case, ATP and phosphocreatine concentration did not return to control levels after their discontinuation despite full recovery of the vascular effect. These data suggest that the volatile anesthetics have direct coronary vascular and myocardial metabolic effects and that these effects occur independently.

Metabolic effects of acetate on the heart

The effects of various substrates (15 mM glucose, 5 mM glucose, 20 mM acetate, or a combination of these substrates) on the coronary blood flow and on the energetic status of myocytes were studied in isolated perfused rat hearts. We demonstrate that low level glucose (5 mM) or high concentration of acetate (20 mM) leads to a simultaneous fall in tissue ATP, rise in tissue adenosine, and significant increment in coronary blood flow. The latter effect is especially marked with 20 mM acetate. Dipyridamole (10(-6) M) does not enhance the vasodilatation induced by acetate. The provision of 15 mM glucose together with 20 mM acetate fully prevents these changes, indicating that the vasodilatation induced by acetate is probably mediated by metabolic changes. The evidence supports the concept that a redistribution of blood flow together with a fall in tissue ATP may explain some of the adverse effects of acetate dialysis in man, and suggests that the provision of glucose may alleviate these changes.

Hypoxemia during hemodialysis: a critical review of the facts

The literature describing the fall in PaO2 during dialysis is intensively and critically reviewed. This phenomenon is related to both the type of membrane used (cellulosic v noncellulosic membrane), and to the composition of the dialysate (acetate v bicarbonate). It appears that a ventilation/perfusion mismatch due to pulmonary leukostasis can, in part, explain hypoxemia in patients dialyzed with cellulosic membranes. This phenomenon is especially apparent in patients with preexisting pulmonary abnormalities. However, hypoventilation remains the major cause of hypoxemia. This hypoventilation is mainly due to CO2 consumption during acetate metabolism (acetate dialysis), or alkalinization of the blood (bicarbonate dialysis). The metabolic consequences of acetate metabolism, and of bicarbonate and CO2 losses through the dialyzer are critically analyzed. The cause for the increment in oxygen consumption during acetate dialysis is examined. Finally, the respective role of these combined factors are described and used to explain the changes in VCO2, VO2, respiratory quotient (RQ), and PaO2 reported in the literature during dialysis against acetate and/or bicarbonate.

Efficacy of incorporating cyclosporine into liposomes to reduce its nephrotoxicity

A preparation of cyclosporine (CsA) in liposomes was tested in the rat to evaluate its effectiveness in reducing CsA nephrotoxicity. The drug was injected intravenously in unilaterally nephrectomized Lewis rats at a daily dose of 25 mg/kg for 14 days, either in a cremophore solution (eight rats) or in a preparation of liposomes (eight rats). Another group of four animals received the cremophore solution alone. Overall, rats treated with the CsA-liposome preparation had reduced toxicity, exhibiting better survival rates and less weight loss than those treated with the CsA-cremophore. Incorporating CsA into liposomes induced a statistically significant (p less than 0.05) reduction in the otherwise progressive increase of serum creatinine during week 2 of the experiment. Following administration of CsA-liposome preparation, epithelial cells of the proximal renal tubules appeared morphologically normal, without evidence of vacuolization, which is characteristic of CsA nephrotoxicity and was seen in the CsA-cremophore group. Although the exact mechanism is not clearly understood, it is likely that the tissue distribution of CsA, when incorporated into liposomes, is modified in favour of the reticuloendothelial cells, thereby sparing highly sensitive, but non-target organs such as the kidneys.

An enzymic assay for the specific determination of methanol in serum

This method for the specific determination of methanol in serum is based on the following two reactions: (formula; see text) Alcohol oxidase is not specific: it converts all lower alcohols to their corresponding aldehydes; however, formaldehyde dehydrogenase is specific and thus the transformation of NAD+ to NADH (which is used to monitor the reaction) proceeds only if methanol is originally present in the sample. The method was automated with a Roche COBAS FARA centrifugal analyzer. The calibration curve is linear between 0.6 and 12 mmol/L. The detection limit is about 0.6 mmol/L. The CV is 4.6% for a concentration of 3 mmol/L. When 55 serum specimens known to be free of methanol were supplemented with known amounts of methanol and analyzed by the enzymatic method, the results correlated well (r = 0.987) with the true values, the regression equation being: y = 1.016x + 0.661, where x represents the true values. Results are not affected by other alcohols that may be present in serum, by methanol metabolites, or by some commonly prescribed drugs. The major advantage of this new assay is that it can be used 24 h a day in any clinical chemistry laboratory.

An enzymic assay for the specific determination of methanol in serum

This method for the specific determination of methanol in serum is based on the following two reactions: (formula; see text) Alcohol oxidase is not specific: it converts all lower alcohols to their corresponding aldehydes; however, formaldehyde dehydrogenase is specific and thus the transformation of NAD+ to NADH (which is used to monitor the reaction) proceeds only if methanol is originally present in the sample. The method was automated with a Roche COBAS FARA centrifugal analyzer. The calibration curve is linear between 0.6 and 12 mmol/L. The detection limit is about 0.6 mmol/L. The CV is 4.6% for a concentration of 3 mmol/L. When 55 serum specimens known to be free of methanol were supplemented with known amounts of methanol and analyzed by the enzymatic method, the results correlated well (r = 0.987) with the true values, the regression equation being: y = 1.016x + 0.661, where x represents the true values. Results are not affected by other alcohols that may be present in serum, by methanol metabolites, or by some commonly prescribed drugs. The major advantage of this new assay is that it can be used 24 h a day in any clinical chemistry laboratory.

Acetate metabolism and bicarbonate generation during hemodialysis: 10 years of observation

The capacity of chronically hemodialyzed patients to metabolize acetate during conventional hemodialysis was evaluated using a retrospective study in 219 patients dialyzed for up to ten years under similar dialysis conditions. For each patient, and using all available data, a regression line relating the changes of plasma total CO2 during dialysis as a function of the pre-dialysis value was calculated. The intercept of this function indicates the plasma concentration where the losses of bicarbonate in the dialysate is matched by the generation of bicarbonate arising from the metabolism of acetate. This value therefore represents an individual index of the capacity of each patient to metabolize acetate. A value for this index smaller than 18.0 mM was considered abnormal. It was shown that around 10% of chronically hemodialyzed patients are clearly unable to metabolize acetate optimally. This defect is not related to the duration of dialysis, body weight or quality of hemodialysis treatments but is strongly related to sex, 19 of the 22 "acetate intolerant" patients being women. In a prospective study, all the 60 patients of the same population undergoing active dialysis were studied, and this index identified 12 abnormal (11 women, 1 man) patients and 48 normal patients. Plasma acetate measured at the end their dialysis treatments were significantly higher in abnormal than in normal patients. It is concluded: that this index is useful to identify the patients unable to metabolize acetate optimally; that only around 10% of hemodialyzed patients present a severe problem when dialyzed against acetate and should be dialyzed against bicarbonate; that dialysis against acetate does not fully correct the metabolic acidosis even in "normal" patients.

Acetate metabolism during hemodialysis: metabolic considerations

Acetate is used during regular hemodialysis to replace the bicarbonate lost during dialysis. The temporal changes of plasma bicarbonate and acetate concentrations and the critical role of acetate metabolism for the maintenance of plasma bicarbonate are described. We point out that the maximal rate of acetate oxidation in man is usually reached during dialysis, and we identify physiologic and pathologic factors that may modify this Vmax. A syndrome of 'intolerance to acetate' has been described. This syndrome is analyzed in the light of the metabolic consequences of a rapid flux of acetate oxidation in liver and muscle cells. More specifically, the effects of rapid acetate metabolism on tissue ATP, CoA, adenosine and other ATP degradation products are presented. The possible impact of dialysis-induced depletion of carnitine on optimal acetate metabolism is discussed. The potential clinical consequences produced by these changes are presented in relation to the symptoms sometimes observed during dialysis against acetate: vasodilation, hypotension and angina pectoris. The hypoxemia induced by acetate is also briefly reviewed. Different directions are proposed for future research.

Determination of the concentration and specific activity of acetone in biological fluids

The concentration of acetone dissolved in liver perfusion medium was determined by injection of the sample into a gas chromatograph equipped with a Carbopack/Carbowax-packed glass column. Interference from labile acetoacetate which readily decomposes to acetone was eliminated by treating the samples with NaBH4 prior to the analysis. Acetone was detected and quantified as 2-propanol. Separation of labeled 2-propanol in the sample by high-performance liquid chromatography allowed the determination of its specific activity. These methods make possible the convenient and rapid determination of acetone concentration and specific activity in biological samples.

Column deactivation in analysis for underivatized tricyclic antidepressants by gas chromatography with use of a nitrogen detector

I describe deactivation treatment of the OV-17 chromatographic column to minimize adsorption of tricyclic antidepressant drugs on the solid support of the column. The procedure involves heat treatment at 399 degrees C under a low flow of nitrogen, with bleeding of OV-17 liquid phase from the injector tube into the column. The column is then conditioned with vapors of phenyldiethanolamine succinate, added to the carrier gas stream by bleeding from a coated injector glass tube. This deactivation process much improves the chromatographic performance of the column, allowing a sensitivity at the nanogram level with a nitrogen-sensitive detector. Determinations of tricyclic antidepressants in plasma with such a deactivated column results in a low CV and a linear calibration curve, reflecting the effectiveness of the deactivation.

EMIT antiepileptic drug assays adapted to an Abbott-VP Analyzer and compared with a gas-chromatographic procedure

The Abbott-VP Bichromatic Analyzer was used for the determination of four antiepileptic drugs (phenobarbital, phenytoin, carbamazepine, primidone) in serum by means of a modified EMIT homogeneous enzyme immunoassay procedure. The main objective of the work was to examine the precision and the accuracy of the results obtained with this system and its cost effectiveness in comparison to the manual method. Day-to-day precision for all four drugs is excellent with coefficients of variation averaging around 5% in the therapeutic range of concentrations. Results for sera analyzed by this procedure and by a gas chromatographic method do not show any significant difference for phenytoin and phenobarbital. There are however slight differences between the two methods for carbamazepine and primidone. These small differences do not modify significantly the clinical interpretation of the results. The procedure is simple and rapid, and requires only one third of the reagents needed in the recommended manual EMIT procedure using the Gilford Stasar III, thus greatly reducing the operation costs.

Enzymic assay for serum theophylline

We describe an original procedure for determination of theophylline in serum. The drug is extracted from 0.4 mL of serum at pH 7.4 with chloroform/isopropanol (20/1 by vol) and back-extracted into sodium hydroxide (1 mmol/L). The inhibition of beef-liver alkaline phosphatases by theophylline in this alkaline phase is measured at 25 degrees C, with p-nitrophenyl phosphate as substrate, in 2-amino-2-methyl-1-propanol buffer, pH 9.4- The reciprocal of enzyme activity and theophylline concentration are linearly related in the range 2 to 60 mg/L. The maximum interference to be expected from 3-methylxanthine would increase apparent theophylline concentration by no more than 1 mg/L. The method is accurate, free of interference by other xanthines and often-coadministered drugs, and results correlate well with those by the immunoenzymic assay. Major advantages are reagent stability, low cost, and simplicity of instrumentation.

Enzymic assay for serum theophylline

We describe an original procedure for determination of theophylline in serum. The drug is extracted from 0.4 mL of serum at pH 7.4 with chloroform/isopropanol (20/1 by vol) and back-extracted into sodium hydroxide (1 mmol/L). The inhibition of beef-liver alkaline phosphatases by theophylline in this alkaline phase is measured at 25 degrees C, with p-nitrophenyl phosphate as substrate, in 2-amino-2-methyl-1-propanol buffer, pH 9.4- The reciprocal of enzyme activity and theophylline concentration are linearly related in the range 2 to 60 mg/L. The maximum interference to be expected from 3-methylxanthine would increase apparent theophylline concentration by no more than 1 mg/L. The method is accurate, free of interference by other xanthines and often-coadministered drugs, and results correlate well with those by the immunoenzymic assay. Major advantages are reagent stability, low cost, and simplicity of instrumentation.

Improved determination of serum theophylline by gas chromatography with use of a nitrogen-phosphorus detector

We describe a method for the 7-min determination of theophylline in less than 100 muL of serum. The procedure requires no centrifugation or solvent evaporation after extraction. Butylation is done on the gas-chromatographic column by injecting the serum extract followed by a butylating mixture which contains 1-iodobutane as the alkylating agent. The method is precise, accurate, and free of interference. Results correlate well with those by ultraviolet spectrophotometry.

Improved determination of serum theophylline by gas chromatography with use of a nitrogen-phosphorus detector

We describe a method for the 7-min determination of theophylline in less than 100 muL of serum. The procedure requires no centrifugation or solvent evaporation after extraction. Butylation is done on the gas-chromatographic column by injecting the serum extract followed by a butylating mixture which contains 1-iodobutane as the alkylating agent. The method is precise, accurate, and free of interference. Results correlate well with those by ultraviolet spectrophotometry.

The in vitro effect of drugs on biochemical parameters determined by a SMAC system

1. We have studied the in vitro effect of 39 drugs on 17 biochemical parameters determined by a SMAC System. Only two drugs were found to interfere: ascorbic and theophyline. 2. The ascorbic acid lowers the glucose and the bilirubine values; it increases the creatinine and the uric acid concentration. At concentration smaller than 5 mg/dl of this drug, these effects are negligible. 3. We have found a new drug interference: theophylline inhibits the alkaline phosphatase and LDH activities. This effect is not negligible on alkaline phosphatase for therapeutic levels of this drug; the action on LDH can be ignored at normal therapeutic range. 4. For a given drug, we have found different interference with biochemical parameters determined with various commercial lyophlised control sera or a liquid pool of sera. This indicates that the type of sera used in drug interference studies must be described.

An evaluation of three new blood-gas analyzer systems

Three new pH-blood-gas analyzer systems have been evaluated. These are the ABL-1, the Croning 165, the Il 513. Because of automation of analysis, accuracy, and speed of analysis, this generation of instruments represents great progress over the previous one. The ABL-1 is the most automated system: all analyses are computer controlled. The pH, P02 and PCO2 values are accurate. Calibration can not be adjusted. The Corning 165 is the least automated system. Its pH determinations are the most accurate and it is the one which uses the smallest volume of blood (125 mul). However it is the least stable and takes the longest time for completion of the analysis. The IL 513 is probably the best balanced system and its calibration can be modified. Its operation is well automated and its results are accurate.