Blood Methanol Research Articles

Simple method for determination of methanol in blood and its application in occupational health

Simple method for determination of methanol in blood and its application in occupational health

Determination of methanol in whole blood by capillary gas chromatography with direct on-column injection

A gas chromatographic procedure was developed for the determination of methanol in small-volume whole blood samples. Samples (100–200 μl) were prepared by protein precipitation, with direct injection of the supernatant on a wide-bore capillary column. The recovery of methanol and acetonitrile (the internal standard) was approximately 90% and did not vary with sample volume. The assay was linear from 2 μg/ml (the limit of detection) through 1000 μg/ml and was highly reproducible (intra-day coefficient of variation <2.5%). Assay performance was assessed following exposure of rats to methanol. The results indicate that the present procedure is suitable for studies of methanol disposition in small rodent species.

Repeated ingestion of aspartame-sweetened beverages: Further observations in individuals heterozygous for phenylketonuria

Six adults heterozygous for phenylketonuria (PKU) ingested eight successive servings of unsweetened and aspartame (APM)-sweetened beverage at 1-hour intervals in a randomized, balanced, crossover design. In one part, the eight beverage servings were not sweetened. In the other, each of the eight beverage servings provided 600 mg of APM, a dose equivalent to the amount provided by 36 oz of an APM-sweetened diet beverage. Plasma aspartate concentration was not significantly increased after ingestion of unsweetened or APM-sweetened beverage. Similarly, ingestion of the unsweetened beverage had no significant effect on plasma phenylalanine concentration. However, ingestion of APM-sweetened beverage significantly increased plasma phenylalanine concentrations 2.35 to 4.03 μmol/dL above baseline 30 minutes after ingestion. Plasma phenylalanine values reached a steady-state after administration of five servings of APM-sweetened beverage and were slightly, but significantly higher than usual postprandial values for adults heterozygous for PKU. Similarly, the ratio of the plasma phenylalanine concentration to the sum of the concentration of the large neutral amino acids was significantly higher than usual postprandial values. Blood methanol and formate concentrations remained within normal limits. These data indicate that a fasting adult heterozygous for PKU could consume the equivalent of 24 12-oz servings of APM-sweetened beverage over an 8-hour period and only increase plasma phenylalanine concentration to a modest degree.

Metabolic Interaction Between Endogenous Methanol and Exogenous Ethanol Studied in Human Volunteers by Analysis of Breath

Ethanol was administered to 5 healthy volunteers by intravenous infusion to maintain a constant blood-alcohol concentration (BAC) of about 0.8 mg/ml (17.4 mmol/l) for 3-4 hr. Before starting the infusion and at 15 min. intervals thereafter, we analysed end-expired air by a highly sensitive gas chromatographic method. The presumed concentrations of ethanol and methanol in blood were estimated indirectly from measurements in the breath. The liquid/air partition coefficients of methanol were determined for whole blood, plasma, water, and corn-oil when dilute solutions were equilibrated at 34 degrees and 37 degrees. The results at 37 degrees were 2709 +/- 165, 3400 +/- 86, 2948 +/- 221 and 44.5 +/- 6.3 for whole-blood/air, water/air, plasma/air and corn-oil/air respectively. During infusion of ethanol, the concentrations of endogenous methanol in blood rose from being between 0.4-0.8 mg/l to reach between 1.2-3.4 mg/l with a substantial inter-subject variation in rate of increase. Our results confirm the existence of endogenous methanol in human blood and breath and demonstrate that the concentrations present can rise to abnormally high levels when the body is flooded with exogenous ethanol.

Effect of repeated ingestion of aspartame-sweetened beverage on plasma amino acid, blood methanol, and blood formate concentrations in normal adults

Aspartame (APM) is a widely used dipeptide sweetener ( l-aspartyl- l-phenylalanine methyl ester). It has been suggested that excessive use of APM might elevate plasma aspartate, phenylalanine, and/or methanol concentrations to levels that are potentially harmful. Six normal young adults ingested eight successive servings of unsweetened and APM-sweetened beverage at one-hour intervals in a balanced crossover design. In one part, the beverage was not sweetened. In the other, each serving of beverage provided 600 mg APM, a dose equivalent to the amount provided by 36 oz of APM-sweetened diet beverage. Plasma aspartate concentration was not significantly increased after ingestion of unsweetened or APM-sweetened beverage. Similarly, ingestion of the unsweetened beverage had no significant effect on plasma phenylalanine concentration. However, ingestion of APM-sweetened beverage significantly increased plasma phenylalanine levels 1.41 to 2.35 μmol/dL above baseline 30 minutes after ingestion. Plasma phenylalanine values reached a steady state after administration of four to five servings and did not exceed normal postprandial values at any time. Blood methanol and formate concentrations remained within normal limits. The data indicate ready metabolism of APM when administered at levels that may be ingested by normal individuals who are heavy users of diet beverages.

Predictors of Methanol Intoxication with Unfavourable Outcome

In 10 adult patients acutely intoxicated with methanol, the base deficit and the total blood CO2 were highly correlated with blood formate level. No correlation was found between the same parameters and blood methanol level. Formate production is the main cause of acidosis in the early stages of methanol poisoning. The association of a latency period before treatment exceeding 10 hours and a blood formate level above 0.5 g/l (11.1 mmol/l) is predictive of severe methanol poisoning possibly leading to permanent sequelae.

Relationship between the concentration of ethanol and methanol in blood samples from Swedish drinking drivers

Headspace gas chromatography was used to determine the concentration of ethanol and methanol in blood samples from 519 individuals suspected of drinking and driving in Sweden where the legal alcohol limit is 0.50 mg/g in whole blood (11 mmol/l). The concentration of ethanol in blood ranged from 0.01 to 3.52 mg/g with a mean of 1.83 ± 0.82 mg/g (±S.D.). The frequency distribution was symmetrical about the mean but deviated from normality. A plot of the same data on normal probability paper indicated that it might be composed of two subpopulations (bimodal). The concentration of methanol in the same blood specimens ranged from 1 to 23 mg/l with a mean of 7.3 ± 3.6 mg/l (±S.D.) and this distribution was markedly skew (+). The concentration of ethanol ( x) and methanol ( y) were positively correlated ( r = 0.47, P < 0.001) and implies that 22% ( r 2) of the variance in blood-methanol can be attributed to its linear regression on blood-ethanol. The regression equation was y = 3.6 + 2.1 x and the standard error estimate was 0.32 mg/l. This large scatter precludes making reliable estimates of blood-methanol concentration from measurements of blood-ethanol concentration and the regression equation. But higher blood-methanol concentrations are definitely associated with higher blood-ethanol in this sample of Swedish drinking drivers. Frequent exposure to methanol and its toxic products of metabolism, formaldehyde and formic acid, might constitute an additional health risk associated with heavy drinking in predisposed individuals. The determination of methanol in blood of drinking drivers in addition to ethanol could indicate long-standing ethanol intoxication and therefore potential problem drinkers or alcoholics.

CLINICAL AND METABOLIC FEATURES OF ETHANOL-METHANOL POISONING IN CHRONIC ALCOHOLICS

The kinetics of methanol were examined in 84 chronic alcoholics admitted after drinking a cleansing solution containing 90% ethanol and 5% methanol. On admission, the average blood methanol concentration was 20 mmol/l (64 mg/dl) and blood ethanol concentration was 39 mmol/l (179 mg/dl). Although these patients were not treated with ethanol, and methanol concentrations remained high as blood ethanol concentrations fell to zero, no acidosis or other signs of classic methanol poisoning developed. The rate of metabolism of methanol was correlated to the initial ethanol concentration. To avoid unnecessary invasive therapy, treatment of methanol poisoning should be based on the case history, clinical signs, and laboratory features—not solely on blood methanol concentrations.

Severe methanol intoxication: Methanol pharmacokinetics and serum osmolality

After drinking a cocktail containing Lysol and photocopier developing fluid, seven severely intoxicated patients presented with extremely high blood methanol (MeOH) concentrations ranging from 61 to 186 mmol/L (1.94 to 5.97 g/L). Supportive measures included bicarbonate administration for profound acidosis followed by prompt hemodialysis and ethanol (EtOH) infusion. Dialysis converted the elimination kinetics of McOH from zero-order to first-order and the elimination rate constant (Kd) for each patient was determined by linear regression analysis of the concentration-time data. Simultaneous venovenous dialysis of these patients using identical procedures and equipment (Dialysis A) provided consistent Kd values from which an average Kd (Kd-A), unique to Dialysis A, was calculated. Kd-A can be used to accurately predict the duration of Dialysis A therapy required in an individual case, given the initial identification and quantitation of M90H in that patient's blood. Kd, as a measure of dialysis efficiency, is influenced by factors including equipment used, catheter placement and flow rates achieved. The most efficient dialysis regimen is desirable and can be established by selecting options that yield higher Kd results. Calculated McOH concentration (C-MeOH) was derived from the osmolar gap (Δ Osm) present in excess of that produced by EtOH. C-MeOH was a very accurate estimator of McOH concentration (paired t-test; P < .01; correlation, r = .99) when compared with the reference method of headspace gas chromatography (GC-HS). During dialysis, therapeutic EtOH and falling Me0H levels were accurately monitored using readily available laboratory tests and C-MeOH. GC-HS analysis can therefore be restricted to the initial identification and quantitation of blood McOH, after which the predictable McOH elimination can be monitored using C-MeOH.

Asymptomatic blood methanol in emergency room patients.

Over a four-month period, methanol was found in the blood of 18 patients among 687 sequential emergency room admissions screened for alcohols by gas chromatography. In the patients with positive results, blood ethanol ranged from 6 to 570 mg/dL (1.3-123.7 mmol/L), blood methanol from 2.3 to 4.0 mg/dL (0.72-1.25 mmol/L). Methanol exposure during preparation of the sampling site or in the course of specimen handling, ingestion of denatured alcohol, as well as methanol production from the metabolism of aspartame are ruled out as causes for these findings. The authors conclude that endogenous methanol production is the probable major cause, while methanol as a fermentation congener may be a contributory minor cause.

Elimination half-life of methanol during hangover.

This paper reports the elimination half-life of methanol in human volunteers. Experiments were made during the morning after the subjects had consumed 1000-1500 ml red wine (9.5% w/v ethanol, 100 mg/l methanol) the previous evening. The washout of methanol from the body coincided with the onset of hangover. The concentrations of ethanol and methanol in blood were determined indirectly by analysis of end-expired alveolar air. In the morning when blood-ethanol dropped below the Km of liver alcohol dehydrogenase (ADH) of about 100 mg/l (2.2 mM), the disappearance half-life of ethanol was 21, 22, 18 and 15 min. in 4 test subjects respectively. The corresponding elimination half-lives of methanol were 213, 110, 133 and 142 min. in these same individuals. The experimental design outlined in this paper can be used to obtain useful data on elimination kinetics of methanol in human volunteers without undue ethical limitations. Circumstantial evidence is presented to link methanol or its toxic metabolic products, formaldehyde and formic acid, with the pathogenesis of hangover.

Pharmacology and pharmacokinetics of esmolol.

Esmolol is an ultra-short-acting beta-adrenergic blocking agent that possesses minimal partial agonist activity or direct membrane depressant activity. The short duration of action of esmolol is attributable to rapid enzymatic hydrolysis by red blood cell esterases, forming ASL-8123 and methanol. Experiments in the constant-flow-perfused isolated canine hindlimb indicate that therapeutic (beta blocking) doses of esmolol lack direct vascular effects and alpha-adrenergic blocking activity and that therapeutic doses do not interfere with vascoconstrictor effects of peripheral sympathetic nerve stimulation. Esmolol produces cardiac electrophysiologic and hemodynamic effects consistent with those of beta blockade. Specifically, esmolol decreases heart rate, depresses atrioventricular nodal conduction, and decreases determinants of myocardial oxygen demand. The beneficial antiarrhythmic and infarct-size limiting effects of esmolol have been demonstrated in several experimental models. Whereas beta blockers in general are effective in settings of supraventricular arrhythmias, sinus tachycardia, and myocardial ischemia, esmolol provides the added dimension of "titratability." Thus, the short duration of action of esmolol allows for very rapid titration to a preferred steady-state level of beta blockade; rapid adjustment to different steady-state levels of beta blockade, as may be required by changing status of the patient, and rapid disappearance of beta blockade following discontinuation of esmolol infusion, should this be necessary in the event of deleterious cardiac hemodynamic effects. Thus, esmolol is ideally suited for use in the treatment of patients in whom beta blockade is desirable, but in whom level of beta blockade must be very carefully modulated.

Blood Methanol Concentrations in One-Year-Old Infants Administered Graded Doses of Aspartame

Blood methanol concentrations were measured in 24 1-year-old infants administered aspartame, a dipeptide methyl ester sweetener. The doses studied included a dose projected to be the 99th percentile of daily ingestion for adults (34 mg/kg body weight), a very high use dose (50 mg/kg body weight) and a dose considered to be in the abuse range (100 mg/kg body weight). Blood methanol values in infants were compared to values observed previously in adults administered equivalent doses of aspartame. Methanol concentrations were below the level of detection (0.35 mg/dl) in the blood of 10 infants administered aspartame at 34 mg/kg body weight, but were significantly elevated (P ≤ 0.05) after ingestion of aspartame at 50 and 100 mg/kg body weight. At the latter doses, mean peak blood methanol concentrations and the area under the blood methanol concentration-time curve increased in proportion to dose. Mean (±SEM) peak blood methanol concentration was 0.30 ± 0.10 mg/100 ml at a 50 mg/kg body weight aspartame dose (n = 6) and 1.02 ± 0.28 mg/ml at the 100 mg/kg body weight dose (n = 8). Blood methanol values in infants were similar to those observed in normal adults.

Formate concentrations in plasma from patients poisoned with methanol.

Formate and methanol were quantified in blood samples from 11 untreated methanol-poisoned subjects. The range for whole blood methanol concentrations was 0-137 mmol/l and for plasma formate concentrations 0.4-17.1 mmol/l. Simultaneously determined acid-base status and serum electrolyte concentrations allowed assessment of the relative importance of formate accumulation for the acidosis. The plasma formate concentration was highly correlated to both the calculated anion gap (r = 0.833), the bicarbonate concentration (r = 0.852) and the negative base excess (r = 0.865). The accumulation of formate fully accounted for the increase in the anion gap and the fall in plasma bicarbonate, whereas the negative base excess values were about 22% higher than the plasma formate concentration. We conclude that formate accumulation is the main or only reason for acidosis in the early, uncomplicated stages of methanol poisoning. Lactate may appear at more advanced stages.

Studies on methanol poisoning.

Eleven patients concomitantly poisoned with methanol are described. Their whole blood methanol concentration ranged from 137.2 mmol/l (4.39 g/l) to 7.4 mmol/l (0.24 g/l). The clinical course in most patients was mild, which was attributed to the concomitant and subsequent ethanol ingestion and rapid transport to dialysing units. One patient suffered permanent visual impairment of one eye while the others recovered completely. Symptoms of poisoning were most clearly correlated to the degree of metabolic acidosis. All patients were hemodialysed. In two patients the average dialysator clearance of methanol was 157 and 176 ml/min at blood flows of 200 and 215 ml/min, respectively. In the same patients the average dialysator clearance of ethanol was 149 and 164 ml/min. Assuming a volume of distribution of methanol of 0.7 l/kg, the dialysator represented about 89 and 95%, respectively, of the total body clearance of methanol during ethanol therapy. Ethanol in concentrations even lower than usually recommended may be useful as the only treatment of patients with blood methanol concentrations up to 15 mmol/l (0.5 g/l), provided there is no acidosis or visual impairment.

Blood methanol concentrations in normal adult subjects administered abuse doses of aspartame.

Blood methanol concentrations were measured in 30 normal adult subjects administered aspartame, a dipeptide methyl ester. The doses studied included the 99th percentile of projected daily ingestion (34 mg/kg body weight) and three doses considered to be in the abuse range (100, 150, and 200 mg/kg body weight). Methanol concentrations were below the level of detection (0.4 mg/dl) in the blood of the 12 normal subjects who ingested aspartame at 34 mg/kg. They were significantly elevated (p less than or equal to 0 .001) after ingestion of each abuse dose, with the mean peak blood methanol concentrations and the areas under the blood methanol concentration-time curve increasing in proportion to dose. Mean (+/- SD) peak blood methanol concentrations were 1.27 +/- 0.48 mg/dl at the 100 mg/kg dose, 2.14 +/- 0.35 mg/dl at the 150 mg/kg dose, and 2.58 +/- 0.78 mg/dl at the 200 mg/kg dose. Blood methanol concentrations returned to predosing levels by 8 h after administration of the 100 mg/kg dose. Methanol was still detected in the blood 8 h after the subjects had ingested aspartame at 150 or 200 mg/kg. Blood formate analyses were carried out in the 6 subjects who ingested aspartame at 200 mg/kg, since recent studies indicate that the toxic effects of methanol are due to formate accumulation. No significant increase in blood formate concentrations over predosing concentrations was noted. No changes were noted in any of the blood chemistry profile parameters measured 24 h after aspartame ingestion, compared to values noted before administration. Similarly, no differences were noted in ophthalmologic examinations carried out before and after aspartame loading.

Severe methanol poisoning: Application of a pharmacokinetic model for ethanol therapy and hemodialysis

Two patients with extremely high blood methanol concentrations (260 and 282 mg/dl) were successfully treated using pharmacokinetic dosing of ethanol, hemodialysis and supportive measures. Both patients recovered completely without residual ophthalmologic deficits. Early hemodialysis and inhibition of methanol metabolism with effective ethanol concentrations were attributed to the patients' full recovery. Methanol elimination was enhanced by hemodialysis as evidenced by a decrease in half-life from eight to two and a half hours. Methanol dialysance was 98 ml/min. A dosage regimen for ethanol was devised, utilizing dose-dependent pharmacokinetic parameters and the ethanol dialysance (100 to 120 ml/min) from these two patients. An ethanol loading dose of 0.6 g/kg should be administered to an adult with an acute methanol ingestion. This dose will produce a blood ethanol concentration of approximately 100 mg/dl which can be maintained by an ethanol infusion of 66 mg/kg/hour for nondrinkers to 154 mg/kg/hour for chronic ethanol drinkers. Hemodialysis should be initiated if the blood methanol concentration is greater than 50 mg/dl. If hemodialysis is initiated, the ethanol infusion should be increased by 7.2 g/hour.

Plasma and erythrocyte amino acid levels of adult humans given 100 mg/kg body weight aspartame

Blood amino acid and methanol levels were measured in 6 fasting adult subjects (3 male, 3 female) administered an abuse dose of aspartame (100 mg/kg body wt) in both solution and slurry form. A randomized cross-over design was used. Greater variation in blood aspartate, phenylalanine and methanol levels was noted when aspartame was administered in slurry form. Blood aspartate, phenylalanine and methanol levels did not exceed those associated with toxic findings in any case. Plasma aspartate levels increased from mean (± S.D.) baseline levels of 0.16 ± 0.05 μmol/dl to peak values of 0.43 ± 0.23 ( P = 0.02) 30 min after administration in solution. Plasma aspartate levels increased to peak values of 3.6 and 5.8 μmol/dl at 30–45 min in 2 of 6 subjects given aspartame in slurry form, while levels in the other 4 subjects were unchanged from baseline values. Erythrocyte aspartate levels were unchanged in all subjects. Plasma and erythrocyte phenylalanine levels increased significantly ( P = 0.001) after both solution and slurry administration. Plasma phenylalanine levels reached mean (± S.D.) peak values of 20.3 ± 2.05 and 26.0 ± 18.9 μmol/dl respectively 45 min after loading. The higher variation after slurry administration reflected 2 subjects with peak values of 45.8 and 51.3 μmol/dl. Blood methanol levels increased after both solution and slurry administration, reaching mean (± S.D.) levels of 1.16 ± 0.47 and 1.27 ± 0.48 mg/dl respectively 60–90 min after loading.

A Simple Approach to Gas Chromatographic Microanalysis of Alcohols in Blood and Urine by a Direct-Injection Technique1

An ultra-micro method utilizing direct sample Injection Is described for the simultaneous Identification and quantification of ethanol, methanol, Isopropanol, and acetone In blood and urine by gas chromatography. AIIquots of whole blood, serum, plasma, or urine and an Internal standard, 1-propanol, are mixed together In equal parts. One microllter of the mixture Is then Injected Into a Shimadzu GC-4BM gas chromatograph equipped with 8 flame Ionization detector. The glass column, 3-mm I.d. x 2-m long, Is packed with 0.2% Carbowax 1500 on 801100 Carbopak C (Supalco, Inc., Bellelento, PA #SP-1827). The column Is fitted with s precolumn glass insert filled with a loosely packed sllanlzed glass wool plug that 8ct8 as a trap for the nonvolatile protein material of the blood end urine specimens. The optimal operating condltions for the gas chromatograph are: column temperature 120~ Injector temperature 100C; carrier gas flow 20 ml/mln; hydrogen and sir pressure set st optimal conditions for 8 hydrogen flame. The relative retention times of the eluted compounds to the Internal standard, l-propsnol, are: ethanol 0.51; methanol 0.37; acetone 0.65; and Isopropanol 0.78. A simple micro method Is also described for the celiaclion and storage of blood for alcohol determination. The techniques provide a rapid, reproducible procedure for the individual or simultaneous ultra-micro analysis of alcohols cominertly encountered in clinical or forensic toxicology.

Hemodialysis for methanol intoxication

We describe nine patients with methyl alcohol poisoning who were treated with hemodialysis. The time from ingestion to dialysis varied from 4 to 100 hours. Predialysis blood methanol levels ranged from 3 to 570 mg/dl. All patients were acidotic and had an increased anion gap. Two patients died, seven recovered, but three had permanent visual impairment. There was little correlation between the blood methanol level or anion gap and visual outcome. The Interval from ingestion to treatment appears to be more important than the initial biochemical status. We recommend prompt hemodialysis if the blood methanol level Is above 50 mg/dl, when an amount of methanol exceeding the minimal lethal dose (30 ml) is known to have been ingested, when there is evidence of acidosis or when an abnormality has developed in vision, funduscopic examination or mental state. Concurrent therapy with alkali and ethanol is vital.