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Biomedical subjects

M McGuigan

Publications and source records attributed to M McGuigan.

At least 19 recordsLinked to original sources
PubMed2002

Treatment strategies for early presenting acetaminophen overdose: a survey of medical directors of poison centers in North America and Europe.

BACKGROUND: Acetaminophen is frequently used in self-poisoning in Western countries. Although treatment with N-acetylcysteine (NAC) reduces liver injury, no consensus exists on the preferred management of acetaminophen toxicity. OBJECTIVES: To describe the approach taken by toxicologists in North America and Europe toward the management of acetaminophen toxicity. METHODS: Medical directors of poison centers in the US, Canada, and Europe were surveyed by means of a questionnaire presenting two clinical scenarios of acetaminophen overdose: a healthy adolescent with no risk factors who had an acute ingestion of acetaminophen, and an adult with both acute ingestion and possible risk factors. For each case, several questions about the management of these patients were asked. RESULTS: Questionnaires were sent to medical directors of 76 poison centers in North America and 48 in Europe, with response rates of 62% and 44%, respectively. Forty percent of responders suggested using charcoal 4 hours after ingestion of a potential toxic dose of acetaminophen, and 90% recommended treatment with NAC when levels were above 150 microg/mL but below 200 microg/mL 4 hours after ingestion. Duration of treatment with oral NAC ranged from 24 to 96 hours; 38 responders suggested a duration of 72 hours. Of 49 centers recommending oral NAC, 18 (36.7%) said they might consider treatment for less than 72 hours. Eleven of 29 (37.9%) responders suggested treatment with intravenous NAC for more than 20 hours as their usual protocol or a protocol for specific circumstances. CONCLUSIONS: Our study showed large variability in the management of acetaminophen overdose. Variations in treatment protocols should be addressed in clinical trials to optimize the treatment for this common problem.

Acetaminophen↗
PubMed2001

The role of the primate amygdala in conditioned reinforcement.

Conditioned reinforcement refers to the capacity of a conditioned stimulus to support instrumental behavior by acquiring affective properties of the primary reinforcer with which it is associated. Conditioned reinforcers maintain behavior over protracted periods of time in the absence of, and potentially in conflict with, primary reinforcers and as such may play a fundamental role in complex social behavior. A relatively large body of evidence supports the view that the amygdala (and in particular the basolateral area) contributes to conditioned reinforcement by maintaining a representation of the affective value of conditioned stimuli. However, a recent study in primates (Malkova et al., 1997), using a second-order visual discrimination task, suggests that the amygdala is not critical for the conditioned reinforcement process. In the present study, excitotoxic lesions of the amygdala in a new world primate, the common marmoset, resulted in a progressive impairment in responding under a second-order schedule of food reinforcement. In addition, the responding of amygdala-lesioned animals was insensitive to the omission of the conditioned reinforcer, unlike that of control animals, for which responding was markedly reduced. In contrast, lesioned animals were unimpaired when responding on a progression of fixed-ratio schedules of primary reinforcement. These data confirm that the amygdala is critical for the conditioned reinforcement process in primates, and taken together with other recent work in monkeys, these results suggest that the contribution of the amygdala is to provide the affective value of specific reinforcers as accessed by associated conditioned stimuli.

Acoustic Stimulation↗
PubMed2001

Band-trajectory model for temperature-programmed series-coupled column ensembles with pressure-tunable selectivity.

A model and a spreadsheet algorithm is described for the prediction of solute-band migration trajectories in a series-coupled combination of two capillary GC columns with pressure-tunable and -programmable selectivity and operated under temperature-programmed conditions. The model takes into account the acceleration of carrier gas in the two columns as a result of decompression effects, the deceleration of carrier gas as a result of the increase in viscosity during temperature programming, the decrease in solute retention factors with increasing temperature during the temperature program, the differences in retention factors for the two columns, and programmed changes in the carrier-gas flow rates in the two columns during selectivity programming. In the model, the 20-meter-long column ensemble is divided into 1-cm-long intervals, and the carrier-gas velocity and column temperature are assummed to be constant in any interval. Migration times for all of the mixture solutes are computed for each column interval, and the solute-band positons in the column ensemble are plotted versus the running sum of these migration times to obtain band trajectory plots. The sum of these migration times for all 2,000 intervals gives the ensemble retention times for the solutes. Isothermal retention factors (k) for all of the mixture components at various column temperatures (Tc) are used as imput to the algorithm. Slope and intercept values of In(k) vs 1/Tc plots are used in the algorithm. General features of the model are tested using a mixture of C12-C24 normal alkanes. A mixture of polar and nonpolar compounds is used to test the utility of the model for the predicition of peak separations and retention times with pressure-tunable and -programmable selectivity. Good agreement is observed in all cases.

Journal Article↗
PubMed2001

Pulsed flow modulation for high-speed GC using a pressure-tunable column ensemble.

A computer-driven pressure controller is used to deliver pressure pulses to the junction point of two series-coupled columns using different stationary-phase chemistries. The column ensemble consists of a trifluoropropylmethyl polysiloxane column followed by a dimethyl polysiloxane column. Each pressure pulse causes a differential change in the carrier gas velocities in the two columns, which lasts for the duration of the pulse. A pressure pulse is used to selectively increase the separation of a component pair that is separated by the first column but coelutes from the series-coupled ensemble. If both components are on the same column when the pulse is applied, a small change in the ensemble separation occurs. If one component of the pair is on the first column and the other component is on the second column, a pressure pulse can result in a much larger change in the ensemble separation for the component pair. A model with a spreadsheet algorithm is used to predict the effects of a pressure pulse on the trajectories of component bands on the column ensemble. The effect of the initiation time of a pressure pulse is investigated for a two-component mixture that coelutes from the column ensemble. For the case where the entire pressure pulse occurs when one of the components is on the first column and the other component is on the second column, the peak separation from the ensemble increases nearly linearly with the product of the pressure pulse amplitude and the pulse duration. Peak shape artifacts are observed if the pressure pulse occurs when a solute band is migrating across the column junction point.

Journal Article↗
PubMed2001

Parent and caregiver compliance with poison center advice.

BACKGROUND: The purpose of this study was to assess the compliance of parents and caregivers whose children (under 6 years of age) accidentally ingested antihistamines, decongestants, or both. METHODS: We used a prospective-descriptive study design and developed a convenience sample from eligible calls retrieved from the records from January 19, 1999 to February 28, 1999. Poison control specialists categorized the children into two groups: toxic and needing treatment in a hospital or nontoxic and not needing treatment at a hospital. Compliance with Poison Control Center advice was measured by follow-up telephone calls made by a research assistant within 7 days of the initial call. RESULTS: One hundred forty-seven calls were retrieved and followed. One hundred and seven (72.8%) callers had been advised that no treatment was needed. One hundred (93.4%) of these 107 followed Poison Control Centre advice. Forty (27.2%) of the 147 callers were advised to take their child to an emergency department. Thirty-nine (97.5%) of these 40 complied with the advice. There was no statistically significant difference in compliance rates between the two groups (chi2 = 0.306, df = 1, p = 0.58). DISCUSSION AND CONCLUSIONS: In this group of callers, compliance was high. Reasons for noncompliance included caregiver anxiety, specifically the need for a second opinion. Future studies are needed to determine the level of compliance more definitively. Studies should include subjects from other age groups, other exposures, and other types of callers.

Child, Preschool↗
PubMed2000

Neuromuscular responses to explosive and heavy resistance loading.

The EMG power spectrum may shift towards higher frequencies with higher movement velocities. Fatigue, on the other hand, can cause a decrease in the frequency components. The purpose of this study was to examine acute effects of explosive (EE) and heavy resistance (HRE) concentric leg press exercise on muscle force, EMG and blood lactate. The EE included five sets of ten repetitions with 40+/-6% of the isometric maximum at a 100 degrees knee angle performed as explosively as possible. The same number of repetitions was performed in HRE but with a heavier load (67+/-7% of the isometric maximum at a 100 degrees knee angle). Maximal isometric and single concentric actions of different loads, and an isometric fatigue test were measured before and after both exercises. Surface EMG was recorded from the vastus medialis muscles for analyses of average EMG (aEMG) and EMG power spectrum. Muscle fiber composition of the vastus lateralis was determined and blood lactate measured throughout the exercises. Mean power frequency and median frequency were higher during EE than during HRE (P<0.05). They increased during EE (P<0.05) as the exercise progressed, whereas during HRE no change or even slight decreases were observed. Signs of fatigue after pure concentric work were not observed after EE, and even after HRE, possibly due to the relatively small range of motion and short duration of action time, the fatigue was not that extensive. The relative number of fast twitch fibers was correlated (r=0.87, P<0.05) with the change in blood lactate in HRE. It was concluded that there may be a greater use of fast twitch motor units in explosive movements and that instead of fatigue, the present number of concentric actions in explosive exercise seems to have facilitated the neuromuscular system.

Adult↗
PubMed2000

Lithium poisoning from a poison control center perspective.

The purpose of this study was to evaluate the severity of lithium poisoning from a poison control center-based population and the correlation of the Hansen and Amdisen classification with outcome and lithium levels in that setting. All lithium overdoses brought to the attention of the poison control center were prospectively observed during 1 year. Demographic data, amount ingested, coingestants, symptoms and signs, lithium levels, treatment, and outcome were recorded. There were 12 acute lithium overdoses: 5, 5, and 2 with grade 0, 1, and 2, respectively. No patients required hemodialysis or had sequelae or died. There were 174 acute-on-chronic overdoses: 66, 85, 15, and 8 with grade 0, 1, 2, and 3, respectively. Six patients underwent hemodialysis; none had sequelae but one died. There were 19 chronic poisonings: 9, 9, and 1 with grade 1, 2, and 3, respectively. Three patients underwent hemodialysis; one had sequelae and one died. Patients classified as grade 2 had higher lithium levels than those with grade 1 in patients with only lithium poisoning (3.08 +/- 0.77 vs. 2.09 +/- 0.91 mmol/L P = 0.03). The study concluded that morbidity (0.5%) and mortality (1%) associated with lithium poisoning are rarely observed. The Hansen and Amdisen classification does not appear to be a useful clinical tool to predict either morbidity or mortality and does not correlate well with lithium levels.

Acute Disease↗
PubMed2000

Comparison of patients hemodialyzed for lithium poisoning and those for whom dialysis was recommended by PCC but not done: what lesson can we learn?

AIMS: To compare patients for whom hemodialysis was done for lithium poisoning and those for whom it was recommended by the poison control centre (PCC) but not done and to evaluate the effect of withholding hemodialysis on outcomes. METHODS: All lithium overdoses brought to the attention of the PCC were prospectively followed from January 1 to December 31, 1996. Patients for whom hemodialysis was done were compared with those for whom it was recommended but not done in terms of clinical presentation, lithium elimination half-life, need for transfer to another centre for hemodialysis, and outcome (death, or sequel or recovery). RESULTS: A total of 205 cases of lithium overdoses were collected including 110 with levels higher than 1.5 mmol/l. There were 12 acute lithium overdoses; no patients required hemodialysis and there were no sequel or deaths. There were 174 acute on chronic overdoses; hemodialysis was recommended in 9 patients but only 6 underwent hemodialysis; one patient died during hemodialysis but no other had sequel. There were 19 chronic poisonings; hemodialysis was recommended in 9 patients but only 2 had hemodialysis, a third patient underwent hemodialysis despite it not being recommended; one patient died without hemodialysis and one other had sequel after hemodialysis. No difference were observed between the groups for age, sex, type of poisoning (acute on chronic/chronic), levels (initial/peak/6 hours/extrapolated at 30 hours), time of presentation post-ingestion, presence of co-ingestants, symptoms and signs, Hansen and Amdisen grade, initial creatinine, time of recommendation to perform hemodialysis (daytime or nighttime), need to transfer patients to another centre to perform hemodialysis, and outcome. Patients with acute on chronic poisoning that were not hemodialyzed had longer elimination half-life than those for whom hemodialysis was done even before hemodialysis was performed: 50.1 +/- 13.6 h (n = 3) versus 12.9 +/-12.1 (n = 3) (p = 0.007), respectively. CONCLUSION: No difference was observed between patients for whom hemodialysis was done and those for whom it was recommended by PCC but not done. Despite the death of one patient clearly associated with voluntary withholding hemodialysis, sequel was not seen in that group. The indications for hemodialysis in lithium poisoning should be reconsidered to include only the more severe cases.

Adult↗
PubMed1997

Position statement: ipecac syrup. American Academy of Clinical Toxicology; European Association of Poisons Centres and Clinical Toxicologists.

In preparing this Position Statement, all relevant scientific literature was identified and reviewed critically by acknowledged experts using agreed criteria. Well-conducted clinical and experimental studies were given precedence over anecdotal case reports and abstracts were not usually considered. A draft Position Statement was then produced and subjected to detailed peer review by an international group of clinical toxicologists chosen by the American Academy of Clinical Toxicology and the European Association of Poisons Centres and Clinical Toxicologists. The Position Statement went through multiple drafts before being approved by the boards of the two societies and being endorsed by other societies. The Position Statement includes a summary statement for ease of use and is supported by detailed documentation which describes the scientific evidence on which the Statement is based. Syrup of ipecac should not be administered routinely in the management of poisoned patients. In experimental studies the amount of marker removed by ipecac was highly variable and diminished with time. There is no evidence from clinical studies that ipecac improves the outcome of poisoned patients and its routine administration in the emergency department should be abandoned. There are insufficient data to support or exclude ipecac administration soon after poison ingestion. Ipecac may delay the administration or reduce the effectiveness of activated charcoal, oral antidotes, and whole bowel irrigation. Ipecac should not be administered to a patient who has a decreased level or impending loss of consciousness or who has ingested a corrosive substance or hydrocarbon with high aspiration potential.

Acetaminophen↗
PubMed1997

Position statement: cathartics. American Academy of Clinical Toxicology; European Association of Poisons Centres and Clinical Toxicologists.

In preparing this Position Statement, all relevant scientific literature was identified and reviewed critically by acknowledged experts using agreed criteria. Well-conducted clinical and experimental studies were given precedence over anecdotal case reports and abstracts were not usually considered. A draft Position Statement was then produced and subjected to detailed peer review by an international group of clinical toxicologists chosen by the American Academy of Clinical Toxicology and the European Association of Poisons Centres and Clinical Toxicologists. The Position Statement went through multiple drafts before being approved by the Boards of the two societies and being endorsed by other societies. The Position Statement includes a summary statement for ease of use and is supported by detailed documentation which describes the scientific evidence on which the Statement is based. The administration of a cathartic alone has no role in the management of the poisoned patient and is not recommended as a method of gut decontamination. Experimental data are conflicting regarding the use of cathartics in combination with activated charcoal. No clinical studies have been published to investigate the ability of a cathartic, with or without activated charcoal, to reduce the bioavailability of drugs or to improve the outcome of poisoned patients. Based on available data, the routine use of a cathartic in combination with activated charcoal is not endorsed. If a cathartic is used, it should be limited to a single dose in order to minimize adverse effects.

Animals↗
PubMed1994

Acute digoxin overdose in a newborn with renal failure: use of digoxin immune Fab and peritoneal dialysis.

Digitalis intoxication is a common problem, mainly because of the narrow margin of safety of digoxin. These patients may have concomitant renal failure. In patients who have renal failure and who have been treated with digoxin-Fab, the elimination of the digoxin-Fab complex is significantly delayed, and there is a risk of dissociation of the complex with rebound of free digoxin and recurrence of toxicity. The high molecular weight of digoxin and digoxin-Fab complex prevents its elimination by hemodialysis or continuous arteriovenous hemofiltration. A 3-day-old newborn with digoxin overdose and acute renal failure was treated with digoxin immune Fab and peritoneal dialysis. Low levels of total digoxin were measured in the dialyzate, indicating poor elimination of the digoxin-Fab complex through peritoneal dialysis.

Acute Kidney Injury↗