Metabolic acidosis and coma following a severe acetaminophen overdose

OBJECTIVE

To report a case of metabolic acidosis and coma in a severe acetaminophen overdose.

CASE SUMMARY

A 29-year-old white woman was admitted to the emergency department with a diminished level of consciousness and metabolic acidosis. The toxicology screen revealed a serum acetaminophen concentration of 1072 microg/mL, and she was consequently treated with intravenous acetylcysteine. Despite the elevated concentration, the patient did not manifest signs of hepatotoxicity.

DISCUSSION

Metabolic acidosis and coma are rare manifestations in acetaminophen overdoses. In published case reports, severe acetaminophen ingestion independently causes metabolic acidosis and coma in the absence of hepatotoxicity. The mechanism by which metabolic acidosis occurs is not clearly defined. Studies conducted on animals demonstrated that in severe overdoses, acetaminophen may cause lactic acidosis by inhibiting mitochondrial respiration. The mechanism by which acetaminophen can cause coma is still unknown.

CONCLUSIONS

Severe acetaminophen overdoses can independently cause metabolic acidosis and coma in the absence of hepatotoxicity.

Efficacy and safety of intravenous phosphate replacement in critically ill patients

OBJECTIVE

To evaluate the efficacy and safety of intravenous potassium phosphate administered in a fixed-dose regimen in critically ill patients.

DESIGN

Prospective, unblind study.

SETTING

Surgical-medical intensive care unit (ICU).

PARTICIPANTS

Patients who developed hypophosphatemia during their ICU admission.

INTERVENTIONS

Patients with a serum phosphate concentration between 1.27 and 2.48 mg/dL (group 1) and those with a concentration of 1.24 mg/dL or less (group 2) received 15 and 30 mmol, respectively, of phosphate as a potassium salt via a central line over 3 hours.

MAIN OUTCOME MEASURES

Normalization of serum phosphate within 6 hours of infusion, the development of arrhythmias during the infusion, and the development of hypocalcemia and hyperkalemia after the infusion were evaluated. Redevelopment of hypophosphatemia and the need for further therapy were also assessed.

RESULTS

Thirty-seven episodes of hypophosphatemia were entered in this study: 27 in group 1 (17 patients) and 10 in group 2 (10 patients). The mean serum phosphate concentration increased significantly from 2.02 to 2.82 mg/dL in group 1 and from 0.83 to 2.17 mg/dL in group 2, with no change in calcium or potassium. Normalization of serum phosphate with this initial dose occurred in 81.5% of the episodes in group 1 and 30% in group 2. However, over the following 2 days, 45% of the patients in group 1 and 60% in group 2 required further phosphate supplementation. No arrhythmias occurred during the 3-hour infusion that were related to the potassium phosphate. A significant drop in total serum calcium concentrations occurred in 2 patients who were slightly hypercalcemic prior to the infusion. Serum calcium concentrations remained above normal, but this was not associated with any adverse effects.

CONCLUSIONS

The administration of potassium phosphate 15 mmol to critically ill patients with mild-to-moderate hypophosphatemia over 3 hours is both effective and safe. The administration of potassium phosphate 30 mmol to severely hypophosphatemic patients was safe but achieved normalization of serum phosphate in a minority of patients. Either a higher dose or the subsequent administration of more potassium phosphate may be required to normalize serum phosphate concentrations. Once normalization has occurred, there is a high likelihood of redevelopment of hypophosphatemia over the following 2 days and supplementation should be given accordingly.

Effect of sodium polystyrene sulfonate on lithium bioavailability

STUDY OBJECTIVE

To examine the effect of a single dose of sodium polystyrene sulfonate and sorbitol on lithium absorption.

DESIGN

Prospective, randomized, crossover.

SETTING

University teaching hospital.

TYPE OF PARTICIPANTS

Healthy volunteers.

INTERVENTIONS

Subjects ingested 600 mg lithium carbonate on two occasions, with and without 30 g concomitant sodium polystyrene sulfonate. Blood samples were drawn up to 24 hours after ingestion and assayed for serum lithium concentration.

MEASUREMENTS AND MAIN RESULTS

Compared with control, sodium polystyrene sulfonate and sorbitol reduced the area under the lithium serum concentration-time curve by 11.33%, reduced the mean observed peak serum lithium concentration 0.07 +/- 0.08 mmol/L, and delayed the time to the mean observed peak serum lithium concentration by 2.04 +/- 2.40 hours.

CONCLUSION

Sodium polystyrene sulfonate and sorbitol may be used in patients immediately or shortly after ingestion of a significant acute overdose of lithium in situations in which hemodialysis cannot be instituted promptly.

Acute Intoxications: Cases presenting to an adult emergency department

Cases of acute substance intoxication presenting to the Emergency Department of the Ottawa General Hospital from 1986 to 1988 were retrospectively analyzed. Of the 1001 cases, 55% were female patients; the mean age was 34 years; 51% were admitted to hospital; 65% ingested more than one drug substance; and ethanol was involved in 27% of cases. There were 10 deaths.

Pharmacokinetic consultation service workload measurement study

A study was conducted to collect work measurement data for pharmacokinetic drug consultation services. A stopwatch was used to measure the time required to perform pharmacokinetic consultations in the Ottawa General Hospital, a 530-bed tertiary care teaching hospital. Ten pharmacists provided 166 drug consults primarily for phenytoin, aminoglycosides, digoxin, and theophylline. The time required to obtain drug level measurements averaged 1.10 minutes. Consults required an average of 8.28 (SD = 4.72) minutes. Initial consults took 10.35 (SD = 5.07) minutes, while repeat consults took 6.62 (SD = 3.67) minutes. The difference was significant (t = 5.48, df = 164, P less than 0.001). No significant differences were found among consults for different drugs nor between primary and secondary patient coverage areas. There was a significant difference in the time required to perform a consult among pharmacists. Consult times were considerably less than those reported by the Canadian Hospital Pharmacy Workload Measurement Study.

Compliance among adults with cystic fibrosis

Advances in therapy have largely contributed to the increased life expectancy of patients with cystic fibrosis. Unlike children, adults with cystic fibrosis must take responsibility for their own care. We administered a questionnaire to 23 adult patients (aged 18-39 years) with cystic fibrosis to (1) determine patients' degree of compliance with medications and chest physiotherapy; (2) collect information on their self-assessment of health motivation, disease severity, and benefits of treatment; and (3) identify barriers to receiving medical care. Patients reported better compliance with medications than with chest physiotherapy. Nine percent of the patients missed at least 25 percent of prescribed medication, whereas 47 percent missed at least 25 percent of prescribed physiotherapy. We observed a trend toward better compliance in patients who were highly worried about their health, who believed their illness to be serious, and who felt that their medications were very effective. Less than half of the study participants believed physiotherapy to be effective, and that adhering to a physiotherapy schedule was very difficult. Among adults with cystic fibrosis, compliance can be a serious problem that minimizes the benefits of good medical care. We suggest that emphasizing the severity of disease and usefulness of therapy may improve compliance and requires study.

Evaluation of the validity of the Done nomogram in the management of acute salicylate intoxication

To evaluate the validity of the Done nomogram in the management of acute adult salicylate intoxications, a retrospective review of cases at our institution was performed. The degree of severity (ie, asymptomatic, mild, moderate, or severe) as determined by plotting the serum concentration and time on the nomogram for 55 acute salicylate intoxications was compared with the degree of severity decided on by three experienced emergency physicians who based their decision on the clinical presentation of the cases and the original criteria devised by Done for each category of severity. Discordant classifications between the nomogram and the physicians provided a basis on which a predictive index for the nomogram and various subsets of cases could be determined. The calculated predictive index for the nomogram was 0.42, with the highest predictive index of 0.79 in the mild salicylate category. The nomogram tends to overpredict the severity of intoxication in the moderate and severe categories. There was no significant difference between predictive indexes of mixed versus nonmixed or enteric-coated acetylsalicylic acid versus plain acetylsalicylic acid cases, although the nomogram had a higher predictive index when used for concentrations drawn six to 12 hours after ingestion (P less than .01, Fisher's exact test). Decisions on management of an acute salicylate overdose should be based on clinical presentation and good judgment as well as the serum salicylate concentration in relation to the time of ingestion.

An evaluation of the effect of repeated doses of oral activated charcoal on salicylate elimination

The authors investigated the effect of repeated doses of oral activated charcoal on salicylate elimination in six healthy volunteers. On two occasions (phase I and phase II; separated by one week) each subject received 1300 mg of aspirin as an aqueous solution. On the second occasion (phase II) each subject also received a total dose of 55 g of aqueous activated charcoal initiated 4 hours after salicylate administration (25 g initial dose, followed by three 10 g doses at two hour intervals). Serum salicylate levels were measured from one to twelve hours post aspirin ingestion. The pharmacokinetic analysis showed no significant change between phase I and phase II for either the salicylate elimination half-life or the area under the concentration versus time curve from 4-12 hours post aspirin ingestion. Reasons for the lack of effect of repeated doses of charcoal on salicylate elimination are discussed and, these results cannot necessarily be extrapolated to the overdose situation. Further investigation is warranted to assess the effect of repeated doses of activated charcoal in the salicylate-overdosed patient.

Evaluation of the effect of norfloxacin on the pharmacokinetics of theophylline

To investigate a possible interaction between norfloxacin and theophylline, eight healthy nonsmoking volunteers (mean age 27 +/- 5.3 years) were administered aminophylline, 5 mg/kg, before and after a 6-day course of norfloxacin, 400 mg every 12 hours, and changes in pharmacokinetic parameters were measured and compared. Norfloxacin induced significant decreases in theophylline clearance (14.9%; p less than 0.01) and the terminal phase slope (13.3%; p less than 0.02) and increased the AUC (16.6%; p less than 0.01). The apparent volume of distribution at steady state was unchanged. The greatest norfloxacin-induced individual change in theophylline clearance was a reduction of 28.6%. Given these findings, we advise that, for patients who are treated with theophylline and are subsequently treated with norfloxacin, adjustment of the theophylline dosage may be necessary in some patients to minimize the risk of theophylline toxicity.

An evaluation of a pharmacy based aminoglycoside monitoring service

The impact of a pharmacy based aminoglycoside serum concentration monitoring service is reported. Physician responses to serum concentrations were assessed before and after the introduction of the service and the results compared. Eighty-four percent of recommendations made by pharmacists to physicians were totally accepted and the response to serum concentrations significantly improved after the introduction of the clinical pharmacokinetic service. Such a service provides a valuable function and is well accepted by the physicians.