Salicylate poisoning

Last updated
Salicylate poisoning
Other namesSalicylism, salicylate toxicity, aspirin poisoning, aspirin toxicity, aspirin overdose
Aspirin-skeletal.svg
A skeletal structural formula for aspirin.
Specialty Emergency medicine
Symptoms Ringing in the ears, nausea, abdominal pain, fast breathing rate [1]
Complications Swelling of the brain or lungs, seizures, low blood sugar, cardiac arrest [1]
Diagnostic method Early: Slightly elevated blood aspirin levels ~ 2.2 mmol/L (30 mg/dL, 300 mg/L), respiratory alkalosis [1]
Late: Metabolic acidosis [1]
Differential diagnosis Sepsis, heart attack, agitation [1]
Prevention Child-resistant packaging, low number of pills per package [1]
Treatment Activated charcoal, intravenous sodium bicarbonate with dextrose and potassium chloride, dialysis [2]
Prognosis ~1% risk of death [3]
Frequency> 20,000 per year (US) [1]

Salicylate poisoning, also known as aspirin poisoning, is the acute or chronic poisoning with a salicylate such as aspirin. [1] The classic symptoms are ringing in the ears, nausea, abdominal pain, and a fast breathing rate. [1] Early on, these may be subtle, while larger doses may result in fever. [1] [4] Complications can include swelling of the brain or lungs, seizures, low blood sugar, or cardiac arrest. [1]

Contents

While usually due to aspirin, other possible causes include oil of wintergreen and bismuth subsalicylate. [2] Excess doses can be either on purpose or accidental. [1] Small amounts of oil of wintergreen can be toxic. [2] Diagnosis is generally based on repeated blood tests measuring aspirin levels and blood gases. [1] While a type of graph has been created to try to assist with diagnosis, its general use is not recommended. [1] In overdose maximum blood levels may not occur for more than 12 hours. [2]

Efforts to prevent poisoning include child-resistant packaging and a lower number of pills per package. [1] Treatment may include activated charcoal, intravenous sodium bicarbonate with dextrose and potassium chloride, and dialysis. [2] Giving dextrose may be useful even if the blood sugar is normal. [2] Dialysis is recommended in those with kidney failure, decreased level of consciousness, blood pH less than 7.2, or high blood salicylate levels. [2] If a person requires intubation, a fast respiratory rate may be required. [1]

The toxic effects of salicylates have been described since at least 1877. [5] In 2004, more than 20,000 cases with 43 deaths were reported in the United States. [1] About 1% of those with an acute overdose die, while chronic overdoses may have severe outcomes. [3] Older people are at higher risks of toxicity for any given dose. [5]

Signs and symptoms

Main symptoms of aspirin overdose Symptoms of aspirin overdose.svg
Main symptoms of aspirin overdose

Salicylate toxicity has potentially serious consequences, sometimes leading to significant morbidity and death. Patients with mild intoxication frequently have nausea and vomiting, abdominal pain, lethargy, ringing in the ears, and dizziness. More significant signs and symptoms occur in more severe poisonings and include high body temperature, fast breathing rate, respiratory alkalosis, metabolic acidosis, low blood potassium, low blood glucose, hallucinations, confusion, seizure, cerebral edema, and coma. The most common cause of death following an aspirin overdose is cardiopulmonary arrest usually due to pulmonary edema. [7]

High doses of salicylate can cause salicylate-induced tinnitus. [8]

Severity

The severity of toxicity depends on the amount of aspirin taken.

SeverityMild (150 mg per kg of body mass)Moderate (150–300 mg per kg of body mass)Severe (300–500 mg per kg of body mass)
ToxicityNo toxicity expectedMild to moderate toxicity expectedLife-threatening toxicity expected
Symptoms Nausea, vomiting, dizziness Nausea, vomiting, ringing in the ears, headache, confusion, hyperventilation, tachycardia, fever Delirium, hallucinations, seizures, coma, respiratory arrest

Pathophysiology

High levels of salicylates stimulate peripheral chemoreceptors and the central respiratory centers in the medulla causing increased ventilation and respiratory alkalosis. [9] The increased pH secondary to hyperventilation with respiratory alkalosis causes an increase in lipolysis and ketogenesis which causes the production of lactate and organic keto-acids (such as beta-hydroxybutyrate). [9] The accumulation of these organic acids can cause an acidosis with an increased anion gap as well as a decreased buffering capacity of the body. [9] Salicylate toxicity also causes an uncoupling of oxidative phosphorylation and a decrease in citric acid cycle activity in the mitochondria. [9] This decrease in aerobic production of adenosine triphosphate (ATP) is accompanied by an increase in anaerobic production of ATP through glycolysis which leads to glycogen depletion and hypoglycemia. [9] The inefficient ATP production through anaerobic metabolism causes the body to shift to a catabolic predominant mode for energy production which consists of increased oxygen consumption, increased heat production (often manifesting as sweating), liver glycogen utilization and increased carbon dioxide production. [9] This increased catabolism accompanied by hyperventilation can lead to severe insensible water losses, dehydration and hypernatremia. [9]

Acute aspirin or salicylates overdose or poisoning can cause initial respiratory alkalosis though metabolic acidosis ensues thereafter. The acid-base, fluid, and electrolyte abnormalities observed in salicylate toxicity can be grouped into three broad phases:

Diagnosis

The acutely toxic dose of aspirin is generally considered greater than 150 mg per kg of body mass. [12] Moderate toxicity occurs at doses up to 300 mg/kg, severe toxicity occurs between 300 and 500 mg/kg, and a potentially lethal dose is greater than 500 mg/kg. [13] Chronic toxicity may occur following doses of 100 mg/kg per day for two or more days. [13]

Monitoring of biochemical parameters such as electrolytes and solutes, liver and kidney function, urinalysis, and complete blood count is undertaken along with frequent checking of salicylate and blood sugar levels. Arterial blood gas assessments typically find respiratory alkalosis early in the course of the overdose due to hyperstimulation of the respiratory center, and may be the only finding in a mild overdose. An anion-gap metabolic acidosis occurs later in the course of the overdose, especially if it is a moderate to severe overdose, due to the increase in protons (acidic contents) in the blood.

The diagnosis of poisoning usually involves measurement of plasma salicylate, the active metabolite of aspirin, by automated spectrophotometric methods. Plasma salicylate levels generally range from 30–100 mg/L (3–10 mg/dL) after usual therapeutic doses, 50–300 mg/L in patients taking high doses, and 700–1400 mg/L following acute overdose. [14] Patients may undergo repeated testing until their peak plasma salicylate level can be estimated. [15] Optimally, plasma levels should be assessed four hours after ingestion and then every two hours after that to allow calculation of the maximum level, which can then be used as a guide to the degree of toxicity expected. [16] Patients may also be treated according to their individual symptoms.

Prevention

A bottle of aspirin with a child-resistant cap bearing the instruction "push down and turn to open" Aspirin1.jpg
A bottle of aspirin with a child-resistant cap bearing the instruction "push down and turn to open"

Efforts to prevent poisoning include child-resistant packaging and a lower number of pills per package. [1]

Treatment

There is no antidote for salicylate poisoning. [9] Initial treatment of an overdose involves resuscitation measures such as maintaining an adequate airway and adequate circulation followed by gastric decontamination by administering activated charcoal, which adsorbs the salicylate in the gastrointestinal tract. [9] Stomach pumping is no longer routinely used in the treatment of poisonings, but is sometimes considered if the patient has ingested a potentially lethal amount less than one hour before presentation. [17] Inducing vomiting with syrup of ipecac is not recommended. [12] Repeated doses of activated charcoal have been proposed to be beneficial in cases of salicylate poisoning, [18] especially in ingestion of enteric coated and extended release salicylic acid formulations which are able to remain in the gastrointestinal (GI) tract for longer periods of time. [9] Repeated doses of activated charcoal are also useful to re-adsorb salicylates in the GI tract that may have desorbed from the previous administration of activated charcoal. [9] The initial dose of activated charcoal is most useful if given within 2 hours of initial ingestion. [9] Contraindications to the use of activated charcoal include altered mental status (due to the risk of aspiration), GI bleeding (often due to salicylates) or poor gastric motility. [9] Whole bowel irrigation using the laxative polyethylene glycol can be useful to induce the gastrointestinal elimination of salicylates, particularly if there is partial or diminished response to activated charcoal. [9]

Alkalinization of the urine and plasma, by giving a bolus of sodium bicarbonate then adding sodium bicarbonate to maintenance fluids, is an effective method to increase the clearance of salicylates from the body. [9] Alkalinization of the urine causes salicylates to be trapped in renal tubules in their ionized form and then readily excreted in the urine. Alkalinization of the urine increases urinary salicylate excretion by 18 fold. [9] Alkalinization of the plasma decreases the lipid soluble form of salicylates facilitating movement out of the central nervous system. [9] Oral sodium bicarbonate is contra-indicated in salicylate toxicity as it can cause dissociation of salicylate tablets in the GI tract and subsequent increased absorption. [9]

Intravenous fluids

Intravenous fluids containing dextrose such as dextrose 5% in water (D5W) are recommended to keep a urinary output between 1 and 1.5 millilitres per kilogram per hour. [9]

Sodium bicarbonate is given in a significant aspirin overdose (salicylate level greater than 35 mg/dL 6 hours after ingestion) regardless of the serum pH, as it enhances elimination of aspirin in the urine. It is given until a urine pH between 7.5 and 8.0 is achieved. [19]

Dialysis

Hemodialysis can be used to enhance the removal of salicylate from the blood, usually in those who are severely poisoned. Examples of severe poisoning include people with high salicylate blood levels: 7.25 mmol/L (100 mg/dL) in acute ingestions or 40 mg/dL in chronic ingestions, [19] significant neurotoxicity (agitation, coma, convulsions), kidney failure, pulmonary edema, or cardiovascular instability. [15] Hemodialysis also has the advantage of restoring electrolyte and acid-base abnormalities while removing salicylate. [20]

Salicylic acid has a small size (low molecular mass), has a low volume of distribution (is more water soluble), has low tissue binding and is largely free (and not protein bound) at toxic levels in the body; all of which make it easily removable from the body by hemodialysis. [9]

Indication for dialysis:

  1. Salicylate level higher than 90 mg/dL (6.5 mmol/L) [9]
  2. Severe acid–base imbalance
  3. Severe cardiac toxicity
  4. Acute respiratory distress syndrome [9]
  5. Cerebral involvement / neurological signs and symptoms
  6. Rising serum salicylate level despite alkalinization/multidose activated charcoal, or people in which standard approaches to treatment have failed [9]
  7. Unable to tolerate fluids with fluid overload

Epidemiology

Acute salicylate toxicity usually occurs after an intentional ingestion by younger adults, often with a history of psychiatric disease or previous overdose, whereas chronic toxicity usually occurs in older adults who experience inadvertent overdose while ingesting salicylates therapeutically over longer periods of time. [9]

During the latter part of the 20th century, the number of poisonings from salicylates declined, mainly because of the increased popularity of other over-the-counter analgesics such as paracetamol (acetaminophen). Fifty-two deaths involving single-ingredient aspirin were reported in the United States in 2000; however, in all but three of these cases, the reason for the ingestion of lethal doses was intentional—predominantly suicidal. [21]

History

Aspirin poisoning has been cited as a possible driver of the high mortality rate during the 1918 flu pandemic, which killed 50 to 100 million people. [22]

See also

Related Research Articles

<span class="mw-page-title-main">Aspirin</span> Medication

Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and inflammation, and as an antithrombotic. Specific inflammatory conditions that aspirin is used to treat include Kawasaki disease, pericarditis, and rheumatic fever.

<span class="mw-page-title-main">Strychnine</span> Poisonous substance used as pesticide

Strychnine is a highly toxic, colorless, bitter, crystalline alkaloid used as a pesticide, particularly for killing small vertebrates such as birds and rodents. Strychnine, when inhaled, swallowed, or absorbed through the eyes or mouth, causes poisoning which results in muscular convulsions and eventually death through asphyxia. While it is no longer used medicinally, it was used historically in small doses to strengthen muscle contractions, such as a heart and bowel stimulant and performance-enhancing drug. The most common source is from the seeds of the Strychnos nux-vomica tree.

Iron poisoning typically occurs from ingestion of excess iron that results in acute toxicity. Mild symptoms which occur within hours include vomiting, diarrhea, abdominal pain, and drowsiness. In more severe cases, symptoms can include tachypnea, low blood pressure, seizures, or coma. If left untreated, acute iron poisoning can lead to multi-organ failure resulting in permanent organ damage or death.

Acidosis is a biological process producing hydrogen ions and increasing their concentration in blood or body fluids. pH is the negative log of hydrogen ion concentration and so it is decreased by a process of acidosis.

<span class="mw-page-title-main">Alcoholic ketoacidosis</span> Medical condition

Alcoholic ketoacidosis (AKA) is a specific group of symptoms and metabolic state related to alcohol use. Symptoms often include abdominal pain, vomiting, agitation, a fast respiratory rate, and a specific "fruity" smell. Consciousness is generally normal. Complications may include sudden death.

<span class="mw-page-title-main">Metabolic acidosis</span> Imbalance in the bodys acid-base equilibrium

Metabolic acidosis is a serious electrolyte disorder characterized by an imbalance in the body's acid-base balance. Metabolic acidosis has three main root causes: increased acid production, loss of bicarbonate, and a reduced ability of the kidneys to excrete excess acids. Metabolic acidosis can lead to acidemia, which is defined as arterial blood pH that is lower than 7.35. Acidemia and acidosis are not mutually exclusive – pH and hydrogen ion concentrations also depend on the coexistence of other acid-base disorders; therefore, pH levels in people with metabolic acidosis can range from low to high.

<span class="mw-page-title-main">Respiratory acidosis</span> Decrease in blood pH due to insufficient breathing

Respiratory acidosis is a state in which decreased ventilation (hypoventilation) increases the concentration of carbon dioxide in the blood and decreases the blood's pH.

<span class="mw-page-title-main">Nicotine poisoning</span> Medical condition

Nicotine poisoning describes the symptoms of the toxic effects of nicotine following ingestion, inhalation, or skin contact. Nicotine poisoning can potentially be deadly, though serious or fatal overdoses are rare. Historically, most cases of nicotine poisoning have been the result of use of nicotine as an insecticide. More recent cases of poisoning typically appear to be in the form of Green Tobacco Sickness, or due to unintended ingestion of tobacco or tobacco products or consumption of nicotine-containing plants.

<span class="mw-page-title-main">Respiratory alkalosis</span> Increase in blood pH due to rapid breathing

Respiratory alkalosis is a medical condition in which increased respiration elevates the blood pH beyond the normal range (7.35–7.45) with a concurrent reduction in arterial levels of carbon dioxide. This condition is one of the four primary disturbance of acid–base homeostasis.

<span class="mw-page-title-main">Metabolic alkalosis</span> Abnormally high tissue pH due to metabolic dysfunction

Metabolic alkalosis is an acid-base disorder in which the pH of tissue is elevated beyond the normal range (7.35–7.45). This is the result of decreased hydrogen ion concentration, leading to increased bicarbonate, or alternatively a direct result of increased bicarbonate concentrations. The condition typically cannot last long if the kidneys are functioning properly.

In physiology, base excess and base deficit refer to an excess or deficit, respectively, in the amount of base present in the blood. The value is usually reported as a concentration in units of mEq/L (mmol/L), with positive numbers indicating an excess of base and negative a deficit. A typical reference range for base excess is −2 to +2 mEq/L.

Zinc toxicity is a medical condition involving an overdose on, or toxic overexposure to, zinc. Such toxicity levels have been seen to occur at ingestion of greater than 50 mg of zinc. Excessive absorption of zinc can suppress copper and iron absorption. The free zinc ion in solution is highly toxic to bacteria, plants, invertebrates, and even vertebrate fish. Zinc is an essential trace metal with very low toxicity in humans.

Acid–base homeostasis is the homeostatic regulation of the pH of the body's extracellular fluid (ECF). The proper balance between the acids and bases in the ECF is crucial for the normal physiology of the body—and for cellular metabolism. The pH of the intracellular fluid and the extracellular fluid need to be maintained at a constant level.

Ethylene glycol poisoning is poisoning caused by drinking ethylene glycol. Early symptoms include intoxication, vomiting and abdominal pain. Later symptoms may include a decreased level of consciousness, headache, and seizures. Long term outcomes may include kidney failure and brain damage. Toxicity and death may occur after drinking even in a small amount as ethylene glycol is more toxic than other diols.

<span class="mw-page-title-main">Paracetamol poisoning</span> Toxicity due to paracetamol overdose

Paracetamol poisoning, also known as acetaminophen poisoning, is caused by excessive use of the medication paracetamol (acetaminophen). Most people have few or non-specific symptoms in the first 24 hours following overdose. These symptoms include feeling tired, abdominal pain, or nausea. This is typically followed by absence of symptoms for a couple of days, after which yellowish skin, blood clotting problems, and confusion occurs as a result of liver failure. Additional complications may include kidney failure, pancreatitis, low blood sugar, and lactic acidosis. If death does not occur, people tend to recover fully over a couple of weeks. Without treatment, death from toxicity occurs 4 to 18 days later.

<span class="mw-page-title-main">High anion gap metabolic acidosis</span> Medical condition

High anion gap metabolic acidosis is a form of metabolic acidosis characterized by a high anion gap. Metabolic acidosis occurs when the body produces too much acid, or when the kidneys are not removing enough acid from the body. Several types of metabolic acidosis occur, grouped by their influence on the anion gap.

<span class="mw-page-title-main">Tricyclic antidepressant overdose</span> Medical condition

Tricyclic antidepressant overdose is poisoning caused by excessive medication of the tricyclic antidepressant (TCA) type. Symptoms may include elevated body temperature, blurred vision, dilated pupils, sleepiness, confusion, seizures, rapid heart rate, and cardiac arrest. If symptoms have not occurred within six hours of exposure they are unlikely to occur.

<span class="mw-page-title-main">Barbiturate overdose</span> Medical condition

Barbiturate overdose is poisoning due to excessive doses of barbiturates. Symptoms typically include difficulty thinking, poor coordination, decreased level of consciousness, and a decreased effort to breathe. Complications of overdose can include noncardiogenic pulmonary edema. If death occurs this is typically due to a lack of breathing.

<span class="mw-page-title-main">Intravenous sodium bicarbonate</span> Pharmaceutical drug

Intravenous sodium bicarbonate, also known as sodium hydrogen carbonate, is a medication primarily used to treat severe metabolic acidosis. For this purpose it is generally only used when the pH is less than 7.1 and when the underlying cause is either diarrhea, vomiting, or the kidneys. Other uses include high blood potassium, tricyclic antidepressant overdose, and cocaine toxicity as well as a number of other poisonings. It is given by injection into a vein.

<span class="mw-page-title-main">Lithium toxicity</span> Medical condition

Lithium toxicity, also known as lithium overdose, is the condition of having too much lithium. Symptoms may include a tremor, increased reflexes, trouble walking, kidney problems, and an altered level of consciousness. Some symptoms may last for a year after levels return to normal. Complications may include serotonin syndrome.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 O'Malley, GF (May 2007). "Emergency department management of the salicylate-poisoned patient". Emergency Medicine Clinics of North America. 25 (2): 333–46, abstract viii. doi:10.1016/j.emc.2007.02.012. PMID   17482023.
  2. 1 2 3 4 5 6 7 Walls, Ron (2017). Rosens Emergency Medicine Concepts and Clinical Practice (9th ed.). Elsevier. p. X. ISBN   978-0323354790.
  3. 1 2 McNeil Consumer & Specialty Pharmaceuticals (2002). "Assessment of Safety of aspirin and other Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)". FDA. Archived from the original on 14 May 2017. Retrieved 27 June 2017.
  4. Brenner, George M.; Stevens, Craig (2012). Pharmacology E-Book: with STUDENT CONSULT Online Access (4 ed.). Elsevier Health Sciences. p. 319. ISBN   978-1455702787. Archived from the original on 2017-08-18.
  5. 1 2 Roland, Peter S.; Rutka, John A. (2004). Ototoxicity. PMPH-USA. p. 28. ISBN   9781550092639. Archived from the original on 10 September 2017. Retrieved 27 June 2017.
  6. MedlinePlus > Aspirin Archived 2009-07-20 at the Wayback Machine Last Reviewed - 02/01/2009.
  7. Thisted, B; Krantz, T; Strøom, J; Sørensen, MB (May 1987). "Acute salicylate self-poisoning in 177 consecutive patients treated in ICU". Acta Anaesthesiologica Scandinavica. 31 (4): 312–6. doi:10.1111/j.1399-6576.1987.tb02574.x. ISSN   0001-5172. PMID   3591255. S2CID   21769646.
  8. Stolzberg, Daniel (20 April 2012). "Salicylate toxicity model of tinnitus". Frontiers in Systems Neuroscience. 6: 28. doi: 10.3389/fnsys.2012.00028 . PMC   3341117 . PMID   22557950.
  9. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Palmer, Biff F.; Clegg, Deborah J. (25 June 2020). "Salicylate Toxicity". New England Journal of Medicine. 382 (26): 2544–2555. doi:10.1056/NEJMra2010852. PMID   32579814. S2CID   220061471.
  10. 1 2 3 Salicylate Toxicity at eMedicine
  11. "Drugs and Lactation Database (LactMed)". toxnet.nlm.nih.gov. Archived from the original on 2017-09-10.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  12. 1 2 Chyka PA, Erdman AR, Christianson G, Wax PM, Booze LL, Manoguerra AS, Caravati EM, Nelson LS, Olson KR, Cobaugh DJ, Scharman EJ, Woolf AD, Troutman WG (2007). "Salicylate poisoning: an evidence-based consensus guideline for out-of-hospital management". Clinical Toxicology. 45 (2): 95–131. doi: 10.1080/15563650600907140 . PMID   17364628.
  13. 1 2 Temple, AR (February 1981). "Acute and chronic effects of aspirin toxicity and their treatment". Archives of Internal Medicine. 141 (3 Spec No): 364–9. doi:10.1001/archinte.141.3.364. ISSN   0003-9926. PMID   7469627.
  14. R. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 9th edition, Biomedical Publications, Seal Beach, CA, 2011, pp. 20-23.
  15. 1 2 Dargan, PI; Wallace, CI; Jones, AL (May 2002). "An evidenced based flowchart to guide the management of acute salicylate (aspirin) overdose". Emergency Medicine Journal. 19 (3): 206–9. doi:10.1136/emj.19.3.206. ISSN   1472-0205. PMC   1725844 . PMID   11971828.
  16. Meredith TJ, Vale JA (1986). "Non-narcotic analgesics. Problems of overdosage". Drugs. 32 (Suppl 4): 117–205. doi:10.2165/00003495-198600324-00013. ISSN   0012-6667. PMID   3552583. S2CID   40459545.
  17. Vale JA, Kulig K (2004). "Position paper: gastric lavage". Journal of Toxicology: Clinical Toxicology. 42 (7): 933–43. doi:10.1081/CLT-200045006. PMID   15641639. S2CID   29957973.
  18. Hillman, RJ; Prescott, LF (Nov 1985). "Treatment of salicylate poisoning with repeated oral charcoal". British Medical Journal (Clinical Research Ed.). 291 (6507): 1472. doi:10.1136/bmj.291.6507.1472. ISSN   0267-0623. PMC   1418067 . PMID   3933714.
  19. 1 2 Marx, John (2006). Rosen's emergency medicine: concepts and clinical practice. Mosby/Elsevier. p. 2342. ISBN   978-0-323-02845-5.
  20. Gaudreault, P; Temple, AR; Lovejoy, FH (October 1982). "The relative severity of acute versus chronic salicylate poisoning in children: a clinical comparison". Pediatrics. 70 (4): 566–9. doi:10.1542/peds.70.4.566. ISSN   0031-4005. PMID   7122154. S2CID   12738659.
  21. Litovitz, TL; Klein-Schwartz, W; White, S; Cobaugh, DJ; Youniss, J; Omslaer, JC; Drab, A; Benson, BE (Sep 2001). "2000 Annual report of the American Association of Poison Control Centers Toxic Exposure Surveillance System". The American Journal of Emergency Medicine. 19 (5): 337–95. doi:10.1053/ajem.2001.25272. ISSN   0735-6757. PMID   11555795.
  22. Starko, KM (1 November 2009). "Salicylates and pandemic influenza mortality, 1918-1919 pharmacology, pathology, and historic evidence". Clinical Infectious Diseases. 49 (9): 1405–10. doi: 10.1086/606060 . PMID   19788357.