Case Report
Severe Iron Poisoning Treated with High Dose Deferoxamine: A Case Report
Suzan S Mazor1,2,3*, Shelton W Wright1,2, Matthew Valento2,3 and Betty C Chen2,3
1Seattle Children’s Hospital, USA
2University of Washington, USA
3Washington Poison Center, USA
*Corresponding author: Suzan S Mazor, Associate Professor, Pediatric Emergency Medicine, Toxicology Director, Continuing Medical Education, Seattle Children’s Hospital, University of Washington, USA
Published: 14 Jan, 2017
Cite this article as: Mazor SS, Wright SW, Valento M, Chen
BC. Severe Iron Poisoning Treated
with High Dose Deferoxamine: A Case
Report. Ann Clin Case Rep. 2017; 2:
1238.
Abstract
The incidence of iron poisoning, once the most common cause of fatal pediatric unintentional ingestions, and the use of its antidote deferoxamine (DFO) has declined. This decrease has resulted in provider inexperience in recognizing clinical aspects and in managing iron poisoning. We present the case of a 17-year-old girl who presented to a hospital following an intentional polysubstance ingestion, which included ferrous sulfate. She developed severe gastrointestinal symptoms including hematemesis, as well as anion gap metabolic acidosis, coagulopathy, and liver toxicity. She was treated with DFO at doses higher than recommended by the pharmaceutical company due to an extremely elevated serum iron concentration of 2565 g/dL and worsening clinical status. Clinical features and management of complex iron poisoning are discussed. The early consultation of a poison control center and the expertise of medical toxicologists can help providers manage complex poisoning cases and weigh the risks and benefits of off-label use of DFO for severe iron poisoning.
Abbreviations
DFO: Deferoxamine; PICU: Pediatric Intensive Care Unit
Introduction
The incidence of serious iron poisoning has drastically decreased over the last 30 years. Iron poisoning was once the most frequent cause of fatal pediatric unintentional ingestions [1]. However, public health measures mandated by the U.S. Food and Drug Administration following urging from the American Association of Poison Control Centers (AAPCC) have resulted in less ingestion and fewer fatalities. The AAPCC reported 5,455 iron exposures in 2014. Of those, 2,095 occurred in children under 6 years of age, and 547 were intentional ingestions. Only one fatality from iron toxicity was reported to the AAPCC in 2014 [2]. Due to the decreased incidence of severe iron poisoning, the use of deferoxamine (DFO) has also declined. This fall in DFO use has resulted in provider inexperience with prescribing this chelator. We report a case of serious iron poisoning resulting from an intentional polysubstance ingestion that included ferrous sulfate. The patient’s treatment required a complex regimen of DFO due to extremely elevated serum iron concentrations.
Case Presentation
A 17-year-old girl presented to a local emergency department (ED) following intentional
polysubstance ingestion. In the ED, she was lethargic but able to state that she ingested an unknown
number of ferrous sulfate tablets. In addition, she also swallowed an unknown number of two
over-the-counter products: Tylenol PM® (each containing 500 mg of acetaminophen and 25 mg
of diphenhydramine) and Excedrin Extra Strength® (each containing 250 mg of acetaminophen,
250 mg aspirin, and 65 mg of caffeine). Her initial vital signs were: temperature: 35.4O C; heart
rate: 153 beats per minute; respiratory rate: 20 breaths per minute; blood pressure: 154/103 mmHg;
and oxygen saturation: 100% on 1 L/min of oxygen by nasal cannula. On exam, she was alert and
oriented without focal neurologic deficits. She obeyed commands and was conversant though
she was noted to have a flat affect. Her cardiovascular exam was notable for a peripheral capillary
refill of greater than three seconds, and her abdominal exam was unremarkable. During her initial
evaluation, she had an episode of red-colored emesis. An abdominal x-ray did not demonstrate
tablets in her gastrointestinal system. Laboratory values revealed a metabolic acidosis on venous
blood gas with pH, 7.16; pCO2, 43 mmHg; lactate, 10.4 mmol/L; and bicarbonate, 15 mmol/L. Other
notable laboratory studies included the following: white blood cell count, 19.6 k/cmm; hemoglobin, 19 g/dL; platelets, 393 k/cmm; acetaminophen concentration,74.6 μg/
ml (2 hours after reported ingestion); salicylateconcentration,7.3 mg/
dL; and iron concentration, 2565 μg/dL. Urine drug screen performed
by immunoassay was positive for cocaine. An electrocardiogram was
significant for sinus tachycardia at a rate of 151 beats per minute and
QTc of 535 ms. The patient was given 50 mEq of intravenous sodium
bicarbonate and then transferred to a pediatric Intensive Care Unit
(PICU) of a tertiary referral children’s hospital.
On arrival to the PICU, the patient’s repeat laboratory values
were significant the following: iron concentration, 2793 μg/dL;
acetaminophen concentration, 48 μg/ml (4 hours post-ingestion)
(Table 1); creatinine, 0.9 mg/dL; International Normalized Ratio
(INR), 2.5 (Table 2). The patient was treated with a DFO infusion
starting at 3.79 mg/kg/hour for 10 hours. This rate was initially
chosen because the pharmacist did not feel comfortable exceeding
the package insert’s recommended maximum daily dose of 6 grams.
After consultation with the local poison control center, the rate was
increased to 10 mg/kg/hour. She received the DFO infusion at this
rate for another 10 hours. During this time, she continued to have
episodes of frank hematemesis. She received 2 units of Fresh Frozen
Plasma (FFP) which resulted in an INR of 1.8 and decreased episodes
of hematemesis. After 20.5 hours of DFO therapy, her infusion was
held for 18 hours, and then resumed at 10 mg/kg/hour for another 7
hours. During this time, she did not develop any respiratory distress
or hemodynamic instability (Table 3).
One day after the ingestion, the patient’s iron concentration was
329μg/dL. Approximately 36 hours after the ingestion, the patient
developed evidence of hepatotoxicity with Aspartate Aminotransferase
(AST) rising from 199 to 1607 IU/L and Alanine Aminotransferase
(ALT) rising from 96 to 2072 IU/L. Her conjugated bilirubin peaked
at 1.9 mg/dL and unconjugated bilirubin peaked at 2.3 mg/dL. Given
the patient’s co-ingestion of acetaminophen, the providers initiated
intravenous n-acetylcysteine therapy in case her reported time of
ingestion was incorrect. She received a 21-hour course for presumed acetaminophen toxicity. During this time, she received an additional
2 units of FFP for persistently abnormal INR measurements. 72-hours
post-ingestion, she began to show improvement in her alanine
aminotransferase level, hyperbilirubinemia, and coagulopathy.
She was transferred out of the PICU five days after admission and
subsequently discharged from the hospital nine days after admission.
Four weeks after the ingestion, the patient was evaluated in an
outpatient gastroenterology clinic for emesis, poor oral intake and
weight loss. A barium upper gastrointestinal fluoroscopy with small
bowel follow-through showed no evidence of gastric outlet obstruction
or stricture. However, due to continued feeding intolerance, six weeks
after her ingestion, she underwent a esophagogastroduodenoscopy
which showed evidence of gastric outlet obstruction. She subsequently
underwent two gastric dilations with the placement of a nasojejunal
feeding tube. Six months after her ingestion, she has had appropriate
weight gain despite intermittent symptoms of nausea.
Table 1
Table 1
Serologic levels of ingested substances by time after ingestion.
First level after deferoxamine started
Table 2
Table 3
Discussion
Once a leading cause of pediatric poisoning, the incidence of
iron overdose has markedly diminished, largely due to a series of
preventative measures, including warning labels and unit dose
packaging, instituted by the US Food and Drug Administration
(FDA) in the late 1990s [3]. Only one death from iron overdose was
reported in the most recent National Poison Data System (NPDS)
Annual Report [2]. Despite the rarity of severe overdose, clinicians
should remain aware of the indications for treatment of iron toxicity
with deferoxamine and its associated risks.
Deferoxamine, an iron-specific chelator, can be used for acute
or chronic iron overload. Following acute overdose, it is usually
recommended for patients exhibiting evidence of serious poisoning
(e.g. metabolic acidosis, shock) or with serum iron concentrations
greater than 500 ug/dl [4]. The standard recommended infusion rate
is 15 mg/kg/h, though some authors advise starting at lower doses
and titrating up to avoid hypotension, which has been described
following rapid infusion [5,6]. In this case, the patient received an
initial rate of infusion at 3.79 mg/kg/hr, which calculated by the
hospital pharmacist based on the package insert that reported the
maximum dose over a 24-hour period is 6 grams. Current practice
accepts that DFO often exceeds this 6 gram limit. Deferoxamine is
ideally administered early, while the majority of iron is accessible
for chelation in the serum compartment, and for a short duration,
to avoid side effects associated with prolonged infusion. Because of
the extremely elevated serum iron concentration, the poison control
center recommended increasing the rate of DFO infusion to at least
15 mg/kg/hr with options to increase it up to 40 mg/kg/hr if the
patient could tolerate the infusion. Perhaps the most concerning
of deferoxamine potential side effects is development of Acute
Respiratory Distress Syndrome (ARDS). Significant pulmonary
toxicity has been reported following intravenous infusions for greater
than 24 hours [7,8]. Proposed mechanisms for pulmonary injury
include free radical formation and intracellular catalase depletion
[9]. We were concerned about the possibility of a lengthy treatment
course upon learning of the patient’s markedly elevated serum iron
concentration. In an attempt to avoid pulmonary complications, we
recommended a 12-hour deferoxamine “holiday” once the patient’s
initial treatment approached 24 hours. We found only one prior
report of an intermittent dosing approach following acute iron
overdose [10]. The patient in that case developed ARDS on the second hospital day, but was treated with a higher infusion rate (25 mg/kg/h)
due to his poor presenting condition and exceedingly high serum
iron concentration (16,706 ug/dL). Fortunately, our patient’s clinical
status markedly improved following approximately 27.5 hours of
therapy, and she showed no evidence of pulmonary toxicity during
her hospitalization.
The clinical presentation of this patient was confounded by her
co-ingestions of acetaminophen-containing products. She developed
signs of hepatotoxicity between 24 and 48 hours post ingestion with
rising liver function tests and development of coagulopathy. Liver
toxicity is a relatively late clinical feature of severe iron poisoning,
typically occurring between 2 and 3 days following ingestion. Iron
causes local oxidative damage upon entering the liver [4,5]. So while
it is possible that the patient developed acetaminophen-induced liver
injury, perhaps due toan inaccurate history of time of ingestion, it
is more likely that the patient’s hepatotoxicity was a result of iron
toxicity.
Conclusion
Clinically significant iron poisoning occurs less frequently following preventative measures instituted by the FDA in prior decades. This decrease has resulted in provider inexperience with evaluation and management of cases, particularly in the prescribing of DFO. This case was particularly complicated due to the extremely elevated serum iron concentration, which suggested that the patient required prolonged DFO infusion past the recommended usual 24 hour limit. The consultation of poison control centers and the expertise of medical toxicologists can help providers weigh the risks and benefits of off-label use of DFO for severe iron poisoning.
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