Case Presentation #4: A Pretty Worm

Transcription

1 Case Presentation #4: Presented by Brent R. King, MD, FAAP, FACEP A three year-old child arrives via EMS with ptosis, stridor, hypersalivation, hypotonia, and poor respiratory effort. The symptoms began 30 minutes prior to arrival. His mother reported that he was playing in the back yard earlier in the day and reported being pinched by a pretty worm. The PAT is as follows Appearance: Abnormal. The child appears drowsy and limp. Work of Breathing: Abnormal. The child has obvious stridor and poor respiratory effort. He has copious oral secretions. Circulation to the Skin: Normal. Capillary refill time is less than two seconds. Vital Signs Include Heart rate: 130 bpm Respiratory rate: 8 breaths/min Blood pressure: 78/40 mmhg Temperature: 37.5 C Weight: 16 kg Initial Assessment A: Obvious stridor B: Poor respiratory effort with clear breath sounds C: Normal color and tachycardia D: Hypotonic E: Two small crusted marks in the web space of his right hand Focused History S: The child was completely well and behaving normally prior to the day of arrival. His mother reports that he was digging in the garden with a toy shovel. She was called back into the house to answer the phone. A few minutes later she found him at the back door crying, saying that a pretty worm had pinched him. She saw two small marks on his hand, one of which was actively bleeding. The wounds were not inflamed or edematous. She took him to his family physician, who noted that there was no evidence of inflammation two hours after the event. He told the mother that the wound might represent a dry bite from a small venomous snake, a bite from a non-venomous snake, or contact with an insect. He instructed her to watch for signs of inflammation and gave instructions for local wound care. Thirty minutes before Case Presentation #4: 1

2 calling EMS, the patient began to exhibit stridor and drooling. He then became weak and listless, and his mother called A: No allergies. M: None. P: Born at term. No significant past medical history. Fully immunized. L: He ate part of a sandwich 4 hours prior to ED arrival. E: Child was well prior to being pinched by the pretty worm. Detailed Physical Exam Skin: No rashes. Two marks with what appears to be crusted blood in the web space of the right hand. No edema, redness, or warmth is present at the site. Head: Ptosis, disconjugate gaze, copious oral secretions, and stridor. Chest: Poor respiratory effort and clear breath sounds. Heart: Tachycardia, no murmurs, and regular rhythm. Abdomen: Soft, non-tender, and without hepatosplenomegaly. Neurologic examination: Poor tone and diminished deep tendon reflexes. Appears to be drowsy. Key Questions What is your general impression of this patient? Characterize the patient s condition as one of the following: Stable Respiratory Distress Respiratory Failure Shock Primary CNS/Metabolic Dysfunction Cardiopulmonary Failure/Arrest Core Knowledge Points General Impression This child is in respiratory failure. Abnormal appearance and work of breathing suggest respiratory compromise. Interventions should include placement on a monitor and pulse oximeter. Supply supplemental oxygen and support ventilation with bag-mask ventilation. Continue your assessment. Patient has abnormal appearance and work of breathing with evidence of neurologic dysfunction. He is tachycardic as well. Case Presentation #4: 2

3 Key Questions What are your initial management priorities? Airway management and continued support of ventilation. Critical Actions This patient shows evidence of respiratory failure, airway obstruction, early circulatory compromise (tachycardia), and evidence of neurologic dysfunction. While the reasons for this are unknown, initial management should focus on airway management and restoration of circulatory status. The initial history is consistent with a snakebite and consultation with a regional poison center or snakebite specialist is warranted once the patient is stable. o Continue bag-mask ventilation and prepare for rapid sequence intubation. o Obtain IV access. o Begin RSI: Administer etomidate and rocuronium followed by endotracheal intubation. o Administer 20 ml/kg of NS. o Obtain samples for laboratory evaluation including: a complete blood count, electrolyte panel, toxicology screen, and urinalysis. o Consultation with a poison center or a snakebite expert. o Once the patient is stable, a CT scan and lumbar puncture might be considered. Case Development The child is successfully intubated and fluids are infused The acute nature of the symptoms along with the wounds on the child s hand and the history of a pretty worm strongly suggest coral snake envenomation. The toxicologist at the poison center suggests that the symptoms are consistent with envenomation by an eastern coral snake or Texas coral snake. Other possibilities include: o Ingestion o Acute encephalitis o Contact with nerve agent or insecticide o Envenomation by a non-native elapid snake Key Question What management strategies should be considered? The possibility of envenomation by a coral snake and presence of severe symptoms indicate the need for administration of antivenin. Case Presentation #4: 3

4 Figure 4-1 Coral snake. Core Knowledge Points Coral Snake Envenomation Coral snakes are the only elapid snakes native to North America. There are two genera of coral snake in the United States. Genus Micrurus includes the eastern coral snake (Micrurus fulvius), which is found in the Southeastern United States from North Carolina, throughout Florida, and as far as the Mississippi River. The Texas coral snake (Micrurus fulvius tenere) is found in Texas, Louisiana, and Arkansas. Genus Micruroides includes the Arizona coral snake and the sonoran coral snake. Micruroides venom is far less toxic than Micrurus venom and antivenin is rarely required for envenomations by snakes in this genus. The venom of elapid snakes is primarily neurotoxic and may cause little or no local tissue reaction. The venom of coral snakes is neurotoxic and results in parathesias and muscle fasiculations at the site of the bite which may progress over hours to weakness, dizziness, nausea, vomiting, paresthesias, hypersalivation, and respiratory paralysis. Bulbar symptoms such as diplopia, dysphagia and slurred speech may precede respiratory failure and may be delayed for greater than 10 hours from the time of Case Presentation #4: 4

5 the initial bite. Death is due to respiratory failure but cardiac failure has also been reported. Coral snakes are small and shy and bites are unusual; however, a large coral snake can administer up to 20 mg of venom in a single bite. This is four to five times the lethal dose for a human adult. Fortunately, up to 50% of bites do not result in envenomation. Elapid snakes deliver venom by latching tightly onto their prey and then making chewing motions with their jaws. If the snake is attached for as little as 10 to 30 seconds significant envenomation can occur. Victims often report that the snake is difficult to remove and describe removal to be like peeling layers of Velcro apart. The onset of neurologic symptoms may be delayed for several hours after the bite. Because the onset of symptoms can be delayed and there is little or no local reaction, it is easy to mistake true envenomation for a dry bite. Neurologic symptoms can be local (e.g. numbness and tingling of the affected extremity) or systemic. Once systemic symptoms are present, they may be very difficult to reverse even with administration of antivenin. Many patients have residual neurologic symptoms for months or permanently. There is currently no FAB fragment antivenin for coral snake venom. The available antivenins are manufactured with horse serum. Furthermore, antivenin may be difficult to find. There is only one manufacturer in the United States (Wyeth) and supplies are limited. In addition to hospital pharmacies, local zoos may keep coral snake antivenin. An additional source is the national antivenin bank, which is a joint project of the American Zoo and Aquarium Association and the American Association of Poison Control Centers. When antivenin is unavailable locally, the local poison control center (800/ ) can, given time, find a source through the antivenin bank. Critical Actions Possible Diagnosis (1) The coral snake s neurotoxic venom can affect airway protective reflexes and respiratory drive. The presence of these symptoms is an indication for management of the airway. Any neurologic symptoms, even local symptoms, are an indication for antivenin administration. Additionally, because the onset of serious symptoms can be delayed for many hours and because it can be very difficult to determine which victims were envenomated, some authorities recommend administration of antivenin to anyone with a reliable history of a coral snake bite. One vial of antivenin is sufficient to neutralize 2 mg of venom. The authors of the largest case series of coral snake bites to date recommend that a minimum of 4 6 vials of antivenin be given. Ten 15 vials may be required in cases of severe envenomation. Case Presentation #4: 5

6 Antivenin is administered as follows: o A test dose of horse serum should be given prior to the administration of the full dose. Prior to the administration of the test dose, emergency airway equipment and medications should be brought to the bedside and an attending physician should be present. The patient should receive cc of 1:00 horse serum intradermally. Some practitioners prefer to pretreat the patient with antihistamines. A skin wheal (usually present within 5 to 30 minutes in sensitive patients) indicates sensitivity to horse serum. o Provided that the skin test does not indicate sensitivity to horse serum, antivenin treatment should begin with a minimum of 4 6 vials. Each vial of antivenin should be reconstituted with 10mL of sterile water or normal saline and gently agitated. The total dose of antivenin should then be diluted in an age appropriate volume of normal saline (ideally mL) and administered over 1 2 hours. Some authorities prefer to administer a portion of the total dose over 30 minutes and then to decrease the rate of administration to the maximum safe rate for age and clinical condition. Because a serious reaction to horse serum can occur at any time, emergency medications for allergic reactions to the antivenom include epinephrine and vasopressor agents. Up to one-fourth of patients can be expected to exhibit signs of hypersensitivity to horse serum during treatment and about one-half will develop serum sickness during the treatment or soon afterward. o If a reaction occurs during treatment, the infusion should be stopped and the patient treated with antihistamines, steroids, and, if necessary epinephrine. The infusion can then be restarted at a slower rate of administration or the antivenin can be further diluted. The decision to administer antivenin to a person who has demonstrated sensitivity to horse serum is a difficult one. In cases of severe envenomation, antivenin may be life-saving but the practitioner must be prepared to treat anaphylaxis should it occur. Such individuals are best stabilized and rapidly transported to a facility capable of treating such severe complications. Core Knowledge Points Possible Diagnosis (2) Non-native elapid snakes are kept as pets by some individuals. Many of these snakes are highly venomous and aggressive. While they can occasionally escape or be released into the wild, the vast majority of bites from these snakes occur while they are being handled by their keepers or other individuals. In such cases, it is critical that the snake be correctly identified so that a source of antivenin can be located. If possible, the snake should be examined by a professional herpetologist. If this is not possible, high-quality digital photos of the snake may be sent to a herpetologist via the internet. Alternatively, the keeper may be able to correctly identify the snake and may even have a supply of appropriate antivenin. Treatment Case Presentation #4: 6

7 for these types of bites should be conducted in concert with a poison center or a knowledgeable expert. In this case, the description of the snake and the bite pattern does not suggest a large, non-native elapid bite. Case Development The patient is admitted to the intensive care unit and treated with a total of 8 vials of antivenin. Over the next few days his neurological symptoms improve, but he develops erythema multiforme and a low-grade fever. The team caring for him appropriately determines that this is serum sickness related to receipt of a horse-serum-based antivenin and administers steroids. He is extubated on the third day after the bite and discharged from the hospital two days later. He has some residual weakness for three weeks but suffers no permanent sequelae. References Kitchens CS, Van Mierop LHS. Envenomation by the Eastern Coral Snake (Micrurus fulvis fulvis): A study of 39 victims. JAMA 1987;258: Dart RC, McNally J. Efficacy, safety, and use of snake antivenoms in the United States. Ann Emerg Med 2001:37: Additional Reading APLS: The Pediatric Emergency medicine Resource pages Pittman J. Once Bitten: The keys to coral snakebite management. AJN April 2002 pages 24DD-24GG. The University of California at San Diego Snakebite Management Protocols ( {These are suggested treatment protocols for a variety of non-native venomous snakebites.} Norris R. Snake Envenomation, Coral.eMedicine: Emergency Medicine 2006 [serial online] available at: Case Presentation #4: 7