Environmental Emergencies. Objectives. Case Study 1: Snake Bite

Transcription

1 Environmental Emergencies Objectives Identify the early manifestations of a snake bite, appropriate care, and use of antivenin. Recognize serious spider bites and describe management. Distinguish among types of heat illness. Discuss management of hypothermia. Discuss the management of submersion injuries. Case Study 1: Snake Bite 2-year-old boy stepped on a snake and was bitten. He arrives in the emergency department 2 hours later He is alert but tearful, has no increased work of breathing, and his skin is pink. His parents think he stepped on a rattlesnake. 1

2 Initial Assessment (1 of 2) PAT: Normal appearance, normal breathing, normal circulation Vital signs: Heart rate 120/min, respiratory rate 26/min, blood pressure 90/60 mm Hg, temperature 37.2 C, weight 13 kg Initial Assessment (2 of 2) A: Patent, no stridor B: Clear breath sounds C: Pulse is strong and regular. D: Awake, alert; nonfocal motor examination findings E: Right calf has 1 set of fang marks surrounded by 6 in of red induration. Key Questions What is your general impression of this patient? What other information may be helpful? 2

3 General Impression Stable Concern regarding type of snake Cottonmouth Rattlesnake Copperhead Pit Viper Envenomation Assessment: ABCs and resuscitate as indicated Circumstances and number of bites First-aid methods and transport time Stage severity of bite Pit Vipers (Crotalidae) Envenomation severity varies with species. Venoms differ in enzyme components: Myonecrotic, cardiotoxins, nephrotoxins, hemotoxins, neurotoxins Extensive capillary leak and local tissue necrosis may result in circulatory shock. 3

4 Envenomation Staging (1 of 3) No envenomation dry bites In 25% of strikes, no venom is released. Only fang marks present Mild envenomation Fang mark(s) Local edema and tissue necrosis No evidence of systemic effects Envenomation Staging (2 of 3) Moderate envenomation Edema, bullae, ecchymoses beyond local area Tender adenopathy may be present. Evidence of systemic effects Envenomation Staging (3 of 3) Severe envenomation Rapid extension of edema, bullae, ecchymoses involving entire extremity Shock: Tachycardia, hypotension, altered level of consciousness Laboratory: Elevation of prothrombin time/ creatine kinase, depression of platelet count/fibrinogen 4

5 Case Progression Child receives wound care, ibuprofen, and intravenous line access is established. Baseline lab studies obtained After 2 hours, the wound, surrounding erythema, and leg size are unchanged. Vital signs: Heart rate 100/min, respiratory rate 26/min, blood pressure 85/60 mm Hg, temperature 37.2 C, all laboratory study results normal Key Questions Does this patient need antivenin? Does he need hospital admission? Pit Viper Envenomation (1 of 2) Management: Based on bite staging Reassurance: Child and caregivers Keep child quiet and limb at heart level. Serial bite measurements and limb circumference: Every 15 to 20 minutes for 6 hours Every 4 hours for a total of 24 hours 5

6 Pit Viper Envenomation (2 of 2) Establish IV line access Laboratory studies every 2 to 6 hours Local wound care and analgesia Crotalidae Antivenin Crotalidae polyvalent immune Fab antivenin (Crotalidae Fab, Cro Fab) Ovine derived Lower-risk hypersensitivity reactions Antivenin Crotalidae polyvalent Horse serum derived High-risk acute and delayed hypersensitivity reactions Crotalidae Polyvalent Antivenin Indicated in moderate to severe stages Useful in most diamondback rattlesnake bites Mild envenomation: Skin testing followed by 5 vials Moderate envenomation: Skin testing followed by 10 vials Severe envenomation: Skin testing followed by 15 vials 6

7 Case Outcome Because parents are certain rattlesnake bit the boy and diamondback rattlesnakes are known to exist in this geographic area, 5 vials of antivenin were given after skin testing. Patient admitted with serial measurements of lower limb. Discharged home the next day with scheduled follow-up in 5 days. Coral Snakes (Elapidae) 3 varieties found in United States Eastern: Southeast (more toxic) Sonoran/Western: Arizona and New Mexico Texas Account for 1% snakebites Coral Snakes (Elapidae) Bite is 2 puncture wounds less than 1 cm apart. Initially causes mild pain and minimal edema In 4 hours, develop paresthesia, weakness, diplopia, bulbar signs May progress to respiratory failure 7

8 Coral Snake Envenomation Management Supportive care in pediatric intensive care unit No US antivenin (other countries manufacture): useful for Eastern or Texas bites Sonoran: No antivenin needed Follow-up after antivenin Case Study 2: Spider Bite 4-year-old boy bitten by spider at family campsite; tells ED staff spider was dark, no other details Alert and calm, no increased work of breathing, skin pink Initial Assessment (1 of 2) PAT: Normal appearance, normal breathing, normal circulation Vital signs: Heart rate 130/min, respiratory rate 26/min, blood pressure 102/66 mm Hg, temperature 37 C, weight 17 kg 8

9 Initial Assessment (2 of 2) A: Patent, no stridor B: Unlabored, no retractions C: Pulse strong and regular D: Awake but reports experiencing pain at bite E: Right forearm swollen and red with 2 small marks in center of wound. Hand pink, fingers move normally Key Question What is your initial impression of this patient? General impression Patient is stable: Mild pain No muscle rigidity No hypertension No nausea/vomiting Need geographic location Additional observation 9

10 Differential Diagnosis: What Else? Black widow spider Brown recluse spider Nontoxic spider Additional Questions What signs or symptoms would help distinguish the type of spider bite? What studies are needed? What treatment is necessary? Black Widow Spider Genus Latrodectus: Female with red hourglass Venom peptides cause release of: Acetylcholine at myoneural junction Norepinephrine 10

11 Black Widow Spider Bite: Clinical Signs Onset of symptoms 30 to 90 minutes after bite and peak in 3 to 12 hours Hypertension Irritability Muscle rigidity, especially abdominal Respiratory distress, 2 muscle paralysis Periorbital swelling Black Widow Envenomation: Management Supportive care and cardiorespiratory monitoring Benzodiazepines for muscle rigidity Narcotic analgesics for pain Antivenin for hypertension, tachycardia, seizures or symptoms unresponsive to benzodiazepine and narcotic therapy Admit for monitored observation Brown Recluse Spider Loxosceles reclusa: Brown recluse spider Common in Southern and Midwestern states Venom contains calciumdependent enzyme sphingomyelinase D. Has lytic effect on red blood cells 11

12 Brown Recluse Spider Bite Brown Recluse Spider Bite Little pain at time of bite Itching, swelling, erythema, tenderness in a few hours Classically, erythema surrounds dull blue-gray macula. 3-4 days, necrotic base with black eschar Brown Recluse Spider Envenomation Dull blue-gray macule, surrounded by erythema and a ring or halo of pallor Fever Muscle pain Nausea Vomiting Rash Headache Anthalgia Hemolysis Shock 12

13 Brown Recluse Spider Bite: Management Supportive care Local wound care Tetanus prophylaxis Immobilize the affected extremity. Apply ice to reduce pain. Administer antihistamines. Case Discussion/Outcome Child has no signs of severe envenomation a few hours after the bite. Black widow envenomation unlikely with no muscle rigidity, hypertension, or irritability Brown recluse envenomation possible, but no dull blue-gray macule with surrounding pallor, no systemic signs Other nonvenomous spider bite likely Case Study 3: Collapsed, Delirious 13-year-old boy collapses on running track. Coach finds him delirious but breathing. In ED, boy is drowsy and nauseated. He has no increased work of breathing. His skin is hot and sweaty but pink. 13

14 Initial Assessment (1 of 2) PAT: Abnormal appearance, normal breathing, normal circulation Vital signs: Heart rate 80/min, respiratory rate 14/min, blood pressure 100/60 mm Hg, tympanic temperature, 39 C, weight, 40 kg Initial Assessment (2 of 2) A: Patent, no stridor B: Unlabored, no retractions C: Pulse strong and regular D: He knows his name but not the date or how he arrived in the ED. E: No hematoma, bruises Question What is your general impression of this patient? 14

15 General Impression Primary CNS dysfunction Unclear origin Review AEIOU-TIPS. What are your initial management plans? Management Priorities Administer oxygen. Obtain vascular access, give 20-mL/kg fluid bolus (normal saline or lactated Ringer solution) Bedside glucose, baseline laboratory studies ECG Core temperature Cool: Antipyretics, mechanical Differential Diagnosis: What Else? Heat exhaustion Heat stroke Heat syncope Dehydration Cardiac syncope Ingestion 15

16 Heat Exhaustion vs Heat Stroke Temperature <41.1 C Sweating Headache Nausea/vomiting Tachycardia Intact mental status Temperature 41.1 C Dehydration Headache Nausea/vomiting Syncope Change in mental status Seizures Case Discussion Patient had not eaten today and was ill yesterday. Temperature outside 90 F and humid Persistent altered level of consciousness is a concern. Rectal temperature of 39.3 C Sweating should not alter diagnosis. Thermoregulation Normal body temperature 36 C to 37.5 C Anterior hypothalamus preoptic nucleus thermostat regulates body temperature. Heat generation: Basal metabolism, catecholamines and thyroxine, muscle activity, heat-accelerated chemical reactions Heat loss: Radiation, conduction, convection, and evaporation 16

17 Hyperthermia 688 deaths in United States per year 4% in children younger than 14 years Predisposing factors: Age: Infants and elderly Drugs: Malignant hyperthermia Fever and infection Obesity, dehydration, skin abnormalities Lack of acclimatization, fatigue, clothing Previous episode of heat stroke Hyperthermia Pathophysiology At rest, body generates sufficient heat to cause 1 C per hour increase in temperature. Exercise, hard work cause 12-fold increase. Hypothalamus triggers heat-losing mechanism: Increased cardiac output Vasodilation and sweating Acclimatization occurs via activation of reninangiotension-aldosterone system. Minor Heat Illness Heat edema: Cutaneous vasodilatation Heat cramps: Severe cramps of heavily exercised muscles after exertion Heat syncope: Syncopal episode during heat exposure in unacclimatized people 17

18 Major Heat Illness Heat exhaustion Precursor to heat stroke Temperature regulatory mechanisms intact Heat stroke Life-threatening emergency Loss of thermoregulatory mechanism Types of Heat Stroke Exertional heat stroke: Unacclimatized athlete Rapid onset Severe prostration Sweating intact Classic/nonexertional heat stroke: More common in infants and elderly individuals Slower onset Marked dehydration Sweating may be absent Heat Stroke: Signs and Symptoms Temperature >41.1 C Changes in mental status Dehydration Nausea and vomiting Headache Ataxia Syncope Seizures Coma 18

19 Heat Stroke: Management (1 of 2) Give supportive care and cardiorespiratory monitoring. Begin cooling measures: Ice packs to axillae and groin Cool water spray and fan Begin fluid resuscitation with 20 ml/kg of normal saline Heat Stroke: Management (2 of 2) Do laboratory studies: CBC, renal and liver function, glucose, coagulation, creatine kinase MB, arterial blood gas, urinalysis Admit to monitored setting. Stop cooling when core temperature is below 39 C. Case Outcome After fluids and cooling, patient is more alert and responsive. Baseline laboratory study and ECG results normal Patient hospitalized, no complications Coach stressed oral rehydration and had mandatory breaks when temperature >80 F. 19

20 Heat Stroke: Prevention Avoid exertion during warmest daytime hours (10 AM to 4 PM). Light clothing and frequent breaks Adequate intake of electrolyte solutions Avoid salt supplements. Case Study 4: Submersion 7-year-old girl falls out of boat in shallow lake, struggles at surface then goes underwater Another boat occupant dives in and rescues her within 10 minutes. At shoreline, emergency medical services reports that she is breathing fast but on her own. She is very sleepy. They immobilize her and transport her with 100% oxygen. Initial Assessment (1 of 2) PAT: Abnormal appearance, abnormal breathing, normal circulation Vital signs: Heart rate 124/min, respiratory rate 30/min, blood pressure 100/70 mm Hg, temperature 35 C 20

21 Initial Assessment (2 of 2) A: Patent, no stridor B: Tachypneic with retractions C: Pulse strong and regular D: She slowly responds to questions. E: No obvious injuries Detailed Physical Examination Head: No bruises, no hematoma Neck: In collar, denies pain Lungs: Wheezes and rhonchi bilaterally Abdomen: Soft Extremities: Able to wiggle fingers, toes Neurologic: Sleepy but good sensation and strength Key Question What is your general impression of this patient? 21

22 General Impression Respiratory distress Submersion injury Hypothermic (mild): Temperature of 35 C What are your management priorities? Case Management Provide warm, humidified oxygen. Provide warm intravenous fluids. Obtain chest radiograph. Remove cold, wet clothing and provide warm blankets. Reassess. Submersion Injury Second leading cause of unintentional injury in children aged 1 to 14 years Peak incidence in boys: Younger than 4 years 15 to 19 years Definition of drowning: Respiratory impairment from submersion (totally covered) or immersion (partially covered) in a liquid 22

23 Submersion Injury: Pathophysiology Global hypoxia: Acidosis 90% of patients aspirate: Surfactant wash out 10% of cases have laryngospasm: Dry drowning Central nervous system hypoxia: Most common cause of death Coagulopathy and renal failure can develop after hypoxia. Cardiac arrest Managing the Responsive Patient Assess ABCs and apply cardiac monitor/pulse oximeter. Assess rectal temperature and remove wet clothing. Rule out underlying comorbidity, especially drugs, alcohol, and possible child abuse. Monitor glucose level. Image chest and cervical spine if diving/fall. Admit for any oxygen requirement: Observe for delayed oxygen requirement. Submersion Injury: Predictors for Death or Severe Neurologic Sequelae After 25 minutes of resuscitation with no return of spontaneous circulation in non-icy waters >5 C (>41.1 F), survival is unlikely If icy water submersion, attempt rewarming. 23

24 Managing the Unresponsive Patient (1 of 2) ABCs and cervical spine stabilization Bag-mask ventilation with 100% oxygen, intubate, insert nasogastric/orogastric tube CPR and ECG: Initiate medications and electrical interventions as indicated. Intravenous access: Normal saline, check glucose Assess rectal temperature and remove wet clothing. Managing the Unresponsive Patient (2 of 2) Perform baseline laboratory tests, blood gas analysis, and chest radiography and consider performing a toxicology screen. Ventilate with positive end-expiratory pressure (5-10 cm H 2 O). Begin rewarming if hypothermic. Neurologic status: Rule out underlying condition. Admit to PICU. Hypothermia Pathophysiology Core temperature below 35 C (95 F) Classification: Mild, moderate, or severe Preoptic anterior hypothalamus initiates sympathetic neurogenic signals: Increased muscle tone Increased metabolic rate Shivering Cutaneous vasoconstriction Bradycardia Apnea and asystole 24

25 Hypothermia: Predisposing Factors Endocrine or metabolic derangements, hypoglycemia, hypothyroidism Infection: Meningitis, sepsis Intoxication: Alcohol, opiates Intracranial disease Environmental exposure/submersion injury Dermatologic: Burns Iatrogenic Mild Hypothermia 32 C to 35 C (89.6 F-95 F) Shivering preserved Inappropriate judgment or mental slowing Treat with passive rewarming (warm blankets). Moderate Hypothermia (1 of 2) 28 C to 32 C (82.4 F-89.6 F) Muscle rigidity Progressive loss of consciousness/coma Difficult to detect vital signs ECG change of an Osborn (J) wave 25

26 Moderate Hypothermia (2 of 2) Treatment: ABCs: Control airway CPR Intravenous access and laboratory studies Active rewarming Myocardium is resistant to defibrillation and medications below 30 C. Active Rewarming Method Warm humidified oxygen Warm intravenous fluids Gastric or rectal lavage Open thoracotomy with mediastinal irrigation Extracorporeal blood rewarming (bypass) Severe Hypothermia <28 C (82.4 F) Appear dead Coma Dilated unresponsive pupils Respiratory arrest and ventricular fibrillation Treatment: ABCs: Control airway CPR, laboratory studies Active rewarming to 30 C 26

27 Case Outcome Repeat temperature of 37.1 C Initial radiographs negative Patient requires 2 L of oxygen to keep SaO 2 arterial oxygen saturation >92% Patient is admitted to the hospital. Promises to wear personal floatation device next time Key Points: Submersion Injury Prompt, effective CPR improves prognosis and outcome. Aggressive out-of-hospital resuscitation if patient arrested Prolonged in-hospital resuscitation of nonhypothermia patients is not indicated. Patients with altered level of consciousness should be intubated, provided with mechanical ventilation, and transported to the PICU. The Bottom Line Environmental emergencies are a diverse group of conditions that result from environmental insults, each with unique signs, symptoms, and management. Recognition of symptoms and consideration of an environmental cause of the clinical features will result in early diagnosis and appropriate management. Prevention is key in reducing injuries. 27

28 Credits Unless otherwise indicated, all photographs and illustrations are under copyright of Jones & Bartlett Learning, courtesy of Maryland Institute for Emergency Medical Services Systems, or the American Academy of Pediatrics. Slide 1: David R. Frazier/Photo Researchers, Inc. Slide 7A-C: SuperStock/Alamy Images, Photos.com, Courtesy of Ray Rauch/U.S. Fish & Wildlife Service Slide 20: Courtesy of Luther C. Goldman/U.S. Fish & Wildlife Service Slide 30: Crystal Kirk/ShutterStock, Inc. Slide 33: Courtesy of Kenneth Cramer, Monmouth College Slide 34: Courtesy of Department of Entomology, University of Nebraska Slide 83: Photos.com 28