Epidemiology of Jellyfish Stings Presented to an American Urban Emergency Department

Abstract

Introduction

Cnidarian, or jellyfifish, stings are a common malady in tropical Emergency Departments. There are limited studies examining cnidarian stings in the United States. The team investigated the epidemiology and treatments for jellyfish stings presenting to an urban emergency department (ED) in Honolulu, Hawai‘i.

Methods

The team performed a retrospective chart analysis of stings presented between 2000 and 2008. A total of 116 patients were identified. Charts were reviewed for patient demographics, incident characteristics, patient arrival condition, and treatments given in the emergency department.

Results

The median age was 24 years (range 9–85). Of patients 58% were men, 64% were Hawai‘i non-residents, and 23 % arrived between the hours of 10pm and 2 am. Emergency Medical System transported 64%, and 65% arrived with normal vital signs. Twenty-four different types of IV/PO medications were administered and patients received up to 5 different medications per visit. Intravenous medications were given to 64%. All patients were eventually discharged home from the ED.

Discussion

Risk factors for cnidarian stings include being men, being a Hawai‘i non-resident, and nighttime ocean activities. Stings were treated with various medications and routes suggesting that there is no current standard of care for stings. This study suggests that there is a need for public health interventions tailored to tourists. Prevention and education of home treatment could decrease the cost of health care by decreasing ambulance transports and total number of ED visits for a non-urgent disease.

Introduction

Cnidarians, more commonly known as “jellyfish,” are responsible for a number of cases annually presented to emergency departments in tropical settings. In Hawai‘i, the most common cnidarian stings arise from two particular species: the box jellyfish (Carybdea alata) and Portuguese man-of-war (Physalia physalis). These species have a considerable impact on Hawai‘i's beach-going culture. During influxes, as many as 1000 jellyfish may appear per day with reported stings reaching over 800 at a single beach.^1,2

Cnidarians have tentacles containing billions of nematocytes — stinging cells that fire toxins upon physical or chemical stimulation. Local effects of stings include intense pain, blistering and skin necrosis. Less common symptoms such as malaise, weakness, fever, chills, muscle spasms, nausea, and vomiting may also occur.^3–5 On rare occasions, unique to Australia, death has also been reported.

Despite the multiplicity and adverse effects of cnidarian stings, literature on treatment and epidemiology are limited. Moreover, sting treatment information published in available journals can be conflicting. The use of hot water immersions or hot compress was supported by several studies as a useful practice in relieving pain.^6–8 However, contrary studies report cold packs and ice to be effective in relieving pain while heat was ineffective.² A current guideline from the Australian Resuscitation Council (ARC) also recommends cold wrap applications following cnidarian stings.⁷

Popular home remedies such as alcohol, urine, or sand can actually worsen symptoms for the victim. Physical rubbing or pressure of the affected area and certain topical chemicals may cause both “fired” and “unfired” nematocytes on the skin to release toxins.^3,9–11 It is therefore important for sting victims to have accurate wound care instruction to prevent further exacerbation.

The lack of available knowledge about cnidarian stings and a published consensus on its treatment may be sources of confusion in the emergency department. In this study, the team investigated the epidemiology, severity, and treatments of cnidarian stings presenting to an urban community emergency department (ED) in Honolulu, Hawai‘i.

Methods

The team conducted a retrospective chart review of all patients presenting to the ED with jellyfish stings between January 2000 and June 2008. The team compiled a database using the International Classification of Disease, Ninth Revision, (ICD-9) and search of the hospital electronic medical records for charts coded for “marine envenomtion.” This yielded 133 cases. The query was further narrowed to charts listing causes as “jellyfish” or “man-of-war sting.” Seventeen patients were excluded because of non-jellyfish envenomations such as sea urchin stings.

The final 116 charts were reviewed for patient demographics and incident characteristics. Times of envenomation were categorized into six periods: 10pm–2am, 2am–6am, 6pm–10am, 10am–2pm, 2pm–6pm, and 6pm–10pm. Two cases did not have a listed time of occurrence. Additionally, the team evaluated patient arrival conditions, vital signs, treatments given prior to arrival and in the ED. The different topical, intravenous and oral medications were recorded and categorized.

Results

The hospital treated 116 patients with jellyfish envenomations in an eight year period. The patients' age ranged from 9–85 years with the median age being 24. Sixty-seven of 116 were men (58%) and 76 were Hawai‘i non-residents (64% ). There were 70 patients (61%) presenting to the ED between 6am to 2pm and 26 (23%) presented between the hours of 10pm and 2am.

Of the total, 74 (64%) patients arrived at the emergency room by Emergency Medical System (EMS). Of these patients 24 (21%) received care prior to arrival. On arrival in the ED 75 (65%) had normal vital signs and no patients were admitted to the hospital after treatment in the emergency department. In the ED, 74 (64%) patients received IV treatment. Over the course of this study, 24 different types of intravenous therapy (IV) or oral medications were used. In a single visit, a patient received up to five medications which included anti-histamines, anti-inflammatories, steroids, narcotics, and muscle relaxants. Twenty-five (22%) patients received some form of topical treatment in the ED.

Discussion

Each year, cnidarian sting cases are presented to the ED in tropical settings. Published literature on stings has been both limited and conflicting. The results of this study may aid in prevention efforts as well as more efficient ways of treating future cnidarian stings in emergency departments.

Patient Demographics

Of the cases presented to the ED, a slight majority were men at 58% versus 42% for women. Forrester published a comparable survey performed in Texas and reported similar results with men accounting for 52% of the stings and women accounting for 47%.⁵ This would suggest men are at higher risk of contracting a cnidarian sting.

Many evenomations occurred in patients who were Hawai‘i nonresidents. Newcomers unfamiliar with Hawai‘i's marine life may run a higher risk of being stung due to a lack of knowledge on sting prevention measures that include predictable box jellyfish influxes such as the cyclic occurrence of box jellyfish on Hawai‘i's beaches 9–10 days after a full moon.² Currently, beaches in Waikiki post warning signs during jellyfish influxes, but stings may still proliferate as swimmers often ignore the posted warnings. One reason may be that jellyfish are often difficult to see even during the day and cause no perceived threat.¹ Tourists might benefit from a more proactive form of caution such as sting education provided by lifeguards and hotel staff.

While it is assumed that the majority of people would go to the beach during the day, there were a relatively large number of envenomations presenting during the nighttime hours from 10pm to 2am. Increased beach patrols during the night time hours and warning signs, might decrease the number of night time swimmers and subsequent marine envenomations.

Treatment Standards

There is a lack of consensus on an acceptable treatment regimen among ED physicians. In the ED, cnidarian stings were treated with topical, intravenous, and oral medications. The study found significant variation of treatment with 24 different intravenous medications used over the course of the study. These included narcotic pain medications, antihistamines, anti-inflammatories, steroids, and muscle relaxant drugs among many others. A study of 107 patients conducted by the Western Australian Poison Centre produced similar results, citing the use of 12 different first aid treatments.^7,11

Current information on cnidarian sting care only provides recommendations, albeit inconsistent, for over-the-counter drugs and topical remedies. Few, if any, describe the intravenous drugs for more severe cases presented to emergency departments. With no established medications, emergency physicians appear to be resorting to treatment unspecific to cnidarian stings or administering drugs based on personal preference. Future consolidation of medications and a protocol for jellyfish stings used to treat stings will help to decrease cost for patients and streamline treatment in the ED.

Injury Severity and Associated Cost

A report by Currie et al. mentions a vast majority of patients presented to the ED with cnidarian stings suffer from local injury, but are not systemically poisoned.¹² The Straub study confirmed that most of the patients have normal vital signs and non-systemic injuries. More importantly, none were admitted to hospital after treatment in the emergency department. These statistics suggest cnidarian stings are a non-severe injury and may not warrant emergency services. But despite the apparent low severity, several expensive emergency services were administered in the Straub study, such as arrival by EMS and IV medications. In addition to the cost of physician examination, a single cnidarian sting treatment can become very costly for the patient.

To avert these expensive services, patients can be treated beachside with lower-cost, over-the-counter remedies that include oral medications or topical therapies. While a few available studies may disagree, there seems to be a general agreement on oral analgesics, topical acetic acid (vinegar), and hot compress in relieving pain. Although acetic acid will not neutralize the toxins that have already been fired, acetic acid will deactivate unfired nematocytes left behind by both box jellyfish and man-of-war tentacles.^3,7,13

While there is some argument over the efficacy of heat, hot water immersions were shown to considerably reduce pain in clinical trials conducted with both box jellyfish and Portuguese man-of-war stings.^6–8 Heat is often prescribed in literature, citing its effect to denature polypeptide toxins beneath the skin and render the proteins harmless. In one prospective study by Nomura et al, box jellyfish sting victims reported a mean difference of 1.6 less pain on a 10 visual analog scale (VAS) when evaluating hot water treatment versus a comparison treatment of vinegar/meat tenderizer.⁶ In a prospective study by Loten et al, involving Portuguese man-o'-war stings, the effectiveness of hot water immersions versus ice packs were compared. After 20 minutes of treatment, 87% of the hot water group reported lessened pain compared to 33% treated with ice and radiating pain occurred less at 10% and 30% respectively.⁸

Local injury caused by envenomation may be painful, but it certainly does not merit an emergency situation. To avoid a costly trip to the emergency department and the unnecessary use of resources, the Straub study recommends onsite treatment for marine envenomation. While this approach may not prevent all ED cases, treating stings immediately may significantly reduce pain and lessen the need for medical attention.

Limitations of Study

The scope of this study was limited to one emergency department near Waikiki, a tourist destination, and does not represent all tropical emergency departments. As a result, the types of patients and cnidarian species will differ with location. The species under study may be different from ones found on the mainland United States and other continents, thus treatments may also be different.

Future Directions

This study indicates that, although painful, cnidarian stings generally do not require extensive and costly Emergency Department treatment. Additionally, the Hawai‘i non-resident demographic is especially prone to cnidarian stings and would benefit from a proactive sting prevention and education program, such as beach signs during jellyfi sh influxes, education of protective swimwear, and first aid and on-site treatment pamphlets. A community-based education effort can potentially decrease frequency, provide better outcomes, and lower costs of cnidarian stings in Hawai‘i.

Conclusion

The results of this study show Hawai‘i non-residents, men, and nighttime swimmers are the most at risk for cnidarian stings. Future about jellyfish influxes and treatments. Hospital admittance rate and patient vital signs suggested cnidarian stings are rarely more than a minor affliction, but used costly emergency services for treatment. The study also revealed a variance in the treatment given by emergency physicians. An established treatment protocol or an algorithm may be able to combat the sheer number of drugs given in the ED. Furthermore, supplemental research is needed to address the efficacy of IV and topical/oral treatments. Hopeful outcomes of supplemental research are to reduce the number of sting patients presented and to streamline performance in the ED.