Regarding submersion events, which ONE of the following statements is TRUE?
Answer: C: The terminology around drowning used to be very confusing. In 2002 the International Liaison Committee on Resuscitation (ILCOR) agreed on recommendations for unified drowning-related definitions and guidelines for reporting data. The term ‘drowning’ now refers to a process resulting in primary respiratory impairment from submersion/immersion in a liquid medium and implies a liquid–air interface is present at the entrance of the victim’s airway, preventing the victim from breathing air; the victim may die or live after the event.
Although differences observed between freshwater and saltwater aspirations in electrolyte and fluid imbalances are frequently discussed, they are rarely of any clinical significance for people who have experienced drowning. Most patients have fluid aspiration of <4 mL/kg. Fluid aspiration of at least 11 mL/kg is required for alterations in blood volume to occur, and aspiration of more than 22 mL/kg is required before significant electrolyte changes develop. Electrolyte abnormalities are usually minimal and transient except in prolonged arrest. Additionally, life-threatening changes in serum electrolytes are seldom seen, regardless of the type of water.
Multiple studies have been performed to evaluate prognostication rules but a decision tool has not been successfully and consistently validated. Various factors are often associated with a poor prognosis. These include a submersion time >10 minutes, resuscitation time >15–25 minutes, time to effective life support >10 minutes, Glasgow Coma Scale (GCS) <5, and pH on presentation <7.1. Ultimately, there are no indicators at the rescue site or in the hospital that are absolutely reliable with respect to death or survival. Furthermore, there are no established rules or consistent algorithms regarding length of resuscitation and therefore the decision to terminate resuscitation is an individual decision made on a case-by-case basis.
The Conn and Modell classification (1980) is a useful classification of the mental status after drowning: category A – awake; category B – conscious but obtunded; and category C – comatose. This classification provides an approximate estimate of the prognosis and can guide management.
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Regarding electrical injuries sustained by household current, which ONE of the following is TRUE?
Answer: D: The effects of an electrical current passing through the body are determined by several factors: the type of current, voltage, tissue resistance, current path and contact duration. In addition, the amperage of current affects the severity of injury. In Australia, the vast majority of household current is alternating current (AC) with a frequency of 50 Hz, as this is optimal for the transmission and use of electricity. As such, household current lies within the dangerous frequency range (40–150 Hz). It also spans the vulnerable period of the cardiac electrical potential, and is therefore capable of causing ventricular fibrillation. Voltage is the driving force behind the current. Most deaths are caused by low-voltage (<1000) exposure and are usually due to ventricular fibrillation occurring at the time of exposure. Household voltage in Australia is 240 V.
Although delayed arrhythmias are possible and predominantly seen in patients with a past medical history of cardiac disease, they are rare and usually transient in survivors. Death due to delayed arrhythmia is exceptionally rare. Therefore, cardiac monitoring is not indicated if a patient is asymptomatic and has a normal ECG on presentation and in general can be safely discharged home.
The most common mode of electrical shock in young children is from chewing or biting on electrical cords. Arcing of the current through the lips causes oral burns, with the oral commissure frequently involved. The burn may be full thickness, involving the mucosa, submucosa, muscle, nerves and blood vessels. Significant oedema and eschar formation follow within hours after the injury. Vascular injury to the labial artery is not immediately apparent because of vascular spasm, thrombosis and overlying eschar. The eschar usually falls off after 2–3 weeks, being replaced by granulation tissue and scarring that may cause considerable deformity. Severe bleeding from the labial artery occurs in up to 10% of cases when the eschar separates, usually after 5 days, but can occur up to 2 weeks after the injury.
Prediction of injuries from a knowledge of the current path is unreliable. Children who sustain hand wounds from electrical outlet injuries with no other injury and no evidence of cardiac or neurological involvement can be discharged after local wound care is provided and their home situation deemed safe.
Regarding injuries caused by lightning, which ONE of the following is TRUE?
Answer: A: Lightning causes a massive counter-shock to the myocardium and usually takes the form of asystole. Interestingly, sinus rhythm may return spontaneously due to the inherent automaticity of the heart. A secondary hypoxic cardiac arrest with deterioration to ventricular fibrillation and asytole may occur with concurrent respiratory arrest due to transient paralysis of the medullary respiratory centre and thoracic muscle spasm. Immediate institution of basic CPR in the field for those in asystole prevents secondary hypoxic cardiac arrest during the interval until cardiac function resumes spontaneously. This principle of first resuscitating those who appear dead is called reverse triage. There are reports of excellent recovery after lightening induced cardiac arrest. Additionally, transient autonomic disturbances may cause fixed, dilated pupils with an often unconscious patient after a lightning injury and therefore should not indicate a poor prognosis or brain death after a lightening strike. Burns due to lightning are common (up to 90%), but despite the massive energy and heat that lightning generates, its short duration and flash over effect play a protective role. As a result, deep burns occur in only 5% of victims. Lichtenberg figures (feathering, ferns or keraunographic markings) are cutaneous marks that are considered pathognomonic of lightning, but it is unclear whether they are actual burns. They may appear immediately but more often a few hours after injury. Burns are usually superficial and heal remarkably easy.
Transient paralysis (keraunoparalysis) and autonomic instability causing hypertension and peripheral vasospasm have been described primarily in the context of electrical injury due to lightning. Keraunoparalysis is characterized by flaccidity and complete loss of sensation of the affected limbs. Peripheral pulses are generally impalpable and the affected limb takes on a mottled, pale, blue appearance. Keraunoparalysis is self-limiting and resolves within 1–6 hours. If it does not resolve in a few hours, other causes should be considered.
Regarding altitude-related medical problems, which ONE of the following is TRUE?
Answer: A: AMS is a clinical syndrome characterized by headache, dizziness or light-headedness, gastrointestinal disturbances, and sleep disturbance. As the illness progresses, headache becomes more severe and vomiting and oliguria develop. The onset of ataxia and altered level of consciousness heralds high-altitude cerebral oedema (HACE) and requires immediate descent and treatment. Left untreated, severe AMS may progress to lifethreatening HACE or HAPE. Graded ascent with adequate time for acclimatization is the best prevention. Low-dose acetazolamide, at a dose of 125 mg bd, also provides effective prophylaxis against AMS.
The major predisposing factors are the rate of ascent and high sleeping altitude. It is not related to physical fitness or gender. In addition, age has little influence on susceptibility, with children being as susceptible as adults. Those older than 50 years of age tend to have less AMS.
Mild AMS is usually self-limiting and improves with an extra 12–26 hours of acclimatization if ascent is halted. Immediate descent is warranted if symptoms worsen and low-flow oxygen should be administered if available. Acetazolamide is very helpful in speeding acclimatization and aborting illness, especially when used early. The dosage regimen varies: 5 mg/kg/d orally in two or three divided doses is sufficient for prevention or treatment. Dexamethasone, 4 mg po/ IM/IV every 6 hours is also effective and can be used as an alternative but is best reserved for cases of moderate to severe AMS.
HAPE is a non-cardiogenic pulmonary oedema associated with markedly elevated pulmonary vascular resistance and pulmonary artery pressure. Rapid and controlled descent, with administration of oxygen, is the mainstay of therapy and is sufficient in most cases. Nifedipine reduces pulmonary artery pressures and seems to be an effective adjunctive therapy in the treatment of HAPE, whereas dexamathasone has no proven value. The recommended dose of nifedipine is 10–20 mg orally 6-hourly or 20–30 mg extended release 12-hourly.
Regarding acute radiation syndrome, which ONE of the following is TRUE?
Answer: A: Characteristic and relatively predictable signs and symptoms develop when a significant proportion of the body is exposed to a high level of penetrating radiation over a short period of time; these signs and symptoms are collectively referred to as acute radiation syndrome (ARS). The patient may initially be asymptomatic and a rapid decline in lymphocytes is one of the best early indicators of the extent of the radiation injury and plotting it on a nomogram may help to predict the clinical course. Four distinct phases are seen in the unfolding of ARS. In general, the higher the dose, the shorter is the duration of each phase and the more severe are the symptoms.
1. Prodromal phase: transient period of self-limiting symptoms. An autonomic nervous system response initiates gastrointestinal symptoms with nausea and vomiting, as well as anorexia and possibly diarrhoea (depending on dose) are the classic symptoms for this stage, which occur from minutes to days following exposure.
2. Latent phase: in this stage, the patient looks and feels generally healthy for a few hours or even up to a few weeks.
3. Manifest illness phase: symptoms depend on the specific syndrome and last from hours up to several months. Divided into three dose-dependant subsyndromes, in increasing order of severity.
a. Hematopoietic syndrome (dose >2 Gy):
b. Gastrointestinal syndrome (dose >6 Gy):
c. Cardiovascular/CNS syndrome (dose >20–30 Gy):
4. Recovery or death.
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