Hypoxic, Hypotensive, & Hypothermic: Focused Resuscitation in Drowning
An 8 year old female is skating on a frozen pond in February. She falls through the ice and disappears under the surface of the water. Her friend runs up the street to get her father who arrives within 5 minutes to find her floating amongst the broken ice. He is able to pull her from the water. She is unconscious, not breathing, and is cold to the touch. Pulse is not readily palpable. The ambulance is just arriving...
Drowning, which has been universally defined as “the process of experiencing respiratory impairment from submersion/immersion in liquid” by the World Health Organization1, is widespread throughout the globe and is a significant burden of disease. Although accurate epidemiology is hindered by reporting issues, there are a few striking statistics that highlight the problem: in the United States, 4628 individuals died in 20162, with younger patients disproportionately suffering morbidity and mortality. That’s more than 12 per day!
Although the definition focuses on respiratory dysfunction, it is important to understand that after a drowning event, there are three distinct outcomes: no morbidity, morbidity, or mortality. The morbidity category encompasses a wide spectrum of disease with neurologic sequelae being the primary, and often devastating, manifestation.
The pathophysiology of drowning is intuitive3. Voluntary breath holding is limited by the patient’s panicked and inefficient efforts to stay above water. Eventually, small aspiration occurs when an involuntary inspiration takes place. Laryngospasm ensues, preventing additional breaths even if the patient returns to the surface temporarily. Systemic hypoxemia causes unconsciousness. Breath attempts cease but the already aspirated fluid leads to a ventilation-perfusion mismatch due to direct alveolar damage, surfactant washout, bronchospasm, atelectasis, and pulmonary edema. Hypoxemia continues and eventually leads to irreversible neuronal injury in the brain with additional injury to the cardiovascular and renal systems.
Underlying cardiovascular or neurologic disease (particularly epilepsy) should be considered in every drowning patient, but these rarely impact initial resuscitation. Depending on circumstances (falls, boating or diving accident), the real possibility of trauma must also be taken into account. The Wilderness Medicine Society notes that the prevalence of concurrent cervical spine injury is low and does not recommend routine immobilization unless there is a specific concern for neck trauma, such as focal neurologic deficit4. At no time should immobilization delay or hamper resuscitation.
Rescue, obviously, is the essential intervention in order to prevent or shorten cerebral hypoxia. However, the rescuer is at significant risk of harm or death in many circumstances. Attempts at rescue should only be made by those with the appropriate training and equipment. Lay persons can attempt to extend or throw rescue devices to those actively drowning but should avoid entering the water themselves. The details of proper rescue technique are usually beyond the purview of the emergency physician, but one point worth mentioning is that in-water resuscitation (rescue ventilations) should be considered only if the patient has a pulse and there is a significant delay to extrication.
Upon presentation to the ED, patients can be graded using the Szpilman Classification for Drowning to gauge the severity of illness and predict mortality5. This is based on physical exam only, where patients presenting without cough and having clear lungs score a Grade 1 classification predicting a 0% mortality rate. However, patients with hypotension, diffuse rales, and foam in the airway have a 20% mortality rate. Those who present in cardiac arrest have only 7% chance of survival.
Asymptomatic patients who are well-appearing and normoxic need no diagnostic testing. The Wilderness Medicine Society recommends discharge after 4-6 hours of emergency department observation. Even those initially symptomatic or requiring supplemental oxygen can be discharged if the vitals have normalized within this timeframe. Keep in mind that chest x-rays done in the emergency department are not predictive of clinical course6. Those with respiratory symptoms but otherwise stable do not need an extensive workup though may require admission for prolonged supplemental oxygen requirements with or without non-invasive positive pressure.
Those who are critically ill need aggressive interventions and diagnostics. Initial assessment should include an extended careful pulse check of about 30 seconds because starting compressions on a hypothermic heart that is still beating may initiate a lethal dysrhythmia. Ongoing pulse oximetry and core temperature measurement, in addition to standard cardiac monitoring, is essential. As the primary insult is always hypoxia, focus on reversing this factor is always the primary objective. Immediate supplemental oxygen and positive-pressure ventilation should be initiated as needed. Escalating to intubation in order to both reverse hypoxia and protect the airway from further aspiration may be appropriate. Hyperoxia should be avoided. Mechanical ventilation should follow ARDSNet protocol.
Patients are typically hypotensive. Although this can be multifactorial, immersion diuresis can result in profound hypovolemia by the time the patient is being resuscitated by EMS or in the ED. Crystalloids should be bolused empirically to correct this and support hemodynamics. Refractory hypotension may require vasopressor support.
Hypothermia is almost always a complication of drowning and needs to be reversed rapidly. There is a misconception that cold water immersion is protective. The more severe the accidental hypothermia is, the longer submersion time can be presumed and the worse cerebral hypoxia7. Low core temperature will prevent ROSC, depress cardiac function, and worsen systemic hypotension. Furthermore, standard ACLS medications and defibrillations may be rendered ineffective until normothermia is achieved8. There are many active external and internal techniques for reversing hypothermia: forced-air warming blankets, radiant heaters, warm water bath, warming mattress, warmed IVFs, warmed inhaled oxygen, warmed bladder irrigation, peritoneal lavage, thoracic lavage, hemodialysis, extracorporeal membrane oxygenation, and cardiopulmonary bypass9.
For those found in cardiac arrest, the above considerations should be intervened on simultaneously if ROSC is to be achieved. Patients are usually in PEA after a tachy-brady decompensation and will remain so until hypoxia, hypothermia, and hypotension are reversed. Although no studies have demonstrated benefit in drowning patients, therapeutic hypothermia should be started after ROSC as per standard ACLS protocols as harm has never been demonstrated.
Advance centers may have ECMO available as a resource to use in patients presenting after a drowning event. A recent retrospective review of 247 drowning patients who received extracorporeal life support before, during, or after cardiac arrest showed a survival benefit[x]. Not surprisingly, those who never had an initial arrest before the extracorporal life support was utilized had the best outcomes, suggesting that early intervention should be considered before acute decompensation.
Take Home Points:
Drowning encompasses a spectrum of outcomes from asymptomatic presentations to vegetative states to death
Modifiers such as dry, wet, secondary, delayed, salt-water, fresh-water, active, passive are no longer used as they do not exist or meaningfully impact management
Resuscitation should focus on reversing the three H’s: Hypoxia, Hypothermia, and Hypotension
Ryan Barnicle is a current second year resident at Stony Brook, former lifeguard, and EMT-B.
A new definition of drowning: towards documentation and prevention of a global public health problem. Beeck et al. Bulletin of the World Health Organization. November 2015.
Number of deaths, death rates, and age-adjusted death rates for injury deaths, by mechanism and intent of death: United States, 2016. National Vital Statistics Reports, Vol. 67, No. 5, July 26, 2018
Szpilman D, Bierens JJ, Handley AJ, et al. Drowning. N Engl J Med. 2012; 366(22):2102-2110.
Practice Guidelines for the Prevention and Treatment of Drowning. Wilderness Medical Society. Wilderness and Environmental Medicine, 27, 236-251. 2016.
Near-drowning and drowning classification: a proposal to stratify mortality based on the analysis of 1,831 cases. Szpilman et al. Chest. 1997.
Gregorakos L, Markou N, Psalida V, et al. Near-drowning: clinical course of lung injury in adults. Lung. 2009; 187(2):93- 97.
Association of water temperature and submersion duration and drowning outcome. Quan et al. Resuscitation 85 (2014) 790–794.
Vanden Hoek, TL, Morrison LJ, American Heart Association, et al. 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science. Part 12: Cardiac arrest in special situations. Circulation. 2010; 122(18):S829-S861
Drowning In The Adult Population: Emergency Department Resuscitation And Treatment. Schmidt A, Sempsrott J. EB Medicine – Emergency Medicine Practice 17, 5. May 2015.
Extracorporeal life support for victims of drowning. Burke et al. Resuscitation 104 (2016) 19-23.