Environmental 4:
Near Drowning Portal
Introduction/Definition
A near-drowning patient is defined as anyone needing rescue from submersion. Technically, the term drowning is usually applied to on-scene fatalities and those individuals not responding to initial resuscitation.
Pathophysiology
The most common mechanism of immediate mortality is simple asphyxiation. Both aspiration and laryngospasm appear to play a role. The quantity of water aspirated is usually not a major factor, as most people aspirate 4 cc/kg or less. For this reason, fluid and electrolyte abnormalities are rarely a source of clinical concern in either fresh or salt water drowning.
Post-resuscitation morbidity is commonly due to pulmonary alveolar injury with non-cardiogenic pulmonary edema and hypoxia. This may develop into adult respiratory distress syndrome. This phenomenon, often referred to as secondary drowning, may develop after a relatively asymptomatic interval of 4 hours or more and necessitates a period of cautious observation, even for those patients who appear relatively well after rescue. (See treatment section below.)
Chemical and infectious pneumonia are occasionally seen.
Delayed mortality and long-term morbidity is primarily due to degree and duration of cerebral hypoxia. As might be expected, duration of submersion, initial LOC, and need for CPR are the major determinants of outcome, but exceptions to this rule do occur. Statistically, few people survive neurologically intact after 10 to 15 minutes of submersion. The mortality rate of those needing CPR at the scene may be as high as 80% to 90% (vs approximately 0.5% in patients conscious after rescue). However, neurologically intact, long-term survival has occurred in patients submerged up to 1 hour and in those with prolonged coma after resuscitation. This is most often reported in children (occasionally, also in adults) immersed in very cold (< 10°C [50°F]) water. For comparison, midsummer surface temperatures of Minnesota lakes are > 23°C (73°F); midwinter temperatures, of course, approach freezing. Even using the most comprehensive indices, long-term outcome can be predicted at time of rescue with no more than about 90% accuracy.
Complicating Factors:
- Spinal injury and other types of trauma may accompany near drowning.
- Hypothermia: The role of hypothermia is difficult to simplify. On one hand, hypothermia may represent an additional treatable cause of mortality in near drowning. On the other hand, most cases of unexpectedly good outcome have occurred in cold-water (< 10°C [50°F]) immersion. Low water temperature rather than low body temperature, per se, seems to be the major determinant of survival in prolonged immersion.
Rescue and Resuscitation at the Scene:
- Decision to Rescue and Resuscitate: As indicated, few patients survive neurologically intact after 10 to 15 minutes of submersion in water > 15°C (60°F). Survival rates may be extended for younger patients and in colder water. Therefore, use submersion time as only one measure in the decision to initiate resuscitation. Weigh all factors of an individual situation.
- Protect the c-spine as much as possible during rescue and resuscitation.
- Heimlich and other drainage procedures are probably not useful.
- In an unresponsive patient, open the airway and initiate BLS/ALS measures as needed. Adequate BLS may be difficult and unsafe in the water. Move the patient to a solid working area as soon as possible.
- Institute passive re-warming.
Continued Resuscitation (In Hospital):
- Continue BLS/ALS measures as indicated.
- Ensure adequate oxygen saturation with supplemental O2; for those unable to maintain an O2 sat above about 90%, you may use CPAP/BiPAP (if the patient is responsive). If the patient is unresponsive or unable to saturate with CPAP/BiPAP, he or she will require intubation and bag assist (also with 100% O2) or mechanical ventilation and PEEP
- Treat Hypothermia: For patients with temperatures above 34°C (93°F), use passive and external re-warming; for patients with temperatures in the range from 30°C to 34°C (86°F to 93°F), consider active core re-warming; and for those patients with temperatures less than 30°C (86°F), use core re-warming. (Vol III—ENV1 Hypothermia) In the absence of other factors incompatible with survival, continue the resuscitation until the body temperature is above 32°C (90°F) before terminating resuscitative efforts. Do not consider the patient dead until warm and dead.
Continuation/Termination of Resuscitation:
The decision to terminate resuscitation at this point should be influenced mainly by response to resuscitation, as in any other case of cardiac arrest. Consider other factors (hypothermia, cold-water immersion, or very young age). No foolproof formula or guideline exists for this decision.
Post-Resuscitation Care:
Intensity and specific components of post-resuscitation care depend on requirements of resuscitation. Patients requiring even supplemental O2 at any point should probably be transferred to an intensive care setting.
As mentioned, even patients requiring minimal resuscitative efforts may be subject to the development of respiratory problems 4 or more hours later. Although some authors suggest that asymptomatic patients may be discharged immediately, the safest reasonable recommendation is that any patient requiring rescue from submersion be observed in a hospital setting for 6 to 8 hours. If the patient has required only minimal resuscitation (for example, spontaneous breathing after rescue) and is asymptomatic with normal exam and O2 sat, observation can probably be carried out in a non-intensive setting, with transfer initiated at any sign of developing cough, decreased sat, or other respiratory compromise. Patients asymptomatic at 6 to 8 hours may be safely discharged.