Page 1855 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

1324 PART 11: Special Problems in Critical Care

the episode is common, and this aggravates the airway and alveolar probably caused by hypoxemia and hypotension. Infrequently, drown-
epithelial injury. ing may be complicated by rhabdomyolysis and hemolysis with dis-
The combination of alveolar flooding, loss of surfactant or its function, seminated intravascular coagulation. 60,61 These conditions may also
atelectasis, and alveolar damage may give rise to progressive hypoxemia contribute to acute tubular necrosis. Although patients with acute
from intrapulmonary shunting, which in severe cases may reach 70% kidney injury after drowning may require transient dialysis, recovery
of the cardiac output. 42-44 In about 40% of individuals who initially of renal function can be expected in most patients.
survive drowning, the injury culminates in ARDS hours to days after the ■
episode. 45,46 Hypoxemia necessitates treatment with supplemental oxy- MANAGEMENT
gen, usually at high inspired O fraction, which if prolonged, may super- General Measures: The management of the drowning victim involves
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impose pulmonary oxygen toxicity on ARDS. Fortunately, ARDS after four distinct, but interrelated phases. These are aquatic rescue, basic
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drowning is more amenable to resolution than ARDS from other causes. 46 life support, advanced life support, and postresuscitation care. The
Brain: Drowning is the second leading cause of brain death, after intensive care specialist is often responsible for postresuscitation
trauma, in children admitted to the pediatric ICU. The pathology is care, and should be familiar with predisposing factors and compli-
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that of global anoxia or severe hypoxia. Prolonged anoxia or hypoxia cating injuries including blunt trauma, alcohol and other drugs, and
produces diffuse neuronal damage, which if severe, compromises blood- preexisting medical conditions. These factors are easily overlooked in
brain barrier function, leading to cerebral edema. As edema develops, unconscious, critically ill patients, but they must be taken into con-
intracranial pressure (ICP) may increase, further decreasing cerebral sideration in each case because they may impact on the treatment and
perfusion pressure and exacerbating intracellular hypoxia. In severe prognosis of the patient.
cases, this may lead to uncal herniation. Profound increases in ICP are Alcohol and other centrally acting drugs are commonly implicated in
infrequent after drowning, but tend to appear more than 24 hours after adult drowning victims, especially in young males. Alcohol and seda-
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resuscitation of patients who present with neurologic dysfunction. tives, in particular, may complicate the patient’s initial ICU stay by exac-
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There is evidence that the increase in ICP reflects the severity of neuro- erbating hypothermia and hypotension and impairing the mental status
nal injury rather than a major cause of ongoing damage. 46,48 and respiratory drive. Drug screens and blood alcohol levels should be
The clinical differences between drowning and other causes of anoxic considered in all complicated drowning patients admitted to the ICU.
brain injury are minor, although there are potential mitigating effects Two other important factors, cardiac disease and cerebrovascular
40-42
of the diving reflex and hypothermia. In adults, the diving reflex is disease, can either predispose to or complicate drowning. Myocardial
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manifest mainly by bradycardia, while young children exposed to cold infarction, cardiac arrhythmias (including LQTS), cardiomyopathies,
water may exhibit the entire triad. 49,50 Drowning in cold water leading to immersion pulmonary edema, seizures, subarachnoid hemorrhage, and
rapid hypothermia slows cerebral metabolism, thereby postponing the in the diver, AGE have been implicated as causative or complicating
deleterious effects of anoxia. Drowning in cold water (below 5°C or factors in many drowning victims. Other predisposing factors include
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41°F) is associated with a better prognosis after rescue. 48 trauma, hypothermia, hypoglycemia, and depression. 42
In the immediate post-resuscitation environment of the ICU, these
Heart: The most important cardiac effects of drowning are atrial and events may require concerted diagnostic efforts. Electrocardiography
ventricular arrhythmias, in particular ventricular fibrillation. Studies of should be routinely obtained in these patients because the heart is a
drowning in animals have demonstrated hemolysis and rapid shifts in target of hypoxemia. Serial measurement of cardiac enzymes is useful
blood electrolyte composition after instillation of water into the lungs. for confirming the diagnosis of myocardial infarction. Acute intra-
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These responses correlated with the appearance of ventricular arrhyth- cranial hemorrhage or status epilepticus may need to be ruled out in
mias. Human studies have not confirmed significant electrolyte changes patients whose presentation is complicated by altered mental status.
even in patients with ventricular fibrillation, except for drowning in Recompression and HBO therapy should be considered in divers with
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the Dead Sea, which has far higher mineral content than other seawater. unexplained neurologic deficits (see section on Decompression Illness).
Victims of the Dead Sea may develop hypernatremia, hyperchloremia, Injuries to the spine and skull are common in drowning victims.
hypermagnesemia, and hypercalcemia after the episode because electro- These occur most often when a swimmer is body surfing or dives into
lytes are absorbed from the gastrointestinal tract after swallowing large shallow water and hits the head on the bottom or on a submerged
volumes of water during the episode. 54 object. Another common scenario involves a motor vehicle accident
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Human victims rarely aspirate enough water to produce significant that leaves the passenger submerged underwater. Burst fractures of the
electrolyte changes. Pathologic studies after drowning have generally cervical vertebrae resulting in tetraplegia have been reported in these
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demonstrated cardiac myocyte hypercontraction and hypereosino- settings. In addition, skin, middle ear, or sinus trauma sustained during
philic sarcomeres characteristic of catecholamine excess. These changes the episode may serve as entry portals for infection. 64
suggest that intense adrenergic stimulation contributes to the arrhyth-
mias after drowning. Thus, the etiology of ventricular fibrillation ICU Care: The drowning patient with respiratory insufficiency, post-
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in human beings is most likely related to hypoxemia, respiratory and cardiac arrest or arrhythmia, and altered mental status should be cared
metabolic acidosis, and catecholamine excess. A review of cases of chil- for in an ICU. Clinically, the patient may exhibit cyanosis, tachycardia,
dren with brain death also demonstrated that myocardial infarction was hypo- or hypertension, hypothermia, respiratory distress with frothy,
commonly associated with drowning. 56 blood-tinged sputum, diffuse crackles, and wheezing on examination.
The long QT syndrome (LQTS) has received a great deal of attention Initial laboratory evaluation often shows a metabolic acidosis (caused by
because these individuals are at risk for sudden death, particularly in lactic acid) and hypoxemia on arterial blood-gas analysis. Serum electro-
the water. 57,58 Genetic polymorphisms in cardiac ion channel LQTS- lytes, with the exception of a decreased bicarbonate concentration, are
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susceptibility genes and the polymorphic ventricular tachycardia- rarely abnormal, although drowning in unusual fluids can perturb the
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associated cardiac ryanodine receptor predisposes to ventricular serum electrolytes. Hypoglycemia is common. Hemolysis and rhabdo-
tachycardia (particularly torsades de pointes) and ventricular fibrilla- myolysis are usually modest and tend to occur early. Electrocardiographic
tion. Survivors of episodes of cardiac arrest while swimming who have abnormalities include evidence of ischemia or injury and ventricular and
no other cardiac risk factors should be tested for LQTS, and beta blocker atrial arrhythmias. Initial chest radiographic findings range from patchy
therapy is usually recommended. infiltrates to diffuse airspace disease (Fig. 132-3). A progressive increase
in parenchymal infiltrates over hours to days is not unusual.
Kidney: Acute kidney injury after drowning is reported far less fre-
quently than lung, brain, or cardiac injury. The renal complication Mechanical Ventilation: Mechanical ventilation can be challenging in
cited most often is oliguria attributable to acute tubular necrosis, the severely injured drowning victim. Atelectasis and pulmonary edema
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