Case Study 21 Copd With Respiratory Failure Answers

After admission to the ICU, the patient was noted to be in acute lung injury (ALI), a subset of acute respiratory distress syndrome (ARDS). The diagnosis of ALI requires all three of the following:  (a) bilateral pulmonary infiltrates, (b) a PaO2:FiO2 ratio of ≤ 300 and (c) echocardiographic evidence of normal left atrial pressure or pulmonary-artery wedge pressure of ≤ 18 mm Hg (2). 

Low tidal volume ventilation (LTVV), also known as lung protective ventilation, has been demonstrated to significantly improve mortality in patients with ALI and ARDS (3).  In a study conducted by the ARDS Network comparing LTVV to traditional tidal volumes, patients were placed either on tidal volumes of 12 ml/kg predicted body weight or 6 ml/kg predicted body weight within 4 hr following randomization.  Tidal volumes in the 12 ml/kg group were reduced to as low as 4 ml/kg while keeping the plateau pressure ≤ 50 cm H2O, and tidal volumes in the 6 ml/kg group were reduced to as low as 4ml/kg while keeping the plateau pressure ≤ 30 cm H2O.  The trial was discontinued early because of the mortality difference between the two groups (31% in the 6 ml/kg group versus 40% in the 12 ml/kg group, p = 0.007). Ventilator-free days were also significantly higher in the LTVV group.

While patients with ALI and ARDS can be maintained with pressure-limited or volume-limited modes of ventilation, only volume assist-control ventilation was utilized in the ARDS Network multicenter randomized controlled trial that demonstrated a mortality benefit.

Noninvasive ventilation has not been demonstrated to be superior to endotracheal intubation in the treatment of ARDS or ALI and is not currently recommended (4).

This is a case of heavy metal poisoning with mercury.  The patient used mercury to clean coins.  Family members who had visited his house while he was hospitalized found several jars of mercury throughout his home.  The Environmental Protection Agency (EPA) was notified and visited the home.  They found aerosolized mercury levels of > 50,000 PPM and had the home immediately demolished. 

Alcoholic hallucinosis is a rare disorder occurring in 0.4 - 0.7% of alcohol-dependent inpatients (5).  Affected persons experience predominantly auditory but occasionally visual hallucinations.  Delusions of persecution may also occur.  However, in contrast to alcohol delirium, other alcohol withdrawal symptoms are not present and the sensorium is generally unaffected.

Delerium tremens (DT) occurs in approximately 5% of patients who withdraw from alcohol and is associated with a 5% mortality rate. DT typically occurs between 48 and 96 hr following the last drink and lasts 1-5 days.  DT is manifested by generalized alteration of the sensorium with vital sign abnormalities.  Death often results from arrhythmias, pneumonia, pancreatitis or failure to identify another underlying problem (6).  While DT certainly could have coexisted in this patient, an important initial step in the management of DT is to identify and treat alternative diagnoses.

Delirium is frequent among older patients in the ICU (7), and may be complicated by pneumonia and sepsis.  However, pneumonia and sepsis as causes for delirium are diagnoses of exclusion and should only be attributed after other possibilities have been ruled out. 

Frontal lobe stroke is unlikely, given the absence of other findings in the history or physical examination present to suggest an acute cerebrovascular event. 

In 1818, Dr. John Pearson coined the term erethism for the characteristic personality changes attributed to mercury poisoning (8).  Erethism is classically the first symptom in chronic mercury poisoning (9).  It is a peculiar form of timidity most evident in the presence of strangers and closely resembles an induced paranoid state.  In the past, when mercury was used in making top hats, the term “mad as a hatter” was used to describe the psychiatric manifestations of mercury intoxication.  Other neurologic manifestations include tremors, especially in patients with a history of alcoholism, memory loss, drowsiness and lethargy.  All of these were present in this patient. 

Acute respiratory failure (ALI/ARDS) can occur following exposure to inhalation of mercury fumes (10). Mercury poisoning has also been associated with acute kidney injury (11). 

Although all of the options mentioned above could possibly contribute to the development of delirium, only mercury poisoning would explain the constellation of findings of confusion, upper extremity tremors, visual hallucinations, somnolence and acute respiratory failure (ALI/ARDS).

Knowledge of the form of mercury absorbed is helpful in the management of such patients, as each has its own distinct characteristics and toxicity. There are three types of mercury: elemental, organic and inorganic. This patient had exposure to elemental mercury from broken thermometers. 

Elemental mercury is one of only two known metals that are liquid at room temperature and has been referred to as quicksilver (12). It is commonly found in thermometers, sphygmomanometers, barometers, electronics, latex paint, light bulbs and batteries (13).  Although exposure can occur transcutaneously or by ingestion, inhalation is the major route of toxicity.  Ingested elemental mercury is poorly absorbed and typically leaves the body unchanged without consequence (bioavailability 0.01% [13]). However, inhaled fumes are rapidly absorbed through the pulmonary circulation allowing distribution throughout the major organ systems.  Clinical manifestations vary based on the chronicity of the exposure (14).  Mercury readily crosses the blood-brain barrier and concentrates in the neuronal lysosomal dense bodies. This interferes with major cell processes such as protein and nucleic acid synthesis, calcium homeostasis and protein phosphorylation.  Acute exposure symptoms manifest within hours as gastrointestinal upset, chills, weakness, cough and dyspnea.

Inorganic mercury salts are earthly-appearing, red ore found historically in cosmetics and skin treatments.  Currently, most exposures in the United States occur from exposure through germicides or pesticides (15).  In contrast to elemental mercury, inorganic mercury is readily absorbed through multiple routes including the gastrointestinal tract.  It is severely corrosive to gastrointestinal mucosa (16).  Signs and symptoms include profuse vomiting and often-bloody diarrhea, followed by hypovolemic shock, oliguric renal failure and possibly death (12).

Organic mercury, of which methylmercury is an example, has garnered significant attention recently following several large outbreaks as a result of environmental contamination in Japan in 1956 (17) and grain contamination in Iraq in 1972 (18).  Organic mercury is well absorbed in the GI tract and collects in the brain, reaching three to six times the blood concentration (19).  Symptoms may manifest up to a month after exposure as bilateral visual field constriction, paresthesias of the extremities and mouth, ataxia, tremor and auditory impairments (12).  Organic mercury is also present in a teratogenic agent leading to development of a syndrome similar to cerebral palsy termed "congenital Minamata disease" (20).

The appropriate test depends upon the type of mercury to which a patient has been exposed.  After exposure to elemental or inorganic mercury, the gold standard test is a 24-hr urine specimen for mercury.  Spot urine samples are unreliable.  Urine concentrations of greater than 50 μg in a 24-hr period are abnormal (21).  This patient’s 24-hr urine level was noted to be 90 μg.  Elemental and inorganic mercury have a very short half-life in the blood.

Exposure to organic mercury requires testing hair or whole blood.  In the blood, 90% of methyl mercury is bound to hemoglobin within the RBCs.  Normal values of whole blood organic mercury are typically < 6 μg/L. This patient’s whole blood level was noted to be 26 μg/L.  This likely reflects the large concentration of elemental mercury the patient inhaled and the substantial amount that subsequently entered the blood.

Mercury levels can be reduced with chelating agents such as succimer, dimercaprol (also known as British anti-Lewisite (BAL)) and D-penicillamine, but their effect on long-term outcomes is unclear (22-25).

И я меньше всего хотел, чтобы кто-нибудь в севильском морге завладел ею. - И вы послали туда Дэвида Беккера? - Сьюзан все еще не могла прийти в.  - Он даже не служит у.

Стратмор был поражен до глубины души. Никто никогда не позволял себе говорить с заместителем директора АНБ в таком тоне.

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