Cyanide Poisoning

Overview

Definition

Cyanide is a highly lethal mitochondrial toxin causing death within minutes to hours of exposure.

Epidemiology

• Human exposures to cyanide 1993–2002: 3165 exposures (2.5% fatal)
• Annual incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency in the United States: 5,000–10,000 smoke inhalation Smoke Inhalation Carbon Monoxide Poisoning deaths
• Industrial exposure and suicide Suicide Suicide is one of the leading causes of death worldwide. Patients with chronic medical conditions or psychiatric disorders are at increased risk of suicidal ideation, attempt, and/or completion. The patient assessment of suicide risk is very important as it may help to prevent a serious suicide attempt, which may result in death. Suicide by cyanide poisoning occur mostly in men.

Etiology

• Domestic fires:
  • Most common cause of cyanide poisoning
  • Byproduct of synthetic product combustion (plastic, paints)
• Diet: ingestion of amygdalin (cyanogenic glucoside in apricot seeds)
• Medical:
  • Side effect of nitroprusside Nitroprusside A powerful vasodilator used in emergencies to lower blood pressure or to improve cardiac function. It is also an indicator for free sulfhydryl groups in proteins. Nitrates use (either a high dose or long-term use) 
  • Short-acting medication for hypertensive emergency Hypertensive emergency A condition of markedly elevated blood pressure with diastolic pressure usually greater than 120 mm hg. Malignant hypertension is characterized by widespread vascular damage, papilledema, retinopathy, hypertensive encephalopathy, and renal dysfunction. Uncontrolled Hypertension results in cyanide release
• Suicide Suicide Suicide is one of the leading causes of death worldwide. Patients with chronic medical conditions or psychiatric disorders are at increased risk of suicidal ideation, attempt, and/or completion. The patient assessment of suicide risk is very important as it may help to prevent a serious suicide attempt, which may result in death. Suicide or homicide: potassium Potassium An element in the alkali group of metals with an atomic symbol k, atomic number 19, and atomic weight 39. 10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the water-electrolyte balance. Hyperkalemia cyanide, sodium Sodium A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23. Hyponatremia cyanide
• Industrial: manufacturing workplace exposure

Pathophysiology and Clinical Presentation

Pathophysiology

• Absorbed through the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions, lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy, mucous membranes, or GI tract
• Quickly distributed throughout the body
• Major mechanism of action:
  • Inhibits the mitochondrial electron transport chain Electron transport chain The electron transport chain (ETC) sends electrons through a series of proteins, which generate an electrochemical proton gradient that produces energy in the form of adenosine triphosphate (ATP). Electron Transport Chain (ETC) by the inhibition of complex IV (cytochrome c oxidase Oxidase Neisseria, a3 subunit) as it binds to ferric iron Iron A metallic element with atomic symbol fe, atomic number 26, and atomic weight 55. 85. It is an essential constituent of hemoglobins; cytochromes; and iron-binding proteins. It plays a role in cellular redox reactions and in the transport of oxygen. Trace Elements (Fe³⁺)
  • Result: blockage of oxidative phosphorylation Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Post-translational Protein Processing and inhibition of aerobic ATP production
  • ATP is then produced primarily by the anaerobic pathway, resulting in lactic acid production and metabolic acidosis Acidosis A pathologic condition of acid accumulation or depletion of base in the body. The two main types are respiratory acidosis and metabolic acidosis, due to metabolic acid build up. Respiratory Acidosis.
  • Result: functional histotoxic hypoxia Hypoxia Sub-optimal oxygen levels in the ambient air of living organisms. Ischemic Cell Damage:
    • Inability to use O₂ due to poisoned electron chain
    • Especially deleterious to the cardiovascular and central nervous systems
• Additional contributing mechanisms of cyanide:
  • Inhibition of antioxidants Antioxidants Naturally occurring or synthetic substances that inhibit or retard oxidation reactions. They counteract the damaging effects of oxidation in animal tissues. Cell Injury and Death
  • Induction of apoptotic cell death Cell death Injurious stimuli trigger the process of cellular adaptation, whereby cells respond to withstand the harmful changes in their environment. Overwhelmed adaptive mechanisms lead to cell injury. Mild stimuli produce reversible injury. If the stimulus is severe or persistent, injury becomes irreversible. Apoptosis is programmed cell death, a mechanism with both physiologic and pathologic effects. Cell Injury and Death
  • Inhibition of gamma-aminobutyric acid ( GABA GABA The most common inhibitory neurotransmitter in the central nervous system. Receptors and Neurotransmitters of the CNS) formation → risk of seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures
  • Binds to hemoglobin → cyanohemoglobin (unable to transport O₂)
• Cyanide metabolism:
  • Detoxified by the rhodanese enzyme
  • Converts cyanide to water-soluble thiocyanate (needs sulfur), which is excreted in urine

Clinical presentation

Symptoms develop within seconds to minutes.

• Breath may have a bitter or almond odor.
• Skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions:
  • Flushed or cherry red
  • Cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination (more common)
  • Irritant dermatitis Dermatitis Any inflammation of the skin. Atopic Dermatitis (Eczema)
• Cardiovascular:
  • Tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children/ hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
  • Progression to bradycardia Bradycardia Bradyarrhythmia is a rhythm in which the heart rate is less than 60/min. Bradyarrhythmia can be physiologic, without symptoms or hemodynamic change. Pathologic bradyarrhythmia results in reduced cardiac output and hemodynamic instability causing syncope, dizziness, or dyspnea. Bradyarrhythmias/ hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension
  • Dysrhythmia, cardiac arrest Cardiac arrest Cardiac arrest is the sudden, complete cessation of cardiac output with hemodynamic collapse. Patients present as pulseless, unresponsive, and apneic. Rhythms associated with cardiac arrest are ventricular fibrillation/tachycardia, asystole, or pulseless electrical activity. Cardiac Arrest
• Respiratory:
  • Tachypnea Tachypnea Increased respiratory rate. Pulmonary Examination/ hyperventilation Hyperventilation A pulmonary ventilation rate faster than is metabolically necessary for the exchange of gases. It is the result of an increased frequency of breathing, an increased tidal volume, or a combination of both. It causes an excess intake of oxygen and the blowing off of carbon dioxide. Respiratory Alkalosis (reduced PaCO₂)
  • Progression to respiratory depression/failure 
  • Pulmonary edema Pulmonary edema Pulmonary edema is a condition caused by excess fluid within the lung parenchyma and alveoli as a consequence of a disease process. Based on etiology, pulmonary edema is classified as cardiogenic or noncardiogenic. Patients may present with progressive dyspnea, orthopnea, cough, or respiratory failure. Pulmonary Edema
• Neurologic:
  • Headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess
  • Vertigo Vertigo Vertigo is defined as the perceived sensation of rotational motion while remaining still. A very common complaint in primary care and the ER, vertigo is more frequently experienced by women and its prevalence increases with age. Vertigo is classified into peripheral or central based on its etiology. Vertigo
  • Dizziness Dizziness An imprecise term which may refer to a sense of spatial disorientation, motion of the environment, or lightheadedness. Lateral Medullary Syndrome (Wallenberg Syndrome)
  • Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures
  • Coma Coma Coma is defined as a deep state of unarousable unresponsiveness, characterized by a score of 3 points on the GCS. A comatose state can be caused by a multitude of conditions, making the precise epidemiology and prognosis of coma difficult to determine. Coma
  • Anoxic brain injury Anoxic Brain Injury Persistent Vegetative State and permanent brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification damage
• Nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics and vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia 
• Rhabdomyolysis Rhabdomyolysis Rhabdomyolysis is characterized by muscle necrosis and the release of toxic intracellular contents, especially myoglobin, into the circulation. Rhabdomyolysis
• Renal failure Renal failure Conditions in which the kidneys perform below the normal level in the ability to remove wastes, concentrate urine, and maintain electrolyte balance; blood pressure; and calcium metabolism. Renal insufficiency can be classified by the degree of kidney damage (as measured by the level of proteinuria) and reduction in glomerular filtration rate. Crush Syndrome
• Hepatic necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage

Diagnosis and Management

Diagnosis

History and physical exam:

• History of exposure
• Bitter/almond smell Smell The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy
• Color change of skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions (flushed/cyanotic)
• Characteristic symptoms

Laboratory tests:

• Severe metabolic acidosis Acidosis A pathologic condition of acid accumulation or depletion of base in the body. The two main types are respiratory acidosis and metabolic acidosis, due to metabolic acid build up. Respiratory Acidosis with anion gap Anion gap Metabolic Acidosis
• ↑ Lactic acid
• Narrowed venous-arterial PO₂ gradient (venous hyperoxia)
• Blood cyanide level (not very reliable test)
• Glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance (to evaluate for hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia)
• Other tests to obtain:
  • Carboxyhemoglobin Carboxyhemoglobin Carbon Monoxide Poisoning and methemoglobin: Rule out concomitant carbon monoxide Carbon monoxide Carbon monoxide (CO). A poisonous colorless, odorless, tasteless gas. It combines with hemoglobin to form carboxyhemoglobin, which has no oxygen carrying capacity. The resultant oxygen deprivation causes headache, dizziness, decreased pulse and respiratory rates, unconsciousness, and death. Carbon Monoxide Poisoning (CO) exposure and ingestion of other drugs.
  • Acetaminophen Acetaminophen Acetaminophen is an over-the-counter nonopioid analgesic and antipyretic medication and the most commonly used analgesic worldwide. Despite the widespread use of acetaminophen, its mechanism of action is not entirely understood. Acetaminophen and salicylate levels: Rule out coingestion of other drugs.

Management

General considerations:

• Address any suspected cyanide poisoning quickly because of high mortality Mortality All deaths reported in a given population. Measures of Health Status.
• Can be hard to diagnose/recognize
• Suspect in any smoke inhalation Smoke Inhalation Carbon Monoxide Poisoning victim.

Decontamination:

• Remove patient from the source.
• Remove clothes.
• Cleanse wounds.
• Administer activated charcoal Charcoal An amorphous form of carbon prepared from the incomplete combustion of animal or vegetable matter, e.g., wood. The activated form of charcoal is used in the treatment of poisoning. Antidotes of Common Poisonings in the case of oral ingestion.

Resuscitation Resuscitation The restoration to life or consciousness of one apparently dead. . Neonatal Respiratory Distress Syndrome:

• Assess airway Airway ABCDE Assessment, breathing, circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment (ABC).
• Secure airway Airway ABCDE Assessment and provide high flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure O₂ (use of hyperbaric oxygenation Hyperbaric Oxygenation The therapeutic intermittent administration of oxygen in a chamber at greater than sea-level atmospheric pressures (three atmospheres). It is considered effective treatment for air and gas embolisms, smoke inhalation, acute carbon monoxide poisoning, caisson disease, clostridial gangrene, etc. The list of treatment modalities includes stroke. Altitude Sickness is controversial).
• IV fluids IV fluids Intravenous fluids are one of the most common interventions administered in medicine to approximate physiologic bodily fluids. Intravenous fluids are divided into 2 categories: crystalloid and colloid solutions. Intravenous fluids have a wide variety of indications, including intravascular volume expansion, electrolyte manipulation, and maintenance fluids. Intravenous Fluids and pressors if needed
• Glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance administration if hypoglycemic
• Benzodiazepines Benzodiazepines Benzodiazepines work on the gamma-aminobutyric acid type A (GABAA) receptor to produce inhibitory effects on the CNS. Benzodiazepines do not mimic GABA, the main inhibitory neurotransmitter in humans, but instead potentiate GABA activity. Benzodiazepines for seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures 

Antidotes:

• Hydroxocobalamin (vitamin B₁₂) directly binds cyanide molecules and is the preferred treatment. 
• Sodium Sodium A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23. Hyponatremia thiosulfate acts as a sulfur donor for the enzyme rhodanese to convert cyanide to excretable thiocyanate.
• Nitrites ( sodium nitrite Sodium nitrite Nitrous acid sodium salt. Used in many industrial processes, in meat curing, coloring, and preserving, and as a reagent in analytical chemistry techniques. It is used therapeutically as an antidote in cyanide poisoning. The compound is toxic and mutagenic and will react in vivo with secondary or tertiary amines thereby producing highly carcinogenic nitrosamines. Nitrates or amyl nitrite Amyl nitrite A vasodilator that is administered by inhalation. It is also used recreationally due to its supposed ability to induce euphoria and act as an aphrodisiac. Nitrates) induce methemoglobinemia Methemoglobinemia Methemoglobinemia is a condition characterized by elevated levels of methemoglobin in the blood. Methemoglobin is the oxidized form of hemoglobin, where the heme iron has been converted from the usual ferrous (Fe2+) to the ferric (Fe3+) form. The Fe3+ form of iron cannot bind O2, and, thus, leads to tissue hypoxia. Methemoglobinemia:
  • Converts ferrous iron Iron A metallic element with atomic symbol fe, atomic number 26, and atomic weight 55. 85. It is an essential constituent of hemoglobins; cytochromes; and iron-binding proteins. It plays a role in cellular redox reactions and in the transport of oxygen. Trace Elements (Fe²⁺) to Fe³⁺
  • Fe³⁺ binds cyanide and avidly forms cyanmethemoglobin.
  • Do not use for concomitant CO poisoning CO poisoning Carbon monoxide (CO) is an odorless, colorless, tasteless, nonirritating gas formed by hydrocarbon combustion (e.g., fires, car exhaust, gas heaters). Carbon monoxide has a higher affinity to hemoglobin than oxygen, forming carboxyhemoglobin (COHb). Increased levels of COHb lead to tissue hypoxia and brain damage. Carbon Monoxide Poisoning as induction of methemoglobinemia Methemoglobinemia Methemoglobinemia is a condition characterized by elevated levels of methemoglobin in the blood. Methemoglobin is the oxidized form of hemoglobin, where the heme iron has been converted from the usual ferrous (Fe2+) to the ferric (Fe3+) form. The Fe3+ form of iron cannot bind O2, and, thus, leads to tissue hypoxia. Methemoglobinemia can be lethal.

Differential Diagnosis

• Methemoglobinemia Methemoglobinemia Methemoglobinemia is a condition characterized by elevated levels of methemoglobin in the blood. Methemoglobin is the oxidized form of hemoglobin, where the heme iron has been converted from the usual ferrous (Fe2+) to the ferric (Fe3+) form. The Fe3+ form of iron cannot bind O2, and, thus, leads to tissue hypoxia. Methemoglobinemia: a condition of elevated methemoglobin containing oxidized Fe³⁺ instead of Fe²⁺. Methemoglobin does not bind BIND Hyperbilirubinemia of the Newborn O₂. Methemoglobinemia Methemoglobinemia Methemoglobinemia is a condition characterized by elevated levels of methemoglobin in the blood. Methemoglobin is the oxidized form of hemoglobin, where the heme iron has been converted from the usual ferrous (Fe2+) to the ferric (Fe3+) form. The Fe3+ form of iron cannot bind O2, and, thus, leads to tissue hypoxia. Methemoglobinemia can be caused by nitrates Nitrates Nitrates are a class of medications that cause systemic vasodilation (veins > arteries) by smooth muscle relaxation. Nitrates are primarily indicated for the treatment of angina, where preferential venodilation causes pooling of blood, decreased preload, and ultimately decreased myocardial O2 demand. Nitrates, dapsone Dapsone A sulfone active against a wide range of bacteria but mainly employed for its actions against Mycobacterium leprae. Its mechanism of action is probably similar to that of the sulfonamides which involves inhibition of folic acid synthesis in susceptible organisms. It is also used with pyrimethamine in the treatment of malaria. Antimycobacterial Drugs, and local anesthetics Anesthetics Agents that are capable of inducing a total or partial loss of sensation, especially tactile sensation and pain. They may act to induce general anesthesia, in which an unconscious state is achieved, or may act locally to induce numbness or lack of sensation at a targeted site. Anesthesiology: History and Basic Concepts and causes tissue hypoxia Hypoxia Sub-optimal oxygen levels in the ambient air of living organisms. Ischemic Cell Damage. Presentation includes cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination, headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess, dizziness Dizziness An imprecise term which may refer to a sense of spatial disorientation, motion of the environment, or lightheadedness. Lateral Medullary Syndrome (Wallenberg Syndrome), nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics, seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures, shortness of breath Shortness of breath Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea, and/or arrhythmias. Methemoglobinemia Methemoglobinemia Methemoglobinemia is a condition characterized by elevated levels of methemoglobin in the blood. Methemoglobin is the oxidized form of hemoglobin, where the heme iron has been converted from the usual ferrous (Fe2+) to the ferric (Fe3+) form. The Fe3+ form of iron cannot bind O2, and, thus, leads to tissue hypoxia. Methemoglobinemia is diagnosed with blood gas and treated with methylene blue and vitamin C Vitamin C A six carbon compound related to glucose. It is found naturally in citrus fruits and many vegetables. Ascorbic acid is an essential nutrient in human diets, and necessary to maintain connective tissue and bone. Its biologically active form, vitamin C, functions as a reducing agent and coenzyme in several metabolic pathways. Vitamin C is considered an antioxidant. Water-soluble Vitamins and their Deficiencies administration. 
• Carbon monoxide Carbon monoxide Carbon monoxide (CO). A poisonous colorless, odorless, tasteless gas. It combines with hemoglobin to form carboxyhemoglobin, which has no oxygen carrying capacity. The resultant oxygen deprivation causes headache, dizziness, decreased pulse and respiratory rates, unconsciousness, and death. Carbon Monoxide Poisoning poisoning: an odorless, tasteless, colorless, nonirritating gas formed by hydrocarbon combustion (fires, car exhaust, gas heaters). Carbon monoxide Carbon monoxide Carbon monoxide (CO). A poisonous colorless, odorless, tasteless gas. It combines with hemoglobin to form carboxyhemoglobin, which has no oxygen carrying capacity. The resultant oxygen deprivation causes headache, dizziness, decreased pulse and respiratory rates, unconsciousness, and death. Carbon Monoxide Poisoning has a higher affinity to hemoglobin than O₂ and forms carboxyhemoglobin Carboxyhemoglobin Carbon Monoxide Poisoning, which results in impaired O₂ transport and utilization. Features include confusion, headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess, dizziness Dizziness An imprecise term which may refer to a sense of spatial disorientation, motion of the environment, or lightheadedness. Lateral Medullary Syndrome (Wallenberg Syndrome), rosy cheeks Cheeks The part of the face that is below the eye and to the side of the nose and mouth. Melasma, coma Coma Coma is defined as a deep state of unarousable unresponsiveness, characterized by a score of 3 points on the GCS. A comatose state can be caused by a multitude of conditions, making the precise epidemiology and prognosis of coma difficult to determine. Coma, and death. Diagnosis is established clinically and confirmed by blood gas. Management is 100% O₂ and, if failed, hyperbaric oxygenation Hyperbaric Oxygenation The therapeutic intermittent administration of oxygen in a chamber at greater than sea-level atmospheric pressures (three atmospheres). It is considered effective treatment for air and gas embolisms, smoke inhalation, acute carbon monoxide poisoning, caisson disease, clostridial gangrene, etc. The list of treatment modalities includes stroke. Altitude Sickness. 
• Drug ingestion: various drugs can produce symptoms of poisoning similar to cyanide. The drugs include tricyclic antidepressants Tricyclic antidepressants Tricyclic antidepressants (TCAs) are a class of medications used in the management of mood disorders, primarily depression. These agents, named after their 3-ring chemical structure, act via reuptake inhibition of neurotransmitters (particularly norepinephrine and serotonin) in the brain. Tricyclic Antidepressants, salicylates, organophosphates, isoniazid Isoniazid Antibacterial agent used primarily as a tuberculostatic. It remains the treatment of choice for tuberculosis. Antimycobacterial Drugs, and strychnine. Detailed history and a high index of clinical suspicion are essential for correct diagnosis. Management depends on the offending agent.