EMERGENCY MEDICINE -TABLE OF CONTENTS : To read a chapter click on its title

 

EMERGENCY MEDICINE -TABLE OF CONTENTS: To read a chapter click on its title 

Note: The site is under  development.  Contents are gradually expanding


Emergency medicine- a free book online


Emergency airway management and ventilation procedures

Upper airway obstruction


Major trauma -assessment and management and wound care. An overview

Head trauma-brain trauma







Edema (Oedema): Basic principles of differential diagnosis and management 


Altered mental status and coma. Diagnosis and treatment

Acute abdominal pain: Diagnosis and management

Fever, infectious disease, and sepsis


  Meningitis: a concise overview of diagnosis and treatment

Peripheral and central venous cannulation technique (Technique of placement of a peripheral venous catheter or a central venous catheter)





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USEFUL LINKS ...

My free cardiology book online: Cardiology: A modern free online cardiology ebook

A useful link for drug information :
medicines.org- emc


LINKS TO MEDICAL CALCULATORS
These are sites that contain easy-to-use medical calculators, to calculate for example body surface area (BSA), body mass index (BMI), estimated glomerular filtration rate (eGFR), CHA₂DS₂-VASc Score for Atrial Fibrillation Stroke Risk,TIMI and GRACE risk scores for acute coronary syndromes Cardiac index and systemic vascular resistance calculators, Calorie calculators/ Drug dosage calculators, etc

MDCalc

Online Medical Calculators-Medicine World org

Medscape-Medical Calculators

ClinCalc.com-calculators for medical professionals


LINKS TO OTHER FREE SOURCES OF MEDICAL INFORMATION  (emergency medicine, internal medicine, and other clinical fields)


Clinical Advisor - Decision Support in Medicine

The Merck Manual - MSD Manual


Snake bites-medical management

 Snake bites

Snakes bite for two reasons: to capture prey or when they feel threatened, for self-defense. Thus, humans are bitten when the snake feels threatened because they have closely approached it, or accidentally stepped on it. The severity of a snake bite varies because there are so many different types of snakes, including both venomous and non-venomous. The severity also varies in cases of the same snake species, depending on the quantity of venom injected and the body size of the victim.

Types of snake bites

There are two types of snake bites:
 Dry bites: These occur when no venom is released from the snake, usually in the case of non-venomous snakes. In some cases, even a venomous snake species may not release venom upon biting. Non-poisonous bites should be cleaned, the patient should receive anti-tetanus prophylaxis if needed and prophylactic antibiotics as for animal bites. If there are no systemic effects or significant local findings the patient can be discharged home with close observation.
Venomous bites: These occur when a snake transmits venom with its bite. They are much more dangerous than dry bites. The patient should be admitted to the hospital.
Bites from venomous snakes can result in paralysis, bleeding, long-term disability, or death.
Venomous snakes usually have a triangular-shaped head and elliptical pupils whereas nonvenomous snakes usually have a more rounded head and round pupils.

Groups of venomous snakes and clinical manifestations of snake bites 

There are two major groups of venomous snakes:
Elapids (Elapidae-cobra family): This family includes about 300 venomous species, such as kraits, mambas, coral snakes and sea snakes. Their venom is mainly neurotoxic but it can also cause tissue damage or damage to blood cells.
Elapids have venom with neurotoxic properties, causing a presynaptic neuromuscular blockade which manifests with muscular weakness or paralysis while local tissue damage and pain are often minimal. However, some species also cause local tissue damage with pain and edema. Coagulopathy is also present in some cases. 
 Often local signs at the site of the bite are minimal and elapid venom systemic effects may develop hours after a bite and are not
easily reversed.  Thus,  3-5 vials of IV antivenom should be administered early to patients who have definitely been bitten by such snakes, because it may not be possible to reverse venom effects once they develop.
Frequently the first sign of envenomation is ptosis of the eyelids. Other manifestations include diplopia, slurred speech, dysphagia, headache, nausea, abdominal pain, progressive generalized muscular weakness, fasciculations, and seizures. In the case of weakness or paralysis of the respiratory muscles, death may occur. Thus, the patient should be observed closely for signs of respiratory muscle weakness and hypoventilation. 
Vipers: This family includes more than 200 species of Viperidae snakes, such as pit vipers (like rattlesnakes, cottonmouths, copperheads, and water moccasins) and Old-World vipers (adders, e.g the common European adder, the puff adder, etc.).
Their poison contains substances, such as proteolytic enzymes, peptides, and biological amines. These substances cause damage to soft tissue and muscle, endothelial dysfunction with increased capillary permeability (leak of fluid into the interstitium), and dysfunction of the mechanism of blood coagulation (by impairing platelet adhesion, causing thrombocytopenia and degrading fibrinogen). Symptoms and signs are categorized as local and systemic.
Local symptoms and signs: Pain (often severe), numbness, severe edema (swelling), skin color change, bruising (ecchymosis), bullae, and in some severe cases compartment syndrome. Often one can discern two small holes in the skin. Oozing of blood from the wound suggests envenomation.
Systemic manifestations: Headache, dizziness, nausea and vomiting, abdominal pain, diarrhea, sweating, tachycardia, hypotension, bleeding. Shock may occur due to bleeding and disruption of fluid balance. Bleeding may occur due to venom-induced coagulopathy.
 Dyspnea may occur in severe cases due to ARDS (acute respiratory distress syndrome) and renal failure due to myoglobinuria (resulting from muscle damage) and shock (causing decreased renal perfusion).

 

Viper bite  

https://commons.wikimedia.org/wiki/File:Viper_bite.jpg

  Brandenberger Rosalba, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons


Treatment of snake bites 


General measures


If possible, the type of snake should be identified to determine if a venomous snake is responsible for the bite and the type of venom injected.
Promptly immobilize the bitten limb and calm the patient. The patient should also be immobilized (e.g. transported lying on a stretcher), if possible. These actions reduce the spread of venom inside the body. The patient should be transported quickly to a medical facility. Tourniquets are not recommended, because they can cause limb ischemia, increase local tissue damage, and also because when the tourniquet is released an abrupt spread of a large quantity of venom will rapidly follow. The use of ice, incision, and suction at the bite site is also not recommended.
Assess vital parameters (heart rate, blood pressure, respiratory rate, pulse oximetry, temperature). In an unstable patient with signs of bleeding, shock, paralysis, or respiratory distress resuscitation measures should be promptly initiated. If hypotension or shock is present initiate intravenous fluids, such as Lactated Ringers or Normal Saline. In the case of respiratory paralysis, the patient is treated with endotracheal intubation and mechanical ventilation.
The site of injury should be cleansed with soap and water and debrided. The skin is marked to identify the rate of spread of edema and erythema. Close observation for the development of compartment syndrome is also required.
 Tetanus toxoid should be administered as needed, depending on the patient's immunization status.  Prophylactic broad-spectrum antibiotics are administered. Although some authorities also recommend high-dose hydrocortisone and antihistamine to reduce local inflammation and systemic symptoms, most experts do not recommend this treatment and use it only in case of an allergic reaction.

Antivenom

Intravenous antivenom is recommended in patients with systemic symptoms or abnormal laboratory tests, or rapid swelling, or severe local manifestations.  Antivenom is the only effective treatment of severe local, or systemic manifestations or hematologic complications. The type and dose of antivenom depend on the likely snake species and local guidelines. 
Antivenoms are created by immunizing horses or sheep with the venom of a particular snake. Their blood serum is then processed, as it will contain antibodies capable of neutralizing the effects of the venom. There are monospecific antivenoms for the treatment of bites from a specific type of snake and also polyspecific antivenoms which can be used for the treatment of bites from a number of snakes found in a particular geographic region.
The antivenom is administered intravenously (IV) and the dosage depends on envenomation severity and not on the body weight or age of the patient. The antivenom should be administered according to the instructions in the package insert.
 Antivenom in some cases can cause an allergic reaction that may range from mild urticaria to severe anaphylaxis. With modern antivenoms, acute severe allergic reactions are relatively rare.  If an acute allergic reaction occurs, the infusion is immediately stopped, antihistamines are administered (both histamine-1 and histamine-2 receptor blockers) and epinephrine is also administered in severe anaphylactic reactions.
Serum sickness is uncommon after antivenom treatment. When it occurs, it manifests with fever, rash, and arthralgias. Treatment is with PO prednisone, 1 mg/kg once daily, and the dose is tapered over 2 weeks.


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LINK: Emergency medicine book-Table of contents

 Bibliography 

Ravikar Ralph,et al Managing snakebite. BMJ 2022;376:e057926

http://dx.doi.org/10.1136/bmj-2020-057926

 

Avau B, Borra V, Vandekerckhove P, DeBuck E. The treatment of snake bites in a first aid setting: a systematic review. PLoS Negl Trop Dis 2016;10:e0005079. doi: 10.1371/journal.pntd.0005079 pmid: 27749906


 Snake Venom In http://www.chm.bris.ac.uk/webprojects2003/stoneley/types.htm

 

Bawaskar HS, Bawaskar PS. Snake bite poisoning. J Mahatma Gandhi Inst Med Sci. 2015;20:-14doi: 10.4103/0971-9903.151717

 

Cleveland Clinic Snake bites https://my.clevelandclinic.org/health/diseases/15647-snake-bites


Edema (oedema): Basic principles of differential diagnosis and management

 Edema (oedema)

It is a clinically evident increase in the volume of fluid (usually interstitial fluid, but in some cases, intracellular fluid may also increase) in a part of the body. This is a general definition of edema, while there are many types of edema, e.g. peripheral edema, unilateral edema of an extremity or a part of an extremity, generalized edema (anasarca), pulmonary edema, and cerebral edema. These different types of edema have different clinical manifestations, depending on the body part or the organ affected and on the underlying cause.
The history should include the time of onset (acute edema if it is present <72 hours), any other symptoms (e.g. pain, dyspnea, etc), systemic disease and important risk factors for systemic disease (e.g. history of heart failure, renal disease or hepatic disease, hypertension, diabetes, alcoholism, thyroid disease), medications, risk factors for deep venous thrombosis (e.g. recent surgery, trauma, prolonged immobilization, cancer), any history of allergy. The physical examination should assess for any signs of systemic disease (e.g. signs of heart disease, hepatic disease, or thyroid disease), as well as for the characteristic features of the edema such as its location and severity, if it is unilateral or bilateral, if it is pitting or non-pitting, skin temperature, skin color, etc.
Pitting is characteristically present in some, but not all, types of edema. Pitting refers to an indentation that remains in the edematous area after pressure is applied. Pitting occurs when the edematous fluid in the interstitial space has a low concentration of protein. This is the case in edema associated with decreased plasma oncotic pressure (e.g. in nephrotic syndrome, cirrhosis) or with increased capillary hydrostatic pressure (e.g. in congestive heart failure, deep venous thrombosis). Non-pitting edema is observed in lymphedema (except from the early phase which may manifest pitting edema), allergic edema or angioedema, and myxedema.


Pitting edema in congestive heart failure
Pitting edema in a patient with congestive heart failure


 
Pathophysiology and etiology of edema
Water constitutes over 50% of the body weight, usually on average about 50-65 % of the body weight. (This percentage is less when there is an increase in body fat, because fat tissue contains less water). The intracellular fluid contains approximately two-thirds of total body water, while the remaining one-third constitutes the extracellular fluid. The plasma (intravascular fluid) contains ¼ of the extracellular fluid.
The remainder ¾ of the extracellular fluid comprise the interstitial fluid. This is the fluid that surrounds cells providing them with oxygen and nutrients and receiving their waste products. Edema represents an excess of interstitial fluid that has become clinically evident.
Edema occurs as a result of:
Increased movement of water from the intravascular to the interstitial space or
Decreased movement of water from the interstitial space into the venous end of the capillaries or into the lymphatic vessels.
The mechanisms responsible for the above alterations in the movement of water may involve one or more of the following:
Increased capillary hydrostatic pressure
This can be due to increased plasma volume (e.g. in renal failure, heart failure, intravenous fluid overload, some drugs such as NSAIDS, pioglitazone, or corticosteroids), or increased venous pressure.  Venous pressure can be increased locally due to a local disorder in venous flow such as deep venous thrombosis, or chronic venous insufficiency or increased systemic venous pressure can be present, due to heart failure of both ventricles or right-sided heart failure. In heart failure, the reduced ability of the heart to achieve adequate forward flow of blood importantly leads to congestion of the venous circulation resulting in an elevated hydrostatic pressure in the venous capillaries.
 In left sided heart failure the pulmonary venous pressure increases and this leads to an elevated pulmonary capillary pressure. This in severe cases leads to pulmonary edema.
Decreased plasma oncotic pressure
This occurs when the amount of plasma proteins diminishes, as in nephrotic syndrome, liver failure (cirrhosis), protein-losing enteropathy, or malnutrition.
Increased capillary permeability
This is caused by local inflammation due to an infection (e.g. cellulitis) or an allergic or immune reaction (anaphylaxis, angioedema). Inflammatory mediators (substances released from cells of the immune system) cause an increase in capillary permeability and leakage of protein and water into the interstitium. Increased amount of protein in the interstitial fluid leads to an increased oncotic pressure in this area, attracting water.
Obstruction of the lymphatic system
Impaired lymphatic drainage causes edema because a portion of the interstitial fluid normally returns to the systemic venous circulation via the lymphatic system. This function of the lymphatic system can be impaired in situations such as hereditary malfunction of the lymphatic system (hereditary lymphedema), chronic inflammation leading to lymph node destruction, a malignancy obstructing lymph drainage, or surgical removal of lymph nodes (e.g. excision of axillary lymph nodes in patients with breast cancer).
● Increased oncotic pressure in the interstitial space
This occurs when there is increased capillary permeability leading to leakage of protein in the extravascular space.

Etiology of edema
Edema can be unilateral or bilateral. The most common cause of unilateral or bilateral leg edema is chronic venous insufficiency.
Unilateral edema of the leg is the result of local mechanical or inflammatory processes. These include:
Venous insufficiency (the most common cause)
 Venous insufficiency causes chronic edema unilateral or bilateral. it is more common in women. Edema lessens after recumbency, whereas it worsens as the day progresses. The edema can be pitting or non-pitting and brownish discoloration of the skin particularly along the medial malleolus is often present, due to hemosiderin deposition. 
Generally, pitting is less than that observed in the edema of heart failure or nephrotic syndrome. Varicose veins are commonly present. Chronic venous insufficiency may also be accompanied by skin erosions or skin ulcers around the medial malleolus.
Thrombophlebitis-Deep venous thrombosis (DVT)
  In thrombophlebitis, there is usually sudden onset of unilateral edema with pain, tenderness, and redness of the affected extremity, which is also warmer than the contralateral extremity. Occasionally in thrombophlebitis pain may be absent. Thus, the absence of pain does not eliminate this diagnosis. Generally in deep venous thrombosis (DVT), edema develops over hours to a few days and it is often accompanied by an increased temperature of the leg and enlarged superficial veins. However, in some cases, symptoms may be minimal and clinical findings are not typical.  A history of a predisposing condition is common, such as recent immobilization, recent surgery, extremity injury, and cancer.  DVT can be complicated by pulmonary embolism (a serious and often life-threatening complication, usually presenting with dyspnea of sudden onset).
Treatment involves therapeutic doses of anticoagulants (usually LMWH or a DOAC) for 3-6 months.
 Lymphedema
Lymphedema results from obstruction of lymphatic drainage leading to an abnormal collection of protein-rich fluid in the interstitium, with subsequent retention of water and swelling of the soft tissue. This protein-rich interstitial fluid stimulates the proliferation of fibroblasts, organization of the fluid, and the development of non-pitting edema. Lymphedema may involve the whole extremity, but it characteristically involves the distal part of the foot, where it begins and the dorsum of the foot, which has the appearance of a hump. The edema is non-pitting (but pitting edema can be present at an early stage of lymphedema).  Another feature of lymphedema is the Kaposi-Stemmer sign: the inability to pinch with your fingers a fold of skin on the dorsum of the foot at the base of the second toe.  Chronic lymphedema is also characterized by thickening of the overlying skin, which may develop a “cobblestone” appearance. Treatment of lymphedema includes elevating the affected limb, complex physical therapy (this is a first-line treatment) and compression stockings, weight loss if the patient is overweight, avoidance of constrictive clothing, and maintenance of appropriate hygiene and skin care.
Cellulitis
 Cellulitis is an infection of the deep dermis and subcutaneous tissues. The most common causative organisms are Streptococcus and Staphylococcus aureus. Erysipelas is a type of cellulitis caused by group A beta-hemolytic streptococci. In cellulitis there is redness, pain and locally increased temperature of the extremity. Erythema, tenderness of the skin, and skin warmth is usually localized to a well-demarcated area of the extremity. In some cases an obvious source of entry of infection, e.g. leg ulcer or insect bite, maybe present. Lymphangitic spread (red lines streaking away from the area of infection) can be present. Depending on the severity of the infection the patient may be febrile and systemically unwell. Treatment is with antibiotics. Mild cases are usually treated with PO antibiotics such as dicloxacillin, amoxicillin-clavulanate, or cephalexin. If the patient is allergic to penicillin clindamycin or a macrolide (clarithromycin or azithromycin) can be used instead. Severe cases are treated with parenteral antibiotics.
Compartment syndrome,
Leg swelling and intense pain associated with altered sensation distally (paresthesia) or paresis, usually in the context of lower limb injury. There is pain out of proportion for a given injury or worsening pain. The edema is tense and firm and the pain is exacerbated by passive extension of the limb (passive muscle stretching). Compartment syndrome is a condition resulting from elevated pressure within a confined myofascial compartment leading to decreased perfusion and hypoxia of the tissues. Acute compartment syndrome is a surgical emergency, since potential necrosis of the involved tissues may develop without prompt diagnosis and intervention. Compartment syndrome results from conditions that increase the volume of a myofascial compartment such as bleeding due to a fracture, tissue edema due to an injury or due to ischemia-reperfusion (after surgical removal of a thrombus, e.g. with a Fogarty catheter) or prolonged external pressure to a myofascial compartment. The latter refers to tight external dressings (e.g., fracture casts), or external pressure, that may occur in sedated or comatose patients who lie on an extremity for a prolonged period.
A ruptured gastrocnemius muscle
A ruptured gastrocnemius muscle is a condition that may occur in athletes (runners). It causes calf edema and midcalf pain of sudden onset. An ecchymosis at the ankle is often present.
A ruptured Baker’s cyst
A Baker's cyst is an enlarged bursa resulting from an accumulation of synovial fluid in the popliteal fossa. Most Baker cysts are small and asymptomatic. When they become large (> 5 cm), the patient will notice a swelling behind the knee and also a decreased range of motion. Baker cysts are usually caused by arthritis, injury, or overuse of the knee, conditions that may result in the increased production of synovial fluid. When a baker cyst ruptures, it manifests with calf swelling, redness, and warmth, (simulating deep vein thrombosis).
An acquired or inherited arteriovenous fistula (rare).
 
Bilateral leg edema or generalized edema is often due to systemic conditions, including
Heart failure
It can cause bilateral non-tender pitting edema in dependent areas of the body. Other clinical features often present in heart failure include dyspnea (on exertion or paroxysmal nocturnal dyspnea with orthopnea), fatigue, and physical examination findings of elevated jugular venous pressure, gallop rhythm on heart auscultation or basilar crackles on lung auscultation, Tests that can aid in the diagnosis are echocardiography and an elevated BNP.
Pulmonary hypertension
Leg edema may appear at an early stage of pulmonary hypertension. Physical examination may reveal a loud pulmonic component of the second heart sound (loud P2) and signs of elevated jugular venous pressure.
Kidney disease such as nephrotic syndrome, acute glomerulonephritis, renal failure
Kidney disease causes soft pitting edema, which is generalized and often involves not only dependent areas of the body but also the face and especially the eyelids. The nephrotic syndrome is characterized by marked proteinuria ( > 3.5 g/day), low plasma albumin, and elevated plasma cholesterol. Renal disease can also cause edema without hypoproteinemia, due to an increased plasma volume (salt and water retention). In renal failure blood urea nitrogen ( BUN) and creatinine are elevated. Urinalysis is a useful test since it may reveal signs of kidney disease, such as protein and blood in the urine (microscopic hematuria).
Hepatic cirrhosis
There is usually a history of alcoholism or hepatitis. Malaise and anorexia are common in a liver disorder or in renal failure, however they are nonspecific symptoms ( also common in advanced cancer, advanced heart failure, a systemic infection, etc.) Findings suggestive of hepatic disease include palmar erythema, easy bruising, jaundice, spider angiomata, hepatomegaly, and ascites.   
Hypoalbuminemia
This may result from nephrotic syndrome cirrhosis, malnutrition, and protein-losing enteropathy. In contrast to cardiac edema, hypoproteinemic edema is less dependent on body position. The face, and particularly the eyelids are often affected, although edema is often present in the lower extremities too. Like cardiac edema, also this form of edema is soft and pitting. The diagnosis of hypoalbuminemia is made by finding low levels of plasma albumin (normal levels 3.5-5.4 g/dl). Hypoproteinemic edema occurs if the plasma albumin content is below 2.5 g/dL  or total plasma protein level is less than 5 g/dL.
Very low levels of  albumin, below 2 g/dL (20g/L) are also accompanied by a predisposition to thrombosis because the plasma
level of antithrombin III also decreases.
Drugs
Drugs can cause edema either by vasodilation or by salt and fluid retention. Drugs that may cause edema are some antihypertensives (calcium channel blockers, hydralazine, minoxidil, methyldopa), NSAIDS (non-steroidal anti-inflammatory drugs), hormones (estrogens, progesterone, oral contraceptives, corticosteroids, androgens), pioglitazone (hypoglycemic drug), trazodone (antidepressant), neurotrophic agents (gabapentin, pregabalin, these may cause edema of hands and feet), chemotherapeutics (cyclosporine, cyclophosphamide, mitramycin)
Allergic reaction or angioedema
These conditions cause acute edema due to increased capillary permeability. Edema often affects the face. If it involves the larynx, it can cause a form of upper airway obstruction with stridor and dyspnea (a dangerous condition requiring immediate treatment, also see the chapter on upper respiratory obstruction).
Sleep apnea
It has been associated with pedal edema because it causes pulmonary hypertension and hence increased venous pressure and capillary hydrostatic pressure
Exposure to extremes of temperature
 
Bilateral leg edema may also result from local causes, such as:
Chronic venous insufficiency
Its clinical features have been described above. Edema caused by venous insufficiency improves with recumbence (i.e. edema is less early in the morning after sleep) and with elevation of the legs and worsens with dependency (it is often worse at the end of the day, after sitting or standing).
Constricting garments,
This may play a role, especially in a person who has recently gained weight.
Prolonged dependency of the legs.
Primary lymphedema
It may present in neonates, adolescents, or young adults and is the result of a genetic malfunction of the lymphatic system.
Idiopathic edema,
Lipedema
Lipedema, although it appears as a form of swelling (increased circumference) of the lower extremities is not true edema. It is more accurately considered a form of fat maldistribution. In lipedema,  the edema 
is symmetric, observed in the hips and both legs due to abnormal fat distribution, but not in the ankles and feetA useful feature for the differential diagnosis between lipedema and lymphedema is that the dorsum of the foot is not affected in lipedema but is prominently involved in lymphedema.

Treatment of edema

Treatment depends on the cause. In case of edema due to fluid overload resulting from a cardiac, renal, or hepatic disease, treatment includes dietary sodium restriction, loop diuretics (furosemide, or torasemide), and in some cases also aldosterone antagonists (mineralocorticoid receptor antagonists, such as spironolactone or eplerenone). Renal function and serum electrolytes should be periodically assessed because both the treatment and the underlying disease may induce significant changes in these laboratory values. Further treatment is dictated by the causative disease.

 
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BIBLIOGRAPHY 

Hoffmann U, Tató F In: Generalized and localized edema. In : Siegenthaler W (ed) Differential diagnosis in internal medicine. From Symptom to diagnosis. Stuttgart, Thieme ; 2007.

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Trayes KP, Studdiford JS, et al. Edema: diagnosis and management. Am Fam Physician. 2013 Jul 15;88(2):102-10.

Link https://www.aafp.org/pubs/afp/issues/2013/0715/p102.html

 

Ely JW, Osheroff JA, Chambliss ML, et al. Approach to leg edema of unclear etiology. J Am Board Fam Med. 2006 Mar-Apr;19(2):148

Link https://www.jabfm.org/content/19/2/148.long

 

Blumberg G, Long B, Koyfman A. Clinical Mimics: An Emergency Medicine-Focused Review of Cellulitis Mimics. J Emerg Med. 2017 Oct;53(4):475-484

Upper airway obstruction

 Upper airway obstruction

Upper airway obstruction is defined as occlusion or narrowing of the upper airways leading to compromise in ventilation. Airway obstruction that is initially partial, may worsen and develop into a life-threatening emergency, which can be fatal without appropriate treatment.
The upper airway is defined as the airway segment above the main carina (i.e. above the lower end of the trachea). The upper airway consists of the following compartments:

the nose (functional during nasopharyngeal breathing)

the mouth (which functions as an airway during oropharyngeal breathing)

the pharynx

the larynx

the trachea.











CC BY 3.0 File:Blausen 0872 UpperRespiratorySystem.png. Blausen.com staff (2014). "Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. - Own work


The mouth and nose are rarely the site of upper airway obstruction, because of their parallel anatomic arrangement, except in cases of massive facial trauma. 

Acute upper airway obstruction can result from aspiration of a foreign body, viral or bacterial infections (retropharyngeal abscess, epiglottitis, croup, bacterial tracheitis), anaphylaxis, angioedema, trauma to the larynx, burns to the face or neck, inhalation injury (smoke, chlorine).  Acute upper airway obstruction is a medical emergency that requires prompt intervention. Reactions to allergens (e.g., bee stings, peanuts, sea-food, medications), infections (epiglottitis), or inhaled irritant particles and gases (smoke inhalation) may cause acute edema of the pharynx and larynx. In addition, a common cause of acute upper airway obstruction is a foreign body lodged in the airway.

Obstruction of the upper airway may occur acutely, resulting in respiratory distress of sudden onset which can lead to death within minutes, in case of complete obstruction, or it may develop chronically, causing progressive dyspnea and exercise intolerance. The sudden onset of respiratory distress and stridor should generally suggest an acute upper airway obstruction. Chronic obstruction, during its course, may also lead to acute respiratory distress when a critical narrowing of the airway develops. This can occur through the progression of the primary cause of the obstruction or as a result of mucus plugging or bleeding.

 

Clinical manifestations of upper airway obstruction

Symptoms and signs, depending on the location and the severity of the obstruction, usually include cough, hoarse voice or muffled voice, dyspnea (the patient often is unable to finish sentences), tachypnea, stridor, agitation or confusion, and tachycardia. In severe cases, without prompt treatment, the clinical picture, due to fatigue of the respiratory muscles and hypoxia, may progress to bradycardia, bradypnea, and cardiac arrest.

Stridor is an important clinical finding which suggests upper airway obstruction. It is a high-pitched musical sound which usually occurs during inspiration, it is heard loudest in the neck and sometimes it can be confused with wheezing. If the site of the obstruction is below the thoracic inlet, both inspiratory and expiratory stridor may be present.

On the contrary, wheezing, occurs predominantly during expiration, becoming louder at end-expiration. Wheezing is a sign of diffuse lower airway narrowing, usually as a result of asthma or COPD.

The voice may be a clue to the site of upper airway obstruction. Hoarseness may be a sign of a laryngeal abnormality in the glottis (the part of the larynx consisting of the vocal cords and the opening between them). Muffling of the voice without hoarseness may suggest a supra-glottic process (an obstruction above the glottis).

In cases of mild upper airway obstruction, the manifestations include cough and hoarse voice but no respiratory distress.

Upper airway obstruction of moderate severity manifests with moderate respiratory distress (moderate tachypnea, mild intercostal and subcostal retractions), agitation, and stridor.

Clinical features of severe upper airway obstruction include severe respiratory distress (severe tachypnea, severe intercostal and subcostal retractions, and nasal flaring), stridor, cyanosis, or SpO2 < 90%, tachycardia, and agitation or lethargy. Cardiac arrest may follow in the most severe cases.

 

Treatment of upper airway obstruction

Examine the patients in the position in which they are the most comfortable.

Evaluate the severity of the obstruction according to the clinical features described above and monitor SpO2, heart and respiratory rate, and the patient’s mental status. In cases with a severe obstruction seek immediate help from a clinician experienced in airway management (an anesthesiologist or otolaryngologist or both).

Administer oxygen continuously: if respiratory distress is present, or if the SpO2 < 94% to maintain the SpO2 between 94 and 98%. If a pulse oximeter is not available administer at least 5 liters of oxygen /minute.

Maintain adequate IV hydration.

Secure the airway if needed (by endotracheal intubation, cricothyroidotomy, or tracheotomy) in cases of severe obstruction and recognize and treat the underlying cause. Treatment for the underlying cause may consist of IV antibiotics for bacterial infections such as epiglottitis and bacterial tracheitis, drainage and antibiotics for a retropharyngeal abscess, humidified oxygen, dexamethasone, and nebulized adrenaline for severe croup, epinephrine corticosteroids, and antihistamines for an anaphylactic reaction).

In an unconscious patient with upper airway obstruction, first try to ventilate with a head-tilt or jaw thrust maneuver (the latter if there is a suspicion of a possible neck injury) and the placement of an oral airway. If these measures fail, direct laryngoscopy with the aid of a gum bougie introducer may often permit successful passage of a small diameter endotracheal tube over the bougie introducer through the glottis.

In a patient with severe upper airway obstruction, when endotracheal intubation fails or is not possible, prompt placement of a surgical airway is indicated. This is achieved by emergency tracheostomy or emergency cricothyroidotomy (or cricothyrotomy). Cricothyroidotomy may provide adequate short-term airway control if a tracheostomy cannot be performed immediately.

Percutaneous cricothyroidotomy

A cricothyroidotomy or cricothyrotomy is an emergent procedure performed when there is a need to secure the airway and orotracheal intubation is not possible or has been unsuccessfully attempted. Percutaneous cricothyroidotomy can be performed by physicians without surgical experience more easily than a surgical cricothyroidotomy, in order to establish an airway. The technique is based on the Seldinger technique (similar to the technique used to insert a central venous line). Special kits for percutaneous cricothyroidotomy are available, that contain the necessary equipment (a scalpel, a catheter over a needle, a syringe, a guidewire, and an airway catheter and its dilator).
Clean and drape the patient’s neck. Lubricate the dilator and insert it through the airway catheter. Lubricate the airway catheter and dilator after it has been assembled into a unit. Identify the anatomical landmarks. The cricothyroid membrane is located between the thyroid cartilage superiorly and the cricoid cartilage inferiorly and it can be identified by palpation of these two surrounding cartilages. With a #11 scalpel blade make a stab incision just through the skin over the center of the cricothyroid membrane. Attach a 5 mL syringe containing saline to the catheter-over-the-needle and insert it slowly at a 30° to 45° angle through the skin incision into the center of the cricothyroid membrane, aiming inferiorly (towards the feet). Advance the catheter-over-the-needle while simultaneously aspirating with the syringe. Stop advancing the catheter-over-the-needle when it enters the airway. When the catheter enters the airway you will feel a loss of resistance and you will see air bubbles in the syringe. Then hold the syringe securely and advance the catheter over the needle until the hub of the catheter is at the skin. Hold the catheter hub against the skin of the neck while removing the needle and syringe. Then advance the guidewire through the catheter into the trachea. Hold the guidewire securely and remove the catheter over the guidewire. Do not stop holding the guidewire in order to prevent it from completely entering the patient’s airway. Insert into the trachea the airway catheter with the dilator in it as a unit over the guidewire. The insertion of the airway catheter-dilator unit over the guidewire is performed with a semicircular motion. Perform this insertion gently to prevent causing injury or perforation of the posterior tracheal wall. Advance the airway catheter-dilator unit until the flange reaches the skin of the neck. Hold the airway catheter securely and remove the guidewire and dilator as a unit, keeping the airway catheter in place. Start ventilation of the patient and secure the airway catheter.   
                       
                                                           




Simple percutaneous insertion of an angiocatheter into the cricothyroid membrane

Another technique, that is easy and can be performed fast, especially indicated in children less than10 years of age, is to insert a 12-16 gauge catheter-over-the-needle (angiocatheter) percutaneously into the cricothyroid membrane. Attach a 5 or 10 mL syringe containing 5 mL of sterile saline to the catheter-over-the-needle (angiocatheter). Insert the angiocatheter through the skin into the inferior aspect of the cricothyroid membrane (preferably through the lower left quadrant of the cricothyroid membrane because this region is least likely to contain cricothyroid arteries and veins). The angiocatheter is inserted with an inferior direction (towards the patient’s feet) at a 30° to 45° angle to the skin. Aspirate continuously with the syringe as the angiocatheter is advanced. The catheter is advanced until you feel a loss of resistance and air bubbles are visible in the syringe. These both signify that the angiocatheter has entered the trachea. Hold the needle securely and advance the catheter until its hub is at the skin. Then remove the needle and syringe. Attach again the syringe without the needle to the catheter and aspirate once again to reconfirm that the catheter is within the trachea. Hold the catheter hub firmly at the skin, remove the syringe and attach the oxygen tubing to the catheter. Ventilate the patient and continue until a more secure airway (e.g. a tracheostomy) is established.
Oxygenation and ventilation of the patient can be achieved by several methods. One method is to insert the adapter piece from a #3.0 endotracheal tube to the catheter hub and then connect it directly to a bag-valve device or a ventilator. Another method is to connect the high-flow oxygen tubing directly to the hub of the catheter. This method requires cyclic ventilation for 1-2 seconds followed by exhalation for 4- 5 seconds. 




Treatment of some specific etiologies of acute airway obstruction


Angioedema is nonpitting, nonpruritic swelling of the deep layers of the skin and mucosal tissues occurring in a localized area of the body, preferentially involving the face (lips, the area around the eyes), tongue, larynx, extremities, gastrointestinal tract (with abdominal pain). Angioedema can often accompany allergic reactions. Angioedema is caused by the following mechanisms:

■ an allergic mechanism (mast cells release histamine in response to IgE-mediated hypersensitivity reactions due to severe food allergies or in response to certain drugs such as aspirin, opiates, iodinated contrast agents).

■ activation of the complement system.

accumulation of bradykinin has been implicated as the probable mechanism of angioedema caused by ACE-inhibitors which occurs in 0,1-0,5 % of the patients receiving these drugs, usually shortly after treatment initiation. (In rare cases it may appear later, even years after treatment initiation).

Angioedema can be, acquired, drug-induced, hereditary or idiopathic. Hereditary angioedema is an autosomal dominant disease resulting from inadequate levels or reduced function of the C1 esterase inhibitor. This changes the activation of the complement system.

Angioedema can cause acute airway obstruction due to tissue swelling. Usually, it can be relieved with subcutaneous epinephrine, corticosteroids, and antihistamines, except from the hereditary type, in which these drugs have much less effect. The above treatment (antihistamines, corticosteroids, and epinephrine) is effective for allergic, histamine-mediated angioedema. Epinephrine (adrenaline) is administered if airway obstruction or hypotension is present. 
The dosage of epinephrine in acute angioedema or anaphylaxis is the following: Epinephrine (adrenaline) 1:1,000 solution (i.e. 1mg/ml):  In adults: 0.2 to 0.5 mL (0.2 to 0.5 mg). In children: 0.01 mg / kg. It is administered subcutaneously or intramuscularly, usually into the upper arm. The injection site may be gently massaged to facilitate absorption. Depending on the patient’s response you may repeat this dose 2-3 times at intervals of 10 -15 minutes.
Antihistamines also provide relief of symptoms in anaphylaxis or in allergic angioedema, e.g., diphenhydramine (Benadryl), 1-2 mg / kg in children (maximum 50 mg) or 25-50 mg in adults, intravenously or intramuscularly.

 For hereditary angioedema, there are other more specific treatments (icatibant, C1 esterase inhibitor replacement).

In patients presenting with angioedema, the likelihood of the need for intubation (preferably fiberoptic intubation) or tracheostomy is increased if the tongue, or larynx is involved and if stridor or drooling occurs.

Aspiration of a foreign body

Upper airway obstruction due to a foreign body aspiration may occur in a child 6 months-5 years playing with a small object or eating. Foreign body aspiration can also occur in an adult while eating because of carelessness or under the influence of drugs or alcohol or in a person who has had a stroke, which may impair the ability to swallow.

If the person is coughing do not intervene, only encourage coughing which may expel the foreign body from the respiratory tract. Maneuvers to relieve obstruction should be performed promptly only if the patient cannot speak or cough.

For children over 1 year and adults:

The Heimlich maneuver is performed to relieve obstruction with the rescuer standing behind the patient. Place a closed fist on the epigastrium (above the navel and below the ribs). Place the other hand over the fist and press hard into the epigastrium with a quick, upward thrust (1-5 times). This maneuver is performed with the intention to compress the lungs from below and dislodge the foreign body.

For children <1 year:

Place the infant face down across your forearm (which rests on your leg) supporting the infant’s head with your hand. With the heel of the other hand, perform one to five slaps on the back, between shoulder plates. If unsuccessful, turn the infant on its back. Perform five forceful sternal compressions as in cardiopulmonary resuscitation: Place 2 or 3 fingers in the center of the infant’s chest just below the nipples and press down approximately one-third the depth of the chest (about 3 to 4 cm).

In a patient who is unable to cough, repeat these maneuvers that aim to relieve the obstruction, until the foreign body is expelled and spontaneous breathing (coughing, talking, crying) is resumed. If the patient loses consciousness perform cardiopulmonary resuscitation (give ventilations and chest compressions).

If effective ventilations are not possible, then urgent endotracheal intubation may be performed with a small diameter tube by an experienced physician. If this is also not possible, an emergency tracheostomy or cricothyroidotomy must be performed very promptly to save the patient’s life.

Laryngotracheobronchitis (croup) is a viral inflammation of the respiratory tract affecting children 3 months-3 years old. The most common presenting features include characteristic barking cough and stridor which is inspiratory or biphasic. The child is usually restless, and developing respiratory distress is often accompanied by flaring of ala nasae and development of intercostals recession. Most cases can be sufficiently managed with humidification, corticosteroids, and nebulized adrenaline, whereas intubation is uncommonly required to secure the airway.

Epiglottitis

It is an acute, rapidly progressive bacterial infection of the epiglottis and adjacent structures that can result in complete obstruction of the upper airway. Epiglottis is an important structure at the base of the tongue preventing food from entering the trachea.  Causative organisms include group A Streptococcus (GAS), Streptococcus pneumoniae, Haemophilus parainfluenzae, and Staphylococcus aureus. In children, the cause is Hemophilus influenzae but it has become rare because of the widespread vaccination against this microorganism.

Patients present with severe sore throat, fever, systemic toxicity, and often inspiratory stridor accompanied by respiratory distress with tachypnea and chest wall retractions. Drooling may be present. When there is a clinical suspicion of epiglottitis, avoid direct visualization of the throat in the examination room (i.e., with a tongue blade) because this carries the risk of precipitating complete airway obstruction. The examination should be performed in a controlled environment (e.g., an operating room) with direct fiberoptic laryngoscopy. This may be performed for diagnosis and also for the placement of an endotracheal tube.

Treatment of epiglottitis

●In cases with respiratory distress, airway protection is required (endotracheal intubation or if this is not possible tracheostomy). Such measures for airway protection are needed in about 10-15% of cases. Signs and symptoms associated with a need for intubation include respiratory distress, stridor, inability to swallow, and drooling.

● Medications: 

Administration of dexamethasone should be considered (reduces the edema of the pharynx and the epiglottis and may help to avoid airway obstruction). IV antibiotics for 7-10 days, comprise the main treatment (ampicillin/sulbactam or a second- or third-generation cephalosporin).


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Bibliography


Eskander A, de Almeida JR, Irish JC. Acute Upper Airway Obstruction. N Engl J Med  2019 ;381(20):1940–9.  10.1056/NEJMra1811697


Médecins Sans Frontières. Acute upper airway obstruction In: Clinical guidelines - Diagnosis and treatment manual. LINK https://medicalguidelines.msf.org/viewport/CG/english/acute-upper-airway-obstruction-16685571.html

 

Eric F. Reichman. Reichman’s Emergency Medicine Procedures, third Edition 2019. New York, McGraw-Hill


Gautam G,  Lippmann M. Disorders of the Central Airways and Upper Airway Obstruction In: Pulmonology Advisor, Decicion Support in Medicine. Link https://www.pulmonologyadvisor.com//home/decision-support-in-medicine/pulmonary-medicine/disorders-of-the-central-airways-and-upper-airway-obstruction/

 

Kumar, S. Salib R (2006). Encyclopedia of Respiratory Medicine || Upper airway obstruction. 375–385.

 

Baines PB and Sarginson RE, Upper airway obstruction. Hospital Medicine 2004; 65(2): 108–111.

 

Tang AW. A practical guide to anaphylaxis.Am Fam Physician. 2003 ;68(7):1325-1333. Link https://www.aafp.org/afp/2003/1001/p1325.html


https://www.rch.org.au/clinicalguide/guideline_index/Acute_upper_airway_obstruction/


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