Diseases Of Respiratory System

Diseases of Respiratory system

Cyanosis  Cyanosis

is a blue or bluish-gray discoloration of the skin and mucous membranes caused by increased amounts (> 5 g/dL) of unsaturated hemoglobin in capillary blood

 Generalized

cyanosis is seen in the lips , nail beds, ears and malar regions



Since the oxygen saturation at which cyanosis becomes clinically apparent is a function of hemoglobin concentration, anemia may prevent cyanosis from appearing while polycythemia may lead to cyanosis in the setting of mild hypoxemia



Cyanosis is therefore not a reliable indicator of hypoxemia but should prompt direct measurement of arterial PO2 or of hemoglobin saturation.

Causes of Cyanosis Respiratory system diseases    

Airway obstruction Pneumothorax Pulmonary edema Pumonary embolism

Cardiovascular diseases       

Heart failure Congenital heart diseases Arterial thrombosis and obstruction Deep venous thrombosis Superior vena caval obstruction Shock Raynaud’s phenomenon

Types of Cyanosis Central

Cyanosis

Peripheral

Cyanosis

Central cyanosis  Central

cyanosis is often due to a circulatory or ventilatory problem that leads to poorer blood oxygenation in the lungs or greater oxygen extraction due to slowing down of blood circulation in the skin's blood vessels.

 Acute

cyanosis can be a result of asphyxiation or choking, and is one of the surest signs that respiration is being blocked.

Common causes of central cyanosis           

Abnormal haemoglobin levels Congenital heart disease Heart failure Heart valve disease High altitude Hypothermia Hypoventilation Lung disease Myocardial infarction Polycythaemia Pulmonary embolism

Peripheral cyanosis  Peripheral

cyanosis is the blue tint in fingers or extremities, due to inadequate circulation

 The

blood reaching the extremities is not oxygen rich and when viewed through the skin a combination of factors can lead to the appearance of a blue color

 All

factors contributing to central cyanosis can also cause peripheral symptoms to appear, however peripheral cyanosis can be observed without there being heart or lung failures

 Small

blood vessels may be restricted and can be treated by increasing the normal oxygenation level of the blood.

Common causes of peripheral cyanosis       

All common causes of central cyanosis Arterial obstruction Cold exposure (due to vasoconstriction) Raynaud's phenomenon (vasoconstriction) Reduced cardiac output (e.g. heart failure, hypovolaemia) Vasoconstriction Venous obstruction (e.g. deep vein thrombosis)

Clinical features of Cyanosis Peripheral cyanosis

Central cyanosis   



Right to left shunt Impaired oxygenation due to lung disorder Abnormal hemoglobin e.g.methhemoglobin or sulphemoglobin Becomes prominenet with exertion or warm environment

Cutaneous vasoconstriction due to cold exposure  Reflex response to decreased cardiac output  Does not get prominent with exertion or warm environment 

Fever  The

average normal oral body temperature taken in mid-morning is 36.7 °C (range 36–37.4 °C)

 Fever

is a regulated rise to a new "set point" of body temperature

 The

elevation in temperature results from either increased heat production (eg, shivering) or decreased loss (eg, peripheral vasoconstriction).



Hyperthermia: Hyperthermia can be conceptualized as an increase above the thermoregulatory set-point



Hypothermia: Hypothermia can be conceptualized as a decrease below the thermoregulatory set-point



Fever: “New Normal” because the thermoregulatory set-point has risen. This has caused what was the normal body temperature (in blue) to be considered hypothermic

Fever Pathophysiology Endogenous or exogenous stimuli ( pyrogens) are presented to monocytes and macrophages Synthesis and release of Interleukin-1, TNF-α, Interleukin-6 and IFN-γ Cytokine-receptor interaction in anterior hypothalamus activates phospholipase A Liberates plasma membrane arachidonic acid Prostaglandin E2 produced through cyclo-oxygenase pathway modifies response in Thermoregulatory centre in the brain

Fever Exogenous pyrogens  

 

Found in bacterial cell wall Endotoxin is a lipopolysaccharide and a component of Gram-negative bacterial cell wall provokes fever and septic shock β-hydroxymyristic acid is a fatty acid producing fever Muramyl dipeptide( MDP) also an exogenous pyrogen mostly in Gram-positive bacterial cell wall

Hyperthermia Pathophysiology



Hyperthermia—not mediated by cytokines—occurs when body metabolic heat production or environmental heat load exceeds normal heat loss capacity or when there is impaired heat loss



Heat stroke is an example



Body temperature may rise to levels (> 41.1 °C) capable of producing irreversible protein denaturation and resultant brain damage



No diurnal variation is observed

Clinical Features of Fever 

Onset of fever with chills, shivering and cutaneous vasoconstriction



Tachycardia



Return of temperature to baseline is marked by sweating and flushing



Night sweats common in chronic infections and malignancies, and represent exaggeration of normal diurnal variation with sweat representing decline of fever at night

Patterns of Fever Remittent fever 

Fever pattern in which temperature varies during each 24 hour period, but never reaches normal. Most fevers are remittent and the pattern is not characteristic of any disease

Relapsing fever Bouts of fever occuring every 5-7 days. Spirochetes

Intermittent fever Episodes of fever separated by days of normal temperature. Tertian fever and quartan fever Fever with tertian periodicity in vivax malaria periodicity in falciparum malaria

Fever with tertian

Undulant fever The fever is typically undulant, rising and falling like a wave It is also called brucellosis after its bacterial cause.

Episodic fever Fever lasts for days or longer followed by prolonged periods without fever Familial periodic fever

Pel-Ebstein fever    



Bouts of several days of continuous or remittent fever followed by afebrile remissions lasting and irregular number of days The diagnosis of Pel-Ebstein fever is made by examining a patient's temperature over several weeks It is a high-grade fever that can reach 40-40.5°C (105-106°F) and keeps rising and falling every 7-10 days The fever rises abruptly, stays high for a week and then falls close to normal abruptly again, staying low for a week. Then this rise and fall pattern is repeated again Example: Hodgkins disease

Continuous fever Diurnal variation of 0.5-1.0 °C. Typhoid and acute pneumonia

Significance of Fever 

Fever provides important information about the presence of illness—particularly infections—and about changes in the clinical status of the patient



Fever pattern is of marginal value except for the relapsing fever of malaria, borreliosis, and Hodgkin's disease



Degree of temperature elevation does not necessarily correspond to the severity of the illness (greater in children than in adults, normal temperature or even hypothermia may be observed in older persons, neonates, and in persons receiving certain medications [NSAIDs] or corticosteroids)



High temperature during the first trimester of pregnancy may cause birth defects, such as anencephaly



Fever increases insulin requirements

Differential diagnosis of fever and hyperthermia Fever—common causes    Infections: Bacterial, viral, rickettsial, fungal, parasitic    Autoimmune diseases    Central nervous system disease: Head trauma and mass lesions    Malignant disease: Renal cell carcinoma, primary or metastatic liver cancer, leukemia, and lymphoma

Fever—less common causes    Cardiovascular diseases, including myocardial infarction, thrombophlebitis, and pulmonary embolism    Gastrointestinal diseases, including inflammatory bowel disease, alcoholic hepatitis, and granulomatous hepatitis    Miscellaneous diseases, including drug fever, sarcoidosis, familial Mediterranean fever, tissue injury, hematoma, and factitious fever

Hyperthermia    Peripheral thermoregulatory disorders, including heat stroke, malignant hyperthermia of anesthesia, and malignant neuroleptic syndrome

Treatment 

Most fever is well tolerated.



When the temperature is greater than 40 °C, symptomatic treatment may be required



A reading over 41 °C is likely to be hyperthermia and thus not cytokine mediated, and emergent management is indicated



Measures for Removal of Heat Alcohol sponges, cold sponges, ice bags, ice-water enemas, and ice baths will lower body temperature. More useful in hyperthermia, since patients with cytokinerelated fever will attempt to override these therapies



Antipyretic Drugs Aspirin or acetaminophen, 325–650 mg every 4 hours, is effective in reducing fever. These drugs are best administered continuously rather than as needed, since "prn" dosing results in periodic chills and sweats due to fluctuations in temperature caused by varying levels of drug.

 Antimicrobial

Therapy

Prompt broad-spectrum antimicrobials are indicated for febrile patients who are clinically unstable, even before infection can be documented

These include patients with :  Hemodynamic instability  Neutropenia (neutrophils < 500/mcL)  Asplenic (surgically or secondary to sickle cell disease)  Immunosuppressed (including individuals taking systemic corticosteroids, azathioprine, cyclosporine, or other immunosuppressive medications)  HIV infection