FEVER

Fever

PKGhatak, MD

Merriam Webster dictionary defines fever as the elevation of the body temperature above normal.

The question then - what a normal body temperature.

It may come as a surprise to many that a normal body temperature is not so easily defined or universally accepted. Human body temperature varies - it is highest at sundown, reaches 37.4C (99.3F) then slowly decreases and drops to 35.2C (95.6F) at sunrise. This is known as Diurnal Variation.

CDC (center for disease control, USA) defines normal body temperature 37C (98.6F) and fever 38C (100.4F). In 1868 Carl Wuderlich wanted to answer that question and studied one million fever charts. He concluded that a normal axillary (under the armpit) temperature was 37 (+ -) 0.9C and any temperature over 38C as fever. A similar study conducted by Mackowiak concluded that a normal oral temperature was 99.9F and above that was fever. Small and Clements reviewed over 120,000 ER visit charts and reported a temperature of 1.8F above the diurnal variation was fever.

Causes of fever.

These are several causes of fever and can be mentioned here very briefly under External and Internal causes.

External causes. -

Infection. Viruses, bacteria, fungi, inhalation of fungal spores, parasites.

Inflammation.  Damage to body tissue by sprains, bone fractures, childbirth, surgery, crush injuries,

Snakebite, insect bites, plant poison.

Autoimmune disease/condition.  Rheumatoid arthritis and other collagen vascular diseases. Crohn's disease, ulcerative colitis. Mismatched blood and blood product transfusion, rejection of organ transplants.

Allergy.  Hay fever.

Malignancy.  Lymphoma, sarcoma, acute leukemia.

Food and Drinks.   Uncooked shellfish, unpasteurized milk and milk products, poorly cooked meat and eggs.

Drugs.  Fever from drugs is due to the development of antibodies or direct action of the heat controlling center of the brain. Penicillin tops the list followed by cephalosporins, anti-TB drugs, quinidine, procainamide, methyldopa, phenytoin.

Hear stroke.  Exposure to high ambient temperature and humidity, working in the boiler room, steam engine locomotive. 

Post anesthetic malignant hyperthermia. Certain anesthetic drugs can precipitate uncontrollable high temperatures in people with a rare inherited disorder.

Internal factors from damage to temperature center.

Brain damage from strokes. Methamphetamine intoxication, Traumatic Brain Injury (TBI).

Malignant hyperthermia. When body temperature reaches 109F(43C), the temperature center breaks down and unless medical attention is given immediately death becomes imminent. Examples are Parkinson's hyperpyrexia syndrome, Serotonin syndrome.

FUO (fever of unknown origin).  FUO in the earlier days due to subacute bacterial endocarditis or lymphoma. Now it is highly unlikely that a fever will not have a discernable cause.

Physiology of Fever.

The Temperature Regulating Center (TCR) is located in the Hypothalamus of the brain. Hypothalamus is also the nerve center of the sympathetic nervous system. The TCR is connected with other centers of the brain and via the Hypothalamus - pituitary portal circulation with the Pituitary gland. Through these pathways, the hypothalamus controls the metabolic rate, heat generation and heat dissipation of the body. Regulation of heart rate, breathing, and hormone levels is under the autonomic nervous system.

The setpoint of Temperature.

The hypothalamic auto-regulatory mechanism sets the normal core body temperature.

Pathology of fever.

Chemicals secreted by the phagocytic WBCs, immunocytes are called Cytokines, Interleukins, Prostaglandins. These are the chemical messengers that can turn the TCR up or down. Cytokines and interleukins promote Prostaglandin E2(PGE2) secretion. PGE2 acts directly on TCR.

Some bacterial degradation products can directly act on TCR and cause fever(pyrogenic).

Effect of fever:

Higher body temperature enhances the phagocytic action (ability to engulf) of WBC.

Immunocytic activities increase - production of IL-1(interleukin 1) and IL-6 are promoters of inflammation.

Inhibition of Bacterial growth. Most human pathogenic bacteria grow best at a normal body temperature; fever slows down the bacterial growth rate.

Metabolic reset.  At a higher temperature, glucose utilization, glycogen breakdown and glucose generation from fat and amino acids are accelerated.

Generation of body heat or Thermogenesis is under the control of the hypothalamus:

Shivering is a common method of thermogenesis; the release of adrenaline and thyroxine are other ways.

Loss of heat is achieved through vasodilatation and increased sweat production via the sympathetic nervous system.

 

In the pre-antibiotic era, the study of fever was an important subject in medical school. Paying meticulous attention to the characteristics of the fever chart, a physician could guess the bacteria responsible for the infection.

The fever was categorized as- 

Continuous, remittent (the temperature remained above normal throughout the day but fluctuated more than 2 C in 24 hrs.), intermittent, quotidian (every day), tertian (every 2-day interval), quartan (every 3-day interval).

Typhoid fever was diagnosed on the basis of remittent fever, and a palpable spleen. Other examples of intermittent fever are Malaria, Kala-azar, TB, Rat bite fever, EB virus.

The post antibiotic era changed the enthusiasm for fever study. At present, antigen testing for pathogens includes viruses, bacteria and many fungal and parasitic diseases. Antibody tests are also widely available. Present day clinicians look at the fever cart but rely less on it to make a diagnosis.

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Common Cold

Common cold

PKGhatak, MD

The common cold is really very common. It is said that every adult gets 2 attacks and every child 6 attacks of the common cold every year. The common cold is the number one viral disease of humans.

There are about 200 different viruses responsible for the common cold including three groups of coronaviruses, however, Rhinovirus is responsible for 50 % of the common cold. The common cold is also called Head Cold and Viral URI (viral upper respiratory infection)

Rhinovirus is an RNA virus. It thrives in the nose because the virus prefers 89 degrees F and the nose temperature is very close to it, as opposed to the core body temperature of 98.6 degrees F. It is also true that exposure to cold makes a person susceptible to rhinovirus infection.

Covid-19 pandemic made people aware of viral infections. The mode of the viral spread and symptoms of illness are understood by most people. Public health officials repeatedly advised people how to protect themselves from this respiratory viral infection and to minimize the spread of the virus to others.

People have learned that viruses are inert particles, like darts until the virus gets a foothold in a living individual. The virus then enters inside the cell and directs the cell DNA /RNA to copy virus particles. In the end, the cell walls are broken open and viruses are released, newly released viruses infect more healthy cells. The rhinovirus uses ICAM receptors to attach to the nasal epithelium and then enter inside the cell.

Covid pandemic has produced havoc in the way we live, work, socialize, and carry out other activities. Most of these are detrimental to human society except for one benefit - during the period of social distancing and hand washing the common cold has almost disappeared.

In early human history, the common cold viruses found humans an easy target to attack, infect, multiply and live in perpetuity. The human immune system is unable to maintain a good defense against the common cold viruses. A vaccine, for the same reason, has not been effective. Recently, MedUnite of Vienna found that the human immune system produces antibodies against the RNA genome of rhinovirus but not against the capsid protein which is necessary to kill the rhinovirus. That is responsible for repeated rhinovirus infections.

Children are nursery going age, young adults on college campuses, military recruits, people in cruise ships, sailors in submarines and other ocean-going vessels and institutional residents are prone to repeated common colds.

Infants and young children suffer the most because their airways are narrow and they are not able to cough sputum up. Elderly and disabled nursing home patients develop complications more often than any other group and also die in a higher proportion.

The diagnosis.

Viral URI is diagnosed by eliminating bacterial URI.  The most common bacteria causing URI is GAS (group A streptococcus). The textbook lists certain signs like - a temperature of 104 degrees F or higher, swollen red tonsils, strawberry tongue, petechiae on the hard palate and cervical lymph node enlargement are usually findings in bacterial URI; but physicians depend on the Rapid Strep Test (RST). The RST detects a GAS antigen, taken from the throat by a swab and mixing it with known GAS antibodies; and at times blood WBC count is necessary.

Complications.

A middle ear infection is common in children, and difficulty in breathing may require hospitalization. Elderly people may develop viral pneumonia, and at times viral URI makes them susceptible to bacterial pneumonia.

Prevention.

A molecule, SETD3 (set domain protein 3) has shown promise in blocking rhinovirus replication by interfering with the methyltransferase of rhinovirus.

If you read this article hoping to get answers to one or two questions you wanted to know about the common cold; I hope you got them here.

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Sternutation

 Sternutation

PKGhatak, MD

Sternutation is an unusual way to say sneezing. The Latin root is a verb- Sternuere, meaning to sneeze.  The term, Sternutation, is hardly used in medicine.

Sneezing is a reflex involuntary action of forceful expulsion of a large volume of air through the nose and mouth containing the nasal discharge and mucus containing the nasal irritant.

The sensory pathway of this reflex is the maxillary division of the trigeminal nerve.  The sensory nucleus is situated in the medulla, close to the lateral reticular formation, called the spinal trigeminal nucleus. The neurotransmitter is Histamine. The motor pathways are extensive because a large number of muscle groups are involved. Many of the muscles are also used in coughing. The muscles used in sneezing are the pharyngeal, tongue, laryngeal, diaphragm, bronchial, facial including eyelids, muscles of respiration, accessory muscles of respiration, and anterior abdominal muscles. The motor impulse is carried by the facial, glossopharyngeal, Vagus, phrenic, intercostal, and spinal motor nerves.

The act of sneezing.

Initially, the mouth and nasal passages are widely opened to draw in a large volume of air. Next, the base of the tongue is elevated and the epiglottis is depressed partially closing the oropharynx. Finally, a sudden volant contraction of all muscles forces out air through the nose and mouth containing nasal secretions and mucus. A sneeze generates aerosol particles of 0.5 to 5.0 micro-millimeter sizes of about 40,000 in one sneeze.

A person must be awake to sneeze but cannot voluntarily sneeze or sneeze on demand. 

Special categories of sneezing.

Snatiation. 

Snatiation is a combination of two words - sneeze and satiety. This is a hereditary condition, inherited by autosomal dominant mode. A full stomach brings uncontrollable sneezing.

Photic sneeze.

It is also inherited by autosomal dominant mode, also known as ACOHOO (autosomal dominant compulsive helio ophthalmic outburst of sneezing). People carrying this gene sneeze as soon they step out of dark places to a brightly lighted place,

The usual cause of sneeze.

Nasal irritants: foreign body, irritant gases, household cleaning agents, detergents, perfume, incense burning.

Allergic rhinitis. Vasomotor rhinitis, chronic sinusitis.

Nasal infection: viruses, bacteria, etc.

Nasal polyp.

Injury to nose, CSF leak, Nose bleeds.

Withdrawal of addictive drugs like opioids.

The history of sneezing is nothing to sneeze about. The subject is full of historical facts, religious beliefs and practices, tradition and lots of intrigues.

_______________________________

Please read:   

https://en.wikipedia.org/wiki/Sneeze

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Cough.

 

Cough

PKGhatak, MD

Cough is a protective action, either voluntary or reflex, to clear the airway of secretion.

The pharynx is a Greek word meaning the throat. The throat is a hollow muscular structure, stretches from the base of the skull to the beginning of the larynx in front and the esophagus behind. Epiglottis is a cartilaginous structure guarding the openings of the larynx and esophagus. The upper posterior part of the pharynx is the nasopharynx where nasal passages open. The middle part is the oropharynx, an extension of the oral cavity and the lower part is the laryngeal pharynx.

The sensation from the nasopharynx is carried by the maxillary branch of the trigeminal nerve (cranial nerve 5). The oropharynx is innervated by the sensory division of the glossopharyngeal nerve. The larynx, vocal cords and nasopharynx are innervated by the sensory fibers of the Vagus nerve –the internal division of the superior laryngeal nerve. A sensory branch of the Vagus also supplies a portion of the external auditory canal and Eustachian tube. Branches from these nerves form a tangle of nerves called the Pharyngeal plexus. The trachea and bronchus down to the respiratory bronchioles are innervated by the recurrent laryngeal nerve of the vagus. These nerves carry sensation to the brain. But the cough center in the brain is not a localized center.

The motor impulse to the muscles involved in the cough reflex is supplied by several nerves. The main muscle is the diaphragm: The phrenic nerve innervates the diaphragm. The intrinsic muscles of the Pharynx are supplied by the recurrent laryngeal nerve, and only the stylopharyngeus muscle is innervated by the motor fibers of the glossopharyngeal nerve. The external intercostal muscles, anterior abdominal muscles are innervated by the intercostal nerves of the thoracic segments of the spinal motor nerves of the abdomen.

Mechanism of cough.

The initial action is the closure of the glottis (the vocal cords and the space between them), the epiglottis closes the opening to the larynx. The next act is a forceful contraction of all muscles, resulting in positive pressure in the thoracic cavity. The trachea and bronchus become shorter and narrower. The last act is the sudden relaxation of the vocal cord and throat. That results in a sudden gush of air expelled from the airways carrying all irritants captured in the bronchial secretion.

Though coughing and sneezing are triggered simultaneously with some common noxious stimuli, these two reflexes are different. A person can cough in sleep or under light anesthesia. On the other hand, a person who has to be awake to sneeze at the same time cannot sneeze voluntarily.

The force generated by a reflex cough can reach 100 miles/hr. The voluntary cough can vary greatly from just a short repeated cough commonly called a nervous cough to a forceful cough with the use of all muscles including accessory muscles of inspiration as in cases of bringing up thick tenacious sputum. When a cough brings up blood - is called Hemoptysis.

Factors triggering coughs.

Irritants: Irritation of the pharynx, trachea-bronchus from irritant gas, or fine sprays of chemicals like perfume, incense, household clears, and detergents.

Infectious agents: respiratory viruses, Covid-19, influenza, bacterial, fungal, mycobacteria.

Allergy and asthma.

Sinus and nasal discharge: Postnasal drip and vasomotor rhinitis, allergic rhinitis are some examples.

Medication: ACE inhibitors.

Pulmonary fibrosis: Idiopathic pulmonary fibrosis, post viral pneumonia fibrosis. Rheumatoid arthritis, SLE and scleroderma.

Malignant lesions: larynx, vocal cord and Lung.

Aspiration of gastric acid: gastric reflux and aspiration.

Foreign body in airways.

Anxiety and psychosocial: also called nervous cough.

Putting Q-tip in the ear.

Voluntarily or on request by the examining physician.

Types of Coughs:

Wet cough. In infection and allergy where a lot of nasal secretion is generated.

Dry cough. Commonly seen in the use of ACE inhibitors, Pulmonary fibrosis.

The patients cough repeatedly, short infective cough, involuntarily, and at times disturb sleep.

Paroxysmal cough. The patient coughs uncontrollably and violently followed by a whooping sound in an attempt to resume breathing. Patients soon feel exhausted from coughing as seen in whooping cough(pertussis)

Tickle cough. In vasomotor rhinitis and allergic rhinitis, sudden onset of cough occurs and continues till secretions are completely cleared from the airway.

Nervous cough: repeated attempts to clear throat when there is no secretion.

Croup. This is seen in children under 5 yrs. old in viral infection because of narrow airways. The swelling in and around the larynx produces raspy and squawking sounds.

Persistent cough. When cough persists over 6-8 weeks as often seen in allergy and gastric acid aspiration. In delayed diagnosis like eosinophilic bronchitis, ca lung, TB, fungal infection, etc.

Night cough. It is usually seen in gastric reflux and asthma.

Features of vasomotor rhinitis:

The precise cause is unknown, various agents are suspected including weather, perfumes, alcohol and spicy food. The cough follows a sudden gush of nasal watery discharge. The disincentive signs are the absent itchy nose, watery eyes, or scratchy throat.

Complications of persistent cough:

Most coughs are episodic, related to the upper respiratory tract infection, and are controlled easily. In prolonged vigorous cough, some of the following complications may be seen.

Fainting spells, Subconjunctival hemorrhage, small urine leaks, Inguinal and femoral hernias, Fractured ribs, Sore chest wall and costochondritis. Exhaustion, Sleep deprivation.

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