Anaphylaxis

Introduction-Anaphylactic reaction

· IgE -mediated type I hypersensitivity reaction.

· Effects are due to wide spread degranulation of mast cells.

· A dose independent unpredictable adverse drug reaction

 

Mechanism:

Commonly associated with a previous exposure to a similar group of drugs or chemicals. Foreign proteins act as antigens and stimulate production of IgEantibodies. They bind to mast cells and basophils, and with subsequent exposure massive degranulation occurs due to these already formed antibodies reacting with new antigens.

There is a massive release of mediators : Eg – Histamine, leukotrienes, tryptase, protease.

They give rise to bronchoconstriction, vasodilatation and increased capillary permeability. 

Malignant hyperthermia

Introduction.

• Inherited disorder in skeletal muscle cells
• Autosomal dominant
• Variable penetrance
• Incidence:-   1:15 000 – paediatrics         1: 40 000 – adult
• Can be lethal

Aetiology.

• A genetic mutation in Rynodine receptor, an intracellular calcium channel in sarcoplasmic reticulum.
• When triggered, there is an exaggerated release of calcium ions causing hypermetabolism.
• Triggering agents:- Halogenated inhalational anaesthetic agents Suxamethonium
• They can be otherwise healthy individuals.
• More susceptible in :-
• Duchenne muscular dystrophy
• Central core disease
• Osteogenesis imperfecta
• Strabismus surgery
• Repeated anaesthetics
• Positive family history.

Abdominal ultra sound

CHECK LIST ON ABDOMINAL ULTRA SOUND

Liver                    Size, margins, echogenecity, mass lesions, portal veins, hepatic veins

                       
Gall bladder         Size, calculi, sludge, cholecystitis

Bile ducts             Normal or dilated

Pancreas               Size, echogenecity, masses, calcification, duct dilatation

Spleen                  Size, mass lesions

Kidneys                Size, position, echo pattern, calculi, hydronephrosis, mass lesions

Oxygen therapy and Interpretation of blood gases

Oxygen therapy

• Different modes of O₂ therapy

-          nasal prongs

-          face mask

-          venturi mask

-          ET tube/LMA

• Ordinary face mask provides a FiO₂ of about 35%
• Addition of an reservoir bag can increase the FiO₂> 70% 
• Venturi mask can provide a FiO₂ up to about 60%
• Anaesthetic circuit can provide a FiO₂ close to 100%

Ventilation

Initiation of mechanical ventilation 

Objective of this station is to familiarize with clinical assessment of the patient before initiation of mechanical ventilation.

 Clinical parameters include:

• Level of consciousness and patients ability to cooperate
• Use of accessory muscles of respiration
• Restlessness, anxiety, sweating and posture preferred by the patient
• Presence of cyanosis
• Altered chest wall movements
• Pulse rate and rhythm disturbances
• Oxygen saturation
• Assess for effectiveness of cough reflex and phonation
• Examination of lungs

Note: The decision to initiate mechanical ventilation should be made considering multiple parameters and not a single parameter. Especially normal saturation does not mean ventilation is normal. (Misnomer of most of clinicians).