Morphine/lung exam Flashcards
How is CO2 transported in the blood?
-Bicarb (70%)
-Carbaminohaemoglobin (20%)
-Dissolved CO2 (10%)
Describe the erythrocyte chloride shift with the equation
Describes the movement of chloride into red blood cells which occurs when the buffer effects of deoxygenated haemoglobin increase the intracellular bicarbonate concentration, and the bicarbonate is exported from the RBC in exchange for chloride
What is the point in the chloride shift?
-Mitigates change in pH which would otherwise occur in peripheral circulation due to metabolic biproducts (mainly CO2)
-Increases CO2 carrying capacity of venous blood
-Chloride changes the shape of haemoglobin to increase oxygen unloading
What is the mechanism of the chloride shift?
-Chloride moves into erythrocytes, and bicarb moves out, in venous blood
-CO2 diffuses into the red cells
-There it is converted to bicarb by carbonic anhydrase
-Bicarbonate then diffuses out of the cell, and chloride diffuses in
-The reverse takes place in the pulmonary capillaries
Examiner will give you an ABG, interpret?
Low pH, raised pCO2, normal bicarb
Uncompensated respiratory acidosis
What is the cause of the respiratory acidosis?
Morphine overdose, depresses the CNS
Why is there no metabolic compensation?
Renal tubular compensation only occurs over a period of around 48 hours
Why is bicarb normal?
-The initial response is cellular buffering that occurs over minutes to hours. Cellular buffering elevates plasma bicarb only slightly
-The second step is renal compensation that occurs over 3-5 days. With renal compensation, renal excretion of carbonic acid is increased and bicarb reabsorption is increased
What are the types of respiratory failure and what are their causes?
Type 1: ventilation/perfusion (V/Q) ismatch: the volume of air flowing in and out of the lungs is not matched with the flow of blood to the lungs
–>pneumonia
–> bronchitis
–> PE
–> pneumothorax
Type 2: caused by inadequate alveolar ventilation: both O2/CO2 are affected. Defined as the buildup of carbon dioxide levels that has been generated by the body but cannot be eliminated
–> increased airways resistance (COPD, asthma, suffocation)
–> reduced breathing effort (drug effects, brain stem lesion)
–> decrease in the area of the lung available for gas exchange (such as in chronic bronchitis)
–> neuromuscular problems
–> deformation (kyposcoliosis
What are the response mechanisms to hypercarbia?
Elevation in CO2 leads to central acidosis, which stimulates central chemoreceptors and leads to increased respiratory rate in order to blow off extra CO2
How does morphine act?
-By binding to mu receptors on the respiratory centre causing respiratory depression
What are the side effects of naloxone?
-Nausea
-Vomiting
-Sweating
-Tachycardia
-Abdominal cramps
-Pulmonary oedema
-Cardiac arrest
What structures pass through the hilum of the lung?
-Pulmonary artery and vein (most anteiror)
-Right and left main bronchus (most posterior)
-Bronchial artery and vein
-Lymph nodes
-Autonomic nerves
What is the pulmonary ligament?
A pleural fold that connects the mediastinal surface of the lung and the pericardium to allow expansion of hilar vessels with increased cardiac output
VAD anteiror to posterior: vein, artery, duct
