8.3 Cystic Fibrosis Flashcards
A 30-year-old female patient is listed for repair of median nerve and brachial artery on trauma list, and the orthopaedic surgeon informs you that this patient suffers from cystic fibrosis.
What do you know about cystic fibrosis?
Cystic fibrosis is an autosomal recessive genetic disorder
that is characterised by abnormal transport of Na+ and Cl– ions across the
epithelium of various organs causing thick viscous secretion.
It can affect various organs, mainly lungs, pancreas, intestine, and liver.
What is the pathophysiology? How does chloride channel affect mucus?
The basic pathology is mutation in the cystic fibrosis transmembrane
regulator (CFTR) gene located on chromosome 7, which creates a protein
that does not normally fold on the membrane and is easily degraded by cells.
The protein created by this gene is anchored to the outer membrane of cells
in the sweat glands, lungs, pancreas, and all other remaining exocrine glands
in the body and spans this membrane, acting as a channel that connects
the inner part of the cell (cytoplasm) to the surrounding fluid.
This channel is primarily responsible for controlling the movement of halogens from inside
to outside the cell; however, in the sweat ducts, it facilitates the movement
of chloride from the sweat into the cytoplasm.
When the CFTR protein is faulty, chloride and thiocyanate are trapped inside the cells in the airway and outside in the skin. Because chloride is negatively charged, this creates
a difference in the electrical potential inside and outside the cell, causing
cations to cross into the cell.
Sodium is the most common cation in the extracellular space, and the combination of sodium and chloride creates the salt, which is lost in high amounts in the sweat of individuals with CF.
This lost salt forms the basis for the sweat test.
What are the effects of cystic fibrosis on different organs?
Resp
Cystic fibrosis causes blockage of narrow passage of the affected organ with
thick secretions.
Respiratory system
* Presence of abnormal CFTR protein causes imbalance in Na absorption
and inability to secret Cl− ion, resulting in inadequate fluid secretion and
dehydration of airways.
- Dehydration of mucus and periciliary liquid layers produces adhesion of
mucous to the airway surface, which leads to the failure to clear mucus.
These retained secretions of mucus lead to chronic infections, which later
result in bronchiectasis. - Eventually it leads to cor pulmonale, heart failure, and death.
What are the effects of cystic fibrosis on different organs?
GIT
- Pancreas: Failure of secretion of sodium bicarbonate and water leads to
retention of enzymes in the pancreas and destruction of pancreatic tissue
and fibrosis of pancreatic tissue. - Intestine: Because of the lack of secretion of Cl– and water, the CF
intestinal epithelium fails to flush secreted mucus from intestinal crypts,
leading to dehydrated intraluminal contents and obstruction. Intestinal
fluid contains less water and bicarbonate, which manifests as increased
faecal fat excretion and steatorrhoea. - Liver and gall bladder: Thickened biliary secretions, focal biliary cirrhosis,
cholecystitis, and cholelithiasis.
Sweat glands
Reproductive system
Sweat glands
- Cystic fibrosis patients secrete nearly normal volumes of sweat in the
sweat acinus but are not able to absorb NaCl from sweat ducts, resulting
in higher concentration of salt in sweat.
Reproductive system
* Men: Infertility due to azoospermia and obliteration of vas deferens
* Women: Thick, tenacious cervical mucus blocks sperm migration
How is cystic fibrosis diagnosed?
Diagnosis is mainly based on a combination of clinical criteria and abnormal
CFTR function as documented by sweat tests. Chloride concentration
> 70 mEq/L differentiates between CF and other conditions.
Genetic testing for abnormal gene and protein is also definite diagnostic method.
How will you optimise this patient?
This is a trauma patient suffering from a neuro-vascular injury that requires
urgent treatment, failure of which can lead to permanent damage.
Although there is limited time for optimisation, the following measures may be
undertaken:
- IV fluids, history, and long-term treatment review plus routine anaesthetic
history, examination, and basic investigations including chest X-ray to rule
out any active chest infection. - Full blood count, urea and electrolytes, liver function test, clotting
screening, and blood glucose level. - Baseline arterial blood gas measurement and spirometry will guide the
perioperative care. - Make sure that the patient is adequately hydrated, bronchodilator
treatment may be administered, mucolytic inhalation and preoperative
chest physiotherapy help to minimise postoperative chest infections. - Preoperative sputum culture will also be helpful for choosing appropriate
antibiotics in postoperative period. - Start insulin infusion if indicated to maintain blood glucose within normal
limits
What are the anaesthetic options for this patient?
As the respiratory system is involved in all cystic fibrosis patients, regional
anaesthesia is more preferable whenever possible.
This patient will benefit from regional anaesthesia in the form of interscalene
block, but all disability or motor and sensory loss due to median nerve
damage must be documented prior to theatres..
Follow usual guidelines for any regional anaesthesia such as gaining
consent, ruling out any contraindications, using resuscitation facilities, trained
assistants, monitoring, and full asepsis technique.
The interscalene block should be performed under ultrasound guidance
as this will prevent complications such as pneumothorax, which can be
detrimental in this patient.
IF GA Required
If there is any contraindication for regional anaesthesia over general
anaesthesia, consider the following points:
- Endotracheal intubation will give a better control of airway and will provide
access for tracheal suctioning intraoperatively, which will improve gas exchange. - Use short-acting drugs.
- Inhalation agents with bronchodilator properties such as sevoflurane are preferable.
- Humidified gases and warm IV fluids.
- Postoperative pain relief and HDU monitoring if necessary.
- Bronchodilators, mucolytic agents, and regular physiotherapy in
postoperative period is absolutely essential to prevent any chest infection.
