NEET MDS Lessons
General Surgery
SHOCK
Shock is defined as a pathological state causing inadequate oxygen delivery to the peripheral tissues and resulting in lactic acidosis, cellular hypoxia and disruption of normal metabolic condition.
CLASSIFICATION
Shock is generally classified into three major categories:
1. Hypovolemic shock
2. Cardiogenic shock
3. Distributive shock
Distributive shock is further subdivided into three subgroups:
a. Septic shock
b. Neurogenic shock
c. Anaphylactic shock
Hypovolemic shock is present when marked reduction in oxygen delivery results from diminished cardiac output secondary to inadequate vascular volume. In general, it results from loss of fluid from circulation, either directly or indirectly.
e.g. ? Hemorrhage
• Loss of plasma due to burns
• Loss of water and electrolytes in diarrhea
• Third space loss (Internal fluid shift into inflammatory exudates in
the peritoneum, such as in pancreatitis.)
Cardiogenic shock is present when there is severe reduction in oxygen delivery secondary to impaired cardiac function. Usually it is due to myocardial infarction or pericardial tamponade.
Septic Shock (vasogenic shock) develops as a result of the systemic effect of infection. It is the result of a septicemia with endotoxin and exotoxin release by gram-negative and gram-positive bacteria. Despite normal or increased cardiac output and oxygen delivery, cellular oxygen consumption is less than normal due to impaired extraction as a result of impaired metabolism.
Neurogenic shock results primarily from the disruption of the sympathetic nervous system which may be due to pain or loss of sympathetic tone, as in spinal cord injuries.
PATHO PHYSIOLOGY OF SHOCK
Shock stimulates a physiologic response. This circulatory response to hypotension is to conserve perfusion to the vital organs (heart and brain) at the expense of other tissues. Progressive vasoconstriction of skin, splanchnic and renal vessels leads to renal cortical necrosis and acute renal failure. If not corrected in time, shock leads to organ failure and sets up a vicious circle with hypoxia and acidosis.
CLINICAL FEATURES
The clinical presentation varies according to the cause. But in general patients with hypotension and reduced tissue perfusion presents with:
• Tachycardia
• Feeble pulse
• Narrow pulse pressure
• Cold extremities (except septic shock)
• Sweating, anxiety
• Breathlessness / Hyperventilation
• Confusion leading to unconscious state
PATHO PHYSIOLOGY OF SHOCK
Shock stimulates a physiologic response. This circulatory response to hypotension is to conserve perfusion to the vital organs (heart and brain) at the expense of other tissues. Progressive vasoconstriction of skin, splanchnic and renal vessels leads to renal cortical necrosis and acute renal failure. If not corrected in time, shock leads to organ failure and sets up a vicious circle with hypoxia and acidosis.
CLINICAL FEATURES
The clinical presentation varies according to the cause. But in general patients with hypotension and reduced tissue perfusion presents with:
• Tachycardia
• Feeble pulse
• Narrow pulse pressure
• Cold extremities (except septic shock)
• Sweating, anxiety
• Breathlessness / Hyperventilation
• Confusion leading to unconscious state
Cricothyroidotomy
Cricothyroidotomy is a surgical procedure that involves making an incision through the skin over the cricothyroid membrane, which is located between the thyroid and cricoid cartilages in the neck. This procedure is performed to establish an emergency airway in situations where intubation is not possible or has failed, such as in cases of severe airway obstruction, facial trauma, or anaphylaxis.
Indications
Cricothyroidotomy is indicated in the following situations:
- Acute Airway Obstruction: When there is a complete blockage of the upper airway due to swelling, foreign body, or trauma.
- Failed Intubation: When attempts to secure an airway via endotracheal intubation have been unsuccessful.
- Facial or Neck Trauma: In cases where traditional airway management is compromised due to injury.
- Severe Anaphylaxis: When rapid airway access is needed and other methods are not feasible.
Anatomy
- Cricothyroid Membrane: The membrane lies between the thyroid and cricoid cartilages and is a key landmark for the procedure.
- Surrounding Structures: Important structures in the vicinity include the carotid arteries, jugular veins, and the recurrent laryngeal nerve, which must be avoided during the procedure.
Procedure
Preparation
- Positioning: The patient should be in a supine position with the neck extended to improve access to the cricothyroid membrane.
- Sterilization: The area should be cleaned and sterilized to reduce the risk of infection.
- Anesthesia: Local anesthesia may be administered, but in emergency situations, this step may be skipped.
Steps
- Identify the Cricothyroid Membrane: Palpate the thyroid and cricoid cartilages to locate the membrane, which is typically located about 1-2 cm below the thyroid notch.
- Make the Incision: Using a scalpel, make a vertical incision through the skin over the cricothyroid membrane, approximately 2-3 cm in length.
- Incise the Membrane: Carefully incise the cricothyroid membrane horizontally to create an opening into the airway.
- Insert the Airway Device:
- A tracheostomy tube or a large-bore cannula (e.g., a 14-gauge catheter) is inserted into the opening to establish an airway.
- Ensure that the device is positioned correctly to allow for ventilation.
- Secure the Airway: If using a tracheostomy tube, secure it in place to prevent dislodgment.
Post-Procedure Care
- Ventilation: Connect the airway device to a bag-valve-mask (BVM) or ventilator to provide oxygenation and ventilation.
- Monitoring: Continuously monitor the patient for signs of respiratory distress, oxygen saturation, and overall stability.
- Consider Further Intervention: Plan for definitive airway management, such as a formal tracheostomy or endotracheal intubation, once the immediate crisis is resolved.
Complications
While cricothyroidotomy is a life-saving procedure, it can be associated with several complications, including:
- Infection: Risk of infection at the incision site.
- Hemorrhage: Potential bleeding from surrounding vessels.
- Damage to Surrounding Structures: Injury to the recurrent laryngeal nerve, carotid arteries, or jugular veins.
- Subcutaneous Emphysema: Air escaping into the subcutaneous tissue.
- Tracheal Injury: If the incision is not made correctly, there is a risk of damaging the trachea.
Sinus
It is a tubular track lined by granulation tissue and open at one end which is at the surface,
eg. Tuberculous Sinus
Fistula
A tubular track lined by granulation tissue and open at both ends.at least one of which communicates with a hollow viscus. it can be internal or external.
Causes
1. Inadequate drainage
- Abscess bursting at the non dependent part
- Incision at the non-dependent part.
- Narrow outer opening leading to collection of exudates in the cavity.
2. Presence of foreign body like sequestrum or slough.
3. Persistence of infection.
4. When the track is lined by epithelium
5. Specific causes, TB., Syphilis, etc.
6. Marked fibrosis of the wall with obliteration of blood vessels.
7. Poor general condition causing delayed healing.
Treatment
1. control of specific infection,
2. Thorough excision of track to open up the cavity. Removal of foreign body and scraping of the epithelium
3. Through Scrapping of the wall to expose healthy tissue
4. Wound laid open and allowed to heal from the bottom leaving no pocket,