Talk to us?

General Surgery - NEETMDS- courses
NEET MDS Lessons
General Surgery

Neuromuscular Blockers in Cardiac Anesthesia

In  patient on β-blockers, the choice of neuromuscular blockers (NMBs) is critical due to their potential cardiovascular effects. Here’s a detailed analysis of the implications of using fentanyl and various NMBs, particularly focusing on vecuronium and its effects.

Key Points on Fentanyl and β-Blockers

  • Fentanyl:

    • Fentanyl is an opioid analgesic that can cause bradycardia due to its vagolytic activity. While it has minimal hemodynamic effects, the bradycardia it induces can be problematic, especially in patients already on β-blockers, which reduce heart rate and blood pressure.
  • β-Blockers:

    • These medications reduce heart rate and blood pressure, which can compound the bradycardic effects of fentanyl. Therefore, careful consideration must be given to the choice of additional medications that may further depress cardiac function.

Vecuronium

  • Effects:

    • Vecuronium is a non-depolarizing neuromuscular blocker that has minimal cardiovascular side effects when used alone. However, it can potentiate decreases in heart rate and cardiac index when administered after fentanyl.
    • The absence of positive chronotropic effects (unlike pancuronium) means that vecuronium does not counteract the bradycardia induced by fentanyl, leading to a higher risk of significant bradycardia and hypotension.
  • Vagal Tone:

    • Vecuronium may enhance vagal tone, further predisposing patients to bradycardia. This is particularly concerning in patients on β-blockers, as the combination can lead to compounded cardiac depression.

Comparison with Other Neuromuscular Blockers

  1. Pancuronium:

    • Vagolytic Action: Pancuronium has vagolytic properties that can help attenuate bradycardia and support blood pressure. It is often preferred in cardiac anesthesia for its more favorable hemodynamic profile compared to vecuronium.
    • Tachycardia: While it can induce tachycardia, this effect may be mitigated in patients on β-blockers, which can blunt the tachycardic response.
  2. Atracurium:

    • Histamine Release: Atracurium can release histamine, leading to hemodynamic changes such as increased heart rate and decreased blood pressure. These effects can be minimized by slow administration of small doses.
  3. Rocuronium:

    • Minimal Hemodynamic Effects: Rocuronium is generally associated with a lack of significant cardiovascular side effects, although occasional increases in heart rate have been noted.
  4. Cis-Atracurium:

    • Cardiovascular Stability: Cis-atracurium does not have cardiovascular effects and does not release histamine, making it a safer option in terms of hemodynamic stability.

Advanced Trauma Life Support (ATLS)

Introduction

Trauma is a leading cause of death, particularly in the first four decades of life, and ranks as the third most common cause of death overall. The Advanced Trauma Life Support (ATLS) program was developed to provide a systematic approach to the management of trauma patients, ensuring that life-threatening conditions are identified and treated promptly.

Mechanisms of Injury

In trauma, injuries can be classified based on their mechanisms:

Overt Mechanisms

  1. Penetrating Trauma: Injuries caused by objects that penetrate the skin and underlying tissues.
  2. Blunt Trauma: Injuries resulting from impact without penetration, such as collisions or falls.
  3. Thermal Trauma: Injuries caused by heat, including burns.
  4. Blast Injury: Injuries resulting from explosions, which can cause a combination of blunt and penetrating injuries.

Covert Mechanisms

  1. Blunt Trauma: Often results in internal injuries that may not be immediately apparent.
  2. Penetrating Trauma: Can include knife wounds and other sharp objects.
  3. Penetrating Knife: Specific injuries from stabbing.
  4. Gunshot Injury: Injuries caused by firearms, which can have extensive internal damage.

The track of penetrating injuries can often be identified by the anatomy involved, helping to determine which organs may be injured.

Steps in ATLS

The ATLS protocol consists of a systematic approach to trauma management, divided into two main surveys:

1. Primary Survey

  • Objective: Identify and treat life-threatening conditions.
  • Components:
    • A - Airway: Ensure the airway is patent. In patients with a Glasgow Coma Scale (GCS) of 8 or less, immediate intubation is necessary. Maintain cervical spine stability.
    • B - Breathing: Assess ventilation and oxygenation. Administer high-flow oxygen via a reservoir mask. Identify and treat conditions such as tension pneumothorax, flail chest, massive hemothorax, and open pneumothorax.
    • C - Circulation: Evaluate circulation based on:
      • Conscious level (indicates cerebral perfusion)
      • Skin color
      • Rapid, thready pulse (more reliable than blood pressure)
    • D - Disability: Assess neurological status using the Glasgow Coma Scale (GCS).
    • E - Exposure: Fully expose the patient to assess for injuries on the front and back.

2. Secondary Survey

  • Objective: Conduct a thorough head-to-toe examination to identify all injuries.
  • Components:
    • AMPLE: A mnemonic to gather important patient history:
      • A - Allergy: Any known allergies.
      • M - Medications: Current medications the patient is taking.
      • P - Past Medical History: Relevant medical history.
      • L - Last Meal: When the patient last ate.
      • E - Events of Incident: Details about the mechanism of injury.

Triage

Triage is the process of sorting patients based on the severity of their condition. The term "triage" comes from the French word meaning "to sort." In trauma settings, patients are categorized using a color-coded system:

  • Red: First priority (critical patients, e.g., tension pneumothorax).
  • Yellow: Second priority (urgent cases, e.g., pelvic fracture).
  • Green: Third priority (minor injuries, e.g., simple fracture).
  • Black: Zero priority (patients who are dead or unsalvageable).

Blunt Trauma

  • Common Causes: The most frequent cause of blunt trauma is road traffic accidents.
  • Seat Belt Use: Wearing seat belts significantly reduces mortality rates:
    • Front row occupants: 45% reduction in death rate.
    • Rear seat belt use: 80% reduction in death rate for front seat occupants.
  • Seat Belt Injuries: Marks on the thorax indicate a fourfold increase in thoracic injuries, while abdominal marks indicate a threefold increase in abdominal injuries.

Radiographs in Trauma

Key radiographic views to obtain in trauma cases include:

  1. Lateral cervical spine
  2. Anteroposterior chest
  3. Anteroposterior pelvis

An ulcer is a break in the continuity of the skin or the mucous membrane.

Mode of onset:  Traumatic ulcers heal when the traumatic agent is removed., If it persists it becomes chronic as in the case of dental ulcer of the tongue. Ulcers may develop spontaneously as in the case of gumma (syphilitic ulcer). It may develop with varicose veins called varicose ulcer, which develops in the lower third of the leg.

Sometimes a malignant ulcer develops in a scar called Marjolin’s ulcer. Special features are:

 No pain - as there are no nerves. It does not spread - as there is scar tissue. No metastases - as there are no lymphatics Treatment:- Wide excision.

Classification of Ulcer

A) Pathologically

I. Non-specific ulcers:

a. Due to infected wound after trauma, that is physical or chemical agents.

b. Due to local infection example dental ulcer, pressure sore

 Specific ulcers: Caused by specific infection

a. Syphilitic ulcers (Hunterian chancre)

b. Tubercular  ulcers, actinomycosis

Trophic ulcer:- Caused by two factors:

Diminished nutrition due to inadequate blood supply to the tissues

Eg. Ulcers in Buerger’s Disease, Artherosclerosis

b. Diminished or absence of sensation of the skin leading to perforating ulcer of the foot

iv. Malignant ulcer: Due to squamous cell carcinoma, rodent ulcers and melanoma.

B) Clinical classification of ulcers

1. Acute Ulcer:  The edge is inflamed oedematous and painful with slough in the floor and n o granulation tissue. Profuse purulent Discgarge seen

2. Healing ulcers: edge sloping with bluish margin The floor is covered with a red, healthy granulation tissue.

3. Chronic or callous ulcer (non- healing) There is no tendency to heal by itself, the base is jndurated  unhealthy granulation tissue is present in the floor The edge is rounded and thickened.

Chronic ulcer occur due to:

Chronic infection , Defective circulation , Foreign body, Persistent local oedema , Malignancy , Diabetes , Malnutrition (loss of proteins), Gout

Specific Ulcers

Tubeculous Ulcer

Edge Undermined, floor contains granulation tissue a watery discharge is present. Caseous material is found in the floor of the ulcer. It usually occurs in tubercular lymphadenitis in the neck, axilla or groin.

Syphilitic Ulcer

a) Huntarian Chancre or  primary sore or hard chancre: usuaIly occurs over the genitalia especially on penis. Occurs in the primary stage of syphilis Ulcer is round or oval, it is hard,indurated, elevated and painless It feels like a button, discharges serum containing spirochetes (cork screw) which is highly infective.

b) In the Secondary stage mucous patches and condylomata occurs The ulcers are shallow white patches, of sodden thickness which occur in the mouth and tongue. Condyloma are hypertrophied epithelium with serous discharge occurring in mucocutaneous junction around the anus. The regional lymphnod (inguinal transverse chain) are enlarged.

c) In tertiary stage of syphilis gummatous ulcers occur They have a punched  out edge and wash Ieather floor. They occur on the subcutaneous bones like sternum and tibia. They are painless and refuse to heal.

Soft Sore (chanchroid)

They are painful muitiple ulcers, with copious discharge. They are caused by Bacillus Ducrey  lncubation time is 3 to 4 days. located on glans penis and prepuce is due to venereal infection. They are associated with enlarged called bilateral inguinal lymphnodes

Tropical ulcer:

a) Oriental Sore - due to L. Tropica (lieshmaniasis)

b) Ulcers and sinuses are due to guinea worm abscess

c) Histoplasmosis with multiple ulcers on the tibia.

d) Chronic ulcers due to yaws

e) Amoebic ulcers occur in colon_and rectum , flask shaped ulcers , undermined edge , caused by  Entamoeba Histolytica

Varicose Ulcer:

Associated with varicose veins. Occurs on the inner aspect of the lower third of leg , chronic ulcer The surrounding area is pigmented and eczema is present. The sore is longitudinally oval It does not penetrate the deep fascia and is painless The base is adherent to the periosteum of the tibia

Rodent ulcer

Usually Occurs on the face above a line joining the lobule of the ear to the angle of the mouth. Usually occurs at the inner canthous of the eye . Edge is raised and rolled, Erodes the deeper structures and the bone, the lyrnph nodes are not involved.

Treatment: If small wide excision is done with skin grafting, If large, radiotherapy is given.

Malignant Ulcer

Occurs due to chronic irritation as in the case of malignant ulcer of the tongue. The edge is everted. The floor is covered with slough and tumor tissue The regional lymph nodes are hard.

Initially mobile later becomes hard

Treatment: Wide excision is done.

Marjolin ulcer: Malignant Ulcer occurring on scar of Burns

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

Inflammation is the respone of the body to an irritant.

Stages of Inflammation

1. General: Temperature Raised. In severe cases bacteremia or septicemia ,rigors may occur.

2. Local: classical signs of inflammation are due to hyperemia and inflammation exudate

i) Heat:  inflammed area feels warmer than the surrounding tissues.

ii) Redness

iii) Tenderness: Due to pressure of exudate on the surrounding nerves  If the exudate is  under tension, e.g. a furuncle (boil) of the ear, pain is severe.

iv) swelling

v) Loss of function.

The termination of Inflammation

This may be by:1. Resolution 2. Suppuration 3. Ulceration 4. Ganangren s. Fibrosis

Management

i. Increase the patients resistance., Rest,  Relief of pain by analgesics,  Diet: High protein and high calorie diet with vitamins,  Antibiotics,  Prevent further contamination of wound.

Surgical measures

1. Excision: If possible as in appendicectomy.

2. Incision and drainage: If an abscess forms.

Excision of Lesions Involving the Jaw Bone

When excising lesions involving the jaw bone, various terminologies are used to describe the specific techniques and outcomes of the procedures.

1. Enucleation

  • Enucleation refers to the separation of a lesion from the bone while preserving bone continuity. This is achieved by removing the lesion along an apparent tissue or cleavage plane, which is often defined by an encapsulating or circumscribing connective tissue envelope derived from the lesion or surrounding bone.
  • Key Characteristics:
    • The lesion is contained within a defined envelope.
    • Bone continuity is maintained post-excision.

2. Curettage

  • Curettage involves the removal of a lesion from the bone by scraping, particularly when the lesion is friable or lacks an intact encapsulating tissue envelope. This technique may result in the removal of some surrounding bone.
  • Key Characteristics:
    • Indicates the inability to separate the lesion along a distinct tissue plane.
    • May involve an inexact or immeasurable thickness of surrounding bone.
    • If a measurable margin of bone is removed, it is termed "resection without continuity defect."

3. Marsupialization

  • Marsupialization is a surgical procedure that involves the exteriorization of a lesion by removing overlying tissue to expose its internal surface. This is done by excising a portion of the lesion bordering the oral cavity or another body cavity.
  • Key Characteristics:
    • Multicompartmented lesions are rendered unicompartmental.
    • The lesion is clinically cystic, and the excised tissue may include bone and/or overlying mucosa.

4. Resection Without Continuity Defect

  • This term describes the excision of a lesion along with a measurable perimeter of investing bone, without interrupting bone continuity. The anatomical relationship allows for the removal of the lesion while preserving the integrity of the bone.
  • Key Characteristics:
    • Bone continuity is maintained.
    • Adjacent soft tissue may be included in the resection.

5. Resection With Continuity Defect

  •  This involves the excision of a lesion that results in a defect in the continuity of the bone. This is often associated with more extensive resections.
  • Key Characteristics:
    • Bone continuity is interrupted.
    • May require reconstruction or other interventions to restore function.

6. Disarticulation

  •  Disarticulation is a special form of resection that involves the temporomandibular joint (TMJ) and results in a continuity defect.
  • Key Characteristics:
    • Involves the removal of the joint and associated structures.
    • Results in loss of continuity in the jaw structure.

7. Recontouring

  •  Recontouring refers to the surgical reduction of the size and/or shape of the surface of a bony lesion or bone part. The goal is to reshape the bone to conform to the adjacent normal bone surface or to achieve an aesthetic result.
  • Key Characteristics:
    • May involve lesions such as bone hyperplasia, torus, or exostosis.
    • Can be performed with or without complete eradication of the lesion (e.g., fibrous dysplasia).

Types of Head Injury

1. Extradural Hematoma (EDH)

Overview

  • Demographics: Most common in young male patients.
  • Association: Always associated with skull fractures.
  • Injured Vessel: Middle meningeal artery.
  • Common Site of Injury: Temporal bone at the pterion (the thinnest part of the skull), which overlies the middle meningeal artery.
  • Location of Hematoma: Between the bone and the dura mater.

Other Common Sites

  1. Frontal fossa
  2. Posterior fossa
  3. May occur following disruption of major dural venous sinus.

Classical Presentation

  • Initial Injury: Followed by a lucid interval where the patient may only complain of a headache.
  • Deterioration: After minutes to hours, rapid deterioration occurs, leading to:
    • Contralateral hemiparesis
    • Reduced consciousness level
    • Ipsilateral pupillary dilatation (due to herniation)

Imaging

  • CT Scan: Shows a lentiform (lens-shaped or biconvex) hyperdense lesion between the brain and skull.

Treatment

  • Surgical Intervention: Immediate surgical evacuation via craniotomy.
  • Mortality Rate: Overall mortality is 18% for all cases of EDH, but only 2% for isolated EDH.

2. Acute Subdural Hematoma (ASDH)

Overview

  • Location: Accumulates in the space between the dura and arachnoid.
  • Injury Mechanism: Associated with cortical vessel disruption and brain laceration.
  • Primary Brain Injury: Often associated with primary brain injury.

Presentation

  • Consciousness: Impaired consciousness from the time of impact.

Imaging

  • CT Scan: Appears hyperdense, with hematoma spreading diffusely and having a concavo-convex appearance.

Treatment

  • Surgical Intervention: Evacuation via craniotomy.
  • Mortality Rate: Approximately 40%.

3. Chronic Subdural Hematoma (CSDH)

Overview

  • Demographics: Most common in patients on anticoagulants and antiplatelet agents.
  • History: Often follows a minor head injury weeks to months prior.
  • Pathology: Due to the tear of bridging veins leading to ASDH, which is clinically silent. As the hematoma breaks down, it increases in volume, causing mass effect on the underlying brain.

Clinical Features

  • Symptoms may include:
    • Headache
    • Cognitive decline
    • Focal neurological deficits (FND)
    • Seizures
  • Important to exclude endocrine, hypoxic, and metabolic causes in this group.

Imaging

  • CT Scan Appearance:
    • Acute blood (0–10 days): Hyperdense
    • Subacute blood (10 days to 2 weeks): Isodense
    • Chronic (> 2 weeks): Hypodense

Treatment

  • Surgical Intervention: Bur hole evacuation rather than craniotomy.
  • Anesthesia: Elderly patients can often undergo surgery under local anesthesia, despite comorbidities.

4. Subarachnoid Hemorrhage (SAH)

Overview

  • Causes: Most commonly due to aneurysms for spontaneous SAH, but trauma is the most common cause overall.
  • Management: Conservative treatment is often employed for trauma cases.

5. Cerebral Contusions

Overview

  • Definition: Bruising of the brain tissue due to trauma.
  • Mechanism: Often occurs at the site of impact (coup) and the opposite side (contrecoup).
  • Symptoms: Can range from mild confusion to severe neurological deficits depending on the extent of the injury.

Imaging

  • CT Scan: May show areas of low attenuation (hypodense) or high attenuation (hyperdense) depending on the age of the contusion.

Treatment

  • Management: Depends on the severity and associated injuries; may require surgical intervention if there is significant mass effect.

Explore by Exams