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
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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.
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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
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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.
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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
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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.
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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.
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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.
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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.
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
- Frontal fossa
- Posterior fossa
- 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.
Walsham’s Forceps
Walsham’s forceps are specialized surgical instruments used primarily in the manipulation and reduction of fractured nasal fragments. They are particularly useful in the management of nasal fractures, allowing for precise adjustment and stabilization of the bone fragments during the reduction process.
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Design:
- Curved Blades: Walsham’s forceps feature two curved blades—one padded and one unpadded. The curvature of the blades allows for better access and manipulation of the nasal structures.
- Padded Blade: The padded blade is designed to provide a gentle grip on the external surface of the nasal bone and surrounding tissues, minimizing trauma during manipulation.
- Unpadded Blade: The unpadded blade is inserted into the nostril and is used to secure the internal aspect of the nasal bone and associated fragments.
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Usage:
- Insertion: The unpadded blade is carefully passed up the nostril to reach the fractured nasal bone and the associated fragment of the frontal process of the maxilla.
- Securing Fragments: Once in position, the nasal bone and the associated fragment are secured between the padded blade externally and the unpadded blade internally.
- Manipulation: The surgeon can then manipulate the fragments into their correct anatomical position, ensuring proper alignment and stabilization.
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Indications:
- Walsham’s forceps are indicated for use in cases of nasal fractures, particularly when there is displacement of the nasal bones or associated structures. They are commonly used in both emergency and elective settings for nasal fracture management.
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Advantages:
- Precision: The design of the forceps allows for precise manipulation of the nasal fragments, which is crucial for achieving optimal alignment and aesthetic outcomes.
- Minimized Trauma: The padded blade helps to reduce trauma to the surrounding soft tissues, which can be a concern during the reduction of nasal fractures.
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Postoperative Considerations:
- After manipulation and reduction of the nasal fragments, appropriate postoperative care is essential to monitor for complications such as swelling, infection, or malunion. Follow-up appointments may be necessary to assess healing and ensure that the nasal structure remains stable.
Dautrey Procedure
The Dautrey procedure is a surgical intervention aimed at preventing dislocation of the temporomandibular joint (TMJ) by creating a mechanical obstacle that restricts abnormal forward translation of the condylar head. This technique is particularly beneficial for patients who experience recurrent TMJ dislocations or subluxations, especially when conservative management strategies have proven ineffective.
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Indications:
- The Dautrey procedure is indicated for patients with a history of recurrent TMJ dislocations. It is particularly useful when conservative treatments, such as physical therapy or splint therapy, have failed to provide adequate stabilization of the joint.
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Surgical Technique:
- Osteotomy of the Zygomatic Arch: The procedure begins with an osteotomy, which involves surgically cutting the zygomatic arch, the bony structure that forms the prominence of the cheek.
- Depressing the Zygomatic Arch: After the osteotomy, the zygomatic arch is depressed in front of the condylar head. This depression creates a physical barrier that acts as an obstacle to the forward movement of the condylar head during jaw opening or excessive movement.
- Stabilization: The newly positioned zygomatic arch limits the range of motion of the condylar head, thereby reducing the risk of dislocation during functional activities such as chewing or speaking.
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Mechanism of Action:
- By altering the position of the zygomatic arch, the Dautrey procedure effectively changes the biomechanics of the TMJ. The new position of the zygomatic arch prevents the condylar head from translating too far forward, which is a common cause of dislocation.
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Postoperative Care:
- Following the procedure, patients may require a period of recovery
and rehabilitation. This may include:
- Dietary Modifications: Soft diet to minimize stress on the TMJ during the healing process.
- Pain Management: Use of analgesics to manage postoperative discomfort.
- Physical Therapy: Exercises to restore normal function and range of motion in the jaw.
- Following the procedure, patients may require a period of recovery
and rehabilitation. This may include:
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Outcomes:
- The Dautrey procedure has been shown to be effective in preventing recurrent TMJ dislocations. Patients often experience improved joint stability and a better quality of life following the surgery. Successful outcomes can lead to reduced pain, improved jaw function, and enhanced overall satisfaction with treatment.
Zygomatic Bone Reduction
When performing a reduction of the zygomatic bone, particularly in the context of maxillary arch fractures, several key checkpoints are used to assess the success of the procedure. Here’s a detailed overview of the important checkpoints for both zygomatic bone and zygomatic arch reduction.
Zygomatic Bone Reduction
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Alignment at the Sphenozygomatic Suture:
- While this is considered the best checkpoint for assessing the reduction of the zygomatic bone, it may not always be the most practical or available option in certain clinical scenarios.
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Symmetry of the Zygomatic Arch:
- Importance: This is the second-best checkpoint and
serves multiple purposes:
- Maintains Interzygomatic Distance: Ensures that the distance between the zygomatic bones is preserved, which is crucial for facial symmetry.
- Maintains Facial Symmetry and Aesthetic Balance: A symmetrical zygomatic arch contributes to the overall aesthetic appearance of the face.
- Preserves the Dome Effect: The prominence of the zygomatic arch creates a natural contour that is important for facial aesthetics.
- Importance: This is the second-best checkpoint and
serves multiple purposes:
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Continuity of the Infraorbital Rim:
- A critical checkpoint indicating that the reduction is complete. The infraorbital rim should show no step-off, indicating proper alignment and continuity.
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Continuity at the Frontozygomatic Suture:
- Ensures that the junction between the frontal bone and the zygomatic bone is intact and properly aligned.
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Continuity at the Zygomatic Buttress Region:
- The zygomatic buttress is an important structural component that provides support and stability to the zygomatic bone.
Zygomatic Arch Reduction
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Click Sound:
- The presence of a click sound during manipulation can indicate proper alignment and reduction of the zygomatic arch.
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Symmetry of the Arches:
- Assessing the symmetry of the zygomatic arches on both sides of the face is crucial for ensuring that the reduction has been successful and that the facial aesthetics are preserved.