NEET MDS Lessons
General Surgery
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).
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.
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
-
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.
-
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.
-
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.
-
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.