NEET MDS Synopsis
ECG FINDINGS
Physiology
1. Hypothermia → Elevation of the j-point — Osborne wave.
2. Hyperkalemia → peaking (tenting) of T-wave, ↓-P-wave amplitude, widening of the QRS interval, cardiac arrest with sine wave (in severe Hyper kalemia)
3. Hypokalemia → Prominent ‘U’-wave, prolongation of ‘QT’ interval.
4. Hypocalcemia → Prolong QT interval
5. Hyper calcemia — Short QT interval.
6. Digitalis toxicity — short QT interval with “scooping” of the ST-T wave comples (i.e. Depression of ST-T segment)
7. Sub arachnoid Hemorrhage→ “CVAT-wave” pattern → marked QT prolongation with deep wide T-wave inversions
8. M.I → T-wave inversion
Tracheostomy
General SurgeryTracheostomy
Tracheostomy is a surgical procedure that involves creating an opening in the
trachea (windpipe) to facilitate breathing. This procedure is typically
performed when there is a need for prolonged airway access, especially in cases
where the upper airway is obstructed or compromised. The incision is usually
made between the 2nd and 4th tracheal rings, as entry through the 1st ring can
lead to complications such as tracheal stenosis.
Indications
Tracheostomy may be indicated in various clinical scenarios, including:
Acute Upper Airway Obstruction: Conditions such as
severe allergic reactions, infections (e.g., epiglottitis), or trauma that
obstruct the airway.
Major Surgery: Procedures involving the mouth, pharynx,
or larynx that may compromise the airway.
Prolonged Mechanical Ventilation: Patients requiring
artificial ventilation for an extended period, such as those with
respiratory failure.
Unconscious Patients: Situations involving head
injuries, tetanus, or bulbar poliomyelitis where airway protection is
necessary.
Procedure
Technique
Incision: A horizontal incision is made in the skin
over the trachea, typically between the 2nd and 4th tracheal rings.
Dissection: The subcutaneous tissue and muscles are
dissected to expose the trachea.
Tracheal Entry: An incision is made in the trachea, and
a tracheostomy tube is inserted to maintain the airway.
Complications of Tracheostomy
Tracheostomy can be associated with several complications, which can be
categorized into intraoperative, early postoperative, and late postoperative
complications.
1. Intraoperative Complications
Hemorrhage: Bleeding can occur during the procedure,
particularly if major blood vessels are inadvertently injured.
Injury to Paratracheal Structures:
Carotid Artery: Injury can lead to significant
hemorrhage and potential airway compromise.
Recurrent Laryngeal Nerve: Damage can result in
vocal cord paralysis and hoarseness.
Esophagus: Injury can lead to tracheoesophageal
fistula formation.
Trachea: Improper technique can cause tracheal
injury.
2. Early Postoperative Complications
Apnea: Temporary cessation of breathing may occur,
especially in patients with pre-existing respiratory issues.
Hemorrhage: Postoperative bleeding can occur, requiring
surgical intervention.
Subcutaneous Emphysema: Air can escape into the
subcutaneous tissue, leading to swelling and discomfort.
Pneumomediastinum and Pneumothorax: Air can enter the
mediastinum or pleural space, leading to respiratory distress.
Infection: Risk of infection at the incision site or
within the tracheostomy tube.
3. Late Postoperative Complications
Difficult Decannulation: Challenges in removing the
tracheostomy tube due to airway swelling or other factors.
Tracheocutaneous Fistula: An abnormal connection
between the trachea and the skin, which may require surgical repair.
Tracheoesophageal Fistula: An abnormal connection
between the trachea and esophagus, leading to aspiration and feeding
difficulties.
Tracheoinnominate Arterial Fistula: A rare but
life-threatening complication where the trachea erodes into the innominate
artery, resulting in severe hemorrhage.
Tracheal Stenosis: Narrowing of the trachea due to scar
tissue formation, which can lead to breathing difficulties.
Gastric acid secretion inhibitors
Pharmacology
Gastric acid secretion inhibitors (antisecretory drugs):
HCl is secreted by parietal cells of the gastric mucosa which contain receptors for acetylcholine (muscarinic receptors: MR), histamine (H2R), prostaglandins (PGR) and gastrin (GR) that stimulate the production, except PGs which inhibit gastric acid production.
Therefore, antagonists of acetylcholine, histamine and gastrin inhibit gastric acid secretion (antisecretory). On the other hand, inhibitors of PGs biosynthesis such as NSAIDs with reduce cytoprotective mechanisms and thus promote gastric mucosal erosion. Also, the last step in gastric acid secretion from parietal cells involve a pump called H+ -K+-ATPase (proton pump). Drugs that block this pump will inhibit gastric acid secretion. Antisecretory drugs include:
1. Anticholinergic agents such as pirenzepine, dicyclomine, atropine.
2. H2-receptors blocking agents such as Cimetidine, Ranitidine, Famotidine, Nizatidine (the pharmacology of these agents has been discussed previously).
3. Gastrin-receptor blockers such as proglumide.
4. Proton pump inhibitors such as omeprazole, lansoprazole.
Major clinical indications of antisecretory drugs:
• Prevention & treatment of peptic ulcer disease.
• Zollinger Ellison syndrome.
• Reflux esophagitis.
Infectious Mononucleosis
General Pathology
Infectious Mononucleosis
It is an Epstein Barr virus infection in children and young adults.
Features
-Constitutional symptoms.
-Sore throat.
-Lymphnode enlargement.
-Skin rashes
-Jaundice.
-Rarely pneumonia, meningitis and encephalitis.
Blood Picture
- Total count of I0,000. 20,000 /cu.mm.
- Lymphocytosis (50-90%) with atypical forms. They are larger with more cytoplasm which may be vacuolated or basophilic. Nucleus may be indented. with nucleoli (Downy type I to III).
- Platelets may be reduced.
- Paul Bunell test (for heterophil antibody against sheep RBC) is positive
FUNDAMENTALS OF INJECTION TECHNIQUE
Pharmacology
FUNDAMENTALS OF INJECTION TECHNIQUE
There are 6 basic techniques for achieving local anesthesia of the structures of the oral cavity:
1. Nerve block
2. Field block
3. Infiltration/Supraperiosteal
4. Topical
5. Periodontal ligament (PDL)
6. Intraosseous
Nerve block- Nerve block anesthesia requires local anesthetic to be deposited in close proximity to a nerve trunk. This results in the blockade of nerve impulses distal to this point. It is also important to note that arteries and veins accompany these nerves and can be damaged. To be effective, the local anesthetic needs to pass only through the nerve membrane to block nerve conduction Field block/Infiltration/Supraperiosteal - Field block, infiltration and supraperiosteal injection techniques, rely on the ability of local anesthetics to diffuse through numerous structures to reach the nerve or nerves to be anesthetized:
- Periosteum
- Cortical bone
- Cancellous bone
- Nerve membrane
Topical - Topical anesthetic to be effective requires diffusion through mucous membranes and nerve membrane of the nerve endings near the tissue surface
PDL/Intraosseous - The PDL and intraosseous injection techniques require diffusion of local anesthetic solution through the cancellous bone (spongy) to reach the dental plexus of nerves innervating the tooth or teeth in the immediate area of the injection. The local anesthetic then diffuses through the nerve membrane
Immunology
General Microbiology
Immunology:
The branch of life science which deals with immune reaction is known as immunology.
Components of Immune System:
The immune system consists of a network of diverse organs and tissue which vary structurally as well as functionally from each other. These organs remain spreaded throughout the body. Basically, immune system is a complex network of lymphoid organs, tissues and cells.
These lymphoid organs can be categorized under three types depending upon their functional aspects:
i. Primary lymphoid organ.
ii. Secondary lymphoid organ.
iii.Tertiary lymphoid organ.
White blood cells or leukocytes are the basic cell types which help to give rise to different types of cells which participate in the development of immune response . WBC are classified into granulocytes and agranulocytes depending on the presence or absence of granules in the cytoplasm.
Agranular leukocytes are of two types, viz., lymphocytes and monocytes. Lymphocytes play pivotal role in producing defensive molecules of immune system. Out of all leukocytes, only lymphocytes possess the quality of diversity, specificity, memory and self-non self recognition as various important aspects of immune response.
Other cell types remain as accessory one; help to activate lymphocytes, to generate various immune effector cells, to increase the rate of antigen clearance
All cells of the immune system have their origin in the bone marrow
myeloid (neutrophils, basophils, eosinpophils, macrophages and dendritic cells)
lymphoid (B lymphocyte, T lymphocyte and Natural Killer) cells .
The myeloid progenitor (stem) cell in the bone marrow gives rise to erythrocytes, platelets, neutrophils, monocytes/macrophages and dendritic cells whereas the lymphoid progenitor (stem) cell gives rise to the NK, T cells and B cells.
For T cell development the precursor T cells must migrate to the thymus where they undergo differentiation into two distinct types of T cells, the CD4+ T helper cell and the CD8+ pre-cytotoxic T cell.
Two types of T helper cells are produced in the thymus the TH1 cells, which help the CD8+ pre-cytotoxic cells to differentiate into cytotoxic T cells, and TH2 cells, which help B cells, differentiate into plasma cells, which secrete antibodies.
Function of the immune system is self/non-self discrimination.
This ability to distinguish between self and non-self is necessary to protect the organism from invading pathogens and to eliminate modified or altered cells (e.g. malignant cells).
Since pathogens may replicate intracellularly (viruses and some bacteria and parasites) or extracellularly (most bacteria, fungi and parasites), different components of the immune system have evolved to protect against these different types of pathogens.
COMPOSITE RESINS - Properties
Dental Materials
Properties-improve with filler content
Physical
Radiopacity depends on ions in silicate glass or the addition of barium sulfate (many systems radiolucent)
Coefficient of thermal expansion is 35 to 45 ppm/C and decreases with increasing filler content
Thermal and electrical insulators
Chemical
Water absorption is 0.5 % to 2.5% and increases with polymer level)
Acidulated topical fluorides (e.g., APF) tend to dissolve glass particles, and thus composites should be protected with petroleum jelly (Vaseline) during those procedures
Color changes occur in resin matrix with time because of oxidation, which produces colored by-products
Mechanical
Compressive strength is 45,000 to 60,000 lb/ in2, which is adequate
Wear resistance-improves with higher filler content, higher percentage of conversion in curing, and use of microfiller, but it is not adequate for some posterior applications
Surfaces rough from wear retain plaque and stain more readily
Biologic
Components may be cytotoxic, but cured composite is biocompatible as restorative filling material
LIPIDS
Biochemistry
LIPIDS
The lipids are a heterogeneous group of compounds, including fats, oils, steroids, waxes, and related compounds, which are related more by their physical than by their chemical properties.
Lipids are non-polar (hydrophobic) compounds, soluble in organic solvents.
Most membrane lipids are amphipathic, having a non-polar end and a polar end
Lipids are important in biological systems because they form the cell membrane, a mechanical barrier that divides a cell from the external environment.
Lipids also provide energy for life and several essential vitamins are lipids.
Lipids can be divided in two major classes, nonsaponifiable lipids and saponifiable lipids.
A nonsaponifiable lipid cannot be broken up into smaller molecules by hydrolysis, which includes triglycerides, waxes, phospholipids, and sphingolipids.
A saponifiable lipid contains one or more ester groups allowing it to undergo hydrolysis in the presence of an acid, base, or enzyme.
Nonsaponifiable lipids include steroids, prostaglandins, and terpenes
Nonpolar lipids, such as triglycerides, are used for energy storage and fuel.
Polar lipids, which can form a barrier with an external water environment, are used in membranes.
Polar lipids include glycerophospholipids and sphingolipids.
Fatty acids are important components of all of these lipids.