Ischemia and Infarction: A Comprehensive Overview in Ayurveda, Summaries of Pathology

Download Ischemia and Infarction: A Comprehensive Overview in Ayurveda and more Summaries Pathology in PDF only on Docsity!

HAEMODYN

AMIC

DISORDERS

Dr. Akshata B. Patil BAMS,MD Assistant Professor Rognidan & Vikriti Vigyan Ideal College of Ayurved, Wada

POINTS IN SYLLABUS

 INFLAMMATION  SEPTICAEMIA  (^) OEDEMA  SHOCK  HAEMORRHAGE  THROMBOSIS  (^) EMBOLISM  (^) ISCHEMIA  INFARCTION

 The adverse effects of ischaemia may result from 3 ways: 1) Hypoxia due to deprivation of oxygen to tissues: It may be of 4 types: i)Hypoxic hypoxia : due to low oxygen in arterial blood. ii) Anaemic hypoxia: due to low level of haemoglobin in blood. iii) Stagnant hypoxia: due to inadequate blood supply iv) Histotoxic hypoxia: low oxygen uptake due to cellular toxicity.

2. Malnourishment of cells due to inadequate supply of nutrients to the tissue (i.e. glucose, amino acids): 3 ) Inadequate clearance of metabolites which results in accumulation of metabolic waste- products in the affected tissue. This is relevant in some conditions such as muscleache after ischaemia from heavy exercise.

1)CAUSES IN THE HEART:

Inadequate cardiac output resulting from heart block, ventricular arrest and fibrillation from various causes may cause hypoxic injury to the brain.  If the arrest continues for 15 seconds, consciousness is lost.  If the condition lasts for more than 4 minutes, irreversible ischaemic damage to the brain occurs.  If it is prolonged for more than 8 minutes, death is inevitable.

2) CAUSES IN THE ARTERIES

The commonest and most important causes of ischaemia are due to obstruction in arterial blood supply. These are as under: A) Luminal occlusion of artery: a) Thrombosis b) Embolism B) Causes in the arterial walls: a) Vasospasm (e.g. in Raynaud’s disease) b) Hypothermia c) Arteriosclerosis d) Polyarteritis nodosa e) Thromboangiitis obliterans (Buerger’s disease) f) Severed vessel wall

3) CAUSES IN THE VEINS

Blockage of venous drainage may lead to engorgement and obstruction to arterial blood supply resulting in ischaemia. The examples include the following: A) Luminal occlusion of vein: a) Thrombosis of mesenteric veins b) Cavernous sinus thrombosis B) Causes in the vessel wall of vein: a) Varicose veins of the legs C) Outside pressure on vein: a) Strangulated hernia b) Intussusception c) Volvulus

4) CAUSES IN THE

MICROCIRCULATION

Ischaemia may result from occlusion of arterioles, capillaries and venules. The causes are as under: A)Luminal occlusion in microvasculature: a) By red cells e.g. in sickle cell anaemia, red cells parasitised by malaria, acquired haemolytic anaemia, sludging of the blood b) By white cells e.g. in chronic myeloid leukaemia c) By fibrin e.g. defibrination syndrome d) By precipitated cryoglobulins e) By fat embolism f) In decompression sickness.

FACTORS DETERMINING

SEVERITY OF ISCHAEMIC INJURY

1. Anatomic pattern
2. General and cardiovascular status
3. Type of tissue affected
4. Rapidity of development
5. Degree of vascular occlusion

ANATOMIC PATTERN

 The extent of injury by ischaemia depends upon the anatomic pattern of arterial blood supply of the organ or tissue affected. There are 4 different patterns of arterial blood supply: i) Single arterial supply without anastomosis Some organs receive blood supply from arteries which do not have significant anastomosis and are thus functional end-arteries. Occlusion of such vessels invariably results in ischaemic necrosis. For example: Central artery of the retina

iii) Parallel arterial supply: Blood supply to some organs and tissues is such that the vitality of the tissue is maintained by alternative blood supply in case of occlusion of one. For example: Arterial supply to forearm by radial and ulnar arteries.

iv) Double blood supply: The effect of occlusion of one set of vessels is modified if an organ has dual blood supply. For example: Lungs are perfused by bronchial circulation as well as by pulmonary arterial branches. Liver is supplied by both portal circulation and hepatic arterial flow

TYPE OF TISSUE AFFECTED

The vulnerability of tissue of the body to the effect of ischaemia is variable. The mesenchymal tissues are quite resistant to the effect of ischaemia as compared to parenchymal cells of the organs. The following tissues are more vulnerable to ischaemia: i) Brain ii) Heart iii) Kidney

RAPIDITY OF DEVELOPMENT Sudden vascular obstruction results in more severe effects of ischaemia than if it is gradual since there is less time for collaterals to develop.

Degree of vascular occlusion

Complete vascular obstruction results in more severe ischaemic injury than the partial occlusion.