Question

pathophysiology and etiology of small bowel obstruction and hypovolemic shock

Answer 1

SMALL BOWEL OBSTRUCTION

Pathophysiology :-

Small bowel obstruction (SBO) leads to proximal dilatation of the intestine due to accumulation of gastrointestinal (GI) secretions and swallowed air. Bowel dilatation stimulates cell secretory activity, resulting in more fluid accumulation. This, in turn, leads to increased peristalsis above and below the obstruction, with frequent loose stools and flatus early in its course.

Vomiting occurs if the level of obstruction is proximal. Increasing small bowel distention leads to increased intraluminal pressures. This can cause compression of mucosal lymphatics, leading to bowel wall lymphedema. With even higher intraluminal hydrostatic pressure, increased hydrostatic pressure in the capillary beds results in massive third spacing of fluid, electrolytes and protiens into the intestinal lumen. The fluid loss and dehydration that ensue may be sever and contribute to increased morbidity and mortality.

Etiology :-

The etiology of SBO was adhesions (74%), Crohn's disease(7%), Neoplasia (5%), Hernia (2%), Radiation (1%), and miscellaneous (11%). Patients with Crhon's disease were younger than patients with other etiologies. Surprisingly, reccurence rates were similar for patients treated operatively as for those treated nonoperatively with the exception in the hernia group where higher recurrence rates were noted for patients initially traeted in a nonoperative manner.

HYPOVOLEMIC SHOCK

Pathophysiology :-

  Hypovolemic shock results from depletion of intravascular volume, whether by extracellular fluid loss or blood loss. The body compensates with increased sympathetic tone resulting in increased heart rate, increased cardiac contractility, and peripheral vasoconstriction. The first changes in vital signs seen in hypovolemic shock include an increase in diastolic blood pressure with narrowed pulse pressure. As volume status continues to decrease, systolic blood pressure drops. As a result, oxygen delivery to vital organs is unable to meet oxygen demand. Cells switch from aerobic metabolism to anaerobic metabolism, resulting in lactic acidosis. As sympathetic drive increases, blood flow is diverted from other organs to preserve blood flow to the heart and brain. This propagates tissue ischemia and worsen lactic acidosis. If not corrected, there will be worsening hemodynamic compromise and, eventually, death.

Etiology :-

Hypovolemic shock results from significant and sudden blood or fluid losses within your body. Blood loss of this magnitude can occur because of :

• bleeding from serious cuts or wounds
• bleeding from blunt traumatic injuries due to accidents
• internal bleeding from abdominal organs or ruptured ectopic ppregnancy
• bleeding from the digestive tract
• significant vaginal bleeding
• endometriosis

In addition to actual blood loss, the loss of body fluids can cause a decrease in blood volume this can occur in cases of  :

• excessive or prolonged diarrhea
• sever burns
• protracted and excessive vomiting
• exessive sweating

Blood carries oxygen and other essential substances to your organs and tissues. When heavy bleeding occurs, there is not enough blood in circulation for the heart to be an effective pump. Once your body loses these substances faster than it can replace them, organs in your body begin to shut down and the symptoms of shock occur. Blood pressure plummets, which can be life-threatening.