Hypovolemia decrease in volume of blood plasma

What is insensible fluid loss?

The loss of fluid by evaporation through the respiratory tract and skin, which we are not consciously aware of. I.e. NOT ????

When significant blood loss occurs  fall in oxygen carrying capacity of blood, reduction in blood volume  a fall in oxygen delivery.

Acute blood loss: Rapid blood loss causing hypovolaemic shock. Hypovolaemic shock results in multiple organ failure due to inadequate perfusion The human body responds to acute hemorrhage by activating 4 major physiologic systems: the hematologic, cardiovascular, renal, and neuroendocrine systems.

The CVS increase heart rate, increase myocardial contractility and constricting peripheral blood vessels. Secondary to an increased release of norepinephrine and decreased baseline vagal tone (regulated by the baroreceptors in the carotid arch, aortic arch, left atrium, and pulmonary vessels). The cardiovascular system also responds by redistributing blood to the brain, heart, and kidneys and away from skin, muscle, and GI tract.

The renal system stimulates an increase in renin secretion from the juxtaglomerular apparatus Renin converts angiotensinogen to angiotensin I, which subsequently is converted to angiotensin II by the lungs and liver. Angiotensin II has 2 main effects, vasoconstriction of arteriolar smooth muscle & stimulation of aldosterone secretion by the adrenal cortex Aldosterone is responsible for active sodium reabsorption and subsequent water conservation.

The neuroendocrine system Responds to hemorrhagic shock by causing an increase in circulating ADH. ADH is released from the posterior pituitary gland in response to a decrease in BP (detected by baroreceptors) and a decrease in the sodium concentration (detected by osmoreceptors). ADH indirectly leads to an increased reabsorption of water and salt (NaCl) by the distal tubule, the collecting ducts, and the loop of Henle.

Staging of Hypovolemia

Stage 1 Up to 15% blood volume loss (750mls) Compensated by constriction of vascular bed Blood pressure maintained Normal respiratory rate Pallor of the skin Normal mental status to slight anxiety Normal capillary refill Normal urine output

Stage 2 15–30% blood volume loss (750–1500 ml) Cardiac output cannot be maintained by arterial constriction Tachycardia >100bpm Increased respiratory rate Blood pressure maintained Increased diastolic pressure Narrow pulse pressure Sweating from sympathetic stimulation Mildly anxious/Restless Delayed capillary refill Urine output of milliliters/hour

Stage 3 30–40% blood volume loss (1500–2000 ml) Systolic BP falls to 100mmHg or less Classic signs of hypovolemic shock Marked tachycardia >120 bpm Marked tachypnea >30 bpm Decreased systolic pressure Alteration in mental status (confusion, anxiety, agitation) Sweating with cool, pale skin Delayed capillary refill Urine output of approximately 20 milliliters/hour

Stage 4 Loss greater than 40% (>2000mls) Extreme tachycardia (>140 ) with weak pulse Pronounced tachypnea Significantly decreased systolic blood pressure of 70 mmHg or less Decreased level of consciousness, lethargy, coma Skin is sweaty, cool, and extremely pale (moribund) Absent capillary refill Negligible urine output

How would we treat hypovolemic shock?

Table 2. Types of Intravenous Fluids Used in Shock Crystalloid Ringers lactate Saline Colloid Gelofusine Haemaccel Dextran 70* Hetastarch Plasma or albumen solutions Blood Whole blood Packed cells Plasma reduced blood

COMPLICATIONS OF MASSIVE BLOOD TRANSFUSION Acidosis Hyperkalemia Citrate toxicity and hypocalcaemia. Hypothermia Depletion of fibrinogen and coagulation factors Depletion of platelets Disseminated intravascular coagulation (DIC)

Investigations Barium Contrast Studies Plain X-Rays Acute cholitis, calcification in chronic pancreatitis, faecal loading Ultrasound, CT & MRI Radioisotope Imaging Endoscopy

Barium Contrast Studies Barium Swallow –Dysphagia DC Barium Meal –Epigastric Pain, Vomiting Small Bowel follow-through –Diarrhoea, Abdo Pain Barium Enema –Alt bowel habit, Abdo pain

Ultrasound, CT & MRI Ultrasound –Liver, bladder, spleen and pancreas Endoscopic US –OP & Gastric wall, cancer Endoanal Ultrasonography –Sphincter, perianal dx, rect cancer staging CT –Abcesses, diverticulitis, appendicitis, crohns all shown MRI –no ? Raditation, abcesses and fistulae PET –Staging cancer after fludeoxyglucose F18

Radioisotope Imaging

Colonoscopy quiz Success rate for reaching the terminal illeum? Perforation risk? Perf risk ater polypectomy Mortality?

Endoscopy Oesophagogastroduoendoscopy Colonscopy –Whole colon and terminal illeum Enteroscopy –Duodenum to illieum, $$ Wireless capsule endoscopy –Small bowel tumours