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 20-30 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

CrystalloidRingers lactate

Saline

Colloid

GelofusineHaemaccel

Dextran 70*Hetastarch

Plasma or albumen solutions

BloodWhole bloodPacked 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