Week 3 - B - Shock - M.A.P - Cardiogenic, Obstructive, Hypovalameic, Distributive (septic/anaphylactic/neurogenic/adrenal crisis)

Question 1

What is the definition of shock?

Answer 1

It is the clinical syndrome of tissue hypoperfusion due to circulatory failure

Question 2

The mean arterial pressure is a useful value for knowing the perfusion that the body organs are receiving How is the MAP calculated? (think of 5 variations of equations)

Answer 2

• * MAP = CPP (should be 70-105mmHg) - ICP (intracranial pressure - 5-13mmHg)
• * MAP = Cardiac output x Total peripheral resistance
• * MAP = HRxSV x TPR
• * MAP = 2/3 DBP + 1/3 SBP
• * MAP = [2 DPB + SBP] / 3
• * MAP = DBP + 1/3 (SBP-DBP)

Question 3

What is cardiac ouput measured in and why? What is the normal value of the cardiac output?

Answer 3

The cardiac output is simply the volume of blood pumped by the heart per minute. Necessarily, the cardiac output is the product of the heart rate, which is the volume of beats per minute, and the stroke volume, which is volume pumped per beat. CO is measured in L/min (usually around 4-8L/min)

Question 4

When the MAP falls below what level does this lead to organ complications?

Answer 4

When the MAP falls below 65mmHg, can start to get tissue underperfuation leading to signs of shock (clinical syndrome of tissue hypoperfusion due to circulatory failure)

Question 5

Shock is often defined by a low SBP <90mmHg or MAP <65mmHg with evidence of tissue hypoperfusion What may happen to the skin showing tissue hypoperfusion? Usually seen in babies when cold? but can also be seen in cardiogenic shock?

Answer 5

This would be cutis maromata - the skin develops a mottled look appearance Cutis marmorata is a condition where the skin has a pinkish blue mottled or marbled appearance when subjected to cold temperatures - can also be seen incardiogenic shock

Question 6

As MAP = CO x TPR (also known as systemic vascular resisitance (SVR), then what are the two problems that can cause the shock here?

Answer 6

Shock can result from inadequate cardiac ouput or due to a decreased systemic vascular resistance (TPR)

Question 7

With the low BP or low MAP and evidence of tissue hypoperfusion (will be discussed shortly), shock can also affected the urine output and the seym lactate What are signs of tissue hypoperfusion?

Answer 7

This would be an altered mental state - ie confused or agitated Mottled/clammy skin Oliguria

Question 8

Oliguria can be seen as a sign of shock as mentioned. What is olguria defined as? What is polyuria defined as? How full is the bladder when the desire to void usually occurs?

Answer 8

Oliguria - a sign of tissue hypoperfusion occurs when the urinary production is 2.8L urine production in 24 hours Desire to void occurs when bladder volume reaches 250ml

Question 9

What is the serum lactate levels that are measured and are arguably diagnostic of shock? What Serum lactate levels have a significant mortality rate?

Answer 9

Serum lactate levels >2mmol/L are arguably diagnostic of shock Serum lactate levels >4mmol/l have significant mortality

Question 10

SHOCK - very indicative measurements showing tissue hypoperfusion * BP 2mmol/l What are the two factors contributing to MAP that can cause shock? What do we try to keep the MAP above?

Answer 10

Decreased cardiac output or decreased total peripheral resistance (systemic vascular resistance) Want to keep the MAP above at least 65mmHg The way we can calculate MAP as hard to calculate CO and TPR is using the systolic/diastolic BP

Question 11

What are the five main types of shock and how can they be categorized? (4 categeries)

Answer 11

Anaphlactic, neurogenic, cardiogenic, hypovalaemic and septic Fall under the categories Cardiogenic Obstructive Hypovalaemic Distributive

Question 12

What happens in cardiogenic shock? Ie between the CO and SVR What does the compensating mechanism result in?

Answer 12

In cardiogenic shock there is the decrease in force of contraction and stroke volume (volume pumped per beat) and therefore the cardiac output decreases reducing the MAP In an attempt to restore balance the SVR increases hence the patient having cool,clammy peripheries

Question 13

Name some causes of cardiogenic shock? Stuff that may cause reduced force of contraction causing reduced stroke volume causing reduced cardiac output

Answer 13

Arrythmias, MI, valve failure

Question 14

The second category of shock is obstructive shock What occurs in osbtructive shock? What may be seen?

Answer 14

In obstructive shock there is an obstruction to the cardiac outflow causing the venous back pressure This can result in a distended jugular vein and distended neck veins

Question 15

Name 3 causes of obstructive shock?

Answer 15

Cardiac tamponade - obstructs the ventricles form contracting properly Tension pneumothorax - may compress the vena cava Pulmonary embolism - stop blood flow into the lungs and also induces hypoxia as blood cannot circualte/be oxygenised

Question 16

What is the treatment of cardiac tamponade, tension pneumothorax and pulmonary embolus? Obstructive shock, although a second category is basically a subset of cardiogenic shock

Answer 16

Cardiac tamponade - pericardiocentessi Tension pneumothorax - emergency needle decompression 2ind intercostal space mid clavicular line followed by chest drain 5th intercostal space mid axillary line PE- LMWH+Warfarin or Thrombolysis

Question 17

How can the third category, hypovalaemia lead to shock?

Answer 17

There is a reduced venous return to the heart and a lower venous return reduces the end diastolic volume (EDV) meaning the SV decreases and the cardiac output decreases In cardiogenic, obstructive, and hypovolaemic, the SVR will increase to compensate for the CO, causing cool, clammy peripheries

Question 18

What does the Frank -Starling law state?

Answer 18

The stroke volume increases in response to an increase in end diastolic volume when all other factors remain ocnstant

Question 19

What happens to the heart rate, resp rate and mental state as hypovalaemic shock ensures?

Answer 19

Heart rate - continually increases Resp rate - continually increases Mental statsus - normal, anxious, confused, lethagic/non responsive

Question 20

The degree of hypovalaemic shock is graded by the advanced trauma life support (ATLS) into 4 stages depdning on the blood volume lost These stages allow you to try and quantify the degree of haemorrhage causing the shock What are the stages?

Answer 20

Stage 1 - 750ml = 2000ml = >40% blood loss

Question 21

How does distributive shock work? What are the four main causes of distributive shock?

Answer 21

This is where there is a reduced systemic vascular resistance due to vasodilation resulting in warm, red peripheries There is a decrease in MAP with a compensatory increase in CO 4 main causes * Sepsis * Anaphylaxis * Neurogenic * Adrenal crisis

Question 22

The fluid challenge is used in the fluid management of many sick patients. The principle behind the fluid challenge technique is that by giving a small amount of fluid in a short period of time, the clinician can assess whether the patient has a preload reserve that can be used to increase the stroke volume with further fluids. How much fluid is given in the fluid challenge?

Answer 22

1/4 or half a litre of fluid is given over half an hour to see if the patient tolerates this well to therefoe give more fluid

Question 23

Which shock mechanisms present with cold peripheries and which present with warm?

Answer 23

Cardiogenic, obstuctive, hypovalaemic are cold peripheries Distributive (Sepsis, Anaphylaxis Neurogenic, Adrenal Crisis) is warm - lose sympathetic tone

Question 24

What is the order of the treatment of anphylactic shock?

Answer 24

* Lie patient flat to ensure blood flow to organs and brain - raise legs * Give IM adrenaline every 5 minutes until have IV access and patient is better * Give chlorphenamine IV - bocks the effects of histamine as is a H1 receptor antagnosit * Give salbutamol -beta agonist to cause bronchodilation * Give steroids - hydrocortisone IV - prevents the effects of leukotriene

Question 25

What can be emasured in anaphylactic shock?

Answer 25

Serum tryptase - measures the level of mast cell degranulation Tryptase is the most abundant secretory granule-derived serine proteinase contained in mast cells and has been used as a marker for mast cell activation.