1. Shock
Amr Mohsen

2. What is shock? Acute circulatory failure leading to
Inadequate tissue perfusion
that results in
Generalized organ hypoxia

3. 3 components
The cardiovascular system is made up of three key elements (figure 1):  a pump, tubing and a fluid. The pump propels the fluid, the tubing distributes and collects it. If a patient becomes hypotensive, either the pump is not working properly, there is not enough fluid in the system, or the distribution network is malfunctioning.
Under normal conditions, the various components of the cardiovascular system are interdependent, and if one element malfunctions, the others compensate to return the blood pressure to normal. An example of this is when a patient bleeds: the volume of fluid falls, and in response, the blood vessels tighten up (vasoconstrict), and the heart rate rises.

4. cardiovascular physiologic reserve
1. Heart Rate
2. Stroke Volume [venous return (blood volume) & myocardial contractility & peripheral resistance]
3. Peripheral Resistance
All exist in dynamic equilibrium. These interactions maintain blood pressure. If one of the three becomes abnormal, the other two compensate.

5. Compensatory mechanisms
Receptors
Respond to
Results
Sympatho-Adrenal Response
Carotid & aortic baro-receptors
Reduced baroreceptor stretch
++ HR
++ SV
= maintain CO
VC (selective)
= maintain ABP

6. Compensatory mechanisms
Receptors
Respond to
Results
ADH (VASOPRESSIN)
Osmoreceptors
Increased osmolality
Water retention VC

7. Compensatory mechanisms
Receptors
Respond to
Results
RENIN
(Angiotensin ii & AldosteronE)
Juxtaglomerular apparatus
Renal ischemia VC
Salt & water retention

8. Compensatory mechanisms
Sympatho-adrenal Response

9. Hypotension is an indication of:
An abnormality of Heart Rate, Stroke Volume or Peripheral Resistance
Failure of the others to compensate.

10. Classification of shock
failure
loss
=hypovolemia
maldistribution
When there is evidence of end organ insufficiency (confusion, oliguria or lactic academia), then hypotension has caused “shock.” In shock – definitive evidence of hypotension (inadequate blood pressure to maintain tissue perfusion) – at least one element of the cardiovascular system has malfunctioned, and the others have failed to adequately compensate. The simplest way to describe shock is 1) Pump failure – “cardiogenic” shock, 2) Tubing malfunction- “distributive” shock, & 3) Fluid loss – “hypovolemic shock”.
The treatment of shock depends on the cause. The commonest type – hypovolemic – is treated by replacing the fluid that is lost, blood or plasma. Cardiogenic shock is managed by using therapies that improve overall cardiac function. Distributive shock is treated by either loosening up constricted blood vessels or tightening up dilated vessels. It is important to remember that shock is failure of circulation and failure of compensation, and two separate types overlap: e.g. in anaphylaxis, there is distributive shock due to mast cell degranulation and vasodilatation. In this situation the failure is the vasodilatation, but there is failure of compensation as the volume of blood in the vasculature is inadequate to maintain pressure, and the patient becomes “relatively hypovolemic”. The treatment therefore is fluid loading and vasoconstrictors.

11. Classification of shock
Hypovolemic shock
blood loss, plasma loss (burns), fluid loss
Cardiogenic shock (pump failure)
Arrhythmias, MI, tamponade
Maldistribution shock
Septic shock
Spinal shock
Anaphylactic shock

12. Pathophysiology

14. ARDS Impaired ventilation Impaired perfusion Impaired diffusion
Stiff lungs (surfactant def.)
Alveolar oedema
Impaired perfusion
Shock
Shunts
Impaired diffusion
Oedema of alveolo-capillary membrane

15. ARDS
ARDS
Late finding
Normal Chest X-ray

16. DIC

17. DIC Low platelet count Low fibrinogen Prolonged PT & APTT
Elevated Fibrin-degradation product
Serious sign

18. Management of Shock & MOF
In ICU

19. Eradicate sepsis (pus drainage) Antibiotics
Treat Cause
Examples
Control bleeding
Eradicate sepsis (pus drainage)
Antibiotics

20. ECG Clinical parameters Pulse Temp (peripheral & core) Blood pressure
Respiratory rate
Monitoring
Continuous
ECG
Pulse oxymetry

21. Optimum output 0.5-1ml/kg/hour.
Urine output
Optimum output 0.5-1ml/kg/hour.
Monitoring
Temperature. A simple non-invasive method of assessing cardiac output and peripheral perfusion is to measure the difference between the peripheral and core temperature. The former is measured by a sensor attached to the big toe, and the latter by a probe placed in either the rectum or the oesophagus. In a warm ambient temperature, the core is higher than peripheral temperature by a gradient that should not exceed 2°C. Any increase in this gradient is a very sensitive indicator of decreased perfusion.

22. (1) Arterial cannula for ABP
Monitoring
(invasive)
Central venous pressure (CVP). The CVP is the venous pressure in the right atrium and is equal to the end-diastolic pressure in the right ventricle and is a measure of the preload to this chamber. To measure the CVP, a catheter is placed in the right atrium via the median-cubital vein, the subclavian vein or the internal jugular vein. The position of the venous catheter is checked by chest X-ray. The radiograph also serves to rule out pneumothorax due to accidental pleural injury during its insertion. The normal pressure is 5-10 cm of water. Assuming that cardiac function is normal, the CVP roughly corresponds to the blood volume. Thus, a high pressure indicates overtransfusion, while a low pressure indicates hypovolaemia.
Pulmonary artery wedge pressure (PAWP). When the right side of the heart is functioning abnormally, it is highly probable that the left side of the heart is equally affected. In such a case, it is recommended to measure PAWP by the use of a Swan-Ganz catheter which is passed into a small branch of the pulmonary artery where it becomes wedged. As the balloon of the catheter occludes this small branch, the pressure measured at the catheter tip reflects that in the left side of the heart.
(2) CVP
N= 0-8 cmH2O
(3) Swan Ganz (PAWP)

23. Renal function tests (Urea & elect) Arterial Bl Gases (ABGs) Lactates
Monitoring
Laboratory tests
CBC
Renal function tests (Urea & elect)
Arterial Bl Gases (ABGs)
Lactates
Liver function tests
PT, PTT & FDP

24. Normal Arterial Bl Gases (ABGs) ~ 7.4 pH ~ 100 PO2 ~ 40 PCO2
~ 25 mmol/L
HCO3-
Monitoring
Normal serum electrolytes
~ 142 mmol/L
Na+
~ 4 mmol/L K+
~ 103 mmol/L
Cl-

26. Respiration Support Body Systems Clear airway - Suction of secretions
- Tracheal intubation or tracheostomy
Oxygen (essential)
- Mask for respiratory distress
- Mechanical ventilation for respiratory failure
PO2 < 60mm Hg RR > 35/m

27. Correct acidosis Support Body Systems
Careful use of IV sodium bicarbonate

28. Circulation Support Body Systems
Correction of hypovolaemia (essential)
Two peripheral venous lines
One central venous line
Crystalloids
Blood
Plasma
Medications (if the above fail to restore BP)
Inotropes (e.g., dopamine & dobutamine)
Vasopressors (noradrenaline)

29. Renal Support Body Systems Adequate volume replacement
Dopamine improves renal blood flow
Dialysis in case of acute renal failure (K+ >7mmol/L), until the kidneys recover

30. GIT Support Body Routine acid suppression Systems
IV H2 blockers or Omeprazole

31. Coagulation Support Body Systems Treatment of DIC Platelet transfusion
Fresh Frozen Plasma (FFP) as it contains coagulation factors

32. Mortality of MOF Renal failure only 8% Renal + other organ failure 70%
Three failing organs 90%