1. 1.9
Copyright UKCS #

2. Management of Surgical Emergencies Part 1 : Critical Care
POST-OPERATIVE HYPOXIA
Copyright UKCS #

3. Learning Outcomes Definition of hypoxia Pathophysiology
How to assess Symptoms and Signs
Management protocols
Copyright UKCS #

4. B
A — C — T
An important ETCC concept: ABC exist to support tissue oxygenation and organ function.
Copyright UKCS #

5. Definition Hypoxia is impaired tissue oxygenation
Hypoxia is one of the most common post-operative complications
Copyright UKCS #

6. Definition Hypoxia is impaired tissue oxygenation
Hypoxia is one of the most common post-operative complications
Copyright UKCS #

7. Oxygen delivery is fundamental to managing sick patients.
oxygen content x cardiac output
Oxygen content = (Hb x 1.36 x SaO2) + ( x PaO2)
(At Hb=15 and SaO2=99 blood carries 200ml O2/liter)
CO = SV x HR
BP = CO x PR
Copyright UKCS #

8. Oxygen delivery depends on:
Airway
Ventilation:
Central drive, volume, rate, FRC
Oxygen availability:
%, pA (air and alveoli), pulmonary capillaries
Oxygen transport:
Hb, Cardiac output, Peripheral resistance
Tissues:
Oxygen release, Diffusion, Utilisation
Copyright UKCS #

9. What needs to be maintained to prevent tissue hypoxia?
Patent airway and effective ventilation
Effective gas interchange
Arterial oxygen saturation (SaO2)
Effective circulation (BP=COxPR)
Haemoglobin concentration and integrity
O2 release from Hb
Extracellular diffusion
Oxygen use by cells
Copyright UKCS #

10. Causes of Hypoxia: ↓pAO2 or ∆FiO2 ↓V ∆V/∆Q ↓Hb ↓CO
Copyright UKCS #

11. Surgical patients at risk of Hypoxia:
Pre-op hypoxia
Smokers, COPD
Reduced FRC
Elderly, Obesity, Diabetes, GA
Surgical pathology
Restricted ventilation, SIRS
Post-op Sedation
Hypothermia
Fluid overload
Copyright UKCS #

12. Assessment: History Examination Investigations
Risk groups, recent events, charts, medication
Examination
Signs of organ dysfunction
Investigations
Pulse oximetry
CXR
ABGs, Hb
ECG
Copyright UKCS #

13. Clinical signs of tissue hypoxia?
Altered mental state
Altered respiratory rate
Arrhythmias
Peripheral vasodilatation
Systemic hypotension
Cyanosis (?)
Copyright UKCS #

14. What does Pulse Oximetry measure?
Gives an estimate of percentage saturation on oxygen binding sites on Hb
NOT the same as PaO2
Related to PaO2 through sigmoid shaped O2-Hb dissociation curve
Copyright UKCS #

15. Oxygen dissociation curve
100 80
% saturation 60 40 20 30 60 90
120
150
pO2 mmHg

16. Pulse Oximetry Remember: 95%-100% = normal
<93% = warning! (ask “Why?”)
<90% = patient in serious trouble (do something now)
Double check that you distinguish the SaO2 from the pulse rate when looking at the monitor.
Copyright UKCS #

17. Copyright UKCS #

18. Error readings in pulse oximetry:
Low cardiac output
Vasoconstriction
SaO2 <70%
Poor positioning
Movement
Hypothermia (often in trauma patients)
Abnormal Hb (COHb, MetHb)
Hyperthermic limb
Dirty probe
Black, blue or green nail polish
External light
Copyright UKCS #

19. Error readings in pulse oximetry:
Low cardiac output
Vasoconstriction
SaO2 <70%
Poor positioning
Movement
Hypothermia (often in trauma patients)
Abnormal Hb (COHb, MetHb)
Hyperthermic limb
Dirty probe
Black, blue or green nail polish
External light
Copyright UKCS #

20. Likely causes of Hypoxia
Pulmonary oedema
Bronchopneumonia
Lobar pneumonia
Pre-existent COPD
Atelectasis with hypoventilation
Pulmonary embolism
ARDS
Copyright UKCS #

21. Pulmonary Oedema Bronchopneumonia Diffusion barrier
“at risk” patient, fluid balance
CXR: diffuse bilateral changes
Bronchopneumonia
Shunting
“at risk” patient
CXR: localised woolly unilateral shadowing
Copyright UKCS #

22. Pulmonary Embolism ARDS Ventilation/perfusion mismatch
“at risk” patient
CXR: usually normal
ARDS
Shunting
“at risk”patient
CXR: bilateral widespread diffuse shadowing
Copyright UKCS #

23. Copyright UKCS #

24. Copyright UKCS #

25. Copyright UKCS #

26. Copyright UKCS #

27. Management Airway Oxygen Ventilation Circulation Other supportive
Physiotherapy; Bronchodilators; Mucolitics
Specific
Antibiotics; Anti-coagulation
Copyright UKCS #

28. Questions?
Copyright UKCS #

29. Summary Aim to prevent hypoxia
Thorough assessment of any postoperative hypoxic patient
Think: Stable or Unstable/Unsure?
Consider all factors in the oxygen delivery pathway.
Think “Why?”
Assessment guides Management
Copyright UKCS #