Anaesthetic breathing systems and IVFT

What is the aim of general anaesthesia

• Unconsciousness

• Analgesia

• Muscle relaxation

What are the stages of general anaesthesia

• Preoperative assessment

• Premedication

• Induction

• Maintenance

• Recovery

What should be done in a pre-op assessment

• History

• Clinical exam

• Health status of patient

• Venous access

What are the aims of premedication

• Reduce anxiety

• Ease handling

• Smooth induction

• Smooth maintenance

• Smooth recovery

• Reduce dose of anaesthesia

• Pre-emptive analgesia

What are injectible anaesthetic agents

• Intravenous

• Easy administration

• Rapid, smooth induction

• Short acting

• Can be used for maintenance

What are inhalational anaesthetic agents

• Volatile liquids

• Vaporise and saturate oxygen

• Delivery of oxygen to patient

• Rapid change in depth of anaesthesia

What breathing systems are attached to patients

• Endo-tracheal tube

• V-gel

• Face mask

What is the function of attached breathing systems

• Deliver anaesthetic vapour

• Deliver oxygen

• Remove carbon dioxide

What are the 5 principle components of breathing systems

• Adapter that connects to an endotracheal tube

• Expiratory valve

• Reservoir bag to allow for intermittent positive pressure ventilation should the patient stop breathing

• Fresh gas tubing

• Expired gas tubing

What are rebreathing systems

• Patient rebreathes expired gas

• Economical

• Increased resistance

• Suitable for patients over 15kg

What are non-rebreathing systems

• Patient does not rebreathe expired gas

• Expired gas flushed from system before patients next breath

• Less economical

• Less resistance

• Patients less then 25kg

What is a capillary membrane

• Semi-permeable membrane between blood and interstitial space

• Freely permeable to water and electrolytes NOT to macromolecules

What is a cell membrane

• Semi permeable membrane between interstitial space and cell

• Freely permeable to water

How does fluid move across a semi-permeable membrane

• Governed by hydrostatic pressure

• High pressure to low pressure

• Effected by osmotic and oncotic pressure

What is osmostic pressure created by

• Electrolytes

• Glucose

• Urea

What is oncotic pressure created by

Proteins

What are the different types of fluid

• Crystalloids

• Colloids

• Protein based solution

What is in crystalloids

• Water

• NaCl

What is in colloids

• Water

• NaCl

• Starch

What are protein based solutions

• Non-oxygen carriers - plasma

• Oxygen carriers - whole blood

What is tonicity

The effective osmorality of a solution in relation to plasma

What is isotonic

No net movement

What is hypotonic

Net movement from intravascular space to interstitial space

What is hypertonic

Net movement from interstitial space to intravascular space

What is the appearance of <5% dehdration

• Normal demeanor

What is the appearance of 5% dehydration

• Normal demeanour

• Normal skin turgor

• Mucous membranes sticky to dry

• Globe position normal

What is the appearance of 7% dehydration

• Mildly depressed demeanor

• Mildly decreased skin turgor

• Dry mucous membranes

• Normal globe position

What is the appearance of 10% dehydration

• Moderately depressed demeanor

• Moderately decreased skin turgor

• Dry mucous membranes

• Slightly sunken globe position

What is the appearance of 12% dehydration

• Moribund demeanor

• Skint tent skin turgor

• Dry mucous membranes

• Deeply sunken globe position

What is hypovolaemia

Loss of fluid from intravascular space

What happens during shock

• Hypovolaemia

• Emergency situation

• Need to increase the intravascular volume to maintain cardiac output

• Administer fluids as quickly as possible 

What is the circuit factor of mapleson A

1 x minute volume

What is the circuit factor of mapleson D

2-2.5 x minute volume

What is the circuit factor of mapleson E and F

2.5-3 x minute volume

How is flow rate calculated

Minute volume x circuit factor