Preoperative Starvation Times

1
Pre-operative Starvation Times

• Ayngara Thillaivasan

2
Background

• Reason for pre-operative starvation is to try to
  prevent aspiration of stomach contents during
  anaesthesia.

3
Mendelsons Syndrome

• 1946.
• New York Obstetrician.
• Face mask anaesthesia Ether Nitrous Oxide.
• Aspiration in 66 out of 44016 women.
• 2 Deaths from airway obstruction from solid food.
• Liquid aspiration lead to a syndrome of dyspnoea,
  cyanosis and tachycardia. (All recovered.)

4
Gastric Contents

• Volume pH of gastric contents.
• Determined by oral intake, gastric secretion
  emptying.
• Experiments in 1974 Patients at risk of
  aspiration pneumonitis from the presence of 25mls
  of residual gastric volume of pH lt2.5.
• Entire contents would have to reach the lungs.
• 50 of healthy fasted people gt25ml pH2.

5
Gastric Emptying

• William Beaumont, American army surgeon.
• Canadian fur trapper with a gunshot wound to the
  stomach.
• Permanent gastric fistula.
• Water Exponential process. Half life 10 mins.
  95 clear liquids gone in 1 hr.
• Solids Constant. Starts 1 hr after ingestion.
• 50 of a meal is at the duodenum in 2hrs.

6
Risk Factors For Aspiration

• Emergency procedures.
• Light anaesthesia.
• GI pathology.
• Obesity.
• Opiods.
• Neurological disease.
• Lithotomy position.
• Difficult intubation.
• Reflux disease.
• Hiatus hernia.

7
ASA Task Force Guidelines 1999.

• 10 anaesthesiologists in both private and
  academic practice from America and Canada.
• Not intended as standards or absolute
  requirements.
• The guidelines provide basic recommendations
  that are supported by analysis of current
  literature and by a synthesis of expert opinion,
  open forum commentary, and clinical feasibility
  data.

8
Guidelines(Accepted by the AAGBI.)

• 2-4-6 (?8) Rule.
• 2 hours for clear fluid.
• 4 hours for breast milk.
• 6 hours for solids and non-human milk.
• Preoperative assessment
• Routine use of GI stimulants, gastric acid
  secretion blockers, antacids, antiemetics,
  anticholinergics, and multiple agents is NOT
  recommended.

9
Audit
10
Responses

• 158 Audit forms.
• X2 No induction times.
• X4 No actual starvation times.
• 496 cases 31
• X1 Cancelled. (Not starved for procedure.)

11
Specialties 1
12
Specialties 2
13
Specialties 3
14
Specialties 4
15
Specialties 5
16
Specialties 6
17
Total
18
League Table (Elective)
19
Reasons
20
Lists
21
Position On List
22
List Changes
23
List Changes 2
24
List Changes 3
25
Conclusions

• Insufficient starvation is not a major problem.
• Starvation times are for the most part greatly in
  excess of what is needed.
• Slight difference between elective and urgent
  cases.
• AM lists lead to prolonged starvation times.
• Medical lists are worse than surgical for
  starvation times.
• Altered / overrunning lists have longer
  starvation times.

26
Recommendations

• Limited for prehospital.
• Make sure parents understand.
• Encourage them to follow as fully as possible.
• ?Anaesthetic information?
• Discuss with teams.
• Early realistic decisions when lists are
  changing/overrunning.
• ONCOLOGY.