2020B Question 08
Discuss the adverse environmental effects of anaesthetic agents in current use
Examiner Report
The question required:
- A basic knowledge of the terms “greenhouse gas”, “ozone layer” and “global warming”
- An explanation of how inhalational agents affect the wider environment
- An explanation of how intravenous agents affect the wider environment
Things that were done particularly well:
- Ranking of agents by degree of impact
- Acknowledging the large amount of non-recyclable, solid waste produced
- Mentioning the adverse effects of N2O upon theatre staff
Things that were done poorly:
- Accurately differentiating between the basic terms
- Understanding the effect of propofol on the wider environment
Model Answer
Structure:
- Definitions
- List of agents
Definitions
| Term | Detail |
|---|---|
| Greenhouse Gas | - Substance that absorbs and emits infrared radiation - e.g. CO2, N2O, methane, ozone |
| Anthropogenic global warming | - Warming of average temperatures on earth caused by greenhouse emissions arising from human activity - Many detrimental environmental effects |
| Ozone layer | - O3 Rich region in the stratosphere - Absorbs UV-B |
Agents
Listed in descending order of toxicity
| Agent | Detail |
|---|---|
| Desflurane | - Direct AGW: 6 hours at Fi 7% ≈ 1000kmg driving - 0.02% metabolised; also resistant to environmental breakdown - Greater impact mostly due to long half life |
| Nitrous Oxide | - Direct AGW: 6 hours at Fi 50% ≈ 500km driving - Depletes ozone layer - Chronic exposure can cause neuropathy, teratogenicity, miscarriage in health care workers due to inactivation of methionine synthetase |
| Sevoflurane | - Direct AGW: 6 hours at Fi 3.5% ≈ 50km driving - ~5% metabolised |
| Propofol | - Minimal impact on AGW, even after taking into account syringe driver, manufacture, procurement - Improperly discarded propofol is toxic to marine life - Syringes and tubing contribute to medical waste - Almost 100% metabolised; metabolites excreted in urine - Environmental effects of metabolites unknown |
| Ketamine | - Minimal impact - Can be used as a sole agent - Minimal effects of ABC - Hence reduces need for other disposable equipment |
| Neuraxial/regional local anaesthetics | - i.e. Bupivacaine, ropivacaine, lignocaine - Minimal direct impact - Can be performed without sedation or general anaesthesia - Hence reduces need for other disposable equipment |