There are several factors that may influence your choice of induction agent:

Factor	Examples
Are any agents absolutely contraindicated?	Previous hypersensitivity reaction to the active agent Thiopental and etomidate in porphyria
Next factor

There are several factors that may influence your choice of induction agent:

Factor	Examples
Are any agents absolutely contraindicated?	Previous hypersensitivity reaction to the active agent Thiopental and etomidate in porphyria
Are there any patient-related factors that may influence choice?	Resuscitation state of patient: propofol and thiopental produce more CVS depression than etomidate, so hypovolaemia is a relative contraindication Rapid sequence induction needed: thiopental has a slightly faster onset than propofol Epilepsy: thiopental is antiepileptic Age of patient: presence of ischaemic heart disease
Next factor

There are several factors that may influence your choice of induction agent:

Factor	Examples
Are any agents absolutely contraindicated?	Previous hypersensitivity reaction to the active agent Thiopental and etomidate in porphyria
Are there any patient-related factors that may influence choice?	Resuscitation state of patient: propofol and thiopental produce more CVS depression than etomidate, so hypovolaemia is a relative contraindication Rapid sequence induction needed: thiopental has a slightly faster onset than propofol Epilepsy: thiopental is antiepileptic Age of patient: presence of ischaemic heart disease
Are there any drug-related factors that may influence choice?	Previous reaction to a drug presented in propylene glycol: this should exclude use of etomidate Egg allergy: some consider this a relative contraindication to propofol, although there is no supporting evidence