Rapid recovery, along with other desirable properties, make propofol ideal for use in the OR, as well as in monitored anesthesia care (MAC) and moderate sedation (see Continuum of sedation and associated patient response). Largely due to the potential for progression from moderate sedation to general anesthesia, there's some debate over who should administer propofol.
Contraindications and precautions
Any dose of propofol can result in airway compromise. For this reason, propofol use in the ICU is restricted to intubated patients.2 In any procedural setting, propofol administration can result in the unintended conversion of moderate sedation to general anesthesia.
The American Society of Anesthesiologists (ASA), the American Association of Nurse Anesthetists and the American Association for Accreditation of Ambulatory Surgical Facilities recommend that only persons trained in the administration of general anesthesia, and who aren't simultaneously involved with the procedure, should administer propofol to patients who aren't being artificially ventilated.3 When this recommendation can't be followed, the ASA recommends that nonanesthesia personnel are qualified to provide rescue interventions for patients entering into a state of general anesthesia. In these cases, advanced cardiac life support certification alone isn't sufficient. Formal policies, advanced training (including expertise in intubating patients), and regular competency evaluations are mandatory tools in preparing the nonanesthesia specialist in the administration of propofol and management of patients receiving this medication.3
During propofol administration, cardiac and respiratory function should be assessed through continuous monitoring of respiratory rate, oxygen saturation, blood pressure, and cardiac monitoring. At a minimum, supplemental oxygen by nasal cannula should be administered, with the knowledge that more aggressive airway management may be required. Specially designed nasal cannulas that measure expired carbon dioxide are available and are ideal for monitoring capnography and respiratory rate in patients maintaining a natural airway during sedation.
There's no reversal agent for propofol; this medication should be administered slowly and titrated to achieve the desired effect.
Allergy to propofol should also be considered. In addition to the active component, propofol contains soybean oil, glycerol, and egg yolk phospholipid. Therefore, contraindications to propofol administration include allergy to soybeans or egg lecithin.
Since the introduction of Diprivan, generic preparations of propofol have been formulated and may contain additional compounds. One form of generic propofol contains a sulfite, which is added to retard bacterial growth in the event of accidental contamination.2 Patients with an allergy to sulfa shouldn't receive the generic form of propofol that contains a sulfite, as an anaphylactic reaction may result. However, the most recently introduced form of generic propofol contains benzyl alcohol for inhibition of bacterial growth instead of a sulfite, thereby eliminating concerns related to sulfa allergy.4 In all cases, patients still should be assessed for any allergies pertinent to all available preparations of propofol, including sulfa.
Dosage and administration
In general, dosage and administration of propofol are tailored to achieve the desired effects, ranging from sedation to general anesthesia. Induction of general anesthesia is limited to providers certified in this specialty. However, specially trained nurses may administer propofol during a variety of procedures, including dental surgeries and endoscopies.
When seeking solely to achieve sedation, standard protocols include injection of a bolus dose of propofol followed by continuous infusion, or repeated boluses as needed. Slow injection of this medication is strongly recommended, as rapid administration may cause apnea, airway obstruction, oxygen desaturation, and/or hypotension.
Because propofol has no analgesic properties, concurrent opioid administration may be required to suitably diminish the perception and physiologic response to procedural-related pain. Sedative effects of opioids, as well as the patient's physical condition and response to sedation, must be taken into account when tailoring the administered dose of this medication. The medication dosage should be titrated to achieve the desired effect.2
Special considerations
Aside from its rapid onset and rapid recovery time, propofol is euphorigenic, meaning it can induce a sense of euphoria without the residual psychotic effects of other anesthetic induction agents such as ketamine.5 Because of the associated euphoria, patients often awaken from propofol-based anesthesia feeling pleasant and at ease.
Propofol also has antiemetic properties, although the mechanism for this action is unknown.5 With concomitant administration of opioids, well-known for their potential to induce nausea and vomiting, the antiemetic properties of propofol are a significant benefit.
Clinical pharmacology
Propofol is a white, lipid-based, oil-in-water emulsion. Because it's highly lipophilic (i.e., having an affinity for fat) and distributes rapidly into the central nervous system (CNS), the onset of action is rapid, and the duration of the effects of one single dose are brief, usually ranging from 10 to 15 minutes.6 Unconsciousness sets in within the time it takes for the medication to travel from the injection site to the brain; this is referred to as one "arm-brain circulation time."6 Generally, the onset time for propofol is 40 seconds, although time to peak effect may take up to 2 minutes.2
Propofol enhances the activity of gamma-aminobutyric acid (GABA) in the CNS.5 Within the CNS, the amino acid GABA is a key inhibitor of neurotransmission.5 Thus, as propofol potentiates GABA's effects, CNS neurotransmission decreases, and the end result is unconsciousness.
While propofol induces both unconsciousness and amnesia, this medication has no analgesic properties. Although the patient may not recall feeling pain, he still may exhibit a physiologic response to the stress of painful stimuli. For this reason, opioids also should be used to attenuate painful stimuli when indicated.
Metabolization of propofol is rapid and occurs mainly in the liver. Metabolites are produced by the liver and excreted by the kidneys.2
Adverse effects
Propofol causes vasodilation with a subsequent decrease in systemic vascular resistance. Likewise, because it's both a negative inotrope (causing the heart to pump less forcefully) and a negative chronotrope (causing the heart rate to decrease), propofol can cause a decrease in cardiac output.6 The combined impact on systemic vascular resistance and cardiac output often manifests through hypotension. In particular, a decrease in blood pressure may be seen immediately after administration of the anesthetic induction dose. The respiratory and cardiovascular effects of propofol usually are dose-dependent. To avoid adverse events, administration of this medication should be titrated to achieve the desired effect. Elderly and debilitated patients are at increased risk for adverse reactions to propofol.
Generally, hypotension and cardiovascular depression can be resolved through discontinuation of propofol, followed by the administration of I.V. fluids and vasopressors as needed.2
Advantages and disadvantages
Ideal properties of an I.V. anesthetic induction agent include rapid onset of action, rapid recovery from the drug's effects, and minimal depression of cardiorespiratory function. While propofol offers rapid onset and recovery, this medication may cause both respiratory and cardiac depression.
Potential airway compromise, ranging from decreased respiratory rate to apnea, is a major concern. Available emergency equipment should include devices needed to maintain a patent airway (e.g., oral airways, bag-valve mask devices, intubation supplies, suction equipment), as well as all supplies and medications required in the event that circulatory resuscitation becomes necessary.3 Vasopressors should be immediately available for use in treatment of hypotension. Additionally, medications offering a positive chronotropic effect (such as atropine and glycopyrrolate) should be immediately available for use in treating symptomatic bradycardia related to the effects of propofol.
While relatively minor in comparison to cardiorespiratory concerns, another drawback of propofol use is pain during administration. Patients may describe sensations ranging from mild burning to severe aching at the infusion site. Infusion-related pain may be decreased by using the larger veins of the forearm or antecubital fossa, and by the concomitant administration of I.V. lidocaine infusion.4
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