Contrast Media in Medical Imaging

Contrast Media in Radiography and Medical Imaging

• This lecture covers anxiety, phobia, and conscious sedation in medical imaging.
• The goal of sedation and analgesia is to improve patient experience by reducing negative procedure effects and optimizing patient outcomes.
• Radiological procedures can cause pain, anxiety, psychological, and physical distress.

Definitions

• Anxiety: An overwhelming sense of apprehension and fear, often marked by physical signs like tension, sweating, and increased pulse rate. This includes doubts about one's capacity to cope with the perceived threat.
• Phobia: An exaggerated, usually inexplicable, and illogical fear of a particular object, class of objects, or situation.
• Sedation: Suppresses the central nervous system to a lesser degree, inhibiting anxiety and long-term memory creation without unconsciousness. It can also be a state of reduced irritability, agitation, or depressed consciousness for medical or diagnostic procedures.
• Conscious Sedation: An induced state of sedation where consciousness is minimally depressed. The patient can independently maintain their airway, retain protective reflexes, and respond to verbal and physical stimuli.
• Analgesic (painkiller): An agent that reduces pain sensation without loss of consciousness; used to relieve pain.

Conscious Sedation and Analgesics

• Many conscious sedation drugs are common in children and adults, but dosages can vary.
• Administration methods include intravenous (adults), oral, intranasal, intramuscular, intravenous, and rectal (paediatrics).

Levels of Sedation

• There are different levels of sedation that affect patients' responsiveness, airway management needs, spontaneous ventilation, cardiovascular stability. The various levels include minimal (anxiolytic), moderate sedations, deep sedation, and general anesthesia.

Categories of Agents

• Analgesics:
  • Opiates (e.g., morphine, pethidine, codeine)
  • Non-opiate (e.g., paracetamol, NSAIDs)
  • Others (e.g., nitrous oxide)
• Sedatives:
  • Benzodiazepines (e.g., midazolam, diazepam)
  • Barbiturates (replaced by benzodiazepines due to side effects)
  • Propofol (an anesthetic only drug)
  • Ketamine (an anesthetic only drug)

Agents Used for Conscious Sedation - Benzodiazepines

• Benzodiazepines are psychoactive drugs affecting nervous system function. They can alter perception, mood, consciousness, cognition, and behavior.
• Benzodiazepines are used as sedatives, hypnotics, anxiolytics, anticonvulsants, and have muscle relaxant properties.
• Examples include midazolam and diazepam (Valium).

Agents Used for Conscious Sedation - Barbiturates

• Barbiturates are central nervous system depressants, used as anxiolytics, hypnotics, and anticonvulsants.
• They are replaced by benzodiazepines due to side effects including physical and psychological addiction, overdose potential, and placental/breast milk transmission.

Agents Used for Conscious Sedation - Propofol

• Propofol is a short-acting intravenous medication that decreases consciousness and causes memory loss.
• It is used for initiating and maintaining general anesthesia, sedation in mechanically ventilated adults, and procedural sedation.
• Side effects include irregular heart rate, low blood pressure, injection site burning, cessation of breathing, seizures, and infections (due to misuse) and addiction.

Reversal Agents

• Reversal agents stabilize the effects of sedatives and analgesics.
• Safe sedation practices minimize the need for reversal drugs.
• A clear reversal protocol is necessary and should be available where sedation/analgesia is used.
• Crucial for emergency situations.

Reversal Agents Examples

• Naloxone: Reverses opioid effects. Essential for managing opioid overdoses and respiratory distress.
• Flumazenil: Stabilizes benzodiazepine effects and quickly reverses benzodiazepine-induced respiratory depression.

Key Points for Sedation and Analgesia in Medical Imaging Departments

• Safe and effective sedation and analgesia is essential for many radiological procedures.
• Appropriately trained staff should administer sedation.
• Patients needing sedation should have pre-procedure assessments and plans.

Key Points for Sedation - Medical Imaging Departments

• A WHO checklist is used for each sedated patient.
• Appropriate monitoring of sedated patients is needed.
• Resuscitation equipment and reversal agents are essential and readily available.
• A properly staffed recovery area with communication is needed.
• Sedation-related complications are recorded.
• Regular audits of practice are performed.
• A multidisciplinary sedation committee exists for sedation and analgesia administration in each institution.

Equipment

• Resuscitation/emergency cart, defibrillator, intubation and ventilation equipment, and oxygen supplies.
• Airway maintenance equipment (e.g., nasal cannula, face masks, oral airways, endotracheal tubes, laryngeal mask airways, laryngoscopes, Ambubag).
• Continuous suction equipment, suction catheters, and monitoring equipment (pulse oximetry, blood pressure, heart rate, cardiac rhythm, respiratory rate).
• Pressure-related and position-related injury prevention equipment (e.g., straps, gel pads).
• MRI-appropriate equipment for sedation in MRI scanners.