Anesthesia in the “Forward” Environment
Kenneth T. Furukawa, M.D. Lieutenant Colonel U.S. Army 41st Combat Support Hospital
Topics
• • • • • • Define forward anesthesia Identify basic techniques Discuss regional anesthetic techniques Discuss general anesthetic techniques Discuss role in resuscitation Demonstrate U.S. deployable anesthetic devices
What is “forward”?
• Any field environment. • Any place you cannot get usual medical supplies and support. • This is very subjective.
What is anesthesia?
• Rendering patient insensate to pain and unpleasant sensations related to medical procedures.
– Analgesia – Akinesia – Amnesia +/-
Techniques of Anesthesia
• • • • Local anesthesia Regional anesthesia Sedation General Anesthesia
Local Anesthesia
• Advantages
– familiar techniques – regular medications and supplies – essentially no systemic side effects except large doses of local anesthetics
• Disadvantages
– relatively labor intensive – no effect beyond surgical site – usually short duration
Local Anesthesia
• Techniques
– Cold temperature
• topical application of ice or refrigerant • immersion
– Local anesthetic application
• topical solutions • infiltration/injection
Topical Local Anesthesia
• Anesthetic agents
– – – – – – cocaine* or lidocaine 4% solution lidocaine 10% solution lidocaine 2% viscous, jelly, solution benzocaine spray tetracaine solution “EMLA” cream
• *excellent vasoconstrictor
Topical Local Anesthesia
• Airway
– – – – nasopharynx oropharynx/hypopharynx glossopharyngeal nerve laryngeal bronchial tree
Local Anesthesia
• Injection
– common use are lidocaine, procaine, bupivacaine, mepivacaine +/- vasoconstrictor – pH buffering with NaHCO3 may speed onset and reduce pain with injection – limited to total dosages over short time periods – injection distorts tissues – discomfort with injections and tissue manipulation, set-up time lag
Local Anesthesia
• Injection technique
– anesthetic must block multiple sites
epidermis
dermis
fascia
Local Anesthesia
• Airway
– – – – Mask, endotracheal tubes and laryngoscope Ventilation apparatus Oxygen source Suction
• Anesthetic agent delivery
– Medications, syringes and needles
• Monitoring
Regional Anesthesia
• Use of agent to block pain transmission and may result in temporary akinesia
– acupuncture or pressure techniques – local anesthetic solution injection
• peripheral nerve bundles • neuraxial injection
Regional Anesthesia
• Advantages
– Limits effects to region affected
• Spares effects on cardiovascular, pulmonary, central nervous systems. • Reduces CNS and pulmonary recovery time. • Improved monitoring with no or light sedation.
– Provides excellent akinesia and muscle relaxation of affected region – May reduce blood loss with some operations
Regional Anesthesia
• Disadvantages
– Does not provide analgesia or akinesis to other areas. – Amnesia is not assured in most cases. – Encourages blood pooling and transient central blood volume depletion (especially neuraxial). – Incomplete blocks or slow onset occur. – Usually limited due to agent duration or patient tolerance.
Regional Anesthesia
• Airway
– sphenopalatine ganglion (CN V) – superior laryngeal nerve (CN X) – glossopharyngeal nerve (CN IX)
Regional Anesthesia
• Neck
– Cervical plexus block* C2-C5 dermatomes
• deep • superficial
– Cervical epidural C2-T2 dermatomes
• continuous technique with catheter allows re-dose
• *Unilateral
Regional Anesthesia
• Thorax
– Intercostal nerve blocks (rib blocks)*
• risk of pneumothorax • largest vascular uptake of any regional block
– Interpleural nerve blocks* – Thoracic epidural
• continuous catheter technique allows re-dose • “band” of anesthesia • sympathectomy is remarkable
Regional Anesthesia
• Lumbar/sacral
– Lumbar plexus block* – Epidural (peri-dural) – Subarachnoid block (spinal)
• can be somewhat controlled for distribution • ALL above result in sympathectomy
– Caudal – These can be single dose or catheter technique
Regional Anesthesia
• Upper extremity
– Brachial plexus
• multiple approaches
– – – – –
Radial nerve Ulnar nerve Median nerve Wrist block Digital block
Supraclavicular Interscalene
Axillary
Intraclavicular
Regional Anesthesia
• Lower extremity
– – – – – – Sciatic nerve Femoral nerve Obturator nerve Popliteal fossa (tibial nerve) Ankle block Digital block
Regional Anesthesia
• Airway
– – – – Mask, endotracheal tubes and laryngoscope Ventilation apparatus Oxygen source Suction
• Anesthetic agent delivery
– Medications, syringes and needles – Catheters and special trays
• Monitoring
Sedation
• Providing limited analgesia and amnesia without impeding normal ability to maintain an airway and respiratory pattern.
– Part of the spectrum leading to general anesthesia. – Unable to provide primary analgesia. – Risks compromising the airway and breathing. – No set dose or regimen is absolutely SAFE.
Sedation
• Component ingredients
– Hypnotic (+/- amnestic)
• Propofol • Barbiturate • Benzodiazepine
– Analgesic
• Opiate • Ketamine
Sedation
• Hypnotics and opiates are synergistic in their combined effect to depress respiratory drives. • Doses required to prevent patient movement will usually depress airway protective reflexes.
– Local or regional analgesia is usually required.
• Proper monitoring is essential.
Sedation
• Airway
– – – – Mask, endotracheal tubes and laryngoscope Ventilation apparatus Oxygen source Suction
• Anesthetic agent delivery
– Medications, syringes and needles
• Monitoring
General Anesthesia
• Deep enough sedation to ensure akinesia. • Multiple techniques
– Intravenous using at least two agents
• Hypnotics (propofol, barbiturates, benzodiazepines) • Analgesics (opiates, NSAID) • Neuromuscular blocker and other adjuvant agents as needed.
– Inhaled anesthetics
• Potent inhaled anesthetic agents (isoflurane) • Adjuvant agents (nitrous oxide)
General Anesthesia
• Requires additional monitoring
– – – – – Airway management Assess adequacy of ventilation and oxygenation Frequent attention for cardiovascular effects Be aware of neurologic effects of positioning Be aware of heat loss or gain
General Anesthesia
• Airway
– – – – Mask, endotracheal tubes and laryngoscope Ventilation apparatus Oxygen source Suction
• Anesthetic agent delivery
– Medications, syringes and needles – Gas/vapor delivery device
• Monitoring
General Anesthesia
• Devices
– Ohmeda 885A
• • • • • • Compressed oxygen required Oxygen flow measured vaporizing device Delivers nitrous oxide Semi-closed or closed rebreathing circuit Ventilator adaptable Relatively lightweight and portable
General Anesthesia
• Devices
– Ohmeda PAC
• • • • • • Drawover vaporizer design Oxygen supplementation suggested Not currently adaptable for most ventilators Does not deliver other gases Semi-open breathing circuit Very lightweight and portable
Resuscitation
• Major role in trauma care is continued resuscitation with judicious anesthesia.
– Airway management – Circulatory support
• Access • Fluids and blood • Medications
– Appropriate application of anesthesia