Vol. 17 •Issue 26 • Page 5
Tips on Practice
Procedural Sedation Replaces Conscious Sedation
The term “conscious sedation” has been used extensively in the past for patients who were sedated and given analgesia during a painful procedure. The drugs were administered so the patients could tolerate the procedures without having their breathing “knocked out.”
Conscious sedation eventually was replaced by the new term, “procedural sedation.” This probably happened because the term “conscious sedation” sounds like an oxymoron.
Sedation and Analgesia
Procedural sedation commonly requires the use of a sedative (to calm the nerves so the patient does not freak out and go ballistic at the sight of big needles, etc.), and something for pain (an analgesic).
Either of these drugs, even used alone, can cause respiratory depression if not administered carefully. A cocktail of both a sedative and an analgesic together must be given very carefully when a patient is not intubated and receiving supported ventilation.
The safest and most practical way to monitor for respiratory depression during procedural sedation is with a capnograph monitoring instrument that measures exhaled end tidal CO2 (ETCO2) levels. A microstream capnograph monitor can be used with the patient wearing a nasal cannula or an oral-nasal device that can deliver oxygen and continuously aspirate and analyze ETCO2.
The capnograpgh displays a breath-by-breath wave form of the CO2 level in mmHg, and the total respiratory rate. An end-tidal CO2 of greater than 50 mmHg is a sensitive, early and reliable indicator of respiratory depression. With normal lungs, the ETCO2 correlates well with the arterial PaCO2.
A pulse oximeter is also used during procedural sedation to measure the oxygen saturation (SpO2). An SpO2 of less than 90 percent is another criteria that can be used to indicate respiratory depression. Pulse oximetry is not an early enough indicator of respiratory depression, however. By the time the SpO2 is less than 90 percent, the CO2 level is significantly elevated. With oxygen administration, the point that the SpO2 drops below 90 percent can be significantly delayed. This is why there is sometimes reluctance to administer oxygen during procedural sedation.
A final indication of respiratory depression is when any manipulation is needed to adjust or open the airway.
Sedation & Analgesia
Opioid analgesics can be very potent CNS depressants. Any level of breathlessness or pain can be relieved with sufficient opioid drug. Many people do not know it, but opioids also lower oxygen consumption. On the other hand, too much narcotic analgesic can cause respiratory and cardiovascular depression and possible death. Excessively elevated CO2 (narcosis) can be a strong central nervous system depressant, which progressively depresses the vegas nerve and leads to bradycardia.
That condition is a latent sign of elevated CO2. Fortunately, with rapid rescue of depressed breathing, the bradycardia usually resolves.
Some of the common drugs used for procedural sedation include morphine, Fentanyl, Valium, versed, chlorohydrate, methohexital, Pentothal, Ketamine, Demerol, and Propofol. Fortunately, there are also reversal agents for some of these drugs, including Narcan, Revex, and Romazicon.
The ASA recognizes the four following levels of sedation.
Minimal Sedation (anxiolysis): Responsive to verbal commands. Cognition may be impaired but the cardiopulmonary system is unaffected.
Moderate Sedation/Analgesia: Responsive to verbal commands, either alone or with tactile stimulation. No airway interventions needed. Spontaneous ventilation is adequate and the cardiovascular system is maintained.
Deep Sedation/Analgesia: Not easily aroused, but responds purposefully with repeated or painful stimulus. Assistance is needed maintaining airway and adequate ventilation, but the cardiovascular system is OK (if CO2 is not too elevated).
General Anesthesia: Loss of consciousness with a need for ventilatory assistance and possible cardiovascular support.
Examples of procedures that often require sedation are: central line placement, bronchoscopy, endoscopy, thoracentesis, wound debridement, bone resetting, tooth extraction, and lumbar puncture.
Non-invasive monitors are used during procedural sedation to help collect vital sign measurements, approximately every two minutes. Additionally, the team also makes visual observation of the patient using a scale similar to those listed below3.
• Responds to name: 5
• Lethargic response to name: 4
• Responds to name with loud noise: 3
• Responds only after mild prodding or shaking: 2
• Does not respond to mild prodding or shaking: 1
Procedural sedation is used on patients of all ages and all over the hospital, as well as in outpatient clinics. Many professional organizations, including the American Society of Anesthesiologists (ASA), the American Academy of Pediatrics (AAP), the American College of Emergency Physicians (ACEP), and the American Academy of Pediatric Dentists (AAPD) have published sedation guidelines. The Joint Commission for Accreditation of Healthcare Organizations (JCAHO) now recommends that accredited hospitals follow the ASA guidelines. For RCPs, this means more job security because we are the technical experts for applying and monitoring the capnograph for airway management and for mechanical ventilation. What’s more, the correct interpretation of various different ETCO2 waveforms, as well as setting up the capnograph monitor and troubleshooting any problems requires technical expertise that RCPs already posses. With an RCP involved, sufficient sedation and analgesia can be provided without having to “call for help” if there is “a problem with the CO2 monitor” or if intubation and mechanical ventilation is needed. The RCP should be thoroughly familiar with the drugs used during procedural sedation. In some states, RCPs are authorized (under direct physician guidance) to administer sedation drugs.
• For references see our web site at www.advanceweb.comRCP
Michael Hahn is a California practitioner.