MANAGEMENT OF WASTE ANESTHESIA GAS NO DISCLOSURES

Transcription

1 MANAGEMENT OF WASTE ANESTHESIA GAS NO DISCLOSURES Michael C. Tan, MD, MPH Perioperative Care Conference - Thursday, April 6, 2017 ANESTHESIA GASES Generic or chemical name Commercial name Year of introduction Currently in use? Diethyl ether Ether 1842 No Nitrous oxide Nitrous oxide 1844 Yes Chloroform Chloroform 1847 No Cyclopropane Cyclopropan e 1933 No Trichloroethylene Trilene 1934 No Fluroxene Fluoromar 1954 No Halothane Fluothane 1956 No Methoxyflurane Penthrane 1960 Infrequently Enflurane Ethrane 1974 Yes Isoflurane Forane 1980 Yes Desflurane Suprane 1992 Yes Sevoflurane Ultane 1995 Yes

2 NITROUS OXIDE Sweet smelling, combustible gas of low potency Associated with post-op NV Inactivates vitamin B12 Effects embryonic development (in vitro) Pregnancy risk category C DESFLURANE SEVOFLURANE Pungent volatile, results in coughing, salivation, laryngospasm Degrades to form carbon monoxide Pregnancy risk category B Minimal odor, non-pungent, potent bronchodilator Candidate inhalational induction agent Breaks down to compound A, which is a dose-dependent nephrotoxin in rats Not been associated with renal injury in humans Pregnancy risk category B

3 WAG HEALTH EFFECTS N2O HAZARDS Acutely (high concentration exposure) - light headedness, nausea, fatigue, headache, irritability, depression, impaired cognitive and motor skills Chronically (low concentration exposure) - birth defects, miscarriage, cancer (?) Women who worked with N2O at least 3 hours per week in offices not using scavenging equipment had an increased risk of spontaneous abortion (relative risk = 2.6, 95% confidence interval [CI] = ) adjusted for age, smoking, and number of amalgams prepared per week. This finding was not observed among workers in offices where scavenging equipment was in use. The authors concluded, "Scavenging equipment can make large differences in exposure levels at moderate cost and appears to be important in protecting the reproductive health of women who work with nitrous oxide. (Rowland et al 1995) HEALTH RISKS IN PREOPERATIVE PRACTITIONERS Female anesthesiologists and preoperative providers have increased risk of miscarriage and birth defects (Shirangi 2009, Bolvin 1997) All cause mortality ratio, cancer, and heart disease between anesthesiologist (N= 40,242) and internists (N= 40,211) was the same. (Alexander 2000) No definitive risk or causal effect established between anesthetic gas and cancer (Sukhminder 2015) WAG EXPOSURE Leaks in the anesthesia closed system (breathing circuit, scavenging system) WAG can escape from open system (eg dental practices) WAG can result from a poor fitting mask WAG can escape from around patient s ETT or LMA if cuff is not properly inflated Patient exhalation during and after emergence

4 WHO IS AT RISK? RECOMMENDED EXPOSURE LIMITS (REL) Operating room personnel Anesthesiologists, nurse anesthetists, OR nurses and technicians, surgeons, ancillary staff Post-anesthesia care unit nurses and staff Dental practitioners 2 ppm for halogenated gases 25 ppm for N2O Newer halogenated gases (desflurane, sevoflurane) not extensively studied No defined safe limit of exposure (Occupational Saftey and Health Administration) MEASURES TO DECREASE WAG ENGINEERING CONTROL 1 Engineering controls Work practices Air monitoring Hazard communication and training (National Institute of Occupational Safety and Health) A well designed scavenging system to properly dispose of the gases Room ventilation to ensure air exchange in surgical suites is able to ventilate any WAG that escapes the patient circuit Ensure no object block the ventilation in the surgical suite Scavenger system should be independent of the hospital ventilation system In event of a Code Red, hospital ventilation can be shut down WAG collection canister to collect WAG before it reaches the scavenger

5 ENGINEERING CONTROL II Properly designed equipment WAG scavenging system is the primary line of defense against exposure, however, a properly designed HVAC system can help dilute and remove WAGs not collected by the scavenger Use airway gas monitor that is connected to the anesthetic breathing circuit (routine) Proper maintenance and inspection programs Use of anesthetic agent supplied bottles with integrated fused filling adaptor REDUCING WASTE ANESTHETIC GASES IN AMBIENT AIR Operating rooms, delivery rooms, and other hospital locations where surgery and anesthesia services are provided should conform to the guidelines established by the American Institute of Architects, which identify the standard of a minimum of air exchanges per hour for existing hospitals and medical facilities. PACU air exchanges should have a total of 6 air exchanges per hour with minimum of 2 air changes of outdoor air per hour (OSHA)

6 WORK PRACTICES Use low flow anesthesia when appropriate Properly sized and fitted face mask Sufficiently inflate the tracheal tube or laryngeal mask airway cuff Properly connect tubes and fittings for anesthesia machine Make sure scavenging system is active before turning on the anesthetic gas Remember to turn the gas off when the mask is removed from the patient MONITORING AIR QUALITY COMMUNICATION AND TRAINING Continuous or periodic monitoring adequately measure exposure in the work areas Monitoring can aid in identifying the presence and location of leaked gases Most modern WAGs cannot be detected by smell and can only be detected by WAG monitor Employers should develop written hazard communication program regarding WAGs, its health hazards, labeling of canisters, tanks, containers, and comprehensive employee training and information program Training program should list steps workers can take to protect themselves from the hazards of WAGs Spills of anesthetic agents should be treated as emergencies and must only be cleaned up and controlled by trained and equipped personnel

7 WAG SPILL NOVEL APPROACHES Large volume spills (>=1 bottle) use spill pillows (polypropylene), vermiculite, carbon based sorbents Also, use suctioning to clear liquid volatile anesthetic agent WAG scavenging mask in the PACU PATIENT BREATHING ZONE 8 inches from patient s mouth Pilot study used IR spectrophotometer and observed 20 PACU patients High flow O2 (> 8 L/min) dilutes WAG concentration (Hiller 2015) SUMMARY Anesthesia gases have been associated with increase risk of miscarriages but no definitive cause and effect has been shown Exposure to WAG and its risks can be reduced by adhering to NIOSH/OSHA recommendations Limit exposure to patient breathing zone Use high flow O2 to dissipate exhaled WAG Novel approaches such as a mask with active scavenging system may be beneficial

8 Q & A PERIOPERATIVE CASE SCENARIO I A 72 y/o F s/p shoulder arthroscopy comes to the PACU complaining of progressively worsening shortness of breath Pmhx include HTN, CAD s/p CABG, DVTs, Patient received a single shot inter-scalene block preoperatively Stable intraoperatively and uneventful anesthetic course DIFFERENTIAL DIAGNOSIS Acute MI/Heart failure Pulmonary embolism Infectious/Pneumonia Phrenic nerve palsy

9 PHRENIC NERVE PALSY CASE SCENARIO II Near 100% of patients receiving interscalene block will have ipsilateral phrenic nerve paralysis Patients with moderate to severe COPD, interscalene block is contraindicated Supportive therapy, O2 supplement, and intubation if encountering severe respiratory distress Resolution of symptoms should occur within hours post-op A 23 y/o has been complaining of bilateral hands and feet tingling and numbness, associated with an unsteady gait for the past 1-2 month span She is chronically fatigued, depressed, and experiencing decreased ability to concentrate She is your colleague at the dental office (Qiu, 2017) CASE SCENARIO II N2O TOXICITY She reports having regularly inhaled laughing gas nitrous oxide (N2O) for the past 6 months, starting with 1 canister once a week and gradually increasing numbers canisters daily for the past 2 months. Work up shows macrocytic anemia and decreased B12 levels N2O converts vit B12 from active monovalent form to the inactive bivalent form Vit B12 deficiency causes myelinolysis and macrocytic anemia Myelinolysis results in subset combined degeneration of the spinal cord Neurotoxic effects of N2O include polyneuropathy, ataxia, and psychosis

10 N2O TOXICITY TREATMENT Vit B12 supplementation N2O toxicity often are reversible with abstinence and B12 supplementation This patient had complete resolution of her neuropathy, depression, and chronic fatigue at 2 month follow up