Carbon Monoxide in the Anesthesia Circuit
Definition
Carbon monoxide present in the anesthesia breathing circuit
Etiology
Carbon monoxide is produced by degradation of volatile anesthetic agents in the presence of desiccated CO 2 absorbents
The amount of carbon monoxide produced depends upon the degree of desiccation, temperature in the breathing circuit, volatile anesthetic concentration, and fresh gas flow
Production is greatest with absorbents containing strong bases (e.g., KOH > NaOH)
Production is greatest with desflurane and isoflurane but has also been reported with sevoflurane
CO 2 absorbent desiccation is typically caused by fresh gas flow into circle system of anesthesia workstation allowing CO 2 absorbent drying (e.g., fresh gas flow left on overnight)
Typical Situations
After period of anesthesia workstation nonuse (e.g., over a weekend)
Prevention
Use CO 2 absorbents whose composition does not facilitate significant volatile anesthetic degradation
Awareness of the potential for carbon monoxide production if a machine has not been used for some time
Develop institutional, hospital, and/or departmental policies regarding steps to prevent desiccation of the CO 2 absorbent, such as
Turn off all gas flow when the workstation is not in use
Change the absorbent regularly
Change absorbent whenever the color change indicates exhaustion
Change all absorbent (both cartridges in a two cartridge system)
Change absorbent when uncertain of the state of hydration
If compact canisters are used, consider changing them more frequently
Place a date on the canister when it is changed
If available, monitor patient using a multiwavelength pulse oximeter capable of continuously measuring carboxyhemoglobin
Manifestations
Moderate decrease in O 2 saturation
Unexpectedly rapid change of absorbent indicator color after anesthesia induction
Unusually high temperature of absorbent canister
On emergence from anesthesia, unexplained confusion, nausea, dyspnea, headaches, blurred vision, and dizziness
Similar Events
Emergence delirium after general anesthesia (see Event 55, Postoperative Alteration in Mental Status )
Hypoxemia (see Event 10, Hypoxemia )
Hypercarbia (see Event 32, Hypercarbia )
MH (see Event 45, Malignant Hyperthermia )
Management
Use high fresh gas flow to purge carbon monoxide from breathing circuit
Confirm diagnosis
Draw an arterial blood sample for co-oximetry analysis, looking for elevated carboxyhemoglobin (COHb)
Ventilate lungs with 100% O 2 to decrease the half-life of COHb
Patient may require mechanical ventilation until COHb has fallen to safe levels
Replace absorbent with fresh absorbent
Complications
Hypoxemia
Nausea, vomiting, severe headache, syncope
Coma, convulsions
Myocardial ischemia
Neuropsychologic abnormalities
Cardiac arrest
Suggested Reading
Circle System Expiratory Valve Stuck Closed
Definition
The expiratory valve of a circle system is “stuck closed” when the valve does not open properly during expiration, thus preventing exhalation of gas from the lungs
Etiology
Valve components are misassembled
Extra parts or foreign bodies are present in the valve assembly
Dirt, blood, moisture, or secretions contaminating the valve assembly
Typical Situations
After cleaning or reassembly of the valve
Prevention
Ensure that only trained individuals assemble and maintain the valve systems
Conduct a thorough preuse check of the circle system and the unidirectional valves
Check for normal appearance of the valve assembly
Check that the valve disk moves appropriately when breathing from the circuit or when ventilating a “test lung” (reservoir bag)
Check breathing circuit pressure at end-expiration during mechanical ventilation of the test lung
With a standing bellows ventilator, the pressure should be 2 to 3 cm H 2 O
With a piston or hanging bellows ventilator, the pressure should be zero
An automated machine check would probably not detect this problem
Manifestations
Progressive increase in PIP and PEEP
The increase in PIP may plateau at a high value owing to the performance envelope of the ventilator and to gas escaping through a high-pressure relief valve during inspiration
The continuing pressure alarm will sound after 15 seconds if pressure limit is set appropriately
Hypotension secondary to increased intrathoracic pressure and impaired venous return
Delayed or diminished response to injected vasoactive medications and fluids
They may not reach the arterial circulation because of impeded venous return
Increasing difficulty in ventilating the patient’s lungs due to apparent low total thoracic compliance (i.e., “stiff lungs”)
Decreased or absent ET CO 2
Decreased O 2 saturation
Pulmonary barotrauma
Pneumothorax
Pneumomediastinum
SC emphysema
Similar Events
Kinked or obstructed ETT or breathing circuit hose (see Event 7, High Peak Inspiratory Pressure )
Obstruction of the WAGD system (see Event 73, Waste Anesthesia Gas Disposal System Malfunction )
Bronchospasm (see Event 29, Bronchospasm )
Pneumothorax from other causes (see Event 35, Pneumothorax )
Management
Disconnect the patient from the anesthesia breathing circuit to relieve high intrathoracic pressure
Use an alternative system to ventilate the lungs (e.g., self-inflating bag or a nonrebreathing system)
If total thoracic compliance is still low (e.g., “stiff lungs” or tension pneumothorax), the problem is in the patient, not the breathing circuit (see Event 7, High Peak Inspiratory Pressure )
If the circle system must be used
Reduce the fresh gas flow into the circuit
Ventilate the lungs manually, disconnecting the patient from the breathing circuit as often as necessary to relieve the excess pressure
Attempt to relieve the obstruction
Tap the valve dome
Remove the expiratory valve disk
Increase the fresh gas flow to minimize rebreathing of CO 2
Ventilate the lungs
Repair or replace the expiratory valve or valve-CO 2 absorber assembly
Complications
Hypotension
Pneumothorax
Following relief of the high intrathoracic pressure
Hypertension and tachycardia due to relief of the venous obstruction and accumulated doses of vasoactive drugs reaching the arterial circulation
Suggested Reading
Circle System Inspiratory Valve Stuck Closed
Definition
The inspiratory valve of a circle system is “stuck closed” when it does not open properly during inspiration, thus preventing ventilation of the lungs.
Etiology
Valve components are misassembled
Extra parts or foreign bodies are present in the valve assembly
Dirt, blood, moisture, or secretions contaminating the valve assembly
Typical Situations
After cleaning or reassembly of the valve
Prevention
Ensure that only trained individuals assemble and maintain the valve systems
Conduct a thorough preuse check of the circle system and the unidirectional valves
Automated check of the newer anesthesia workstations should detect this fault
Check for normal appearance of the valve assembly
Check that the valve disk moves appropriately when breathing from the circuit or when ventilating a “test lung” (reservoir bag)
Check that PIP is normal during ventilation of the test lung and that there is appropriate flow of gas into the test lung during inspiration
Manifestations
Markedly increased PIP
The high-pressure alarm may sound
Most anesthesia workstations have a default setting of 40 cm H 2 O
Apparent low total thoracic/pulmonary compliance
The reservoir bag feels “stiff” during manual ventilation
Diminished or absent breath sounds
Decreased expired minute volume
Absent or decreased ET CO 2
Increased arterial PaCO 2
Hypoxemia
Similar Events
Kinked or obstructed ETT or breathing circuit hose (see Event 7, High Peak Inspiratory Pressure )
Obstruction of the WAGD system (see Event 73, Waste Anesthesia Gas Disposal System Malfunction )
Bronchospasm (see Event 29, Bronchospasm )
Pneumothorax (see Event 35, Pneumothorax )
Endobronchial intubation (see Event 30, Endobronchial Intubation )
Management
Use an alternative system to ventilate the lungs (e.g., self-inflating bag or a nonrebreathing system)
Maintain oxygenation and ventilation
Convert to an IV anesthetic if necessary
To diagnose the obstruction in the inspiratory limb of the circle system
Disconnect the patient from the anesthesia breathing circuit at the Y piece and activate the O 2 flush
If the breathing circuit pressure rises dramatically but there is no gas flow from the circuit, the inspiratory limb is obstructed
Inspect the valve assembly
If the circle system must be used
Remove the disk from the inspiratory valve, effectively leaving the valve stuck open
Maximize the fresh gas flow to minimize rebreathing
Ventilate the patient’s lungs
Complications
Hypoventilation
Hypoxemia
Hypercarbia
Suggested Reading
Circle System Valve Stuck Open
Definition
A valve in the circle system is “stuck open” when it does not fully occlude the inspiratory or expiratory limb, thereby permitting rebreathing of exhaled gases containing CO 2 .
Etiology
The valve disk or valve ring is broken or deformed
Valve components are misassembled or missing
Extra parts or foreign bodies are present in the valve assembly
Dirt, blood, moisture, or secretions contaminating the valve assembly
Typical Situations
After cleaning or reassembly of the valve
Long-duration cases with humidification
Prevention
Ensure that only trained individuals assemble and maintain the valve systems
Conduct an appropriate preuse check of the circle system and the one-way valves
Check for normal appearance of the valve assembly
Check that the valve disks move appropriately when breathing from the circuit or when ventilating a “test lung” (reservoir bag)
Check for agreement between the tidal volume set on the ventilator and the volumes delivered and exhaled from the test lung
An automated machine check would most likely not detect this problem
Manifestations
Increased inspiratory CO 2
This is pathognomonic for rebreathing or for exogenous administration of CO 2
Observe both the digital readout of FiCO 2 and the capnogram
FiCO 2 > 0 to 1 mm Hg
Elevated baseline of capnogram
Increased ET CO 2 and PaCO 2
Hypertension, tachycardia, and vasodilation secondary to hypercarbia
Hyperventilation in patients who are breathing spontaneously
Reverse flow alarm may be activated by a spirometer that can sense the direction of flow and is located in the limb of the incompetent valve
If the incompetent valve is in the inspiratory limb, there may be a disparity between the inspiratory movement of the ventilator bellows and the expired volumes measured by a spirometer in the expiratory limb
Similar Situations
Failure or exhaustion of the CO 2 absorbent
CO 2 absorber bypass valve accidentally left in the bypass position
CO 2 absorber out of circuit
CO 2 infused into the circuit from a pipeline supply or tank
Management
Check for CO 2 absorbent exhaustion and replace if necessary
Check that CO 2 absorber bypass valve (if present) is correctly positioned
Check that the CO 2 absorber (disposable cartridge) is in the circuit
Use an alternative system to ventilate the lungs (e.g., self-inflating bag or a nonrebreathing system) if the ET CO 2 or PaCO 2 is significantly increased or if there are systemic signs of hypercarbia
Repair or replace the valve assembly or anesthesia workstation as soon as feasible
Maintain anesthesia with IV agents
If the circle system must be used
Maximize fresh gas flow into the breathing circuit
Ventilate the patient’s lungs
Complications
Hypercarbia
Tachycardia
Hypertension
Arrhythmias
Suggested Reading
Common Gas Outlet Failure
Definition
Common (fresh) gas outlet failure is the disconnection or obstruction of the fresh gas supply between the common gas outlet of the anesthesia workstation and the anesthesia breathing circuit (many contemporary anesthesia workstations do not have a user-accessible common gas outlet).
Etiology
Disconnection of the connecting hose from the common gas outlet or the CO 2 absorber housing
Obstruction of the common gas outlet or connecting hose
Failure of the auxiliary common gas outlet present on some anesthesia workstations (e.g., GE/Datex-Ohmeda Aestiva and the GE Aisys Carestation)
Typical Situations
After the connecting hose has been disconnected from the common gas outlet so that the common gas outlet can be used as a source of O 2 or an O 2 -air mixture for delivery to a face mask or nasal cannulae
After cleaning or maintenance of the anesthesia workstation
Prevention
Use an antidisconnect device at each end of the connecting hose between the common gas outlet and the anesthesia breathing circuit
Do not connect O 2 nasal cannulae or face masks to the common gas outlet or connecting hose
Connect to a separate O 2 source
Connect to auxiliary O 2 flowmeter
Connect to the Y piece of the breathing circuit
Connect to auxiliary common gas outlet if an air/O 2 mixture is desired to avoid an O 2 enriched atmosphere
Conduct a thorough preuse check of the anesthesia workstation
Discourage nonessential activity in the vicinity of the anesthesia workstation and the anesthesia breathing circuit
Manifestations
The reservoir bag or ventilator bellows will progressively empty
In ventilators in which the bellows falls during exhalation (“hanging bellows”), the loss of gas from the circuit may not be apparent
When the O 2 flush is activated, there will be a loud sound of rushing gas but the reservoir bag or ventilator bellows will not fill
The breathing circuit low airway pressure alarm will sound
The low minute ventilation alarm may sound
Decrease in the O 2 concentration of the inspired gas
The signs of hypoventilation, hypoxemia, and hypercarbia will appear later
Similar Events
Major leak in the anesthesia circuit from other causes (see Event 69, Major Leak in the Anesthesia Breathing Circuit )
Management
Increase the fresh gas flow into the anesthesia breathing circuit
This will not compensate for the leak from a disconnection of the common gas outlet or connecting hose
Switch to the reservoir bag, close the pop-off valve, and attempt to fill the anesthesia breathing circuit by activating the O 2 flush
Activating the O 2 flush will not fill the anesthesia circuit
If the common gas outlet is obstructed, there will be no flow of gas
If the connecting hoses are disconnected, there will be a loud sound of escaping gas but the reservoir bag will not fill
Scan for an obvious disconnection or interruption of the hose between the common gas outlet and the anesthesia breathing circuit
Reconnect the hose
Check whether the auxiliary common gas outlet (present on some anesthesia workstations) has been selected
If problem persists, use an alternative system to ventilate the lungs (e.g., self-inflating bag or a nonrebreathing system)
Call for help to identify and correct the problem
If necessary, replace the anesthesia workstation if this is feasible
Maintain anesthesia with IV agents until the common gas outlet is restored
Inform biomedical engineering of the failure and have the equipment inspected
Complications
Hypoventilation
Hypercarbia
Hypoxemia
Awareness
Suggested Reading
Drug Administration Error
Definition
A drug administration error involving a syringe, ampule, or infusion pump may occur in the following ways:
Ampule swap: The incorrect drug is drawn up into a labeled syringe or infusion pump
Syringe swap: Medication from the wrong syringe is administered to the patient
Infusion pump error: Incorrect drug or drug dosage administration from an infusion pump
Etiology
Failure to label syringes or infusion pump
Incorrect labeling of syringes or infusions
Failure to read the label on the ampule, syringe, or infusion pump
Mix-up of drugs with similar names (e.g., epinephrine and ephedrine)
Mix-up of drugs with similar packaging (drugs from different vendors may look similar)
Wrong drug in storage bin
Failure to properly dilute a concentrated preparation of a drug (e.g., regular insulin)
Typical Situations
When the anesthesia professional is working in unfamiliar settings or with unfamiliar devices
When drug packaging or ampules are changed (e.g., new vendor)
When drugs are restocked
When there is time pressure or in the presence of distractions
When ampules have a similar appearance, especially if they are located close to each other in a drug cart
When syringe and infusion pump labels are written by hand
When syringes are prepared by other personnel
When it is dark in the OR or procedure room
Prevention
Check the drug name and concentration on each drug ampule carefully (ASTM standard D 6398-08)
Use drug ampules whose labels conform to ASTM standard D 5022-07
Label syringes carefully
Use preprinted, color-coded adhesive syringe labels (ASTM D 4774-11e1)
For emergency drugs, use “ready to use” syringes (ASTM D 4775-88/D 4775M-09)
Discard unlabeled syringes
Discard syringes if there is any doubt about their actual contents
Use commercially premade syringes (especially with high-potency medications requiring dilution)
Arrange drug trays to separate similar appearing or named medications
Pharmacy should notify anesthesia professionals when changing drug vendors
Use “high risk” labels for high-risk drugs (e.g., neuromuscular blockers)
Manifestations
Unusual response or lack of response to drug administration
Unusual increase or decrease in BP or HR
The awake patient may complain of an unusual sensation
Pounding heart or palpitations
Lightheadedness
Unexpected change in level of consciousness
Visual disturbance
Unexpected muscle weakness
The anesthetized patient may exhibit
Hypertension, tachycardia, hypotension, bradycardia
Unexpected occurrence or persistence of muscle relaxation
Unexpected change, or lack of change, in level of consciousness
Incorrect ampule or vial found to be open in the anesthesia professional’s work area
Similar Events
Seizures (see Event 57, Seizures )
Airway obstruction
Hypertension (see Event 8, Hypertension )
Hypotension from other causes (see Event 9, Hypotension )
Failure to awaken or breathe from other causes (see Event 56, Postoperative Failure to Breathe , and Event 55, Postoperative Alteration in Mental Status )
Anaphylaxis (see Event 16, Anaphylactic and Anaphylactoid Reactions )
Failure of the IV infusion (see Event 67, Intravenous Line Failure )
Management
If the error in drug administration is recognized immediately after injection
Stop the IV line carrying the drug
Disconnect IV tubing from IV catheter and drain IV line
If there is a BP cuff on the same arm as the IV catheter, inflate it to slow down the entry of the drug into the central circulation
Maintain the patient’s airway and ensure adequate oxygenation and ventilation
If the medication error involved administration of a muscle relaxant to an awake patient
Reassure the patient, provide sedation with a short-acting IV agent, and assess the need to place an ETT for ventilation and anesthesia
Assess neuromuscular function with a nerve stimulator and reverse neuromuscular blockade when sufficient recovery has occurred
If the medication error involved administration of a muscle relaxant to an anesthetized patient
Assess neuromuscular function with a nerve stimulator and reverse neuromuscular blockade when sufficient recovery has occurred
Maintain anesthesia until adequately reversed
If the patient is hypotensive (see Event 9, Hypotension )
Expand the circulating fluid volume rapidly
Administer a vasopressor (e.g., phenylephrine IV, 50 to 100 μg bolus)
Treat any associated bradycardia with atropine IV, 0.6 mg bolus; or glycopyrrolate IV, 0.2 to 0.4 mg bolus, repeated as necessary
If the patient is hypertensive (see Event 8, Hypertension )
Depending on the drug and dose, the hypertensive episode may resolve quickly. In particular, it is often better to wait for the effects of epinephrine (especially tachycardia) to resolve spontaneously than to treat it aggressively with β-blockade, which can lead to unopposed adrenergic effects
Administer a short-acting vasodilator (NTG IV 0.2 to 1 μg/kg/min; sodium nitroprusside IV 0.2 to 2 μg/kg/min)
Consider treating prolonged tachycardia
Esmolol IV, 0.5 mg/kg loading dose, followed by an infusion as necessary to control the HR
Labetolol IV, 5 to 20 mg, repeat as needed
Attempt to determine what drug was administered
Check infusion pumps
Check to see whether infusions are running
Check drug infusion settings and labeling
Check tubing from source to patient
Check the syringes and ampules used during the case
Check the label on the syringe just used to determine whether it was the desired one
Check to see whether one syringe has an unexpectedly low volume of drug remaining
Inspect opened ampules and vials to determine whether an incorrect medication was opened
Have the trash and “sharps” containers impounded to allow inspection of ampules, vials, and syringes at a later time
Treat any additional side effects of the medications that were administered
Complications
Awareness
Residual or prolonged neuromuscular blockade
Hypoventilation, hypoxemia, or hypercarbia
Myocardial ischemia or infarction
Cerebral ischemia
Arrhythmias
Cardiac arrest
Suggested Reading
Electrical Power Failure
Definition
Electrical power failure is loss of all or part of the electrical power supply, including the possible loss of the emergency power generation system.
Etiology
Power failure external to the hospital
Power failure internal to all or part of the hospital
Failure of an electrical circuit within the OR
Failure of the emergency power generation system or battery backup system
Typical Situations
During severe weather
During or after a fire in the hospital
Following a natural disaster (e.g., earthquake)
During or after construction within or outside the hospital
Prevention
Ensure that backup batteries in anesthesia equipment are charged and that the batteries continue to hold charge
Nickel-cadmium batteries may need to be fully discharged occasionally to maintain their ability to hold a full charge
Plug critical electrical equipment into circuits connected to the emergency power generation system (typically red colored outlets)
Test the emergency power generation system on a regular basis, and correct any faults that might prevent a rapid switchover to emergency power
Use an uninterruptible power supply (UPS) for critical pieces of equipment
Check the operating manual of each anesthesia workstation and ventilator for the need of a UPS
Some newer anesthesia workstations have a battery backup that can power the ventilator for a short time
Conduct periodic power failure drills with OR staff
Manifestations
Failure of primary and emergency electrical power
Room lights go off
All electrical equipment without a battery backup goes off
Electronically controlled or powered anesthesia workstations without battery backup will stop working
Some anesthesia ventilators are both pneumatically powered and pneumatically controlled and will continue to function
Most contemporary anesthesia ventilators are electronically controlled or electrically powered and will stop workingDelivery of anesthetic gases to the circuit may also stop
Failure of primary power only; emergency power is on
Lights and equipment go off transiently
There will be a variable time interval while emergency generators are activating and power is restored to the emergency power outlets
When switching to emergency power, microprocessor-based equipment may reset to factory defaults or lock up owing to power surge
Equipment that is not connected to an emergency power outlet will not operate
Similar Events
Localized failure of a single outlet or circuit
Failure of an individual monitor, device, or light
Tripping of a ground fault circuit interrupter (GFCI) outlet
Management
Find an emergency flashlight
A flashlight should be stored in the anesthesia cart
Many ORs have battery-powered emergency lights
Use the laryngoscope light to assist in finding other lights
Use a smartphone flashlight
Open the OR door to let in light from the corridor
If emergency power is on, ensure that all critical devices are connected to emergency power outlets
Ensure that the O 2 supply is still intact
If not, disconnect wall O 2 hose, open backup O 2 cylinders on the anesthesia workstation, and manually ventilate the patient’s lungs
If both the primary and emergency power systems have failed
The internal backup battery may power the anesthesia workstation for a short time, usually 30 to 60 minutes
Prolong battery life in workstations by reducing screen brightness to a minimum
Check the anesthesia workstation to determine what systems are functional. If there is any doubt about ability to oxygenate and ventilate the patient using the anesthesia workstation, ventilate with a self-inflating bag and a separate O 2 source
Check gas flow
If there is no gas flow, activate the manual emergency O 2 flowmeter if available and ventilate with self-inflating bag. Send help to obtain additional O 2 tanks and regulator
Check the ventilator to ensure the patient’s lungs are being mechanically ventilated
If the ventilator is not operating, initiate manual ventilation using the anesthesia workstation and breathing circuit or self-inflating bag
Consider manual ventilation to prolong battery life of the anesthesia workstation
Check that monitors are functioning
Send for battery-operated transport monitor
Confer with the surgeon
Consider the status of the surgical procedure and its urgency
If the surgery is at a critical point, the highest priority for lighting should go to the surgical field
Establish monitoring of the patient
Place esophageal or precordial stethoscope
Place manual BP cuff and check periodically
Palpate peripheral pulses or have the surgeon palpate arterial pulses in the operative field
Check that routine monitors with battery backups are still operating
Allocate available battery-operated transport monitors (high-acuity cases have priority)
Consider the need for additional IV anesthesia drugs
Ensure that OR staff and engineers are informed of the power failure and have activated the hospital disaster plan if appropriate
Allocate personnel and equipment where needed most
Patients undergoing CPB
Some pump oxygenators have battery backups but all have hand cranks
Complex or urgent surgical cases
ICU (all ventilators may be inoperative if there has been a large-scale power loss)
Reassess allocation of personnel and resources as the situation evolves
Determine time until power will be restored, if possible
If power supply is likely to take more than a few minutes to restore, terminate all non-emergent cases as soon as possible
Do not start non-emergent cases until a reliable electrical power supply is ensured
Complications
Hypoxemia
Surgical mishap
Hemodynamic instability
Intraoperative awareness
Suggested Reading
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