Equipment Events

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

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

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

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

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

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)