Hazard [Health Devices Mar 1985;14(4):133]

Problem

A member hospital reported that the plastic shell of a disposable blood oxygenator was severely damaged when liquid anesthetic spilled on it during a cardiopulmonary bypass procedure. The perfusionist observed blood seeping out of cracks in the oxygenator and interrupted extracorporeal perfusion to replace it. The patient suffered no adverse effects from the interruption of circulation.

Since pulmonary blood flow is interrupted during bypass, inhalation anesthesia must be administered via the oxygenator ventilation gases using a vaporizer to combine the liquid anesthetic and oxygen. Because of the length of some bypass procedures, some anesthesia vaporizers may not have sufficient capacity (or may not be adequately filled during setup), and may require refilling during surgery.

In the reported incident, the vaporizer was found to be empty when additional anesthesia was required late in the procedure. While pouring liquid Forane (isoflurane) into the vaporizer filling port, the perfusionist accidentally spilled a small amount (approximately 5 cc) onto the top of the bubble oxygenator, which was mounted on the heart-lung console directly below the vaporizer. Apparently, the Forane acted as a concentrated solvent and rapidly caused extensive cracking and crazing on the top of the unit, particularly around its bonded seams. The sampling port reportedly melted off and blood seeped out, forcing the perfusionist to halt extracorporeal perfusion for approximately two minutes until a new oxygenator was located and installed. The perfusionist minimized blood loss by salvaging the blood remaining in the oxygenator reservoir. However, perfusionists do not wear sterile gloves during bypass and may contaminate the setup while exchanging oxygenators.

We duplicated the reported interaction by applying halothane and methoxyflorane to several manufacturers' oxygenators. Commonly used anesthetic agents are powerful organic solvents that readily attack polycarbonate, the plastic material from which disposable oxygenators, including the arterial filter and cardiotomy reservoir, are generally made. Siliconized rubber or PVC tubing is normally used for both arterial and venous lines, and do not appear to be affected.

Molding and bonding of plastic creates areas of stress concentration. Liquid anesthetics can pervade these areas and severely degrade the polycarbonate. In fact, applying a relatively light force to a damaged oxygenator's arterial outlet or cardiotomy inlet can actually break it off.

Any breach of the oxygenator's exterior can introduce bacterial contamination or cause critical blood loss. Also, replacing a damaged oxygenator during bypass requires interrupting extracorporeal blood flow for several minutes and may introduce air to the patient. Although metabolic activity and oxygen demand are significantly lowered by induced hypothermia, cessation of extracorporeal blood flow during bypass is extremely risky and may jeopardize the success of the surgical procedure, particularly if perfusion is interrupted prior to cooling or during rewarming, when organ oxygen demand is critical.

Many perfusionists and anesthesiologists are not aware of the danger of exposing polycarbonate oxygenators to concentrated liquid anesthetics. In addition, oxygenator and liquid anesthetic manufacturers currently do not label their products with warnings about these harmful effects. All personnel involved with heart-lung bypass surgery should be aware of the consequences of exposing polycarbonate oxygenators to concentrated anesthetic agents and should take steps to prevent such events.

1. Alert all perfusionists and anesthesia personnel to this report.
2. Never place an anesthesia vaporizer above or near an oxygenator or any other polycarbonate device (e.g., blood filters, cardiotomy reservoirs).
3. Ensure that the vaporizer is adequately filled during setup to avoid refilling during the bypass procedure.
4. Consider placing the following label on all heart-lung machine consoles:

WARNING: Concentrated liquid anesthetics are powerful solvents and may damage plastic oxygenators. Do not mount vaporizer above or near the oxygenator. Be careful not to spill liquid anesthetic when filling vaporizer .

UMDNS Terms

• Anesthesia Unit Vaporizers [10-144]
• Filters, Blood [11-713]
• Filters, Heart-Lung Bypass Priming [17-580]
• Heart-Lung Bypass Units [11-969]
• Oxygenators, Extracorporeal, Bubble [11-974]
• Oxygenators, Extracorporeal, Membrane [17-643]
• Reservoirs, Cardiotomy [13-338]

Device factors: Design/labeling error; Device failure; Device interaction

User error: Accidental spill

Exposure to airborne infectious agents; Exsanguination