Surgical Smoke Evacuation

What is plume? With each excimer laser pulse striking the cornea water vapor, cellular debris, breaking nitrogen peptide bonds in cellular protein, and various elements are released creating “plume” that instantly splatters and scatters into the air above the immediate surgical field.

Some of the elements that characterize the plume’s composition include water vapor, dead and live cellular material, carbonized tissue, blood, viruses, and the gases benzene, hydrogen cyanide, toluene, and formaldehyde, and polycyclic aromatic hydrocarbons.

Plume generated during LASIK surgery can present several potential problems.

Plume is a potential health hazard to the patient, the surgeon, and the operating personnel. Research studies have shown that the particles in laser plumes can potentially inhibit human lung efficiency in addition causing respiratory irritations and having mutagenic and carcinogenic potential. Evidence suggests that fears of breathing laser plume may be warranted for the following additional reasons:

• Viruses including human papilloma virus (HPV) and HIV have been cultured from surgical plume.
• A 1994 study by McKinley and Ludlow demonstrated that some bacteria could be cultured from the smoke.
• Studies on sheep and rats found that breathing laser smoke caused transient hypoxia, depression of lung defense mechanisms, delayed airway inflammation, emphysema, interstitial pneumonia, bronchiolar hypoxia and hyperplasia, and lymphocytic infiltration.
• Surgical masks, which are primarily designed to filter out plume, are not very effective because they allow leakage around the perimeter.

One must consider the physiological impact of the “burning flesh” odor resulting from excimer laser refractive procedures. Naturally, the odor of surgical smoke and aerosol is extremely offensive to physicians, nurses, patients, and others in the operating room. It attaches to hair surgical attire, and any exposed skin surfaces. There is also evidence that the unpleasant smell heightens patient anxiety.

Plume Smoke – A direct effect of LASIK plume “smoke” is the “masking effect” created as it “hangs” just over the ablating stromal bed, blocking subsequent excimer pulses. The masking effect can affect laser beam etching (corneal tissue removal).

Airborne particles form a cloud between the laser and the stromal bed, and this can cause a measurable difference in the laser’s ablation. This may contribute to unexpected outcomes such as under-correction, central island formation, or irregular astigmatism.

Particle Fall Back – Researchers and ophthalmologist contend that the plume particles falling back onto the ablating stromal bed creates additional beam masking (blocking) and may be a contributing factor to Sands of the Sahara Syndrome according to Dr. Dell. Dr. Keith Charles studied the effects of using a laser plume evacuation method and not using plume evacuation and found a 0% incidence of diffuse lamella keratitis with use of plume evacuation vs. a 1.2% occurrence in those patients where the plume evacuation was not used.

Plume Vapor Condensation – Researchers and ophthalmologists contend that plume vapor condensation with precipitation contributes to visible fluid accumulation on the surface of the stromal bed during ablation. This additional regional accumulation of fluid blocks or masks the laser beam, resulting in a decrease in transmission of laser energy to the stromal through increased reflection and absorption of incident laser energy. This may result in an undesirable ablation, such as central islands, “hot and cold” spots, under corrections, visual aberrations, and loss of best-corrected acuity, higher order aberrations, increased glare and nighttime halos.

Conventional LASIK -There is considerable variability in LASIK surgery in the way that excimer generated plume is managed. Some do not provide for plume evacuation. (Illustration 18)

Some of the commercial laser systems incorporate a single large plume vacuum tube that is positioned several inches from the patient’s eye. (Illustration 19)

This large size limits how close it can be positioned to the source of plume during ocular surgery. Research has demonstrated that the efficiency of plume evacuation degrades rapidly the farther the evacuation port is from the target tissue. Some researchers believe that the plume evacuators integrated into the commercial excimer lasers are extremely inefficient. Physicians and the patients question the effectiveness of the evacuators on some lasers. The efficiency of an evacuation system relates mostly to the distance between the plume source and the evacuator’s port. To compensate for the increased distance some of these conventional lasers’ intergraded plume evacuators may generate a large volume flow of non-filtered room air across the “sterile” surgical field. The plume in some systems must travel a vertical distance before eventually being evacuated from the surgical field. The vertical downward traveling treatment laser beam may become “masked” by this oppositely (upward) traveling plume smoke. In addition, the airflow generated at the entrance of some of the distally positioned, large plume evacuation systems is turbulent. It is the opinion of some researchers that turbulent airflow between the laser delivery system and the patients’ eyes may cause random variability in beam etching contributing to under-correction, island formation, or irregular astigmatism. (Illustration 20)

LAHayeSIK™ Surgical System - The LAHayeSIK™ Handpiece is designed to remove laser beam masking plume particles and plume water vapor just millimeters from the ablating target tissue, reducing the need for a large volume vacuum flow and reducing additional exposure of the laser pulses (beam masking) to the vertically traveling plume. With LAHayeSIK™ Surgical System, plume removal is laminar (non-turbulent) and occurs in close proximity to the target tissue through seven ports in the LAHayeSIK™ Handpiece. (Illustration 21)

Some researchers and LASIK physicians believe that the most efficient way to remove plume smoke and establish even corneal hydration is to control a microclimate above the patient’s cornea by means of proximal plume evacuation systems that features an evacuation cylinder chamber that fixates to the patient’s eye. Additionally efficient plume evacuation may reduce the incidence of plume particles attaching to the lens of the laser that may impair the laser’s performance until the lens is cleaned or replaced.

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