Lasers in neurosurgery: a historical overview.

This contribution to the history of laser applications to neurosurgical patients gives the background against which the subsequent developments took place. It covers the important facts regarding the theoretical formulations that led to the invention of the world's first laser in 1960. This was a pulsed ruby laser, which proved lacking in desirable surgical procedures, and at high powers was shown to be damaging to vital organs, such as the brain. It could be lethal to small animals. These very early tests of laser tissue and organ interaction included studies on protein in solution, cultured cells, brain, spinal cord and their surrounding tissues, and transplantable melanomas, as well as ependymoblastomas in mice. Fortunately, the continuous wave CO 2 laser came along in 1967 to replace both the pulsed ruby and neodymium-in-glass lasers. The CO 2 laser was quickly seen to possess surgical properties, namely, vaporization, cutting, hemostasis, and sterilization, without additional damage at a distance or remotely in time. Research studies on normal and pathologic tissues in and around the brain and spinal cord quickly and dramatically showed the potential for benefit to animal and human patients with experimental and naturally occurring neoplasms, burns, and decubitus ulcers. Lasers in neurosurgery are used largely for benign and malignant brain and spinal neoplasms. For benign tumors, debulking of tumor mass, and ablation of unwanted neoplasm without damaging adjacent, vital, functioning neural tissue, the laser adds another therapeutic adjunct and will, at times, aid in complete tumor removal. For malignant vascular growths, the laser will aid greatly in the safest possible excision with maximum hemostasis. Studies around the world, ongoing or planned, will surely extend the uses of lasers for neurosurgery into vascular, infectious, and reconstructive fields, particularly with the proliferation of laser instruments that exploit additional wavelengths into the larger infrared levels and even the shorter ultraviolet region. Experimental and, to some extent, clinical applications are testing the value of Nd:YAG, holmium:YAG, and erbium:YAG lasers in various surgical fields.

Physics of surgery with lasers.

The characteristics of the principal lasers used in surgery are summarized in Table 1. Their diverse effects on biologic tissues permit the following generalizations: The CO2 laser is best suited for precise, visually controllable tissue removal by vaporization with minimal marginal damage. Hemostasis is excellent for bleeding from capillary vessels, but difficult for larger ones. The Nd:YAG laser is best suited for the coagulation of larger tissue volumes of the order of 10 mm3 or more. Tissue heating inherently extends for several millimeters, leading to excellent hemostasis. Radiation from this laser is well transmitted through flexible optical fibers and clear fluids. The argon ion laser emits radiation in the visible range and is ideally suited for treating the retina and other tissues in the eye without damage to its transparent structures. Radiation of this laser is strongly absorbed by pigmented tissues, scattered and reflected by others, and transmitted by fluids. Its radiation can be focused to very small spot sizes, leading to high precision and high-power densities. It has hemostatic properties intermediate between those of the CO2 and of the Nd:YAG laser radiations. It is well transmitted through optical fibers and clear fluids. It is used extensively in ophthalmology and dermatology. Selected applications to neurosurgery and otology are being investigated. These lasers have become indispensable adjuncts to the surgical armamentarium of several specialties. The very success of these lasers is leading to a critical examination of their shortcomings and to a search for improved systems. Examples are (1) the ongoing search for optical fibers to transmit the radiation of the CO2 laser; (2) the development of systems for the sequential delivery to tissues of several wavelengths from a single unit (Fig. 14); and (3) investigations of tissue effects of laser beams in the ultraviolet and in the infrared at wavelengths intermediate between those of the Nd:YAG and CO2 lasers. The use of lasers has already contributed to improved medical care in many surgical disciplines. Additional areas of application can be confidently anticipated.

History of the carbon dioxide laser in otolaryngologic surgery.

The review of recent history shows that since the initial discovery of the principle of the laser, rapid dissemination and application of this modality in the field of medicine have occurred. The use of laser energy has become an established technique in microsurgery and endoscopic surgery, particularly in the field of otolaryngology and head and neck surgery. Laser instruments and surgical techniques and experience are becoming increasingly widely appreciated. All these developments are a tribute to the imagination and determination of a few individuals who were instrumental in recognizing the potential of laser energy for surgical application and in developing and using this new modality in clinical surgery. The major developments in laser surgery include early laboratory studies of laser surgical applications and their effects, the invention and development of instruments allowing application of laser energy in a variety of surgical settings, particularly the upper aerodigestive tract, and clinical studies confirming the efficacy of laser surgery. Other significant developments include the successful application of laser surgery in the eradication or control of selected cancers in the upper aerodigestive tract, including the tracheobronchial tree. Although a firm foundation for laser surgery is well established, its future offers a wide vista of new opportunities.

General techniques and clinical considerations in laryngologic laser surgery.

The carbon dioxide laser, one of the great advances in otolaryngology, has the characteristics of accuracy, reduced bleeding, reduced reaction, faster healing, and less scarring as compared with conventional surgery. Its beam is produced by creating an electric discharge within a cylinder containing carbon dioxide, nitrogen, and helium. The emitted beam is invisible, and special means are used to show exactly where the beam is going to impinge on the tissue. The effect of the power delivered to the tissue by the laser beam depends on the character of the tissues, the presence of char, the delivery device, and the condition of the lenses and mirrors. The imprint size varies with the power and the duration of exposure and is not necessarily the same as spot size. Repeated exposures increase the amount of tissue destruction and can be used to completely eradicate a lesion until the junction of normal and abnormal tissue is encountered. The following points and techniques are important in determining the results of carbon dioxide laser surgery. Increasing the power and reducing the duration of the beam result in less charring, less reaction, and faster healing. Overheating of tissues is avoided by using a skip technique. Char must be removed to prevent overheating of tissues and to aid in identifying accurately the junction of normal and pathologic tissues. Palpation may help identify pathologic tissue not readily apparent on inspection alone. The edge of the beam can be used to shave away pathologic tissue accurately while preserving normal tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Physics of the surgical laser.

Following a brief historical introduction to the use of lasers in surgery, the principal characteristics of laser light sources relevant to surgery with lasers are reviewed and the nomenclature most often used in connection with laser devices is explained. The interactions of electromagnetic energy with soft tissues that make possible ablative surgery with carbon dioxide lasers are stressed. The general requirements of laser instruments for clinical surgery are mentioned in conclusion.

Laser surgery in exsanguinating liver injury.

Thirty-two conditioned 15-18 kg dogs underwent laparotomy, heparinization, left lateral hepatic lobe injury and subsequent partial left lateral hepatic lobectomy. The hemostatic capabilities of the surgical scalpel combined with suture ligatures and stay sutures, the Bovie, and the CO2 laser were compared. The CO2 laser proved significantly more effective in achieving hemostasis both in comparison to the Bovine and the surgical scalpel combined with classical methods. The postoperative mortality utilizing the Bovie was 11%, the scalpel 30% and the laser 23%. Two of the three laser deaths were related to a bulky laser delivery system which can be redesigned. Postoperative laboratory evaluation revealed that SGOT, LDH, alkaline phosphatase, total protein, albumin and hemoglobin levels were altered in the postoperative period but returned to normal levels in uniform fashion in all groups. There was no statistical difference between various surgical modalities with regard to these parameters. The white blood count was significantly lower in laser dogs when compared to the other two groups. Other laboratory parameters were unchanged. Damage to liver tissue may be less extensive when the laser is utilized as opposed to the Bovie or stay suture methods of hemostasis and healing is equally good. The CO-2 laser is considered a valuable ancillary tool in hepatic resection and clinical evaluation is warranted.