A new computerized bipolar coagulator is described in which tissue heating is switched off automatically when adequate vessel occlusion has been achieved, thus preventing overheating, undue tissue damage, cutting, and sticking of the forceps. Experiments with radiofrequency (rf) heating of albumin or arteries revealed an impedance minimum at the moment of coagulation. The attainment of this impedance minimum is transmitted electronically via a microprocessor to the coagulator, which automatically shuts off the rf energy supply. In experiments, adequate artery strength and avoidance of the drawbacks of conventional coagulation methods were achieved when rf heating was shut off soon after the impedance minimum was reached. Neither irrigation for cooling nor cleaning of the forceps tips was necessary. Electronic feedback through the same cables as used for coagulation enabled the use of conventional bipolar cables and forceps. The bipolar coagulator described can also be used for conventional bipolar coagulation under visual control. The microcomputer enables: 1) automatic coagulation cycles that start when tissue is picked up in the forceps and stop automatically on completion of the seal; 2) the change of power setting from a pedal and activation of automatic cycles by the pedal as described above or surgeon-controlled coagulation, which facilitates the use of alternative debridement with inactive forceps; 3) cable testing; and 4) negligible disturbance of the intraoperative monitoring equipment.
Thirteen bone tumours that were invading the craniofacial skeleton were operated on by intracranial procedures. The resected tumorous bone was autoclaved and put back. Follow up of no less than one year included 122mTc scanning, computed tomography, radiography, bone biopsy and clinical examination. In every case, when rigidly fixed, most of the autoclaved bone was gradually revitalised by invading new and normal bone. We conclude that autoclaved bone will be replaced by normal bone, and that the present technique is justified for reconstruction of complicated structures or large areas of bone after operations for tumours invading the craniofacial skeleton.
Myelin basic protein in spinal fluid was measured with a radioimmunoassay method after surgery of brain tumors and posttraumatic brains in thirteen cases. Three cases were studied daily for up to three weeks. Immediately after the operation the values were high but then successively returned to normal. Repeated measurement of the myelin basic protein in spinal fluid seem to be useful for assessing the healing rate of brain tissue after surgery for brain tumors and after other brain damage.
Primary cell cultures from newborn rat brain hemispheres were exposed to different irrigation fluids used in neurosurgery. The cells died after incubation for 5 min with hydrogen peroxide, and the number of cells was drastically decreased after 10 sec of incubation. They shrank after incubation in Elliott's artificial cerebrospinal fluid for 3 h, but the viability as determined by trypan blue exclusion test was not affected. Physiological sodium chloride, Ringer's solution and the culture medium 199 with Hank's salt had no noticeable effect on the viability or morphology of the cells.
The mesothelial cell integrity of the subdural and arachnoid surfaces in the cat was investigated by scanning electron microscopy after exposure to different irrigation fluids used in neurosurgery, as well as after drying by air. Irrigation for 3 hours with Elliott's Solution B and Ringer's solution retained the morphology of the cells. After exposure to saline for the same time, the mesothelial cells appeared perforated and were sometimes detached from the underlying connective tissue. Exposure to air for 15 minutes induced extensive, probably irreversible, cell damage. After 5 minutes of exposure to hydrogen peroxide, most cells disappeared, revealing the underlying collagenous connective tissue. These mesothelial cell changes might be one cause of the formation of postoperative subdural adhesions. In previous studies, disturbance of the blood-brain barrier was produced by those agents causing mesothelial cell damage. With hydrogen peroxide, widespread thrombosis occurred in leptomeningeal vessels supplying the cortex. Changes in these vessels can obviously be induced easily by fluids applied to the subdural space because of the close contact between the arachnoid and the adventitia of the vessels. This alternative should be considered in the treatment of cerebral vasospasm.
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