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Biomedical subjects

B Vällfors

Publications and source records attributed to B Vällfors.

At least 19 recordsLinked to original sources
PubMed1991

Repositioning of craniofacial tumorous bone after autoclaving.

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.

Adolescent↗
PubMed1991

Studies on coagulation and the development of an automatic computerized bipolar coagulator. Technical note.

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.

Animals↗
PubMed1986

Craniofacial surgery for trauma.

Craniofacial surgical techniques have yielded as an important spin-off better methods of treating severe craniofacial trauma. In this paper surgical techniques are discussed. It was concluded that the most important factors for successful reconstruction after craniofacial trauma is to do as much as possible the first time, to obtain wide exposure, ensure rigid fixation of bone pieces and grafts and to make use of a work bench procedure where bone fragments are assembled on a side table for subsequent reattachment to the head.

Adult↗
PubMed1986

The craniofacial approach to trauma.

Craniofacial surgical techniques have yielded better methods of treating severe craniofacial trauma. In this paper surgical techniques are discussed in principle and specifically presented through case reports. We conclude that the most important factors for successful reconstruction after craniofacial trauma are to do as much as possible the first time, to obtain wide exposure, to ensure rigid fixation of bone pieces and grafts, and to make use of a workbench procedure where bone fragments are assembled on a side table for subsequent reattachment to the head.

Adult↗
PubMed1986

Facial disassembly for tumor resection.

A standardized method of surgical dismantelling of the face for access to the periorbital area is described in detail. Its use in 11 patients with periorbital tumors is described and illustrated by selected case reports. It was concluded that many tumors in the periorbital area that previously were considered inoperable with craniofacial disassembling techniques can be adequately treated without sacrificing eyes or mutilating the face.

Adult↗
PubMed1985

Influence of ketanserin on 5-hydroxytryptamine-induced cerebrovascular spasm in the cat.

In an experimental cat model the leptomeningeal vasculature was studied by a vital microscopic brain window technique. The brain window was connected to a thermostat-regulated pool of Elliot's solution. By air-drying (10 min) of the arachnoid mesothelium access for drugs, applied into the pool, was established to the adventitia of the leptomeningeal vasculature. Application of 5-hydroxytryptamine (5-HT) (10(-6)-10(-4) M) caused dose-dependent contractile responses (morphometry of outer vessel diameter) of both arteries and veins of three different sizes (large, 200-300 microns; medium, 50-150 microns; small, 30-50 microns). A well-reproducible contractile response was obtained at challenge with 5-HT (10(-4) M) from the various vascular beds with most pronounced effects on the arterial side. If the animals were pretreated with peripheral blockade of serotonergic (5-HT2) receptors (ketanserin 0.3 mg/kg i.v.), challenge with 5-HT (10(-4) M) elicited no significant vascular responses on either the arterial or venous sides. Vital microscopy further visualized capillary beds after ketanserin pretreatment that were not seen under control conditions.

Animals↗
PubMed1985

Acute, subacute and chronic low back pain: clinical symptoms, absenteeism and working environment.

In this study the relationship between low back pain and the following factors was studied: Clinical findings, frequency and duration of absenteeism, social situation, psychosomatic and psychological factors and the working environment. The sample studied included 220 persons (participation frequency 86%) between the ages of 16-65 who had either acutely declared themselves unable to work because of low back pain (acute patients, n = 50) or who had been ill because of low back pain for one month (subacute patients, n = 50) or for three months (chronic patients, n = 70). A control group (n = 50) consisting of persons who had not been absent at all from work the last year was also included. Information regarding the participants' socio-economic situation, previous and present illnesses, further sick-listing during the one year follow-up period and the duration of absenteeism was obtained from the records of the Department of Health Insurance. The median age for men (68%) in the four different groups was 46, 46, 46 and 48.5, respectively. The corresponding figures for women were 50, 33, 33 and 49 years. Twenty percent were of foreign extraction. The proportion of foreigners in the group of non-participants (n=33) was higher (39%) and in this group there was a significantly greater frequency of previous episodes of ill health of short duration (less than or equal to 7 days + no certificate of ill health). Despite a careful clinical examination it was not possible to find any objective signs amongst 51% (86) of the patients. These patients exhibited normal motion of the back, normal musculature, no signs of neurologic involvement, negative straight-leg-raising test, no fixed painful position and no pain during percussion or palpation despite the fact they had subjective symptoms. The proportion of patients without objective findings increased with increased duration of absenteeism. Forty percent of the acute back patients displayed no objective findings. The corresponding figures for the subacute and chronic back patient groups were 34% and 70%, respectively. In the group without objective findings but with chronic pain (greater than 3 months) there was an increased frequency of Waddell's non-organic signs compared with the group with objective findings. Psychological and social problems increased with increasing duration of absenteeism. There were significantly more patients with psychiatric illness, signs of alcoholism and early retirement in the three months group compared to the remaining groups.(ABSTRACT TRUNCATED AT 400 WORDS)

Absenteeism↗
PubMed1984

Efficient atraumatic liquid suction by means of slit suction tubes combined with a pressure control unit.

In 1976 a modified suction system for neurosurgery and precision surgery was presented. It was developed to meet the need for efficient and atraumatic liquid suction. the system consists of suction tube ends provided with three vertical slits in the suction edge (W-tubes), a Pressure Control Unit (PCU) and an independent suction pump with an air capacity of 25-30 litres per min. This system has subsequently been modified for microsurgery. The PCU normally controls the negative pressure to 20 kPa (corresponding to 200 cm of water) for atraumatic suction of liquid, which is needed during most of the operating time. For suction of various tissues or cleaning the system, the surgeon can set the pressure limit to 50 or 90 kPa by means of a foot-operated IR-transmitter in a pedal with a kick-down function. The PCU and the W-tubes, which neutralize the pressure load on tissue and the sudden interruption of liquid flow that are inevitable with conventional suction tips, form a system with a high liquid suction capacity in spite of the atraumatic suction pressure. This is possible because the slits maintain a large active suction area. Crushed or soft tissues and coagulated blood are aspirated as and when required, if necessary by elevation of the negative pressure limit. The W-tubes are not provided with an air inlet hole on the tube because that method of pressure control proved unpredictable and variable and reduced the suction capacity by interfering with the flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurosurgery↗
PubMed1984

Automatically controlled bipolar electrocoagulation--"COA-COMP".

Modern bipolar electrocoagulation has certain limitations, especially regarding the regulation of the short coagulation course. Studies on the electrical parameters of tissues during heating led to the conclusion that impedance changes in a typical and reproducible way. Furthermore, the impedance value proved to be close to minimal at the moment of coagulation. Laboratory tests were performed to correlate the pressure strength of the sealed artery to the impedance change. The tests proved that strong seals were achieved when the coagulation was interrupted soon after minimum impedance. Good seals were also achieved with later interruption of the heating but the well-known phenomena of sticking of the forceps to tissues and charging of the tips with charred tissue became more prominent. Further electrocoagulation gives carbonisation, fulguration and risk of new haemorrhage. Based on these results, micro-computerized equipment was built which cut off the coagulation soon after minimum impedance, i.e. when good strength without sticking was achieved. This equipment was tested clinically and the trials showed that the method is practical and most reliable. The microcomputer also allows automatic start of the coagulation as needed during opening or closing of wounds, as well as providing a built-in test of the equipment. This equipment saves time and labour and increases safety.

Electrocoagulation↗
PubMed1983

Effect of radiologic contrast media and local anaesthetics on the blood-brain barrier and on the leptomeninges.

The leptomeninges of cats were exposed to lidocaine, metrizamide and methiodal sodium and compared with control brains exposed to Ringer's solution. As a sign of blood-brain barrier damage, an increased extravasation of albumin into the cerebral cortex was recorded after exposure to methiodal sodium; lidocaine or metrizamide did not produce such damage. Scanning electron microscopy revealed minor cellular reactions in the mesothelial cells of the leptomeninges after application of metrizamide, lidocaine and Ringer's solution. Methiodal sodium produced an extensive cellular damage of the leptomeningeal cells. The importance of testing the leptomeningeal reactions and the reactions of the blood-brain barrier to all liquid media used on the brain surface is emphasized.

Animals↗
PubMed1983

Mesothelial cell integrity of the subdural and arachnoid surfaces of the cat brain after exposure to neurosurgical irrigation fluids and air: a scanning electron microscopic study.

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.

Animals↗
PubMed1983

Current leakage in bipolar electrocoagulation.

Bipolar electrocoagulation has previously been shown to give a considerable amount of current leakage to ground from either of the two outputs. This might result in unwanted tissue destruction. Thus far, no standard has been proposed for current leakage to ground from the outputs of bipolar equipment. This study was performed to establish safe parameters for such leakage. To determine the limit for damage-no damage, monopolar stimulations were performed on the brain surface of dogs. Blood-brain barrier disturbance was used as an indicator of damage. The limit for acceptable current leakage was found to be about 10 to 15 mA. Most bipolar coagulators were found to exceed this value. The electrical data recorded in this study should be considered in the design of bipolar equipment for electrocoagulation.

Animals↗
PubMed1982

Exposure of the cat brain surface to neurosurgical irrigation fluids, hydrogen peroxide and air. Quantitative assay of blood-brain barrier dysfunction.

The effect of different irrigation fluids used in neurosurgery and of cortical exposure to air or hydrogen peroxides on the cat brain surface was tested by quantitative assay of extravasated albumen in the cortex and the white matter. Ringer's solution and Elliott's solution B induced no major blood-brain barrier (BBB) dysfunction after closed subdural perfusion for 3 hours. Normal saline induced slight BBB dysfunction extending throughout the cortex into the white matter after the same time of exposure. When these three solutions were applied to the brain surface via pledgets during exposure for 3 hours no further damage was induced. If 15 minutes exposure to air preceded the open perfusion via pledgets with Ringer's solution or Elliott's solution B for 2 hours and 45 minutes, no significant cortical BBB dysfunction was induced. There was a manifold increase in BBB dysfunction after perfusion with Ringer's solution or Elliott's solution B for 2 hours and 45 minutes followed by exposure to three per cent hydrogen peroxide for 5 minutes and a further 10 minutes perfusion with the previous irrigation fluid. Thus, normal saline was found unsuitable for neurosurgical irrigation purposes, due to disturbance of the BBB. Ringer's solution and Elliott's solution B protected the brain adequately even if only applied in pledgets. A short period of exposure to air had no effect on the BBB in the cortex, whilst exposure to hydrogen peroxide was detrimental to the BBB.

Animals↗
PubMed1981

Absorbable or nonabsorbable suture materials for closure of the dura mater?

This study was undertaken to determine which suture material would give the best results for closure of the dura mater. Because there is no need for the suture to remain longer than until healing has occurred and as remaining foreign material will predispose to foreign body reactions and infection, it was considered important to test new absorbable materials like polyglactin 910 (Vicryl) and polyglycolic acid (Dexon) for closure of the dura mater. The reactions from these materials were compared to those of silk and polyester (Ethibond) in dogs 60 days after the suture of dural incisions. The quality of healing with respect to the smoothness of the subdural surface, the presence of adhesions between sutures and the brain surface, the degree of absorption of the material, and reactions around the sutures were evaluated. Vicryl gave the best results, providing a smooth subdural surface without adhesions. It was almost totally absorbed when healing was completed, in contrast to Dexon and the other materials. The cellular reaction around Vicryl was slight. Silk, Ethibond, and Dexon protruded from the subdural surface and adhesions to the arachnoid were common. When the dura mater was removed, these adhesions tore off the leptomeninges with their vascular supply to the cortex. The results of these experiments seem to justify the recommendation of Vicryl for suturing of the dura mater. Such an absorbable material decreases the risk of foreign body reactions, and infections will be more easily combated because of the absence of foreign material. The lack of subdural adhesions is an advantage if reoperation is necessary.

Absorption↗
PubMed1980

A study of irrigation fluids for neurosurgery on brain primary cell cultures.

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.

Animals↗
PubMed1980

Increase in myelin basic protein in CSF after brain surgery.

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.

Adult↗