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Intraoperative dermatomal evoked potential monitoring fails to predict outcome from lumbar decompression surgery.

STUDY DESIGN: Thirty-three patients with single-level, unilateral lumbosacral radiculopathy underwent micro-decompression and intraoperative dermatomal evoked potential monitoring. Side-to-side latency asymmetry was calculated. A criteria for "abnormal" was defined. Intraoperative dermatomal evoked potentials were obtained before and after decompression. The changes were correlated with clinical outcome at the 3-month follow-up examination. OBJECTIVES: To determine whether intraoperative dermatomal evoked potential latency asymmetry confirms nerve root compression and whether an improvement of latency asymmetry after decompression predicts a good clinical outcome. SUMMARY OF BACKGROUND DATA: Intraoperative dermatomal evoked potential has been proposed as a test to assess the adequacy of nerve root decompression. Initial reports suggested improvement of dermatomal evoked potential amplitude and latency after decompression. The clinical efficacy is controversial because of its technical difficulty and inherent variation. METHODS: Cervical recording was chosen to reduce the effects of anesthesia. The asymptomatic nerve root was used as a control. Quality of the tracings was determined by evoked potentials-to-noise amplitude ratio. Clinical outcome was based on patient's pain relief and satisfaction. RESULTS: Tracings of acceptable quality were obtained at baseline in 57.6% (19 of 33) of patients. A side-to-side latency asymmetry > 5% was defined as abnormal. Before decompression, 68.4% (13 of 19) of patients had an abnormal dermatomal evoked potential. After decompression, latency asymmetry returned to normal in every patient. Clinical outcome was good or excellent in 13 patients, fair in four patients, and poor in two patients. Dermatomal evoked potential latency improvements were not related to variation in clinical outcome. CONCLUSIONS: Intraoperative dermatomal evoked potential monitoring is technically demanding. Finding reproducible potentials is difficult. More research is necessary before general use of dermatomal evoked potentials for monitoring nerve root decompression.

Adult↗

Effects of decompressive craniectomy on regional cerebral blood flow in severe head trauma patients.

The effect of decompressive craniectomy on regional cerebral blood flow (rCBF) was investigated in five patients with severe head trauma who underwent decompressive craniectomy. Repeated rCBF studies using single photon emission computed tomography with 99mtechnetium-hexamethylpropyleneamine oxime observed that a hyperperfusion area (focal CBF increase) occurred in the decompressed brain within 24 hours after decompressive craniectomy. The hyperperfusion area in the decompressed brain enlarged and increased in severity by 1 week after surgery. However, it attenuated and disappeared by 1 month after surgery. The chronology of the hyperperfusion area corresponded to the change in the swelling of decompressed brain observed by x-ray computed tomography. Patient consciousness showed a significant and progressive improvement in the postoperative 1 month period. Decompressive craniectomy may cause a focal CBF increase in the decompressed brain related to the beneficial effect in patients with acute severe head trauma.

Adolescent↗

Rabbit lung injury induced by explosive decompression.

OBJECTIVE: To study the mechanism of rabbit lung injury caused by explosive decompression. METHODS: A total of 42 rabbits and 10 rats were served as the experimental animals. A slow recompression-decompression test and an explosive decompression test were applied to the animals, respectively. And the effects of the given tests on the animals were discussed. RESULTS: The slow recompression-decompression did not cause an obvious lung injury, but the explosive decompression did cause lung injuries in different degrees. The greater the decompression range was, the shorter the decompression duration was, and the heavier the lung injuries were. CONCLUSIONS: Explosive decompression can cause a similar lung injury as shock wave does. The primary mechanical causes of the lung injury might be a tensile strain or stress in the alveolar wall and the pulmonary surface's impacts on the inside wall of the chest.

Journal Article↗

The effect of surgical decompression on neurologic outcome after lumbar fractures.

From 1980 until 1989, 69 patients with lumbar fractures resulting in incomplete paraparesis were admitted to the authors' medical center for treatment. Thirty had anterior vertebrectomy, including 18 who had posterior instrumentation and four who had anterior instrumentation. Twenty-two patients were treated with a posterolateral decompression and fusion, including four who also required an anterior decompression. Nineteen of the remaining 21 patients required posterior spine instrumentation and fusion only. The American Spinal Injury Association (ASIA) motor index score was determined for each patient pre- and postoperatively and used to compare these three treatment groups. Average follow-up period for the patients was 19 months. The improvement in ASIA motor score for all patients treated with decompression averaged 10 and similar improvement was obtained in those who were treated with posterior decompression (10.2 points). The average improvement in those who had vertebrectomy was 9.9 points. For those who had fusion without decompression, average improvement was 4.2 points. Comparing those patients who were surgically decompressed, either anteriorly or posteriorly, with those patients who only underwent fusion, the difference in neurologic improvement was statistically significant. Neurologic outcome after lumbar fractures is improved by surgical decompression. The neurologic outcome results were similar after anterior and posterior decompression.

Follow-Up Studies↗

The effect of early craniocervical decompression on functional outcome in neonates and young infants with myelodysplasia and symptomatic Chiari II malformations: results from a prospective series.

The indications for hindbrain decompression in neonates and young infants with spinal dysraphism who experience brain stem dysfunction in association with Chiari II malformations have remained controversial. This largely reflects the fact that the postoperative outcome in such patients has often been poor, which has supported the belief that much of the brain stem compromise in these patients is congenital and inherently irreversible. However, in a previous retrospective review of our operative results between 1975 and 1989, we noted that a significant component of the brain stem dysfunction in these children was an acquired phenomenon that potentially was reversible with prompt operative intervention. Accordingly, we hypothesized that with early craniocervical decompression, excellent functional outcome could be achieved in a majority of neonates and young infants with symptomatic Chiari II malformations. On the basis of this premise, we prospectively treated all such patients since 1989 with urgent brain stem decompression after other potential causes for brain stem dysfunction, such as progressive hydrocephalus, had been ruled out. All children underwent limited suboccipital craniectomies, cervical laminectomies extending beneath the inferior extent of the cerebellar tissue, and dural decompressions. The outcome in these patients has been favorable in comparison with previous studies. Ten of the 13 children treated according to this protocol recovered normal or nearly normal brain stem function shortly after decompression; 1 child had mild residual unilateral lower cranial nerve paresis. None of these children required a tracheostomy for ventilatory support, and only one required a temporary gastrostomy. The other three children all exhibited bilateral vocal cord paralysis and severe central hypoventilation by the time decompression was performed and failed to have any meaningful recovery of function. We conclude that early recognition of the symptoms of brain stem compromise in neonates and young infants with spinal dysraphism coupled with urgent evaluation and decompression are effective in producing prompt resolution of the brain stem dysfunction in most affected patients. Conversely, the prognosis for recovery is poor in children who exhibit bilateral vocal cord paralysis by the time of decompression.

Arnold-Chiari Malformation↗

Biophysical basis for inner ear decompression sickness.

Isolated inner ear decompression sickness (DCS) is recognized in deep diving involving breathing of helium-oxygen mixtures, particularly when breathing gas is switched to a nitrogen-rich mixture during decompression. The biophysical basis for this selective vulnerability of the inner ear to DCS has not been established. A compartmental model of inert gas kinetics in the human inner ear was constructed from anatomical and physiological parameters described in the literature and used to simulate inert gas tensions in the inner ear during deep dives and breathing-gas substitutions that have been reported to cause inner ear DCS. The model predicts considerable supersaturation, and therefore possible bubble formation, during the initial phase of a conventional decompression. Counterdiffusion of helium and nitrogen from the perilymph may produce supersaturation in the membranous labyrinth and endolymph after switching to a nitrogen-rich breathing mixture even without decompression. Conventional decompression algorithms may result in inadequate decompression for the inner ear for deep dives. Breathing-gas switches should be scheduled deep or shallow to avoid the period of maximum supersaturation resulting from decompression.

Adult↗

Decompression comparison of N2 and O2 in rats.

We have previously reported that O2 in the breathing gas mixture contributed significantly to the risk of decompression sickness (DCS) in rats after rapid (less than 10 s) decompression to the surface from depth. The rate of O2 uptake was extremely fast (less than 1 min estimated for equilibrium after a pressure change) compared to much slower rates for He and N2. To further define the role that O2 plays in diving, the present investigation examined decompression outcome in unanesthetized male albino rats after 60-min N2-O2 dives (1-3 atm abs O2, depth 6.26 or 7.26 atm abs). Slower decompression profiles were used to determine the elimination rates of N2 and O2 as pressure was reduced and included "stops" of up to 20 min. The probability of DCS was modeled using the maximum likelihood technique. O2 again contributed significantly to the risk of DCS, although O2 was eliminated very rapidly during decompression; the washout of N2 was considerably longer. These findings support the view that O2 can add significantly to decompression risk. However, this phenomenon may not normally be encountered during human diving operations where relatively slower decompression and lower PO2's are used.

Animals↗

Evaluation of standard decompression schedule by agarose gel method.

The Standard Decompression Schedule was evaluated by the method of bubble formation in agarose gel, the result of which can be summarized as follows: 1) The number of bubbles formed in agarose gel corresponded well with the exposed pressure. 2) The technique of this method was simple and the number of bubbles was accurately counted. 3) Eventually, this method was useful for examining the decompression schedules. 4) It is not always safe to follow the Standard Decompression Schedule in some pressure conditions. 5) As to the period of time that a person is able to tolerate a high pressure condition, the prescription of the Standard Decompression Schedule is not necessarily correct. 6) The number of bubbles was small by the proper decompression schedule, for example, in the cases of exposure above the 60-meter depth of water. 7) This method can be applied for the prevention of decompression sickness when the agarose gel samples are attached to the workers during the compressed air work. 8) The number of bubbles was inconsistent with the coefficient of body pressure (1. N2 in the body), therefore it is not necessarily safe to rely only on the coefficient of body pressure. 9) To prevent osteonecrosis, the Standard Decompression Schedule is not proper, a deeper first stop and slower ascent being recommended.

Decompression↗

Air and nitrox saturation decompression: a report of 4 schedules and 77 subjects.

Seventy-seven subjects were decompressed from air or nitrogen-oxygen (nitrox) saturation exposures at 18.3 to 40.2 meters sea water (msw) [60 to 132 feet sea water (fsw)] using four different decompression schedules. A h schedule for decompression from an air saturation-excursion profile at 18.3 msw (60 fsw) resulted in pain-only decompression sickness (DCS) symptoms in 2 of 23 subjects. A 32 and 35 h schedule from a different air saturation profile at 19.8 and 22.9 msw (65 and 75 fsw), respectively, resulted in DCS symptoms in 1 of 24 subjects. A third and fourth schedule for air or nitrox saturation at 40.2 msw (132 fsw) resulted in DCS symptoms in 3 of 12 and 1 of 18, respectively. No serious (type II) symptoms were observed as a result of any of the decompressions. All DCS cases consisted of knee pain occurring either in the last 3 msw of the decompression or shortly after surfacing. Doppler ultrasound monitoring revealed venous gas emboli (VGE) in several subjects, but generally only shallow to 6.1 msw (20 fsw). Results demonstrate an overall DCS incidence of 9%, and all cases were pain-only and localized to the knee. The third schedule (U.S. Navy heliox saturation decompression schedule) seems to produce a higher incidence of DCS than the other schedules when used in air or nitrox exposures. Differentiation between the schedules designed for nitrox was impossible due to the limited number of subjects in each and the variable nature of the exposures.

Adult↗

[A method for evaluating the safety of decompression regimens for divers].

The authors offer a way of estimation of safety modes of decompression, based on definition of intensity of venous gas embolism (VGE) at each decompression and account of probability of illness of divers in series of tests. Intensity of VGE was determined with the help of ultrasonic gas bubbles Doppler radar. Comparative safety of standard modes of decompression of divers of the Navy was estimated, and also the modes, designed in accordance with mathematical model of decompression, offered by I. A. Voĭtsekhovich (1990), were done. The results testify, that use of ultrasonic radar for estimation of intensity of VGE at decompression and account of average and maximum probability of decompression illness in series of tests of modes permit to receive the comparative characteristic of safety of modes at small number of decompressions.

Adult↗

Compressed air tunneling and caisson work decompression procedures: development, problems, and solutions.

Multinational experience over many years indicates that all current air decompression schedules for caisson and compressed air tunnel workers are inadequate. All of them, including the Occupational Safety and Health Administration tables, produce dysbaric osteonecrosis. The problem is compounded because decompression sickness (DCS) tends to be underreported. Permanent damage in the form of central nervous system or brain damage may occur in compressed air tunnel workers, as seen on magnetic resonance imaging, in addition to dysbaric osteonecrosis. Oxygen decompression seems to be the only viable method for safely decompressing tunnel workers. Oxygen decompression of tunnel workers has been successfully used in Germany, France, and Brazil. In Germany, only oxygen decompression of compressed air workers is permitted. In our experience, U.S. Navy tables 5 and 6 usually prove adequate to treat DCS in caisson workers despite extremely long exposure times, allowing patients to return to work following treatment for DCS. Tables based on empirical data and not on mathematical formulas seem to be reasonably safe. U.S. Navy Exceptional Exposure Air Decompression tables are compared with caisson tables from the United States and Great Britain.

Decompression↗

Comparison of haemodynamic effects during venous air infusion and after decompression in pigs.

We have compared haemodynamic effects of venous gas emboli during continuous air infusion into the right atrium and after rapid decompression in pigs. Eight anaesthetized and spontaneously breathing pigs received continuous air infusion at a rate of either 0.05 ml.kg-1.min-1 (six pigs, air infusion group) or 0.10 ml.kg-1.min-1 (two pigs). Another eight pigs (decompression group) underwent a 30-min compression to 5 bar (500 kPa, absolute pressure), followed by a rapid decompression (2 bar.min-1). Haemodynamic variables were measured or calculated, and bubbles in the pulmonary artery were monitored using transoesophageal echocardiography. The results showed less variation in the maximal increase in mean pulmonary arterial pressure (BPa,pulm) during air infusion (0.05 ml.kg-1.min-1) than after decompression, although the mean maximal increase did not differ between the two groups [28.0 mmHg (3.73 kPa), 95% confidence interval (CI) 23.5-32.5, vs 32.0 mmHg (4.27 kPa), 95% CI 25.3-38.7, P = 0.3]. The BPa,pulm stabilized or decreased very slowly after peak values were reached in the air infusion group, whereas the BPa,pulm decreased rapidly during the same period in the decompression group. No significant changes in mean arterial pressure were observed during air infusion (0.05 ml.kg-1.min-1), in contrast to the rapid increase and the subsequent decrease, that appeared after decompression. Finally, the maximal bubble count was much lower in the air infusion group than in most of the pigs in the decompression group. The two pigs that received 0.10 ml.kg-1.min-1 stopped breathing after 5-min infusion, developed arterial hypotension and died.

Animals↗

Computed chest tomography in an animal model for decompression sickness: radiologic, physiologic, and pathologic findings.

This study was conducted to investigate the early pulmonary effects of acute decompression in an animal model for human decompression sickness by CT and light microscopy. Ten test pigs were exposed to severe decompression stress in a chamber dive. Three pigs were kept at ambient pressure to serve as controls. Decompression stress was monitored by measurement of pulmonary artery pressure and arterial and venous Doppler recording of bubbles of inert gas. Chest CT was performed pre- and postdive and in addition the inflated lungs were examined after resection. Each lung was investigated by light microscopy. Hemodynamic data and bubble recordings reflected severe decompression stress in the ten test pigs. Computed tomography revealed large quantities of ectopic gas, predominantly intravascular, in three of ten pigs. These findings corresponded to maximum bubble counts in the Doppler study. The remaining test pigs showed lower bubble grades and no ectopic gas by CT. Sporadic interstitial edema was demonstrated in all animals--both test and control pigs--by CT of resected lungs and on histologic examination. A severe compression-decompression schedule can liberate large volumes of inert gas which are detectable by CT. Despite this severe decompression stress, which led to venous microembolism, CT and light microscopy did not demonstrate changes in lung structure related to the experimental dive. Increased extravascular lung water found in all animals may be due to infusion therapy.

Acute Disease↗

[Lateral orbital decompression for Graves' orbitopathy. Indication, surgical technique, and treatment success].

PURPOSE: In Graves' disease a discrepancy between volume increase of the orbital soft tissues and fixed volume of the orbital cavity leads to exophthalmos. The patients do not only feel cosmetically disfigured, they often complain about more or less painful retroorbital pressure sensation or show symptoms of compressive optic neuropathy or corneal exposure because of a significant lid lag. To solve this problem, different orbital decompression techniques have been developed. This is to report about our results with a modified Dollinger technique for lateral orbital decompression. PATIENTS AND METHODS: A total of 27 patients aged 19-76 years (mean: 45.1 years) with Grave's ophthalmopathy were recorded who had undergone orbital decompression by a lateral approach between June 1999 and April 2003. The modified Dollinger technique was performed by deepening the osteotomy to the level of the sphenoid wing and by additional resection of intraconal fat. RESULTS: The reduction of exophthalmos achieved after decompressive surgery averaged 2.9 +/- 1.1 mm. Of the patients whose indication for orbital decompression was a compressive neuropathy, the visual acuity improved postoperatively for 3 lines. Of the 16 patients with preoperative retrobulbar pressure sensation, 12 had no complaints after the operation. Remarkably no significant impairment of the ocular motility resulted after surgery. CONCLUSIONS: Decompression of the orbit by the modified Dollinger technique is a safe and effective approach to reduce exophthalmos, retrobulbar pressure sensation, and compression neuropathy as a result of diffusely elevated orbital tissue tension. In the case of direct compression of the optic nerve in the orbital apex, additional medial orbital wall decompression has to be considered.

Adult↗

A randomized trial of very early decompressive craniectomy in children with traumatic brain injury and sustained intracranial hypertension.

OBJECT: The object of our study was to determine, in children with traumatic brain injury and sustained intracranial hypertension, whether very early decompressive craniectomy improves control of intracranial hypertension and longterm function and quality of life. METHODS: All children were managed from admission onward according to a standardized protocol for head injury management. Children with raised intracranial pressure (ICP) were randomized to standardized management alone or standardized management plus cerebral decompression. A decompressive bitemporal craniectomy was performed at a median of 19.2 h (range 7.3-29.3 h) from the time of injury. ICP was recorded hourly via an intraventricular catheter. Compared with the ICP before randomization, the mean ICP was 3.69 mmHg lower in the 48 h after randomization in the control group, and 8.98 mmHg lower in the 48 hours after craniectomy in the decompression group (P=0.057). Outcome was assessed 6 months after injury using a modification of the Glasgow Outcome Score (GOS) and the Health State Utility Index (Mark 1). Two (14%) of the 14 children in the control group were normal or had a mild disability after 6 months, compared with 7 (54%) of the 13 children in the decompression group. Our conclusion was that when children with traumatic brain injury and sustained intracranial hypertension are treated with a combination of very early decompressive craniectomy and conventional medical management, it is more likely that ICP will be reduced, fewer episodes of intracranial hypertension will occur, and functional outcome and quality of life may be better than in children treated with medical management alone (P=0.046; owing to multiple significance testing P <0.0221 is required for statistical significance). This pilot study suggests that very early decompressive craniectomy may be indicated in the treatment of traumatic brain injury.

Brain Injuries↗

Efficacy and side effects of 'swinging eyelid' orbital decompression in Graves' orbitopathy: a proposal for standardized evaluation of diplopia.

OBJECTIVES: To evaluate the efficacy and side effects of 'swinging eyelid' orbital decompression in patients with Graves' orbitopathy (GO). To calculate the incidence of postoperative new-onset diplopia (NOD) using a newly proposed scoring system for diplopia. METHODS: We reviewed the clinical data on proptosis, visual acuity, and diplopia in 104 consecutive patients (198 orbits) with GO, who underwent orbital decompression. A combined lateral canthal and inferior fornix incision ('swinging eyelid' approach) was used for removal of the medial wall, the orbital floor and, if indicated, the lateral wall. Indications for surgery were disfiguring/congestive GO (DGO) in 79 patients (149 orbits) and compressive optic neuropathy (CON) in 25 patients (49 orbits). Diplopia was scored according to four grades. In both groups, the incidence of new-onset (continuous) diplopia (NOD), deterioration of diplopia (DOD), and improvement of diplopia (IOD) were calculated, using strictly defined criteria. Our data on NOD were compared to those from other series, after recalculation according to our criteria. RESULTS: The mean proptosis reduction was 4.6 mm (range 0-9.5 mm) after three-wall decompression (95 patients, 180 orbits) vs 3.1 mm (range 0-7 mm) after two-wall decompression (nine patients, 18 orbits). The visual acuity improved in 98% of the patients with CON. In patients with DGO, NOD occurred in 14%. In patients with CON, NOD was not observed, but DOD occurred in 41%. Our data compare favourably to the reported incidence of NOD after either transantral or transnasal decompression. CONCLUSIONS: "Swinging eyelid' orbital decompression is efficacious for proptosis reduction as well as for optic nerve decompression. A scoring system for standardized evaluation of diplopia is proposed.

Adolescent↗

Comparison of results of core decompression and intertrochanteric osteotomy for nontraumatic osteonecrosis of the femoral head using Cox regression and survivorship analysis.

Different surgical procedures have been recommended for osteonecrosis of the femoral head to prevent or delay the need for arthroplasty. Core decompression is a commonly used treatment in the early stages of the disease, but the published efficacy has varied markedly. Only a few comparisons of different techniques have been reported. The aim of this study was to evaluate and compare the results of 2 commonly used procedures, core decompression and intertrochanteric osteotomy, using Cox regression and survivorship analysis. A total of 177 cases with a mean age of 41 years at surgery were treated for osteonecrosis (94 core decompressions, 83 osteotomies). Any further surgery was defined as failure and endpoint. Significant risk factors for treatment failure were age > 40 years at surgery (P = .022), corticosteroid intake (P < .001), advanced stage of necrosis (Steinberg stage > or =III, P=.04), and core decompression (P = .084). To analyze the influence of the surgical procedure, patients with corticosteroid treatment were excluded, and survival analysis was performed. This analysis revealed survival rates of 74% after osteotomy and 78% after core decompression 6 years postoperatively in early, precollapse stages (P = .819). In advanced stages, the rate of survival for hips after core decompression was lower (56%) than in hips after osteotomy (76%) (P = .056). Our results indicate that core decompression may be as effective as intertrochanteric osteotomy in precollapse stages but is less traumatizing and is cost-effective. For postcollapse hips, intertrochanteric osteotomy should be considered.

Adolescent↗

Effects of acute pancreatic duct obstruction on pancreatic perfusion: implication of acute pancreatic duct decompression.

BACKGROUND: Acute pancreatitis can result in pancreatic ischaemia and necrosis. Pancreatic duct (PD) obstruction may be the first step causing ischaemia in acute pancreatitis. Nitric oxide donors can attenuate acute pancreatitis through improvement in compromised pancreatic perfusion (PP). In this study, we determined if (1) PD obstruction altered PP and (2) PD decompression or L-arginine administration reversed this change. METHODS: Fifteen Australian possums were randomly assigned to two groups: Animals in group A (n = 6) were subjected to 30 min of PD obstruction and 60 min of PD decompression. Animals in group B (n = 9) were subjected to 120 min PD ligation and 60 min PD decompression. A subset group B (n = 6) were subjected to intravenous L-arginine (100 microg/kg) at the end of 120 min of ligation and at the end of PD decompression. The PP (Laser Doppler fluxmetry), PD pressure and blood pressure were continuously monitored. RESULTS: PD pressure increased from 2.9 +/- 2.5 to 18.1 +/- 4.9 mmHg following PD ligation. PP was reduced to 67.1% +/- 4.5% (P<0.01) and 46.2% +/- 7.5% (P<0.001) of baseline following 30 and 120 min of PD ligation, respectively. Following 60 min of PD decompression, PP was restored to 89.1% +/- 13.4% (P<0.02) of the baseline in the 30-min group. However, following 120 min PD ligation, PP remained depressed. L-arginine administration after 120 min of PD ligation transiently increased PP from 46.2% +/- 7.5% to 81.1% +/- 8.6% (P<0.03) of baseline. This effect was reproduced if L-arginine was administered at the end of decompression (P<0.05). CONCLUSION: In patients with acute pancreatitis due to obstructive causes, early decompression of the PD may prevent early pancreatic ischaemia.

Acute Disease↗