Cryotherapy: an effective modality for decreasing intraarticular temperature after knee arthroscopy.

Cryotherapy is a modality commonly used after arthroscopic procedures. We divided 17 patients into two groups after routine knee arthroscopy: 12 patients were immediately treated with ice and 5 control patients were treated without ice for the first hour. In all patients, thermocouple probes were placed intraarticularly into the lateral gutter of the knee. Ice was placed on the operative knees of the treatment group for 2 hours. The control group had no intervention for the 1st hour and then had ice applied for the 2nd hour. Temperatures were continually recorded every minute for 2 hours. The temperature in the treatment group declined significantly, by 2.2 degrees C (95% confidence interval [-3.6 degrees C, -0.72 degrees C]) over the 1st hour and by 0.79 degrees C (95% CI [-1.8 degrees C, 0.18 degrees C]) over the 2nd hour (P = 0.008). The temperature in the control group increased significantly, by 5.0 degrees C (95% CI [2.4 degrees C, 7.5 degrees C]) over the 1st hour (P = 0.006). After ice was applied, the temperature fell significantly, by 4.0 degrees C (95% CI [-8.3 degrees C, 0.26 degrees C]) (P = 0.06). The difference between the temperature decrease in the treatment group and the increase in the control group at 60 minutes was 7.1 degrees C. This is the first rigorously conducted study in human patients that documents a statistically significant decline in intraarticular knee temperature with the application of ice and compression to the skin. The mechanism by which cryotherapy acts must therefore include the cooling effect on the intraarticular environment and synovium.

Stem pressure at the origin of intracranial collateral vessels.

The relationship between pressure at the functional site of origin of intracranial collateral channels (Pstem) and systemic pressure allows an estimation of the size of vascular channels from which collateral vessels originate. In this study, Pstem was determined in anesthetized dogs. A branch of the middle cerebral artery was perfused through a closed system with autologous blood. Tissues with regional cerebral blood flow (rCBF) less than or equal to 10 ml.100 g-1.min-1 (collateral-dependent zone) were identified using radioactive microspheres. Sequential injections of nonradioactive microspheres were made into the cannulated vessel to progressively occlude the terminal capillary bed. Injection of nonlabeled spheres was terminated when backpressure no longer increased, and the final rCBF measurement was made. There was a linear relationship between backpressure and flow to the collateral-dependent tissues. When rCBF within these tissues was zero, the corresponding value for backpressure (Pstem) was 79 +/- 4% (mean +/- SD) of mean arterial pressure. The high value for Pstem suggests that cerebral collateral channels arise in part from large vessels.

Evaluation of the acute respiratory effects of aerosolized machining fluids in mice.

Using a previously developed bioassay, the sensory and pulmonary irritating properties of a group of 10 aerosolized machining fluids were evaluated in mice. Single, 3-hr inhalation exposures were conducted with the fluids at exposure concentrations ranging from 20 to 2000 mg/m3. The results have shown that all 10 were capable of inducing sensory and pulmonary irritation, with little or no change in pulmonary histopathology. A concentration-response relationship was developed for each fluid which revealed that, for the 10 fluids studied here, the synthetic/semisynthetic and soluble fluids were more potent irritants than the straight oils. Also, 3 of the 10 fluids which had been collected from workplace operations (i.e., "in use" fluids) were found to be similar in potency to the same fluids prior to their introduction into the workplace (i.e., "neat" fluids). From concentration-response relationships, the RD50 value (i.e., concentration inducing a 50% response) was obtained for each of the 10 fluids. The RD50 values ranged from 100 to 1000 mg/m3 for all fluids except the straight oils whose RD50 values were over 100,000 mg/m3. Using these values, exposure limits were then suggested for workers in industry to prevent irritation. This bioassay may be a good first step in evaluating new machining fluids whose formulations may change depending upon the current industrial needs.

Studies of collateral perfusion to canine middle cerebral artery territory.

Previous studies of intracranial collateral circulation have not distinguished between true "collateral" blood flow (flow to a region that occurs only when a primary artery is occluded) and "overlap" flow (flow to a region that is present under both normal and demand conditions). These experiments had three purposes: 1) to identify tissues that were truly collateral dependent, 2) to determine potential for true collateral flow in the absence of overlap flow, and 3) to determine whether an anatomical basis for overlap flow could be demonstrated. Branches (700-900 microns) of the dog middle cerebral artery (MCA) were perfused with autologous blood. The perfused region, which was the area at risk, was identified by intravenous injection of neutral red dye. Microspheres were used to measure regional cerebral blood flow (rCBF). Overlap flow was determined by perfusion of the artery with microsphere-free blood. True collateral flow (total rCBF minus overlap flow) was determined by analysis of rCBF to the risk area after cessation of vessel perfusion. Most of the risk area had substantial levels of overlap flow (about one-third of base line). In the center of the area at risk, the true collateral-dependent area was identified [mean overlap flow 4 +/- 1 (mean +/- SE) ml.min-1.100 g-1], which had high levels of perfusion from collateral vessels (102 +/- 14) within 30 s of vascular occlusion. Microfil injection into two adjacent MCA branches showed discrete borders between vascular territories, with no overlapping vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of cervical spine injuries in patients with ankylosing spondylitis.

Eleven patients with ankylosing spondylitis and traumatic fracture/dislocation of the spine were identified in a retrospective review of all cases of cervical spine injury treated on the neurosurgical service over a 10-year period. Injury was most often secondary to minor trauma or a motor-vehicle accident, and the level of vertebral involvement was most frequently between C-5 and T-1. Neurological symptoms at presentation ranged from neck pain alone to complete loss of function distal to the level of injury. Initial routine treatment consisted of axial traction for realignment with the minimal weight needed to accomplish this, taking into account the flexion deformity. All patients underwent pluridirectional tomography and/or computerized tomography to delineate the exact sites of injury. Three patients died shortly after admission due to pulmonary complications. The remaining eight patients underwent early posterior stabilization and mobilization in a halo or cervicothoracic brace to achieve fusion. Neurological improvement was achieved in six of these eight cases. The experience described here supports the initiation of axial traction as initial therapy for cervical injuries followed by early surgical stabilization in patients with ankylosing spondylitis. The difficulty of maintaining spinal alignment and the devastating pulmonary problems attendant on conservative management may be obviated by early fusion.

Alteration of respiratory cycle timing by propranolol.

The present study was undertaken to explore the effect of propranolol on respiratory cycle timing and breathing pattern using mice and guinea pigs. Propranolol was administered via aerosol or via injection. Mice exposed to propranolol aerosols exhibited a breathing pattern that was characterized by a pause between breaths. The length of such pauses (TP) increased as the propranolol exposure concentration was raised. We also observed at increasing propranolol concentrations that the time of inspiration (TI) and time of expiration (TE) decreased. Thus, the respiratory rate of these animals was seen to increase, remain unchanged, or decrease depending on the balance between TP versus TI and TE. Guinea pigs also exhibited pauses between breaths during exposure to propranolol aerosols, but such pauses were not observed as consistently as in mice. TP again rose while TI and TE fell in guinea pigs exposed to increasing propranolol concentrations. This species was, however, less sensitive than mice. Intraperitoneal injections of propranolol failed to elicit such alterations in respiratory pattern or timing in either species. These changes in respiratory timing obtained with an aerosol of propranolol were most probably due to a local effect on vagal nerve endings or to its bronchoconstricting effect.

Cerebral autoregulation following prophylactic and delayed experimental STA-MCA bypass.

Cerebral autoregulation is impaired in ischaemic regions. We hypothesized that pre-existing STA-MCA bypass would be superior to delayed revascularization in maintaining ipsilateral rCBF and preserving cerebral autoregulation following experimental stroke. Two series of dogs were tested to evaluate this hypothesis, but which was disproved for the chosen experimental conditions. In the first, eight dogs underwent craniotomy, STA-MCA bypass, and radiolabeled microsphere rCBF determinations. Blood pressure was manipulated with intravenous adenosine and levarterenol. Ischaemic zone rCBF was measured at MAP 60 mm Hg (97.2 ml.min-1.100 g-1) and MAP 140 mm Hg (113.6) (p = NS), in the intact arterial system with the patent bypass in place. An hemispheric ipsilateral ischaemic lesion was then created, and three further microsphere rCBF determinations were made at MAP 60 mm Hg (41.7 ml.min-1.100 g-1), MAP 100 mm Hg (52.6) and MAP 140 mm Hg (58.3). There were no significant differences between these measurements (ANOVA p = NS). In a second series of five animals the bypass was placed and the stroke lesion created first. Ischaemic zone rCBF was then measured at MAP 60 mm Hg (35 ml.min-1 . 100 g-1) and MAP 140 mm Hg (44 ml.min-1 . 100g-1) (p = NS), with the patent bypass in place. The bypass was then clamped for 15 minutes and profound ischaemia confirmed (5 ml.min-1 . 100 g-1, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Pseudoaneurysm of the extracranial vertebral artery. Case report.

The unusual association of a giant extracranial vertebral artery pseudoaneurysm, intracranial aneurysms, and extracranial carotid occlusion in a woman with neurofibromatosis is presented. Pain as a result of expansion of the mass in the soft tissue of the neck led to her seeking evaluation. Herniation of the mass intraspinally between the occiput and C-1 resulted in myelopathy. Following balloon occlusion of the vertebral artery, the mass and associated symptoms resolved without the need for direct resection. The salient features of these unusually associated problems are discussed.