Blood trauma in plastic haemodialysis cannulae

To investigate the haemolysis in haemodialysis cannulae, an in-vitro set up is built, using a unipuncture dialysis system. This system is connected to a bag with fresh calf's blood, by the cannula under test, mounted in a large bloodline (5 mm diameter). The blood characteristics are kept constant by means of a bicarbonate dialysate in the dialyser. During a 6 h period, haematological parameters are regularly samples. Flow through the cannulae is recorded, which is about 500 mL/min. Four different cannulae are tested and compared to the results obtained without any cannula in the circuit. In all cases a linear increase in plasma free haemoglobin levels is found after 6 h. The cannulae can be ranked from 8F catheter over 13G, 14G to 16G cannula, the latter producing the highest degree of haemolysis. When using plastic cannulae at high blood flows, their haemolytic effect may not be neglected.     

Hydrodynamical comparison of aortic arch cannulae

The high velocity of blood flow exiting aortic arch cannulae may erode atherosclerotic material from the aortic intima causing non-cardiac complications such as stroke, multiple organ failure and death. Five 24 Fr cannulae from the Sarns product line (straight open tip, angled open tip with and without round side holes, straight and angled closed tip with four rectangular, lateral side holes), and a flexible cannula used at the University Hospital of Gent (straight open tip) are compared in an in vitro steady flow setup, to study the spatial velocity distribution inside the jet. The setup consists of an ultrasound Doppler velocimeter, mounted opposite to the cannula tip in an outflow reservoir. An elevated supply tank supplies steady flow of 1.3 L/min of water. Exit forces at various distances from the tip are calculated by integrating the assessed velocity profiles. The pressure drop across the cannula tip is measured using fluid filled pressure transducers. The four sidehole design provides the lowest exit velocity (0.85 versus 1.08 m/s) and force per jet (0.03 vs 0.15-0.20 N). The round sideholes are useless as less than 1% of the flow is directed through them. Furthermore, the use of angled tip cannulae is suggested because the force exerted on the aortic wall decreases the more the angle of incidence of the jet deviates from 90 degrees. Pressure drop is the lowest for the 4 side hole design and highest for the open tip and increases when an angled tip is used.     

An analysis of the effect of venous resistance on the performance of gravity-fed intravenous infusion systems

OBJECTIVE: Our objective was to assess the effect of venous resistance in a clinically relevant range on flow rates through intravenous (i.v.) cannulae. METHODS: Since resistances in series are additive, the sum of the resistance of the i.v. cannula and the vein equates to the total resistance to flow. Using resistance data from earlier work, the total resistance for various combinations of cannula and vein size was calculated, allowing a prediction to be made of the comparative flow rates between these combinations for a given driving pressure. Next, the clinical situation was simulated by measuring flow rates through i.v. cannulae connected in series to a variety of infusion devices with resistances known to be within the range of clinically relevant venous resistance. RESULTS: The effect of venous resistance was greatest on large-bore cannulae, with significant reductions in flow occurring when even low levels of venous resistance were added. Throughout much of the range of venous resistances encountered clinically, total flows through two small-gauge cannulae exceeded that through a single large-gauge cannula. CONCLUSION: To achieve maximum benefit from a large-bore cannula, a suitably large vein must be chosen. Further, where venous access is difficult and high flow potential from an infusion system is required, two separate infusions through small cannulae may be a preferable option to a single large bore.     

Characterization and specificity of B-cell responses in lupus induced by Mycobacterium bovis in NOD/Lt mice

BACKGROUND: Endoscopic treatment of postoperative benign bile duct strictures (BBDS) is technically challenging, and the long-term outcome after stricture dilation remains poorly defined. METHODS: Forty-eight cases of postoperative BBDS with attempted endoscopic treatment (either transient plastic stenting or definitive metal stent insertion) were reviewed. RESULTS: Endoscopic stricture dilation succeeded in 47 of 48 cases (98%). No procedure-related mortality was observed; 16 (33%) procedure-related or stent-associated complications were observed during treatment. Endoscopic treatment was interrupted in five patients. Stricture relapse occurred in 6 of 6 (100%) and 7 of 36 (19%) patients after metal stent insertion and plastic stent removal, respectively (p < 0.001) (mean follow-up periods 50+/-12 and 44+/-34 months, respectively). After plastic stent removal, stricture relapses were more frequent among patients with strictures related to liver transplantation as opposed to other surgical procedures (p < 0.05); these recurrent strictures were successfully treated by repeated insertion of plastic stents on a temporary basis. At the end of follow-up, all but one patient treated with plastic stents had normal serum alkaline phosphatase values. CONCLUSION: Metal stents proved to be inadequate for treating postoperative BBDS. Temporary insertion of a plastic stent (possibly repeated) provided long-term results equal or superior to those reported for surgical biliary drainage. Repeated insertion of plastic stents was more frequently indicated for strictures related to liver transplantation compared with other surgical procedures.     

Quantitative evaluation of flow patterns in perfusion cannulae by a new magnetic resonance imaging method

The arterial cannula is a critical part of any extracorporeal circulation system due to the high flow rates which must pass a small cross-sectional area, resulting in high blood velocities. The aim of this study was to examine whether high-field magnetic resonance scanning is applicable for detailed mapping of velocity fields around the tip of such arterial cannulae in vitro. The investigated cannula was an angled, open-tip traditional design aortic cannula with an internal tip diameter of 5.5 mm. The velocity fields were measured at two different flow rates (2 and 4 l/min) at various positions in the lumen and outside the cannula using magnetic resonance imaging (MRI). All three components of the velocity vectors were measured. The study showed that MRI can provide a clear quantitative visualization of the velocity field around the tip of arterial cannulae at lower flow rates. At higher flow rates it can provide information about localization of regions with turbulent or disturbed flow.     

Evaluation of two commercially available carbon dioxide sampling nasal cannulae

Our study compared two commercially available carbon dioxide sampling nasal cannulae for efficacy of oxygenation and relationship of end-tidal carbon dioxide (PETCO2) to arterial carbon dioxide (PaCO2). The two-prong nasal cannula (2PNC) has one prong dedicated to delivering O2 via one naris and the second prong dedicated to sampling exhaled gases via the other naris. The four-prong nasal cannula (4PNC) delivers O2 via a prong in each naris, and samples exhaled gases via another set of prongs in each naris. Forty six patients were divided into three groups, which received either 2 (n = 15), 3 (n = 16), or 4 (n = 15) L/min O2, respectively, and were studied sequentially with standard nasal cannula (SNC), the 2PNC, and then the 4PNC. At each O2 flow rate, PaO2 was equivalent regardless of whether the SNC, 2PNC, or 4PNC was used. Seventy-four percent (34/46) of the 2PNC and 0% (0/46) of the 4PNC PETCO2 values were within +/- 4 torr of the PaCO2 value. The authors conclude that the 2PNC and 4PNC are equally effective compared with an SNC in oxygenating patients, but the PETCO2 measured by the 2PNC provides a superior quantitative estimate of the PaCO2 than that obtained by the 4PNC.     

Palliative treatment of malignant esophageal stenosis: experience with plastic versus metal stents

BACKGROUND/AIMS: We report on the palliative treatment of 44 patients with malignant dysphagia by placement of plastic (Celestin tubes, n = 24) vs metal stents (Wall stents, Nitinol stents, Gianturco stents, n = 20). METHODOLOGY: Prior to stent insertion, esophageal stenosis was dilated stepwise to 16 mm (plastic tube) and to 10 mm (metal stent). RESULTS: Stent insertion was technically successful in all cases and led to a reduction of dysphagia. Risk of perforation was comparable in both groups (n = 1 in each group). Most of the plastic stents were placed when the tumor was localized in the proximal part of the esophagus close to the upper esophageal sphincter, when esophageal-bronchial fistula was present and in the risk of fistula development after radiation. During follow-up, tumor ingrowth (TI) and stent migration (SM) were the major complications. Whereas tumor ingrowth predominantly occurred in metal stents (TI after 6 weeks, 45% vs. SM, 10%) that required repeated argon beamer therapy, tube migration and bolus impaction (BI) often occurred in patients with plastic stents (TI, 0% vs. SM, 16%; BI, 4%). CONCLUSIONS: The findings of the study suggest that the decision whether plastic tubes or metal stents used should be taken individually considering tumor localization, axis deviation and the presence of esophago-respiratory fistulas. When stepwise dilation of malignant stenoses is performed carefully, perforation risk appears not to be different between placement of plastic prostheses and metal stents.     

Cervical ECMO cannula placement in infants and children: recommendations for assessment of adequate positioning and function

BACKGROUND/PURPOSE: Cervical extracorporeal membrane oxygenation (ECMO) cannula position is often difficult to confirm by chest x-ray alone. Malposition requires a second surgery to rectify the problem. Reoperation places the patient at risk for infection, bleeding, or death. This study analyzes indications for cannula repositioning and suggests an alternative standard for intraoperative evaluation of catheter function as it relates to position. METHODS: The authors reviewed charts of 73 patients placed on arterio-venous ECMO through cervical vascular access. Reasons for repositioning of either cannula at the initial surgery or postoperatively were recorded. RESULTS: Of 73 patients, 18 (24.6%) required either arterial cannula or venous cannula repositioning. In 10 (55%) of these patients, cannula malposition was not detected by chest x-ray during the initial cannulation, and they therefore required a second cervical exploration for repositioning. CONCLUSIONS: Chest x-ray is not sensitive in demonstrating malpositioned cervical ECMO cannulae. Two-dimensional ECHO before wound closure, may be a superior, more cost effective means of assessing cannula placement and function than x-ray alone. Confirmation of cannula position and function, before wound closure, would reduce the risks involved with cervical reexploration.     

Translaryngeal tracheostomy. A new era?

OBJECTIVE: Presentation of a new technique of dilation tracheostomy projected to offer a minimum risk of complication and tissue trauma. DESIGN: Prospective study carried out between July 1993 and December 1995, to evaluate the feasibility of the procedure, its possible advantages over other methods, and possible complications. SETTING: General ICU with a Paediatrics Section. PATIENTS: Uninterrupted series of 84 adults and 12 children with multifactorial respiratory insufficiency. INTERVENTION: Through a needle inserted in the trachea, a guide wire is retrogradely pushed out of the mouth and attached to a special device formed by a flexible plastic cone with pointed metal tip joined to an armoured tracheal cannula. This device is then pulled back through the oral cavity, larynx, trachea-hence the definition: TransLaryngeal Tracheostomy (TLT)- and outwards across the neck wall by applying traction on the wire with one hand and counterpressure on the neck wall with the fingers of the operator's other hand. When the cone and part of the cannula have emerged, the cone is separated from the cannula. The cannula is further extracted until its inside portion can be turned downwards to its final placement. RESULTS: A precise localisation of the stoma placement and the needle introduction are facilitated by the rigid tracheoscope and protrusion. Thanks to the very pointed cone, the piercing resistances are lowered. At the same time, every degree of traction power is allowed through the counterpressure practised by the fingers. The channel is very regular with a strong adherence to the cannula that secures a virtual lack of bleeding and local inflammation. We observed this in the fifty cases, in which the final version of our technique was applied. Trachea CT scan and endoscopic control did not show late lesions of the airway. CONCLUSIONS: TLT is characterised by highest inherent safety and lowest tissue traumatism, that it can also be performed in patients who would risk complications from any other tracheostomy techniques.     

Port site electrosurgical (diathermy) burns during surgical laparoscopy

BACKGROUND: Direct and capacitive coupling of diathermy current have been reported as causes of occult injury during surgical laparoscopy. METHODS: In order to determine the incidence of electrosurgical injury adjacent to metal and plastic cannulas, skin biopsies at 19 port sites used for monopolar electrosurgery were analyzed for coagulative necrosis. Prior to surgery the cannulas were randomized to either metal or plastic. RESULTS: Coagulative necrosis was observed at nine electrosurgery port sites compared to only one control (chi2 = 4.872; df = 1; 0.05 > p > 0.02). Plastic cannulas afforded no greater protection from skin burns than metal cannulas. CONCLUSIONS: Burns may be the result of direct or capacitive coupling to metal cannulas or capacitive coupling to the skin edge across plastic cannulas. The potential exists for burns to other tissues also in close proximity to a cannula used for electrosurgery.     

Long-term estrogenization in mammals. II. Environmental influences of housing conditions upon estrogen-induced polydipsia and food intake in Marsh mice

Estrogen-induced polydipsia was influenced by environmental conditions in which Marsh mice were housed in plastic cages with bedding or in metal cages having grilled floors and no bedding. Increases in this polydipsia with metal-cage housing were reversed upon return to plastic. The increases over controls as ml/kg body weight ranged from 40 to 250%. After an initial fall in food consumption following estrogenization, controls and estrogenized mice consumed nearly the same amount of food/mouse but 10% more for the estrogenized mice on a g/kg body-weight basis. Increased food consumption for controls and estrogenized mice following the change from plastic to metal cages was attributed to compensation for increased loss of body heat. Whether in plastic or metal cages, core temperatures of controls were higher than those of estrogenized mice; both groups had relatively higher temperatures in the metal cages. The older mice in metal cages developed a gnawing pattern wasting food. In five experiments with males, body-weight losses following estrogenization were maintained 43 to 70 days but recovered in 2 of 4 experiments with females under comparable conditions.     

Serum hepatitis G virus (HGV) RNA in multitransfused thalassemics from eastern Sicily

To evaluate the efficacy of continuous administration of 50% nitrous oxide in oxygen for reducing pain during flexible fiberoptic bronchoscopy 32 children aged 3-60 months were randomly assigned to an experimental or a control group. Indications for endoscopy included persistent atelectasis (6), wheezing (10) cystic fibrosis (2) pneumonia (11) persistent cough (3). All patients received Midazolam (0.3 mg/kg) atropine (20 mcg/kg) intra rectaly 20 minutes before the procedure. The flexible fiberoptic bronchoscope (Olympus BF3C4) was inserted transnasally through a face mask. Topical anesthesia with 1% lidocaine hydrochloride (3 mg/kg) was applied to the nose, larynx, trachea and bronchial tree over 15 minutes through the suction chanel of the bronchoscope. All patients were monitored with a pulse oximeter and a cardiac monitor. The experimental group (n = 16) received 50% nitrous oxide in oxygen prior (3 minutes) and during flexible fiberoptic bronchoscopy, the control group (n = 16) received only oxygen. We measured pain of the children by a behavioral observation scale (Children's Hospital of Eastern Ontario Pain Scale: CHEOPS) at each phase of topical anesthesia during bronchoscopy in the two groups. At the end of bronchoscopy physician's satisfaction was scored by a visual analogue scale (VAS 0-100) in which 0 corresponded to absence of satisfaction. Nitrous oxide was associated with lesser pain scores than those with oxygen. Physician significantly preferred these procedure compared with oxygen. No complication occurred during procedure. Combined with local anesthesia midazolam and atropin the administration of 50% nitrous oxide in oxygen seems a better choice for flexible fiberoptic bronchoscopy in children and should be used routinely.     

Respiratory distress in newborn: treated with ventilation in a level II nursery

The ClearView Uterine Manipulator was compared with the Cohen acorn-tipped cannula for efficacy and safety in patients undergoing laparoscopy at the University of Utah Medical Center. Fifty consecutive patients were randomized by computer to have either the ClearView instrument or the Cohen cannula used as a uterine manipulator (25 patients each). The ClearView manipulator was statistically superior to the Cohen cannula for range of motion in the anterior and posterior sagittal plane (p <0.0001). The Cohen cannula was consistently inserted in less time (p <0.02). There was no statistically significant difference between the instruments in ease of uterine manipulation, ease of dye instillation, percentage of dye leakage from the cervix, overall ease of use, ease of device insertion, and ease of device removal. Two cervical perforations occurred during cervical dilatation in the ClearView manipulator group in patients with cervical stenosis requiring dilatation with metal dilators (os <2 mm). No patients in the Cohen cannula group had cervical stenosis. In that group two cervical lacerations occurred requiring suture ligation. The ClearView instrument provides a greater range of motion, does not require an assistant to maintain uterine position, and allows manipulation without a cervical tenaculum. Its insertion occasionally (36%) required tenaculum placement, uterine sounding, and cervical dilatation, increasing the time of insertion compared with placement of the Cohen cannula. In patients with cervical stenosis, use of a uterine sound and cervical dilatation increase the risk of perforation.     

Population based randomized study of uptake and yield of screening by flexible sigmoidoscopy compared with screening by faecal occult blood testing

OBJECTIVES: To compare the feasibility of mass screening by flexible sigmoidoscopy with screening by faecal occult blood testing (Haemoccult) and both tests combined. DESIGN: Patients were randomised to screening by flexible sigmoidoscopy, faecal blood testing, or both tests. The flexible sigmoidoscopy examinations were performed by a general practitioner. SETTING: General practice. SUBJECTS: 3744 patients aged 50-75 years. Main outcome measures: Uptake, positive results, detection of neoplasia, complications, and recall for diagnostic colonoscopy. RESULTS: Uptake was significantly higher in the flexible sigmoidoscopy group (46.6%) than in the faecal blood test group (31.6%; P<0.001) or than in the group having both tests (30.1%; P<0.001). Telephone reminders increased uptake of sigmoidoscopy to 61.8%. In total, 1116 sigmoidoscopy examinations were performed without major complication. Polyps were found in 19. 3% (95% confidence interval 17.0% to 21.6%) but only 6.8% (5.3% to 8. 3%) had adenomas and 2.4% (1.5% to 3.3%) "high risk" adenomas. Cancer was detected in four subjects. The faecal blood test yielded positive results in 0.8% (0.2% to 1.4%) but missed at least one cancer and 30 cases of adenoma which were found by sigmoidoscopy in the combined group. Use of histological criteria-shown elsewhere to correlate with future risk of colorectal cancer-to select "positive" patients could reduce recall for diagnostic colonoscopy from about 20% to less than 5%. CONCLUSIONS: Some of the predicted obstacles to screening with flexible sigmoidoscopy are surmountable. Clear evidence relating to efficacy will be obtained only from a randomised controlled trial.     

Effect of xylazine and ketamine on blood pressure, heart rate and respiratory rate in rabbits

New Zealand white and New Zeland white-Dutch Belted cross rabbits of both sexes were anesthetized using xylazine and ketamine alone and in combination while blood pressure, heart and respiratory rates were monitored. Blood pressure effects were measured from the aortic arch by a cannula implant through the left carotid artery. Ketamine-xylazine in combination at 35 and 5 mg/kg body weight, respectively, produced 45-60 minutes of surgical plane anesthesia. Anesthesia was induced in approximately 10 minutes. The average initial blood pressure drop was complete in 10 minutes and was 30%. Heart and respiratory rates dropped 19% and 77%, respectively, in the same time span. An additional blood pressure drop of 6-7% occurred as consciousness was regained. Blood pressure recovery was nearly complete (normal) about 6 hours following injection of the drug combination.     

The influence of the impression tray on the accuracy of impressions for crown and bridge work--an investigation and review

OBJECTIVE: To evaluate the accuracy of working casts for crown and bridge restorations made from twin mix putty/wash silicone elastomeric impression materials using different types of stock tray. DESIGN: A master cast was made from ivorine teeth in a mandibular model. Three teeth were prepared for full crown restorations to simulate a single unit and a three unit bridge. Impressions were taken using four different types of impression tray and two different viscosities of silicone putty, together with a wash. Full metal crowns were constructed and seated on duplicate master casts and measurements made of the marginal discrepancies. SETTING: The work was carried out in a dental technology laboratory in a university department of restorative dentistry in 1995/1996. RESULTS: Metal and rigid plastic impression trays showed the least discrepancy (about 50 microns), the latter slightly greater with the normal putty than the soft one. Impressions taken with flexible plastic trays produced considerable discrepancy with both putties, approximately 210 microns and 180 microns respectively. CONCLUSIONS: Metal and rigid plastic stock trays give greater accuracy in the putty/wash silicone twin mix impression technique compared with flexible plastic ones for crown and bridge work. Those using the latter should be aware of their shortcoming in this respect.     

Surgical outcome and cost-minimisation-analyses of laparoscopic and open hernia repair: a randomised prospective trial with one year follow up

OBJECTIVE: To compare outcome and costs between laparoscopic and open hernia repair. DESIGN: Prospective randomised study. SETTING: One university and two district hospitals in Sweden. SUBJECTS: 200 men aged 25-75 years. MAIN OUTCOME MEASURES: Operating time, hospital stay, complications, and time to recovery. A cost-minimisation-analysis was used in which the total costs were calculated for a defined period of time for each option. RESULT: The one year follow-up rate was 98%. Mean (SD) operation times in the laparoscopic and open groups were 72 (30) and 62 (25) minutes, respectively (p = 0.009). Hospital stay and complication rates did not differ between the groups. Among employees the mean (SD) periods off work in the laparoscopic and open groups were 10 (8) and 23 (21) days, respectively (p = 0.0001). The mean direct costs of the laparoscopic operation were increased by SEK 4037 (US$ 483) but the savings in indirect costs resulting from earlier return to work were SEK 11392 (US$ 1364). CONCLUSIONS: Laparoscopic hernia repair gave the employed patients faster recovery and return to work, and was the most cost-effective strategy provided that both direct and indirect costs were included.     

Day surgery for cervical microdiscectomy: is it safe and effective?

The objective of this pilot study was to evaluate the safety and efficacy of cervical discectomy with fusion performed on an outpatient basis. The experimental group (50 consecutive patients) was studied prospectively and the outcomes were compared with 53 consecutive, retrospectively analyzed, admitted controls who underwent the same procedure. Outcomes for both groups were assessed by patient-response questionnaires and clinical examination. At follow-up times of 1.3 (outpatient) and 1.6 (inpatient) years, outcomes (outpatient/inpatient) expressed as percent successful were as follows: Relief of arm pain (80/70%); relief of neck pain (78/68%); relief of arm muscle weakness and atrophy (94/96%); return to normal activities (64/70%); return to work (65/68%); and satisfaction with the results of surgery (86/83%). No statistically significant differences between outpatients and inpatients were found for any of the outcome parameters studied. There was no mortality and the operative complication rate was 2% for each study group. The results indicate that conversion of cervical discectomy with fusion from an admitted to an ambulatory practice did not compromise the safety or efficacy of the surgical procedure. Potential economic savings to overall health costs of the United States that might result from such conversion could exceed $100 million annually.     

A randomized trial of 2 regimens for the administration of vaginal prostaglandins (gemeprost) for the induction of midtrimester abortion

The most frequently used method for second trimester termination of pregnancy is administration of gemeprost (16, 16-dimethyl-trans delta 2-prostaglandin E1methyl ester) as a vaginal pessary. This provides a safe and effective method for achieving abortion. The current prescribing advice is to insert the pessaries into the posterior vaginal fornix every 3 hours. This study compares this to a 6-hourly regimen. The median abortion interval in the 6-hour group was shorter than the 3-hour group (15 versus 16 hours respectively) but the cumulative abortion rates were similar (98% in the 3-hour group and 91.8% in the 6-hour group). The 6-hour group required a significantly lower total dose of gemeprost to induce abortion. There was no difference in the rates of side-effects in the 2 groups but those receiving pessaries every 6 hours required less analgesia. This study finds no advantage in giving gemeprost every 3 hours.     

Clinical analysis of two-level compression of the cauda equina and the nerve roots in lumbar spinal canal stenosis

STUDY DESIGN: This study is a prospective, clinical study assessing the efficacy of selective decompression of the responsible level in two-level stenosis in accordance with neurologic findings defined by the gait load test, and functional diagnosis based on selective nerve root block. OBJECTIVE: To clarify the clinical features of two-level stenosis regarding the neurologic level responsible for the symptoms, neurogenic intermittent claudication, and the outcome of selective decompression. SUMMARY OF BACKGROUND DATA: Experimental studies have indicated that double-level compression of the cauda equina induces a more severe impairment of nerve function than does single-level compression. However, few studies have focused on the clinical importance of two-level stenosis. The clinical effects of two-level stenosis on the cauda equina and nerve roots are unknown. METHODS: A total of 81 patients with lumbar spinal canal stenosis due to spondylosis and degenerative spondylolisthesis were divided into two groups, two-level stenosis at L3-L4 and L4-L5, and one-level stenosis at L4-L5, based on myelography. The types of neurogenic intermittent claudication, the level responsible for neurologic findings, and the postsurgical outcome were compared between both groups. The level responsible for the symptoms in two-level stenosis was determined in accordance with neurologic findings on the gait load test and functional diagnosis based on a selective nerve root block. All patients underwent a prospective, selective decompression at the neurologically responsible level only. The average follow-up period was 4.6 years (range, 1-8 years). RESULTS: The patients with two-level stenosis more frequently had cauda equina symptoms than those with one-level stenosis, except patients with degenerative spondylolisthesis. It was therefore assumed that two-level stenosis was associated with cauda equina impairment, Changes in neurologic condition before and after the gait test were observed in four patients with two-level stenosis. Finally, for 28 patients with two-level stenosis, the levels responsible for the neurologic symptoms were the caudal level (L4-L5) in 22 patients, the cranial level (L3-L4) in 1 patient, and both cranial and caudal levels (L3-L4 and L4-L5) in 5 patients. All stenotic levels on the myelogram were not always symptomatic in two-level stenosis. However, in one-level stenosis, all of the responsible levels completely corresponded to the myelogram. Selective decompression only at the neurologically responsible level improved neurogenic intermittent claudication in all patients. The asymptomatic levels at which the stenotic condition was left unchanged at surgery did not become symptomatic at follow-up; in addition, there was no significant difference in the postoperative outcome between two-level stenosis and one-level stenosis. CONCLUSIONS: Two-level stenosis in patients with lumbar spondylosis is associated with production of cauda equina lesions. The gait load test provides information regarding changes in symptoms and neurologic condition during exercise. The responsible levels should be determined based on neurologic findings after the gait load test and a selective nerve root block. It is uncommon for both stenotic levels to be symptomatic in patients with two-level stenosis. Less invasive surgery such as selective decompression for the responsible level in patients with two-level stenosis is a useful technique with a good potential for long-term success.