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Biomedical subjects

R Ludemann

Publications and source records attributed to R Ludemann.

13 recordsLinked to original sources
PubMed2003

Pneumothorax during laparoscopy.

BACKGROUND: Pneumothorax is a known complication of laparoscopy, with most pneumothoraces diagnosed postoperatively with conventional chest x-ray. Electrocardiogram (ECG) conduction changes are associated with pneumothorax. In a sheep model, ECG changes were evaluated as a potential indicator of intraoperative pneumothorax. Additionally, resolution rates of helium (He) and carbon dioxide (CO2) pneumothorax were also evaluated in this model. METHODS: Under general anesthesia, 10 sheep had known volumes (20-100 cc) of either He or CO2 introduced into the left hemithorax. A 12-lead ECG recorded changes associated with the induced pneumothorax. After changes in the ECG plateaued, the gas volume in the hemithorax was increased to 2 L and the resultant pneumothorax was followed for a 2-h period using fluoroscopy to determine resolution rates for the different gas pneumothoraces. Gas volumes were aspirated after 2 h and ECGs were again recorded. RESULTS: Pneumothorax volumes as low as 20 cc produced consistent ECG changes. The amplitude of the precordial QRS complex was seen to diminish, and this lowering of the QRS amplitude continued as pneumothorax volume increased up to 100 cc. The ECG returned to prepneumothorax patterns with aspiration of the left chest. For different gas pneumothoraces, CO(2) pneumothorax showed almost complete resolution in the 2-h period, whereas He pneumothorax was unchanged. CONCLUSIONS: Precordial ECG changes appear to be a very sensitive indicator of pneumothorax, with very small pneumothorax (<100 cc) consistently being detected by reduction of the QRS complex amplitude. Intraoperative use of precordial ECG leads could result in rapid identification of pneumothorax during laparoscopic surgery. Carbon dioxide pneumothorax shows near 100% resolution in a 2-h period. This supports recommendations of expectant management in asymptomatic patients with CO(2) pneumothorax. However, He pneumothorax does not resolve spontaneously quickly and may require aspiration even in asymptomatic patients.

Absorption↗
PubMed2001

[Laparoscopic aortic surgery in a swine model using a newly designed intestine retraction system].

BACKGROUND: Recently, the feasibility of laparoscopic surgery for aortic occlusive and aneurysmal disease has been demonstrated in clinical studies. However, aortic access is compromised by poor exposure of the operative field from uncontrolled bowel. Currently available retractors are inadequate. The development of new retracting instruments therefore may facilitate laparoscopic aortic surgery. METHODS: Two paddles inserted in a polyester bilayer (mobile device, group A) or a mesh net fixed to the abdominal wall (fixed device, group B) were used to retain the bowel. Six female piglets (28-30 kg) in each group underwent laparoscopic aortic surgery. RESULTS: Mean time to deploy the device was 22 +/- 12 min in group A and 36 +/- 34 min in group B (n.s.). Vascular surgery time averaged 60 +/- 24 min in group A and 68 +/- 16 min in group B (n.s.), the time to withdraw the nets was respectively 3.6 +/- 1.2 min and 13.5 +/- 8.2 min (p < 0.05). Total surgery time was 155 +/- 41 min vs. 174 +/- 49 min (n.s.). Two retraction failures have been registered (1 in group A and 1 in group B). No major complications were documented. CONCLUSIONS: Both nets provided adequate exposure of the infrarenal aorta. Vascular surgery time and blood loss were similar in both groups. Nevertheless, the handling of the mobile device (group A) seemed to be more comfortable in direct comparison. The newly developed retraction devices might facilitate the performance of laparoscopic aortic surgery.

Animals↗
PubMed2000

Newly designed retraction devices for intestine control during laparoscopic aortic surgery: a comparative study in an animal model.

BACKGROUND: Recent clinical studies have demonstrated the feasibility of laparoscopic surgery for aortic occlusive and aneurysmal disease. However, transperitoneal aortic access is compromised by poor exposure in the operative field from uncontrolled bowel. The retractors that are currently available are inadequate for this task. The development of new retractors would help to facilitate laparoscopic aortic surgery. METHODS: Six female piglets (28-30 kg) in each group underwent laparoscopy with pneumoperitoneum (12 mmHg). Exposure of the infrarenal aorta and cross-clamping were undertaken through a transperitoneal approach. Two paddles inserted in a polyester bilayer (mobile device, group A) or a mesh net fixed to the abdominal wall (fixed device, group B) were used to retain the bowel. Aortotomy and suturing were performed to mimic a vascular procedure. After bleeding was controlled, the intraabdominal pressure (IAP) was lowered to 6 mmHg, and retraction was assessed for 30 min. The main outcome measures were time to deploy the retractors, time to perform the vascular procedure, time to withdraw the devices, and total procedural time. Blood loss and frequency of retraction failure were also recorded. RESULTS: Mean time to deploy the device was 22 +/- 12 min in group A and 36 +/- 34 min in group B (n.s.). Vascular surgery time averaged 60 +/- 24 min in group A and 68 +/- 16 min in group B (n.s.). The times to withdraw the nets were 3.6 +/- 1.2 min and 13.5 +/- 8.2 min, respectively (p < 0.05). Total surgery time was 155 +/- 41 min vs 174 +/- 49 min (n.s.). There were six retraction failures, five in group A and one in group B. When lower IAP was used, there was only one failure in each study group. Mean blood loss was <150 ml in both groups. There were no major complications. CONCLUSIONS: Both methods provided adequate exposure of the infrarenal aorta. Vascular surgery time and blood loss were similar for both groups. The movable device proved more usable and, at lower IAP, more effective. The results of this study demonstrate effective bowel retraction for laparoscopic aortic surgery.

Animals↗
PubMed1999

Totally laparoscopic abdominal aortic aneurysm repair.

Current experience with totally laparoscopic aortic aneurysm repair is reviewed with particular attention to the techniques of surgery. Vascular surgery has been slow to enter the field of minimally invasive surgery because of the unique difficulties of managing arterial anatomy with minimal access techniques. Laparoscopic instrumentation has undergone a stunning evolution, and surgeon experience with minimally invasive surgery has grown exponentially. This dramatic revolution has allowed several groups to perform laparoscopic aortic vascular surgery. The surgical approach that each group has taken has varied. The approaches have included both laparoscopically assisted and totally laparoscopic aortic surgery with both transperitoneal and retroperitoneal approaches to the aorta. A review of these varied techniques will be discussed and include our experience with totally laparoscopic aortic surgery. This experience includes both transperitoneal and retroperitoneal approaches to infrarenal aortic aneurysms. An extended discussion of our surgical technique for aneurysm bypass is included. Patient selection, patient positioning, and trocar placement are described. The pattern of surgery for both techniques is enumerated, and postoperative care is discussed. However, the world experience with minimally invasive vascular surgery remains small, therefore a wider acceptance will require a prospective, randomized trial that shows an equally as safe surgical approach as provided open vascular surgery. With its acceptance, minimally invasive vascular surgery should show the patient benefits that befall minimally invasive surgery patients.

Aorta, Abdominal↗
PubMed1993

Copurification of casein kinase II with 20 S proteasomes and phosphorylation of a 30-kDa proteasome subunit.

The 20 S proteasome is a multicatalytic protease that has been implicated in several processes including ATP/ubiquitin-dependent proteolysis. However, the ATP requirement(s) related to proteasome function is undefined. We demonstrate that a protein kinase activity copurifies through multiple steps utilized to isolate latent 20 S proteasomes from human erythrocytes. The kinase phosphorylates serine residues within a single 30-kDa proteasome subunit. The activity is not sensitive to cyclic AMP or protein kinase inhibitor, indicating that it is not a cyclic AMP-dependent kinase. It is sensitive to nanomolar levels of heparin and is able to utilize both ATP and GTP as phosphodonors, similar to casein kinase II activity. Moreover, a polyclonal antibody specific for casein kinase II recognizes the alpha' subunit of casein kinase II in the 20 S preparation and specifically immunoprecipitates the proteasome-phosphorylating activity. These characteristics suggest that the proteasome kinase is similar or identical to casein kinase II. It is suggested that phosphorylation of the 30-kDa proteasome subunit by casein kinase II may be involved in regulating the activity and/or assembly of proteasome complexes.

Blotting, Western↗
PubMed1988

Slow to fast alterations in skeletal muscle fibers caused by clenbuterol, a beta 2-receptor agonist.

Chronic treatment of rats with clenbuterol, a beta 2-receptor agonist (8-12 wk), caused hypertrophy of histochemically identified fast- but not slow-twitch fibers within the soleus, while the mean areas of both fiber types were increased in the extensor digitorum longus (EDL). In contrast, treatment with the beta 2-receptor antagonist, butoxamine, reduced fast-twitch fiber size in both muscles. In the solei and to a lesser extent in the EDLs, the ratio of the number of fast- to slow-twitch fibers was increased by clenbuterol, while the opposite was observed with butoxamine. The muscle fiber hypertrophy observed in the EDL was accompanied by parallel increases in maximal tetanic tension and muscle cross-sectional area, while in the solei, progressive increases in rates of force development and relaxation toward values typical of fast-twitch muscles were also observed. Our results suggest a role of beta 2-receptors in regulating muscle fiber type composition as well as growth.

Animals↗
PubMed1987

Clenbuterol, a beta 2-agonist, retards atrophy in denervated muscles.

Denervated soleus, anterior tibialis, and gastrocnemius muscles, but not the extensor digitorum longus, contained 95-110% more protein after 2-3 wk of treatment with the adrenergic beta 2-receptor agonist, clenbuterol, than denervated controls. In addition, the twofold difference in the protein content of denervated solei was paralleled by similar changes in contractile strength and muscle fiber cross-sectional area. In contrast, when the innervated contralateral muscles were examined, the extensor digitorum longus and anterior tibialis showed relatively small increases in protein of 32 and 19%, respectively, whereas the soleus and gastrocnemius were unaffected. The magnitude of the effects of clenbuterol in sparing the mass and functional capacity of denervated muscle suggests that this agent may be important in studies of neuromuscular diseases and disuse atrophy.

Animals↗
PubMed1986

Regulation of Ca2+-dependent protein turnover in skeletal muscle by thyroxine.

Dantrolene, an agent that inhibits Ca2+ mobilization, improved protein balance in skeletal muscle, as thyroid status was increased, by altering rates of protein synthesis and degradation. Thyroxine (T4) caused increases in protein degradation that were blocked by leupeptin, a proteinase inhibitor previously shown to inhibit Ca2+-dependent non-lysosomal proteolysis in these muscles. In addition, T4 abolished sensitivity to the lysosomotropic agent methylamine and the autophagy inhibitor 3-methyladenine, suggesting that T4 inhibits autophagic/lysosomal proteolysis.

Adenine↗
PubMedDate not supplied

Minimally invasive approaches to hepatic surgery.

During the last 10 years we have seen dramatic changes in minimally invasive surgery. Important advancements in videoscopy, instrumentation, and surgical skills have allowed us to perform surgical procedures recently viewed as well outside the domain of minimally invasive surgeon. Solid organ surgery has become common place; in particular, hepatic surgery has been shown to be amenable to minimally invasive techniques. Benign cyst excision, abscess drainage, local tumor ablation, and liver resection are all hepatic procedures described in recent literature. Though it is clear that the trend toward less invasive alternatives towards open liver surgery will continue, proper indications and utilization of such procedures requires careful scrutiny using outcome oriented research. This paper gives a brief overview of the technology available and its application in minimally invasive approaches to liver surgery.

Catheter Ablation↗