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Biomedical subjects

D W Meijer

Publications and source records attributed to D W Meijer.

35 records · Page 2Linked to original sources
PubMed1999

Head-controlled laparoscopy: experiment, prototype, and preliminary results.

Depth perception is closely linked to the ability to explore. Previously described laboratory experiments showed the advantage of linking the motions of the laparoscope directly to the head movements of the surgeon. Additionally, it was found that the laparoscope should be mechanically supported instead of manually (by an assistant). This article describes three stages in the design and evaluation of a practical mechanism with which to link the motions of the laparoscope directly to the head movements of the surgeon. First, a description is given of the perceptual and technical considerations. Second, a laboratory experiment is described investigating the validity of the proposed suggestions. Last, a prototype was built that was tested in a practical setting.

Animals↗
PubMed1999

Manipulation in laparoscopic surgery: overview of impeding effects and supporting aids.

Within a Dutch research program on minimally invasive surgery, a large literature survey has been carried out. This article describes the state of the art in research on manipulation in laparoscopy. It gives an overview of factors impeding the surgeon and technical developments designed to overcome these problems. Starting from the year 1991, a large number of journals, proceedings, patents, and books have been consulted. The survey was completed with a thorough MEDLINE search. The impeding effects have been subdivided into two groups: transformation of spatial and grasping movements of the hand. The article gives an overview of these effects and of supporting aids that have been developed. The studies show that many aids are based on a technology-driven rather than a clinically-driven approach. The development of simple instruments that can be used for a large range of tasks instead of only one is still a very important topic of research.

Ergonomics↗
PubMed1999

Ergonomics and design of laparoscopic instruments: results of a survey among laparoscopic surgeons.

This study determined which types of laparoscopic instruments are most often used in Europe, why they are being used, and what problems exist while using the instruments. The handles were also evaluated according to ergonomic design criteria. A questionnaire was send to 62 experienced surgeons in 19 countries. The laparoscopic instruments were divided into four groups: instruments with similar functionality and handgrip model were grouped together. Eight questions were asked for every group about the type of instrument (disposable, reusable, or semireusable), the type of handle, the reason for using a specific instrument, and the experience of discomfort while using the instrument. The handles of the instruments of the group that were associated with the greatest discomfort were ergonomically evaluated on eight aspects (dimensions, angles, and control). Half of the questionnaires were returned. In every group, about 80% of the instruments the surgeons employed were reusable. The chief reason for using a specific type was the good cost-quality of the product and satisfying experiences with other products of the brand. The discomfort was pressure on thumb and fingers (scissors handle) and fixating the tip (ratchet). The handle of the instruments that causes the most discomfort met only three of the eight ergonomic requirements. Most of the laparoscopic instruments employed by surgeons in Europe are reusable. A significant number of the instruments cause discomfort. These instruments do not meet standard ergonomic requirements.

Costs and Cost Analysis↗
PubMed1999

Splenectomy revised: manually assisted splenectomy with the dexterity device--a feasibility study in 22 patients.

Laparoscopic splenectomy claims a number of advantages over open surgery: less trauma, quicker recovery, and faster return to normal activity. On the other hand, laparoscopic splenectomy is complex and time consuming, and so far, many surgeons are reluctant to perform such an operation. A new device was designed to give manual access to the abdomen through a utility laparotomy. By using one hand in the abdomen during laparoscopy, the surgeon regains direct tactile sense and hand-eye coordination. A pilot study to assess the feasibility of this method has been performed in 22 patients. The operation could be completed easily in 21 patients (95%). The average blood loss was 230 mL, and the average postoperative stay was 3.9 days. With this simple, inexpensive method, it is possible to combine the established convenience, safety, efficacy of open surgery with the advantages of minimally invasive surgery.

Adolescent↗
PubMed1998

Initial experiences with the retroperitoneal approach for endoscopic nephrectomy with the patient in the prone position.

Retroperitoneal endoscopic nephrectomy with the patient in the prone position was performed in 12 patients. Indications for this procedure were end-stage kidneys with ureteropelvic junction stenosis or distal ureteric obstruction, nonfunctional kidneys with drug resistant renin-mediated hypertension, and distal ureter malignancy. The retroperitoneal area was exposed using an open surgical technique in combination with the use of a liquid-filled dissection balloon. Removal of kidney tissue was performed with a morcellator through one of the ports. On average, the operating time was 210 min (range 160-480 min) to complete a one-sided nephrectomy. No major complications occurred. Mean hospital stay in this series was 6.6 days, and the follow-up period was uncomplicated in all cases. Retroperitoneal endoscopic nephrectomy with the patient in the prone position is an acceptable alternative to open nephrectomy in selected indications.

Adult↗
PubMed1997

Laparoscopic cholecystectomy using abdominal wall retraction. Hemodynamics and gas exchange, a comparison with conventional pneumoperitoneum.

BACKGROUND: Disadvantages related to CO2 pneumoperitoneum have led to development of the abdominal wall retractor (AWR), a device designed to facilitate laparoscopic surgery without conventional pneumoperitoneum (15 mmHg CO2). We investigated the effects of the AWR on hemodynamics and gas exchange in humans. We also investigated whether the use of an AWR imposed extra technical difficulties for the surgeon. A pilot study revealed that cholecystectomy without low-pressure pneumoperitoneum was technically impossible. METHODS: A prospective randomized controlled trial: Twenty patients undergoing laparoscopic cholecystectomy were randomly allocated into group 1: AWR with low-pressure pneumoperitoneum (5 mmHg), or group 2: conventional pneumoperitoneum (15 mmHg). RESULTS: Surgery using the AWR lasted longer, 72 +/- 16 min (mean +/- SD) vs 50 +/- 18 min compared with standard laparoscopic cholecystectomy. There were no differences between the groups with respect to hemodynamic parameters, although a small reduction of the cardiac output was observed using conventional pneumoperitoneum (from 3.9 +/- 0.7 to 3. 2 +/- 1.1 l/min) and an increase during AWR (from 4.2 +/- 0.9 to 5.2 +/- 1.5 l/min). Peak inspiratory pressures were significantly higher during conventional pneumoperitoneum compared to AWR. A slight decrease in pH accompanied by an increase in CO2 developed during pneumoperitoneum and during the use of the AWR. In both groups arterial PO2 decreased. CONCLUSIONS: The results indicate that the view was impaired during use of the AWR and therefore its use was difficult and time-consuming. Possible advantages of this devices' effects on hemodynamics and ventilatory parameters could not be confirmed in this study.

Abdominal Muscles↗
PubMed1997

Hemodynamics during laparoscopic extra- and intraperitoneal insufflation. An experimental study.

BACKGROUND: Total extraperitoneal laparoscopic surgery is an alternative to the laparoscopic transperitoneal route; however, its effects on hemodynamics have not been adequately studied. This experimental study compared the effects of intraperitoneal insufflation and extraperitoneal insufflation on hemodynamics and oxygen transport. METHODS: Sixteen pigs were randomly assigned for intraperitoneal insufflation or extraperitoneal insufflation with 15 mmHg carbon dioxide. Hemodynamic and oxygen transport parameters were taken during an hour of insufflation and analyzed for statistical differences. RESULTS: During extraperitoneal CO2 pneumoperitoneum central venous filling pressures (central venous pressure, pulmonary capillary wedge pressure and mean pulmonary arterial pressure) and end-tidal CO2 increased slower but to a similar magnitude in comparison to intraperitoneal insufflation. Cardiac output and indices of oxygen consumption and oxygen delivery were equally affected by both types of insufflation. Arterial CO2 pressure increased significantly more during intraperitoneal insufflation. CONCLUSION: The data from this study suggest that extraperitoneal insufflation might result in less cardiovascular impairment than intraperitoneal insufflation.

Analysis of Variance↗
PubMed1996

Laparoscopic-assisted colectomy with the dexterity pneumo sleeve.

UNLABELLED: The dexterity pneumo sleeve is designed to provide abdominal access for the surgeon's hand while preserving pneumoperitoneum during laparoscopy. The first experience using the dexterity pneumo sleeve in colorectal surgery is reported. METHODS: Four patients with diverticulitis and one with a dolichocolon had manually assisted laparoscopic sigmoid colectomy with the dexterity pneumo sleeve. RESULTS: Assistance of the left hand, introduced through the dexterity device proved to be extremely helpful in identifying the plane of dissection in one patient with a large diverticular mass and in another with a colovaginal fistula. Mean operative time was 109 minutes, blood loss was 80 ml, and length of incision was 7.5 cm. Flatus reoccurred at the second postoperative day, bowel movement occurred on the third day after surgery, and patients were discharged after 4.8 days. CONCLUSIONS: With the dexterity pneumo sleeve, the tactile sensation is regained, which makes laparoscopic-assisted colectomy safer and faster.

Blood Loss, Surgical↗
PubMed1995

Hemodynamics during laparoscopy in the supine or prone position. An experimental study.

During laparoscopy elevations in arterial pressure and a decrease in cardiac output have been reported. Laparoscopic surgery performed in the prone position may be advantageous for some surgical procedures, but the hemodynamic effects of pneumoperitoneum in this position have not been studied. We studied the effects of different levels of increased intraabdominal pressure on hemodynamics and oxygen transport in eight pigs in the prone and the supine position. Increases in intraabdominal pressure did not result in decreased cardiac output or in a reduction of oxygen transport and consumption in either position. These results suggest that laparoscopy in the prone position does not result in more severe hemodynamic depression than laparoscopy in the supine position.

Analysis of Variance↗
PubMed1995

Extraperitoneal laparoscopic paraaortic lymph node sampling in prone position: development of a technique.

Paraaortic lymph node sampling has been found to be efficient in the staging of genitourinary cancers. However, the complications associated with this procedure using the traditional transperitoneal or extraperitoneal approach are considerable. Developments in endoscopic technology and instrumentation have allowed an extraperitoneal approach. Presented is a porcine model for extraperitoneal endoscopic paraaortic lymph node dissection as a staging procedure for genitourinary cancers. The pig is placed in a prone position, and an extraperitoneal pneumoperitoneum is created. Using a three-port technique, we were able to remove almost 95% of all paraaortic lymph nodes laparoscopically without any complications. The prone position allows for a fast and safe procedure because it minimizes the need for extra entry ports and gives a clear view, unobstructed by the bowel, of the back wall of the abdomen.

Animals↗
PubMed1995

Retroperitoneal endoscopic lumbar sympathectomy: laboratory and clinical experience.

Retroperitoneal endoscopic lumbar sympathectomy was performed in four pigs in the prone or lateral position to study the feasibility of these new approaches. Positioning, port placement and the dissection technique are described in detail. In nine patients retroperitoneal endoscopic lumbar sympathectomy, using the lateral position technique, was performed. The importance of port placement and dissection techniques for visualisation of the sympathetic chain are emphasised. The endoscopic retroperitoneal approach enables the sympathetic chain to be accurately localised whilst enhanced endoscopic vision aids dissection. Retroperitoneal endoscopic lumbar sympathectomy is a feasible technique offering patients the benefits of the minimally invasive approach.

Animals↗
PubMed1995

Experimental retroperitoneal endoscopic surgery.

Techniques for retroperitoneal endoscopic procedures with the patient in prone position were evaluated in experimental studies in the pig. Nephrectomy, para-aortic lymph node dissection, lumbar sympathectomy and assisted aorto-femoral bypass were performed and the experience is reported herein. The prone position contributes to the creation of the retroperitoneal working space and eliminates the need for extensive retraction and thus for additional ports. The modified open Hasson technique was found to be the preferred retroperitoneal access procedure.

Animals↗
PubMed1994

The prone position. Using gravity for a clear view.

Obtaining a clear view during laparoscopic surgery in the posterior abdominal cavity, on the abdominal backwall, or during colon surgery is time consuming and therefore one of the major objections to these procedures. In an experimental setting we positioned the animals in the prone position using the abdominal flanks to introduce the trocars. Our experience with this position is that a clear and unobstructed view of the abdominal back wall and the large intestines is obtained, facilitating laparoscopic procedures in these areas.

Abdomen↗
PubMed1992

The continent ileal reservoir--an experimental study.

This thesis describes new concepts pertaining to the continent ileostomy. The aim of the study was twofold: to counter valve desinvagination and to simplify pouch construction. In Chapter 1 a survey is given of the history, the present situation of the technique and the complications of the continent ileostomy. It appears that on the one hand the operation improves the quality of the patient's life, but on the other hand the operation gives rise to many complications. The number of complications quoted in the literature varies and has been reported to be as high as 43%. Most of the time this led to repeat surgery, with equally uncertain results. This is the reason why the operation is not very frequently performed. Most of the time the complications concern the valve system and to a lesser degree the reservoir. In order to obtain a better insight into the origin of and possible gain better control over these complications an investigation was carried out on laboratory animals. This investigation involved: the complications of the valve system, the effect of the suturing method on the function of the reservoir and the simplification of the construction of the reservoir. In Chapter 2 the aim of the investigation was formulated in three questions. 1. Is it possible to diminish the chance of complications of the valve system of the continent ileostomy? 2. Does the method of suturing influence the function of the reservoir? 3. Is it possible to simplify the construction of the reservoir, so that the duration of the operation can be shortened? Chapter 3 is the general materials and methods section. Chapter 4 is about the research on the valve system. Up to now, no method of suturing the valve has consistently produced results good enough to make subsequent re-operations unnecessary. In this study two types of valve experiments have been carried out. First the feasibility of circumventing the problems of the nonpermanent form of the valve was investigated combining a short papilla with a 10 centimeter long, anti-peristaltic sutured section of the ileum. The assumption was that permanence of the form would be more easily obtained in a shorter valve (2 centimeter instead of 5 centimeter). After an initial period of continence, incontinence occurred on the average after 10 months. Autopsy showed that the short papilla had disinvaginated.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Construction of a stable nipple valve with processed dermal sheep collagen for continent ileostomy and urostomy.

Complications of the nipple valve system used for continent urostomy and ileostomy basically consist of incomplete (or complete lack of) adhesion of the invaginated serosal surfaces of the valve. A novel concept in fixation of the valve by means of the intussusception of a newly developed biomaterial (processed dermal sheep collagen; PDSC) was tested. The implanted PDSC is characterized by induction of fibroblast invasion and formation of new collagen fibers, initial high tensile strength, bio-inertion and (slow) biodegradation. It was implanted between the serosal surfaces of the invagination in 14 dogs without the application of the commonly used staples and synthetic mesh. Good permanent fixation was obtained in all cases after the PDSC had been sutured in place. As the observation time advanced up to 2 years, an increased amount of newly formed collagen was seen anchoring the serosal surfaces firmly together via the implanted PDSC with apparent slow degradation. In none of the test animals did complications occur. The first clinical trial was successful.

Animals↗
PubMedDate not supplied

Experimental videothoracoscopic cannulation of the left atrial appendix. A feasible rapid approach for initiating left heart bypass?

Rapid implementation of left ventricular assistance without thoracotomy for temporary support of patients with severe, life-threatening, acute cardiac power failure potentially expands applications of such support devices. A thoracoscopic technique for direct cannulation of the left atrium is described. In healthy closed-chest pigs, it proved a feasible method for effective volume unloading of the left ventricle.

Animals↗