Experimental foundation for in vivo measurement of the elasticity of the aorta in computed tomography angiography

OBJECTIVE

This study was performed to determine the feasibility of measuring the elastic properties of the arterial wall in vivo. To prove this concept, elastic parameters were calculated from an aortic model of elastic behavior similar to a human aorta using computed tomography angiography (CTA) images.

METHODS

We first constructed an aortic model from polydimethylsiloxane (PDMS). This model was inserted into a pulsatile flow loop. The model was then placed inside a computed tomography scanner. To estimate the elasticity values, we measured the cross-sectional area and the pressure changes in the model during each phase of the simulated cardiac cycle. A discrete wavelet transform (DWT) algorithm was applied to the CTA data to calculate the geometric changes in the pulsatile model over a simulated cardiac cycle for various pulsatile rates and elasticity values of the PDMS material. The elastic modulus of the aortic model wall was derived from these geometric changes. The elastic moduli derived from the CTA data were compared with those obtained by testing strips of the same PDMS material in a tensile testing machine. Our two aortic models had elastic values at both extremes of those found in normal human aortas.

RESULTS

The results show a good comparison between the elastic values derived from the CTA data and those obtained in a tensile testing machine. In addition, the elasticity values were found to be independent of the pulsatile rate for mixing ratios of 6:1 and 9:1 (p = .12 and p = .22, respectively).

CONCLUSIONS

The elastic modulus of a pulsatile aortic model may be measured by electrocardiographically-gated multi-detector CTA protocol. This preliminary study suggests the possibility of determining non-invasively the elastic properties of a living, functioning aorta using CTA data.

How should we measure and report elasticity in aortic tissue?

BACKGROUND

Different stress-strain definitions are used in the literature to measure the elastic modulus in aortic tissue. There is no agreement as to which stress-strain definition should be implemented. The purpose of this study is to show how different results are given by the various definitions of stress-strain used and to recommend a specific definition when testing aortic tissues.

METHODS

Circumferential specimens from three patients with ascending thoracic aortic aneurysm (ATAA) were obtained from the greater curvature and their tensile properties were tested uniaxially. Three stress definitions (second Piola-Kirchhoff stress, engineering stress and true stress) and four strain definitions (Almansi-Hamel strain, Green-St. Venant strain, engineering strain and true strain) were used to determine the elastic modulus.

RESULTS

We found that the Almansi-Hamel strain definition exhibited the highest non-linear stress-strain relation and consequently may overestimate the elastic modulus when using different stress definitions (second Piola-Kirchhoff stress, engineering stress and true stress). The Green-St. Venant strain definition yielded the lowest non-linear stress-strain relation using different definitions of stress, which may underestimate the values of elastic modulus. Engineering stress and strain definitions are only valid for small strains and displacements, which make them impractical when analysing soft tissues. We show that the effect of varying the stress definition on the elastic modulus measurements is significant for maximum elastic modulus but not when calculating the hypertensive elastic modulus.

CONCLUSIONS

It is important to consider which stress-strain definition is employed when analysing soft tissues. Although the true stress-true strain definition exhibits a non-linear relation, we favour it in tissue mechanics because it gives more accurate measurements of the material's response using the instantaneous values.

In vitro characterisation of physiological and maximum elastic modulus of ascending thoracic aortic aneurysms using uniaxial tensile testing

OBJECTIVE

Ascending thoracic aortic aneurysms (ATAA) are a life-threatening condition due to the risk of rupture or dissection. This risk is increased in the presence of a bicuspid aortic valve (BAV). The purpose of this study was to provide data on the elastic modulus of aortic wall of ATAA using uniaxial tensile testing in two different areas of the stress-strain relationship: physiological and maximum range of stresses. The influence of tissue location, tissue orientation and valve type on these parameters was investigated.

MATERIALS AND METHODS

Tissues freshly excised from ATAA with bicuspid or tricuspid aortic valve were obtained from greater and lesser curvature (GC and LC) and the specimens were tested uniaxially in circumferential (CIRC) and longitudinal (LONG) orientation. Maximum elastic modulus (MEM) was given by the maximum slope of the stress-strain curve before failure. Physiological modulus (PM) was derived from the Laplace law and from ranges of pressure of 80-120 mmHg. Means of each group of specimen were compared using Student's t-test to assess the influence of location, orientation and valve type on each mechanical parameter.

RESULTS

PM was found to be significantly lower than the MEM (p < 0.001). The MEM and PM were significantly higher (p < 0.01) in the CIRC (n = 66) than in the LONG orientation (n = 42). The MEM was higher in the circumferential orientation in the BAV group (p < 0.001 in GC and p < 0.05 in LC). MEM and PM in GC specimens were higher in the longitudinal orientation than the LC specimens (p < 0.05).

CONCLUSION

This study demonstrates the anisotropy of the aortic wall in ATAA and provides data on the mechanical behaviour in the physiological range of pressure.

The relationship between hand size and difficulty using surgical instruments: a survey of 726 laparoscopic surgeons

BACKGROUND

Hand size is an important variable to consider when designing hand tools. Laparoscopic surgical instruments have been reported to cause hand and upper extremity discomfort. This study investigates the correlation between surgical glove size, preexisting musculoskeletal problems, and difficulty using laparoscopic instruments.

METHODS

Approximately 11,000 questionnaires were sent to SAGES, AAGL, and AWS members. Questions included basic demographic and practice data, surgical glove size, the presence of musculoskeletal problems, and the perceived difficulty using several types laparoscopic instruments. There were 726 responses (from 159 women and 567 men). Subjects were grouped by hand size (Small < or =6.5, Medium 7.0-7.5, Large >7.5; female group only: Small < or =6.0, Medium 6.5, Large >6.5). ANOVA was used to test for differences between groups.

RESULTS

The percentage of time subjects reported having difficulty using all laparoscopic instruments was greater for the Small glove size group compared to both the Medium and Large groups ( p < 0.001). In females, the scissors and staplers were more difficult to use for the Small and Medium glove size group compared to the Large group ( p < 0.001). Subjects who reported musculoskeletal problems ( n = 145) performed a significantly greater percent of laparoscopic cases and found the stapler and graspers difficult to use for a greater percentage of time than those not reporting problems ( n = 559).

CONCLUSION

Hand size is a significant determinant of difficulty using laparoscopic surgical instruments. Individuals using glove sizes 6.5 or smaller experience significantly more difficulty using common laparoscopic instruments, and in particular laparoscopic staplers. Manufacturers of surgical hand tools should consider hand size when designing future surgical instruments.

An ergonomic evaluation of surgeons' axial skeletal and upper extremity movements during laparoscopic and open surgery

BACKGROUND

Many surgeons have complained of fatigue and musculoskeletal pain after laparoscopic surgery. We evaluated differences in surgeons' axial skeletal and upper extremity movements during laparoscopic and open operations.

METHODS

Five surgeons were videotaped performing 16 operations (8 laparoscopic and 8 open) to record their neck, trunk, shoulder, elbow, and wrist movements during the first hour of surgery. We also compared postprocedural complaints of pain, stiffness, or numbness between the two groups.

RESULTS

Compared with surgeons performing open surgery, surgeons performing laparoscopic surgery exhibited less lateral neck flexion; less trunk flexion; more internal rotation of the shoulders; more elbow flexion; more wrist supination and wrist ulnar and radial deviation. There was a trend of more shoulder stiffness after laparoscopic operations than after open operations.

CONCLUSIONS

Laparoscopic surgery involves a more static posture of the neck and trunk, but more frequent awkward movements of the upper extremities than open surgery. Ergonomic changes in the operating room environment and instrument design could ease the physical stress imposed on surgeons during laparoscopic operations.

Intra-aneurysmal pressure after incomplete endovascular exclusion

PURPOSE

An endoleak results from the incomplete endovascular exclusion of an aneurysm. We developed an experimental model to analyze hemodynamic changes within the aneurysm sac in the presence of an endoleak, with and without a simulated open collateral branch.

METHODS

With a latex aneurysm model connected to a pulsatile pump, pressures were measured simultaneously within the system (systemic pressure) and the aneurysm sac (intrasac pressure). The experiments were performed without endoleak (control group) and after creating a 3.5-mm (group 1), 4.5-mm (group 2), and 6-mm (group 3) diameter orifice in the endograft, simulating an endoleak. Pressures were also registered with and without a patent aneurysm side branch.

RESULTS

In each endoleak group, the intrasac diastolic pressure (DP) and mean pressure (MP) were significantly higher than the systemic DP and MP (P =.01, P =.006, and P =.001, respectively), although the pressure curve was damped. The presence of an open side branch significantly reduced the intrasac DP and MP.

CONCLUSION

In this model, intrasac pressures were significantly higher than systemic pressures in the presence of all endoleaks, even the smallest ones. Intrasac pressures higher than systemic pressure may pose a high risk for aneurysm rupture. Although patent side branches significantly reduce these pressures, the aggressive management of an endoleak should be pursued.

Performing laparoscopic surgery is significantly more stressful for the surgeon than open surgery

BACKGROUND

The awkward visual and physical interface of video-endoscopic surgery (VES) has been shown to increase the physical workload of the surgeon, yet there is a lack of objective information on the mental effort and stress demanded by VES techniques. This study addresses the hypothesis that VES is more stressful than open surgery using an ergonomic analysis of surgical tasks in a laboratory setting.

METHODS

A portable ergonomic work station was developed using a software Virtual Instrument (VI) interfaced with electronic hardware to compare the mental workload of 28 surgeons. The task was knot tying. The independent variable was work condition: rest, open technique, or VES technique. Dependent variables were tonic skin conductance level (SCL), electrooculogram (EOG), and subjective reports of concentration (CON) and stress (STR). Statistical analysis used nonparametric methods.

RESULTS

Subjects tied fewer knots using the VES technique (p < 0.05). The SCL increased progressively from rest to the open task to the VES task (p < 0.05), correlating with the subjects' reported increase in mental stress level (p < 0.05). Eye blinks decreased from rest to the open task (p < 0.05), consistent with the subjects' reported increase in level of mental concentration. From the open to the VES task, eye blinks increased (p < 0.05), as would be expected given the greater demands of the VES task. Experienced subjects demonstrated less variability in SCL levels across tasks.

CONCLUSIONS

VES technique requires greater concentration and places greater mental stress on surgeons than to open surgery. More experience with VES may decrease this effect. Studies are needed to improve the human-technology interface the stress.

The effect of laparoscopic instrument working angle on surgeons' upper extremity workload

BACKGROUND

Laparoscopic surgery may be kinder to the patient, but it is more demanding on the surgeon. Fixed trocar positions often require the surgeon to work with instruments at awkward angles to their body. We studied the effect of horizontal and vertical laparoscopic instrument working angle on the surgeon's thumb, forearm, and shoulder muscle work.

METHODS

Electronyographic (EMG) signals were collected from the thenar compartment (TH), flexor digitorum superficialis (FDS), and deltoid (DEL) muscles of the dominant arm of eighth surgeons while they were closing a standard pistol-grip disposable laparoscopic grasper against a fixed resistance of 3 N. With the aid of a special testing bench, the instruments' position was randomly changed among 15 degrees, 45 degrees, and 75 degrees of horizontal angulation relative to the surgeons' sagital plane, and 15 degrees, 45 degrees, and 75 degrees degrees of vertical angulation relative to a horizontal plane. EMG signals were rectified and smoothed using analogue circuitry and digitally sampled at l0 Hz using a National Instruments DAQCard-700 connected to a Macintosh PowerBook 5300c running LabVIEW software. Statistical analysis was carried out by analysis of variance (ANOVA).

RESULTS

The effects of vertical and horizontal working angles on the muscle effort were as follows: TH (horizontal, N.S.; vertical, N.S.), FDS (horizontal, p 45 degrees to the surgeon's sagital plane significantly increases the workload of the flexor digitorium superficialis and deltoid muscles. The deltoid muscle is also adversely affected by vertical angulation of the instrument. The instrument working angle has no effect on the thenar muscles. Whenever possible, laparoscopic surgeons should strive to place their instruments and trocars so as to minimize extreme horizontal or vertical displacement of their hands away from a resting position of comfort.

One stage carotid artery resection: reconstruction in radiated head and neck carcinoma

PURPOSE

Management of the carotid artery involved with metastatic squamous cell carcinoma continues to be a topic of much discussion. Early reports, for the most part, focused on the sequel of ligation and the development of various tests to predict patient tolerance for the procedure. More recent alternatives have described resection reconstruction in multistage procedures. By using immediate reconstruction with autogenous arterial grafting, carotid artery resection can be accomplished in patients with radiation failure in a single stage. This technique can be used without the addition of myocutaneous flaps, controlled fistulas, or intracranial surgery advocated for usage with alternative techniques.

PATIENTS AND METHODS

Immediate reconstruction after resection of the carotid artery with superficial femoral arterial graft is described.

RESULTS

In a series of 18 high-risk patients with radiation failure, the artery was successfully resected and reconstructed in 1 stage without any neurologic or vascular complications. The technique has been associated with prolonged survival in selected patients.

CONCLUSION

Carotid artery resection and immediate reconstruction can be performed in high-risk radiation failure patients with acceptable complications, and is associated with prolonged survival in selected cases.

A virtual instrument ergonomics workstation for measuring the mental workload of performing video-endoscopic surgery

The visual and physical interface imposed on the surgeon by video-endoscopic surgery (VES) increases the surgeon's mental workload. Ergonomic studies are needed to develop ways to reduce this workload. We used virtual instrumentation to devise a portable ergonomic workstation to compare the surgeon's mental workloads during simulated open surgery and VES. The system measures palmar tonic skin conductance level (SCL) and electrooculogram (EOG) and frontalis electrical activity to monitor mental stress and concentration levels. We used the system at a national surgery conference on volunteer subjects during a rest period and as they performed simulated surgery, consisting of typing knots using open and VES techniques. The subjects were asked to self-rate their levels of mental concentration and stress during these activities and reported that both progressively increased from rest to the open surgery task to the VES task. The subjects tied fewer knots during the VES than the open task, consistent with the increased demands of the VES task. The SCL progressively increased from rest to the open task to the VES task, correlating with the subjects' reported increase in mental stress level. Eye blinks and low frequency EOG activity decreased from rest to the open task, consistent with the subjects' reported increase in mental concentration level. From the open to the VES task, eye blinks and EOG activity increased, as expected given the greater demands of the VES task. High frequency frontalis activity merits further study as another indicator of the subjects' levels of mental concentration and stress.

Standardized technique of laparoscopic surgery in the rat

The evolution of advanced laparoscopic techniques requires animal models for instrument development, evaluation of the physiopathological correlation and physician training. Selection of surgical models is primarily based on cost, availability, anatomic and physiologic considerations, and housing and anesthetic methods. The use of large animals is becoming increasingly difficult due to restrictive legislation, public concern, and economic factors. A standardized technique of laparoscopic surgery in the rat has been developed to perform procedures in all abdominal regions including fundoplication, splenectomy, nephrectomy, liver resection, herniorraphy, colotomy, colectomy, and retroperitoneal exploration. The equipment consists of a specially designed small animal operating table, a standard arthroscope and micro-instruments. The rat model gives the opportunity to investigate the physiopathological relations and immune functions of laparoscopic procedures, to develop micro-instruments under realistic conditions of a live organism, and it is an excellent training model especially for pediatric and microsurgery. Besides low costs and easy availability, the rat model requires less logistic and financial efforts.

Measurement of intracellular gamma-interferon, interleukin-4, and interleukin-10 levels in patients following laparoscopic cholecystectomy

Major surgery suppresses intracellular T-cell cytokine production. Laparoscopic surgery has been reported to have no effect on in vitro lymphocyte reactivity, but its effects on intracellular cytokine production are unknown. This study measured T-cell intracellular gamma-interferon, interleukin-4 (IL-4), and interleukin-10 (IL-10), along with serum interleukin-6 (IL-6) and cortisol levels, immediately before and 1 day after laparoscopic cholecystectomy in a cohort of six Air Force and veteran patients. Stimulated intracellular levels of gamma-interferon were slightly, but not significantly, elevated during the postoperative period in all T-cell subsets. There were no postoperative changes in stimulated IL-4 or IL-10 levels. Postoperative serum IL-6 levels, but not serum cortisol levels, were significantly elevated compared to preoperative values. In conclusion, laparoscopic surgery causes slight trauma but has no effect on T-cell intracellular interferon, IL-4, and IL-10 responses.

Surgical reconstruction of the extracranial vertebral artery: management and outcome

PURPOSE

The purpose of this study was to identify the risk and outcome of reconstruction of the extracranial vertebral artery (ECVA).

METHOD

The study was conducted as a retrospective review of 369 consecutive ECVA reconstructions.

RESULTS

The clinical presentations consisted of hemispheric symptoms alone in 4% of the cases, hemispheric and vertebrobasilar symptoms in 30%, and vertebrobasilar symptoms alone in 60%. The cause of the lesion was atherosclerosis (n = 300), extrinsic compression (n = 42), dissection (n = 7), radiation arteritis (n = 5), intimal hyperplasia (n = 3), fibromuscular dysplasia (n = 2), previous surgical ligation (n = 3), aneurysm (n = 2), and other (n = 5). All the patients underwent preoperative arteriography. There were 252 proximal ECVA reconstructions (218 transpositions, 42 bypass grafting procedures, and two other) and 117 distal ECVA reconstructions (85 bypass grafting procedures, 25 transpositions, and seven other). In 83 patients, the ECVA operation was performed concomitant with a carotid or supraaortic trunk reconstruction. This series was analyzed in two separate sets: before 1991 (n = 215), when changes in indications and management were occurring; and after 1991 (n = 154), when we acquired a dedicated anesthesia team and digital arteriography in the operating room and established uniform protocols for the management of ECVA disease. The stroke, death, and stroke/death rates for the period before 1991 were, respectively, 4. 1%, 3.2% and 5.1%. The stroke, death, and stroke/death rates for the period after 1991 were, respectively, 1.9%, 0.6% and 1.9%. The patency rate at 5 years was 80%. The survival rate at 5 years was 70%. Most of the deaths during the follow-up period were caused by cardiac disease. Among the survivors, the protection rate from stroke was 97%.

CONCLUSION

The changes in operative selection and management have improved the results of ECVA reconstruction. The data reported for ECVA reconstruction in patients who underwent operation since 1991 reflect the outcome of ECVA reconstruction today. In our experience, a reconstruction of the ECVA is less risky than a carotid reconstruction.

A comparison of forearm and thumb muscle electromyographic responses to the use of laparoscopic instruments with either a finger grasp or a palm grasp

Laparoscopic techniques allow for less-invasive treatment of common surgical problems. Laparoscopic instruments are different from standard surgical instruments and generally incorporate a pistol-grip handle configuration with rings for the fingers. This handle configuration has been reported as being uncomfortable, leading to finger compression neuropathies in some cases. As an alternative, the surgeon can choose to grasp laparoscopic instruments using a more powerful palm grip during grasping motions. This study evaluates the hypothesis that the use of the palm grip requires less muscle tension than the finger-grip when grasping with laparoscopic instruments. Nine general surgeons used an Autosuture laparoscopic grasper with a ringed pistol-grip handle held in both a finger-in-ring (F) or palm (P) hand grip position to grasp and close two spring-loaded metal plates. The same task was performed with a surgical haemostat clamp (H) for comparison. Each subject performed the grasping task in a random sequence for the three instrument configurations at two grasping forces levels (0.7 and 4.2 N), and with the instrument at three angles to the subjects' sagittal plane (0 degree, 45 degrees and 90 degrees). Surface electromyographic (EMG) signals were acquired from the flexor carpi ulnaris (FCU), flexor digitorum profundus (FDP), flexor digitorum superficialis (FDS), extensor carpi ulnaris (ECU), extensor digitorum comunis (EDC) and the thenar compartment (TH). The peak root mean squared (RMS) EMG voltage was averaged for five repetitions at each instrument, force and angle condition. Statistical analysis was carried out by repeated measures ANOVA. The muscle EMG RMS amplitude while using the palm grip was decreased in the FDS, TH and EDC, was unchanged in the ECU and FCU, and was slightly higher in the FDP when compared with the finger grip. These differences were most prominent at 90 degrees to the sagittal plane where the subjects' wrists neared maximal flexion. It is concluded that the palm grip is more powerful than the finger grip when grasping with laparoscopic instruments, particularly at angles perpendicular to the surgeon's sagittal plane.

A virtual instrument ergonomics workstation to measure surgeons' physical stress

Videoendoscopic (VES) instruments have poor force transmission properties and often require surgeons to employ awkward hand and arm positions. In order to compare the physical workload of laparoscopic surgery to open surgery, we collected long-duration EMG records from the thumb (thenar compartment) of six surgeons performing suturing and knot tying in a training box using both open and VES techniques. EMG signals were acquired using a LabVIEW Virtual Instrument and analyzed using a Modified Exposure Variation Analysis (MEVA) algorithm. Standard EMG indices and the MEVA analysis demonstrated significantly greater amplitude and duration of EMG signals using VES technique compared to open technique. Our results suggest that the use VES techniques requires a greater intensity of physical effort than open surgery techniques.

Surgery and ergonomics

This article will provide the reader with an overview of ergonomic issues relevant to the operating room environment. Minimally invasive surgical technologies have increased the therapeutic value of surgical procedures by allowing operations to be performed with less trauma to the patient. At the same time, the surgical team-and particularly the surgeon-have been further removed from direct interaction with the patient's tissues. A scientific and ergonomic approach to the analysis of the operating room environment and the performance and workload characteristics of members of the modern surgical team can provide a rational basis for maximizing the efficiency and safety of our increasingly technology-dependent surgical procedures.

Suboccipital approach to the distal vertebral artery

A technique to expose directly the pars atlantica or the vertebral artery through a posterior approach was studied. It is useful when dealing with occlusive, aneurysmal, or dissecting lesions that extend to the transverse process of C1 or beyond. This technique permits exposure of the entire pars atlantica or the vertebral artery, from its exit from the foramen transversarium of C1 to its penetration of the dura mater at the foramen magnum. The experience with this technique in three patients is described.

Major surgery suppresses maximal production of helper T-cell type 1 cytokines without potentiating the release of helper T-cell type 2 cytokines

BACKGROUND

Major surgery is known to suppress T-cell function; however, its differential effects on the production of helper T-cell type 1 (T(H)1) and type 2 (T(H)2) cytokines remains unknown.

OBJECTIVE

To measure the production patterns of T(H)1 (interleukin 2 [IL-2] and interferon gamma) and T(H)2 (IL-4 and IL-10) cytokines following major surgery.

DESIGN, SETTING, AND PATIENTS

A cohort study of patients (both active and former members of the armed forces) at a military hospital.

INTERVENTION

Aortic surgery or carotid endarterectomy and measurement of serum IL-6 levels by enzyme-linked immunosorbent assay.

MAIN OUTCOME MEASURES

Unstimulated and stimulated intracellular levels of IL-2, IL-4, IL-10, and interferon gamma in CD4+, CD8+, and gammadelta+ T cells and serum IL-6 levels immediately before and for 2 days after aortic surgery or carotid endarterectomy.

RESULTS

No unstimulated production of T(H) or T(H)2 cytokines was detected. Stimulated intracellular levels of IL-2 and interferon gamma were significantly depressed during the postoperative period in all T-cell subsets in both patient groups. There were no postoperative increases in stimulated IL-4 or IL-10 levels.

CONCLUSION

Major surgery suppresses the potential responses of T(H)1 cytokines without enhancing production of T(H)2 cytokines.

Ergonomic problems associated with laparoscopic surgery

BACKGROUND

The Society of American Gastrointestinal Endoscopic Surgeons (SAGES) Task Force on Ergonomics conducted a subjective and objective assessment of ergonomic problems associated with laparoscopic instrument use. The goal was to assess the prevalence, causes, and consequences of operational difficulties associated with the use of laparoscopic instruments.

METHODS

A questionnaire was distributed asking respondents to rate the frequency with which they experienced pain, stiffness, or numbness in several body areas after laparoscopic operations. An ergonomics station was assembled to quantify forearm and thumb muscle workload. Processed electromyogram (EMG) signals were acquired from 27 volunteer surgeon subjects while they completed simulated surgical tasks using a hemostat and an Ethicon laparoscopic grasper, with the aid of an endoscopic trainer and video monitoring system.

RESULTS

Of 149 surgeons responding to the questionnaire, 8% to 12% reported frequent pain in the neck and upper extremities associated with laparoscopic surgery. The ergonomics station demonstrated that the peak and total muscle effort of forearm and thumb muscles were significantly greater (p < 0.01) when the grasping task was performed using the laparoscopic instrument rather than the hemostat.

CONCLUSION

These findings indicate that laparoscopic surgical technique is more taxing on the surgeon.

Cervical reconstruction of the supra-aortic trunks: a 16-year experience

PURPOSE

The purpose of this study was to review 182 consecutive cervical reconstructions of supra-aortic trunks, which were performed over a 16-year period.

METHODS

A total of 182 innominate, common carotid, or subclavian arteries were reconstructed with a cervical approach in 173 patients aged 23 days to 83 years. Indications included hemispheric (n = 79), vertebrobasilar (n = 56), upper extremity (24), and internal mammary/cardiac ischemia (n = 5), asymptomatic severe common carotid disease (n = 33), or other (n = 3). Primary atherosclerotic innominate (n = 6), common carotid (n = 84), and subclavian (n = 66) lesions underwent reconstruction. Thirty-one operations were performed for multiple trunk involvement, recurrent disease, arteritis, infection, dissection, coarctation, or aneurysm. There were 122 bypass grafting procedures (98 ipsilateral, 24 contralateral) and 60 arterial transpositions.

RESULTS

One death (0.5%) and 7 nonfatal strokes (3.8%) occurred, none in patients who were asymptomatic. Perioperative morbidity included four asymptomatic occlusions (2%), 6 myocardial infarctions (3%), 10 pulmonary complications (5%), and 2 graft infections (1%). Follow-up periods ranged from 1 to 190 months (mean, 53 +/- 5 months). Nineteen patients (10%) were lost to follow-up. Fifty-seven late deaths occurred, most from cardiac causes. Seven reconstructions necessitated late revision. The cumulative primary patency rate at 5 and 10 years was 91% +/- 2% and 82% +/- 5%, respectively. The survival rate at 5 years was 72% +/- 4% and at 10 years was 41% +/- 6%. The stroke-free survival rate was 92% +/- 2% at 5 years and 84% +/- 2% at 10 years.

CONCLUSION

Cervical reconstruction of symptomatic and asymptomatic supra-aortic trunk lesions carries acceptable death and stroke rates and provides a long-term patient benefit. This should be the preferred approach for asymptomatic lesions and for patients with significant comorbidity because it carries less morbidity than direct transmediastinal aortic-based reconstruction.

Virtual ergonomic studies in endoscopic intervention

Virtual instrumentation provides a strong platform for the rapid design and prototyping of biomedical instruments. Virtual instrument software written using a block diagram approach familiar to instrument designers quickly turns a personal computer into a custom biomedical instrument. The portable VIs we have developed for ergonomic analysis of video-endoscopic surgery are quick to set up and convenient to use. We have collected a large amount of ergonomic data in a short time with these VIs because of their custom design and because we can take them to sites where there are many willing surgeon-subjects. We are preparing to use these VIs in studies of actual surgery.

An ergonomic comparison of in-line vs pistol-grip handle configuration in a laparoscopic grasper

BACKGROUND

Laparoscopic instruments incorporate both in-line and pistol-grip handle configurations, yet it is unclear which design is most advantageous for surgeons, particularly when operating at angles perpendicular to the surgeon's position. We present a detailed electromyographic (EMG) comparison of these handle configurations under different force and angle conditions.

METHODS

Nine general surgeons used a Microsurge grasper with the handle in an in-line (MS-IL) and pistol (MS-PS) configuration, as well as a standard hemostat (HE), to grasp and close two spring-loaded metal plates. The task was performed randomly by each subject with the three instrument configurations at two forces levels (0.7 N, 4.2 N) and at three angles to the surgeons' body (0, 45, and 90 degrees). Surface EMG was measured from the flexor carpi ulnaris (FCU), flexor digitorum profundus (FDP), flexor digitorum superficialis (FDS), extensor carpi ulnaris (ECU), extensor digitorum comunis (EDC), and thenar compartment (TH). The peak root mean squared (RMS) EMG voltage was calculated for each instrument, force, and angle condition. Statistical comparison was carried out by ANOVA.

RESULTS

Both laparoscopic handle configurations required significantly higher contractions of all muscle groups compared to the hemostat at the high force level. TH was not affected by laparoscopic handle configuration. MS-IL required higher FCU, ECU, and EDC contractions at 45 degrees compared to MS-PS. However, MS-IL decreased the flexor compartment muscle contractions (FDP, FDS, FCU) at 90 degrees compared to MS-PS.

CONCLUSIONS

Laparoscopic grasping requires higher forearm and thumb muscle contractions compared to the use of a hemostat. The in-line handle configuration is no better than the pistol configuration except when grasping at 90 degrees to the surgeon, where rotation of the handle and wrist back toward the surgeon significantly decreases forearm flexor compartment muscle contractions.

Surgical technology and the ergonomics of laparoscopic instruments

Laparoscopic surgery provides patients with less painful surgery and a more rapid recovery, while requiring that surgeons work harder and in a more remote manner from the operating field. Cost-containment pressures on surgeons demand efficient surgery, whereas the increased technological complexity and sometimes poorly adapted equipment have led to increased complaints of surgeon fatigue and discomfort during laparoscopic surgery. There is, therefore, a need to evaluate the ergonomic integration and suitability of the laparoscopic operating room environment to address the issues of efficiency, safety, and comfort for the operating team. This approach is particularly important in the design of laparoscopic surgical instruments. A review of the literature on the biomechanics of laparoscopic surgical instrument use was combined with data from the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) Ergonomics Questionnaire and demonstration station. Laparoscopic instruments suffer from ergonomically inadequate handle designs and inefficient handle to tip force transmission, which lead to surgeon fatigue, discomfort, and hand paresthesias. Improvements in the design of laparoscopic instruments are needed to decrease the work and discomfort of tissue manipulation during video-endoscopic surgery.

Carotid resection and replacement with autogenous arterial graft during operation for neck malignancy

Carotid artery resection as part of the management of advanced head and neck cancers remains controversial. Since 1991, 30 patients have undergone resection of the carotid artery with immediate reconstruction using superficial femoral artery as replacement conduit. There was one stroke/death. Forty-three percent developed neck wound problems but no grafts failed or hemorrhaged. Mean follow-up was 20 months (3-76) and mean life expectancy was 16 months from the time of surgery. Fifty-eight percent were free of local recurrence at the time of death. There was a 35% disease-free survival rate at 2 years. These results compare favorably with alternative therapy including carotid ligation or shaving tumor from the carotid artery. Given the importance of cerebral perfusion and local tumor control we offer superficial femoral artery as a durable conduit for immediate extracranial carotid reconstruction in the often hostile environment associated with cancer resection in the neck.

A review of 100 consecutive reconstructions of the distal vertebral artery for embolic and hemodynamic disease

PURPOSE

The aim of our study was to assess the outcome of distal vertebral artery (VA) reconstructions through a retrospective review conducted at a university-affiliated referral center.

METHODS

One hundred consecutive distal VA reconstructions had been performed during a period of 14 years (98 patients) and included reversed saphenous vein bypass from the ipsilateral common, internal, or external carotid to the third portion of the VA at the C1-2 level (68 reconstructions) or the C0-1 level (4); transposition of the external carotid or its occipital branch to the VA (23); and transposition of the third portion of the VA onto the internal carotid artery (2). Other methods were used in 3 additional patients. Eighteen patients underwent concomitant carotid operations, and 1 patient underwent a concomitant subclavian transposition. Symptoms were present in 98% of patients and included vertebrobasilar ischemia (89%), vertebrobasilar plus hemispheric ischemia (7%), and hemispheric ischemia (2%). Two asymptomatic patients with bilateral carotid occlusions underwent operations to provide a single artery for cerebral perfusion (2%). Sixty-three lesions were atherosclerotic, 18 were dynamic bony compressions, and 14 were dissection, fibromuscular dysplasia, arteritis, or aneurysm. Five had miscellaneous anatomic indications.

RESULTS

Stroke caused the four perioperative deaths that occurred. There was one occurrence of nonfatal hemispheric stroke. Routine postoperative arteriography identified 16 graft abnormalities; 11 patients underwent attempted revision. The introduction of the use of intraoperative angiography in 1990, halfway through the series, lowered the incidence of graft abnormalities from 28% to 4% and the incidence of perioperative death from 6% to 2%. Eighty-seven percent of patients had complete or significant resolution of symptoms. Follow-up ranged from 1 to 168 months (mean, 79 months). Ten patients were lost to follow-up. Twenty late deaths occurred; none were stroke related. Five reconstructions required late revision. The cumulative primary patency at 5 and 10 years was 75% +/- 6 and 70% +/- 7 (mean +/- SE), respectively; cumulative secondary patency was 84% +/- 5 and 80% +/- 6 at 5 and 10 years, respectively. Median survival was 107 months.

CONCLUSIONS

Distal VA reconstruction provides excellent long-term patency and stroke protection. Intraoperative angiography is mandatory.

Reflex sympathetic dystrophy of the face: current treatment recommendations

Reflex sympathetic dystrophy (RSD) of the face is an infrequently reported clinical pain syndrome characterized by dysesthesia, hyperalgia, hyperpathia, and allodynia. Treatment strategies, extrapolated from RSD and causalgia of the extremities, remain variable and poorly defined. Sympathetic blockade is generally the diagnostic and therapeutic treatment of choice; however, the frequency, timing, and duration of injections; need for neurolytic blocks; and role of sympathectomy are not well understood. The objectives of this report are to highlight the clinical behavior of facial RSD and contrast its essential differences from extremity RSD in response to standard treatment regimes. The case studies of two patients with this syndrome, following vascular surgery in the neck, are retrospectively reviewed with existent reported cases. Age, gender, etiology, symptoms, onset, triggers, and examination findings; timing, duration, and method of treatment; and outcome are summarized, forming the database for this study. Findings demonstrate an infrequent association of vasomotor and sudomotor changes with facial RSD, and lack of progression to a dystrophic or an atrophic stage, in contrast to extremity RSD. Furthermore, treatment response to sympathetic blockade is durable and less critically dependent on timing. The authors conclude that facial RSD has a favorable prognosis and should be managed conservatively with nonneurolytic stellate ganglion blocks, even when initiated as a delayed and repetitive injection series.

Adrenocortical response and regional T-lymphocyte activation patterns following minimally invasive surgery in a rat model

BACKGROUND

Laparoscopic surgery is associated with less tissue trauma and postoperative pain as well as a more rapid recovery than open surgery. We hypothesized that these factors may result in less immune impairment following laparoscopic surgery.

METHODS

We measured mitogen-induced surface interleukin-2 receptor (IL2R) expression and lymphocyte proliferation in CD4+ and CD8+ T-lymphocytes as well as serum corticosterone levels in rats 24 h following open (OP) and laparoscopic (LAP) fundoplication.

RESULTS

Serum corticosterone levels were lower in LAP vs OP rats (p = 0.02). CD4+ IL2R expression was higher in the blood, but not in the spleen, in LAP vs OP animals (p = 0.02). CD8+ IL2R expression was similar in both groups. Mitogen-induced lymphocyte proliferation was no different in the blood but decreased in the spleen in LAP vs OP rats (p = 0.03).

CONCLUSIONS

Compared to open surgery, laparoscopic fundoplication in the rat results in lower adrenocortical hormone levels and better-preserved T-helper-cell activation in the blood. Lymphocyte proliferation is suppressed in the spleen 24 h after laparoscopic surgery. Minimally invasive surgery may better preserve cell-mediated immunity in the early postoperative period.

Transthoracic repair of innominate and common carotid artery disease: immediate and long-term outcome for 100 consecutive surgical reconstructions

PURPOSE

This is a review of 100 consecutive supraaortic trunk reconstructions (SAT) performed over 16 years.

METHODS

There were eight innominate endarterectomies and 92 bypass procedures based on the thoracic aorta (n = 86) or proximal innominate artery (n = 6) in 98 patients 24 to 79 years of age. Indications included cerebrovascular ischemia in 83 and upper extremity ischemia in four. Thirteen patients were asymptomatic. An innominate lesion was bypassed in 78 cases. The left common carotid and left subclavian arteries required reconstruction in 38 and nine patients, respectively. Multiple trunks were reconstructed by direct bypass grafting in 35. Approach was via median sternotomy in 92, partial sternotomy in six, and left thoracotomy in two. Seven patients underwent concomitant cardiac surgery.

RESULTS

Eight deaths and eight nonfatal strokes occurred, for a combined stroke/death rate of 16%. The operative mortality rate was 6% for SAT and 29% for SAT/cardiac operations. Perioperative complications included two asymptomatic graft occlusions, three nonfatal myocardial infarctions, seven significant pulmonary complications, three sternal wound infections, and one recurrent laryngeal nerve injury. Follow-up ranged from 1 to 184 months (mean, 51 +/- 4.8 months). Eight patients were lost to follow-up. Twenty-one late deaths occurred. Two SATs required late revision. The cumulative primary patency rates at 5 and 10 years were 94% +/- 3% and 88% +/- 6%, respectively. The stroke-free survival rates at 5 and 10 years were 87% +/- 4% and 81% +/- 7%, respectively. Patients who survived beyond 30 days had a median stroke-free life expectancy of 10 years, 7 months (SE, 6%).

CONCLUSIONS

Direct reconstruction of complex symptomatic SAT lesions can be performed with acceptable death/stroke rates and with long-term patient benefit. Asymptomatic lesions in patients who have significant concomitant conditions should be managed with a less-morbid cervical or endovascular approach, even if long-term outcome of the latter is inferior.

The Virtual Instrumentation (VI) Laboratory facilitates customized on-site ergonomic analysis of minimally invasive surgery

Ergonomic studies are needed to understand and improve the visual and physical interface that minimally invasive surgery methods interpose between the surgeon and the operating field. We used the Virtual Instrumentation (VI) Laboratory of the Biomedical Engineering Program at California State University, Sacramento to develop a portable ergonomic analysis system to compare the physical workloads imposed on the surgeon by tradition open and laparoscopic surgery techniques. We used the system at a national surgery conference to measure electromyogram (EMG) activity from thumb and forearm muscles of volunteer subjects as they performed simulated surgical tasks using open and laparoscopic techniques. We found that EMG activity was significantly greater for the laparoscopic than for the open surgery technique, suggesting that the laparoscopic technique was more physically demanding. The portable ergonomic analysis VI system was quick to set up and convenient to use. We are using the rapid prototyping and modular design capabilities of the VI Lab to develop additional ergonomic analysis VI systems.

Laparoscopic cecal ligation and puncture in the rat. Surgical technique and preliminary results

BACKGROUND

We describe a technique of laparoscopic cecal ligation and puncture (CLP) in the rat analogous to open CLP which may facilitate the study of minimally invasive surgery (MIS) and peritonitis.

METHODS

Forty-four rats were randomized to either laparoscopic or open CLP and their 3-day mortality was recorded. Autopsies were performed for peritoneal fluid cultures, measurement of the length of ligated cecum, and scoring of the degree of cecal necrosis.

RESULTS

Laparoscopic CLP required slightly longer operating times compared to open CLP (average 15.6 vs 13.1 min, p = 0.002). Three-day postoperative mortality was 36.4% and 22.7% for open and laparoscopic CLP, respectively (p = NS). There were no differences in the length of ligated cecum or the cecal necrosis score between the open and laparoscopic CLP groups.

CONCLUSION

Laparoscopic CLP is feasible and produces a fecal peritonitis with similar characteristics to those of traditional open CLP.

The optimum pneumoperitoneum pressure for laparoscopic surgery in the rat model. A detailed cardiorespiratory study

BACKGROUND

There is increasing interest in the rat model of laparoscopic surgery. This study evaluates the cardiorespiratory effects of increasing CO2 pneumoperitoneum (PP) in the rat.

METHODS

Nine Sprague-Dawley rats were subjected to CO2 PP at pressures of 2, 5, 10, and 15 mmHg or control (no PP) under anesthesia. Catheters were placed in the femoral artery and the jugular vein to measure heart rate (HR), blood pressure (MAP), and arterial pH, PCO2, PO2, and HCO3. A thermistor probe in the aortic arch measured cardiac output (CO) and blood temperature (BT).

RESULTS

CO2 PP had no effect on CO, MAP, or BT at any pressure. CO2 PP greater than 5 mmHg caused significant bradycardia and CO2 PP greater than 10 mmHg caused significant respiratory acidosis.

CONCLUSIONS

CO2 PP pressures above 10 mmHg in rat should be avoided when performing laparoscopic surgery in the rat model.

The application of ergonomics in the work environment of general surgeons

Ergonomics, also called human factors engineering, is the study of the behavior and activities of individuals in relation to the working environment and the mechanical and electronic equipment operated by the worker. The function of specialists in ergonomics is to design or to improve the workplace, equipment, and procedures of workers to ensure the safe, healthy, and efficient achievement of personal and organizational goals. Many mental and physical similarities can be found between the work of a surgeon and the jobs of skilled industrial and military personnel. This review addresses the necessity for applying ergonomics in surgical working activities. The materials reviewed here are classified into the following topics in surgical ergonomics: Visualization, manipulation, posture, mental and physical workload, and the operating-room environment. It was concluded that the discipline of ergonomics can enhance our understanding of the way in which surgeons work. As surgeons confront increasingly complex and costly procedures, the need to cut health-care costs deems it necessary to develop a scientific understanding of the mechanics of surgical operations.

A comparison of surgeons' posture during laparoscopic and open surgical procedures

BACKGROUND

There is increasing recognition of surgeons' physical fatigue in the new ergonomic environment of laparoscopic surgery. The purpose of this study was to determine what the differences are in the movement of the surgeon's axial skeleton between laparoscopic and open operations.

METHODS

Surgeons' body positions were recorded on videotape during four laparoscopic (LAP) and six open (OP) operations. The percent of time the head and back were in a normal, bent, or twisted position as well as the number of changes in head and back position were tabulated using a computer program. A separate laboratory study was performed on four surgeons "walking" a 0.5-inch polyethylene tubing forward and backward using laparoscopic and open techniques. The movements of the surgeons' head, trunk, and pelvis were measured using a three-camera kinematic system (Kin). The center of pressure was recorded using a floor-mounted forceplate (Fp).

RESULTS

In the operating room surgeons' head and back positions were more often straight in laparoscopic procedures and more often bent in open operations. The number of changes in back position per minute were significantly decreased when the laparoscopic-only part of surgery was analyzed. In the laboratory the subjects' head position was significantly (p = 0.02) more upright and the anteroposterior (AP) and rotational range of motion of the head was significantly reduced during laparoscopy. Subjects' CP was more anterior and there was a significant reduction in the AP range of motion of the CP during laparoscopy.

CONCLUSIONS

Our study suggests that surgeons exhibit decreased mobility of the head and back and less anteroposterior weight shifting during laparoscopic manipulations despite a more upright posture. This more restricted posture during laparoscopic surgery may induce fatigue by limiting the natural changes in body posture that occur during open surgery.

Use of the virtual instrumentation laboratory for the assessment of human factors in surgery and anesthesia

There is a growing consensus that human factors issues for anesthesiologists, surgeons, and other operating room personnel require serious attention. We have established a program of collaboration between the University of California Davis Medical Center Departments of Anesthesiology and Surgery and the California State University Sacramento Biomedical Engineering Program to address ergonomic problems in anesthesiology and surgery using a Virtual Instrumentation Laboratory. A 17-workstation Virtual Instrument Laboratory using LabVIEW software on Power Macintosh platforms permits rapid prototyping of medical monitor displays as well as rapid development of data acquisition and processing circuits for physiologic data collection. The Virtual Instrument Lab has been used for three Master's thesis projects and a BME course titled Human Factors in the Design of Medical and Assistive Technology. Course projects have included: 1) The design of novel physiologic data displays for potential use in anesthesia workstations, and 2) The measurement of surface electromyographic signals and heart rate variability to investigate the physical and mental workload of performing laparoscopic surgery. The Virtual Instrument Lab allows BME students to investigate relatively complex human factors issues in anesthesiology and surgery in a short time span.

Successfully establishing laparoscopic surgery programs in developing countries. Clinical results and lessons learned

BACKGROUND

Laparoscopic surgery has not been widely established in developing countries due to the lack of access to training and lack of money. We describe our experience using on-site training programs to efficiently teach and propagate laparoscopic surgery in Leon, Nicaragua; La Paz, Bolivia; and Santa Cruz, Bolivia.

METHODS

A group of well-trained and motivated local surgeons was identified in each country as the initial target for teaching. Participants were taught basic and advanced laparoscopic surgery during on-site didactics, animal laboratories, and proctoring sessions. Follow-up courses were held until the target group of surgeons was capable of independently teaching and supervising laparoscopic surgery among other surgeons in each country.

RESULTS

Multiple technical and logistic difficulties were encountered. In Leon, Nicaragua, and La Paz, Bolivia, a total of eight surgeons were fully trained and proctored in laparoscopic cholecystectomy. In La Paz and Santa Cruz, Bolivia, a total of seven surgeons were instructed in advanced laparoscopic procedures. To date, over 180 patients have undergone laparoscopic cholecystectomy or advanced procedures with a morbidity similar to that reported in literature series in the United States.

CONCLUSIONS

Our experience demonstrates that in spite of numerous limitations, basic and laparoscopic surgery can be efficiently and safely taught in developing countries. Many lessons were learned in how to safely and efficiently use laparoscopic equipment and instruments within strict financial constraints.