Laparoscopic ventral and incisional hernioplasty.

BACKGROUND: While the first laparoscopic ventral hernia repair was reported in 1992, there have been no studies comparing laparoscopic to conventional ventral herniorrhaphy. METHODS: Twenty-one ventral hernias repaired laparoscopically are compared to a similar group of 16 patients undergoing traditional open repair during a 2-year period. Operative and hospital courses along with outcomes and cost analysis are analyzed. RESULTS: There was no statistical difference between groups in number of previous abdominal operations, prior hernia repairs, and comorbidities. Patients undergoing open repair were older with larger fascial defects. Open repairs had a shorter operative time as compared to the laparoscopic group, but statistically longer postoperative stays and costs. Postoperative complications occurred in 31% of the open group and 23% of the laparoscopic group. There were two recurrences in each group. CONCLUSIONS: Laparoscopic herniorrhaphy is as safe and effective as the traditional open technique with shorter length of stay and decreased hospital costs.

Measurement of vascular input impedance in infrainguinal vein grafts.

The purpose of this investigation was to measure vascular input impedance in infrainguinal vein grafts and assess the importance of clinical and hemodynamic parameters in predicting graft patency. Fifty-seven patients undergoing infrainguinal vein bypass grafting for limb salvage (n = 40) or claudication (n = 17) were prospectively studied. At the time of revascularization, simultaneously acquired intraluminal pressure and blood flow waveforms were digitized at 200 Hz and subjected to Fourier transformation in near real-time. Input impedance was calculated at baseline (immediately after unclamping) and after stimulation with either papaverine or completion arteriography. Resistance (Rin) was calculated as mean pressure divided by mean blood flow (Q). Characteristic impedance (Z0) was calculated as the mean of harmonics 3-10. Intraoperative data acquisition required approximately 5 min, utilized the completion angiography cannula already in place, and was uncomplicated in all patients. Stimulation with either papaverine or arteriography resulted in increased Q (72 +/- 7 to 146 +/- 11 ml/min, p < 0.001), decreased Rin (126 +/- 13 to 52 +/- 4 x 10(3) dyne.s.cm-5, p < 0.001), and slightly decreased Z0 (18 +/- 2 to 15 +/- 1, p = 0.002). After a mean follow-up of 20 months, the 2-year primary patency, secondary patency, limb salvage, and survival rates were 61 +/- 8%, 74 +/- 7%, 76 +/- 6%, and 86 +/- 6%, respectively. Primary patency was not associated with any of the clinical variables studied including age, sex, smoking history, history of previous vascular surgery, hypertension, coronary artery disease, diabetes mellitus, creatinine, indication for revascularization (claudication versus limb salvage), anesthesia (general versus regional), or level of distal anastomosis (popliteal versus infrapopliteal). Furthermore, there was no association between primary patency and baseline Q, baseline Rin, or stimulated Z0. However, using univariate analysis, patency was positively associated with decreased stimulated Rin (p = 0.002), elevated stimulated Q (p = 0.006), and decreased baseline Z0 (p = 0.02). Multiple regression analysis identified stimulated Rin as the only independent predictor of primary patency (p = 0.002). Stimulated Rin > or = 50 x 10(3) dyne.s.cm-5 was 71% sensitive and 65% specific for graft failure. It is concluded that 1) vascular input impedance can be simply and reliably measured in the operating room, and 2) elevated stimulated Rin is an independent predictor of primary patency.

Effects of pulsatile perfusion on human saphenous vein vasoreactivity: a preliminary report.

This study examined the effects of exposure to arterial blood pressure and flow on human saphenous vein catecholamine sensitivity. Unused portions of saphenous vein from eight patients undergoing peripheral bypass procedures were mounted parallel in a specially designed organ culture apparatus and perfused with tissue culture medium with 95% CO(2) at 37 degrees C. One segment was fixed between two cannulas while the medium was gently agitated (control) and the other was actively perfused via a pulsatile pump system at a rate of 60 beats/min, peak pressure of 100 mmHg and peak flow of 200 ml/min (pulsed; mean pressure 60 mmHg; mean flow 115 ml/min). After 48 h, vein segments were removed and tested for in vitro isometric contraction in response to KCI, norepinephrine and histamine, and relaxation in response to acetylcholine, calcium ionophore A23187, and sodium nitroprusside. There were no differences in mean(s.e.m.) maximal contraction in response to KCI (control 0.61(0.16) g versus pulsed 0.72(0.27)g; P = n.s.), norepinephrine (control 1.00(0.56) g versus pulsed 1.51(0.54) g; P= n.s.), or histamine (control 1.47(0.85) g versus pulsed 1.95(0.64) g; P= n.s.). However, pulsed veins exhibited increased sensitivity to both norepinephrine (control -logED50 6.20(0.23) versus pulsed mean(s.e.m.) 6.60(0.17); P< 0.05) and histamine (control -logED(50) 5.60(0.27) versus pulsed 6.24(0.20); P = 0.05). Pulsed veins exhibited slightly less acetylcholine-induced relaxation although the difference did not reach statistical significance (control mean(s.e.m.) relaxation at 1 x 10(6)M 9.2(14.0)% versus pulsed -13.3(6.4)%; P = n.s.). There were no differences in relaxation in response to either A23187 (control 1 x 10-(4)M 178(19)% versus pulsed 191(68)% or sodium nitroprusside (control 225(15)% versus pulsed 254(17)%; P = n.s.). The data presented herein indicate that exposure of human saphenous vein to the hemodynamics of the arterial environment for 48 h results in catecholamine supersensitivity while contractile and relaxant function are not affected.

Pulmonary hemodynamic consequences of ECG-synchronized ventilation.

The pulmonary hemodynamic consequences of ECG-synchronized jet ventilation were studied in an acute closed chest swine model (n = 11). Eight jet timing protocols were compared to conventional mechanical ventilation. Hearts were paced atrially at 120 beats per minute, and analog measurements of pulmonary arterial flow and pulmonary arterial, tracheal, pleural, left atrial, and femoral arterial pressure were digitized in real time at 200 Hz. Fourier analysis of pulmonary artery pressure and flow waveforms was employed to calculate mean and oscillatory right ventricular hydraulic power and pulmonary vascular input impedance. Measurements were taken at 0, 5, and 10 cm H2O of positive end-expiratory pressure (PEEP) during conventional respiration and synchronized ventilation modes. No difference was found in mean pulmonary pressure and flow between conventional and synchronized ventilation at any level of PEEP, regardless of the timing of the jet pulse relative to the cardiac cycle. A significant difference in mean tracheal pressure between conventional and jet ventilation could be found only in the absence of PEEP (3.8 +/- 0.5 vs 2.5 +/- 0.3 mm Hg, P < 0.05). In the absence of PEEP, total hydraulic power was significantly less with respect to conventional ventilation when the jet pulse trailed the QRS complex by 90 and 135 degrees. A significant decrease in the ratio of oscillatory-to-mean power versus conventional respiration was found when jet ventilation lagged the QRS by 135 degrees (0.115 +/- 0.015 vs 0.147 +/- 0.013). These differences did not persist when PEEP was added. Moreover, no significant difference in hemodynamic variables was found when the various jet timing protocols were compared to each other.(ABSTRACT TRUNCATED AT 250 WORDS)

The efficiency of pulmonary blood transport following single lung transplantation.

Perioperative right ventricular (RV) dysfunction remains a significant problem following single lung transplantation (SLT), especially in patients with pulmonary hypertension. Total RV power (Wt), a determinant of RV function, is the sum of the mean component (Wm) which contributes to actual blood flow and the oscillatory component (Wo) which is the energy expended on arterial pulsation. Calculation of Wo is possible only through harmonic analysis of pulmonary arterial (PA) pressure and flow waveforms, and as much as 33% of RV power is attributed to it. The purpose of this study was to precisely quantify changes in RV power output using Fourier analysis of PA pressure and flow waveforms after SLT. Fourteen dogs (donors) were instrumented with a PA ultrasonic flow probe, PA and left atrial (LA) micromanometers, and LA epicardial pacing leads. Control (Pre-Tx) pressure-flow data were acquired during transient occlusion of the right PA at a heart rate of 140. The PA was cannulated, the lungs were flushed with 1 liter of modified Euro-Collins solution at 4 degrees C, and the left lung was harvested and transplanted to 14 recipient dogs in a standard manner. After 1 hr of reperfusion, PA (Post-Tx) pressure-flow data were acquired as above. All recipient animals survived SLT with a mean ischemic time of 183 +/- 3 min. Following SLT, both the mean, Wm, (69 +/- 9 to 161 +/- 23 mW) and oscillatory, Wo, (23 +/- 3 to 46 +/- 10 mW) components of RV power output increased significantly after SLT (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Computer-assisted modeling of blood-flow: theoretical evidence for the existence of optimal flow wave patterns.

The purpose of this study was to model blood-flow waveforms in order to examine the relationship between various waveform shapes and input impedance spectra. Twenty distinct single cardiac cycle flow waveforms having the same mean flow and heart rate were created based on clinical and published observations. The "best" waveform was one with a steep flow upstroke, a high peak flow value, swift deceleration following peak flow, and flow reversal during diastole. Each flow waveform was paired with 20 computer-generated pressure waveforms to calculate input impedance spectra by discrete Fourier transformation. "Favorable" flow waveforms were associated consistently with a lower characteristic impedance (average of 4th-10th harmonics, Zav) irrespective of the shape or magnitude of the input pressure wave. Zav corresponds to the degree of compliance of the vascular bed and could be expected to be lower under favorable outflow conditions and in non-diseased vessels. In conclusion, this study provides theoretical evidence for the existence of optimal flow wave patterns and supports the notion of flow waveform assessment for diagnostic purposes.

Pulmonary arterial impedance after single lung transplantation.

Single lung transplantation (SLT) is emerging as definitive therapy for end-stage pulmonary disease of varying etiology, yet a complete description of the hemodynamic properties of the transplanted lung has not been reported. In this study, Fourier analysis was used to calculate the pulmonary arterial (PA) impedance spectrum before and immediately after SLT to define precisely the pulmonary pressure-flow relationship. Median sternotomies were performed in 18 dogs (donors): an ultrasonic flow probe was placed around the PA and micromanometers were placed in the PA and left atrium (LA). Control PA pressure and flow (PAQ) and LA pressure were measured during transient occlusion of the right PA. The lungs were harvested using cold modified Euro-Collins solution for preservation. After thoracotomy and pneumonectomy, left SLT was performed in 18 recipient dogs with a mean ischemic time of 179 +/- 6 min. After reperfusion for 1 hr, PA pressure and flow data were again collected. Characteristic impedance (Z0), a measure of resistance to pulsatile flow, was compared to input resistance (Rin), a measure of resistance to mean flow, and pulmonary vascular resistance (PVR), the conventional index. Rin is defined as the zeroth harmonic of the impedance spectrum and Z0 as the mean of impedance moduli from 2-12 Hz. All recipients survived transplantation. Both PVR and Rin increased significantly after transplantation (11 +/- 1 vs 19 +/- 3 Wood U, P less than 0.05, and 1352 +/- 121 vs 1964 +/- 244 dyne.sec.cm-5, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Myointimal thickening in experimental vein grafts is dependent on wall tension.

This study examines the relative contributions of intraluminal pressure, blood flow, wall tension, and shear stress to the development of myointimal thickening in experimental vein grafts. To study these different hemodynamic parameters, several experimental models were created in 30 New Zealand White rabbits separated into six groups: common carotid interposition vein grafts harvested at 4 weeks (VG-4) or 12 weeks (VG-12), common carotid-linguofacial vein arteriovenous fistulas harvested at 4 weeks (AVF-4) or 12 weeks (AVF-12), AVFs with partial outflow obstruction harvested at 4 weeks (AVFobs), and combination VG-AVFs in series harvested at 4 weeks (VGAVF). Blood pressure and flow in the graft or vein were measured by use of a transducer-tipped pressure catheter and electromagnetic flow meter. At harvest, veins were perfusion-fixed and proximal, middle, and distal sections were subjected to computerized morphometric analysis. Vein grafts were characterized by a high mean pressure (VG-4, 51 +/- 4; VG-12, 62 +/- 3 mm Hg), low mean flow (VG-4, 17 +/- 1; VG-12, 16 +/- 4 ml/min), large luminal area (VG-4, 19.7 +/- 2.4; VG-12, 19.3 +/- 3.9 mm2), high wall tension (VG-4, 17.0 +/- 1.5; VG-12, 19.5 +/- 2.4 x 10(3) dyne/cm), low shear stress (VG-4, 0.75 +/- 0.13; VG-12, 0.96 +/- 0.38 dyne/cm2), and a high degree of myointimal thickening (VG-4, 5.89 +/- 0.90; VG-12, 4.72 +/- 0.83 mm2). Arteriovenous fistulas were characterized by a low mean pressure (AVF-4, 5 +/- 1, AVF-12, 6 +/- 2 mm Hg), elevated blood flow (AVF-4, 82 +/- 16; AVF-12, 82 +/- 17 ml/min), small luminal area (AVF-4, 2.43 +/- 0.58; AVF-12, 7.14 +/- 2.68), low wall tension (AVF-4, 0.62 +/- 0.19; AVF-12, 0.89 +/- 0.24 x 10(3) dyne/cm), elevated shear stress (AVF-4, 108 +/- 32; AVF-12, 71 +/- 50 dyne/cm2), and decreased myointimal area (AVF-4, 1.18 +/- 0.26; AVF-12, 1.90 +/- 0.55 mm2). The addition of outflow obstruction to AVFs (AVFobs) resulted in elevated pressure (48 +/- 2 mm Hg), decreased flow (17 +/- 4 ml/min), larger luminal area (8.71 +/- 2.31 mm2), elevated wall tension (10.3 +/- 1.7 x 10(3) dyne/cm), and a degree of myointimal thickening approaching that of vein grafts (3.79 +/- 0.66 mm2).(ABSTRACT TRUNCATED AT 400 WORDS)

Origin of the left coronary artery from the pulmonary artery in older adults.

Origin of the left coronary artery from the pulmonary artery is usually a serious clinical problem; untreated, it often causes death. Usually the condition becomes symptomatic early in life, but occasionally symptoms do not manifest until later in childhood. A smaller group will not have symptoms until early adulthood. Rarely, this lesion may be asymptomatic for decades. The reports in the literature and our experience with surgical correction of this condition in patients in their sixth and seventh decades of life are described. One patient is the oldest reported in the world literature to have this condition.

Quantitation of vascular outflow by measurement of impedance.

One of the most important determinants of graft patency is the degree and character of vascular outflow. This study was designed to evaluate input impedance as a functional assessment of the outflow bed of vascular grafts. Four distinct outflow environments were created for external jugular vein conduits in 42 New Zealand white rabbits. Vein grafts (n = 14) were fashioned as end-to-side common carotid interposition bypass grafts. Arteriovenous fistulas (n = 15) were created by side-to-side anastomosis of the distal common carotid artery and linguofacial vein. Arteriovenous fistulas with outflow obstruction (n = 7) were fistulas with a metal clip partially obstructing the distal outflow channel (1 mm lumen). Vein graft/arteriovenous fistula combinations (n = 6) consisted of a vein graft and arteriovenous fistula in series. Pressure and flow in the external jugular vein were measured, and input impedance spectra were calculated by Fourier methods. By use of a PC-based acquisition and processing system, impedance results for 20 cardiac cycles could be obtained in approximately 10 minutes. The results revealed that vein grafts typically demonstrated high resistance to steady state flow (Rin = 235 +/- 50 x 10(3) dyne . sec/cm-5) and steadily decreasing impedance to pulsatile flow resulting in a characteristic impedance (Z0; average of fourth to tenth harmonics) of 35.5 +/- 8.0 x 10(3) dyne . sec/cm-5. Phase angle values were usually negative, especially at low harmonics (first harmonic phase angle = -1.11 +/- 0.10 radians) indicating that flow led pressure. In contrast, arteriovenous fistula Rin was minimal (6.3 +/- 1.4 x 10(3) dyne . sec/cm-5; p less than 0.05 compared to vein graft, and the impedance was flat across the frequency spectrum (Z0 = 8.5 +/- 1.5 x 10(3) dyne . sec/cm-5; p less than 0.05) with pressure and flow nearly in phase (first harmonic phase angle = -0.05 +/- 0.10 radians). Creation of outflow obstruction in arteriovenous fistulas resulted in significantly elevated Rin (136 +/- 41 x 10(3) dyne/sec . cm-5; p less than 0.05 compared to arteriovenous fistula and Z0 (23 +/- 9 x 10(3) dyne . sec/cm-5, p less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Recovery of myocardial function during coronary artery bypass grafting. Intraoperative assessment by pressure-volume loops.

Radionuclide angiocardiography and left ventricular manometry were performed simultaneously in 12 men undergoing elective coronary artery bypass grafting. Pressure-volume loops constructed from these data allow calculation of stroke work and provide a more complete description of global left ventricular function immediately before cardiopulmonary bypass and at a mean of 18 and 34 minutes after termination of ischemic arrest. Early reperfusion was characterized by significant elevation of end-diastolic pressure (p less than 0.01) without a corresponding increase in end-diastolic volume. With continued reperfusion, end-diastolic volume, calculated stroke work, and cardiac output increased significantly with respect to control (p less than 0.05). Heart rate, ejection fraction, mean arterial pressure, stroke work/end-diastolic volume, and maximal dP/dt remained unchanged during the study period. No new focal abnormalities were detected in regional wall motion. These data indicate that minimal residual impairment of diastolic function exists during the acute recovery from cardioplegic arrest and bypass grafting but improves with further reperfusion. Systolic function appears to normalize more rapidly than diastolic function after ischemic arrest.

Intraoperative management of severe endobronchial hemorrhage.

Endobronchial hemorrhage due to pulmonary artery perforation by a Swan-Ganz catheter developed during coronary artery bypass grafting while weaning from cardiopulmonary bypass. After reinstitution of cardio-pulmonary bypass with pulmonary artery venting, bleeding was localized to the right lower lobe bronchus using fiberoptic bronchoscopy. A Fogarty embolectomy catheter was inflated in the bronchus to tamponade successfully only the right lower lobe. This case illustrates a method of distal bronchial blockade for maximal retention of pulmonary function and avoidance of pulmonary resection.

A new method to determine left ventricular pressure-volume loops in the clinical setting.

Left ventricular pressure-volume (P-V) loops provide a complete definition of cardiac performance but have been difficult to obtain in the clinical setting. Accordingly, we have developed a new technique for acquiring P-V loops during and after cardiac surgical procedures using portable first-pass radionuclide angiocardiography coupled with intraventricular micromanometer catheters. Using this technique 35 serial left ventricular P-V loops were acquired in 12 patients during and after coronary artery bypass grafting. Dynamic radionuclide left ventricular volume and micromanometer pressure were acquired simultaneously to generate the P-V loops. Moreover, simultaneous measurement of both volume and pressure allowed comparison of the timing of end diastole (ED) and end systole (ES) defined by each of the two cardiac parameters. For 208 EDs and 243 ESs analyzed volume-defined ED occurred 8 +/- 27 msec (s.d.) later in the cardiac cycle than pressure-defined ED while volume-defined ES occurred 29 +/- 27 msec (s.d.) earlier than pressure-defined ES. It is concluded that measurement of cardiac P-V loops with this new technique is clinically feasible and that a close agreement has been demonstrated between the timing of cardiac events defined either by volume or pressure criteria.