Biomedical subjects
Publications and source records attributed to M J Mack.
Current methods of insertion of silicone tracheal Y stents can be technically challenging. A simplified method of carinal stent insertion is presented. This method is easy to learn and takes only a few seconds to accomplish.
Contradictory results have been reported regarding risk factors for aortic valve replacement (AVR). This study was designed to investigate determinants of operative mortality for AVR with emphasis on concomitant coronary artery bypass grafting (CABG) and old age. Between January 1986 and June 1992, 371 patients with a mean age of 61.99 +/- 0.76 years underwent AVR. There were 256 men (69.0%) and 115 women (31.0%). Twenty-six patients (7.0%) were 80 years old or older, and 97 (26.1%) were between 70 and 80 years old. Of these patients, 210 (56.6%) had isolated AVR, 142 (38.3%) had concomitant CABG, and 31 (8.4%) had concomitant mitral valve operations. Twenty patients (5.4%) underwent emergency operation. There were 33 operative deaths (8.9%). Univariate analysis and stepwise multiple logistic regression analysis were used to determine the risk factors for operative mortality. In the univariate analysis, 13 preoperative variables (sex, age, history of congestive heart failure, myocardial infarction, arrhythmia, functional class, class I/II versus III/IV, four variables related to aortic valve pathology, ejection fraction, left ventricular function) and 20 perioperative variables (emergency operation, individual surgeon, myocardial protection by type and route of cardioplegia, type of prosthesis, size of prosthesis, mean size by survival, small versus large size, concomitant procedure, concomitant CABG (versus others or AVR alone), concomitant mitral valve operation (versus others or AVR alone), concomitant CABG and MV operation, aortic cross-clamp time, cardiopulmonary bypass time, use and time of insertion of intraaortic balloon pump, low cardiac output, postoperative complications) were examined.(ABSTRACT TRUNCATED AT 250 WORDS)
Coronary artery bypass grafting using bifurcation of the internal mammary artery (IMA) has been reported to have a poor patency rate. To test the hypothesis that the contractility (tendency for spasm) is greater at the bifurcation than at the main IMA, segments of the bifurcation and the distal section of IMA taken from patients with coronary artery bypass grafts were studied in organ baths. The IMA rings were set up at a physiologic pressure. Concentration-response curves were established for norepinephrine, endothelin-1, U46619, potassium, and glyceryl trinitrate (precontracted with 10 nmol/L U46619). Contraction forces were standardized (gram per mm circumference) at a pressure of 100 mm Hg. The diameter was 1.50 +/- 0.08 mm (n = 38) for the bifurcation and 2.03 +/- 0.07 (n = 42) for the main IMA (p < 0.0001). The standardized contraction force was greater in the bifurcation than in the main IMA for norepinephrine (0.82 +/- 0.06 versus 0.54 +/- 0.1; p = 0.02) and endothelin-1 (1.07 +/- 0.11 versus 0.69 +/- 0.07; p = 0.02). No differences were seen for potassium, U46619, or glyceryl trinitrate, whereas the effective concentration that induced 50% of maximal effect for U46619 was 6.17-fold lower in the bifurcation than in the main IMA (9.14 +/- 0.28 versus 8.35 +/- 0.09 -log M; p = 0.003), indicating higher sensitivity in the bifurcation.(ABSTRACT TRUNCATED AT 250 WORDS)
The prevalence and severity of chronic pain after video-assisted thoracic surgery for pulmonary resection remains to be defined. Three hundred forty-three of 391 consecutive patients 3 to 31 months after pulmonary resection by lateral thoracotomy (n = 165) or video-assisted thoracic surgery (n = 178) responded to a questionnaire aimed at comparing the relative occurrence of chronic postoperative pain after video-assisted thoracic surgery and lateral thoracotomy approaches for pulmonary resection. Patients less than 1 year after operation (video-assisted thoracic surgery = 142; thoracotomy = 97) and more than 1 year after operation (video-assisted thoracic surgery = 36; thoracotomy = 68) were analyzed as individual cohorts. Chronic pain was assessed by questioning patients about the presence and the intensity of discomfort on the side of the operation (using a visual analog scale) and their need for analgesic medication and the presence of ongoing limitations in shoulder function. Patients who underwent video-assisted thoracic surgery (less than 1 year from operation) had less pain and subjective shoulder dysfunction although their pain medication requirements were similar to those of thoracotomy patients less than 1 year from operation. After 1 year, there was no significant difference in these "pain related" morbidity parameters between the two surgical approach groups (video-assisted thoracic surgery or thoracotomy).
1. The internal mammary artery has become a preferred coronary bypass graft. Sympathomimetic amines are spasmogens for vasospasm and calcium antagonists are frequently administered drugs perioperatively. The effect of calcium antagonists on alpha-adrenoceptor-mediated contraction depends on the subtype of alpha-adrenoceptor and the type of origin of vascular smooth muscle. This study was designed to investigate the effect of calcium antagonists on alpha-adrenoceptor-mediated contraction in the IMA. 2. Human IMA segments taken from 22 patients undergoing IMA--coronary artery bypass grafting were mounted in an organ bath under the physiological pressure determined from their own length-tension curves. 3. Three ring segments were allocated into three groups. One served as a control and the others were treated with clinically related concentrations of nifedipine (20 or 200 nM) for 25 min before concentration-contraction curves to alpha 1-adrenoceptor agonist methoxamine (MO) or full alpha-adrenoceptor agonist noradrenaline (NA) were established. 4. In separate experiments, the concentration-relaxation curves to nifedipine were established in the IMA rings precontracted with MO (30 microM) or NA (10 microM). Glyceryl trinitrate (GTN, 3 microM) was added to further relax the vessels. 5. Pretreatment with nifedipine (200 nM) only slightly inhibited the MO- (1.74 +/- 0.32 vs 2.88 +/- 0.56 g) or NA- (2.43 +/- 0.66 vs 3.60 +/- 0.82 g) induced contraction without statistical significance (P > 0.05). 6. On the other hand, nifedipine only caused 34.49% relaxation in the MO-precontracted and 24.39% relaxation in the NA-precontracted IMAs. In contrast, GTN caused 76.16% (against MO, P < 0.05) or 92.22% (against NA, P < 0.0001) relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)
1. The internal mammary artery (IMA) is the primary choice as an arterial graft for coronary artery bypass surgery. Endothelin (ET) has been recently measured with an increased release after cardiopulmonary bypass for coronary artery bypass grafting. Threshold concentrations of ET-1 have been found to amplify specifically contractions induced by noradrenaline and serotonin. This study was designed to investigate the effect of glyceryl trinitrate (GTN) and calcium antagonists on ET-1 contraction in the human IMA. 2. Human IMA segments taken from 21 patients undergoing IMA-coronary artery bypass grafting were mounted in an organ bath under the physiological pressure determined from their own length-tension curves. Four ring segments were allocated into four groups. One served as a control and the others were treated with GTN (10, 100 nM, or 30 microM) for 5 min or nifedipine (20 or 200 nM, or 30 microM) for 25 min before concentration-contraction curves to ET-1 were established. In separate experiments, the concentration-relaxation curves to GTN or nifedipine were established in the IMA rings precontracted with ET-1 (10 nM). 3. Pretreatment of IMA with GTN for 5 min did not alter the ET-1-induced contraction. Pretreatment with 20 or 200 nM of nifedipine slightly but not significantly, altered the maximum contraction induced by ET-1. Higher concentrations (30 microM) significantly reduced the maximum contraction force (P = 0.008). On the other hand, GTN caused 76.44 +/- 6.35% relaxation in ET-1-precontracted IMA. In contrast, the nifedipine-induced relaxation was difficult to establish due to unsustained contraction to ET-1.(ABSTRACT TRUNCATED AT 250 WORDS)
Recent studies have shown that blood flow through the internal mammary artery graft is inadequate for maximal exercise and that hypoperfusion may be worsened by high-dose vasopressor therapy that could further reduce arterial graft flow. Histologic studies have suggested that the human internal mammary artery is an elastic "passive conduit" along the majority of its length. However, although the pharmacologic reactivity at the distal section of the internal mammary artery has been extensively studied, this evaluation has never been done at the middle and proximal sections. It is extremely important to understand the contractility at the midsection of the internal mammary artery because, in a critical situation, any contraction may further reduce the internal mammary artery flow. The present study was designed to investigate the following: (1) Is it true that the pharmacologic reactivity of the human internal mammary artery is different among various sections? and (2) Is the human internal mammary artery a nonreactive "passive conduit" at its most important area used as the graft--the middle and the proximal sections? One hundred six human internal mammary artery ring segments taken from patients who underwent internal mammary artery grafting procedures (29 from the proximal, 38 from the middle, and 39 from the distal sections) were studied in the organ bath under a physiologic pressure. Concentration-response curves were established for norepinephrine, endothelin-1, U46619, potassium, and glyceryl trinitrate (precontracted with 10 nmol/L U46619). Contraction forces were standardized (in grams per millimeter circumference) at a pressure of 100 mm Hg. The contraction force was greater in the distal section than in other sections for norepinephrine (p = 0.002) and endothelin-1 (p = 0.04). No differences were seen for potassium, U46619, or glyceryl trinitrate, whereas the effective concentration inducing 50% of maximal response for U46619 was 100-fold lower in the distal than in the middle section (9.06 +/- 0.34 versus 7.06 +/- 0.48 -log M; p = 0.01) indicating higher sensitivity in the distal section. This study for the first time shows various reactivity along the full length of the human internal mammary artery and shows that the distal section is the most reactive part of the graft. However, although the middle and the proximal sections are less reactive to some vasoconstrictors (norepinephrine and endothelin-1), it is not a "passive conduit" and it contracts with all four vasoconstrictors tested.(ABSTRACT TRUNCATED AT 400 WORDS)
Coronary artery bypass grafting has been performed for elderly patients (> or = 70 years) with increasing frequency. From January 1986 through June 1993, 1399 elderly patients underwent isolated coronary bypass grafting. Of these patients, 823 had saphenous vein grafts alone and 576 had internal mammary artery grafting, including unilateral (n = 546) and bilateral (n = 28). Overall operative mortality was 8.86%. Operative mortality for unilateral internal mammary artery grafting (6.41%) was lower than for saphenous vein grafting only (9.96%, p = 0.021) and bilateral internal mammary artery grafting (21.43%, 6/28, p = 0.018). Fewer patients undergoing internal mammary artery grafting had postoperative complications (low cardiac output, intraaortic balloon pumping, and neurologic complications) than patients having saphenous vein grafting only. To determine risk factors for mortality and the influence of internal mammary artery grafting on the outcome, we analyzed 55 variables (27 preoperative, 15 intraoperative, and 13 postoperative) by univariate analysis. Significant variables (age, gender, height, weight, surface area, diabetes, obesity, body mass index, history of congestive heart failure, myocardial infarction, or arrhythmia, functional class, left ventricular ejection fraction, stenosis of the left anterior descending or right coronary artery, emergency operation, reoperation, number of grafts, perfusion time, and bilateral or right internal mammary artery grafting) were included in a stepwise multiple logistic regression analysis. The logistic regression demonstrates that those preoperative (history of congestive heart failure or myocardial infarction, low ejection fraction, female gender, and old age), intraoperative (long cardiopulmonary bypass time, emergency operation, reoperation, and use of right internal mammary artery grafting), and postoperative (postoperative complications) variables are independently associated with higher mortality. This study reveals the high-risk groups in elderly patients undergoing coronary bypass and suggests that a left internal mammary artery graft in combination with saphenous vein grafting may achieve a lower operative mortality and morbidity than other procedures in selected elderly patients undergoing coronary artery bypass grafting.
To investigate risk factors for operative mortality and sternal infection in patients undergoing bilateral internal mammary artery grafting, we analyzed the data of 199 patients who underwent this procedure from January 1986 through June 1992. These patients were also compared with those who underwent only saphenous vein grafting (1664 cases) and those who underwent unilateral internal mammary artery grafting (3359 cases) during the same time frame. The operative mortality was 3.52% (7/199) in the patients having bilateral internal mammary artery grafting, 2.71% (91/3359) in those having unilateral internal mammary artery grafting, and 8.53% (142/1664) in the patients having saphenous vein grafting (p < 0.0001). The occurrence rate of sternal infections was 2.45% (5/199) for bilateral internal mammary artery grafting, 1.32% (13/1664) for saphenous vein grafting, and 1.19% (20/3359) for unilateral internal mammary artery grafting (p = 0.27). The univariate analysis revealed that age, history of congestive heart failure, emergency operation, ejection fraction, and aortic crossclamp time were significantly correlated with operative mortality and that obesity was correlated with sternal wound infection. Stepwise multiple logistic regression identified that old age (> or = 70 years) (p < 0.0001), long perfusion time (p < 0.0001), and emergency operation (p = 0.0004) are risk factors for operative mortality and that obesity (p = 0.0009) is the only significant risk factor for sternal wound infection. We conclude that bilateral internal mammary artery grafting does not increase operative mortality in properly selected patients. However, this procedure should be carefully chosen in elderly (> or = 70 years) patients and for emergency operation. Obese patients have a high risk for sternal infection after bilateral internal mammary artery grafting.
The role of thoracoscopy for the management of intrathoracic diseases has expanded with advancement in endoscopic instrumentation and technology. We report a case of thoracoscopic transdiaphragmatic biopsy of an adrenal gland for metastatic carcinoma. The procedure was uncomplicated and the patient was discharged on the second postoperative day. The morbidity of traditional approaches for adrenal operation was avoided. Thoracoscopy may be a useful approach in selected patients for adrenal operation.
Traditional nonoperative diagnostic approaches to the indeterminate solitary pulmonary nodule include bronchoscopy and percutaneous needle biopsy. Although both methods are minimally invasive, the diagnosis of the small, peripheral nodule may remain elusive. Open thoracotomy is often required when these methods fail to obtain a diagnosis. Between January 1991 and June 1992, 242 patients with indeterminate solitary lung nodules underwent thoracoscopic excisional biopsy as the primary diagnostic method. Wedge excisions of the nodules were all performed by thoracoscopic techniques using an endoscopic stapler alone (72%), neodymium:yttrium-aluminum garnet laser (18%), or both (10%). A definite diagnosis was obtained in all patients. Two patients required conversion to thoracotomy to locate the nodule (both malignant). A benign diagnosis was obtained in 127 patients (52%) and a malignant diagnosis in 115 (48%). Of the malignant nodules, 51 (44%) were primary lung cancer and 64 (56%) were metastases. All patients diagnosed with primary lung cancer having adequate pulmonary reserve (n = 29) underwent formal open lung resection during the same procedure. There was no mortality, and significant morbidity was limited to atelectasis in 3 patients (1.2%), pneumonia in 2 patients (0.8%), and prolonged air leak more than 7 days in 4 patients (1.6%). Average hospital stay for patients having thoracoscopy only (n = 213) was 2.4 days (range, 1 to 12 days). Thoracoscopy offers a minimally invasive approach for the diagnosis of the indeterminate solitary nodule. It has advantages over traditional diagnostic methods of being virtually 100% sensitive and 100% specific with no mortality and minimal morbidity.(ABSTRACT TRUNCATED AT 250 WORDS)
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In the past 2 years, the development of video-assisted thoracic surgery (VATS) has allowed thoracoscopy to rapidly evolve from a primarily diagnostic tool to a therapeutic tool with potentially useful applications. As with laparoscopy, the initial enthusiasm for VATS must be tempered by the reality of technical inadequacies, complications, and results that have yet to withstand careful scientific scrutiny. The purpose of this study was to determine the technical feasibility of a VATS lobectomy. Forty-four patients with primary bronchogenic carcinoma were evaluated and accepted as potential candidates for VATS lobectomy. After complete preoperative staging, these patients were in clinical stage I. All patients had normal arterial blood gases and adequate pulmonary function (forced expiratory volume in 1 second > 1.5 L) to tolerate a lobectomy. At the time of operation, 3 patients were found to have N2 disease and were excluded from the study. In 35 of the remaining 41 patients, a successful VATS lobectomy was accomplished through two thoracoscopy ports and a non-rib-spreading 6- to 8-cm "access" thoracotomy. There were no major intraoperative complications that necessitated conversion to an open thoracotomy. Mean operative time was 153 +/- 26 minutes. All 35 patients recovered uneventfully with a mean hospital stay of 5.7 +/- 1.6 days. A VATS lobectomy is technically feasible using our approach and is potentially safe. However, major advances in thoracoscopy imaging and instrumentation are necessary before this procedure will have the potential for widespread acceptance. Also, the advantages of VATS lobectomy over accepted surgical techniques will have to be carefully documented in randomized trials.
One hundred thirty-eight consecutive, nonrandomized patients, with equivalent demographic and preoperative physiologic parameters, underwent either a video-assisted thoracic surgical (VATS) approach (n = 81) or a limited lateral thoracotomy (LLT) approach (n = 57) to accomplish pulmonary resection for peripheral lung lesions (< or = 3 cm in diameter). Wedge resection was done in 74 VATS patients and 19 LLT patients. Seven patients underwent VATS lobectomy and 38 patients had lobectomy performed through an LLT. Pain was quantitated by postoperative narcotic requirements, the need for intercostal/epidural analgesia, and patient perception of pain index scoring. Shoulder and pulmonary function (forced expiratory volume in 1 second) were measured preoperatively, 3 days postoperatively, and at 3 weeks of follow-up. Patients undergoing VATS experienced significantly less postoperative pain. No patients undergoing VATS required intercostal block/epidural analgesia; 31 LLT patients (54%) required this treatment for breakthrough pain (p = 0.001). Narcotic requirements were less (p = 0.05) among VATS patients, which correlated with lower perception of pain index after operation for VATS patients. Shoulder girdle strength was equally impaired at day 3, but function was more improved in VATS patients at 3 weeks (p = 0.01). Patients undergoing wedge resection alone by LLT had greater impairment in early (day 3) pulmonary function (forced expiratory volume in 1 second) (p = 0.002); this difference from VATS was not sustained at 3 weeks. Video-assisted thoracic surgery is associated with reduced pain, shoulder dysfunction, and early pulmonary impairment compared with LLT for select patients requiring pulmonary resection.
As with any operative procedure, careful preoperative and intraoperative planning are vital to achieving a safe and effective video-assisted thoracic surgical intervention. We outline some of our basic strategies for enhancing the success of this approach in the management of thoracic surgical problems.
Video-assisted thoracic surgery (VATS) procedures are now being performed with increasing frequency. The instrumentation and video equipment continue to evolve and much of this new technology is expensive. We reviewed our experience with VATS in our most recent 150 cases for the purpose of cost analysis. The costs incurred in patients undergoing VATS wedge resection for nodules (n = 45) were compared with those in similar patients having wedge resection using open techniques (n = 31). We found that patients who undergo open resections were more likely to spend time in the intensive care unit after surgery. The anesthesia costs were similar in the two groups. Disposable instrument costs were $623 higher for VATS resection; however, the operative time was shorter (101.4 minutes for VATS versus 122.5 minutes for the open procedure), making the total operating room costs comparable. The length of hospital stay was shorter after VATS resection (4.4 days for VATS versus 6.5 days for the open procedure), resulting in lower total hospital charges in the VATS group; however, this difference was not statistically significant. The cost of a VATS wedge resection for removing peripheral nodules is competitive with that of open techniques. Additional benefits, such as reduced pain, shorter operating times, and decreased hospital stays, make thoracoscopy a valuable diagnostic tool. The length of hospital stay, operating room time, disposable instrument costs, complications, and patient acuity all have an impact on the total costs and vary for different procedures. The operative time has shortened and the use of disposable instrumentation has lessened as our experience with thoracoscopy has increased.(ABSTRACT TRUNCATED AT 250 WORDS)
Thoracoscopy would seem to have several potential advantages over open techniques in terms of the attendant postoperative pain and pulmonary complications. Although many questions exist pertaining to the use of thoracoscopy in the therapeutic management of malignancies of the mediastinum, its use for benign disorders appears desirable. Since December 1990, we have removed 9 mediastinal cysts using a thoracoscopic procedure. These included 7 bronchogenic or enteric cysts, 1 pericardial cyst, and 1 thymic cyst. The average cyst size was 4.2 cm, with 11 cm the largest diameter. Complete removal of the cysts was possible in all but 1 case, in which the cyst adhered to vital structures. A portion of the cyst wall was therefore left intact and the mucosa cauterized. The average hospital stay in these patients was 2.1 days, and there were no intraoperative or postoperative complications. All cysts were benign. The resection of mediastinal cyst using thoracoscopic procedures and based on standard surgical indications would seem to be appropriate. Thoracoscopic removal should be considered as an alternative method to resection of mediastinal cysts.
For anterior approaches to the thoracic spine, a posterolateral thoracotomy has been the standard approach. Recent expanded experience with video-assisted thoracic surgical techniques has allowed us to perform many thoracic spine procedures that previously required open approaches. These procedures include drainage of spinal abscesses, biopsy of vertebral bodies, discectomy for a herniated nucleus pulposus, and anterior releases for kyphoscoliosis. All procedures were successful, but experience is limited and follow-up still short. It is hoped that further experience will prove that this less invasive approach can be widely applied in the practice of thoracic spinal surgery.