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W H Baker

Publications and source records attributed to W H Baker.

At least 55 records · Page 3Linked to original sources
PubMed1996

An approach for the use of Doppler ultrasound as a screening tool for hemodynamically significant stenosis (despite heterogeneity of Doppler performance). A multicenter experience. Asymptomatic Carotid Atherosclerosis Study Investigators.

BACKGROUND AND PURPOSE: The Asymptomatic Carotid Atherosclerosis Study (ACAS) Doppler validation study assessed the performance of individual Doppler machines across a spectrum of laboratories. We attempted to establish a threshold specific to individual machines to predict angiographically defined hemodynamic stenosis. The reliability of these Doppler ultrasound criteria was prospectively and independently evaluated among patients screened with ultrasound in the ACAS trial. METHODS: Regression techniques were used to establish the relationship between Doppler velocity and percent stenosis by angiography for 63 specific Doppler machines. This relationship was used to establish a Doppler threshold to provide a 90% positive predictive value (PPV) of a 60% stenosis by angiography. The sensitivity of each Doppler machine to detect a 60% stenosis (at the 90% PPV threshold) was estimated. The efficacy of these Doppler thresholds was then prospectively evaluated by calculating the PPV among ACAS participants eligible by ultrasound. RESULTS: Of the 63 machines, 13 (21%) had an excellent sensitivity (80%+) at 90% PPV. In 32 devices (51%) only a marginal sensitivity (50% to 80%) could be achieved. In 9 devices (14%) the sensitivity was poor (0% to 50%), and in 9 (14%) no threshold could be established. Despite the heterogeneity of Doppler performance, the standardization program worked as designed in the ACAS trial. Of 825 surgical patients, 399 were eligible by Doppler and 395 subsequently underwent angiography. Of these, 32 (8.1%; 95% confidence interval, 5.4% to 10.8%) did not have hemodynamically significant stenosis by arteriography, a proportion nonsignificantly lower than the planned 10% by the PPV. CONCLUSIONS: The performance of Doppler ultrasound was highly variable. This suggests that Doppler performance is likely overstated in the literature, but specific devices may perform satisfactorily to detect individuals with hemodynamically significant stenosis. Because performance differs substantially among devices, local investigators are strongly urged to maintain local standardization series. With such standardization, ultrasound performance is sufficient for admission to clinical trials and as the is sufficient for admission to clinical trials and as the basis for carotid surgery. However, without quality control many ultrasound machines are not adequate to accurately predict the degree of carotid stenosis and should not be the only test to decide whether surgery is warranted.

Angiography↗
PubMed1996

Intensive care after carotid endarterectomy: a prospective evaluation.

BACKGROUND: Through prior investigation we established that only a small minority of patients who undergo carotid endarterectomy (CEA) have a complicated postoperative course requiring an intensive care unit (ICU) stay. An appropriate policy for patient management was established. This study prospectively analyzes the safety and efficacy of this policy. STUDY DESIGN: Patients were transferred directly to a nonmonitored surgical ward, regardless of preoperative comorbidity, if they remained stable from a neurologic and a hemodynamic standpoint during a short (less than three hour) stay in the recovery room. Patients whose status was questionable remained in recovery longer or were transferred to an ICU. RESULTS: One hundred forty-six (79 percent) of 185 patients were transferred safely to a ward. Average length of stay in recovery was one hour 59 minutes. No complications occurred that required a return to the operating suite or a move to an ICU. Most of these patients (88 percent) were discharged within 24 hours of surgery. Thirty-nine (21 percent) patients, each identified in recovery, required intervention or monitoring in an intensive care setting. Fourteen required prolonged, aggressive intravenous treatment of hypertension; 14 had sustained hypotension; three were observed to rule out myocardial infarction, and three had neurologic deficits. Two patients had ventricular arrhythmias, two had wound hematomas, and one patient required reintubation. This group (n = 39) remained in the recovery room two hours 40 minutes on average, spent 20 hours in the ICU, and remained in the hospital 32 hours after CEA. CONCLUSIONS: Most patients who undergo CEA follow a predictably benign postoperative course. Patients are easily identified by a recovery room protocol and approximately 80 percent can avoid ICU costs.

Aged↗
PubMed1995

Bone marrow and splenic granulocyte-macrophage colony-stimulating factor and transforming growth factor-beta mRNA levels in irradiated mice.

The effects of a myeloablative sublethal 775 cGy 60C gamma radiation exposure on endogenous bone marrow (BM) and splenic granulocyte-macrophage colony-stimulating factor (GM-CSF) and transforming growth factor-beta (TGF-beta) mRNA levels were assayed in B6D2F1 female mice. BM and spleen were harvested from normal mice and irradiated mice on days 2, 4, 7, 10, and 14 after exposure. Cytokine mRNA levels were determined using reverse transcription-polymerase chain reaction. After irradiation, GM-CSF mRNA levels were significantly increased in the BM from days 2 to 10 and in the spleen from days 4 to 10. However, when BM and splenic GM-CSF protein levels were measured using Western dot blot, no increased protein levels were detected. Serum GM-CSF levels were likewise unchanged. Radiation exposure did not affect BM or splenic TGF-beta mRNA levels and this cytokine is known to be produced by cell populations similar to those that produce GM-CSF. These data suggest that radiation injury to hemopoietic tissues results in differential effects on GM-CSF and TGF-beta mRNA levels and that, in the case of GM-CSF, increased mRNA levels are not matched by increased protein production.

Agranulocytosis↗
PubMed1995

c-kit ligand gene expression in normal and sublethally irradiated mice.

The c-kit ligand (KL; Steel factor, mast cell growth factor, stem cell factor) is a hematopoietic factor that has been shown to act as a potent cofactor for hematopoietic growth and differentiation in vitro. The in vivo effects of KL, however, have been variable. To study the hematopoietic role of KL in vivo, we evaluated KL gene expression in both normal mice and mice recovering from myelosuppressive radiation exposure using the reverse transcriptase-polymerase chain reaction (RT-PCR) technique. In a single RNA sample, we found that the RT-PCR technique has high precision (co-efficient of variation, 15.7%). Amplifications of serial 1:2 dilutions of template RNA precisely correlated with starting RNA concentrations at 20 cycles or at 25 cycles, depending on the level of expression. Amplification of individual normal bone marrow and spleen cell RNA showed basal expression in all normal bone marrows but irregular expression in normal spleens. On day 2 after a sublethal 7.75-Gy (0.4 Gy/min) 60Co irradiation, splenic KL gene expression increased approximately 2.5-fold (P = .011), and bone marrow expression increased 15-fold (P = .004). During a 28-day postirradiation recovery period, KL expression increased in bone marrow on days 2 through 7. Splenic expression during the same period was more variable. In conclusion, the KL gene is invariably expressed in normal murine spleens. Postirradiation, recovering bone marrow and spleen both express increased levels of KL mRNA at day 2 and continue to express increased levels for several days postexposure. These data support a role for KL in the endogenous recovery of hematopoiesis after hypoplastic injury.

Animals↗
PubMed1995

Selective use of the intensive care unit following carotid endarterectomy.

The purpose of this study was to develop criteria by which selected patients can be observed solely on the ward following carotid endarterectomy (CEA). One hundred consecutive CEA patients were retrospectively reviewed. Preoperative medical conditions were identified, and the postanesthesia recovery room course was reviewed in an attempt to predict the need for intensive care unit (ICU) level care. Forty-four of our 100 patients developed perioperative complications or conditions that required some intervention. Conditions included hypertension in 23, hypotension in nine, arrhythmias in six, and myocardial ischemia in two. Complications included nonfatal cerebrovascular accident (CVA) in one, fatal CVA in one, and postoperative bleeding in two. Sixteen patients required ICU level intervention (hypertension in five, hypotension in five, arrhythmias in two, nonfatal CVA in one, fatal CVA in one, and postoperative bleeding in two. Fifteen of the 16 were identified in the recovery room. Fifty-three patients had a medical history of significant hypertension (42), cardiac disease (27), and/or recent CVA (seven). Thirty-six (68%) of these patients required perioperative intervention in some form; 12 (23%) required ICU level therapy. Eight of 47 (17%) patients without a significant medical history required intervention; only four (9%) required ICU level care. All eight patients were identified in recovery. Only 16 of 100 CEA patients required ICU level care. Fifteen of 16 were identified in recovery. Certain patients identified in the recovery room can be followed safely in a less intense and costly setting.

Adult↗
PubMed1995

Comparison of interleukin-1 alpha gene expression and protein levels in the murine spleen after lethal and sublethal total-body irradiation.

To understand the effects of ionizing radiation on the production of IL-1 alpha in vivo within a hematopoietic organ, we evaluated acute changes in splenic IL-1 alpha mRNA and IL-1 alpha protein after exposing B6D2F1 mice to lethal and sublethal 60Co radiation. Results suggest that in vivo, ionizing radiation induces a time- and dose-dependent accumulation of IL-1 alpha mRNA in the mouse spleen after exposure to gamma radiation. Time-dependent increases in the level of IL-1 alpha protein were also observed, although the magnitude of increased protein expression did not complement the magnitude of the accumulation of the message. Selective concentration of cells producing IL-1 alpha does not appear to account completely for the increase in splenic IL-1 alpha mRNA observed in this in vivo system.

Animals↗
PubMed1994

Residency evaluations. Are they worth the effort?

OBJECTIVE: The accuracy of rotation evaluation forms was assessed to determine the usefulness of clinical performance ratings in predicting competence in a general surgery residency. DESIGN: Longitudinal, 15-year, multifactorial, repeated-measures design. SETTING: University medical center residency training program. PARTICIPANTS: General surgery and subspecialty residents (n = 310) entering postgraduate training from 1976 to 1990 received 6459 rotation evaluations. Predictive efficiency of 4423 evaluations of a subsample of 199 residents admitted to the general surgery program during the study period was assessed using several outcome measures. MAIN OUTCOME MEASURE: Attending surgeons categorized and ranked residents' competence at the completion of training. RESULTS: Rotation evaluations identified 77.8% of residents who involuntarily withdrew. Prediction of outcome category (problem, average, or superior residents), as well as final ranking (R2 = .54), were demonstrated (P < .001). Evaluations of residents from the first year of training onward predicted outcome at the end of training (P < .01). CONCLUSION: Rotation evaluations demonstrate predictive validity in documenting resident performance, particularly when the accuracy of individual raters is known.

Adult↗
PubMed1994

Carotid endarterectomy without arteriography: the preeminent role of the vascular laboratory.

The classic workup of patients considered for carotid endarterectomy (CE) has included contrast arteriography to delineate the nature and extent of the arterial pathology. Noninvasive testing (NIT) consisting of duplex scanning plus sound spectrum analysis is an alternative method for accurately evaluating the carotid bifurcation. The accuracy of our laboratory in comparing NIT to contrast arteriography has been established by use of the guidelines suggested by the Intersocietal Commission for the Accreditation of Vascular Laboratories. Forty-two patients underwent CE based on NIT alone. Seventeen had hemispheric transient ischemic attacks or minor strokes, six had amaurosis fugax, three had nonspecific symptoms, and 16 were asymptomatic. NIT identified a severe stenosis that was limited to the carotid bifurcation; the internal carotid artery distal to the bulb was normal. The predicted stenotic atherosclerotic lesion was confirmed at operation in all patients. One patient had a high bifurcation that required an extension of the original incision. Of three undiagnosed kinked distal internal carotid arteries found at operation, only one required surgical correction. No transient ischemic attacks, strokes, or deaths occurred postoperatively. CE can be performed in selected patients based on NIT alone, obviating the mortality, morbidity, and cost of arteriography. This algorithm demands that the NIT is unequivocal and the accuracy of the testing laboratory is established and maintained according to published standards.

Arteriosclerosis↗
PubMed1994

Intraoperative duplex scanning and late carotid artery stenosis.

PURPOSE: The purpose of this study was to assess the effect of intraoperative duplex scanning on early and late results after carotid endarterectomy. METHODS: We reviewed 316 carotid arteries in 283 patients who underwent operation since 1986. The results of intraoperative ultrasonography were normal in 254 (80.4%) and abnormal in 62 (19.6%). We did not reexplore 53 (85.5%) of the abnormalities because the defect was minor, 2 to 3 mm or less. These defects were retained atheroma in the common carotid artery (n = 35), internal carotid artery (ICA) (n = 5), external carotid artery (n = 2), small frond in the bulb (n = 2), thickened wall of the vein patch (n = 2), and ICA kink (n = 7), two of which were associated with retained atheroma. Nine defects (14.5%) were reexplored and repaired; there were seven flaps, one residual plaque, and one case with turbulent flow alone. RESULTS: Patients with a normal examination result had an early ICA occlusion rate of 0.79% (n = 2), an early stroke rate of 1.6% (n = 4), and one death (0.4%). In the unrepaired group these rates were 1.9% (n = 1) and 1.9% (n = 1), respectively. No occlusion occurred in the repaired group, but one preexisting cerebrovascular accident worsened immediately after operation. Frequency analysis and B-mode imaging were performed after operation and every 6 to 12 months in all patients (mean 21.6 months). A greater than 75% area stenosis was found in nine (17%) of the 53 unrepaired carotid arteries, but in only four (4.3%) of the 254 carotid arteries lacking defects and in one of the reopened group (p < 0.001). There have been no late strokes, and only three late transient ischemic attacks overall. CONCLUSIONS: A normal intraoperative scanning result obtained after carotid endarterectomy is associated with improved late patency rates. Even small defects appear to be associated with an increased incidence of late restenosis, reemphasizing the importance of technical perfection.

Adult↗
PubMed1992

Histopathologic effects of soluble glucan and WR-2721, independently and combined in C3H/HeN mice.

Soluble glucan, an immunomodulator, and Walter Reed (WR)-2721, a radioprotectant, increase postirradiation survival when administered before and after exposure, respectively. Combined, these agents act synergistically through WR-2721's ability to spare hematopoietic stem/progenitor cells from radiation injury and glucan's ability to subsequently stimulate spared cells to proliferate. In this study, the histopathologic effects of WR-2721 (200 mg/kg, ip) and glucan (250 mg/kg, iv), at doses capable of increasing survival in lethally irradiated mice, were evaluated in unirradiated and irradiated female C3H/HeN mice. After treatment, whole body weights and wet organ weights of liver, spleen, and kidney, as well as gross and histologic changes in these and other tissues, were monitored on Days 1, 4, 7, 11, 15, 21, and 28. Morphometric studies of splenic white and red pulps were also performed. Soluble glucan, with or without WR-2721, in unirradiated groups, was associated with splenomegaly, transient morphometrically determined perturbations of white and red pulp areas, and histologic alterations of white pulp. In irradiated mice, splenic weight loss was initially dampened in glucan groups and accompanied by morphologic and histologic changes similar to those seen in unirradiated counterparts. The subsequent rebound of splenic parameters in irradiated mice was limited to WR-2721-treated mice and was associated with hematopoietic reconstitution. Glucan, with or without WR-2721, in unirradiated groups was associated with transient hepatomegaly and associated histologic changes. Similar changes in irradiated animals were seen only in the combined treatment group.

Amifostine↗
PubMed1991

Selection process for surgeons in the Asymptomatic Carotid Atherosclerosis Study.

BACKGROUND AND PURPOSE: The Asymptomatic Carotid Atherosclerosis Study is a prospective, multicenter, randomized clinical trial of carotid endarterectomy for the treatment of asymptomatic hemodynamically significant stenosis. This report describes the selection process for participating surgeons in the trial. METHODS: The Surgical Management Committee established guidelines for minimal annual experience and maximum neurological morbidity and mortality for surgeons to qualify to participate in the study. For approval, a surgeon must perform at least 12 carotid endarterectomies per year. Based on a review of the surgeon's last 50 consecutive endarterectomies, the combined neurological morbidity and mortality rate must be no greater than 5% for all indications and no greater than 3% for endarterectomies performed on asymptomatic patients. RESULTS: One hundred sixty-four surgeons from 48 centers applied for approval: 117 were approved, 17 were rejected, and 30 were not reviewed. The 117 approved surgeons submitted a total of 5,641 endarterectomies with a combined mortality and neurological morbidity rate of 2.3% for the variety of indications for operation. CONCLUSIONS: This overall experience with carotid endarterectomy is one of the largest series reported to date. The data from approved surgeons are well within the range of acceptable neurological morbidity and mortality rates recommended by the Stroke Council of the American Heart Association, which attests to the overall quality of the surgeons participating in the study.

Carotid Artery Diseases↗
PubMed1990

An evaluation of external jugular vein patch angioplasty after carotid endarterectomy.

Seventy-six patients had 91 internal carotid endarterectomies closed with patch angioplasty. There were 36 redo and 55 primary procedures. External jugular vein was used as the patch material in 38, facial vein in nine, Dacron in seven, polytetra flour ethylene (PTFE) in nine, and saphenous vein in 28 operations. There were no perioperative deaths. Five patients required reoperation, but only one required replacement of a defective facial vein. There were five postoperative strokes, but two were related to a contralateral occlusion. Two of the three ipsilateral strokes had a temporary indwelling shunt. Only one patient returned with recurrent neurologic symptoms. Five other restenoses of greater than 75 per cent were noted in three patients. One false aneurysm occurred three months after an external jugular vein patch angioplasty. External jugular vein, although requiring careful handling, is conveniently located in the operative field, does not appear to be associated with increased complications, has excellent long-term results, and allows preservation of the saphenous vein for other bypass surgery.

Adult↗