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Biomedical subjects

B Urquhart

Publications and source records attributed to B Urquhart.

At least 19 recordsLinked to original sources
PubMed2001

The efficacy of antifibrinolytics in the reduction of blood loss during complex adult reconstructive spine surgery.

STUDY DESIGN: Controlled study to assess the efficacy of aprotinin and Amicar in reducing blood loss during complex spinal fusions. OBJECTIVES: To compare blood loss and the clotting profile with a thromboelastogram in patients with spinal deformities undergoing sequential anterior and posterior spinal fusions treated intraoperatively with either aprotinin or Amicar. SUMMARY OF BACKGROUND DATA: Spinal fusion for correction of adult spinal deformities is associated with large blood losses despite the implementation of multiple factors to reduce this blood loss. The antifibrinolytics aprotinin and Amicar have both been shown to reduce blood loss in other surgical procedures with the potential for large blood loss. Hence, we compared their efficacy for reducing blood loss in complex spinal fusions. METHODS: Sixty patients for elective sequential anteroposterior thoracolumbosacral fusions were randomly assigned to three groups: control, aprotinin, and Amicar. Patients were assessed for blood loss, transfusion requirements, postoperative complications, and coagulation profile using a thromboelastogram. RESULTS: The study demonstrated a significant reduction in total blood loss (aprotinin 3628 mL, Amicar 4056 mL, control 5181 mL) and transfusion requirements using the half-dose aprotinin regimen compared with Amicar or control. Aprotinin also preserved the thromboelastogram mean clot formation time, clot strength, and clotting index compared with Amicar or control. CONCLUSIONS: For complex spinal operations with large blood losses, the half-dose aprotinin regimen will reduce blood loss and the need for blood components and may have a role in reducing postoperative lung injury.

Aminocaproic Acid↗
PubMed2001

Evidence of lung injury during reconstructive surgery for adult spinal deformities with pulmonary artery pressure monitoring.

STUDY DESIGN: Observational analyses of 55 adult patients who underwent elective sequential anterior-posterior thoracolumbosacral surgical corrections for spinal deformities were used to evaluate the efficacy of pulmonary artery catheter monitoring. OBJECTIVE: To demonstrate that during complex reconstructive surgery for spinal deformities, pulmonary artery catheter monitoring identifies a subset of patients with pulmonary injury and is essential in their management. SUMMARY OF BACKGROUND DATA: Patients who undergo sequential anterior-posterior thoracolumbosacral surgical corrections for spinal deformities experience significant perioperative morbidity. Although the value of pulmonary artery catheter monitoring is controversial, its use in these procedures may help identify potential physiologic complications and improve surgical outcome. METHODS: All patients were monitored with a pulmonary artery catheter during surgery until at least postoperative day 1. Outcome measurements included blood loss, vertebral levels fused, operative time, postoperative respiratory complications, and days in intensive care. RESULTS: Eight (8/55; 14.5%) patients according to pulmonary artery catheter monitoring demonstrated elevated pulmonary vascular resistance and noncardiac pulmonary edema. These patients had longer operative procedures with greater blood loss and had more postoperative respiratory complications. They were treated appropriately in intensive care and discharged without further complications. CONCLUSION: Pulmonary artery catheter monitoring of patients who undergo complex spinal fusion facilitates the identification of patients with pulmonary injury and is essential in the management of these patients in the postoperative period. It may, also, be a marker for embolic injury to the lung.

Adult↗
PubMed2001

Troponin I as a diagnostic marker of a perioperative myocardial infarction in the orthopedic population.

STUDY OBJECTIVE: To assess the utility of troponin I, the only molecular marker of myocardial injury not expressed in regenerating muscle, in diagnosing perioperative myocardial infarction (MI) in the setting of orthopedic surgery where false elevations in creatine kinase MB isoenzymes (CKMB) are known to occur. DESIGN: Prospective study. SETTING: University-affiliated hospital. PATIENTS: 85 patients with risk factors for coronary artery disease (CAD) who were scheduled for orthopedic surgery, including total knee arthroplasty, 34; total hip arthroplasty, 36; posterior spine fusion, 7; and other orthopedic operations, 8. INTERVENTIONS: Patients were observed in the postanesthesia care unit for at least 24 hours where they had an electrocardiogram (ECG) performed, and blood drawn to rule out MI. MEASUREMENTS: Blood samples for measurement of creatine kinase MB isoenzymes (CKMB) and troponin I were drawn at 8-hour intervals for up to 24 hours. MAIN RESULTS: Five (5/85) patients had elevated levels of both CKMB and troponin I postoperatively. New ECG abnormalities were present in all but one patient who had an old anterolateral MI. Troponin I peaked within 16 hours except in one patient where it continued to increase. That female patient developed cardiogenic pulmonary edema. All the others did well clinically. Six patients (6/85) had a positive CKMB index, and a negative troponin I level. None had ECG changes, except for one in whom subsequent cardiac catheterization showed insignificant CAD. They all did well clinically. All patients with an elevated troponin I level had a positive CKMB index. CONCLUSIONS: Troponin I is as sensitive a marker of MI as CKMB in the orthopedic population, but it has a higher specificity in the perioperative setting. Troponin I can be helpful in properly identifying the source of CKMB elevation postoperatively when this elevation is questionable.

Aged↗
PubMed1997

Effect of epidural analgesia on venous blood flow after hip arthroplasty.

The effects of postoperative epidural infusions using local anesthetic and narcotic were assessed in reference to lower extremity blood flow. Nineteen patients who underwent unilateral total hip arthroplasty were randomly assigned to receive a postoperative epidural infusion of either 5 microg/ml fentanyl or 5 microg/ml fentanyl plus 0.125% bupivacaine at a rate of 10 ml per hour. The infusions were started after complete resolution of the operative epidural blockade. Femoral venous blood flow volume and velocity were measured above and below the saphenous vein bifurcation using an Acuson #128XP/10 computed sonography system (duplex ultrasound) and proprietary software. Femoral venous blood flow was not affected by the type of infusion and did not increase during the study period. However, femoral venous blood flow volume increased 50% after active flexion and extension of the foot, 10 times in quick succession. The addition of bupivacaine (a local anesthetic that blocks sympathetic afferent nerves) to a postoperative epidural infusion does not augment blood flow from the deep veins of the leg after total hip arthroplasty. Alternatively, lower extremity skeletal muscle activity significantly enhances femoral venous blood flow and may be a useful adjunct in deep venous thrombosis prevention.

Aged↗
PubMed1993

Factors affecting deep vein thrombosis rate following total knee arthroplasty under epidural anesthesia.

A retrospective review was performed of 448 consecutive patients undergoing primary, unilateral, bicondylar, and cemented total knee arthroplasty under epidural anesthesia by three surgeons to determine factors contributing to deep vein thrombosis rate. All had venography on the fourth or fifth postoperative day and received aspirin and elastic stockings as their only thromboprophylaxis. The overall deep vein thrombosis rate was 41% (2% had proximal clots). The rate of deep vein thrombosis was not related to obesity, history of heart disease, hypertension, prior malignancy, smoking, diagnosis of osteoarthritis, duration of surgery, type of local anesthetic used, or the use of postoperative epidural analgesia. The rate of deep vein thrombosis varied significantly between surgeons: one surgeon had an overall deep vein thrombosis rate of 58% (proximal thrombi, 4%) whereas the other two surgeons had a deep vein thrombosis rate of 35% (proximal clot thrombi, 1%). A number of possible mechanisms to explain the variation in deep vein thrombosis rates between surgeons are provided.

Aged↗
PubMed1993

Factors influencing deep vein thrombosis following total hip arthroplasty under epidural anesthesia.

To determine intraoperative factors which may influence deep vein thrombosis rate, we studied surgeries performed by one surgeon on 441 consecutive patients undergoing primary total hip arthroplasty under epidural anesthesia. Operative limb venography was performed on the fourth or fifth postoperative day in 381 patients, who received 650 mg of aspirin daily as the only postoperative thromboprophylaxis. Of 381 (15%) patients, 58 had a positive venogram; 13 (3%) had proximal thrombi. Of 178 patients (9.5%) with surgery lasting less than 70 min, 17 developed deep vein thrombosis whereas 41 of 203 patients (20.3%) with surgery lasting more than 70 min developed deep vein thrombosis (P < 0.05). Corresponding proximal deep vein thrombosis rates increased from 1.7% to 4.9%. Deep vein thrombosis was observed in 12.5% of patients receiving intravenous low-dose epinephrine, 10.3% receiving intravenous sodium nitroprusside, 14.5% receiving both low-dose epinephrine and sodium nitroprusside concurrently, and 25% receiving intravenous fluid alone. Proximal deep vein thrombosis rates were 2.4%, 0%, 1.45%, and 9.3% in these groups, respectively. These data suggest that the intraoperative management of both surgery and anesthesia influence rates of deep vein thrombosis following total hip arthroplasty.

Adolescent↗
PubMed1993

Supraventricular tachyarrhythmias during total joint arthroplasty. Incidence and risk.

Perioperative supraventricular tachyarrhythmias (AF/SVT) have been long recognized as a complication after major surgery, but little is known about the incidence after major nonthoracic surgery. One thousand two hundred ten consecutive patients undergoing total hip or knee arthroplasty were studied to determine the incidence of new onset AF/SVT. Information on preoperative medical history and laboratory tests were collected in a subset of 583 patients, and analyzed using logistic regression and linear analysis to determine risk. Ninety-four-and-one-half percent of patients received an epidural anesthetic, 4.1% had general anesthesia and 1.3% had spinal anesthesia. New onset AF/SVT was found in 38 of 1210 patients, representing an incidence of 3.1%. In the subset of 583 patients, the incidence was 4.8%. The only variables found to be independently associated with the perioperative development of AF/SVT were a history of atrial fibrillation, increasing age, left anterior hemi-block, and atrial premature depolarizations on the preoperative electrocardiogram. In those patients 60 years of age or older with one or more positive risk factors (13% of the study population), the incidence was 18.2%. In those patients less than 60 years of age with none of the identified risks, the incidence was 1.9%.

Adult↗
PubMed1993

The effect of two levels of hypotension on intraoperative blood loss during total hip arthroplasty performed under lumbar epidural anesthesia.

The degree of induced hypotension necessary to achieve a significant reduction in intraoperative blood loss has never been defined. Forty patients undergoing primary total hip arthroplasty during epidural anesthesia by a single surgeon were randomly assigned to have mean arterial pressure maintained at 50 +/- 5 mm Hg or 60 +/- 5 mm Hg throughout surgery. Intraoperative blood loss was 179 +/- 73 mL in the 50 mm Hg group and 263 +/- 98 mL in the 60 mm Hg group (P = 0.004). Subjectively, there was more bleeding during surgery in the 60 mm Hg group during dissection of the hip joint (P = 0.0026) and while reaming the acetabulum (P = 0.0001) and femur (P = 0.0001). No difference in transfusion requirements, postoperative hematocrit, or duration of surgery was noted. A difference in mean arterial blood pressure of 10 mm Hg from 50 to 60 mm Hg during surgery for total hip arthroplasty under epidural anesthesia has a measurable effect on intraoperative blood loss.

Aged↗
PubMed1991

Haemodynamic effects and outcome analysis of hypotensive extradural anaesthesia in controlled hypertensive patients undergoing total hip arthroplasty.

We have examined the safety of induced hypotension produced by extradural anaesthesia in patients with medically controlled hypertension. The haemodynamic response to induced hypotension was assessed in 38 non-hypertensive and 31 controlled hypertensive patients. All received extradural anaesthesia to T4 or above which decreased mean arterial pressure to 52 mm Hg and 55 mm Hg in normotensive and hypertensive patients, respectively. Cardiac output (thermodilution) was maintained by low dose i.v. infusions of adrenaline (1-5 micrograms min-1). No differences in the haemodynamic response to induced hypotension were observed in hypertensive patients. Data were collected also from 987 consecutive patients (353 hypertensive and 634 non-hypertensive) undergoing total hip replacement. Patients with hypertension were significantly older (68 vs 60 yr; P less than 0.001) and had greater ASA ratings (P less than 0.001). The smallest recorded systolic pressures were reduced more in patients with hypertension (57% vs 52%, respectively; P less than 0.001). The mean duration of maintained intraoperative hypotension (100 and 98 min) and estimated intraoperative blood loss (278 vs 281 ml) were similar in each group. After operation, two patients developed myocardial infarctions. None developed acute renal failure or stroke. There were three deaths; one of a patient who had hypertension. This suggests that induced hypotension with extradural anaesthesia is a safe technique for patients with medically controlled hypertension undergoing total hip arthroplasty.

Adult↗
PubMed1991

Effect of hypotensive epidural anaesthesia on acetabular cement-bone fixation in total hip arthroplasty.

We selected 20 matched pairs of patients who had had total hip arthroplasty by the same surgeon using the same cemented technique. Matching was by age, sex, height, weight and diagnosis. One of each pair had received hypotensive epidural anaesthesia, with less than 300 ml blood loss: the other had normotensive general anaesthesia with more than 500 ml of blood loss. Early postoperative radiographs were evaluated independently by three blinded observers, using a scoring criteria which assessed the quality of the cement-bone interface. The results showed that patients who had received epidural anaesthesia had significantly better radiographic scores (p less than 0.02). Our findings suggest that hypotensive anaesthesia facilitates penetration of cement into bone.

Anesthesia, Epidural↗
PubMed1991

Effects of epidural anesthesia on the incidence of deep-vein thrombosis after total knee arthroplasty.

Epidural anesthesia has been reported to reduce the prevalence of deep-vein thrombosis after total hip arthroplasty compared with the prevalence after general anesthesia. However, the effect of epidural anesthesia on the rate of thrombosis after total knee arthroplasty has not been reported previously, to our knowledge. A review was conducted of 705 total knee arthroplasties (541 patients) that had been performed by a single surgeon between September 1984 and December 1988. During this period, the operative technique, the protocol for rehabilitation, and the regimen for prophylaxis against thromboembolism did not change meaningfully. The patients received either epidural or general anesthesia. Preoperative and postoperative perfusion scans of the lungs and a venogram of the lower limb or limbs that had been operated on were done for all patients. For the 227 patients who had received epidural anesthesia, the over-all rate of deep-vein thrombosis was 48 per cent, which was significantly lower than the 64 per cent incidence in the 264 patients who had received general anesthesia (p less than 0.0001). The greatest reduction was in the occurrence of proximal thrombosis, which was identified in 9 per cent of the patients who had had general anesthesia but in only 4 per cent of those who had had epidural anesthesia (p less than 0.05). The use of epidural anesthesia reduced the incidence of proximal thrombosis after both unilateral and one-stage bilateral arthroplasty.

Adult↗
PubMed1990

Extradural anaesthesia in patients with previous lumbar spine surgery.

We studied prospectively 1381 patients undergoing extradural anaesthesia for total hip or total knee replacement, to determine if extradural anaesthesia can be performed reliably in patients who have had previous lumbar spine surgery. Fifty-two of the 57 patients (91.2%) who had undergone lumbar spine surgery received a successful extradural anaesthetic, and 1307 of 1324 patients without previous back surgery had successful extradural anaesthesia (98.7% success) (P less than 0.0001). No late complications were observed. Causes for failure of extradural anaesthesia in patients who had previously undergone lumbar spine surgery included technical difficulty (three) and inadequate spread (two).

Anesthesia, Epidural↗
PubMed1980

Rat brain cyclic AMP levels and withdrawal behavior following treatment with t-butanol.

1. The time course development of physical dependence as assessed by the withdrawal reaction was identical for ethanol and t-butanol. 2. t-Butanol is most likely not metabolized by the liver and is eliminated from the rat 6 to 7% as rapidly as ethanol. 3. Blood and brain acetaldehyde could not be detected following treatment with t-butanol. 4. At the peak of withdrawal, cyclic AMP levels were indistinguishable from control values following treatment with either ethanol or t-butanol.

Acetaldehyde↗
PubMedDate not supplied

Increased specificity in measuring satisfaction.

The authors report a patient satisfaction study that addressed some of the methodological limitations of previous studies and attempted to increase the variance in satisfaction assessment by increasing the scope and specificity of inquiry. Same sex patient/therapist match, duration of therapy, individual therapy and treatment with staff social workers rather than psychiatric residents all were positively correlated with increased patient satisfaction. Satisfaction appeared to be a unitary dimension that could be tapped by a global score. Nonetheless, although overall satisfaction was high, one third of patients preferred an alternative treatment.

Adult↗
PubMedDate not supplied

Hemodynamic changes associated with tourniquet use under epidural anesthesia for total knee arthroplasty.

BACKGROUND AND OBJECTIVES: Epidural anesthesia is administered commonly for total knee arthroplasty, a procedure using a thigh tourniquet. Tourniquet use has been associated with intraoperative hypertension and with occasional circulatory collapse after deflation. The purpose of this study was to define the hemodynamic changes in this setting. METHODS: We prospectively studied 373 consecutive patients having a total knee arthroplasty performed under epidural anesthesia, with continuous electrocardiogram and radial artery pressure monitoring. Results were analyzed using Student's t-test, correlation coefficients, analysis of variance, or chi-square analysis. Alpha was set at 0.01. RESULTS: There was a 4 +/- 11 mmHg rise in mean arterial pressure throughout the period of tourniquet application (p less than 0.001); no clinically significant hypertension occurred. After tourniquet deflation, there was a 19.2 +/- 12% reduction in mean arterial pressure, occurring within one minute. The magnitude of mean arterial pressure reduction failed to correlate with any clinical parameter other than vasopressor use. There was a small subset of patients who had a fall in heart rate and a more profound degree of hypotension after tourniquet deflation, but these patients could not be identified before tourniquet release. CONCLUSIONS: In this setting, tourniquet-induced hypertension is rare. However, hypotension after deflation is common, occurs rapidly, and correlates poorly with clinical parameters.

Adult↗