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Biomedical subjects

D R Walker

Publications and source records attributed to D R Walker.

At least 55 records · Page 3Linked to original sources
PubMed1992

Response to heparinization in adults and children undergoing cardiac operations.

The activated clotting time is an unreliable index of anticoagulation status during cardiopulmonary bypass procedures. However, modern instrumentation (Hemotec Hepcon HMS) now allows the monitoring of free heparin levels via automated protamine titration. In the present study, the standard procedure of anticoagulation at Killingbeck Hospital, Leeds, was investigated. Twenty-two pediatric patients and 20 adult patients undergoing open heart procedures involving cardiopulmonary bypass were given empirical doses of heparin (3 mg/kg body weight bolus), and activated clotting time was maintained at a level greater than 450 seconds using the Hemochron Timer. Heparin neutralization was performed at the termination of the bypass period using an empirical equivalent (3 mg/kg) of protamine sulfate. Mean free heparin concentration (+/- standard deviation) fell from 2.26 (+/- 0.45) mg/kg to 1.39 (+/- 0.34) mg/kg over the period 10 to 40 minutes on bypass in children. In adults, free heparin level declined from 2.56 (+/- 0.58) mg/kg to 1.81 (+/- 0.58) mg/kg over the same period. The biological half-life for heparin was 60 minutes in adults and 35 minutes in pediatric patients. Empirical protamine dosing resulted in excess protamine administration when compared with Hepcon titrated dose requirements: for children: median (range), 80 (12 to 350) versus 33 (12 to 97) mg, p less than 0.001; and for adults: 350 (200 to 500) versus 130 (61 to 237) mg, p less than 0.001. In conclusion, empirical heparin administration (3 mg/kg) does not result in "steady-state" anticoagulation during cardiopulmonary bypass, and empirical administration of protamine takes no account of interindividual differences in heparin sensitivity and biological half-life, which may be assessed using the Hepcon HMS.

Adult↗
PubMed1992

Angiography of a bronchial carcinoid tumour.

The author describes a patient in whom a bronchial carcinoid tumour was demonstrated preoperatively only by bronchial arteriography. The reported arteriographic characteristics of such a lesion include hypertrophy of the bronchial artery, a tumour blush and the apparent absence of venous drainage.

Adult↗
PubMed1992

Heparin rebound phenomenon--much ado about nothing?

Significant postoperative bleeding following open-heart surgery is often ascribed to the so-called heparin 'rebound' phenomenon and as such is treated with additional empiric doses of protamine sulphate. However, inappropriate protamine administration has been reported to be associated with acute pulmonary hypertension. The efficacy of heparin reversal was investigated in 42 patients undergoing open-heart surgery. The standard heparin bolus of 3 mg/kg body weight (4.1 IU/ml blood) administered before cardiopulmonary bypass was countered at the end of bypass using an empirical equivalent (3 mg/kg) of protamine. This regimen resulted in complete heparin neutralization (measured by the Hepcon HMS [Hemotec Inc., Englewood, CO, USA]) 15 min after protamine administration in all 42 patients, but heparin levels (0.4 IU/ml) were transiently detectable (duration less than 1 h) in six (14%) of the 42 cases 2 h later. Twenty-four hour postoperative bleeding in these patients did not differ significantly from that seen in patients who did not exhibit heparin rebound. Similarly, the thrombelastographic profiles (at 15 min and 2 h post-operation) and coagulation screen (prothrombin time, activated partial thromboplastin time, activated clotting time and platelets) did not differ significantly from those of non-rebound patients. The significance, if any, of the phenomenon of heparin rebound following cardiac surgery remains to be elucidated, and, until such time, conservative administration of protamine in response to 'rebound' is recommended.

Adolescent↗
PubMed1991

Monitoring of coagulation status using thrombelastography during paediatric open heart surgery.

Thrombelastography (TEG) has proved useful in identifying coagulopathies (via assessment of clot elasticity properties) during hepatic surgery, but its role in cardiac surgery has as yet not been defined. Twenty-two children [11M, 11F, mean age (range) 4.9 (0.1-16) years] undergoing open heart surgery were investigated [1] preoperatively, [2] 15 min post protamine, [3] 2 h and [4] 24 h postoperatively using TEG. Comparisons were made between pre- and postoperative measurements and haematological indices. The values obtained from the TEG were: R phase (indicative of thrombokinase and thrombin formation disorders), K phase (indicative of fibrinogenesis) and MA phase (providing information on clot stability and platelet function). The patients were divided into two groups based upon 24 h blood loss; Group 1 - blood loss less than 0.7 ml/kg/h and Group 2 - blood loss greater than 0.7 ml/kg/h. In Group 2 there was a highly significant correlation between post-protamine MA phase and platelet number (r = 0.93, p less than 0.001) but there was no correlation in Group 1 (p greater than 0.1). Furthermore, in Group 2 elevated postoperative blood loss was associated with a prolonged K phase (mean [SD] 12.0 [6.0] versus 6.3 [2.1] min, p less than 0.05) and diminished MA phase (37 [12.5] versus 56 [4.9] mm, p less than 0.01) relative to preoperative values. In Group 1, K and MA phase did not alter significantly (p greater than 0.5 and p greater than 0.2, respectively). TEG predicted with 100% (8/8) accuracy increased post-operative bleeding. The specificity of TEG prediction of future bleeding was 73% [8/11]. Alterations in TEG parameters merit further evaluation as markers of postoperative haemorrhage.

Blood Coagulation↗
PubMed1991

Alternative technique for repair of sinus venosus atrial septal defect.

A technique is described for closure of a sinus venosus atrial septal defect using a single patch held in place by sutures placed from outside the right atrium and underneath the superior vena cava. The superior vena cava does not require enlargement and potential damage to the artery to the sinoatrial node is avoided.

Adolescent↗
PubMed1991

Multiple pulmonary microemboli complicating pneumonectomy.

Pulmonary embolism is widely recognized to complicate abdominal and lower limb orthopedic surgical procedures, but in comparison, it is seldom recognized to hamper the postoperative progress of patients after thoracic operations. We present 4 patients in whom multiple pulmonary emboli developed after pneumonectomy, 2 of whom were treated successfully. We discuss the mostly atypical presentation and the physiological and clinical consequences, and also suggest a mode of management.

Aged↗
PubMed1991

Long-term outcome for children with acute renal failure following cardiac surgery.

Acute renal failure requiring dialysis occurred in 34 children (2.9%) following cardiac surgery over a five year period. 17 children (50%) recovered renal function with 11 (32%) long-term survivors. The long-term outcome for the survivors, in terms of renal function, was studied from 1 to 5 years after their episodes of acute renal failure. Three children had significant abnormalities of renal function despite normal urinalysis. Detailed assessment of renal function is advocated for children who survive acute renal failure following cardiac surgery.

Acute Kidney Injury↗
PubMed1991

Day case ligation of patent ductus arteriosus in preterm infants: a 10 year review.

Since 1978, 136 preterm babies received ligation of a patent ductus arteriosus as day cases. A total of 122 babies whose notes were available for review, with a median gestational age of 27 weeks (range 23-35) and median birth weight of 960 g (range 470-2750), were transported distances of up to 80 miles. The median ages at ligation with and without previous medical management with indomethacin were 23 and 15 days, respectively. One hundred and ten (90%) babies were dependent on ventilatory support, but extubation was achieved at a median time of 10 days after ligation, regardless of postnatal age at the time of ligation. There were no deaths associated with the operation, and no complications resulting from transportation. The hospital mortality was 15 (12.3%), and the most important (and significant) adverse factor was a preoperative fractional inspiratory oxygen content greater than 0.3. The results of this study show that day case ligation of the patent ductus arteriosus is safe, and if it is carried out early will reduce the time before extubation and discharge from the intensive care unit.

Birth Weight↗
PubMed1990

The Killingbeck pediatric lung retractor.

A new series of lung retractors has been designed for use in patients ranging from premature infants to large children. Their unique shape, low profile, and light weight affords excellent exposure with a minimum of trauma to tissues.

Adolescent↗
PubMed1990

Operative insertion of a transvenous left atrial pressure monitoring line.

We describe a technique for the insertion of a left atrial pressure monitoring line during open heart operations in infants. The procedure requires central venous cannulation with a long catheter, followed by intraoperative placement of the catheter tip through the interatrial septum into the left atrium. The technique has been used successfully in 35 infants.

Blood Pressure↗
PubMed1990

Malignant thymoma causing tricuspid valve obstruction.

A 57-year-old man presenting with a retrosternal mass was found to have a malignant thymoma. This was treated with surgery and radiotherapy. It recurred 5 years later as an intra-cardiac mass causing tricuspid valve obstruction.

Heart Valve Diseases↗
PubMed1989

Coarctation of the aorta corrected during the first month of life.

Forty eight children (29 boys) had surgical correction of coarctation of the aorta during the first month of life; all had patent ductus arteriosus. The 33 survivors were reviewed at a mean age of 6.6 years. Of the 19 children with no associated anomaly, none had died. The more complex the associated anomalies, the greater the mortality. Two (6%) of the survivors, both with associated anomalies, have some residual disability; one is incapable of leading an independent life. No survivor has systemic hypertension. Six (18%) of the survivors have required correction of recurrent coarctation, and one is awaiting repair. Newborn babies suspected of having coarctation should be assessed for surgical correction without delay, and medical treatment (including, if necessary, infusion of prostaglandin E2 in a dose of 0.025 micrograms/kg/minute) should be instituted in the interim. Long term follow up is important to detect systemic hypertension or recurrence of the coarctation. This occurred in seven (21%) of our survivors.

Aorta, Thoracic↗
PubMed1988

Giant-cell tumour of the sacrum in a child.

Giant-cell tumours rarely are seen in children before epiphyseal fusion occurs and such tumours in the spine are uncommon. The authors report the case of a giant-cell tumour of the sacrum that developed in a 12-year-old girl before epiphyseal fusion. Embolization with activated microfibrillar collagen relieved her symptoms and was carried out twice before progression of the tumour necessitated radiotherapy. Giant-cell tumours of the spine are particularly difficult to manage since the accepted treatment for such tumours at other sites is wide resection, excisional curettage or surgical curettage with chemical cautery. However, embolization alone or combined with other methods of treatment is valuable, particularly in non-resectable giant-cell tumours of the spine.

Child↗
PubMed1988

Surgical management of thoracic malignancy in childhood: eight years' experience in Leeds.

During the period 1978 to 1986, 13 children aged 2-15 years underwent surgical resection of malignant thoracic tumours. Five children with neuroblastomas presented with chest pain and infections, pleural effusions, dysphagia, lymphadenopathy and paraplegia. Chemo- and radiotherapy were given preoperatively to previously diagnosed cases and postoperatively to all survivors. At operation, complete tumour clearance was possible in only two cases. Two children remain alive with no sign of recurrence at 6 and 7 1/2 years. Eight children with pulmonary metastases had undergone resection of the primary tumour and systemic chemotherapy. All were asymptomatic and were detected by chest radiographs. Wedge resection or lobectomy was performed. Two required contralateral resections at 4 months. Two children remain alive with no evidence of recurrence at 2 and 6 1/2 years. We conclude that aggressive surgical resection of childhood thoracic malignancy is worthwhile, but cooperation with a paediatric oncology team is essential.

Adolescent↗