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Biomedical subjects

R Stewart

Publications and source records attributed to R Stewart.

At least 181 records · Page 10Linked to original sources
PubMed1986

Educational antibiotic advertising.

Antibiotic audits that were conducted within our hospital between 1978 and 1982 showed persisting patterns of inappropriate antibiotic use. A commercial advertising agency was commissioned to plan a campaign to change entrenched prescribing habits. Amoxycillin was chosen as the test drug because previous audits consistently had shown that its intravenous administration was prescribed more frequently than was that of benzylpenicillin in the treatment of primary pneumonia. In addition, amoxycillin given by mouth was prescribed six-hourly rather than eight-hourly in one-third of the patients who were surveyed. A three-month remedial campaign used direct mail (pads and pens), display stands and posters, all of which focused on the booklet Antibiotic guidelines. Educational material was placed wherever staff members congregated. At the end of the campaign, intravenously administered amoxycillin was used in only 8% of 50 patients with primary pneumonia and amoxycillin given by mouth was prescribed six-hourly in only 10% of 99 patients. These changed habits were sustained six months after the campaign but showed some fall-off 18 months after the campaign. The campaign costs of $10,000 were recouped within 12 months by savings on drug costs. It is concluded that educational advertising is an effective means of changing prescribing behaviour in a hospital.

Administration, Oral↗
PubMed1986

The hypoplastic left heart syndrome: evidence of preoperative myocardial and hepatic infarction in spite of prostaglandin therapy.

From February, 1983, to November, 1984, 11 infants with hypoplastic left heart syndrome were managed medically prior to operative intervention. Only 2 of the 11 infants appeared to be in mild distress at birth. Despite relatively normal Apgar scores, 9 of the infants were seen in shock. All patients were managed medically with fluid restriction, diuretics, and the institution of prostaglandin E1. There was a marked improvement in arterial pH from a mean value of 7.13 prior to prostaglandin to 7.42 following prostaglandin infusion. There was also a dramatic decrease in the serum creatinine level from a mean pretreatment level of 1.5 mg/dl to 0.7 mg/dl following infusion. Ten of the 11 infants were operated on at a mean age of 4 days with a Norwood or conduit procedure. Three infants who died at 3, 13, and 24 days of age had sustained myocardial infarctions prior to operation. Three patients also had multiple infarcts of the liver. Three patients are alive 23, 22, and 6 months after operation, and are growing and developing normally. The ability to maintain the infant with hypoplastic left heart syndrome in a stable hemodynamic condition has made surgical palliation a realistic option for this otherwise fatal anomaly. Nevertheless, preoperative infarctions of the heart and viscera continue to play a major role in mortality.

Alprostadil↗
PubMed1986

Cardiac surgery in patients with functional renal transplants.

The results of cardiac surgery in 7 patients with functioning renal transplants are reported. In all cases surgery was carried out using standard operative techniques whilst renal perfusion was enhanced where necessary by the use of a dopamine infusion. The immediate postoperative course was uneventful in all cases, though 2 out of 4 patients with ischemic heart disease have since experienced recurrent symptoms. Cardiac surgery may be performed in patients with functioning renal transplants with acceptable mortality and morbidity.

Adult↗
PubMed1986

Some factors affecting bubble formation with catheter-mediated defibrillator pulses.

Factors affecting bubble formation during delivery of defibrillator pulses to arrhythmogenic cardiac tissue via a catheter are unknown. We investigated the role of energy, electrode surface area, interelectrode distance, and electrode polarity on bubble formation and on current and voltage waveforms during delivery of damped sinusoidal discharges from a standard defibrillator to anticoagulated bovine blood. Gas composition was studied with mass spectrometry. Defibrillator energy settings were varied between 5 and 360 J. The principal catheter used for study was a Medtronic 6992A lead. Additional electrodes tested included 2, 5, and 10 mm long No. 6F, 7F, and 8F copper electrodes. Interelectrode distances used to assess the effect of anode-cathode spacing were 1, 5, 10, and 20 cm. Bubble volume increased linearly from 0.043 to 0.134 ml per cathodal pulse and from 0.030 to 3.50 ml per anodal pulse as energy settings were increased from 5 to 360 J (r = .99). Typical smooth waveforms for both current and voltage were seen only in the absence of bubbles. The voltage waveform was distorted for each cathodal pulse of 100 J or more and for each anodal pulse of 10 J or more only if bubbles were present. The effect of electrode surface area on bubble formation was tested at a 200 J energy setting and at a 10 cm interelectrode distance with the use of cathodal pulses. Bubble formation varied inversely with electrode surface area (r = .876). Bubble formation, however, varied minimally as interelectrode spacing was changed from 1 to 20 cm. The effect of polarity on bubble formation when the Medtronic 6992A distal electrode and an 8.5 cm disk electrode separated by 10 cm were used was highly significant. For a 200 J pulse, bubble formation with the catheter as anode was 3.30 +/- 0.10 ml and with the catheter as cathode it was 0.070 +/- 0.002 ml (p less than .001). Mass spectrometry of both anodal and cathodal gas samples demonstrated the constituents of the gas bubble to include a variety of gases, which is inconsistent with simple electrolytic production of the bubbles observed. The predominance of nitrogen in either polarity sample suggested that the principal source of the bubble was dissolved air. In summary, bubble formation at an electrode receiving damped sinusoidal outputs from a standard defibrillator does not vary significantly with varying interelectrode distance. However, it is directly proportional to energy and inversely proportional to electrode surface area. Anodal catheter discharges produce considerably more bubbles than do cathodal discharges.(ABSTRACT TRUNCATED AT 400 WORDS)

Catheterization↗
PubMed1986

Serial levels of CA 19-9 and CEA in colonic cancer.

The use of serial carbohydrate antigen (CA) 19-9 assays was assessed by comparison with serial carcino-embryonic antigen (CEA) levels on the plasmas of 53 patients with colorectal carcinoma. The patients had all undergone resection for their primary tumors and in six instances subsequent resections for hepatic metastases. Initial CA 19-9 levels were greater than or equal to 37 U/mL in 22 of the 53 patients (41%) and in 68% of the patients with metastatic disease. Similar trends of serial CA 19-9 and CEA levels were found in 79% of the 53 patients. One patient with initially normal CEA levels had elevated CA 19-9 levels from the start. In ten of the 53 patients (19%), serial CA 19-9 levels remained low despite tumor recurrence or progression, and despite increasing CEA levels above 5 ng/mL. The increasing serial CEA trends predicted recurrence in 88% and increasing CA 19-9 trends in 50% of cases, which was increased to 70% by including trends of CA 19-9 levels below 37 U/mL. Following hepatic lobectomy, both serial CEA and CA 19-9 levels decreased rapidly. Used alone, serial CA 19-9 levels did not appear to be as sensitive as standard CEA in this retrospective study of selected patients.

Adult↗
PubMed1986

The asymptomatic pancreatic islet cell tumor: a novel presentation.

Pancreatic islet cell tumors that secrete one or several polypeptide hormones have been suspected and diagnosed secondary to their systemic manifestations. This case report details the diagnosis and treatment of an 62-year-old man with a large pancreatic islet cell tumor without symptoms in whom the mass was found as a direct result of blunt trauma to the abdomen. The tumor contained high concentrations of both vasoactive intestinal polypeptide (VIP) and somatostatin. A discussion of VIP-containing tumors is included.

Achlorhydria↗
PubMed1985

Filling pressures of the heart during anaesthesia.

The validity of extrapolating central venous pressure (CVP) to left ventricular (LV) filling pressure as gauged from the pulmonary artery wedge pressure (PAWP) was investigated in 9 subjects undergoing lung resection. Correlations existed between CVP and PAWP before, during and after surgery, and between changes in CVP and PAWP during surgery. There was, however, a wide scattering of the data around the regression lines, and an inability of the CVP and changes therein to predict the actual and directional change in PAWP in specific individuals. Caution is therefore advised in assessing the LV filling pressure from the CVP in patients undergoing lung resection during any phase of the peri-operative period.

Anesthesia↗
PubMed1985

Graft rejection in a congenic panel of rats with defined immune response genes for MHC class I antigens. I. Rejection of and priming to the RT1Aa antigen.

Allograft rejection in the rat has been shown to be under stringent immune response (Ir) gene control using major histocompatibility complex recombinant animals as donors. Presentation of an isolated class I antigenic difference to high responder recipients results in rapid graft rejection, but low responders fail to reject. This striking qualitative difference is also seen in some liver grafting experiments in which the donor presents a full MHC haplotype and minor antigen mismatch to the responders. Grafts of other organs, however, do not discriminate qualitatively between high and low responders when a full haplotype mismatch exists. We have used the canonical high and low-responder animals, (PVG X PVG-RT1u)F1 and PVG to examine whether any qualitative difference in responsiveness can be detected against the a haplotype using a variety of organ grafts. We have confirmed a qualitative difference between high and low responders using PVG.R1 donors presenting an isolated class I (Aa) difference. Rapid rejection by high responders contrasted with complete failure to reject by the low responders. No difference in rejection tempo was found when a full a haplotype mismatch was introduced. This could have reflected vigorous responses to I and C region differences, because rapid rejection through these regions was demonstrated using the PVG.r1 (AaIcCc) and PVG.r8 (AaIuCu) recombinants. The feeble immunogenicity of the Aa antigen for PVG animals was revealed by priming and cross-priming experiments showing not only that r1 failed to prime for subsequent r1 graft rejection, but that the Aa antigen presented in concert with Ia and Ca also failed to prime. An unexpected result was that the Aa antigen of r1 actually suppressed responsiveness, especially when delivered by a heart graft. This suppression not only extended to subsequent r1 grafts (for example, skin rafts) but also to subsequent grafts of a tissue. The mechanism of this suppression remains unclear but preliminary experiments argue in favor of enhancement rather than active suppression.

Animals↗
PubMed1985

Graft rejection in a congenic panel of rats with defined immune response genes for class I antigens. II. Quantitative aspects of Ir gene function in a full-haplotype mismatch.

Previous studies have shown that the Ir-gene-controlled rejection of rl tissues by c/u responder and non-rejection by c low responders does not extend to tissues expressing a full a haplotype mismatch. However, antibody responses and liver graft rejection are both defective in low responders, even across a full haplotype barrier. We have therefore used a titrated adoptive transfer assay to search for quantitative differences in the responsiveness of c and c/u animals to a organ grafts. We first established that a heart graft rejection could be ablated in both recipient strains with whole-body irradiation and could be restored with syngeneic cells. Titration of restorative cells revealed that 5 times as many c cells were required to restore graft rejection in c recipients as c/u cells were required in c/u recipients. Use of cells from primed donors showed that in both c/u and c animals these cells had undergone about a 5-fold increase in potency, showing that there was no failure of proliferation and differentiation in the low responder after contact with antigens. Cross-transfer experiments were done to attempt to localize the defect in low-responder animals either to a failure of low-responder antigen-presenting cells (APC) to trigger a response or a defect in the responsiveness of alloreactive cells toward the a antigens. In these experiments c cells were obtained from radiation chimeras of the c----c/u type. These cells were used to restore graft rejection in c/u irradiated recipients. Similar experiments employing c/u cells obtained from c/u----c chimeras and given to irradiated c recipients were also done. These showed that c cells from chimeras were marginally less potent than c/u cells from chimeras. In contrast when cross-transfer of c/u cells to c animals bearing a nonrejected rl heart was done, no rejection was seen even when antigen presenting cells were cotransferred. The conclusions from this series of experiments were that quantitatively small defects were present in both repertoire and antigen presentation, and that these quantitative defects in aggregate were probably sufficient to explain the documented low responsiveness of c animals to the a haplotype. The failure of high-responder c/u cells to secure rejection of rl tissues in the low-responder c environment suggests that presentation of isolated class I differences in host APCs is mandatory for rejection to occur and is highly defective in the c animal.

Animals↗
PubMed1983

Use of antibiotic agents in a large teaching hospital. The impact of Antibiotic Guidelines.

Three surveys of antibiotic use have been conducted at The Royal Melbourne Hospital. The first was conducted in 1978, before the introduction of the booklet, Antibiotic Guidelines; the second was conducted eight months after, and the most recent, four years after, its distribution. In 1978, 30% of 563 patients surveyed were receiving antibiotic therapy; this proportion declined to 28% of 967 patients studied in 1982. At the beginning of 1978, 52% of all treatments audited were judged appropriate when compared with those recommended in the Guidelines; this proportion rose to 72% in the second survey and was maintained at 70% in 1982. Certain inappropriate prescribing patterns persisted, such as the use of amoxycillin for the treatment of primary pneumonia, surgical antibiotic prophylaxis which was started too late, and the failure to simplify therapy when the results of microbiological investigations became available. Antibiotic guidelines facilitate the auditing of antibiotic usage and aid rational prescribing. Nevertheless, additional measures appear necessary if specific patterns of misuse of antibiotic agents are to be corrected.

Amoxicillin↗