PubMed Health⌕ Search

Biomedical subjects

R Knight

Publications and source records attributed to R Knight.

At least 19 recordsLinked to original sources
PubMed1992

Changing perspective on gastrointestinal complications in patients undergoing cardiac surgery.

There has been a documented shift towards increasing age and severity of illness in the patient population undergoing cardiac surgery. To determine if there was a coincident change in frequency, gastrointestinal (GI) complications were prospectively recorded in a consecutive series of 5,438 patients undergoing cardiac surgery from 1983 to 1991. There were 73 complications in 69 patients (incidence = 1.4%) defined as any GI condition that required transfer to an acute care unit, surgical intervention, blood transfusion, or treatment that prolonged the hospital course. Fourteen patients died, a mortality rate of 20% for patients with GI complications (p less than 0.001 versus patients without GI complications). The most frequent complications were those of gastric ulceration despite routine use of H2-receptor blocking agents. Thirty-six patients had upper GI (UGI) bleeding from gastric ulceration with 4 patients requiring operative intervention to control hemorrhage and 6 fatalities in patients with UGI bleeding. Two additional patients died of septic complications following gastroduodenal perforation or penetration. Six patients experienced bowel obstruction or prolonged bowel dysfunction (three Ogilvie's syndrome) with two requiring laparotomy. There were four cases of cholecystitis, two cases of pancreatitis, and the remaining cases were equally divided among common septic complications (diverticulitis and ischemic injury among others). Three patients with massive intestinal infarction died. GI complications were significantly associated with older patients (p less than 0.01) and valve surgery (p = 0.002) but were not more common in women. When considered as a separate group, patients with acid-peptic complications had longer perfusion times, increased use of vasopressors, and more frequent utilization of the intra-aortic balloon pump. In contrast to prior studies, this investigation indicates that GI complications associated with acid-peptic erosion of the UGI tract tend to occur in a different patient group than those with other GI complications. Older patients and/or those with a prior history of peptic ulcer symptoms, as well as those who experience prolonged perfusion times, low cardiac output, or prolonged ventilatory support, should be under rigorous gastric pH surveillance and receive aggressive prophylactic treatment with high-dose H2 antagonists, antacids, and/or sucralfate.

Aged↗
PubMed1992

Pharmacokinetic strategies for cyclosporin therapy in organ transplantation.

Marked interindividual variations in cyclosporin (CsA) produce disparate clinical results in organ transplant recipients. In an attempt to eliminate marked deviations of insufficient or excessive CsA concentrations consequent to the administration of uniform drug doses, test dose pharmacokinetics were performed on each potential organ transplant candidate. An intravenous 3 mg/kg test dose delivered over 3 h proved to be readily performed, namely 53% perfect studies, and relatively reliable, namely 73% of observed concentrations within 10% of the predicted values. Furthermore, the use of CsA doses predicted by pretransplant studies reduces the incidence of delayed graft function, early rejection episodes and transplant loss. The oral test dose study predicted a suitable amount of CsA to achieve sufficient gastrointestinal absorption but was less accurate than the iv prediction method: namely, 40% of observed post-transplant concentrations were within 10% of the predicted target value. Furthermore, patients who received oral doses predicted by the test dose strategy showed no improvement in the incidence of acute rejection episodes between 7 and 60 days, and only modestly improved serum creatinine values. The lower accuracy of predictions from oral test dose studies may reflect the impact of non-linear oral (as opposed to iv) drug pharmacokinetics, of variable diet, and/or of altered postoperative gastrointestinal function.

Administration, Oral↗
PubMed1992

A trial of the prostaglandin E1 analogue, enisoprost, to reverse chronic cyclosporine-associated renal dysfunction.

Cyclosporine (CYA) reduces the renal synthesis of prostaglandins of the E series (PGE). Analogue of PGE1 have been shown to mitigate the vasoconstriction and abnormal renal function of experimental acute CYA nephrotoxicity. We examined the hypothesis that the orally bioavailable PGE analogue enisoprost (EP) would improve renal function in renal transplant recipients chronically exposed to CYA. In a randomized double-blind study, 40 patients at two centers who were being monitored for 3 to 30 months after renal transplantation, were allocated to receive either EP 100 micrograms orally four times daily or placebo (P) for 2 weeks. CYA dosing was fixed at existing levels. There could be no evidence of concurrent acute renal injury, including that of acute rejection. Glomerular filtration rate (GFR) was measured by the clearance of radiolabeled DTPA, while effective renal plasma flow (ERPF) was measured as the clearance of p-aminohippuric acid (PAH). The acute effects of EP were examined twice, by comparing immediate postdose to predose values for GFR and ERPF on day 1 and again on day 14. Chronic effects were examined by comparing baseline (predose) values only for GFR and ERPF between days 1 and 14 and by an examination of creatinine clearances (CCR) on days 0, 14, and 21. At enrollment, patients were well matched for renal function (CCR:EP 47 +/- 5 v P 49 +/- 4 mL/min/1.73 m2; P = NS). Baseline demographics were similar, although patients treated with EP were older (46 +/- 2 v 36 +/- 3 years, mean +/- SEM, P = 0.003). CYA doses and blood levels did not change significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The ability of pretransplant test-dose pharmacokinetic profiles to reduce early adverse events after renal transplantation.

Pretransplant test-dose pharmacokinetic profiles were used to determine individual cyclosporine drug bioavailability and clearance rates in renal transplant patients. Assuming a linear relation between dose and area under the concentration curve (AUC), starting i.v. and p.o. CsA doses were computed from the test-dose results. Target values were 400 ng/ml steady-state concentration (Css) during continuous intravenous infusion, and 500 ng/ml average drug concentration (Cavss = AUC/dosing interval) after oral administration, based upon measurements with the specific monoclonal antibody 3H-tracer radioimmunoassay. The outcomes after dose individualization with a 1-(n = 32), 2-(n = 38), or 3-(n = 41) hr i.v. infusion test dose and a p.o. test dose (n = 111) were compared with 228 historical control patients who received a uniform protocol of CsA i.v. at 2.5 mg/kg/day and p.o. at 14 mg/kg/day. The observed Css after i.v. CsA was within 10% of the target concentration in 73% of recipients tested with the 3-hr protocol, a significantly greater fraction than achieved with either the uniform dose (14%), or the 1-(34%) and 2-(25%) hr protocols. Patients in the 3-hr protocol group showed reduced incidences of delayed graft function, early graft loss, and rejection episodes, and a lower mean serum creatinine value, particularly at 7 but also at 30 days posttransplantation. Administration of the predicted oral dose produced a peak concentration of greater than or equal to 700 ng/ml drug absorption in 60% of recipients at 3 days, 90% at 5 days, and 98% at 7 days. The test-dose method less effectively predicted the appropriate oral CsA dose to produce target Cssav and failed to reduce the 90-day rejection incidence. Despite its limitations with the more-complicated p.o. route, the test-dose method successfully predicts i.v. CsA doses, thereby reducing the incidence of early adverse events.

Administration, Oral↗
PubMed1992

Protozoan infections and HIV-1 infection: a review.

Reactivation of latent infection is the principal mechanism relating Toxoplasma gondii and Pneumocystis carinii to HIV. Less common is reactivation in Leishmania donovani, Trypanosoma cruzi, and microsporidian infections. An impaired primary immune response occurs in all these infections, and also with Cryptosporidium and Isospora belli. Association of HIV infection with gut parasites including Giardia lamblia and Entamoeba histolytica, and also with Trichomonas vaginalis infection is likely to be related to sexual modes of contact that favour both HIV and the parasite. The severity of malaria is not definitely associated with HIV, but Plasmodium falciparum infection may favour more rapid evolution of the HIV infection. Both malaria and trichomoniasis favour HIV transmission; the former by necessitating blood transfusion, and the latter by enhancing viral transmission during sexual contact.

AIDS-Related Opportunistic Infections↗
PubMed1979

Long-term results after surgical correction of Ebstein's anomaly: report of two cases.

Two patients with Ebstein's anomaly had valve replacement with Starr-Edwards cloth-covered valves 11 and 8 years ago. They have been asymptomatic and very active despite the absence of anticoagulation. These cases provide some of the long-term results needed for proper evaluation of the different methods of operative treatment of Ebstein's anomaly.

Adolescent↗
PubMed1978

Enflurane anesthesia and changes of intracranial pressure.

Enflurane has been recommended by some as an ideal agent for use in neuroanesthesia. There is no statistically significant alteration of normal intracranial pressure with enflurane anesthesia. However, supporting a clinical impression, this study demonstrates in dogs that enflurane will significantly increase an already elevated intracranial pressure.

Animals↗