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Biomedical subjects

R Preston

Publications and source records attributed to R Preston.

At least 37 records · Page 2Linked to original sources
PubMed1996

Increased release of kaliuretic peptide during immersion-induced central hypervolemia in cirrhotic humans.

Kaliuretic peptide is a recently discovered potent stimulator of potassium and water excretion. Its role in modulating renal water handling in cirrhotic patients has not been defined. The responses of circulating kaliuretic peptide and atrial natriuretic factor in 8 cirrhotic subjects to water immersion were significantly greater (p < 0.05) than those of 7 healthy volunteers. With cessation of immersion, atrial natriuretic factor decreased within 30 min to preimmersion values, whereas kaliuretic peptide remained significantly elevated > 1 h, suggesting a slower clearance for kaliuretic peptide. The peak diuretic response to immersion corresponded in a temporal fashion to the peak circulating concentration of kaliuretic peptide, suggesting a possible physiological role of kaliuretic peptide in modulating volume homeostasis in cirrhotic humans.

Adult↗
PubMed1996

Developmental neurotoxicity of methanol exposure by inhalation in rats.

The possibility of widespread methanol exposure via inhalation stemming from its adoption as an automotive fuel or fuel component arouses concerns about the potential vulnerability of the fetal brain. This project was designed to help address such concerns by studying the behavior of neonate and adult rats following perinatal exposure to methanol vapor. Four cohorts of pregnant Long-Evans hooded rats, each cohort consisting of an exposure and a control group, were exposed to 0 parts per million (ppm) (control) or 4,500 ppm methanol vapor for six hours daily beginning on gestation day (GD) 6 with dams and pups then being exposed postnatal day (PND) 21. Exposures took place in 2-m3 Rochester-type inhalation chambers while the animals remained in their plastic breeder cages. Prenatal and postnatal blood methanol concentrations were determined by gas chromatography. Blood methanol concentrations of the dams, measured immediately following a six-hour exposure, were approximately 500 to 800 micrograms/mL throughout gestation and lactation. Average blood methanol concentrations of the pups were about twice those of the dams. Because such results appeared consistently across the other cohorts, we decided to obtain additional data with Cohort 4. Once it had undergone the standard exposure protocol, we selected sets of extra pups from those that had not been assigned previously to the adult phase of behavioral testing. Each set was exposed once, at ages that extended out to PND 52, for one additional six-hour session of exposure to 4,500 ppm methanol. The blood methanol concentrations of these pups declined until about PND 48, at which time they approximated those of the dams. These findings might be accounted for by a process of metabolic maturation in the pups that remains to be identified.

Animals↗
PubMed1996

Anaesthesia--room for advancing nurse practice?

Nurse anaesthesia has been a topic of debate in the UK for many years. I use the word debate loosely because in order to debate one has to be in possession of the facts about the chosen subject. Certainly the subject of nurse anaesthesia evokes very mixed emotions ranging from cautious interest to complete denial that this type of practitioner is of any benefit to the health care industry. Comments such as "it is an idea taken up by some states in the USA and by a number of other countries with a mixed degree of success" and "British anaesthesia ... would neither be improved nor made cheaper by the introduction of nurse anaesthesia" are made from, in this author's opinion, a lack of knowledge about this type of practitioner and their benefits. Accurate and unbiased information about nurse anaesthesia is hard to come by in the UK, therefore, how can accurate comments and opinions be made about this subject.

Certification↗
PubMed1994

Postdural puncture headache and spinal needle design. Metaanalyses.

BACKGROUND: Attempts have been made to reduce the incidence of postdural puncture headache (PDPH) after spinal anesthesia by changing the size and design of the needle. We wished to determine whether these strategies are effective in reducing PDPH and whether they affect the incidence of back pain and the failure rate of spinal anesthesia. METHODS: The literature was searched for trials comparing noncutting spinal needles with cutting needles and larger spinal needles with smaller needles. Trials were included if they were randomized or blinded and if outcomes included PDPH, backache, or failure of the method. The pooled odds ratio for each side effect was computed, and the results were considered statistically significant if the 95% confidence interval excluded 1. RESULTS: Four hundred fifty articles were identified by title using computerized search strategies. Thirty-one abstracts, 25 correspondences, 44 original articles, and 12 reviews were assessed. There was a reduction in the incidence of PDPH when noncutting spinal needles rather than cutting needles were used (P < 0.05), unless the discrepancy in needle size was very large. There also was a reduction in PDPH when a small spinal needle was used compared with a large needle of the same type (P < 0.05). There was no difference in the incidence of failure of spinal anesthesia or the incidence of back pain. CONCLUSIONS: We conclude that a noncutting needle should be used for patients at high risk for PDPH, and the smallest gauge needle available should be used for all patients.

Anesthesia, Spinal↗
PubMed1994

HIV infection in the parturient.

As the incidence of AIDS continues to increase in the female population, there will be more cases of HIV-positive women in the obstetric suite requiring anesthesia services. Many may be asymptomatic, but there will be patients with active opportunistic infections and malignancies who may or may not have been treated. The impact of both the disease AIDS and the drugs used to treat it on anesthetic technique can be significant. Hematological, neurological, respiratory, and immune dysfunction can be expected in a significant proportion of these women. Universal precautions should be utilized for all deliveries regardless of known HIV status. The ubiquitous presence of blood and amniotic fluid during labor and delivery mandate the use of gloves, gowns, and eye protection in the obstetric suite to avoid transmission of HIV to health care workers. Transmission to the newborn during delivery can be minimized by avoidance of skin and mucous membrane trauma and careful removal of secretions and blood. Infected parturients should be carefully assessed for neurological and hematological dysfunction prior to the use of regional anesthesia, and anesthesiologists must be aware of the potential toxicities of therapeutic drug treatment and their impact on anesthesia.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Maternal positioning affects fetal heart rate changes after epidural analgesia for labour.

Adverse fetal heart rate (FHR) changes suggestive of fetal hypoxia are seen in patients with normal term pregnancies after initiation of epidural block for labour analgesia. It was our hypothesis that, in some parturients, these changes were a consequence of concealed aortocaval compression resulting in decreased uterine blood flow. We expected that the full lateral position compared with the wedged supine position would provide more effective prophylaxis against aortocaval compression. To test our hypothesis we studied the role of maternal positioning on FHR changes during onset of epidural analgesia for labour. Eighty-eight ASA Class I or II term parturients were randomized into two groups: those to be nursed in the wedged supine position and those to be nursed in the full lateral position during induction of an epidural block. External FHR monitoring was employed to assess the fetal response to initiation of labour epidural analgesia. Epidural catheters were sited with the parturients in the sitting position and the patients then assumed the study position. After a negative test dose, a standardized regimen of bupivacaine 0.25% was employed to provide labour analgesia. The quality and efficacy of the block were assessed using VAS pain scores, motor block scores and sensory levels. The results demonstrated that there was no difference in the quality of analgesia provided nor in the incidence of asymmetric blocks. There was no difference in the observed incidence of FHR changes occurring during the initiation of the epidural block.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesia, Epidural↗
PubMed1991

Increased release of the N-terminal and C-terminal portions of the atrial natriuretic factor prohormone during immersion-induced central hypervolemia in cirrhotic humans.

The role of peptides from the N-terminus and C-terminus of the 126 amino acid (a.a.) atrial natriuretic factors (ANF) prohormone in modulating renal sodium and water handling in cirrhotic patients has not been defined. Eight cirrhotic individuals were evaluated; their mean basal circulating concentration of the C-terminus (a.a. 99-126; i.e., ANF) was 25 +/- 2 fmol/ml, not different from the 22 +/- 1 fmol/ml value found in 54 normal volunteers. On the other hand, the basal circulating concentrations of the whole N-terminus (a.a. 1-98) and the midportion of the N-terminus (namely a.a. 31-67; pro ANF 31-67) of the ANF prohormone in these cirrhotic subjects of 704 +/- 52 and 654 +/- 83 fmol/ml were significantly elevated (p less than 0.05; ANOVA) in comparison to control values (531 +/- 25, 317 +/- 22 fmol/ml, respectively). Following equilibration on a 10 mmol/day sodium diet, the responsiveness of the N-terminus and C-terminus of ANF prohormone to 3 h of water immersion, which induces marked acute central volume expansion, was evaluated in these 8 seated cirrhotic patients. There was a prompt increase in the circulating concentrations of immunoreactive (ir) pro ANF 1-98 (whole N-terminus), ir pro ANF 31-67, and ir ANF (C-terminus) within 15 min of immersion (p less than 0.05; ANOVA) compared to their preimmersion values. The response of circulating ir pro ANF 1-98, pro ANF 31-67, and ANF concentrations in these 8 cirrhotic subjects to immersion was significantly greater (p less than 0.05; ANOVA) than that of 7 healthy volunteers undergoing an identical 3-hour immersion study. With cessation of immersion, the C-terminus decreased within 30 min to a concentration not significantly different from preimmersion values, whereas the N-terminus and pro ANF 31-67 remained significantly elevated after 1 h.

Adult↗
PubMed1983

The leukemias. Definition, treatment, and nursing care.

While leukemia continues to represent a dreaded, often terminal disease, many new drugs and treatments have been developed in the past two decades. The life span of those afflicted by leukemia has been lengthened, and in some instances the patients have been cured. The treatment is often aggressive with life-threatening side effects. The nurse is faced with many demands when caring for the patient with leukemia who is undergoing therapy. An understanding of the disease process and the treatment is necessary to give optimal nursing care. In addition, the psychologic impact of this disease on patient and family requires time and special interventions from the nursing staff. Care of these challenging patients need not be viewed with pessimism and gloom. When quality care is delivered, both patient and nurse share the gratifying experience of working to achieve the hope and goal of continued life.

Adolescent↗