PubMed Health⌕ Search

Biomedical subjects

D F Landers

Publications and source records attributed to D F Landers.

At least 19 recordsLinked to original sources
PubMed1999

Assessment of changes in coagulation in parturients with preeclampsia using thromboelastography.

BACKGROUND: Preeclampsia is associated with a risk of abnormal hemostasis that occurs most commonly secondary to thrombocytopenia. Thromboelastography measures whole blood coagulation and has been used to manage coagulation defects in obstetric patients. The authors conducted this investigation in a large number of preeclamptic women to assess changes in coagulation using thromboelastography. METHODS: Thromboelastography and platelet counts were performed in 52 healthy pregnant women, 140 mild preeclamptic women, and 114 severe preeclamptic women in active labor using disposable plastic cups and pins and native whole blood. In preeclamptic patients with a platelet count <100,000/mm3, conventional coagulation tests were also performed. Epidural analgesia was provided in some women when they requested pain relief. RESULTS: Fifteen percent of all preeclamptic women (38 of 254) and 2% (1 of 52) of healthy pregnant women had a platelet count <100,000/mm3. The incidence of thrombocytopenia <100,000/mm3 was 3% (4 of 140) and 30% (34 of 114) in mild preeclamptic patients and severe preeclamptic patients, respectively. Severe preeclamptic patients with a platelet count <100,000/mm3 were significantly hypocoagulable when compared to the other study groups. Ten severe preeclamptic women with a platelet count <100,000/mm3 had a maximum amplitude <54 mm (the lower limit of maximum amplitude in healthy pregnant women enrolled in this investigation). None of the mild preeclamptic women had a maximum amplitude <54 mm. Five severe preeclamptic women with a platelet count <100,000/mm3 had an abnormal coagulation profile, whereas all four mild preeclamptic women with a platelet count <100,000/mm3 had a normal coagulation profile. CONCLUSION: This study shows that severe preeclamptic women with a platelet count <100,000/mm3 are hypocoagulable when compared to healthy pregnant women and other preeclamptic women.

Adult↗
PubMed1998

Audit in transfusion practice.

Given the growing concern for the safety, cost and adequacy of blood supply, there is an increasing need for appropriate blood product utilization. Despite a number of consensus guidelines for the transfusion of allogeneic blood products, inappropriate blood transfusion continues. We discuss the quality assurance process for improvement in transfusion therapy including audit of blood transfusion. Audits identify areas of problems in transfusion practice which can be corrected by education of doctors, formulation of practice guidelines and algorithms. To improve the effectiveness of the audit programmes, the frequency of audits has to be maintained and there should be continual reinforcement of policies.

Blood Transfusion↗
PubMed1997

The influence of cardiopulmonary bypass on cytokines and cell-cell communication.

Cardiopulmonary bypass (CPB) is characterized by systemic endotoxemia immediately after its onset as well as the systemic release of proinflammatory cytokines, including tumor necrosis factor-alpha and the interleukins 1 and 6. Recent studies document that increased morbidity and mortality rates correlate with elevated systemic concentrations of these proinflammatory cytokines during adult and neonatal sepsis, following thoracoabdominal aortic aneurysm repair, as well as following CPB. These proinflammatory cytokines induce increased neutrophil and endothelial surface adhesive molecule expression, thereby promoting enhanced neutrophil-endothelial adherence. Increased neutrophil-endothelial adherence and subsequent neutrophil organ binding are thought to be a "final common pathway" of organ injury during clinical inflammatory conditions. Proinflammatory cytokines also increase cellular expression of inducible nitric oxide synthase, thus increasing cellular production of nitric oxide, a known inflammatory mediator. This review discusses recent evidence of the adverse effects of proinflammatory cytokine release during CPB and therapeutic modalities that can reduce the systemic concentrations of these mediators of inflammation.

Adult↗
PubMed1995

Energy status in anoxic rat hepatocytes: effects of isoflurane, solution composition, and hypothermia.

Both cold and warm ischemia occur during liver transplantation. Hypothermia and Wisconsin solution preserve adenine nucleotide energy status, which is crucial to hepatic function and viability. The volatile anesthetic isoflurane has been shown to preserve energy status in anoxic isolated hepatocytes in warm Krebs solution. The present study examined isoflurane effects on energy status during incubation also in Wisconsin or Krebs-plus-adenosine solution at 37 degrees or 4 degrees. Hepatocytes were isolated from rat liver after perfusion with Krebs + collagenase. In 25-mL flasks, 12.5 million cells in 2.5 mL of Krebs, Krebs plus 5 mmol/L adenosine, or Wisconsin solution were incubated under an atmosphere of O2/CO2 or N2/CO2 (19:1) +/- isoflurane (3 volumes% = 2ED50), for 30 minutes at 37 degrees C or 4 degrees C. Adenine nucleotides were measured by high-performance liquid chromatography (HPLC), lactate enzymatically. During warm (37 degrees) anoxia, Wisconsin solution preserved energy status; Krebs plus adenosine did not. Isoflurane further protected energy status in all three solutions. Hypothermia (4 degrees) alone greatly decreased anoxic loss of energy status in all solutions. In Wisconsin solution only, energy status tended to be higher in anoxic than in oxygenated cells and was further enhanced by isoflurane, with corresponding increases in lactate. During 30 minutes of either warm or cold anoxia, isoflurane and Wisconsin solution each helped preserve adenine nucleotide energy status in isolated hepatocytes, at least in part through enhanced glycolysis.

Adenine Nucleotides↗
PubMed1994

Isoflurane isomers differ in preservation of ATP in anoxic rat hepatocytes.

The volatile anesthetic isoflurane inhibits the precipitous drop of ATP concentration that results from induced anoxia in isolated rat hepatocytes. This change is dose dependent and reaches its maximum at clinically relevant anesthetic concentrations. The use of highly purified isoflurane enantiomers has allowed a demonstration of the difference in the efficacy of the (+) and (-) isomers on the isoflurane-dependent preservation of ATP. The difference in relative potency between isomers was approximately 2.5-fold, with the (-) form being more potent. In a direct test of the anesthetic potency of these isomers, it was shown previously that the (+) isomer was more potent than the (-) isomer. Differences in the order of potency of isoflurane stereoisomers for the "anesthetic" and "metabolic" effects of isoflurane suggest that these effects are independent and may result from interactions with different specific molecular sites.

Adenosine Triphosphate↗
PubMed1993

Plasma laudanosine levels in patients given atracurium during liver transplantation.

Atracurium, a nondepolarizing muscle relaxant, does not depend on the liver for clearance, but its principal metabolite, laudanosine, is eliminated primarily by the liver and is potentially neurotoxic. We measured atracurium and laudanosine levels in 15 adult patients during the three stages of liver transplantation to assess the effect of major impairment of liver function. Atracurium was given in a bolus dose of 0.5 mg/kg followed by continuous infusion at a rate adjusted to maintain 95-99% of total neuromuscular block, as judged by train of four response to facial nerve stimulation. Atracurium levels remained constant at 1.4-1.8 micrograms/mL during the 180-min preanhepatic and 75-min anhepatic stages but decreased to a mean of 1.0 microgram/mL by the end of the 180-min postanhepatic stage. In contrast, laudanosine levels increased during each stage, being 0.40 +/- 0.18, 0.50 +/- 0.22, and 0.43 +/- 0.16 micrograms/mL after the preanhepatic, anhepatic, and postanhepatic stages, respectively. The highest individual value recorded was 1.02 microgram/mL. We conclude that, despite increases in laudanosine levels during each stage of liver transplantation in patients receiving atracurium, those levels are only about one-tenth of the maximum values previously reported in humans.

Adult↗
PubMed1993

Effects of isoflurane dose, duration of anoxia, and reoxygenation on isoflurane's preservation of energy balance in anoxic isolated hepatocytes.

We investigated how the protection of energy status by isoflurane in isolated hepatocytes varied with isoflurane dose, duration of anoxia, and reoxygenation. Hepatocytes were isolated from fed rats and incubated in Krebs buffer under O2/CO2 or N2/CO2 (95/5) for 30 or 90 min, followed by 5 or 30 min of reoxygenation. From measurements of adenosine tri-, di-, and monophosphate (ATP, ADP, AMP) in the cells, energy charge (= [ATP + 1/2 ADP]/[ATP + ADP + AMP]) was calculated to reflect the balance between ATP supply and demand, and total adenine nucleotide (= ATP + ADP + AMP) to indicate the potential maximum ATP level. During 30 min of anoxia, energy charge and total adenine nucleotide steadily increased with isoflurane dose from 0 to 2 minimum alveolar anesthetic concentration, then decreased from 2 to 3 minimum alveolar anesthetic concentration. In short incubations (30-35 min) at 1 minimum alveolar anesthetic concentration isoflurane, there was a modest decrease in energy charge during anoxia, partially prevented by isoflurane and completely reversed by reoxygenation, and no decrease in total adenine nucleotide. In long incubations (90-120 min), there were large decreases in both energy charge and total adenine nucleotide during anoxia, with partial and no reversal by reoxygenation, respectively. Isoflurane partly prevented decreases in both energy charge and total adenine nucleotide during both anoxia and reoxygenation. We conclude that at doses in the clinical range, isoflurane partially protected isolated hepatocytes against decreases in both energy charge and total adenine nucleotide occurring either during short (reversible) or long (irreversible) anoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMed1992

Identity of a membrane-bound vasoactive intestinal peptide-binding protein with calmodulin.

A vasoactive intestinal peptide (VIP)-binding protein purified from guinea pig lung membranes (p18) was digested with trypsin, and the amino acid sequence of the peptide fragments was determined. The sequence of six tryptic fragments of p18 was identical with subsequences present in mammalian calmodulin. Authentic porcine brain calmodulin and p18 co-migrated on an sodium dodecyl sulfate-electrophoresis gel and displayed identical chromatographic behavior on a reverse phase high performance liquid chromatography column. The VIP-binding properties of p18 and calmodulin were indistinguishable. Both proteins displayed saturable and apparent high affinity binding of VIP, evidenced by potent inhibition of complexation with [Tyr10-125I]VIP by unlabeled VIP (IC50 = 6.0-8.1 nM). Rat growth hormone releasing factor and a C terminally extended form of VIP ([Leu17]VIP-GKR) also displayed potent inhibition of the binding (IC50 = 6.4 and 4 nM, respectively). These neuropeptides are potential modulators of calmodulin function.

Amino Acid Sequence↗
PubMed1992

Lecture practices in United States anesthesiology residencies.

We obtained data on lecture practices from 100 of the 110 university-affiliated anesthesiology residency programs certified in the United States in 1988. Of these residency programs, 36% had a majority of their lectures before the operating room schedule began, 57% had no lectures at all in this early time slot, and 78% had morning lectures at least once a week in conjunction with a delayed operating room start. Seventy-one percent of programs had one or more afternoon lectures each week. An attendance of more than 80% was reported in 66% of the programs for morning lectures and in 50% of the programs for afternoon lectures, which is a significant difference. Aggregate pass rates on the American Board of Anesthesiology written examinations in 1987 and 1988 correlated significantly with morning-lecture attendance, but not with afternoon-lecture attendance, number of lecture days per week, or mandatory lecture attendance. These findings suggest the need for further study and definition of the role of lectures in resident education in anesthesiology.

Anesthesiology↗
PubMed1991

Effects of neuroleptic agents on rat skeletal muscle contracture in vitro.

The purpose of this investigation was to examine and compare the effects of both in vivo pretreatment and in vitro treatment with the neuroleptic agents droperidol, haloperidol, and trifluoperazine on skeletal muscle contracture using an in vitro model. Strips of normal rat diaphragm were challenged with succinylcholine and halothane (halothane: 1% and 3%) subsequent to either in vitro administration (10-100 microM) or in vivo pretreatment (0.35-2.80 mg/kg) with droperidol, haloperidol, or trifluoperazine. After equilibration, maximum increases in tension were recorded and mean data analyzed by analysis of variance (P less than 0.05). When either droperidol or trifluoperazine was administered in vivo, contracture values after exposure to succinylcholine and halothane were significantly decreased. After in vivo pretreatment with haloperidol or in vitro administration of droperidol, succinylcholine-induced contractures were significantly reduced; contractures subsequently induced by halothane did not significantly differ from that of controls. In vitro treatment with haloperidol and trifluoperazine, however, produced significant increases in tension in muscles exposed to succinylcholine and halothane. This study provides evidence that droperidol may be considered a safe anesthetic adjunct in malignant hyperthermia-susceptible patients, and, additionally, that caution should be exercised when interpreting results from studies in which contracture testing is performed on muscle from patients treated with neuroleptic agents.

Animals↗
PubMed1991

Isoflurane partially preserves energy balance in isolated hepatocytes during in vitro anoxia.

We investigated whether a volatile anesthetic (1.5% isoflurane or 1.0% halothane) or an added anaerobic energy source (10 mM glucose or fructose) could act directly on liver cells to protect energy status during 20-30 min of anoxia. We used hepatocytes freshly isolated from fed rats or rats that had fasted, suspended them in Krebs' buffer, and incubated them in sealed flasks under O2/CO2 or N2/CO2 (95%:5%). The adenosine triphosphate (ATP) to adenosine diphosphate (ADP) ratio (ATP/ADP) measured cellular energy balance--the balance between overall ATP supply and demand. Lactate levels measured the extent to which ATP was supplied by the nonmitochondrial pathway, (anaerobic) glycolysis. Maximum values of energy balance were seen in cells from fed rats incubated in the presence of glucose and O2. When glucose was replaced by fructose, ATP/ADP decreased and lactate increased. During anoxia (O2 replaced by N2), increases in lactate were also seen with glucose; and ATP/ADP decreased to similarly low values with both substrates. In cells from fasted rats, ATP/ADP decreased significantly below the value for cells from fed rats only in the presence of glucose and O2. Compared with cells from fed rats, cells from fasted rats showed decreased lactate in the face of decreased ATP/ADP, suggesting that glycolysis was impaired. Isoflurane partially prevented anoxia-induced decreases in ATP/ADP. This protective effect on energy balance occurred equally with glucose and fructose, but was not seen in cells from fasted rats or with halothane. Thus, 1 MAC isoflurane and some factor(s) related to the fed state combined to protect partially the energy balance in anoxic liver cells through action(s) at the cellular level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗