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Biomedical subjects

Jan Klein

Publications and source records attributed to Jan Klein.

At least 37 records · Page 2Linked to original sources
PubMed2005

Effects of recombinant-hemoglobin solutions rHb2.0 and rHb1.1 on blood pressure, intestinal blood flow, and gut oxygenation in a rat model of hemorrhagic shock.

The vasoconstriction induced by hemoglobin-based oxygen carriers (HBOCs), mainly a result of nitric oxide (NO) scavenging, until now has limited the application of HBOCs as resuscitation fluids. In this study, we tested the hypothesis that the new modified recombinant-hemoglobin solution rHb2.0, with a 20 to 30 times lesser NO-scavenging rate, would minimize vasoconstriction without adverse effects on microvascular oxygenation. Responses were compared with those to rHb1.1, a recombinant-hemoglobin solution with a wild-type NO-scavenging rate, as well as an oncotically matched albumin solution. In a fixed-pressure (40 mm Hg) rat model of hemorrhagic shock and resuscitation, rHb2.0 and albumin both restored mean arterial pressure (MAP) to baseline values, whereas rHb1.1 increased MAP to 27% above the baseline value. Mesenteric vascular resistance after resuscitation with rHb2.0 was 57% less than that with rHb1.1. rHb2.0 was found to have 55% greater intestinal oxygen delivery (Do2int ) and resulted in a 27% lower oxygen-extraction rate than did rHb1.1 after resuscitation. Intestinal microvascular Po2 , determined on the basis of oxygen-dependent quenching of palladium-porphyrin phosphorescence, revealed no difference between rHb2.0 and rHb1.1. The findings of this study confirm that the well-known pressure effect of HBOCs is caused by their effect on the NO-scavenging rate; recombinant modification of this rate did not increase MAP during resuscitation compared with baseline values. Although systemic vasoconstriction was absent, intestinal vasoconstriction almost negligible, and Do2int greater after resuscitation with rHb2.0, the effect of rHb2.0 on pH, base-excess and microvascular Po2 levels after resuscitation were comparable to those achieved with the use of the albumin solution.

Animals↗
PubMed2005

Laparoscopic radical prostatectomy--impact of training and supervision.

To define the influence of training and supervision on the quality of laparoscopic radical prostatectomy we compared our perioperative parameters, as well as the postoperative functional and oncological outcomes of four generations of surgeons with significantly different training modalities. The first two generations were trained in open retropubic radical prostatectomy, but the third and fourth generation were trained mostly laparoscopically. Overall the data of more than 1000 performed cases were compared: We could not find any significant difference concerning our complication rates. Also the data of oncological (positive margins) and functional results (data of continence with a follow-up of more than two years) were comparable within all groups. A learning curve was observed only for the operating time, but proved to be significantly shorter for the third and fourth generations. Therefore we can conclude that the quality of laparoscopic radical prostatectomy does not depend on the individual experience in open surgery but to a considerable extent on the quality of laparoscopic education (e.g. simulation trainer, supervision).

Journal Article↗
PubMed2005

The Heilbronn laparoscopic training program for laparoscopic suturing: concept and validation.

BACKGROUND AND PURPOSE: More than a decade after the first description of laparoscopic nephrectomy, an increasing number of laparoscopic procedures are being performed worldwide. Nevertheless, there still exists a significant lack of standardized training programs to teach ablative and, most important, reconstructive laparoscopic operations (i.e., pyeloplasty, radical prostatectomy). We evaluated and validated a new standardized step-by-step program to improve laparoscopic skills and enable trainees not experienced in laparoscopy to perform a urethrovesical anastomosis. MATERIALS AND METHODS: In an inanimate model (pelvic trainer) with defined trocar positions, the 10 participants were exposed to six reconstructive exercises. The steps consist of improvement of hand-eye coordination (two-row metal-pin model; step I), linear and curved suturing with changing angles of the needle (chicken leg and catheter model; steps II-V), and performance of an anastomosis in a porcine bladder (step VI). Times of 3, 15, 15, 10, 20, and 30 minutes for steps I, II, III, IV,V, and VI, respectively, were defined as the goal before proceeding to the next stage. The time required to succeed in each step and the increase in the speed of suturing and knotting activities were analyzed with the Wilcoxon signed-rank test. RESULTS: After a mean of 40 hours of training, all participants were able to perform all steps within the specified times and complete an accurate urethrovesical anastomosis in 30 minutes. The time required to succeed before and after training showed a significant decrease (P < 0.05). Continual training in reconstructive procedures decreased the time needed for suturing activities by between 66.3% and 72.2%. The time needed for the knotting activities decreased by between 34.3% and 38.3%. CONCLUSIONS: Our program enabled participants not experienced in laparoscopy to increase reproducible performance in reconstructive laparoscopy. These results indicate that the challenging parts of reconstructive laparoscopy such as intracorporeal suturing can be taught using a standardized concept. This experience could be incorporated easily by every department developing a laparoscopic training program.

Anastomosis, Surgical↗
PubMed2005

Effects of hyperbaric treatment in cerebral air embolism on intracranial pressure, brain oxygenation, and brain glucose metabolism in the pig.

OBJECTIVE: To evaluate the effects of hyperbaric oxygen treatment after cerebral air embolism on intracranial pressure, brain oxygenation, brain glucose/lactate metabolism, and electroencephalograph. DESIGN: Prospective animal study. SETTING: Hyperbaric chamber. SUBJECTS: Eleven Landrace/Yorkshire pigs. INTERVENTIONS: In 11 anesthetized pigs, intracranial pressure and brain oxygenation were measured with microsensor technology, brain glucose/lactate by microdialysis, and electroencephalograph by conventional methods. After injection of air into the internal carotid artery, animals were treated immediately (at 3 mins; t = 3) or at 60 mins (t = 60) with U.S. Navy Treatment Table 6 for 4.48 hrs. RESULTS: At the end of hyperbaric oxygen treatment, intracranial pressure in the t = 60 group (39 +/- 8 mm Hg) was significantly higher than in the t = 3 group (27 +/- 6 mm Hg), brain oxygenation values for group t = 3 and t = 60 were 66 +/- 14 and 52 +/- 15 mm Hg, respectively (no significant difference from baseline), and there were no pathologic scores in the visually assessed electroencephalograph. However, there was a significant decrease in brain glucose and a significant increase in brain lactate in both groups at the end of the 5-hr study period. CONCLUSIONS: Hyperbaric oxygen treatment initiated at both 3 and 60 mins after embolization decreased the deleterious effects of cerebral air embolism on intracranial pressure and brain metabolism. Therefore, this model appears suitable to test the application of hyperbaric oxygen treatment with a delay >60 mins after embolization, as is often the case in the clinical situation.

Animals↗
PubMed2005

Open lung ventilation improves functional residual capacity after extubation in cardiac surgery.

OBJECTIVE: After cardiac surgery, functional residual capacity (FRC) after extubation is reduced significantly. We hypothesized that ventilation according to the open lung concept (OLC) attenuates FRC reduction after extubation. DESIGN: A prospective, single-center, randomized, controlled clinical study. SETTING: Cardiothoracic operating room and intensive care unit of a university hospital. PATIENTS: Sixty-nine patients scheduled for elective coronary artery bypass graft and/or valve surgery with cardiopulmonary bypass. INTERVENTIONS: Before surgery, patients were randomly assigned to three groups: (1) conventional ventilation (CV); (2) OLC, started after arrival in the intensive care unit (late open lung); and (3) OLC, started directly after intubation (early open lung). In both OLC groups, recruitment maneuvers were applied until Pao2/Fio2 was >375 Torr (50 kPa). No recruitment maneuvers were applied in the CV group. MEASUREMENTS AND MAIN RESULTS: FRC was measured preoperatively and 1, 3, and 5 days after extubation. Peripheral hemoglobin saturation (Spo2) was measured daily till the third day after extubation while the patient was breathing room air. Hypoxemia was defined by an Spo2 value < or =90%. Averaged over the 5 postoperative days, FRC was significantly higher in the early open lung group and tended to be higher in the late open lung group, in comparison with the CV group (mean +/- sem: CV, 1.8 +/- 0.1; late open lung,1.9 +/- 0.1; and early open lung, 2.2 +/- 0.1l). In the CV group, 37% of the patients were hypoxic on the third day after extubation, compared with none of the patients in both OLC groups. CONCLUSIONS: After cardiac surgery, earlier application of OLC resulted in a significantly higher FRC and fewer episodes of hypoxemia than with CV after extubation.

Adult↗
PubMed2005

Multifrequency transducer for microemboli classification and sizing.

The classification of circulating microemboli as gaseous or particulate matter is essential to establish the relevance of the detected embolic signals. Until now, Doppler techniques have failed to determine unambiguously the nature of circulating microemboli. Recently, a new approach based on the analysis of radio frequency (RF) signal and using the nonlinear characteristics of gaseous bubbles to classify emboli was investigated. The main limitation of these studies was the requirement of two separate transducers for transmission and reception. This paper presents a multi-frequency transducer with two independent transmitting elements and a separate receiving part with a wide frequency band. The transmitting elements are positioned in a concentric design and cover a frequency band between 100 and 600 kHz. The receiving part consists of a polyvinylidene fluoride layer. The new transducer has been tested in vitro using gaseous emboli. It could correctly classify and size air emboli with diameters ranging from 10 microm to 105 microm.

Electromagnetic Phenomena↗
PubMed2005

The effect of nitroglycerin on microvascular perfusion and oxygenation during gastric tube reconstruction.

Esophagectomy followed by gastric tube reconstruction is the surgical treatment of choice for patients with esophageal cancer. Complications of the cervical anastomosis are associated with impaired microvascular blood flow (MBF) and ischemia in the gastric fundus. The aim of the present study was to differentiate whether the decrease in MBF is a result of arterial insufficiency or of venous congestion. To do this we assessed MBF, microvascular hemoglobin oxygen saturation (muHbSo(2)), and microvascular hemoglobin concentration (muHbcon) simultaneously during different stages of gastric tube reconstruction. In 14 patients, MBF was determined with laser Doppler flowmetry, and muHbSo(2) and muHbcon were determined with reflectance spectro- photometry. After completion of the anastomosis, nitroglycerin was applied at the fundus. Although MBF did not change significantly in the pylorus, MBF decreased progressively during surgery in the fundus from 210 +/- 18 Arbitrary Units at baseline (normal stomach) to 52 +/- 9 Arbitrary Units after completion of reconstruction (mean +/- sem; P < 0.05). There was no change in muHbSo(2) and muHbcon during the reconstruction. After application of nitroglycerin, MBF doubled. We conclude that MBF decreases during gastric tube reconstruction but that muHbSo(2) and muHbcon do not. This decrease might be the result of venous congestion, which can partly be counteracted by application of nitroglycerin.

Adult↗
PubMed2005

Remifentanil as a single drug for extracorporeal shock wave lithotripsy: a comparison of infusion doses in terms of analgesic potency and side effects.

UNLABELLED: This randomized, double-blind study was designed to evaluate analgesic effectiveness and side effects of two remifentanil infusion rates in patients undergoing extracorporeal shock wave lithotripsy (ESWL) for renal stones. We included 200 patients who were administered remifentanil either 0.05 microg x kg(-1) x min(-1) (n = 100) or 0.1 microg x kg(-1) x min(-1) (n = 100) plus demand bolus of 10 microg of remifentanil via a patient-controlled analgesia (PCA) device. No other sedating drugs were given. The frequencies of PCA demands and deliveries were recorded. Arterial blood pressure, oxygen saturation, and respiratory rate were recorded throughout the procedure; postoperative nausea and vomiting (PONV), dizziness, itching, agitation, and respiratory depression were measured posttreatment. Visual analog scale (VAS) scores were taken preoperatively, directly postoperatively, and 30 min after finishing the procedure. There were no statistically significant differences in the frequency of PCA demands and delivered boluses or among perioperative VAS scores. The extent of PONV and frequency of dizziness and itching immediately after and dizziness 30 min after the end of treatment were significantly reduced in the smaller dose group. We conclude that a remifentanil regimen of 0.05 microg x kg(-1) x min(-1) plus 10 microg demands is superior to 0.1 microg x kg(-1) x min(-1) plus demands, as there was no difference in the VAS scores recorded between groups and it has a less frequent incidence of side effects in patients receiving ESWL. IMPLICATIONS: Remifentanil is an appropriate analgesic choice for patients undergoing extracorporeal shock wave lithotripsy (ESWL) therapy, as it has both fast onset and offset times. We studied remifentanil as a sole drug for ESWL and have shown that an infusion rate of 0.05 microg x kg-1 x min-1 plus patient-controlled analgesia demands of 10 microg provides adequate analgesia and has significantly less side effects than a dose of 0.1 microg x kg-1 x min-1 plus 10 microg demands.

Adolescent↗
PubMed2004

The descent of the antibody-based immune system by gradual evolution.

The antibody-based immune system (AIS) is one of many means by which organisms protect themselves against pathogens and parasites. The AIS is present in jawed vertebrates (gnathostomes) but absent in all other taxa, including jawless vertebrates (agnathans). We argue that the AIS has been assembled from elements that have primarily evolved to serve other functions and incorporated existing molecular cascades, resulting in the appearance of new organs and new types of cells. Some molecules serving other functions have been appropriated by the AIS, whereas others have been modified to serve new functions, either after the duplication of their encoding genes or through the acquisition of an additional function without gene duplication. A few molecules may have been created de novo. The deployment and integration of the ready-made elements gives the impression of a sudden origin of the AIS. In reality, however, the AIS is an example of an organ system that has evolved gradually through a series of small steps over an extended period.

Animals↗
PubMed2004

Prototypic T cell receptor and CD4-like coreceptor are expressed by lymphocytes in the agnathan sea lamprey.

All jawed vertebrates have highly diverse lymphocyte receptors, which allow discrimination between self and nonself antigens as well as the recognition of potential pathogens. Key elements of the anticipatory recombinatorial immune system in jawed vertebrates are the TCR, Ig, and MHC genes, but their ancestral genes have not been found in more basal vertebrates. In this study, we extended our analysis of the transcriptome of lymphocyte-like cells in the lamprey to identify the TCR-like and CD4-like genes. The structural features of these genes and their preferential expression in lymphocytes make them attractive candidates for ancestral TCR and CD4 genes. The TCR-like gene contains both V (variable) and J (joining) sequences in its first exon and exists as a single-copy gene that is invariant. Thus, the TCR-like gene cannot account for the receptor diversity that is required for the immune responses reported for lamprey, but it could have been easily modified to serve as an evolutionary precursor of modern TCR and Ig genes.

Amino Acid Sequence↗
PubMed2004

The phylogenetic relationship of tetrapod, coelacanth, and lungfish revealed by the sequences of forty-four nuclear genes.

The origin of tetrapods is a major outstanding issue in vertebrate phylogeny. Each of the three possible principal hypotheses (coelacanth, lungfish, or neither being the sister group of tetrapods) has found support in different sets of data. In an attempt to resolve the controversy, sequences of 44 nuclear genes encoding amino acid residues at 10,404 positions were obtained and analyzed. However, this large set of sequences did not support conclusively one of the three hypotheses. Apparently, the coelacanth, lungfish, and tetrapod lineages diverged within such a short time interval that at this level of analysis, their relationships appear to be an irresolvable trichotomy.

Animals↗
PubMed2004

Mast cells are involved in inflammatory reactions during Complex Regional Pain Syndrome type 1.

BACKGROUND: The Complex Regional Pain Syndrome type 1 (CRPS1) is a complication of surgery or trauma but spontaneous development is also described. Although the pathogenesis remains debatable, afferent, efferent and central nervous system mechanisms are proposed. Recently we showed involvement of the proinflammatory cytokines IL-6 and TNFalpha which is direct evidence for an inflammatory process. Many types of cells, such as activated T lymphocytes, monocytes, macrophages and skin resident cells like mast cells, could contribute to the production of cytokines. Involvement of mast cells is relatively easy to detect by measurement of tryptase. AIM: To establish whether mast cells are involved in the inflammatory reactions during CRPS1. METHODS: Twenty patients fulfilling the Bruehl criteria with CRPS1 in one extremity were studied. Impairment was assessed by registration of pain and measurement of differences in temperature, volume and mobility between the involved and uninvolved extremity. Blisters were made with a suction method in order to determine cytokines and mast cell derived tryptase in the involved and uninvolved extremity. RESULTS: In the blister fluid a significant difference (median +/- interquartile range, Wilcoxon signed-ranks test P < 0.05) was found between the involved and uninvolved extremity in IL-6 [53.5 (17.3-225) versus 6.2 (2-20.3) pg/ml], TNFalpha [31 (15.5-131.5) versus 8 (4-39) pg/ml], and tryptase [37 (20.5-62.3) versus 12.5 (6.7-23.5) ng/ml]. There was a significant correlation (0.455) between the intensity of pain and tryptase levels in the involved extremity (Spearman's test, P < 0.05). CONCLUSION: Mast cells are involved in inflammatory reactions during the CRPS1. Mast cells could play a role in the production of cytokines such as TNFalpha.

Adult↗
PubMed2004

Hyperventilation impairs brain function in acute cerebral air embolism in pigs.

OBJECTIVE: To evaluate, in a model of cerebral air embolism (CAE), the effects of ventilation-induced hypocapnia and hyperoxemia on intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain oxygen (PbrO(2)), brain carbon dioxide (PbrCO(2)), brain pH (brpH) and levels of brain glucose and lactate. DESIGN AND SETTING: Prospective animal study in a university medical center. SUBJECTS: Fifteen Landrace/Yorkshire pigs. INTERVENTIONS: In 15 anesthetized pigs ICP, PbrO(2), PbrCO(2) and brpH were measured with multi-parameter sensors, and brain glucose and lactate by microdialysis. All these parameters were recorded for 2 h after injection of air into the internal carotid artery. Nine animals were hyperventilated (PaCO(2 )+/-25 mmHg) and hyperoxygenated (FiO(2) 1.0) and six animals were normoventilated (PaCO(2)()+/-40 mmHg with an FiO(2) 0.4) and served as controls. RESULTS. In the treatment group the ICP rose from 8+/-1 to 52+/-6 mmHg, which was similar to that in the control group (12+/-1 to 57+/-8 mmHg). At the end of the 2-h study period, there were no significant differences in PbrO(2), PbrCO(2) and brpH between the two groups. The decreased brain glucose and increased brain lactate reached severe pathological values in both groups by the end of the 2-h study period. CONCLUSIONS: Hypocapnia and hyperoxemia in acute CAE did not improve pathological functional brain parameters compared with normoventilated controls. Similarly, the pathological changes in brain glucose/lactate could also not be improved by hypocapnia and hyperoxemia.

Animals↗
PubMed2004

Computer-assisted skin videothermography is a highly sensitive quality tool in the diagnosis and monitoring of complex regional pain syndrome type I.

The use of thermography in the diagnosis and evaluation of complex regional pain syndrome type 1 (CRPS1) is based on the presence of temperature asymmetries between the involved area of the extremity and the corresponding area of the uninvolved extremity. The interpretation of thermographic images is, however, subjective and not validated for routine use. The objective of the present study was to develop a sensitive, specific and reproducible arithmetical model as the result of computer-assisted infrared thermography in patients with early stage CRPS1 in one hand. Eighteen patients with CRPS1 on one hand and 13 healthy volunteers were included in the study. The severity of the disease was determined by means of pain questionnaires [visual analogue scale (VAS) pain and McGill Pain Questionnaire], measurements of mobility (active range of motion) and oedema volume. Asymmetry between the involved and the uninvolved extremities was calculated by means of the asymmetry factor, the ratio and the average temperature differences. The discrimination power of the three methods was determined by the receiver-operating curve (ROC). The regression between the determined temperature distributions of both extremities was plotted. Subsequently the correlation of the data was calculated. In normal healthy individuals the asymmetry factor was 0.91 (0.01) (SD), whereas in CRPS1 patients this factor was 0.45 (0.07) (SD). The performance of the arithmetic model based on the ROC curve was excellent. The area under the curve was 0.97, the P value was <0.001, the sensitivity 92% and specificity 94%. Furthermore, the temperature asymmetry factor was correlated with the duration of the disease and VAS pain. In conclusion, in resting condition, videothermography is a reliable additive diagnostic tool of early stage CRPS1. This objective tool could be used for monitoring purposes during experimental therapeutic intervention.

Adult↗
PubMed2004

Association between long-term statin use and mortality after successful abdominal aortic aneurysm surgery.

PURPOSE: To assess the potential long-term beneficial effects of statin use after successful abdominal aortic surgery. METHODS: Between 1991 and 2001, 570 patients underwent abdominal aortic aneurysm repair at the Erasmus Medical Center. Of the 519 patients (91%) who survived surgery beyond 30 days, 510 (98%) were followed for a median of 4.7 years (interquartile range, 2.7 to 7.3 years). These patients were evaluated for use of statins and beta-blockers, and for clinical risk factors (e.g., advanced age; prior myocardial infarction; diabetes mellitus; renal dysfunction; chronic pulmonary disease; history of heart failure, stroke, or angina), and their association with all-cause and cardiovascular mortality. RESULTS: A total of 205 patients (40%) died during follow-up; 140 due to cardiovascular causes. The incidence of all-cause (18% [27/154] vs. 50% [178/356], P <0.001) and cardiovascular (11% [17/154] vs. 34% [122/356], P <0.001) mortality was significantly lower in statin users than in nonstatin users. After adjusting for clinical risk factors and beta-blocker use, the association between statin use and reduced all-cause (hazard ratio [HR] = 0.4; 95% confidence interval [CI]: 0.3 to 0.6; P <0.001) and cardiovascular (HR = 0.3; 95% CI: 0.2 to 0.6; P <0.001) mortality persisted. Beta-blocker use was also associated with a significant reduction in all-cause (HR = 0.6; 95% CI: 0.5 to 0.9; P = 0.003) and cardiovascular (HR = 0.7; 95% CI: 0.4 to 0.9; P = 0.03) mortality. There was no evidence of an association between statin use and all-cause and cardiovascular mortality according to beta-blocker use or clinical risk factors. CONCLUSION: Long-term statin use is associated with reduced all-cause and cardiovascular mortality irrespective of clinical risk factors and beta-blocker use.

Adrenergic beta-Antagonists↗
PubMed2004

Aortic stenosis: an underestimated risk factor for perioperative complications in patients undergoing noncardiac surgery.

PURPOSE: To determine the incidence of perioperative events in patients with aortic stenosis undergoing noncardiac surgery. METHODS: We studied 108 patients with moderate (mean gradient, 25 to 49 mm Hg) or severe (mean gradient, > or =50 mm Hg) aortic stenosis and 216 controls who underwent noncardiac surgery between 1991 and 2000 at Erasmus Medical Center. Controls were selected based on calendar year and type of surgery. Details of clinical risk factors, type of surgery, and perioperative management were retrieved from medical records. The main outcome measure was the composite of perioperative mortality and nonfatal myocardial infarction. RESULTS: There was a significantly higher incidence of the composite endpoint in patients with aortic stenosis than in patients without aortic stenosis (14% [15/108] vs. 2% [4/216], P <0.001). This rate of perioperative complications was also substantially higher in patients with severe aortic stenosis compared with patients with moderate aortic stenosis (31% [5/16] vs. 11% [10/92], P = 0.04). After adjusting for cardiac risk factors, aortic stenosis remained a strong predictor of the composite endpoint (odds ratio = 5.2; 95% confidence interval: 1.6 to 17.0). CONCLUSION: Aortic stenosis is a risk factor for perioperative mortality and nonfatal myocardial infarction, and the severity of aortic stenosis is highly predictive of these complications.

Adult↗