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Biomedical subjects

Jan Klein

Publications and source records attributed to Jan Klein.

At least 19 recordsLinked to original sources
PubMed2007

A randomized prospective study comparing the Cobra Perilaryngeal Airway and Laryngeal Mask Airway-Classic during controlled ventilation for gynecological laparoscopy.

BACKGROUND: An increasing number of noninvasive, supraglottic airway devices are currently available. In this randomized single-blind study, we compared the Cobra Perilaryngeal Airway (CobraPLA) to the [Laryngeal Mask Airway (LMA)-Classic] during gynecological laparoscopy. METHODS: Forty patients received either an LMA-Classic or a CobraPLA. Insertion, ventilation and removal characteristics were noted, as well as any throat morbidity. RESULTS: Devices were similar for insertion characteristics, adverse events, and throat morbidity. Before pneumoperitoneum, peak airway pressures were 20.3 +/- 4.9 cm H2O in the LMA-Classic group versus 25.5 +/- 7.9 cm H2O in the CobraPLA group, P = 0.01. This difference was maintained during pneumoperitoneum; LMA-Classic (22.8 +/- 6.1 cm H2O) and CobraPLA (28.1 +/- 8.5 cm H2O), P = 0.04. Macroscopic blood occurred only on the CobraPLA, seen on 40% of the devices after removal, P = 0.001. CONCLUSION: During gynecological laparoscopy, the CobraPLA provides similar insertion characteristics, but higher airway sealing pressures than the LMA-Classic. The usefulness of this finding requires further investigation.

Adult↗
PubMed2007

Increased preoperative glucose levels are associated with perioperative mortality in patients undergoing noncardiac, nonvascular surgery.

OBJECTIVE: To determine the relationship between preoperative glucose levels and perioperative mortality in noncardiac, nonvascular surgery. RESEARCH DESIGN AND METHODS: We performed a case-control study in a cohort of 108 593 patients who underwent noncardiac surgery at the Erasmus MC during 1991-2001. Cases were 989 patients who underwent elective noncardiac, nonvascular surgery and died within 30 days during hospital stay. From the remaining patients, 1879 matched controls (age, sex, calendar year, and type of surgery) were selected. Information was obtained regarding the presence of cardiac risk factors, medication, and preoperative laboratory results. Preoperative random glucose levels <5.6 mmol/l (110 mg/dl) were normal. Impaired glucose levels in the range of 5.6-11.1 mmol/l were prediabetes. Glucose levels >or=11.1 mmol/l (200 mg/dl) were diabetes. RESULTS: Preoperative glucose levels were available in 904 cases and 1247 controls. A cardiovascular complication was the primary cause of death in 207 (23%) cases. Prediabetes glucose levels were associated with a 1.7-fold increased mortality risk compared with normoglycemic levels (adjusted odds ratio (OR) 1.7 and 95% confidence interval (CI) 1.4-2.1; P<0.001). Diabetes glucose levels were associated with a 2.1-fold increased risk (adjusted OR 2.1 and 95% CI 1.3-3.5; P<0.001). In cases with cardiovascular death, prediabetes glucose levels had a threefold increased cardiovascular mortality risk (adjusted OR 3.0 and 95% CI 1.7-5.1) and diabetes glucose levels had a fourfold increased cardiovascular mortality risk (OR 4.0 and 95% CI 1.3-12). CONCLUSIONS: Preoperative hyperglycemia is associated with increased (cardiovascular) mortality in patients undergoing noncardiac, nonvascular surgery.

Aged↗
PubMed2006

The radius surgical system - a new device for complex minimally invasive procedures in urology?

OBJECTIVE: Complex laparoscopic procedures in urology are technically demanding with an extended learning curve. Robotic systems add significant cost to laparoscopic procedures. We therefore evaluated the use of the Radius Surgical System (RSS), a mechanical manipulator, for complex laparoscopic cases in urology. MATERIAL AND METHODS: The RSS (Tuebingen Scientific) consists of two hand-guided surgical manipulators and provides a deflectable and rotatable tip allowing six degrees of freedom. We evaluated the system by using a series of standardized models in the pelvitrainer. We analyzed the effectiveness of the system and the learning curve. We then evaluated the system in the clinical setting during laparoscopic radical prostatectomy. RESULTS: Surgeons with experience on the RSS were compared to surgeons without previous experience on the system. We identified a learning curve in those participants without experience on the system only when performing complete anastomoses in the pelvitrainer. However, this learning curve included less than 10 anastomoses. The first clinical experiences during laparoscopic extraperitoneal radical prostatectomy (n=10) are promising. All anastomoses were patent on routine (X-ray) examination 8 days after surgery. CONCLUSIONS: The RSS system is easy to use and we identified a very short learning curve. We now optimize the system for use in urology. This device may facilitate complex laparoscopic procedures without the use of costly robotic systems and should be further evaluated in the experimental and clinical setting.

Equipment Design↗
PubMed2006

Assessing the predictive validity and efficacy of a multimodal training programme for laparoscopic radical prostatectomy (LRP).

OBJECTIVES: To assess the predictive validity (ability to correlate to real-life environment) and efficacy of a training programme for laparoscopic radical prostatectomy (LRP), based on a structured and progressive pelvitrainer component with hands-on clinical training in the operating room (OR). METHODS: Prospective data on 500 LRP cases were analysed with 80 excluded due to incomplete records. The operation was divided into multiple steps. Times for these steps were compared among 11 surgeons with different laparoscopic expertise (first-, second-, and third-generation surgeons in order of decreasing experience) and correlated to times for specific exercises on the pelvitrainer that simulated particular steps. Perioperative parameters were also evaluated among the three groups. RESULTS: Pelvitrainer times achieved by trainees (third-generation surgeons) did not differ significantly with times for corresponding steps of LRP. There was also no significant difference for total OR time between the second- and third-generation surgeons (205 and 207 min, respectively; p>0.05) although the time for the first-generation surgeons was faster than both (176 min). Short-term quality indicators for first, second, and third generations included transfusion rates (2.3%, 2.4%, and 2.6%, respectively), positive margin rates (20.3%, 21.5%, and 23.0%) and complications, which did not differ significantly among the generations although the first-generation surgeons had the lowest rates. CONCLUSIONS: A carefully designed training programme that incorporates both pelvitrainer and mentor-based operative training is essential for the effective and safe transfer of skills and knowledge required to learn LRP.

Adult↗
PubMed2006

Mhc class I genes of the cichlid fish Oreochromis niloticus.

In terms of number of species, perciform (perch-like) fishes are one of the most diversified groups of modern vertebrates. Within this group, the family Cichlidae is best known for its spectacular adaptive radiation in the great lakes of East Africa. The molecular tool kit used in the study of this radiation includes the major histocompatibility complex (Mhc) genes. To refine this tool, information about the organization of the Mhc regions is badly needed. In this study, the first step was taken toward providing such information for the Mhc class one regions of Oreochromis niloticus, a representative species of the tilapiine branch of the Cichlidae, for which good bacterial artificial chromosome library is available. Screening of the library with class I gene probes led to the identification and isolation of 31 class-I-positive clones. Sequencing of one of these clones and partial characterization of the remaining clones for the presence of class I exons resulted in the construction of two contigs representing the class I region of this species as well as identification of seven additional class-I-positive singleton clones. The O. niloticus genome was shown to contain at least 28 class I genes or gene fragments. The shorter of the two contigs was approximately 330 kb long and contained eight class I genes/gene fragments; the longer contig encompassed 1,200 kb of sequence and contained minimally 17 class I genes/gene fragments; three additional class I genes were found to be borne by a clone that might be part of the shorter contig.

Animals↗
PubMed2006

High-dose beta-blockers and tight heart rate control reduce myocardial ischemia and troponin T release in vascular surgery patients.

BACKGROUND: Adverse perioperative cardiac events occur frequently despite the use of beta (beta)-blockers. We examined whether higher doses of beta-blockers and tight heart rate control were associated with reduced perioperative myocardial ischemia and troponin T release and improved long-term outcome. METHODS AND RESULTS: In an observational cohort study, 272 vascular surgery patients were preoperatively screened for cardiac risk factors and beta-blocker dose. Beta-blocker dose was converted to a percentage of maximum recommended therapeutic dose. Heart rate and ischemic episodes were recorded by continuous 12-lead electrocardiography, starting 1 day before to 2 days after surgery. Serial troponin T levels were measured after surgery. All-cause mortality was noted during follow-up. Myocardial ischemia was detected in 85 of 272 (31%) patients and troponin T release in 44 of 272 (16.2%). Long-term mortality occurred in 66 of 272 (24.2%) patients. In multivariate analysis, higher beta-blocker doses (per 10% increase) were significantly associated with a lower incidence of myocardial ischemia (hazard ratio [HR], 0.62; 95% confidence interval [CI], 0.51 to 0.75), troponin T release (HR, 0.63; 95% CI, 0.49 to 0.80), and long-term mortality (HR, 0.86; 95% CI, 0.76 to 0.97). Higher heart rates during electrocardiographic monitoring (per 10-bpm increase) were significantly associated with an increased incidence of myocardial ischemia (HR, 2.49; 95% CI, 1.79 to 3.48), troponin T release (HR, 1.53; 95% CI, 1.16 to 2.03), and long-term mortality (HR, 1.42; 95% CI, 1.14 to 1.76). CONCLUSIONS: This study showed that higher doses of beta-blockers and tight heart rate control are associated with reduced perioperative myocardial ischemia and troponin T release and improved long-term outcome in vascular surgery patients.

Adrenergic beta-Antagonists↗
PubMed2006

Prognostic value of routine preoperative electrocardiography in patients undergoing noncardiac surgery.

Electrocardiography is commonly performed as part of preoperative cardiovascular risk assessment in patients undergoing noncardiac surgery. However, the prognostic value of such electrocardiography is still not clear. This study retrospectively studied 23,036 patients who underwent 28,457 surgical procedures at Erasmus Medical Center from 1991 to 2000. Patients were screened before surgery by type of surgery, cardiovascular risk factors (history of coronary heart disease, heart failure, diabetes mellitus, renal dysfunction, and stroke), and preoperative electrocardiography. Electrocardiographic (ECG) results showing atrial fibrillation, left or right bundle branch block, left ventricular hypertrophy, premature ventricular complexes, pacemaker rhythm, or Q-wave or ST-segment changes were classified as abnormal. Multivariate logistic regression was applied to evaluate the relation between ECG abnormalities and cardiovascular death. In-hospital cardiovascular death was observed in 199 of 28,457 patients (0.7%). Patients with abnormal ECG findings had a greater incidence of cardiovascular death than those with normal ECG results (1.8% vs 0.3%; adjusted odds ratio 4.5, 95% confidence interval 3.3 to 6.0). Adding ECG data to clinical risk factors and the type of surgery resulted in an improved C index for the prediction of cardiovascular death (0.79 vs 0.72). However, in patients who underwent low-risk or low- to intermediate-risk surgery, the absolute difference in the incidence of cardiovascular death between those with and without ECG abnormalities was only 0.5%. In conclusion, preoperative electrocardiography provides prognostic information in addition to clinical characteristics and the type of surgery. However, the usefulness of its routine use in lower risk surgery is questionable.

Aged↗
PubMed2006

Heterogeneous but conserved natural killer receptor gene complexes in four major orders of mammals.

The natural killer (NK) receptor gene complex (NKC) encodes a large number of C-type lectin-like receptors, which are expressed on NK and other immune-related cells. These receptors play an important role in regulating NK-cell cytolytic activity, protecting cells against virus infection and tumorigenesis. To understand the evolutionary history of the NKC, we characterized the C-type lectin-like NKC genes and their organization from four major orders of placental mammals, primates (human), rodents (mouse and rat), carnivores (dog), and artiodactyls (cattle) and then conducted phylogenetic analysis of these genes. The results indicate that the NKC of placental mammals is highly heterogeneous in terms of the gene content and rates of birth and death of different gene lineages, but the NKC is also remarkably conserved in its gene organization and persistence of orthologous gene lineages. Among the 28 identified NKC gene lineages, 4, KLRA1, KLRB1, CLEC2D, and CLEC4A/B/C, have expanded rapidly in rodents only. The high birth and death rate of these 4 gene families might be due to functional differentiation driven by positive selection. Identification of putative NKC sequences in opossum and chicken genomes implies that the expansion of the NKC gene families might have occurred before the radiation of placental mammals but after the divergence of birds from mammals.

Animals↗
PubMed2006

The grapes of incompatibility.

When two colonies of the tunicate Botryllus contact each other, they either fuse into a single colony or mount a destructive reaction, which keeps them apart. Which of the two reactions takes place is determined by a single, highly polymorphic fusion/histocompatibility (FuHC) locus. Recent communications report the cloning and characterization of the FuHC locus and suggest that its function may be to protect against parasitism by conspecific stem cells.

Animals↗
PubMed2006

Thermographic temperature measurement compared with pinprick and cold sensation in predicting the effectiveness of regional blocks.

We designed this study to evaluate the usefulness of thermographic temperature measurement with an infrared camera, compared with patient response to cold and pinprick, as a means of assessing the success or failure of axillary blockades. Axillary blocks were performed on 25 patients undergoing surgery on the hand or forearm using a nerve stimulator technique with mepivacaine 1.5%. Pinprick and cold sensation were assessed on the operative site at 5-min intervals for 30 min. A thermographic image of the operative limb was recorded at similar time intervals. Thermographic images of the unblocked limb were taken before block placement and at 30 min. Temperature values at the operative site and unblocked limb were calculated from the thermographic images. Results revealed that thermography had higher combined values for sensitivity, specificity, and positive and negative predictive values than both cold and pinprick at all time intervals, with statistically significant differences at 15 min (thermography versus cold, P = 0.006; thermography versus pinprick, P = 0.026) and 30 min (thermography versus cold, P = 0.038; thermography versus pinprick, P = 0.040). For thermography as a method of block assessment, an optimal time of 15 min after mepivacaine local anesthetic injection gives the highest combined values for predicting a successful block (P = 0.004). We conclude that thermography provides an early and objective assessment of the success and failure of axillary regional blockades.

Adult↗
PubMed2006

Peripheral flow index is a reliable and early indicator of regional block success.

We investigated the usefulness of peripheral flow index (PFI) measurement using a standard pulse oximetry digit probe for early prediction of successful regional blocks. Sixty-six patients scheduled for limb surgery underwent either axillary or sciatic block using a nerve stimulator technique with mepivacaine 1.5%. PFI, which is the ratio of the pulsatile versus the nonpulsatile component of the pulse oximetry signal, was recorded from 10 min before block insertion until 30 min afterwards. PFI recordings of the unblocked limb were similarly recorded. Pinprick and cold sensation were assessed at 5-min intervals until 30 min after blockade. An increase in PFI by a factor of 1.55 at 10 min after axillary block placement (P = 0.006), and 12 min after sciatic block placement (P = 0.001) was required to predict a successful block. The sensitivity and specificity of PFI was 100% for predicting axillary block outcomes at this time. Positive predictive value was 95% and negative predictive value was 93%. For sciatic blocks, sensitivity and specificity were 90% and 100%, respectively. The calculated positive predictive value at time 12 min for sciatic blocks was 94% and negative predictive value was 92%. At 15 min after block placement, cold and pinprick sensations had the same calculated values for sensitivity and specificity at 71% and 100%, respectively, for axillary blocks. For sciatic blocks, cold sensation had a sensitivity of 77% and a specificity of 100%, whereas pinprick had a sensitivity of just 20% with a specificity of 100%. We conclude that PFI provides a simple, early, and objective assessment of the success and failure of nerve blocks.

Adult↗
PubMed2006

Pain in neurosurgically treated patients: a prospective observational study.

OBJECT: This is the first observational study to compare perioperative pain character and intensity in patients undergoing different types of elective neurosurgical procedures. METHODS: A structured questionnaire was used to inquire about pain intensity, character, and management during the perioperative course, and the anticipated visual analogue scale (VAS) score in 649 patients during a 1-year period. The anticipated maximal postoperative VAS score was lower than the actual postoperative maximal VAS score and was independent of operation type and preoperative VAS score. Patients undergoing craniotomy experienced less pain than those undergoing spinal surgery. A majority of patients did not receive analgesic medication after surgery. Patients undergoing spinal surgery experienced higher preoperative VAS scores than those undergoing other neurosurgical treatments, with a shift from preoperative referred pain to postoperative local pain. After lumbar flavectomy, referred pain was greater than local pain. Patients with preoperative pain suffered significantly more postoperative pain than those without preoperative pain. In patients with postoperative surgery-related complications, VAS scores were higher than in those without complications. CONCLUSIONS: Neurosurgical procedures cause more pain than anticipated. Anticipated pain intensity is independent of the operation type and preoperative pain intensity. Postcraniotomy on-demand analgesic medication is appropriate, if the nurses on the ward react quickly. Otherwise, patient-controlled analgesia might be an option. Other neurosurgical procedures require scheduled analgesic therapies. Spinal surgery requires intensive preoperative pain treatment; a shift in pain character from preoperative referred pain to postoperative local pain is expected. Patients with referred pain after lumbar flavectomy are prone to the most intense pain. Patients with preoperative pain experience more postoperative pain than those without preoperative pain and require more intensive pain management. Increased postoperative VAS scores are associated with surgery-related complications.

Adolescent↗
PubMed2005

Organization, alternative splicing, polymorphism, and phylogenetic position of lamprey CD45 gene.

CD45 of jawed vertebrates is a receptor-type protein tyrosine phosphatase regulating lymphocyte development and activation. To shed light on the evolution of the CD45 gene, the organization of its orthologue in the lamprey, a jawless vertebrate, was determined. Compared to its mammalian and fugu counterparts, the lamprey gene was found to be lacking several exons in the segment encoding the extracellular part of the protein. In consequence, this part contains only one instead of the two or three fibronectin type III domains typical of the mammalian molecules. The lamprey transcripts of the CD45 gene occur in several variants originating by alternative splicing, including some not observed previously in other vertebrates. Most remarkable of these are splice variants generated by the use of intra-exonic splicing signals and thus lacking one half, one third, or two thirds of an exon and yet apparently translated in the correct reading frame. The lamprey gene contains polymorphic sites not only in the segment encoding the extracellular portion but also in the segment specifying the cytoplasmic part of the molecule. Polymorphism is generated by both mutations and recombination. Some of the alleles may have persisted long enough to represent transspecies polymorphism presumably maintained by positive selection. Phylogenetic analysis suggests that ancestors of the CD45 gene may have existed before the divergence of coelomate from pseudocoelomate metazoans.

Alternative Splicing↗
PubMed2005

Optimizing the prediction of perioperative mortality in vascular surgery by using a customized probability model.

BACKGROUND: Accurately assessing the probability of perioperative mortality can be useful in preoperative risk assessment and management. This study aimed to revise and customize the revised cardiac risk (Lee) index to estimate the probability of perioperative all-cause mortality in patients undergoing noncardiac vascular surgery. METHODS: We studied 2310 patients (mean age, 67.8 +/- 11.3 years; 1747 males) who underwent acute or elective major noncardiac vascular surgery between January 1, 1991, and December 31, 2000, at the Erasmus Medical Center, Rotterdam, the Netherlands. A total of 1537 patients were assigned for model development, in which the associations between predictor variables and mortality occurring within 30 days after surgery were identified to modify the Lee index, which was then evaluated in a validation cohort of 773 patients. RESULTS: The perioperative mortality rates were similar in the development (n = 103 [6.7%]) and validation (n = 50 [6.5%]) populations. The customized risk-prediction model for perioperative mortality identified type of vascular surgery, ischemic heart disease, congestive heart failure, previous stroke, hypertension, renal dysfunction, and chronic pulmonary disease as being associated with increased risk, whereas beta-blocker and statin use were associated with a lower risk of mortality. The performance of the customized index had excellent discriminative ability in both derivation and validation populations (concordance statistic, 0.88 and 0.85, respectively). CONCLUSIONS: The customized index provides more detailed information than the Lee index about the type of vascular procedure, clinical risk factors, and concomitant medication use. The customized probability model can be a useful tool to estimate the risk of perioperative all-cause mortality and facilitate subsequent treatment strategies.

Aged↗
PubMed2005

Origin and evolution of the chicken leukocyte receptor complex.

In mammals, the cell surface receptors encoded by the leukocyte receptor complex (LRC) regulate the activity of T lymphocytes and B lymphocytes, as well as that of natural killer cells, and thus provide protection against pathogens and parasites. The chicken genome encodes many Ig-like receptors that are homologous to the LRC receptors. The chicken Ig-like receptor (CHIR) genes are members of a large monophyletic gene family and are organized into genomic clusters, which are in conserved synteny with the mammalian LRC. One-third of CHIR genes encode polypeptide molecules that contain both activating and inhibitory motifs. These genes are present in different phylogenetic groups, suggesting that the primordial CHIR gene could have encoded both types of motifs in a single molecule. In contrast to the mammalian LRC genes, the CHIR genes with similar function (inhibition or activation) are evolutionarily closely related. We propose that, in addition to recombination, single nucleotide substitutions played an important role in the generation of receptors with different functions. Structural models and amino acid analyses of the CHIR proteins reveal the presence of different types of Ig-like domains in the same phylogenetic groups, as well as sharing of conserved residues and conserved changes of residues between different CHIR groups and between CHIRs and LRCs. Our data support the notion that the CHIR gene clusters are regions homologous to the mammalian LRC gene cluster and favor a model of evolution by repeated processes of birth and death (expansion-contraction) of the Ig-like receptor genes.

Animals↗
PubMed2005

Origin and evolution of the Ig-like domains present in mammalian leukocyte receptors: insights from chicken, frog, and fish homologues.

In mammals many natural killer (NK) cell receptors, encoded by the leukocyte receptor complex (LRC), regulate the cytotoxic activity of NK cells and provide protection against virus-infected and tumor cells. To investigate the origin of the Ig-like domains encoded by the LRC genes, a subset of C2-type Ig-like domain sequences was compiled from mammals, birds, amphibians, and fish. Phylogenetic analysis of these sequences generated seven monophyletic groups in mammals (MI, MII, and FcI, FcIIa, FcIIb, FcIII, FcIV), two in chicken (CI, CII), four in frog (FI-FIV), and five in zebrafish (ZI-ZV). The analysis of the major groups supported the following order of divergence: ZI [or a common ancestor of ZI and F (a cluster composed of the FcIII and FIII groups)], F, CII (or a common ancestor of CII and MII), MII, and MI-CI. The relationships of the remaining groups were unclear, since the phylogenetic positions of these groups were not supported by high bootstrap values. Two main conclusions can be drawn from this analysis. First, the two groups of mammalian LRC sequences must diverged before the separation of the avian and mammalian lineages. Second, the mammalian LRC sequences are most closely related to the Fc receptor sequences and these two groups diverged before the separation of birds and mammals.

Animals↗
PubMed2005

Perioperative cardiovascular mortality in noncardiac surgery: validation of the Lee cardiac risk index.

PURPOSE: The Lee risk index was developed to predict major cardiac complications in noncardiac surgery. We retrospectively evaluated its ability to predict cardiovascular death in the large cohort of patients who recently underwent noncardiac surgery in our institution. METHODS: The administrative database of the Erasmus MC, Rotterdam, The Netherlands, contains information on 108 593 noncardiac surgical procedures performed from 1991 to 2000. The Lee index assigns 1 point to each of the following characteristics: high-risk surgery, ischemic heart disease, heart failure, cerebrovascular disease, renal insufficiency, and diabetes mellitus. We retrospectively used available information in our database to adapt the Lee index calculated the adapted index for each procedure, and analyzed its relation to cardiovascular death. RESULTS: A total of 1877 patients (1.7%) died perioperatively, including 543 (0.5%) classified as cardiovascular death. The cardiovascular death rates were 0.3% (255/75 352) for Lee Class 1, 0.7% (196/28 892) for Class 2, 1.7% (57/3380) for Class 3, and 3.6% (35/969) for Class 4. The corresponding odds ratios were 1 (reference), 2.0, 5.1, and 11.0, with no overlap for the 95% confidence interval of each class. The C statistic for the prediction of cardiovascular mortality using the Lee index was 0.63. If age and more detailed information regarding the type of surgery was retrospectively added, the C statistic in this exploratory analysis improved to 0.85. CONCLUSION: The adapted Lee index was predictive of cardiovascular mortality in our administrative database, but its simple classification of surgical procedures as high-risk versus not high-risk seems suboptimal. Nevertheless, if the goal is to compare outcomes across hospitals or regions using administrative data, the use of the adapted Lee index, as augmented by age and more detailed classification of type of surgery, is a promising option worthy of prospective testing.

Adult↗