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N Roewer

Publications and source records attributed to N Roewer.

At least 19 recordsLinked to original sources
PubMed2001

The influence of a dominating centre on a quantitative systematic review of granisetron for preventing postoperative nausea and vomiting.

BACKGROUND: We performed a meta-analysis on granisetron in the prevention of postoperative nausea and vomiting (PONV) and further investigated whether total results and the dose-response characteristics may be significantly affected by a single centre. METHODS: Systematically searched randomised controlled trials (RCT) using granisetron for the prevention of PONV after general anaesthesia were included in the analysis. The pooled relative risks (RR) and numbers needed to treat (NNT) with their corresponding 95%-confidence intervals (CI) were calculated. For all centres, one dominating centre and other centres pooled, comparisons were performed according to all doses, low dose ( 20 microg/kg) granisetron. RESULTS: A total of 27 RCT with 2938 patients were included in the analysis. RR (CI) to suffer from PONV with granisetron when all comparisons were considered was 0.46 (0.39-0.54), 0.7 (0.6-0.81) and 0.34 (0.28-0.41) for all doses, low and high dose, respectively. RR of the dominating centre (1867 patients) were significantly better compared to the remaining centres (1071 patients), with 0.41 (0.34-0.49) and 0.60 (0.49-0.73), respectively. In the dominating centre low dose granisetron was ineffective with a RR of 0.84 (0.68-1.04), while high dose granisetron led to a strong decrease with a RR of 0.30 (0.26-0.36). In contrast, the RR of other centres pooled for low and high dose granisetron were comparable with 0.62 (0.49-0.79) and 0.56 (0.42-0.75), respectively. CONCLUSIONS: Overall results and dose-response characteristics of meta-analyses may be significantly altered by one dominating centre. Further, if data of a dominating centre do not appear to be valid for other centres, it may seem advisable to either exclude them from the analysis or to perform sub-group analyses so that results without the data from the dominating centre are available.

Antiemetics↗
PubMed2001

The detection of interatrial flow patency in awake and anesthetized patients: a comparative study using transnasal transesophageal echocardiography.

UNLABELLED: The Valsalva maneuver in the awake patient and the ventilation maneuver in the tracheally intubated anesthetized patient are two provocation methods to detect a patent foramen ovale (PFO) by means of contrast transesophageal echocardiography. In 60 patients undergoing posterior fossa surgery, a contrast agent was administered via a peripheral vein during a Valsalva maneuver immediately before anesthesia induction, followed by central venous administration during a ventilation maneuver in the same patients when anesthetized and endotracheally intubated. We evaluated both maneuvers with a 32-element monoplane transnasal transesophageal echocardiography probe to trace the atrial flow of the contrast agent in a 90 degrees bicaval view. A maneuver was rated positive when more than four bubbles appeared in the left atrium during the first three cardiac cycles after intrathoracic pressure release. The right atrial cross-sectional area before pressure release, and the peak septal excursion during atrial contrast opacification, were measured. McNemar's test was used to assess a paired dichotomous response on the two maneuvers for a significant difference. In 56 patients, the ventilation maneuver was significantly (P < 0.037) more often positive for PFO (n = 14) than the Valsalva maneuver (n = 7). Although there was no difference in the methods regarding the peak septal excursion, the mean right atrial area before pressure release was significantly smaller during the ventilation maneuver than during the Valsalva maneuver (11.2 +/- 3.1 cm(2) vs 14.4 +/- 3.3 cm(2), n = 42, P < 0.05). In the patients with a positive ventilation, but a negative Valsalva maneuver, the discrepancy was even larger (10.9 +/- 4.4 cm(2) vs 16.3 +/- 4.2 cm(2), n = 7, P < 0.001). We conclude that the ventilation maneuver is superior to the Valsalva maneuver in detecting PFO. Our data suggest that a peak pressure of 30 cm H(2)O during the ventilation maneuver achieves a more pronounced reduction in right atrial load and allows right atrial pressure to exceed left atrial pressure when intrathoracic pressure is released. IMPLICATIONS: A controlled ventilation maneuver in anesthetized patients immediately before posterior fossa surgery may be superior to the preoperative Valsalva maneuver in detecting a patent foramen ovale by contrast transesophageal echocardiography. This approach identifies patients at high risk for paradoxic embolism, but it is not practical for preoperative identification of patients who might benefit from patent foramen ovale closure before surgery.

Anesthesia↗
PubMed2001

An increased body mass index is no risk factor for postoperative nausea and vomiting. A systematic review and results of original data.

BACKGROUND: An increased Body Mass Index (BMI) is almost always mentioned as a fundamental risk factor for postoperative nausea (PN), vomiting (PV) or both (PONV). However, multivariate analyses were unable to detect any correlation. Therefore, we asked whether an increased BMI is really a risk factor for PONV. METHODS: For the systematic review, a search of electronic databases and a detailed manual search of reviews were carried out. For the analysis of the original data, 587 adult patients from a randomised controlled antiemetic trial (RCT) who underwent general anaesthesia were allocated to four weight groups: Underweight (BMI < 20), Normal Weight (BMI 20-25), Overweight (BMI 25-30) and Obesity (BMI > or = 30). RESULTS: Four publications with original data were found. Two described a positive relationship, although not clearly supported by the data. Despite this, most narrative reviews claimed a positive correlation between obesity and PONV by quoting again narrative reviews or misquoting originals. In the RCT, the calculated underlying risk profile for PONV was comparable between all groups. Incidences (95% confidence intervals) of PONV were 45.8% (34.0; 57.6), 41.7 (36.5; 46.9), 47.8 (38.4; 57.1) and 44.1 (31.0; 57.1), for the groups Underweight, Normal Weight, Overweight and Obesity, respectively (P=0.69). The incidences of PN and PV also did not differ with P=0.76 and P=0.36, respectively. CONCLUSION: Systematic search of the literature provides no evidence for a positive relationship. Furthermore, our data confirm that an increased BMI is not a risk factor for PONV. This negative finding is important as focussing on the relevant risk factors is needed to allow for an objective risk assessment of PONV.

Body Mass Index↗
PubMed2000

[Risk factors for nausea and vomiting after general anesthesia: fictions and facts].

Numerous factors have been claimed to influence postoperative nausea and vomiting (PONV). A critical review of the literature reveals, that strong evidence based on original double-blind, randomized, controlled trials or their meta-analyses is only available for very few risk factors. For most other factors, although mentioned in narrative reviews, there is insufficient evidence. Sufficient evidence on original data or meta-analyses is present for female gender, a history of PONV or motion sickness, non-smoking-status, young age, volatile anaesthetics, nitrous oxide and postoperative opioids. Factors with conflicting results are the menstrual cycle, hypnotics for induction, mask ventilation and nasogastric tube, the experience of the anaesthetist, muscle relaxants and their antagonists and laparoscopic procedures. Insufficient evidence is present for the other types of operation, psychological factors including anxiety and pain. No evidence due to lack of data applies to postoperative movement, hemodynamic stability, hypercarbia and acid-base-shifts. For adipositas++ there is not only a lack of evidence for an effect but evidence for a lack of effect based on several multivariate analyses. In conclusion, we have developed the following simplified view: PONV is mainly caused by opioids and volatile anaesthetics when applied to susceptible patients (females, non-smoker, positive history of previous sickness).

Anesthesia, General↗
PubMed2000

The impact of 4-chloro-m-cresol in heparin formulas on malignant hyperthermia: in vitro and in vivo.

BACKGROUND: The preservative 4-chloro-m-cresol (4CmC) is a specific activator of sarcoplasmic Ca2- release and induces contractures in skeletal muscles of malignant hyperthermia susceptible (MHS) patients in vitro. Clinical formulas of heparin contain 4CmC. We studied whether (a) these heparin formulas induce contractures in isolated MHS and normal (MHN) human skeletal muscles and whether (b) significant serum levels of 4CmC are reached after heparinization in cardiopulmonary bypass patients. METHODS: (a) In vitro, muscle bundles of 16 MHS and 22 MHN patients were exposed to the heparin formula Liquemin (containing 4CmC 0.08 mg/500 IU), to chlorocresol and to preservative-free heparin in the in vitro contracture test. (b) In vivo, serum 4CmC levels of 12 patients receiving Liquemin 500 IU/ kg before cardiopulmonary bypass were determined at 1, 5 and 60 min by high-pressure liquid chromatography. RESULTS: (a) For Liquemin and 4CmC, significant contractures were measured with MHS muscles compared to MHN muscles at 61.4 microM 4CmC. (b) In control sera, the detection threshold for 4CmC was 4 microM. Concentrations of 4CmC in all patients' serum samples were below this threshold. CONCLUSION: Heparin formulas, containing 4CmC, induce dose-dependent contractures in vitro in MHS human skeletal muscle at about 60 microM 4CmC. However, in vivo, 4CmC serum concentrations with therapeutic heparinization are less than 1/15 of the in vitro concentration. The lipophilicity of 4CmC with a high volume of distribution may account for these findings. MHS patients seem not to be at risk from clinical heparin formulas containing chlorocresol.

Adult↗
PubMed2000

Intracavitary contrast intensity after transpulmonary transmission of a second-generation contrast agent at normal and reduced myocardial contractility.

In this closed-chest preparation in 10 anesthetized pigs, we determined the effects of left ventricular (LV) contractility changes on the echocardiographic contrast intensity variation of a second-generation contrast agent within the LV cavity. The peak positive rate of change in LV pressure (dP/dt(max)), as an index of the isovolumetric phase, was gradually reduced by administration of halothane and propranolol, and the velocity of circumferential fiber shortening (Vcfs) was referenced as an index for the LV ejection phase. Contrast intensity-time curves of the LV cavity were obtained after transpulmonary transmission of the contrast agent. An off-line densitometric method was performed to determine peak maximum and minimum intensities (I(max), I(min)) and their difference (I(amp)). Compared with baseline values, at reductions in dP/dt(max) of 50% and 75%, the contrast intensity parameters I(max), I(min), and I(amp) were decreased by 23% +/- 6% and 44% +/- 5%, 24% +/- 5% and 44% +/- 3%, and 31% +/- 6% and 45% +/- 3%, respectively (P <.05). Significant correlations were observed between I(amp) and dp/dt(max) (r = 0.82, P <.003, n = 30) and their changes (r = 0.59, P <.03, n = 20), but correlations between contrast indexes and Vcfs were only moderate. The sensitivity of I(amp) to indicate changes in dP/dt(max) and Vcfs was 0.95 and 0.83, respectively. The cyclic variation of LV intracavitary contrast intensity reflects the isovolumetric contraction phase better than the ejection phase. The results suggest that measurements of cyclic intensity changes may contribute to the assessment of myocardial contractility changes. Underlying biophysical mechanisms and load dependency of this phenomenon require further investigation.

Animals↗
PubMed2000

Preliminary report: analgesia with Remifentanil for complicated eye muscle surgery.

The authors report a new anesthetic technique that is especially suitable for the surgery of complicated disorders of ocular motility. Analgesia is achieved by an intravenous dose of Remifentanil, an opioid that is normally used together with propophol as a form of total intravenous anesthesia (TIVA) for general anesthesia. The advantage of Remifentanil is a rapid increase (1-2 min.) and decrease (3-4 min.) of the effect. Eye muscle surgery can then be performed on a patient who is free of pain and slightly sedated. After the planned eye muscle surgery, while the patient is still under anesthesia, the muscle sutures are tied provisionally. Afterwards, the squint angle can be measured with a cover test and the patient is questioned about the presence of diplopia. If the position of the eye is not satisfactory, the knots can be loosened and the muscle can be fixated in another position.

Analgesia↗
PubMed2000

Propofol decreases stimulated dopamine release in the rat nucleus accumbens by a mechanism independent of dopamine D2, GABAA and NMDA receptors.

Although propofol (2,6-di-isopropylphenol) is a popular i.v. general anaesthetic, it has been suggested to have abuse potential. As many drugs of abuse act preferentially via release of dopamine in the limbic system, we investigated the action of propofol on stimulated dopamine release in the rat nucleus accumbens. Nucleus accumbens slices were superfused (1.6 ml min-1) with artificial cerebrospinal fluid at 32 degrees C. Dopamine release was evoked by electrical stimulation (10 pulses, 0.1 ms, 10 mA, 10 Hz, every 10 min) and monitored by fast cyclic voltammetry. Propofol 100 mumol litre-1 reduced stimulated dopamine release over the 2 h after administration, relative to intralipid controls, to mean 30 (SEM 2)% (P < 0.01). The dopamine D2 receptor antagonist metoclopramide 0.3 mumol litre-1 increased dopamine release but did not block the effect of propofol (38 (3)%). The selective GABAA antagonist bicuculline 24 mumol litre-1 also failed to antagonize the action of propofol (45 (3)%). The NMDA receptor antagonist dextromethorphan 10 mumol litre-1 decreased dopamine release to 57 (6)% (P < 0.01) but failed to block the inhibitory effect of propofol (46 (6)%). Although propofol has been reported to bind to D2, GABAA and NMDA receptors, failure of metoclopramide and bicuculline to block its effects suggests that an agonist action at D2 or GABAA receptors does not mediate the effects of propofol on dopamine release in the rat nucleus accumbens. The lack of effect of dextromethorphan makes an NMDA receptor antagonist action unlikely.

Anesthetics, Intravenous↗
PubMed1999

[Are morphologic changes in skeletal muscles of patients with malignant hyperthermia diagnostically useful?].

Malignant Hyperthermia (MH) represents a functional myopathy triggered by volatile anesthetics and depolarizing muscle relaxants, and leading to metabolic disturbances of intracellular Calcium homeostasis. Central-Core-like-structures (CCLS) were recently described as central defects in enzyme-histochemical stains and well correlated to the autosomal-dominant MH-predisposition. We studied the correlation of a MH-predisposition with specific myopathological signs. Skeletal muscles of suspected MH-individuals were histochemically stained by SDH-, NADH-, COX-, Gomori-Trichrome-, ATPase-, Acid Phosphatase-, Oil-red O- und PAS-stain und evaluated without knowing MH-diagnosis by the in-vitro-contracture test. Out of 118 patients (30% MHS ["susceptible"], 63% MHN [normal], 7% MHE ["equivocal"]) 19% revealed pathological findings corresponding to CCLS. 45% of these findings were associated with MHS/MHE. With HE-staining internal nuclei were not specific, but increased with the probability of MHS/MHE from 24% to 80%. Central Cores were correlated in 100% with MHS/MHE (4 out of 118 patients). CCLS were found with about similar frequency in skeletal muscle of MHS/MHE and MHN individuals. Internal nuclei were, however, not specifically, associated with MHS. In contrast, Central Cores correlated significantly with MHS/MHE diagnosis. In conclusion, histopathological findings in skeletal muscle seem to be a reliable marker for MH-predisposition only with Central Cores.

Adolescent↗
PubMed1999

Transnasal transesophageal echocardiography: a modified application mode for cardiac examination in ventilated patients.

UNLABELLED: In 42 endotracheally intubated patients, we examined the utility of a miniaturized monoplane probe for transnasal transesophageal echocardiography (TEE). Transnasal TEE was prospectively evaluated in 26 deeply and 16 mildly sedated patients receiving topical anesthesia with lidocaine jelly 2%. The patients with deep sedation were additionally examined with transoral monoplane and multiplane TEE. Transnasal esophageal insertion of the TEE probe was successfully performed in 90% of patients. Endotracheal malpositioning was corrected in two patients. Nasal bleeding required treatment in another patient. Topical anesthesia was adequate in 82% of mildly sedated patients. Left ventricular short- and four-chamber long-axis views of good quality were obtained with transnasal (transoral) monoplane TEE in 76% (81%) and 92% (96%) of patients (differences not significant). Compared with conventional multiplane TEE, transnasal monoplane TEE missed diagnoses in 19% of patients. The relative error (mean +/- SEM) of quantification with transnasal TEE was <9% +/- 2% for ventricular diameters and <7% +/- 2% for cross-sectional area measurements, with a bias of 0.5 +/- 3.8 cm2 and 0.1 +/- 2.4 cm2 (mean +/- 2 SD) for left ventricular end-diastolic and end-systolic short-axis areas. The relative error in measuring intracardiac flow velocities was >40%, but systolic to diastolic peak velocity ratios at the valvular site were determined with an error <4% +/- 3%. Transnasal monoplane TEE can be performed even in mildly sedated patients with an endotracheal tube without further need for analgesia or sedation. The technique is as useful as conventional transoral TEE to image standard tomographic planes for quantification, but it is less suited for comprehensive echocardiographic diagnosing. IMPLICATIONS: Transnasal insertion of a miniaturized monoplane transesophageal echocardiography (TEE) probe was studied in endotracheally intubated patients. Nasal passage was well tolerated even by patients with only mild sedation. Imaging quality was similar to conventional transoral monoplane TEE with larger transducers, but technical restraints cause a deficit in complete cardiac diagnosing obtained with multiplane TEE.

Anatomy, Cross-Sectional↗
PubMed1999

A simplified risk score for predicting postoperative nausea and vomiting: conclusions from cross-validations between two centers.

BACKGROUND: Recently, two centers have independently developed a risk score for predicting postoperative nausea and vomiting (PONV). This study investigated (1) whether risk scores are valid across centers and (2) whether risk scores based on logistic regression coefficients can be simplified without loss of discriminating power. METHODS: Adult patients from two centers (Oulu, Finland: n = 520, and Wuerzburg, Germany: n = 2202) received inhalational anesthesia (without antiemetic prophylaxis) for various types of surgery. PONV was defined as nausea or vomiting within 24 h of surgery. Risk scores to estimate the probability of PONV were obtained by fitting logistic regression models. Simplified risk scores were constructed based on the number of risk factors that were found significant in the logistic regression analyses. Original and simplified scores were cross-validated. A combined data set was created to estimate a potential center effect and to construct a final risk score. The discriminating power of each score was assessed using the area under the receiver operating characteristic curves. RESULTS: Risk scores derived from one center were able to predict PONV from the other center (area under the curve = 0.65-0.75). Simplification did not essentially weaken the discriminating power (area under the curve = 0.63-0.73). No center effect could be detected in a combined data set (odds ratio = 1.06, 95% confidence interval = 0.71-1.59). The final score consisted of four predictors: female gender, history of motion sickness (MS) or PONV, nonsmoking, and the use of postoperative opioids. If none, one, two, three, or four of these risk factors were present, the incidences of PONV were 10%, 21%, 39%, 61% and 79%. CONCLUSIONS: The risk scores derived from one center proved valid in the other and could be simplified without significant loss of discriminating power. Therefore, it appears that this risk score has broad applicability in predicting PONV in adult patients undergoing inhalational anesthesia for various types of surgery. For patients with at least two out of these four identified predictors a prophylactic antiemetic strategy should be considered.

Adult↗