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Biomedical subjects

N Roewer

Publications and source records attributed to N Roewer.

At least 91 records · Page 5Linked to original sources
PubMed1997

The relation between left ventricular wall stress shortening and preload changes in ventilated patients.

The relation between left ventricular end-systolic wall stress (ESWS) and the velocity of circumferential fibre shortening (Vcfs) was examined in four non-random groups with 12 patients each. In group A, preload was increased by the administration of hydroxyethylstarch 30 mL min-1. In group B, preload was reduced by administering nitroglycerine 4.0 +/- 0.8 mg h-1. A change in pulmonary capillary wedge pressure by 3 mmHg was taken to be the end point for preload manipulation. To assess a change in the relation between ESWS and Vcfs, patients in group C received adrenaline at an infusion rate of 4 g min-1. Patients in group D served as the controls. Geometric variables of ESWS and Vcfs were determined by transoesophageal echocardiography. A linear model was used to assess the relation between ESWS and Vcfs within each group by regression analysis, and analysis of covariance performed to detect significance of intragroup and intergroup differences (P < 0.005). No significant changes were found during preload intervention. With adrenaline, Vcfs increased significantly for a given ESWS. It is concluded that the relation between ESWS and Vcfs, in a multiple patient setting, is independent of modest preload changes and may have the potential to indicate inotropic effects.

Adult↗
PubMed1997

[Echocardiography values in the halothane uptake phase--measurement by acoustic quantification and manual evaluation].

In 35 ASA group I and II patients we investigated the influence of haemodynamic changes induced by increasing concentrations of halothane (from 0.0 to 0.6% halothane in 70% N20) on parameters of transesophageal echocardiography (TEE). Measurements by TEE were taken in manual and automatic boundary detection mode. In manual mode the left ventricular endsystolic area (ESA) increased significantly (+16.3%) and the fractional area change (FAC) decreased significantly (-14.9%). There was no significant change of left ventricular end diastolic area (EDA). In the automatic mode there was a significant increase of ESA and EDA (+13.8%; +6.0%) and a significant decrease of FAC (-10.9%). Peak ejection rate (PER) and peak filling rate (PFR) which were also assessed in automated mode decreased significantly (-10.0%; -5.7%) under halothane. No change occurred with manually determined left ventricular endsystolic wall stress (LVEWS). The endsystolic quotient decreased significantly both in manual and automated mode during halothane (-28.3%; -29.9%). No significant difference existed between TEE measurements under apnoea versus under controlled ventilation (except for EDA in automated mode). We conclude that there is no need for apnoea conditions for TEE measurements. In conclusion, TEE proves a useful monitoring system in anesthesia which enables the investigator to assess the negative inotropic effect of halothane. Problems in its practical usage are due to the wide variation of TEE measurements.

Adult↗
PubMed1997

[Asymmetric hypertrophic cardiomyopathy in a septic patient--intraoperative preliminary diagnosis with transesophageal echocardiography].

Cardiac dysrhythmias in septic patients often reflect hypovolaemia, hypokalaemia or endocarditis as cardiac manifestation of the infection, but may be indicative for underlying cardiac pathology previously undiagnosed. We report on the case of a patient with severe peritonitis, on whom transoesophageal echocardiography (TEE) had been performed intraoperatively due to progressive circulatory instability. TEE revealed first diagnosis of asymmetric hypertrophic cardiomyopathy, which complicated the features of septic syndrome. Further perioperative treatment to support the circulation was successfully adjusted on the grounds of this diagnosis.

Abdominal Abscess↗
PubMed1997

Continuous cardiac output monitoring during adult liver transplantation: thermal filament technique versus bolus thermodilution.

UNLABELLED: Continuous thermodilution (CT) using a pulmonary artery (PA) catheter with a thermal filament has the potential for intraoperative on-line monitoring of cardiac output. Liver transplantation frequently requires rapid fluid administration and often includes the use of an extracorporeal veno-venous bypass. To assess the agreement between CT and bolus thermodilution (BT) in such a setting, we conducted a prospective intraoperative study in 14 liver transplant patients. Throughout the operation, CT cardiac output was recorded and paired with BT measurements taken every 30 min and whenever indicated for clinical reason. Corresponding data were assigned to acquisition periods when patients were on or off veno-venous bypass (flow rate 2.5 +/- 0.2 L/min) and were discriminated by the various range of intravenous infusion rates (< 150 mL/h, 150-1000 mL/h, 1000-2000 mL/h, and 2000-4000 mL/h) and the magnitude of cardiac output (< or = 7.5 L/min, 7.5-10.0 L/min, > 10.0 L/min). A total of 270 data pairs was obtained and examined by analysis of agreement (mean difference +/- SD), variance, error, and weighted regression. Trend analysis was performed for significant CT and BT cardiac output changes, defined as changes greater than 15%. Agreement of both methods was best at peripheral intravenous fluid infusion rates < or = 1000 mL/h and BT cardiac output > 10 L/min (0.0 +/- 0.6 L/min) and was unaffected by veno-venous bypass. Discrepancy was most evident at intravenous fluid infusion rates > 2000 mL/h and BT cardiac output < or = 7.5 L/min (2.1 +/- 1.7 L/min). Correlation of CT and BT cardiac output was excellent (r = 0.95, P < 0.001) for combined data from all patients. Changes in CT cardiac output > 15% (n = 116) correctly indicated the direction in 93% of BT cardiac output changes and were 74% sensitive and 75% specific for significant BT cardiac output changes. The thermal filament technique enhances the usefulness of PA catheterization during liver transplantation but reflects BT cardiac output with clinically acceptable error only at low peripheral intravenous fluid infusion rates. IMPLICATIONS: Cardiac output determines organ perfusion. In clinical practice, it is measured by intermittent thermodilution using right heart catheterization. This intraoperative study compared the intermittent method with a technique based on continuous thermodilution. The new technique provides logistical advantages and challenges the accuracy of the intermittent method during liver transplantation.

Adult↗
PubMed1996

Fulminant malignant hyperthermia associated with ketoacidotic diabetic coma.

Malignant hyperthermia (MH) in humans is usually triggered by volatile anaesthetics and depolarizing muscle relaxants. However, other factors or drugs (e.g. cresol) are thought to induce MH. We report a case of fulminant MH associated with a ketoacidotic diabetic coma. After therapy for diabetic coma with insulin (containing the preservative cresol) and electrolyte solutions was started, the patient complained of increasing myalgia, developed a high fever and respiratory and metabolic acidosis and lost consciousness. MH was treated immediately with dantrolene; the patient recovered within 14 days. Five months later the patient was diagnosed as MH-susceptible by the in vitro caffeine and halothane contracture test. This case supports the assessment that MH and diabetes are associated diseases and that cresol could possibly trigger MH. Furthermore, therapy with dantrolene has been demonstrated to be beneficial in the treatment of MH associated with diabetic coma.

Adult↗
PubMed1996

[Are monamine oxidase inhibitors in disposition to malignant hyperthermia contraindicated? Discussion based on a case report].

We report on a young patient with a positive family history for malignant hyperthermia (MH), who was diagnosed as susceptible to MH in our malignant hyperthermia laboratory by the in vitro-contracture test. Prior to the investigation of MH-susceptibility, the patient had been on medication with moclobemide, a monoamine oxidase (MAO) inhibitor, over a period of 13 months for treatment of a hyperactivity disorder. During the therapy with moclobemide no signs of relevant side effects were observed. However, some authors regard MAO-inhibitors as MH-triggering agents. The risk of MH-patients due to the therapy with MAO-inhibitors and the association between MH and the neuroleptic malignant syndrome is discussed in this case report.

Anesthetics, Inhalation↗
PubMed1996

On-line estimation of left ventricular stroke volume using transoesophageal echocardiography and acoustic quantification.

We have examined the usefulness of transoesophageal echocardiography (TOE) and automated endocardium detection for on-line calculation of left ventricular stroke volume. In 12 of 15 patients undergoing abdominal surgery, stroke volume was derived continuously from the multiple discs (MD) and area-length (AL) methods and compared with stroke volume calculated by thermodilution. In 10 patients (80%), more than three manipulations of the ultrasound transducer were required before measurements. Linear regression analysis of automated TOE methods and thermodilution revealed weak correlations (r < 0.75) for stroke volume (114 matched pairs) and its changes (105 matched pairs). Correlation of percentage changes in stroke volume calculated by thermodilution with those derived from MD (r = 0.85) and AL (r = 0.79) was better. Changes in MD (AL) derived stroke volume by more than 20% identified changes in thermodilution-derived stroke volume greater than 20% (n = 57) with a sensitivity of 74% (70%) and a specificity of 82% (79%). Signal instability, lack of accuracy and only a moderate trend capability currently limit the intraoperative usefulness of automated TOE techniques for continuous estimation of stroke volume from a single long-axis plane.

Abdomen↗
PubMed1996

In vitro diagnosis of malignant hyperthermia susceptibility with ryanodine-induced contractures in human skeletal muscles.

The in vitro contracture test with ryanodine is a new method to distinguish malignant hyperthermia (MH) susceptible (MHS) from normal (MHN) patients. The purpose of our investigation was to determine whether smaller concentrations of ryanodine than those used previously may result in a better differentiation. We performed a ryanodine contracture test (RCT) using concentrations of 1 and 2 microM in muscle specimens of 41 MHS, 58 MHN, and 19 MH-equivocal (MHE) patients. Nine patients were excluded from the study due to neuromuscular diseases. All contracture levels (i.e., start of contractures, contractures of 0.2 g and 1.0 g) were attained significantly earlier in MHS than in MHN muscles at both concentrations of ryanodine. Using a ryanodine concentration of 2 microM, all contracture levels were reached significantly faster than with 1 microM. There was no overlap in the range of times between groups at all contracture levels with ryanodine 1 and 2 microM. The median threshold times for all MHE patients were always between those of MHS and MHN. Defining arbitrarily threshold times for MHS and MHN, an assignment of MHE patients to either MHS or MHN using 1 or 2 microM ryanodine was possible in most cases. Ryanodine administration at a concentration of 1 microM led to a better distinction of MHS from MHN patients than 2 microM. The RCT with ryanodine 1 microM should therefore be added to the current diagnostic methods.

Adolescent↗
PubMed1996

Effects of the serotonin2 receptor agonist DOI on skeletal muscle specimens from malignant hyperthermia-susceptible patients.

BACKGROUND: Administration of serotonin2 (5-HT2) receptor agonists in pigs triggers malignant hyperthermia (MH) and psychotic-like behavior. Both can be reduced by 5-HT2 receptor antagonists. Furthermore, an increase in the plasma concentration of 5-HT has been found during onset of halothane-induced MH in pigs. Therefore, in this study, the in vitro effects of the 5-HT2 receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) were investigated in muscle specimens from MH-susceptible (MHS) and -negative (MHN) patients. METHODS: After MH classification using the caffeine-halothane contracture test (CHCT), surplus muscle specimens from 23 MHS and 17 MHN patients were used to examine the effects of DOI. In the first study, DOI was added to the bath in a concentration of 0.02 mM. In a second experiment, muscles were preincubated for 60 min with 0.02 mM DOI, and subsequently, halothane was added incrementally to the organ bath (0.11-0.22-0.44 mM) for 15 min according to the CHCT protocol. The in vitro effects of DOI on contracture development and muscle twitch were measured for 120 min in both investigations. RESULTS: Muscle specimens form all patients developed contractures after administration of DOI, characterized by a significantly earlier development of contracture in MHS (16.8 +/- 1.7 min) than in MHN (66.3 +/- 5.8 min) muscles (P < 0.05). There was no overlap between the groups in the range of times. The onset of contracture development after DOI was prolonged by halothane in specimens from MHN patients (89.7 +/- 5.6 min) but not MHS patients. Preincubation with DOI increased the halothane-induced contractures in specimens from MHS patients compared to the results of the CHCT. The contracture development in specimens from MHS patients was larger than from MHN patients. At the end of the experiment, contractures had reached a maximum of 12.9 +/- 1.1 mN in specimens from MHS and 5.3 +/- 0.6 mN in MHN patients (P < 0.05). The additional administration of halothane led to significantly increased contractures in specimens from MHS individuals (15.9 +/- 0.9 mN) at 120 min. However, the contracture development decreased significantly to 3.1 +/- 0.4 mN in MHN muscles. Muscle twitch after DOI administration was reduced significantly in specimens from MHS and MHN patients. CONCLUSIONS: A functional or structural altered serotonin system might be involved in the development of MH in humans.

Adolescent↗
PubMed1995

C1840-T mutation in the human skeletal muscle ryanodine receptor gene: frequency in northern German families susceptible to malignant hyperthermia and the relationship to in vitro contracture response.

In swine, a point mutation in the ryanodine receptor gene can account for all cases of malignant hyperthermia (MH). The frequency of a corresponding mutation in humans (C1840-T) and its relationship to the in vitro contracture profile is unknown. We screened 192 patients from 28 unrelated northern German families for the C1840-T mutation in the human ryanodine receptor gene and tested for MH susceptibility using the in vitro contracture test (IVCT) according to the European MH Protocol. In our patients 106 revealed MH susceptible (MHS), 56 MH nonsusceptible and 30 MH equivocal status following IVCT. In each family one or two individuals had developed clinical signs of MH or a MH crisis. All of these patients were classified MHS. The C1840-T mutation was found in 2 of 28 families (7.1%). All eight individuals of the two families characterized by this mutation revealed MHS status following IVCT. The thresholds for halothane- and caffeine-induced contractures as well as the contracture profiles following cumulative (0.4-10.0 mumol/l every 3 min) and bolus (10 mumol/l) administration of ryanodine were found to be similar in MHS patients with and without the C1840-T mutation. In conclusion, the C1840-T mutation in the human ryanodine receptor gene is a rare abnormality in MHS families. Similar contracture profiles in the presence and absence of this mutation might imply no major functional role with respect to the contracture response. At present, molecular genetic analysis cannot replace IVCT to discover MH susceptibility in humans.

Adolescent↗
PubMed1995

[Estimation of acute left ventricular afterload alterations. Transesophageal echocardiography in artificially respirated patients].

UNLABELLED: Left ventricular afterload is most accurately represented by left ventricular end-systolic wall stress, but in clinical practice is commonly estimated by the systemic vascular resistance (SVR). End-systolic wall stress can be derived from M-mode and two-dimensional (2D) echocardiograms in combination with systolic arterial pressure (SAP). We tested transoesophageal echocardiography for the assessment of acute left ventricular afterload alterations in ventilated patients requiring cardiovascular support with noradrenaline or nitroglycerine. METHOD. With approval from the local ethics committee, we studied afterload alterations in 11 hypotensive patients who were treated by increasing the dosage of i.v. noradrenaline by 2-5 micrograms/min in order to raise mean arterial pressure (MAP) by 20 mmHg. In another 10 patients with MAP over 95 mmHg, nitroglycerine was raised from 2 to 4 mg/h, aiming at a 20 mmHg MAP reduction. MAP and SAP were monitored via a radial artery cannula, cardiac output (CO) was measured with the thermodilution technique using a Swan-Ganz catheter, and SVR was calculated from CO, MAP, and right atrial pressure. M-mode and 2D echocardiograms were obtained from the cross-sectional short-axis view of the left ventricle and recorded shortly before and during treatment when MAP had changed by 20 mmHg. Left ventricular total area (TA) and cavity area (A) including the papillary muscles were obtained from end-systolic 2D echocardiograms, while end-systolic internal diameter (ID) and posterior wall thickness (HW) were measured in the M-mode. Wall stress was calculated in the M-mode as: WSM = 0.33 x SAP x ID/(HW x (1+HW/ID)), and in the 2D mode as: WS2D = 1.33 x SAP x A/(TA-A). STATISTICS: paired t-test (P < 0.05), regression analysis. RESULTS. Afterload alterations were reflected by significant changes of WS2D (-41%, +68%), WSM (-26%, +38%), and SVR (-15%, +50%). WSM and SVR underestimated changes of WS2D by 15%-30%. WSM changes due to SAP rather than to left-ventricular dimensional changes. No correlation was found between WS2D or WSM and SVR. Inter-observer variability for echocardiographic wall stress was reasonable (WS2D 4%, WSM 10%). CONCLUSIONS. Acute changes of left ventricular afterload and dimensions were clearly indicated by 2D measurements. As M-mode measures were not conclusive for left ventricular dimensional changes, WSM was not an appropriate parameter for acute afterload alterations. WS2D is an afterload index superior to WSM that cannot be estimated by SVR.

Blood Pressure↗
PubMed1995

[Effects of serotonin 2 receptor agonists on skeletal muscle preparations in patients with a disposition toward malignant hyperthermia].

In pigs genetically susceptible to malignant hyperthermia (MH), it has been shown that serotonin (5-HT2) receptor agonists can induce MH and "psychotic" behaviour. Both can be prevented by 5-HT2 receptor antagonists. Furthermore, free levels of serotonin in plasma increased concomitantly with clinical and laboratory parameters during halothane-induced MH in pigs. In this study the in vitro-effects of the 5-HT2 receptor agonist1-(2,5-dimethoxy-4-iodophenyl)-2-amino-propane (DOI) were investigated in muscle specimens of MH-susceptible (MHS) and normal (MHN) patients. METHODS. Muscle biopsies were obtained from 37 patients aged 5-69 years (23.6 +/- 5.3 years) with clinical suspicion for MH. The patients were first classified as MHS, MHN or MHE (MH equivocal) by the in vitro contracture test (IVCT) according to the European MH protocol. After MH classification, surplus muscle specimens were subjected to the DOI study. DOI was added to the organ bath in a concentration of 0.02 mmol/l. The in vitro effects on contracture development and muscle twitch were observed for 120 min. RESULTS. Muscle specimens of all patients developed contractures after administration of DOI. However, DOI produced an earlier development of contracture in MHS (17.0 +/- 1.8 min; n = 17) than in MHN (64.7 +/- 5.9 min; n = 15) muscles. In MHS muscles, contractures were more distinct than in MHN muscles; at the end of the experiment, contractures had reached a maximum of 12.5 +/- 0.9 mN in MHS and 5.1 +/- 0.7 mN in MHN muscles. Muscle twitch following DOI administration was reduced significantly in both MHS and MHN muscles. The results of four MHE muscles were comparable with MHS. CONCLUSION. The present study supports the assumption that an altered serotonin system might be involved in the development of MH. In further studies it should investigated whether 5-HT2 receptors of skeletal muscles from MHS subjects are disordered in function or structure. 5-HT2 receptor agonists should be considered as MH-triggering agents.

Adolescent↗
PubMed1995

Alterations of inositol polyphosphates in skeletal muscle during porcine malignant hyperthermia.

Malignant hyperthermia (MH) may result from increased intracellular calcium concentrations. Increased 1,4,5-IP3 concentrations could mediate this increase in Ca2+. In this study we measured inositol polyphosphates in selectively bred MH susceptible (MHS) and MH non-susceptible (MHN) swine. MH crisis was induced by halothane challenge, and dantrolene was administered in order to measure inositol polyphosphates after MH reversal. Muscle biopsies of skeletal muscles of the hind limbs were obtained in random order and inositol polyphosphates determined by high pressure liquid chromatography using a metal dye detection method. Inositol polyphosphates were determined in three groups: (1) MHS vs MHN basal, (2) during MH crisis induced by halothane and (3) following treatment with dantrolene after halothane challenge. Clinical variables (P(_)VO2, P(-)VCO2, PE'CO2 and pH) indicated that MH was readily induced in MHS swine. Basal concentrations of all inositol polyphosphates were higher in MHS swine compared with MHN swine. After halothane challenge, 1,3,4-IP3, 1,3,4,6-IP4 and 1,3,4,5-IP4 concentrations increased in MHS animals compared with the respective baseline values, whereas no changes in MHN animals could be detected. Dantrolene administration decreased inositol polyphosphate concentrations in MHS swine. MHN swine showed no changes in inositol polyphosphates after dantrolene. These findings indicate that inositol polyphosphates may be involved in metabolic changes after triggering and treatment of MH.

Anesthetics, Inhalation↗