The Correlation of Age and Extension Length in DeBakey Type I Aortic Dissection: Are older patients over 70 years at a lower risk?

OBJECTIVES

Age-related atherosclerosis has been shown to cause aortic stiffness and wall rigidification. This analysis aimed to correlate age and dissection extension length in a large contemporary multi-centre study. We hypothesize that younger patients suffer more extensive DeBakey Type I dissection due to aortic wall integrity, allowing unhindered extension within the layers.

METHODS

The perioperative data of 3385 patients from the German Registry for Acute Aortic Dissection Type A (GERAADA) were retrospectively analyzed with regard to postoperative outcomes and dissection extension. Patients with DeBakey Type I aortic dissection (n = 2510) were retrospectively identified and divided into two age-groups for comparison: ≤ 69 years (n = 1741) and ≥ 70years (n = 769). Patients with DeBakey type II dissection or connective tissue disease were excluded from the analysis.

RESULTS

In younger patients (≤ 69 years), aortic dissection involved the supraaortic vessels significantly more often (52.0% vs. 40.1%; p < 0.001) and extended significantly further downstream the aorta: descending aorta (68.4% vs. 57.1%; p < 0.001), abdominal aorta (54.6% vs. 42.1%; p < 0.001), iliac bifurcation (36.6% vs. 26.0%; p < 0.001). Consequently, younger patients also presented with significantly higher incidences of preoperative cerebral (p < 0.001), spinal (p < 0.001), visceral (p < 0.001), renal (p = 0.013) and peripheral (p < 0.001) malperfusion. In older patients (≥70 years), dissection extent was significantly more often limited to the level of the aortic arch (40.9% vs. 29.2%; p < 0.001). No significant difference was found with regard to 30-day mortality (20.7% vs. 23.6%; p = 0.114).

CONCLUSIONS

Extensive DeBakey Type I aortic dissection is less frequent in older patients ≥70 years than in younger patients. In contrast, younger patients suffer more often from preoperative organ malperfusion and associated complications. Postoperative mortality remains high irrespective of age-groups.

The effects of physical exercise on plasma levels of relaxin, NTproANP, and NTproBNP in patients with ischemic heart disease

The insulin-like and vasodilatatory polypeptide relaxin (RLX), formerly known as a pregnancy hormone, has gained interest as a potential humoral mediator in human heart failure. Controversy exists about the relation between plasma levels of RLX and the severity of heart failure. The present study was designed to determine the course of RLX, atrial, and brain natriuretic peptide (NT-proANP and NT-proBNP) during physical exercise in patients with ischemic heart disease (IHD) and to relate hormone levels to peak cardiac power output (CPO) as a measure of cardiopulmonary function with prognostic relevance. 40 patients with IHD were studied during right-heart-catheterization at rest and during supine bicycle ergometry. RLX, NTproBNP, and NTproANP were determined before, during exercise, and after recovery. NT-proANP and NT-proBNP levels increased during maximal charge, and recovery while RLX levels decreased. Cardiac power output at maximal charge correlated inversely with NTproANP and NTproBNP but positively with RLX. Patients with high degree heart failure (CPO < 1.96 W) had higher NTproANP and NTproB-NP and lower RLX levels than patients with low degree heart failure. While confirming the role of NTproANP and NTproBNP as markers for the severity of heart failure, the present data do not support the concept that plasma levels of RLX are related to the severity of myocardial dysfunction and that systemic RLX acts as a compensatory vasodilatatory response hormone in ischemic heart disease.

The metabolic and renal effects of adrenaline and milrinone in patients with myocardial dysfunction after coronary artery bypass grafting

INTRODUCTION

Myocardial dysfunction necessitating inotropic support is a typical complication after on-pump cardiac surgery. This prospective, randomized pilot study analyzes the metabolic and renal effects of the inotropes adrenaline and milrinone in patients needing inotropic support after coronary artery bypass grafting (CABG).

METHODS

During an 18-month period, 251 patients were screened for low cardiac output upon intensive care unit (ICU) admission after elective, isolated CABG surgery. Patients presenting with a cardiac index (CI) of less than 2.2 liters/minute per square meter upon ICU admission - despite adequate mean arterial (titrated with noradrenaline or sodium nitroprusside) and filling pressures - were randomly assigned to 14-hour treatment with adrenaline (n = 7) or milrinone (n = 11) to achieve a CI of greater than 3.0 liters/minute per square meter. Twenty patients not needing inotropes served as controls. Hemodynamics, plasma lactate, pyruvate, glucose, acid-base status, insulin requirements, the urinary excretion of alpha-1-microglobuline, and creatinine clearance were determined during the treatment period, and cystatin-C levels were determined up to 48 hours after surgery (follow-up period).

RESULTS

After two to four hours after ICU admission, the target CI was achieved in both intervention groups and maintained during the observation period. Plasma lactate, pyruvate, the lactate/pyruvate ratio, plasma glucose, and insulin doses were higher (p < 0.05) in the adrenaline-treated patients than during milrinone or control conditions. The urinary excretion of alpha-1-microglobuline was higher in the adrenaline than in the control group 6 to 14 hours after admission (p < 0.05). No between-group differences were observed in creatinine clearance, whereas plasma cystatin-C levels were significantly higher in the adrenaline than in the milrinone or the control group after 48 hours (p < 0.05).

CONCLUSION

This suggests that the use of adrenaline for the treatment of postoperative myocardial dysfunction - in contrast to treatment with the PDE-III inhibitor milrinone - is associated with unwarranted metabolic and renal effects.

Focussing cellular function. Metabolic monitoring in perioperative and Intensive Care Medicine

In the clinical field microdialysis today is a routine technique for monitoring the chemistry of tissues and organs in physiological and pharmacological research on animals. In more than 10.000 papers on microdialysis research it is used to uncover physiological mechanisms and the influence of drugs in almost every organ of the body. Since the first papers describing microdialysis in the human brain microdialysis has become a technique for routine monitoring of energy metabolism especially in neurointensive care. This paper gives an account of the microdialysis technique describing its practical use and interpretation in monitoring energy metabolism and ischemia in different organs with respect to the field of perioperative and intensive care medicine. This article gives an overview over current results of clinical studies using microdialysis in critical care medicine and tries to focus on possible indications for clinical biochemical monitoring. However, despite numerous publications available microdialysis has not been shown to improve outcome of the patients yet.

High myocardial lactate concentration is associated with poor myocardial function prior to cardiopulmonary bypass

AIM

This study was designed to analyse the relationship between myocardial lactate--determined by microdialysis--and hemodynamics during coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB).

METHODS

Twenty consecutive patients with coronary artery disease were enrolled for this prospective, observational study. Microdialysis measurements were performed in the apical region of the heart during periods of 15 to 20 min before, during, and after CPB; hemodynamics and plasma lactate concentrations were determined correspondingly. Correlation analysis revealed a relationship between myocardial lactate concentration and right ventricular ejection fraction at baseline (Spearman's r: 0.6; P=0.02). Patients were thus grouped according to the myocardial lactate concentration at baseline into a high-lactate group (2.5+/-0.7 mmol.l(-1), n=10) and low-lactate group (0.9+/-0.5 mmol.l(-1), n=10).

RESULTS

Preoperative left ventricular ejection fraction was not different between the groups (high-lactate group: 53+/-16%; low-lactate group: 57+/-15%; P=n.s.) Patients in the high-lactate-group had a lower stroke volume index (P=0.005) and right ventricular ejection fraction (P=0.04) before, and higher central venous and pulmonary artery pressures (P<0.01) after CPB. Plasma lactate was significantly higher during CPB in the high-lactate-group (P<0.05). No correlation was observed between myocardial and plasma lactate. Six patients in the high-lactate but none in the low-lactate-group needed inotropic support after weaning from CPB (P=0.01).

CONCLUSIONS

These data are suggestive of an association between subtle myocardial ischemia--detected by microdialysis--and perioperative myocardial dysfunction in patients undergoing CABG. The microdialysis technique may be a valuable adjunct for monitoring myocardial metabolism during cardiac surgery.

Metabolic stress during hypoglycaemia clamp assessed by microdialysis

AIM

Microdialysis allows the biochemical analysis of interstitial fluids as a bedside procedure. This technique is of interest to evaluate the glucose dependent metabolism in hypoglycaemic patients. It was the aim to perform subcutaneous and blood microdialysis during hypoglycaemic clamp experiments in 12 healthy young men to reveal basis data for critical care microdialysis practice.

METHODS

The hyperinsulinaemic clamp was induced with a continuous infusion of 1.5 mU min(-1) kg(-1) insulin (H-insulin, Hoechst, Frankfurt, Germany). A 20% dextrose solution simultaneously was infused at a variable rate to control blood glucose levels. For hypoglycaemia blood glucose levels were reduced to 40 mg/dL for a 30 min period. Glucose, lactate, pyruvate and glycerol concentrations were semicontinuously measured.

RESULTS

The absolute concentrations of glucose and glycerol in blood vs subcutaneous microdialysate were significant different during observation. Until the end of hypoglycaemia, glucose concentration in both compartments declined in parallel, followed by an increase thereafter. During the clamp the subcutaneous glycerol increased threefold, whereas blood glycerol rose with a delay of 15 min and increased only twofold. After the clamp in both compartments glycerol values normalized. The lactate-pyruvate-ratio persisted in normal range throughout the examination.

CONCLUSIONS

In our experiment subcutaneous lipolysis increased faster and more profound than blood microdialysis. We propose the microdialysis technique as an additional monitoring tool in hypoglycaemia patients.