Assessment of Spinal Cord Ischemia With Near-Infrared Spectroscopy: Myth or Reality?

Non-invasive near-infrared spectroscopy is gaining popularity in the detection of spinal cord ischemia following aortic aneurysm repair. However, practical recommendations are lacking. This review focuses on the physiological and anatomical background, as well as on the clinical implementations of near-infrared spectroscopy as a tool for monitoring ischemia of the spinal cord. Clinical recommendations based on the currently available evidence are rendered.

The Concept of Risk Assessment and Being Unfit for Surgery.

The concept of risk assessment and the identification of surgical unfitness for vascular intervention is a particularly controversial issue today as the minimally invasive surgical population has increased not only in volume but also in complexity (comorbidity profile) and age, requiring an improved pre-operative selection and definition of high risk. A practical step by step (three steps, two points for each) approach for surgical risk assessment is suggested in this review. As a general rule, the identification of a "high risk" patient for vascular surgery follows a step by step process where the risk is clearly defined, quantified (when too "high"?), and thereby stratified based on the procedure, the patient, and the hospital, with the aid of predictive risk scores. However, there is no standardized, updated, and objective definition for surgical unfitness today. The major gap in the current literature on the definition of high risk in vascular patients explains the lack of sound validated predictive systems and limited generalizability of risk scores in vascular surgery. In addition, the concept of fitness is an evolving tool and many traditional high risk criteria and definitions are no longer valid. Given the preventive purpose of most vascular procedures performed in elderly asymptomatic patients, the decision to pursue or withhold surgery requires realistic estimates not only regarding individual peri-operative mortality, but also life expectancy, healthcare priorities, and the patient's primary goals, such as prolongation of life versus maintenance of independence or symptom relief. The overall "frailty" and geriatric risk burden, such as cognitive, functional, social, and nutritional status, are variables that should be also included in the analyses for stratification of surgical risk in elderly vascular patients.

Cost/benefit of synbiotics in acute infectious gastroenteritis: spend to save.

The cost/benefit ratio of probiotics in the ambulatory treatment of acute infectious gastro-enteritis with or without a synbiotic food supplement (containing fructo-oligosaccharides and probiotic strains of Streptoccoccus thermophilus, Lactobacillus rhamnosus, Lactobacillus acidophilus, Bifidobacterium lactis and Bifidobacterium infantis) has been studied. 111 children (median age 37 and 43 months for the synbiotic and placebo group, respectively) with acute infectious gastroenteritis were included in a randomised, prospective placebo-controlled trial performed in primary health care. All children were treated with an oral rehydration solution and with the synbiotic food supplement (n=57) or placebo (n=54). Physicians were allowed to prescribe additional medication according to what they considered as 'necessary'. Cost of add-on medication and total healthcare cost were calculated. Median duration of diarrhoea was 1 day shorter (95% confidence interval -0.6 to -1.9 days) in the symbiotic than in the placebo group (P<0.005). Significantly more concomitant medication (antibiotics, antipyretics, antiemetics) was prescribed in the placebo group (39 prescriptions in 28 patients) compared to the synbiotic group (12 prescriptions in 7 patients) (P<0.001). The difference was most striking for antiemetics: 28 vs. 5 prescriptions. The cost of add-on medication in the placebo group was evaluated at € 4.04/patient (median 4.97 (interquartile (IQ) 25-75: 0-4.97)) vs. € 1.13 /patient in the synbiotic arm (P<0.001). If the cost of the synbiotic is considered, median cost raised to € 7.15/patient (IQ 25-75: 7.15-7.15) (P<0.001). The extra consultations needed to prescribe the concomitant medication resulted in a higher health care cost in the placebo group (€ 14.41 vs. € 10.74/patient, P<0.001). Synbiotic food supplementation resulted in a 24 h earlier normalisation of stool consistency. Although use of the synbiotic supplementation increased cost, add-on medication and extra consultations were reduced, resulting in a reduction of health care cost of 25%.

Assessment of length-dependent regulation of myocardial function in coronary surgery patients using transmitral flow velocity patterns.

BACKGROUND: In a subset of coronary surgery patients, a transient increase in cardiac load by leg elevation resulted in a decrease in maximal rate of pressure development (dP/dtmax) and a major increase in end-diastolic pressure (EDP). This impairment of left ventricular (LV) function appeared to be related to a deficient length-dependent regulation of myocardial function. The present study investigated whether analysis of transmitral flow patterns with transesophageal echocardiography constituted a noninvasive method to identify these patients. METHODS: High-fidelity LV pressure tracings and transmitral flow signals were obtained in 50 coronary surgery patients during an increase in cardiac load by leg elevation. Using linear regression analysis, changes in transmitral E-wave velocity and deceleration time (DT) were related to changes in dP/dtmax and EDP. RESULTS: Changes in dP/dtmax with leg elevation were closely related to corresponding changes in E-wave velocity (r = 0.81; P < 0. 001) and to changes in DT (r = 0.78; P < 0.001). Similarly, changes in EDP were related to changes in E-wave velocity (r = 0.83; P < 0. 001) and to changes in DT (r = 0.84; P < 0.001). The decrease in dP/dtmax and the major increase in EDP in some patients was associated with an increase in E-wave velocity and a decrease in DT, indicating development of a restrictive LV filling pattern. CONCLUSIONS: Impairment of LV function with leg elevation was associated with the development of a restrictive transmitral filling pattern. Analysis of transmitral flow patterns by means of transesophageal echocardiography therefore allowed noninvasive identification of a subset of coronary surgery patients with impaired length-dependent regulation of LV function.

Continuous total intravenous anesthesia, using propofol and fentanyl in an open-thorax rabbit model: evaluation of cardiac contractile function and biochemical assessment.

Effects are reported of an anesthetic protocol involving use of predetermined intravenous (i.v.)-administered drug doses during acute experimental procedures in vagotomized, New Zealand White rabbits with open thorax (n = 20) in a nonsurvival study. After induction of anesthesia by intramuscular (i.m.) administration of ketamine hydrochloride (25 mg/kg of body weight) and xylazine hydrochloride (15 mg/kg), continuous total intravenous anesthesia (TIVA) with propofol (0.6 mg.kg-1.min-1), fentanyl (0.48 micrograms.kg-1.min-1) and the neuromuscular agent vecuronium bromide (0.003 mg.kg-1.min-1) was maintained. Oxygenation conditions, acid-base balance, biochemical and hemodynamic variables, and cardiac contractile function were assessed. Measurements were made and blood analysis was done at the moment of ear vein catheterization (P1); before (P2) and after (P3) sternotomy; after complete instrumentation (P4); and at the beginning (T1), in the middle (T2), and at the end (T3) of the experimental protocol. From T1 to T3, heart rate was kept constant by use of atrial pacing at a rate of 235 +/- 15 beats/min. During surgical preparation and instrumentation, hemoglobin (Hb) concentration decreased from 12.5 +/- 0.9 g/dl (mean +/- SEM) to 7.7 +/- 0.7 g/dl and remained stable thereafter. Blood gas analysis (PO2, PCO2, pH, HCO3-, base excess, measured SaO2) and measurement of plasma lactate concentration revealed constant, adequate oxygenation. Plasma electrolyte values (Na+, Cl-, K+, Ca2+) remained within physiologic ranges throughout. Blood glucose concentration increased from 229 +/- 30 mg/dl at P1 to 382 +/- 34 mg/dl at P3. At T1, glycemia had returned to normal values and remained stable. Heart rate, blood pressure, ventricular elastance (Ees), and diastolic stiffness constant (Kc) remained stable throughout. Other indices of ventricular function (dP/dtmax, thickening, ejection duration, and maximal left ventricular pressure) remained unaltered as well. Left ventricular relaxation (dP/dtmin, tau) did not change. After anesthesia induction by i.m. administration of ketamine and xylazine, TIVA with predetermined drug dosages of propofol and fentanyl provided stable cardiovascular function for open-thorax long-term experimental observations in a nonsurvival setting.

Relaxation-systolic pressure relation. A load-independent assessment of left ventricular contractility.

This contribution reviews the regulation of left ventricular pressure (LVP) fall by load and relates this regulation to left ventricular contractility. Load regulation of LVP fall has to be distinguished from neurohumoral regulation, from effects induced by arterial reflected waves and from long-term load effects on contractility. The response of LVP fall to a moderate elevation of systolic LVP is highly variable. It depends on the ratio between the actual systolic pressure and peak isovolumetric pressure, defined as "relative load". Up to a relative load of 81% to 84%, LVP fall accelerates. Above this relative load, LVP fall decelerates. Depending on the level of relative load there is a wide variety of effects ranging from moderate acceleration of LVP fall to marked deceleration of LVP fall. Acceleration of LVP fall in response to a load elevation is associated with normal cardiac function, while slowing of LVP fall is associated with impaired cardiac function. Similar but opposite effects are observed with reductions of systolic LVP. Effects of changes in systolic LVP on time constant tau reveal a fair correlation with systolic elastance (Ees), peak dP/dtmax and regional fractional shortening (or ejection fraction). There is an excellent correlation with measured isovolumetric LVP, indicating that contraction-relaxation coupling is close when contractility is expressed in terms of peak isovolumetric pressure. Assessment of contractility with systolic LVP-relaxation relation is precise and load independent and can be performed with the sole use of a high-fidelity pressure gauge positioned in the left ventricular cavity.