Surgical strategies in very-low-birthweight neonates with necrotizing enterocolitis

Very-low-birthweight (VLBW) neonates are more prone to complications and death than term infants are. In a 15-year period, 19 neonates with VLBW were operated on for necrotizing enterocolitis (NEC). Indications for operation were pneumoperitoneum in 12 and deterioration of general condition in 7. Bowel resection and intestinal diversion was performed in 12, a lateral enterostomy at the site of perforation was created in 5, and 2 neonates with necrosis of the whole bowel underwent an exploratory laparotomy without any further surgical treatment. Surgical complications were found in one-third of the patients. The mortality rate was significantly higher when the ileum was affected. The survival rate was 68%. Prior to 1984 the survival rate was 37% (3/8); subsequently, it has improved to 91% (10/11) as a result of improved intensive therapy.     

Systolic Blood Pressure Revisited

The clinical importance of systolic blood pressure (SBP) needs no emphasis. Its determinants are well known, but recent studies of one of these determinants, arterial distensibility, have led to results that now have clinical relevance. This review summarizes the role of arterial stiffness in ventricular-vascular coupling in the normal circulation and that disordered by aging and hypertension. The discussion defines the unfamiliar terms of compliance, distensibility and modulus and indicates how they are measured. Such measurements have increased our understanding of the parts played by the inhomogeneity of the arterial tree and reflected pressure waves in governing SBP. Elevated SBP is a recognized risk factor for cardiovascular complications among older patients, but when this elevation is due to a stiffened arterial tree, diastolic blood pressure (DBP) is necessarily reduced. Early epidemiologic studies in hypertension required a DBP ≥90 mm Hg for hospital admission. They therefore excluded persons with high SBP, low DBP and very wide pulse pressure (PP). More recent inclusion of such patients has shown that elevation of SBP and PP is a strong predictor of cardiovascular risk. These considerations point to a possible redefinition of hypertension to include patients with lower DBP and to the inaccuracy but indispensability of the brachial artery pressure as a surrogate for aortic pressure—the pressure the heart sees. Finally, we review the known effects of available antihypertensive drugs on the arterial wall and indicate possible future directions of research stemming from wider understanding of the role of arterial distensibility in hypertension.

(J Am Coll Cardiol 1997;29:1407–13)     

Brain lactate and alanine-glutamate ratios during and after asphyxia in rats

Recently, Conger, Garcia, Kauffman, Lust, Murakami and Passonneau, (1981) proposed the use of brain alanine-glutamate ratios (A:G) for the prediction of outcome after brain ischemia. This study evaluates this parameter and brain lactate concentration during and after asphyxial insults in rats. During the first 15 min of asphyxial death in rats (n = 37), lactate increased sharply from mean values of 1.48 to 18.06 mumol g-1 wet brain, and thereafter to 19.44 mumol g-1 wet brain at 180 min. During total body asphyxia (n = 38) and recovery after resuscitation, brain lactates increased to mean values of 15 and 17.5 mumol g-1 wet brain at 5 and 10 min, respectively, to recover after 30-60 min to baseline. The alanine-glutamate ratios did not rise during the insult; however, after restoration of circulation, the ratios rose to peak at about 15 min post-restoration of circulation and recovered slowly during the next 165 min to still slightly increased levels. During intermittent asphyxia (n = 15), lactate and alanine-glutamate ratios followed the same patterns as found before except at lower levels. The conclusions of this study are: (1) brain lactate concentrations had no value in predicting the potential of recovery; (2) increased lactate concentrations during recovery indicated secondary insult; (3) brain A:G's did not increase during asphyxiation; (4) brain alanine-glutamate ratios increased after restoration of circulation and may have reflected the quality of reflow; (5) increased ratios during recovery beyond 20 min indicated secondary insult. Brain alanine-glutamate ratios could not be used for prediction of outcome in asphyxial insults in rats.     

Pulsatile diameter and elastic modulus of the aortic arch in essential hypertension: a noninvasive study

A noninvasive evaluation of the aortic arch diameter was performed in 16 subjects with sustained essential hypertension and in 15 normal subjects of similar age, gender and body surface area. In all subjects, measurements were obtained of brachial mean arterial pressure and pulse pressure, cardiac mass (judged on echocardiography) and carotid-femoral pulse wave velocity together with ultrasound determinations of aortic arch diastolic and systolic diameter (suprasternal window). For each subject, pulsatile change in aortic diameter, strain and aortic arch elastic modulus were calculated. Compared with normal subjects, the hypertensive subjects showed an increase in aortic arch diameter (diastolic diameter 29.6 +/- 1.0 versus 25.4 +/- 1.0 mm, p less than 0.01), in elastic modulus (1.071 +/- 0.131 versus 0.526 +/- 0.045 10(5) N.m-2, p less than 0.001) and pulse wave velocity (11.8 +/- 0.5 versus 8.9 +/- 0.3 m/s, p less than 0.001). In the study group, a positive correlation was observed between diastolic aortic arch diameter and mean arterial pressure (r = 0.54, p less than 0.01) and between elastic modulus and cardiac mass (r = 0.60, p less than 0.01). Elastic modulus and age were positively correlated (r = 0.73, p less than 0.01) in hypertensive but not in normal subjects (r = 0.08, NS). This study is the first to demonstrate noninvasively that both the aortic arch diameter and the elastic modulus are increased in patients with sustained uncomplicated essential hypertension. These findings suggest that the increase in elastic modulus could influence the development of cardiac hypertrophy, and that both age and blood pressure act independently as factors that alter the arterial wall of subjects with sustained essential hypertension.     

Baroreflex sensitivity and cardiopulmonary blood volume in normotensive and hypertensive patients.

Baroreflex sensitivity and cardiopulmonary blood volume were determined in 95 men, including normotensive and hypertensive subjects with normal renal function and balanced sodium intake and urinary output. Baroreflex sensitivity was estimated by determining the slope of the regression line relating the increase of systolic pressure to the cardiac slowing after transient rises of arterial pressure. A technique of gradual atropinisation was used to evaluate the parasympathetic mediated component of the reflex. With this method, it was possible to calculate the exact atropine dose abolishing the reflex sensitivity. This index was not dependent on age. It was negatively correlated to the diastolic pressure in normotensive patients but not in hypertensive patients. The ratio between the cardiopulmonary and the total blood volume was considered as an index of sympathetic venous tone. This ratio was positively correlated to the diastolic pressure in normotensive patients, but not in hypertensive patients. This study strongly suggests that a precise sympathetic-parasympathetic balance existed in the normotensive patients. This balance was disrupted in the hypertensive patients pointing to abnormalities in the autonomic nervous system of permanently hypertensive patients.