Abdominal Compartment Research Articles

Frequency of nodal metastases to the upper mediastinum in Barrett's cancer.

In Barrett's cancer, the frequency of lymph node metastases to the middle and upper mediastinum has rarely been analyzed because it requires a complete mediastinal lymphadenectomy. Fifty-one patients with esophageal adenocarcinoma underwent transthoracic en-bloc esophagectomy with two-field lymph node dissection. A meticulous work-up of the resected specimen allowed a specific assignment of each single lymph node to defined groups of the abdominal and mediastinal compartment. Histopathology classified the lymph nodes as metastatic or nonmetastatic. A total of 1706 lymph nodes were resected, with a mean of 33.5 lymph nodes per patient (range, 13-74). Of 51 patients, 28 (54.9%) were classified as pN1; 7 (25%) of 28 pN1 patients had nodal metastases at the level of the tracheal bifurcation (3 of 28 patients) or in the upper mediastinum (5 of 28 patients). In all 28 pN1 patients, the abdominal compartment was involved. The distribution of nodal metastases demonstrated that the main lymphatic spread occurred close to the primary tumor, along the lesser curvature and the left gastric artery. Adenocarcinomas of the distal esophagus have a bidirectional lymphatic spread to the mediastinum and the abdomen. Two-field lymphadenectomy seems to be an adequate surgical approach for this tumor entity to achieve a complete nodal clearance.

Relationship between abdominal fat compartments and glucose and lipid metabolism in early postmenopausal women.

The relationships between abdominal and pelvic fat compartments and glucose and lipid metabolism were investigated in early postmenopausal women. Fifty-five healthy, postmenopausal women aged 52-53 yr participated in the study. Fat distribution (intra-abdominal and sc abdominal fat, and intrapelvic and sc pelvic fat) was estimated by computed tomography. Insulin sensitivity was assessed by euglycemic hyperinsulinemic clamp. In a multiple regression analysis, the size of the intra-abdominal fat compartment was the only significant predictor of insulin sensitivity (r(2) = 24%; P = 0.0002). Plasma triglycerides were closely related to the size of the intra-abdominal fat compartment (r(2) = 26%; P < 0.0001), whereas plasma free fatty acid concentrations only correlated to the size of the sc abdominal fat compartment (r(2) = 18.5%, P = 0.001). In early postmenopausal women the amount of the intra-abdominal fat strongly influences insulin sensitivity and plasma triglyceride levels, whereas plasma free fatty acids are closely related to the amount of the sc abdominal fat. Accordingly, from a metabolic standpoint it seems most essential to reduce intra-abdominal fat in postmenopausal women.

Pathophysiological basis of orthostatic hypotension in autonomic failure.

In patients with autonomic failure orthostatic hypotension results from an impaired capacity to increase vascular resistance during standing. This fundamental defect leads to increased downward pooling of venous blood and a consequent reduction in stroke volume and cardiac output that exaggerates the orthostatic fall in blood pressure. The location of excessive venous blood pooling has not been established so far, but present data suggest that the abdominal compartment and perhaps leg skin vasculature are the most likely candidates. To improve the orthostatic tolerance in patients with autonomic failure, protective measures that reduce excessive orthostatic blood pooling have been developed and evaluated. These measures include physical counter-manoeuvres and abdominal compression.

The management of patients with advanced cancer (II)

In this second article in the series, obstruction of hollow viscera in patients with advanced malignant disease is discussed. The obstruction of such structures can be associated with the development of painful and incapacitating symptoms, often in patients who have a limited life expectancy. This obstruction may be caused by the primary tumour, compression from adjacent tumour-draining lymph nodes, the presence of metastases distant from the site of the primary tumour or to adhesions within the abdominal compartment (usually as a result of previous surgery). The organs most often affected are the oesophagus, the intestine (small and large), the biliary tree and the genito-urinary tract. Obstruction of each of these organs and its management is discussed in more detail below.

Changes in chest wall compartment volumes on induction of anaesthesia with eltanolone, propofol and thiopentone

Changes in the expiratory dimensions of the rib cage and abdomen on induction of anaesthesia with eltanolone, propofol and thiopentone were measured in 76 patients using respiratory inductance bands. Calibration of the respiratory inductance plethysmograph was by simultaneous flow measurement with a pneumotachograph. Movement of the vertebral column was restrained with a rigid mattress to allow volume change to be estimated more accurately from rib cage and abdominal dimensions. Rib cage volumes decreased by a median of 125 ml, while the median change in the abdominal compartment was 0. These findings suggest that a reduction in rib cage volume may contribute to the decrease in functional residual capacity after induction of anaesthesia, but that changes in the diaphragmatic-abdominal compartment are not important.

Mechanical abdomino/heart/lung interaction.

It is generally assumed that inspiration will enhance both superior and inferior vena cava (SVC and IVC) blood flows due to the decrease in right atrial pressure produced by the fall in intrathoracic pressure. However, inspiration can also increase abdominal pressure due to the descent of the diaphragm. Using a model of abdominal vascular zone conditions, analogous to pulmonary vascular zone conditions, the abdominal venous compartment can be viewed as either a capacitor (zone III abdomen) or as a collapsible Starling resistor (zone II abdomen). This dual nature of the abdominal venous bed can explain how an inspiratory increase in abdominal pressure can increase IVC flow with hypervolaemia, but increase IVC flow with hypovolaemia. Combined generalized increases in abdominal pressure and focal forces over the liver can be shown to be an essential element in the pathogenesis of a Kussmaul's sign. Increases in abdominal pressures produced by active diaphragmatic descent can increase the total IVC venous return by enhancing the splanchnic IVC flow under relatively hypervolaemic conditions, but decrease the total IVC venous return by impeding the non-splanchnic IVC flow under hypovolaemic conditions. Results are presented which suggest that the concept of abdominal vascular zone conditions is useful to understand overall directions of changes in total and regional venous return during normal and obstructed breathing and may provide useful analysis of the haemodynamic events which occur in obstructive sleep apnoea.

Prevention of venous air embolism in paediatric neurosurgical procedures performed in the sitting position by combined use of MAST suit and PEEP

We studied 60 children undergoing neurosurgical procedures in the sitting position. Routine monitoring included ECG, pulse oximetry, invasive arterial pressure, in particular mean arterial pressure (MAP), and right atrial pressure (RAP). Children were allocated to two groups. In group B lower body positive pressure and positive end-expiratory pressure (PEEP) were used for preventing venous air embolism (VAE). In this group, antishock trousers (MAST suit) were adjusted in supine children. After induction of anaesthesia, different positions were studied: supine and sitting before MAST suit inflation, sitting with MAST suit inflated up to a pressure of 40 mmHg in the lower compartments and 30 mmHg in the abdominal compartment, and finally a combination of lower body positive pressure and PEEP of 8-10 cm H2O. In group A no MAST suit or PEEP was used. Continuous monitoring of end-tidal carbon dioxide pressure throughout (PE'CO2) was used to detect VAE. In order to evaluate the transmission of pressures from the right atrium to the veins at the base of the skull, jugular bulb venous pressure (JBVP) was measured in 20 patients by retrograde catheterization. The incidence of VAE was compared in the two groups. On placing children into the sitting position, a significant decrease in RAP and JBVP was noted without significant changes in MAP in the two groups. Inflation of the MAST suit induced a dramatic increase in RAP and JBVP, reinforced by addition of PEEP. There was a strong positive relationship between RAP and JBVP. There were no deleterious side effects or differences between the two groups in peroperative blood product requirements or surgical general conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Improvement of diaphragmatic function by a thoracic extradural block after upper abdominal surgery.

The effects on diaphragmatic function of a thoracic epidural block were assessed in 13 patients after upper abdominal surgery (UAS). Lung volumes and tidal changes in chest wall circumferences and gastric (delta Pgas) and esophageal (delta Pes) pressures were measured pre- and postoperatively. Volume displacement of the abdomen divided by tidal volume (delta VAB/VT) and delta Pgas/delta Pes were taken as indices of the diaphragmatic contribution to tidal breathing. These respiratory variables were obtained in the postoperative period, before and after epidural injection of 0.5% plain bupivacaine to achieve a block up to the T4 segment. UAS was constantly associated with a decrease in VT, delta VAB/VT, delta Pgas/delta Pes, and forced vital capacity (FVC). Epidural block was associated with an increase in VT, delta VAB/VT, and FVC. delta Pgas and delta Pgas/delta Pes returned to their preoperative values. It is concluded that: 1) diaphragmatic dysfunction observed after UAS is partially reversed by thoracic epidural block; and 2) that inhibitory reflexes of phrenic activity arising from the abdominal compartment (abdominal wall and/or viscera) could be involved in this diaphragmatic dysfunction.

Rib cage and abdominal contributions to ventilatory response to CO2 in infants.

We have measured the ventilatory response to inhaled CO2 of six newborn infants in rapid-eye-movement (REM) and non-REM (NREM) sleep. Ventilatory responses were measured using the Read rebreathing technique. The response was further partitioned into the volume contributions of the rib cage and abdominal compartment using the respiratory inductance plethysmograph. Sleep state was defined by electroencephalogram, electrooculogram, and behavioral criteria. In NREM sleep, there was a highly significant linear correlation between both tidal volume (VT) and instantaneous minute ventilation (VI) with CO2. Among infants, the slope of VT varied from 1.0 to 0.34 ml X Torr-1 X kg-1. However, these differences were largely due to differences in rib cage contribution, which varied from 0.56 to -0.08 ml X Torr-1 X kg-1. The abdominal contribution was similar among infants (0.41-0.56 ml X Torr-1 X kg-1). In REM, the slopes of VI were less steep than in NREM, with greater breath-to-breath variability. Slopes of VT also tended to be lower. The abdominal responses were similar to those in NREM, whereas the rib cage response was low and negative in three studies. We conclude that the slope of the CO2 response curve is primarily determined by the extent of rib cage recruitment.

Contribution of rib cage and abdomen-diaphragm to tidal volume during CO2 rebreathing

In man, there is wide interindividual range in the tidal volume response to CO2. To determine which (rib cage or abdomen-diaphragm) compartment had a greater influence on this range, ventilatory response to CO2 was measured, using Read's method, in eight men and two women seated in a constant-pressure body plethysmograph. Rib cage and abdominal tidal volume was simultaneously measured using magnetometers. Correcting for body size, the tidal volume response of the abdominal compartment was similar in all subjects, whereas that of the rib cage was larger in subjects with high tidal volume response to CO2; a significant correlation was found (P less than 0.01). Rib cage volume displacement lagged behind abdominal in all subjects; phase lag was greatest in the subject with the lowest ventilatory response to CO2. These results suggest that, at high levels of ventilation, a larger volume displacement of the rib cage may reflect a more effective coupling of the diaphragm pressure generator to it or alternatively a reduction in its impedance relative to the abdominal compartment.