Velocity profile in the main pulmonary artery in a canine model.

The velocity profile of the main pulmonary artery was determined in nine adult, open-chested, mechanically ventilated mongrel dogs using an intraluminal, needle-mounted, range-gated, pulsed Doppler technique. Mean phasic point velocities were determined at 2 mm intervals across the lumen of the vessel, 2 cm above the pulmonary valve, by recording the Doppler shift of an activated 20 MHz piezoelectric crystal, range-gated 3.5 mm in the direction of the pulmonary valve. Mean Reynolds numbers from the main pulmonary artery ranged from 275 to 1140. Radially normalised intraluminal distance versus mean phasic point velocity plots were constructed which demonstrated a curved profile in all 9 dogs. First order regression analysis demonstrated a poor fit (r: 0.05-0.68). Second order (r:0.61-0.97) and third order (r:0.72-0.99) regression analyses markedly improved the fit, confirming the non-linear nature of the velocity profile. Step-wise third order regression analysis to determine the importance of the entry sequence demonstrated that the most important term for determining the regression coefficient was the X2 term in six dogs. In addition, the velocity profile was noted to be shifted, with the highest velocities recorded between the centre of the vessel and the anterior wall in eight of nine dogs (location of highest velocity: +0.26 radius +/- 0.25 (mean +/- SD).

Two-dimensional in vivo pressure/diameter relationships in the canine main pulmonary artery.

Ultrasonic measurement of blood flow within the main pulmonary artery (MPA) requires a precise knowledge of the mean blood velocity within this vessel and the cross-sectional area (CSA). Small conformational changes in the elliptical shape of the MPA have substantial effects on the calculation of CSA and, subsequently, flow. We examined the extent of these changes by measuring the pulsatile and mean elliptical dimensions of the MPA in nine anaesthetised, open-chested, mechanically ventilated mongrel dogs using two pairs of 10 MHz ultrasonic, piezoelectric crystals. These custom-made devices were sutured to the PA adventitia along the long and short cross-sectional axes 2 cm distal to the pulmonary valve. Axial dimensions were collected during normal, elevated (via noradrenaline and fluid additions) and reduced (via exsanguination) PA pressures. We confirmed the linear pressure/diameter response in 15/18 axial data sets (r greater than 0.80). Further, the linear axial responses of the long and short diameters were parallel (7/9, p less than 0.05) and have different zero-pressure intercepts (7/9, p less than 0.0001). A mathematical consequence of this parallelism is predictable, although non-constant, eccentricity. Finally, error analysis of multi-axial measurement techniques were shown to improve CSA accuracy by as much as 50% when compared with uni-axial determinations.

Intraluminal pulsed Doppler evaluation of the pulmonary artery velocity time curve in a canine model of acute pulmonary hypertension.

The velocity pattern of the blood flow in the pulmonary artery was investigated in an animal model of acute pulmonary hypertension. Nine anesthetized, open-chest dogs were embolized with polystyrene microspheres, and the velocity pattern of the blood flow in the pulmonary artery was studied with use of an invasive pulsed Doppler technique. Phasic intraluminal velocity was recorded with use of a miniature piezoelectric crystal activated by 20-MHz Doppler pulses and mounted on the tip of a needle probe introduced into the pulmonary artery. The recorded Doppler quadrature signals were processed by spectral analysis. Significant increases occurred in mean, systolic, and diastolic pulmonary arterial pressures (p less than 0.0002), in pulmonary vascular resistance (p less than 0.005), and in negative velocity time (duration in milliseconds that the mean velocity was directed toward the pulmonic valve) (p less than 0.002). Significant decreases occurred in right ventricular ejection time (p less than 0.006) and in positive velocity time (duration in milliseconds that the mean velocity was directed away from the pulmonic valve) (p less than 0.005). A significant shortening in the time to peak velocity (acceleration time) was found (p less than 0.005). Second-order regression analyses demonstrated an inverse correlation between the ratio of positive velocity time to negative velocity time and the mean pulmonary artery pressure in all animals (r = 0.71). These findings should be compared with the velocity patterns of the blood flow in the pulmonary artery obtained under pulmonary hypertensive conditions due to various causes to facilitate interpretation and understanding of clinical investigations.

Esophagogastrectomy as palliative treatment for esophageal carcinoma: results obtained in the setting of a thoracic surgery residency program.

The palliative treatment of esophageal carcinoma has included intubation, bypass, dilation, irradiation, and esophagogastrectomy. The last has been criticized by some on the basis of high operative morbidity and mortality. To assess the success of this method at our institution, we reviewed the 60 consecutive resections performed for carcinoma of the esophagus from January, 1972, through June, 1983. Forty-six patients had squamous cell tumors and 14, adenocarcinomas. There were 47 men and 13 women, and the mean age was 59.9 years (range, 38.5 to 78.9 years). The most frequent preoperative findings included dysphagia (55), weight loss (34), chest pain (22), and vomiting (49). Fifty (83%) out of the 60 resections were performed by the resident staff under the supervision of an attending surgeon. Four patients died within 30 days of operation, an operative mortality of 6.7%. Immediate causes of death included respiratory failure, myocardial infarction, hemorrhage, and renal failure. One of the patients who died and 3 of the survivors had an anastomotic leak. There were 27 additional complications in 24 patients: respiratory problems (8), arrhythmias (5), pleural effusion (4), gastric outlet obstruction (2), wound infection (2), and 1 each of pulmonary embolus, acute brain syndrome, congestive heart failure, myocardial infarction, chylothorax, and empyema. The one-, two-, three-, and five-year actuarial survival rates were 46%, 27%, 10%, and 5%, respectively. Mean survival for the 46 patients dead at the time of this study was 13.5 months. Outpatient follow-up data were available on 53 (95%) of the operative survivors and showed an absence of dysphagia in 87.5% during most of the follow-up period.(ABSTRACT TRUNCATED AT 250 WORDS)

Major pulmonary resection for suspected but unconfirmed malignancy.

Thoracotomy is not infrequently performed in patients with suspected pulmonary carcinoma but with no histological or cytological confirmation of malignancy. The intraoperative decision to proceed with major pulmonary resection (lobectomy or pneumonectomy) is difficult if a large or central lesion precludes total excisional biopsy. Incisional or needle biopsies violate the principles of good cancer surgery, and the results may be inconclusive if the tumor is missed and areas of associated inflammation or necrosis are sampled. Between January 1, 1970, and December 31, 1980, 303 patients underwent thoracotomy for suspected but unconfirmed malignancy. One hundred twenty-two had a minor resection only, 79 had a major resection (lobectomy or pneumonectomy) after a diagnosis was established by frozen section, and 102 had a major resection without a definitive diagnosis of cancer. Carcinoma subsequently was found in 68% (69) of this group of 102 patients, and benign lesions were identified in the remaining 32% (33), all of whom underwent lobectomy. The diagnoses in these 33 patients included seven granulomas, three hamartomas, nine instances of tuberculosis, and fourteen instances of fibrosis, inflammation, or cystic degeneration. The 2 thirty-day operative deaths in this group of 102 patients occurred among the 69 with malignant disease; 1 died of hemorrhage following pneumonectomy and 1, of respiratory insufficiency after lobectomy. In all 303 patients, there was no difference in operative mortality (p less than 0.01) between lobectomy (2%) and a lesser resection (1.6%). In a patient with a suspicious but inaccessible pulmonary lesion, lobectomy can be performed safely without violating the principles of cancer surgery. This recommendation should probably not be extended to lesions requiring pneumonectomy, because of the increased rates of morbidity and mortality associated with that procedure.

Cardiovascular effects of positive end-expiratory pressure (PEEP) after pneumonectomy in dogs.

Little is known regarding the hemodynamic effect of positive end-expiratory pressure (PEEP) following pneumonectomy. To investigate this, 9 mongrel dogs underwent PEEP before and after lung resection. With the chest closed, the dog anesthetized, and partial pressure of carbon dioxide constant, PEEP was added in increments of 2 mm Hg until the animal's condition became hemodynamically unstable. At each level of PEEP, aortic, pulmonary, left atrial, and central venous pressures were monitored while aortic flow (cardiac output) was determined with an electromagnetic probe and airway pressure was measured with a Millar catheter in the respiratory tubing. Pneumonectomy was then performed, PEEP was again sequentially added, and the same measurements were recorded. Both before and after pneumonectomy, a strong positive linear correlation exists between the level of PEEP and pulmonary vascular resistance (PVR) (r greater than 0.74; p less than 0.05). Also, there is a high negative linear correlation between the level of PEEP and cardiac output (r greater than -0.76; p less than 0.05). At 0 mm Hg of PEEP, the PVR is higher after pneumonectomy than before (p less than 0.02). The incremental elevation in PVR persists after pneumonectomy at each level of PEEP, and in 5 of the 9 dogs the slope of the linear regression line relating PVR to PEEP was steeper following resection (p less than 0.05), thereby demonstrating an exaggerated effect of PEEP on PVR. In addition, all animals had a lower cardiac output at each comparable level of PEEP following pneumonectomy (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Elective pulmonary lobectomy: factors associated with morbidity and operative mortality.

Periodic review of clinical results is essential to ensure that high-quality patient care is maintained. To that end, we reviewed the morbidity and operative mortality in a consecutive series of 369 pulmonary lobectomies performed between January 1, 1970, and December 31, 1983. There were 251 male and 118 female patients with a mean age of 50.6 years. The thirty-day operative mortality was 2.2% (8/369), with 6 of these deaths related primarily to respiratory insufficiency. Two hundred twenty-four postoperative management problems occurred in 151 patients and included arrhythmia, air leak, pneumothorax, respiratory difficulties, postoperative bleeding, pleural effusion, wound infection, myocardial infarction, pulmonary embolus, empyema, bronchial stump leak, and lobar gangrene. Multiple factors were related to the occurrence of postoperative morbidity and mortality using both chi-square analysis to examine each individual item and discriminant analysis to evaluate their interaction. Chi-square tabulation showed no difference in the occurrence of major postoperative complications (p greater than 0.05) related to the side of operation, an abnormal preoperative electrocardiogram, a forced vital capacity of 2.8 liters or less, a one-second forced expiratory volume (FEV1) of less than 1.7 liters, an oxygen tension of less than 60 mm Hg, or the seniority of the surgeon (resident versus attending). An increased number of complications (p less than 0.05) was found in male patients, in patients operated on for carcinoma, and in patients older than 60 years. Stepwise discriminant analysis included FEV1 as a significant predictor of postoperative complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Characteristics of blood flow velocity in the hypertensive canine pulmonary artery.

Pulmonary artery blood flow velocity was measured in 15 dogs by a recently developed direct intraluminal pulsed Doppler technique. Changes in velocity characteristics under conditions of experimentally induced hypoxic pulmonary hypertension were observed. Experimental conditions (fractional inspired oxygen concentration = 0.10) produced significant increases in mean pulmonary artery pressure and pulmonary vascular resistance. Overall and maximal negative velocity increased with pulmonary hypertension. Negative velocity occurred predominantly in the posterior half of the pulmonary artery during both control and experimental conditions. With pulmonary hypertension, diastolic negative velocity increased only in the posterior half of the pulmonary artery and systolic negative velocity decreased only in the anterior half. More basic knowledge of pulmonary artery blood flow characteristics may facilitate an informed approach to noninvasive detection of pulmonary hypertension. Direct measurements by this recently developed intraluminal technique will be useful in studying various conditions with altered pulmonary blood flow.

The significance of elevation of serum phosphate levels in experimental intestinal ischemia.

It has been suggested that the serum phosphate level is significantly elevated early in massive intestinal infarction. We attempted to determine whether or not this elevation in serum phosphate level is indeed an early and reliable diagnostic finding and to define the relationship between this elevation, the re-establishment of mesenteric blood flow and the viability of the intestinal wall. Significant elevation in serum phosphate value occurred after four hours of ischemia. This was associated with irreversibility of the ischemic process and intestinal necrosis according to an intravenous fluorescein test and pathologic data. The results of other superior mesenteric artery-12 parameters followed were erratic and appeared to have no diagnostic value in acute mesenteric arterial occlusion. Significant serum phosphate level elevation occurs in arterial intestinal ischemia, but this is not an early diagnostic sign, becoming significant only after irreversible necrosis of the intestine.

Peritoneal lavage with povidone-iodine solution in experimentally induced peritonitis.

Two experimental studies were carried out upon dogs to clarify the efficacy of peritoneal povidone-iodine lavage in peritonitis. With an experimental model of peritonitis which closely resembles the clinical situation, we found that peritoneal lavage with povidone-iodine was not more effective than other lavage regimens in decreasing bacterial colony counts and was associated with an early 100 per cent mortality. Renal function was not affected by the treatment with this antiseptic solution. However, we found a statistically significant superimposed metabolic acidosis in the peritonitis group treated with povidone-iodine when compared with the other groups, by means of a significant decrease in base excess, p less than 0.01, at the two hour postlavage measures. This metabolic acidosis was also observed in normal dogs undergoing peritoneal lavage with povidone-iodine, showing a significant decrease in serum bicarbonate level one hour, p less than 0.05, and three hours, p less than 0.01, three hours postlavage, when compared with a sham laparotomy group in the nonperitonitis study. This has not previously been experimentally investigated. In view of these results, we do not recommend the clinical use of povidone-iodine solution for peritoneal lavage in peritonitis.

Changes in ventricular hemodynamics caused by a systemic-pulmonary shunt.

Systemic pulmonary shunts are both surgically created (Blalock-Taussig anastomosis) and obliterated (patent ductus arteriosus), but the effects of such a vascular communication on left ventricular hemodynamics have not been examined quantitatively. To study these effects, innominate arterial allografts were sutured between the descending thoracic aorta and the left main pulmonary artery in nine mongrel dogs. Left ventricular output (LVO) and shunt flow (SF) were monitored with electromagnetic flow probes while simultaneous phasic and mean pressures were recorded from the right atrium, aorta (AOP), and pulmonary artery. Data points (192) were analyzed while SF was varied between 0.02 and 5.5 liters/min using a variable-sized constricting band. Regression analysis showed increases (P less than 0.01) in LVO, stroke work (SW), and stroke volume (SV) in all dogs which were linearly related to SF (r = 0.64-0.99). Increasing SF was also associated with decreases (P less than 0.01, r = 0.61-0.99) in resistance (RES) facing the left ventricle and in diastolic (D) AOP. To compensate for differences in allograft size and to quantify the effects of a patent shunt, the regression equations were used to compare the percentage change in all parameters at SF = 0 and SF = 1.5 liters/min. Increases occurred in SV (46 +/- 21%), SW (32 +/- 14%), and LVO (48 +/- 21%), and decreases were present in DAOP (15 +/- 12%) and RES (32 +/- 13%). These data show that despite the decreases in pressure or the decreases in resistance facing the left ventricle in the presence of a systemic pulmonary shunt, a substantial increase in stroke work occurs.(ABSTRACT TRUNCATED AT 250 WORDS)