Soluble complement receptor-1 protects heart, lung, and cardiac myofilament function from cardiopulmonary bypass damage.

BACKGROUND: Host defense system activation occurs with cardiopulmonary bypass (CPB) and is thought to contribute to the pathophysiological consequences of CPB. Complement inhibition effects on the post-CPB syndrome were tested with soluble complement receptor-1 (sCR1). METHODS AND RESULTS: Twenty neonatal pigs (weight 1.8 to 2.8 kg) were randomized to control and sCR1-treated groups. LV pressure and volume, left atrial pressure, pulmonary artery pressure and flow, and respiratory system compliance and resistance were measured. Preload recruitable stroke work, isovolumic diastolic relaxation time constant (tau), and pulmonary vascular resistance were determined. Pre-CPB measures were not statistically significantly different between the 2 groups. After CPB, preload recruitable stroke work was significantly higher in the sCR1 group (n=5, 46.8+/-3.2x10(3) vs n=6, 34.3+/-3.7x10(3) erg/cm(3), P=0.042); tau was significantly lower in the sCR1 group (26.4+/-1.5, 42.4+/-6. 6 ms, P=0.003); pulmonary vascular resistance was significantly lower in the sCR1 group (5860+/-1360 vs 12 170+/-1200 dyn. s/cm(5), P=0.009); arterial PO(2) in 100% FIO(2) was significantly higher in the sCR1 group (406+/-63 vs 148+/-33 mm Hg, P=0.01); lung compliance and airway resistance did not differ significantly. The post-CPB Hill coefficient of atrial myocardium was higher in the sCR1 group (2.88+/-0.29 vs 1.88+/-0.16, P=0.023). CONCLUSIONS: sCR1 meaningfully moderates the post-CPB syndrome, supporting the hypothesis that complement activation contributes to this syndrome.

Inhaled nitric oxide, right ventricular efficiency, and pulmonary vascular mechanics: selective vasodilation of small pulmonary vessels during hypoxic pulmonary vasoconstriction.

OBJECTIVE: In the setting of acute pulmonary artery hypertension, techniques to reduce right ventricular energy requirements may ameliorate cardiac failure and reduce morbidity and mortality. Inhaled nitric oxide, a selective pulmonary vasodilator, may be effective in the treatment of pulmonary artery hypertension, but its effects on cardiopulmonary interactions are poorly understood. METHODS: We therefore developed a model of hypoxic pulmonary vasoconstriction that mimics the clinical syndrome of acute pulmonary hypertension. Inhaled nitric oxide was administered in concentrations of 20, 40, and 80 ppm. RESULTS: During hypoxic pulmonary vasoconstriction, the administration of nitric oxide resulted in a significant improvement in pulmonary vascular mechanics and a reduction in right ventricular afterload. These improvements were a result of selective vasodilation of small pulmonary vessels and more efficient blood flow through the pulmonary vascular bed (improved transpulmonary vascular efficiency). The right ventricular total power output diminished during the inhalation of nitric oxide, indicating a reduction in right ventricular energy requirements. The net result of nitric oxide administration was an increase in right ventricular efficiency. CONCLUSION: These data suggest that nitric oxide may be beneficial to the failing right ventricle by improving pulmonary vascular mechanics and right ventricular efficiency.

Liquid ventilation improves pulmonary function and cardiac output in a neonatal swine model of cardiopulmonary bypass.

OBJECTIVE: Neonatal and infant cardiopulmonary bypass results in multiorgan system dysfunction. Organ protective strategies have traditionally been directed at the myocardium and brain while neglecting the sometimes severe injury to the lungs. We hypothesized that liquid ventilation would improve pulmonary function and cardiac output in neonates after cardiopulmonary bypass. METHODS: Twenty neonatal swine were randomized to receive cardiopulmonary bypass with or without liquid ventilation. In the liquid-ventilated group, a single dose of perflubron was administered before bypass. The control group was conventionally ventilated. Each animal was placed on nonpulsatile, hypothermic bypass. Low-flow cardiopulmonary bypass was performed for 60 minutes. The flow rate was returned to 125 ml/kg per minute, and after warming to 37 degrees C, the animals were removed from bypass. Hemodynamic and ventilatory data were obtained after bypass to assess the effects of liquid ventilation. RESULTS: Without liquid ventilation, cardiopulmonary bypass resulted in a significant decrease in cardiac output, oxygen delivery, and static pulmonary compliance compared with prebypass values. Input pulmonary resistance and characteristic impedance increased in these control animals. At 30, 60, and 90 minutes after bypass, the animals receiving liquid ventilation showed significantly increased cardiac output and static compliance and significantly decreased input pulmonary resistance and characteristic impedance compared with control animals not receiving liquid ventilation. CONCLUSIONS: Liquid ventilation improved pulmonary function after neonatal cardiopulmonary bypass while increasing cardiac output. The morbidity associated with cardiopulmonary bypass may be significantly reduced if the adverse pulmonary sequelae of bypass can be diminished. Liquid ventilation may become an important technique to protect the lungs from the deleterious effects of cardiopulmonary bypass.

Intraoperative perfusion contrast echocardiography. Initial experience during coronary artery bypass grafting.

Intraoperative evaluation of the effectiveness of myocardial revascularization has been limited by an inability to assess regional myocardial perfusion. Microbubbles of sonicated diatrizoate sodium and diatrizoate meglumine (Renografin) have been an effective echocardiographic contrast agent and have been employed clinically during cardiac catheterization. This recent development in contrast-enhanced two-dimensional echocardiography permits real-time imaging of transmural myocardial blood flow but has not been evaluated in the operating room. This study represents the initial surgical application of this directed technique and was designed to evaluate the safety and efficacy of intraoperative perfusion contrast echocardiography in assessing the results of coronary artery bypass grafting. Twenty men with significant coronary artery disease ranging in age from 49 to 73 years were studied. Direct contrast agent injection into completed saphenous vein bypass grafts caused the myocardium supplied by each graft to be well delineated and provided a tomographic view of contrast distribution. The enhanced region was well correlated with the size and distribution of the native vessel. Rapid contrast washout (less than 20 seconds) indicated satisfactory regional perfusion. Contrast echocardiography prolonged the operation less than 10 minutes and did not result in any perioperative complications.

In acute lung injury, inhaled nitric oxide improves ventilation-perfusion matching, pulmonary vascular mechanics, and transpulmonary vascular efficiency.

Acute respiratory distress syndrome continues to be associated with significant morbidity and mortality related to ventilation-perfusion mismatch, pulmonary hypertension, and right ventricular failure. It has been suggested that inhaled nitric oxide, which is a selective pulmonary vasodilator, may be effective in the treatment of acute respiratory distress syndrome; however, the effects of nitric oxide on cardiopulmonary interactions are poorly understood. We therefore developed a model of acute lung injury that mimics the clinical syndrome of acute respiratory distress syndrome. In our model, inhaled nitric oxide significantly reduced pulmonary artery pressure, pulmonary vascular resistance, and pulmonary vascular impedance. In addition, inhaled nitric oxide improved transpulmonary vascular efficiency and ventilation-perfusion matching, which resulted in increased arterial oxygen tension. Although arterial oxygen tension increased, oxygen delivery did not improve significantly. These data suggest that by improving ventilation-perfusion matching and arterial oxygen tension while lowering pulmonary vascular resistance and impedance, nitric oxide may be beneficial in patients with acute respiratory distress syndrome. However, additional measures to enhance cardiac performance may be required.

Improved tolerance of the pediatric myocardium to brain death.

The occurrence of brain death has been shown to significantly diminish left ventricular function in the adult porcine model. This study examined whether the pediatric myocardium is as sensitive as the adult myocardium to the detrimental effects of brain death in the porcine model. Left ventricular intracavitary pressure and major and minor axis epicardial dimensions were measured in eleven 1-month old pigs (7.5 to 10 kg) during a vena caval occlusion. Brain death was induced in six pigs by acutely ligating the brachiocephalic and left subclavian arteries. The remaining five pigs served as controls. Data were then collected every hour for 6 hours. The plot of the stroke work versus the end diastolic volume, called the preload recruitable stroke work relationship, was determined from the measured pressure and calculated intracavitary volume data. The slope of this linear relationship is an index of contractility, and the x intercept (Vo) is an index of diastolic mechanics. At each hour after instrumentation two vena caval occlusions were performed, and the mean slope of the preload recruitable stroke work line was calculated as a percentage of the baseline slope in both the brain-dead and control group. The mean values from the brain-dead pigs were 118%, 138%, 126%, 154%, 123%, and 87% of the baseline value for the 6 hours after brain death. The mean control values were 128%, 117%, 133%, 123%, 114%, and 111% of baseline for the 6 hours after instrumentation alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary hemodynamics and blood flow characteristics in chronic pulmonary hypertension.

BACKGROUND: Lung transplantation is now an acceptable form of therapy for pulmonary hypertension, but controversy remains regarding the most appropriate surgical procedure. In this study, the changes in pulmonary vascular mechanics occurring in the setting of pulmonary hypertension were investigated using an adult canine model of monocrotaline pyrrole-induced pulmonary hypertension. METHODS: Animals underwent pulmonary artery catheterization to measure right heart pressures before and 8 weeks after injection of either 3 mg/kg of monocrotaline pyrrole (n = 8) or placebo (n = 8). Eight weeks after injection, hearts underwent instrumentation with an ultrasonic flow probe and micromanometers. Harmonic derivation of functional data was achieved with Fourier analysis. RESULTS: Significant increases in mean pulmonary artery pressure and pulmonary vascular resistance were observed after monocrotaline pyrrole injection. There was no significant difference in pulmonary blood flow. However, significant increases in input resistance and right ventricular hydraulic power with significant decreases in transpulmonary efficiency were observed. CONCLUSIONS: Pulmonary hypertension causes significant alterations in pulmonary hemodynamics. Pulmonary blood flow is maintained by a significant increase in total power but with a significant decrease in transpulmonary efficiency. This adult canine model of pulmonary hypertension provides a useful means by which to evaluate surgical options of lung transplantation for improving pulmonary hemodynamics in the setting of chronic pulmonary hypertension.

Effects of internal mammary artery dissection on phrenic nerve perfusion and function.

The effects of left internal mammary artery (LIMA) dissection and distal division on phrenic nerve perfusion and function were examined in an adult swine model. Phrenic nerve perfusion was determined by left atrial injection of radioactively labeled microspheres. Phrenic nerve function was determined by measuring nerve and diaphragm potentials evoked by bilateral phrenic nerve stimulation. In the first group of animals (n = 9), the LIMA was dissected with ligation of all its branches. Left phrenic nerve perfusion and function decreased after LIMA dissection in every animal studied, whereas only minimal changes were observed on the right. Sixty minutes after LIMA dissection, left phrenic nerve mean perfusion decreased 71%. Left phrenic nerve and left diaphragm mean action potential amplitudes decreased 54% and 80%, respectively. In the second group of animals (n = 4), the LIMA dissection was performed without division of the pericardiacophrenic artery, a small proximal branch of the internal mammary artery that supplies the phrenic nerve. Sixty minutes after LIMA dissection, left phrenic nerve perfusion had decreased by 21% from control values, with a corresponding decrease in left phrenic nerve and diaphragm mean action potential amplitudes of 19% and 23%, respectively. These results indicate that LIMA dissection with division of all its branches in this model is associated with a significant impairment in left phrenic nerve perfusion and function and suggests a causal relationship. These results may also explain the apparent increased phrenic nerve cold sensitivity and increased incidence of phrenic nerve dysfunction associated with LIMA grafting.(ABSTRACT TRUNCATED AT 250 WORDS)

Influences of ultrasonic machine settings, transducer frequency and placement of region of interest on the measurement of integrated backscatter and cyclic variation.

Integrated backscatter and its cyclic variation are potentially important parameters to discriminate normal from diseased myocardium. Cyclic variation of integrated backscatter is expected to be independent of machine settings. Backscatter images of swine hearts were taken using a two-dimensional backscatter system while acoustic power was varied at different time gain control (TGC) settings. Cyclic variation was measured in vivo with various acoustic power and TGC settings using different transducer frequencies. Three different regions were analyzed. For any given TGC setting, the relationship between acoustic power and integrated backscatter in vitro was linear only over a narrow range. In vivo, cyclic variation was present at all regions studied in both long- and short-axis views. However, lower acoustic power (< 15 dB) and TGC (< 20 dB), or excessive settings of acoustic power (> 35 dB) and TGC (> 50 dB), produced minimal cyclic variation. Appropriate acoustic power (20-35 dB) and TGC (30-50 dB) produced larger and more consistent cyclic, variation at the posterior region of the left ventricle. These data indicate that each region has specific, appropriate machine settings to maximize the magnitude of cyclic variation.

The resection of orbicularis oculi muscle from the upper eyelid in experimental surgery on the monkey.

The purpose of this study was to determine the maximum amount of orbicularis oculi muscle that may safely be resected from the upper eyelid without causing functional abnormalities. Measured amounts of that muscle were surgically excised from both upper eyelids in six cynomolgus monkeys. All the eyelids were photographed and videotaped at progressively increased intervals to permit the evaluation of wound healing, scarring, and function. Our preliminary results revealed that the excision of preseptal and partial supraorbital orbicularis oculi muscle, preseptal and complete supraorbital muscle, or pretarsal muscle only did not result in lagophthalmos. Complete resection of pretarsal, preseptal, and supraorbital orbicularis oculi did result in lagophthalmos but caused no corneal injury. The orbicularis oculi muscle in the cynomolgus monkey is similar to that in humans, but it is not yet clear whether our findings in the monkey are applicable in humans. A determination of the maximum amount of orbicularis oculi muscle that can safely be excised in humans would enable plastic surgeons to better understand and develop techniques for eyelid reconstruction and blepharoplasty.

Factors predictive of adolescents' intentions to use birth control pills, condoms, and birth control pills in combination with condoms.

Using the Theory of Planned Behaviour (Ajzen, 1988) as a conceptual framework, 705 secondary school students were surveyed to identify their intentions to use birth control pills, condoms, and birth control pills in combination with condoms. Hierarchical multiple regression revealed that the theory explained between 23.5% and 45.8% of the variance in intentions. Variables external to the model such as past use, age, and ethnicity exhibited some independent effects. Attitudes were consistently predictive of intentions to use condoms, pills, and condoms in combination with pills for both male and female students. However, there were differences by gender in the degree to which subjective norms and perceived behavioural control predicted intentions. The findings suggest that programs should focus on: creation of positive attitudes regarding birth control pills and condoms; targeting important social influences, particularly regarding males' use of condoms; and developing strategies to increase students' control over the use of condoms.

Computer-assisted modeling of blood-flow: theoretical evidence for the existence of optimal flow wave patterns.

The purpose of this study was to model blood-flow waveforms in order to examine the relationship between various waveform shapes and input impedance spectra. Twenty distinct single cardiac cycle flow waveforms having the same mean flow and heart rate were created based on clinical and published observations. The "best" waveform was one with a steep flow upstroke, a high peak flow value, swift deceleration following peak flow, and flow reversal during diastole. Each flow waveform was paired with 20 computer-generated pressure waveforms to calculate input impedance spectra by discrete Fourier transformation. "Favorable" flow waveforms were associated consistently with a lower characteristic impedance (average of 4th-10th harmonics, Zav) irrespective of the shape or magnitude of the input pressure wave. Zav corresponds to the degree of compliance of the vascular bed and could be expected to be lower under favorable outflow conditions and in non-diseased vessels. In conclusion, this study provides theoretical evidence for the existence of optimal flow wave patterns and supports the notion of flow waveform assessment for diagnostic purposes.

Revision arthroscopic partial meniscectomy of the knee. A retrospective review.

The aim in this study was to find out if there were any revision operations in patients who underwent an arthroscopic partial meniscectomy and we attempted to identify the factor(s) that may be associated with the need for that revision. We reviewed 1,603 patients who underwent an arthroscopic partial meniscectomy, and 16 cases of revision were identified (rate 1%). Nine factors were analysed: age, sex, affected knee, affected meniscus, private or National Health Service (NHS) patient, symptoms prior to the most recent meniscectomy, type of tear, history of re-injury and the progression of Outerbridge changes to the articular surfaces. There was a significant risk for a revision meniscectomy in patients with horizontal/partial thickness tears compared to flap tears. No additional factor analysed was significantly associated with a revision procedure.

Adolescent females' attitudes, subjective norms, perceived behavioral control, and intentions to use latex condoms.

Guided by I. Ajzen's (1991) theory of planned behavior, the authors of this descriptive correlational study explored adolescent females' attitudes, subjective norms (social pressure), perceived behavioral control, and intentions with regard to latex condom use. An elicitation study was initially conducted (n = 16) to ascertain salient beliefs related to condom use. These beliefs were then used to develop a questionnaire administered during the main study to 60 sexually active adolescent females attending a sexually transmitted disease clinic. Global attitudes, subjective norms, and perceived behavioral control predicted 50% of the variance of intentions to use condoms. Perceived behavioral control contributed the highest proportion of variance in the equation for both global and belief-based measures in stepwise regression analyses. Implications for community health practice, research, and theory are reported.

Four primary malignant neoplasms in a single patient.

A 60-year-old Caucasian male, with a previous history of a 10-year occupational exposure to ionizing radiation, chemical carcinogens, and a long history of tobacco and alcohol abuse, developed synchronous squamous cell carcinoma of the floor of the mouth and adenocarcinoma of the lung. Four years later, squamous cell carcinoma of the larynx followed by squamous cell carcinoma of the tongue were diagnosed. In this case report, we suggest that increased exposure to multiple carcinogenic factors may result in an increased incidence of both synchronous and metachronous primary malignant neoplasms.

One-stage arm-preserving shoulder resection with latissimus dorsi flap for basal cell carcinoma.

A 60-year-old man was found to have a large invasive basal cell carcinoma involving the skin and surrounding bones of the shoulder joint. The Tikhor-Linberg procedure, a technique for preserving the arm in a shoulder resection, was combined with a latissimus dorsi muscle flap reconstruction in one stage to achieve a satisfactory functional result.

Importance of the kidney in the correction of chloride-depletion alkalosis in the rat.

Correction of chloride-depletion alkalosis (CDA) may involve renal as well as extrarenal mechanisms. To determine the relative contribution of these mechanisms in a rat model of CDA produced by peritoneal dialysis (PD), we studied six groups of anesthetized Sprague-Dawley rats after PD. Groups II-IV and IIa were subjected to functional bilateral nephrectomy, and groups I and Ia were sham-operated. Groups I, Ia, II, and IIa were infused with isotonic fluid containing 70 mM Cl- and 40 mM HCO3-; the infusate in group III was 140 mM Cl- and in group IV, 70 mM neutral PO4 was substituted for Cl-. Groups I and Ia were infused at 0.5 ml . h-1 X 100 g body wt-1 and groups II, IIa, III, and IV at 0.25 ml . h-1 X 100 g-1. After 3 h of infusion, early partial correction with reciprocal changes in plasma Cl (+6.1 +/- 1.9 mmHg) and total CO2 (-6.0 +/- 0.8 meq/liter) occurred (P less than 0.01) only in group I. Hypokalemia (3.1 +/- 0.1 meq/liter) also occurred only in group I. The responses of groups Ia and IIa studied at 5 h were similar to those of groups I and II. These data suggest that the kidney, and not extrarenal mechanisms, is primarily responsible for the correction of CDA during infusion of chloride.

Pulmonary hemodynamic consequences of ECG-synchronized ventilation.

The pulmonary hemodynamic consequences of ECG-synchronized jet ventilation were studied in an acute closed chest swine model (n = 11). Eight jet timing protocols were compared to conventional mechanical ventilation. Hearts were paced atrially at 120 beats per minute, and analog measurements of pulmonary arterial flow and pulmonary arterial, tracheal, pleural, left atrial, and femoral arterial pressure were digitized in real time at 200 Hz. Fourier analysis of pulmonary artery pressure and flow waveforms was employed to calculate mean and oscillatory right ventricular hydraulic power and pulmonary vascular input impedance. Measurements were taken at 0, 5, and 10 cm H2O of positive end-expiratory pressure (PEEP) during conventional respiration and synchronized ventilation modes. No difference was found in mean pulmonary pressure and flow between conventional and synchronized ventilation at any level of PEEP, regardless of the timing of the jet pulse relative to the cardiac cycle. A significant difference in mean tracheal pressure between conventional and jet ventilation could be found only in the absence of PEEP (3.8 +/- 0.5 vs 2.5 +/- 0.3 mm Hg, P < 0.05). In the absence of PEEP, total hydraulic power was significantly less with respect to conventional ventilation when the jet pulse trailed the QRS complex by 90 and 135 degrees. A significant decrease in the ratio of oscillatory-to-mean power versus conventional respiration was found when jet ventilation lagged the QRS by 135 degrees (0.115 +/- 0.015 vs 0.147 +/- 0.013). These differences did not persist when PEEP was added. Moreover, no significant difference in hemodynamic variables was found when the various jet timing protocols were compared to each other.(ABSTRACT TRUNCATED AT 250 WORDS)