Effect of endotoxin on portal hemodynamic in rats

AIM: To study the effects of endotoxin on portal hemodynamic of normal and noncirrhotic portal hypertensive rats. METHODS: Normal rats were intraperitoneally injected with 0.1, 0.25, 0.5, 1.0, 2.0, 4.0mg.kg(-1) of lipopolysaccharide(LPS) respectively, portal vein ligation(PVL) and intrahepatic portal occlusion (IPO) rats as well as sham-operated rats were treated with an intraperitoneal injection of 1.0mg.kg(-1) of LPS, the portal vein pressure(PVP), portal venous flow(PVF), inferior vena cava pressure(IVCP) and portal vein resistance(PVR) were detected 4 hours after injection. RESULTS: PVF of the 5 groups of rats accepting intraperitoneal injection of LPS were increased from 14.0 to 18.0, 22.2, 26.2, 34.8, 39.6, 38.8 mL.min(-1) 4 hours after injection of LPS(P【0.01). PVP of the 4 groups of rats accepting more than 0.1mg/kg.b.w of LPS was increased from 1.04 to 1.25, 1.50, 1.80, 1.95, 2.05 kPa(P【0.01). The increments of PVF and PVP were in a dose-dependent manner of LPS. PVR of the 5 groups of rats was decreased from 51 to 42,44,48,45,44,47 kPa.min.L(-1) (P【0.05) and no dose-dependent manner was observed. PVF of PVL, IPO and sham-operated rats increased from 22.6 to 32.8, 22.0 to 28.0, 14.0 to 34.8 mL.min(-1) (P【0.01), and PVP increased from 1.86 to 2.24, 1.74 to 1.95, 1.04 to 1.80 kPa(P【0.01), PVR decreased from 71 to 61, 67 to 61, 52 to 44 kPa.min.L(-1) after intraperitoneal injection of 1mg.kg(-1) of LPS. The increments of PVF and PVP of PVL and IPO rats were significantly less than the sham-operated rats(P【0.01), There was no significant difference between the amounts of PVR decreased in the two groups of PHT model rats and sham-operated rats(P】0.05) after intraperitoneal injection 1mg.kg(-1) of LPS. CONCLUSION: Endotoxin could prompt portal hypertension of the normal and noncirrhotic portal hypertensive rats by increasing portal blood flow mainly.

Distribution of ventilation and hemodynamic effects of different ventilatory patterns

OBJECTIVE: To compare the influence of cardiac-pulmonary function on clinical acute respiratory failure patients using Proportional assist ventilation (PAV), Pressure support ventilation (PSV) and intermittent positive pressure ventilation (IPPV). Here, we also describe some our experience with the clinical use of PAV. METHODS: Using the IPPV mode in ten acute respiratory failure patients, calculate Elastance (Ers) and Resistance (Rrs), then change to PSV, set inspiratory positive airway pressure (IPAP) according to IPPV, so that tidal volume (V(T)) is the same as that of IPPV. We then changed the mode into PAV and set the assist ratio according to PSV, so that V(T) and Ppeak were the same as that of PSV. Then we observed the changes of respiratory mechanics, blood gas levels and hemodynamics during ventilation. RESULTS: Compared with PSV and IPPV, peak pressure (Ppeak) of PAV was markedly lower while V(T) was similar; work of breathing of patient (WOBp), and work of breathing of ventilation (WOBv) were also lower; center vein pressure (CVP) and pulmonary capillary wedge pressure (PCWP) of PAV were markedly lower than that of IPPV while V(T) were similar. Compared with PSV, V(T), mean blood pressure (mBP) and cardiac output (CO) of PAV were higher. Mean pulmonary artery pressure (mPAP) and WOBp of PAV were lower while Ppeak was similar; the differences in WOBp were notable. CONCLUSIONS: For clinical acute respiratory failure patients, compared with PSV and IPPV, PAV has lower airway pressure, less WOBp and less influence on hemodynamics.

Evaluation of the relative risk of stroke in patients with hypertension using cerebrovascular hemodynamic accumulative score

The relative risk(RR)of stroke in patients with hypertension was evaluated by using synthetic index of cerebrovascular hemodynamics.A total of 7,371 patients with hypertension with ages i40 years were selected from a population-based cohort study of the risk factors for stroke.The data on the baseline investigation of risk factors,the determination of cerebrovascular hemodynamic parameters(CVHP),and stroke follow-up were analyzed.The RR of stroke in patients with hypertension was evaluated by CVHP scores.Univariate analysis indicated that hypertension,complicated by other risk factors,had significant statistical association with the onset of stroke.RRs for stroke when hypertension complicated with decrease of hemodynamic scores,heart disease,cigarette smoking and alcohol consumption were 4.93(95%CI,3.26–7.45),1.90(95%CI,1.36–2.66),1.99(95%CI,1.42–2.79)and 1.73(95%CI,1.19–2.53)respectively.In multivariate analysis,hemodynamic score,age,sex,cigarette smoking,family history of stroke and systolic blood pressure were selected by the Cox regression for inclusion in the final analysis.Among them,the RR of hemodynamic score was highest.The analysis of doseresponse relationships indicated that when the hemodynamic scores in patients with hypertension were lower than 75 points,the RR of stroke at 75,60,45,30 and 15 points were 2.85,4.43,4.54,5.40 and 9.88,respectively.The risk of stroke in patients with hypertension is closely asso ciated with hemodynamic impairment and the hemodynamic score may be used for quantitative evaluation of relative risks of stroke.

Pump models assessed by transesophageal echocardiography during cardiopulmonary resuscitation

OBJECTIVE: Transesophageal echocardiography was performed during closed-chest cardiopulmonary resuscitation (CPR) in in-hospital cardiac arrest to further explore the hemodynamic mechanism of CPR. METHODS: CPR attempts were performed according to advanced cardiovascular life support guidelines in 6 cases of in-hospital cardiac arrest. Multi-plane transesophageal echocardiography was carried out within 15 min of initiation of CPR. Throughout CPR, the motion of the mitral, tricuspid and aortic valves, the changes in the left ventricular cavity size and the thoracic aortic diameter were observed. Trans-mitral and trans-aortic Doppler files of blood flow were also documented. RESULTS: A closure of the mitral and tricuspid valves with simultaneous opening of the aortic valve occurred exclusively during chest compression, resulting in forward blood flow in the pulmonary and systemic circulation. Peak forward aortic flow at a velocity of 58.8 +/- 11.6 cm/s was recorded during the compression phase. Whereas, a closure of the aortic valve and rapid opening of the atrioventricular valves associated with ventricular filling during relaxation of chest compression was noted in all 6 patients. Peak forward mitral flow at a velocity of 60.6 +/- 20.0 cm/s was recorded during the release phase. Mitral regurgitation during the chest compression period was detected in 5 patients, reflecting a positive ventricular-to-atrial pressure gradient. A reduction in the left ventricular chamber and an increase in the thoracic aortic diameter during the compression phase was found in all patients, indicating that direct cardiac compression contributed to forward blood flow. CONCLUSION: These observations favor the cardiac pump theory as the predominant hemodynamic mechanism of forward blood flow during CPR in human beings.

Proportional assist ventilation: methodology and therapeutics on COPD patients compared with pressure support ventilation

OBJECTIVE: To investigate the impact of proportional assist ventilation (PAV) on tolerance and breathlessness in ventilated chronic obstructive pulmonary disease (COPD), and to describe the patient-ventilator interaction, hemodynamic state, breathing pattern and work of breath during PAV and pressure support ventilation (PSV). METHODS: Ten intubated COPD patients on weaning from mechanical ventilation were studied. Elastance and resistance were measured by both the inspiratory-hold technique during a brief period of volume control ventilation and runaway technique during PAV. Each assistance level of PAV (80%, 60% and 40%) and PSV was selected randomly. Patients' response, hemodynamics, blood gas and lung mechanics were monitored. RESULTS: Tidal volume and respiratory rate didn't change in a consistent manner as the level of assist was decreased (P > 0.05). With the level of assist increasing, peak inspiratory pressure was increasing significantly (P