Metronidazole kinetics and bioavailability in patients undergoing gastrointestinal surgery.

Kinetics and bioavailability of metronidazole were studied in 17 patients admitted in our emergency care unit for gastrointestinal surgery. All were treated with intravenous metronidazole (500 mg three times a day) before, during, and for 4 days after surgery. Seven of the patients continued the intravenous regimen and seven were switched to oral therapy with the same dose and dosing interval for 4 additional days. Kinetic evaluations were performed at steady state on days 4 and 8. The main unexpected result was a consistent 51% increase in AUC with no increase in elimination t 1/2 when intravenous was changed to oral therapy. This change was accompanied by an upward 75% shift in the trough metronidazole plasma concentrations. There was no change when patients remained on intravenous metronidazole. Reduction of clearance on oral treatment appears to be the most likely explanation.

Early anuria prevention in human kidney transplantation. Advantage of fluid load under pulmonary arterial pressure monitoring during surgical period.

In human kidney transplantation, a high blood flow established through the graft immediately upon clamp release is usually associated with immediate satisfactory renal function. One hundred consecutive kidney transplant patients were thus provided with a large volume of fluid during surgery. To avoid pulmonary edema, fluid load was given under mean pulmonary arterial pressure (PAP) monitoring, and controlled ventilation was maintained during the early postoperative period. Whether initial PAP value was within normal range or elevated, all patients required an equivalent fluid load to reach the best hemodynamic condition upon clamp removal. The mean intraoperative fluid load consisted of 2406 +/- 968 ml of water with 22.8 +/- 9.4 g of sodium chloride, 5.9 +/- 1.8 units of albumin, and 2.6 +/- 1.8 units of packed red blood cells. Immediately before clamp release patients were given furosemide and mannitol. During the postoperative period, i.v. infusions consisted of water and sodium chloride (6 g/liter) to match urine output, provided that diuresis was equal to or above 400 ml/hr. If diuresis remained or decreased below this level, diuresis replacement was associated with PAP-controlled infusion of saline, albumin, and red blood cells if needed. Furosemide was eventually given if diuresis did not increase above 400 ml/hr with fluid loading. With this protocol a good early diuresis was established in 95% of the cases. Ten patients required dialysis before the 5th postoperative day, one of them because of fluid overload and anuria. Concurrently, a decreased mortality rate and an increased graft survival rate were observed.

Comparative arterial antithrombotic activity of clopidogrel and acetyl salicylic acid in the pig.

We investigated the comparative antithrombotic properties of clopidogrel, an analogue of ticlopidine, and aspirin, using the Folts' model on femoral arteries in 22 pigs. On each animal, clopidogrel or aspirin were used to treat the thrombotic process on the left femoral artery and to prevent this process on the right femoral artery. Sequentially: an injury and stenosis were carried out on the left femoral artery; the thrombotic process was monitored with a Doppler during a 30-min observation period for cyclic flow reductions or permanent cessation of flow; after the first cyclic flow reduction occurred, clopidogrel (5 mg kg-1) or aspirin (2.5, 5, 100 mg kg-1) were injected intravenously; if cyclic flow reductions were abolished, epinephrine (0.4 micrograms kg-1 min-1) was injected to try to restore cyclic flow reductions and/or permanent cessation of flow; then injury and stenosis were applied on the right femoral artery. Before and after injection of clopidogrel or aspirin, ear immersion bleeding times and ex-vivo platelet aggregation were performed. Clopidogrel (n = 7) abolished cyclic flow reductions were efficiently prevented, even for two injuries. Basal bleeding time (5 min 28) was lengthened (> 15 min, 30 min after clopidogrel and remained prolonged even after 24 h). ADP-induced platelet aggregation was inhibited (more than 78%). Comparatively, aspirin had a moderate and no dose-dependent effect. Aspirin 2.5 mg kg-1 (n = 6) abolished cyclic flow reductions in 2 animals, CFR reoccurred spontaneously in one animal and epinephrine restored it in a second animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Aprotinin could promote arterial thrombosis in pigs: a prospective randomized, blind study.

Haemostatic properties of aprotinin could be associated with an increased risk of thrombosis. A randomized, blinded study was conducted to consider the potential thrombogenicity of aprotinin, using the Folts' model on femoral arteries in 12 pigs. The flow variations were measured by a pulsed Doppler in anaesthetised animals. Ear immersion bleeding time was performed. During the first part of the study, a stenosis was performed successively on both femoral arteries, each for a period of 30 min, without prior injury, to assess the integrity of the vessel, and to check that the arteries did not develop cyclic flow reductions (CFR), permanent cessation of flow (PCF) or partial thrombosis, when a stenosis is applied. Then the clamp was released and a bolus of placebo (saline), or aprotinin (4 millions KIU, followed by a continuous infusion of 1 million KIU.h-1), was administered. At the end of the bolus, the second part of the study began. Stenosis was applied to the arteries. If CRF, PCF, or partial thrombosis were observed without prior injury then the infused drug (aprotinin or saline) was considered a prothrombotic drug, and the opposite artery was studied. For each animal, right and left femoral artery segments were fixed and studied (morphologic study). Eighteen arteries were studied. In the aprotinin group, 6 arteries out of 8 developed an unexpected thrombosis, as compared with only 2 out of 10 arteries in the control group (p = 0.02). The morphologic study confirmed the occurrence of thrombosis in 4 out of 7 arteries in the aprotinin group, as compared with only 1 out of 9 in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Prehospital autotransfusion in life-threatening hemothorax.

Eighteen patients with life-threatening traumatic hemothorax received prehospital autotransfusion using a simple new device. During transfer to the hospital, they received 3.9 +/- 0.5 L of colloid fluid and 4.1 +/- 0.6 L of autotransfused blood, without anticoagulation. Hemorrhagic blood was not coagulable, had a hematocrit of 20 +/- 4 percent, few platelets, and low fibrinogen levels. Five patients died from irreversible hemorrhagic shock. Thirteen patients were alive upon admission to the hospital, underwent emergency surgery, and were discharged alive. During autotransfusion, hematocrit decreased from 24 +/- 3 to 19 +/- 3 percent, and systolic arterial pressure increased from 78 +/- 11 to 88 +/- 12 mm Hg. Upon admission to the hospital, platelet count was 90,800 +/- 21,400/cu mm, prothrombin time 48 +/- 3 percent, partial thromboplastin time 197 +/- 18 percent, plasma free hemoglobin levels 21 +/- 7 mg/100 ml, and serum potassium levels 3.6 +/- 0.5 mmol/L. No serious complication could be related to autotransfusion considered to be crucial to patients' survival. The preliminary results of this study suggest that autotransfusion might be developed in the prehospital setting since it appears simple and safe, and represents the only hope of survival for patients with life-threatening hemothorax.

Myocardial contusion in patients with blunt chest trauma as evaluated by thallium 201 myocardial scintigraphy.

Fifty five patients suffering from blunt chest trauma were studied to assess the diagnosis of myocardial contusion using thallium 201 myocardial scintigraphy. Thirty-eight patients had consistent scintigraphic defects and were considered to have a myocardial contusion. All patients with scintigraphic defects had paroxysmal arrhythmias and/or ECG abnormalities. Of 38 patients, 32 had localized ST-T segment abnormalities; 29, ST-T segment abnormalities suggesting involvement of the same cardiac area as scintigraphic defects; 21, echocardiographic abnormalities. Sixteen patients had segmental hypokinesia involving the same cardiac area as the scintigraphic defects. Fifteen patients had clinical signs suggestive of myocardial contusion and scintigraphic defects. Almost 70 percent of patients with blunt chest trauma had scintigraphic defects related to areas of myocardial contusion. When thallium 201 myocardial scintigraphy directly showed myocardial lesion, two-dimensional echocardiography and standard ECG detected related functional consequences of cardiac trauma.

High-frequency jet ventilation vs continuous positive airway pressure for postoperative respiratory support.

In ten patients after recovery from general anesthesia for major vascular surgery, we compared continuous positive airway pressure (CPAP) and high-frequency jet ventilation (HFJV) at the same fractional concentration of oxygen in the inspired gas, both being superimposed on spontaneous breathing. The HFJV was delivered by a ventilator ( Acutronic VS-600) through the lateral lumen of a three-lumen endotracheal tube. Mean airway pressure was increased (3, 8, and 11 mm Hg) by adjusting the driving pressure during HFJV and by the setting of the expiratory valve during CPAP. During HFJV, the frequency (10 Hz) and inspiratory-expiratory ratio (0.25) were kept constant. Control values were measured when patients breathed spontaneously without positive end-expiratory pressure. Cardiac output and transmural filling pressures remained unchanged throughout the study. Neither the arterial oxygen pressure (PaO2) nor intrapulmonary shunt (Qs/Qt) changed significantly during CPAP. The 20- to 30-percent increase in PaO2 and the 5- to 10-percent decrease in Qs/Qt during HFJV when compared to control reflected a slightly but significantly (p less than 0.05) better oxygenation. The increase in arterial carbon dioxide tension was significantly greater during CPAP than during HFJV.

Hemodynamic consequences of increasing mean airway pressure during high-frequency jet ventilation.

Six critically ill patients with acute respiratory failure were ventilated using high-frequency jet ventilation (HFJV)-frequency 100.min-1, driving pressure 35 psi, 1.8 mm inside diameter injector cannula. Hemodynamic measurements using radial artery and Swan-Ganz catheters, esophageal pressure (EP), and mean airway pressure (Paw) were measured at four different I:E ratios: 0.25, 0.43, 0.67 and 1.0. Static respiratory compliance, using the super syringe method, was measured during intermittent positive pressure ventilation (IPPV) and during HFJV. The results suggested that decreased venous return, increased right ventricular afterload, and decreased PaCO2 accounted for the decrease in cardiac index observed during HFJV using elevated I:E ratios. These variations, related to marked increases in intrathoracic pressures, are very similar to those observed during conventional ventilation with PEEP.

Early diagnosis of traumatic thoracic aortic rupture by transesophageal echocardiography.

Traumatic aorta rupture survival depends on early diagnosis requiring aortography. Aortography is the "gold standard" method, but it is time-consuming and may be dangerous in trauma patients with multiple organ injuries. Transesophageal echocardiography is a noninvasive technology that can be performed at the bedside. We report two cases in which transesophageal echocardiography enabled us to make the early diagnosis of thoracic descending aorta rupture.

Three mixed venous saturation catheters in patients with circulatory shock and respiratory failure.

Thirty-one critically ill patients with acute respiratory failure and circulatory shock were divided into three groups. Group 1 included 11 patients with an inserted mixed venous saturation (SvO2) catheter using three-reference wavelengths and characterized by one transmitting and one detecting fiberoptic filament (Oximetrix opticath catheter); group 2 included eight patients with an inserted SvO2 catheter using two-reference wavelengths and characterized by one transmitting and one detecting fiberoptic filament; (Edwards sat-one catheter); group 3 included 12 patients with an inserted SvO2 catheter using two-reference wavelengths and characterized by one transmitting and two detecting fiberoptic filaments. Once calibration procedures were performed, SvO2 measured by the catheter and by an hemoximeter OSM 3 (reference value) were compared following each therapeutic intervention. Over a period of 1.5 to 6 hours during which the hematocrit value remained unchanged, 119 measurements were obtained in group 1, 91 in group 2 and 181 in group 3. The dispersion of SvO2 values was much more pronounced with the two-reference wavelength systems using either one or two detecting fiber optic filaments, and the correlation coefficient was significantly higher with the three-reference wavelength system (r = 0.970 for the Oximetrix catheter vs r = 0.855 for the Edwards catheter and r = 0.826 for the Spectramed catheter, p less than 0.001). After 24 hours, the spontaneous drifts in the two-reference wavelength systems, using either one or two detecting fiber optic filaments (expressed as the SvO2 value measured by the catheter minus the reference SvO2 value) were significantly higher than the spontaneous drift in the three-reference wavelength system (9.3 +/- 7 percent for the Edwards catheter and +/- 6 +/- 4.1 percent for the Spectramed catheter vs 3.3 +/- 3.1 percent for the Oximetrix catheter, p less than 0.05). This study shows that a three-wavelength system is more accurate than a two-wavelength system for measuring acute changes in SvO2. The addition of a second detecting fiber optic filament does not seem to improve the accuracy of the system when SvO2 changes occur in conditions of stable hematocrit.

Diagnosis of traumatic mediastinal hematoma with transesophageal echocardiography.

In patients with blunt chest trauma, early diagnosis of mediastinal hematoma is important, because it could be associated with thoracic vessel injury. Mediastinal hematoma is generally evoked because of a widened mediastinum on chest radiograph, but radiologic diagnosis may lead to excessive angiography being performed. Transesophageal echocardiography (TEE) provides accurate views of the mediastinum and can be rapidly performed at the bedside. Thus, we conducted a prospective study to define TEE signs of mediastinal hematoma. TEE was performed in 22 thoracic trauma patients (trauma group) and in 20 brain-dead patients without thoracic trauma (control group). The positive diagnosis of mediastinal hematoma was made using thoracic surgery or computed tomographic scan. The specificity of TEE was 75 percent and sensitivity was 100 percent. In the trauma group, there was only one false positive but angiography discovered a traumatic aneurysm of the proximal right subclavian artery. No false negative was noted. We described three different TEE signs of mediastinal hematoma: (1) an increased distance between the probe and the aortic wall; (2) a double contour of the aortic wall; and (3) visualization of the ultrasound signal between the aortic wall and the visceral pleura. The distance between the esophageal probe and the aortic wall was the most accurate sign because it could be easily obtained; the threshold value for this distance was 3 mm. TEE appears to be an accurate method to diagnose traumatic mediastinal hematoma.

Diazepam does not improve the mechanical performance of rat cardiac papillary muscle exposed to chloroquine in vitro.

Diazepam has been reported to decrease the cardiac toxicity of chloroquine but the precise mechanism involved remains unknown. Left ventricular papillary muscles from adult Wistar rats were exposed to 10(-4) M chloroquine and assigned to three groups: group I (n = 10) exposed to chloroquine alone; group II (n = 8) exposed to chloroquine and 10(-5) M diazepam; group III (n = 8) exposed to chloroquine and 10(-4) M diazepam. The main mechanical parameters measured were: maximum unloaded shortening velocity (Vmax), maximum lengthening velocity (maxVr), active force normalized per cross-sectional area (AF/s), contraction-relaxation coupling under low load (R1), load sensitivity of relaxation (Isot.A/Isom.A), and peak power output (Emax) determined from Hill's equation of the force-velocity curve. Data are expressed as mean percent of control values +/- SD, for groups I, II, III respectively. No differences between groups I, II, and III were noted for Vmax (87 +/- 13, 82 +/- 9, 86 +/- 7), maxVr (47 +/- 6, 48 +/- 11, 52 +/- 11), AF/s (87 +/- 16, 91 +/- 10, 83 +/- 11), Isot. A/Isom. A (113 +/- 9, 108 +/- 3, 109 +/- 7), or Emax (75 +/- 10, 81 +/- 12, 72 +/- 16). Chloroquine was shown to be a negative inotropic agent since it decreased Vmax, AF/s and Emax, but diazepam did not restore the intrinsic mechanical performance of rat cardiac papillary muscle exposed to chloroquine, therefore 1) the protective cardiovascular effects of diazepam in chloroquine poisoning are not related to an improvement in intrinsic cardiac mechanical properties; 2) inotropic agents are therefore necessary in combination with diazepam for the treatment of severe chloroquine poisoning.

Continuous positive airway pressure (CPAP) vs. intermittent mandatory pressure release ventilation (IMPRV) in patients with acute respiratory failure.

Intermittent Mandatory Pressure Release Ventilation (IMPRV) is a positive pressure spontaneous breathing ventilatory mode in which airway pressure is released intermittently and synchronously with patient's spontaneous expiration in order to provide ventilatory assistance. Eight critically ill patients free of any factor known to alter chest wall mechanics (group 1) and 8 critically ill patients whose spontaneous respiratory activity was markedly altered by a flail chest, or by a C5 quadraplegia and/or by the administration of opioids (group 2) were studied prospectively. CPAP and IMPRV were administered to each patient in a random order during a 1 h period using a CESAR ventilator. Gas flow, tidal volume, tracheal pressure, esophageal pressure, end-expiratory lung volume and hemodynamic parameters were measured. In group 1 patients, the ventilatory assistance provided by IMPRV was associated with a significant decrease in spontaneous tidal volume whereas all other respiratory parameters remained unchanged. In group 2 patients, IMPRV increased minute ventilation from 8.0 +/- 2.61/min to 12.2 +/- 1.81/min (p less than 0.05), decreased PaCO2 from 46 +/- 7.3 mmHg to 38 +/- 6.8 mmHg (p less than 0.05) and reduced respiratory frequency from 21 +/- 10 bpm to 14 +/- 5.7 bpm (p less than 0.07). These results show that IMPRV provides significant ventilatory assistance to patients with mild acute respiratory failure either by decreasing patient's contribution to minute ventilation or by increasing alveolar ventilation in presence of respiratory depression of central or peripheral origin.

Plasma ionized calcium in brain-dead patients.

BACKGROUND: The mechanism of brain death-induced myocardial dysfunction remains debatable. Hypocalcemia is known to induce reversible myocardial dysfunction. However, the incidence of hypocalcemia and its effect on myocardial function during brain death is unknown. METHODS: In 54 consecutive brain-dead patients, we measured plasma total and ionized calcium concentrations, QT and corrected QT intervals, and left ventricular ejection fraction area (LVEFa), using transesophageal echocardiography. RESULTS: 49 (91%) of brain-dead patients had a decrease in total plasma total calcium concentration but only 19 (35%) had a decrease in plasma ionized calcium. Corrected total plasma calcium failed to predict ionized calcium concentration and QT intervals were not significantly different in normo and hypocalcemic patients. The LVEFa was not significantly different between normo and hypocalcemic patients (53 +/- 13 versus 50 +/- 20%), and no correlation was found between LVEFa and ionized calcium (R = 0.02, NS). Hypocalcemic patients required greater doses of dopamine (8.2 +/- 5.2 versus 5.0 +/- 3.4 micrograms.kg-.min-1, p < 0.02) to maintain arterial pressure. Hypocalcemia was associated with a higher volume loading and a lower plasma protide concentration which reflected hemodilution. CONCLUSION: A decrease in plasma ionized calcium is not frequent, rarely severe, and probably not the main mechanism of myocardial dysfunction in brain-dead patients. Hypocalcemic patients required higher doses of dopamine, suggesting a decrease in systemic resistance. Only direct measurement of ionized calcium can assess plasma calcium ion status in brain-dead patients.

Histologic aspects of pulmonary barotrauma in critically ill patients with acute respiratory failure.

OBJECTIVE: To describe histologically pulmonary barotrauma in mechanically ventilated patients with severe acute respiratory failure. DESIGN: Assessment of histologic pulmonary barotrauma. SETTING: A 14-bed surgical intensive care unit (SICU) PATIENTS: The lungs of 30 young critically ill patients (mean age 34 +/- 10 years) were histologically examined in the immediate post-mortem period. None of them were suspected of pre-existing emphysema. MEASUREMENTS AND RESULTS: Clinical events and ventilatory settings used during mechanical ventilation were compared with lung histology. Airspace enlargement, defined as the presence of either alveolar overdistension in aerated lung areas or intraparenchymal pseudocysts in nonaerated lung areas, was found in 26 of the 30 lungs examined (86%). Patients with severe airspace enlargement (2.6-40 mm internal diameter) had a significantly greater incidence of pneumothorax (8 versus 2, p < 0.05), were ventilated using higher peak airway pressures (56 +/- 18 cmH2O versus 44 +/- 10 cmH2O, p < 0.05) and tidal volumes (12 +/- 3 ml/kg versus 9 +/- 2 ml/kg, p < 0.05), were exposed significantly longer to toxic levels of oxygen (8.6 +/- 9.4 days versus 1.9 +/- 2 days at FIO2 > 0.6, p < 0.05) and lost more weight (6.3 +/- 9.2 kg versus 0.75 +/- 5.8 kg, p < 0.05) than patients with mild airspace enlargement (1-2.5 mm internal diameter). CONCLUSION: Underlying histologic lesions responsible for clinical lung barotrauma consist of pleural cysts, bronchiolar dilatation, alveolar overdistension and intraprenchymal pseudocysts. Mechanical ventilation appears to be an aggravating factor, particularly when high peak airway pressures and large tidal volumes are delivered by the ventilator.

Prevention of gram negative nosocomial bronchopneumonia by intratracheal colistin in critically ill patients. Histologic and bacteriologic study.

OBJECTIVE: To evaluate the efficiency of intratracheal colistin in preventing nosocomial bronchopneumonia (BPN) in the critically ill. DESIGN: Study evaluating the clinical incidence of nosocomial BPN in 2 groups of critically ill patients who receive or did not receive intratracheal colistin. BPN was assessed clinically in survivors and histologically in non-survivors. SETTING: A 14-bed surgical intensive care unit. PATIENTS: 598 consecutive critically ill patients were studied during a prospective non-randomized study over a 40-month period. INTERVENTIONS: 251 patients--31 non-survivors and 220 survivors--did not receive intratracheal colistin and 347-42 non-survivors and 305 survivors--received intratracheal colistin for a 2-week period (1,600,000 units per 24 h). MEASUREMENTS AND RESULTS: The incidence of nosocomial BPN was evaluated clinically in survivors, using repeated protected minibronchoalveolar lavages, and histologically in non-survivors via an immediate postmortem pneumonectomy (histologic and semi-quantitative bacteriologic analysis of one lung). The clinical incidence of nosocomial BPN was of 37% in coli (-) survivors and of 27% in coli (+) survivors (p < 0.01). This result was histologically confirmed in non-survivors, where the incidence of histologic BPN was of 61% in coli (-) patients and of 36% in coli (+) patients (p < 0.001). Emergence of BPN due to colistin-resistant micro-organisms was not observed. Because colistin was successful in preventing Gram-negative BPN and did not change the absolute number of Gram-positive BPN, the proportion of BPN caused by staphylococcus species was higher in group coli (+) patients (33% vs 16%). Mortality was not significantly influenced by the administration of colistin. CONCLUSION: This study suggests that the administration of intratracheal colistin during a 2-week period significantly reduces the incidence of Gram-negative BPN without creating an increasing number of BPN due to colistin-resistant micro-organisms.

Inhaled nitric oxide in acute respiratory failure: dose-response curves.

OBJECTIVE: To determine the dose-response curve of inhaled nitric oxide (NO) in terms of pulmonary vasodilation and improvement in PaO2 in adults with severe acute respiratory failure. DESIGN: Prospective randomized study. SETTING: A 14-bed ICU in a teaching hospital. PATIENTS: 6 critically ill patients with severe acute respiratory failure (lung injury severity score > or = 2.5) and pulmonary hypertension. INTERVENTIONS: 8 concentrations of inhaled NO were administered at random: 100, 400, 700, 1000, 1300, 1600, 1900 and 5000 parts per billion (ppb). Control measurements were performed before NO inhalation and after the last concentration administered. After an NO exposure of 15-20 min, hemodynamic parameters obtained from a fiberoptic Swan-Ganz catheter, blood gases, methemoglobin blood concentrations and intratracheal NO and nitrogen dioxide (NO2) concentrations, continuously monitored using a bedside chemiluminescence apparatus, were recorded on a Gould ES 1000 recorder. In 2 patients end-tidal CO2 was also recorded. RESULTS: The administration of 100-2000 ppb of inhaled NO induced: i) a dose-dependent decrease in pulmonary artery pressure and in pulmonary vascular resistance (maximum decrease--25%); ii) a dose-dependent increase in PaO2 via a dose-dependent reduction in pulmonary shunt; iii) a slight but significant decrease in PaCO2 via a reduction in alveolar dead space; iv) a dose-dependent increase in mixed venous oxygen saturation (SVO2). Systemic hemodynamic variables and methemoglobin blood concentrations did not change. Maximum NO2 concentrations never exceeded 165 ppb. In 2 patients, 91% and 74% of the pulmonary vasodilation was obtained for inhaled NO concentrations of 100 ppb. CONCLUSION: In hypoxemic patients with pulmonary hypertension and severe acute respiratory failure, therapeutic inhaled NO concentrations are in the range 100-2000 ppb. The risk of toxicity related to NO inhalation is therefore markedly reduced. Continuous SVO2 monitoring appears useful at the bedside for determining optimum therapeutic inhaled NO concentrations in a given patient.

Effects of high-frequency jet ventilation on arterial baroreflex regulation of heart rate.

Fifteen anesthetized mechanically ventilated patients recovering from multiple trauma were studied to compare the effects of high-frequency jet ventilation (HFJV) and continuous positive-pressure ventilation (CPPV) on arterial baroreflex regulation of heart rate. Systolic arterial pressure and right atrial pressure were measured using indwelling catheters. Electrocardiogram (ECG) and mean airway pressure were continuously monitored. Lung volumes were measured using two linear differential transformers mounted on thoracic and abdominal belts. Baroreflex testing was performed by sequential intravenous bolus injections of phenylephrine (200 micrograms) and nitroglycerin (200 micrograms) to raise or lower systolic arterial pressure by 20-30 Torr. Baroreflex regulation of heart rate was expressed as the slope of the regression line between R-R interval of the ECG and systolic arterial pressure. In each mode of ventilation the ventilatory settings were chosen to control mean airway pressure and arterial PCO2 (PaCO2). In HFJV a tidal volume of 159 +/- 61 ml was administered at a frequency of 320 +/- 104 breaths/min, whereas in CPPV a tidal volume of 702 +/- 201 ml was administered at a frequency of 13 +/- 2 breaths/min. Control values of systolic arterial pressure, R-R interval, mean pulmonary volume above apneic functional residual capacity, end-expiratory pulmonary volume, right atrial pressure, mean airway pressure, PaCO2, pH, PaO2, and temperature before injection of phenylephrine or nitroglycerin were comparable in HFJV and CPPV. Baroreflex regulation of heart rate after nitroglycerin injection was significantly higher in HFJV (4.1 +/- 2.8 ms/Torr) than in CPPV (1.96 +/- 1.23 ms/Torr).(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory effects of the Jarvik-7 artificial heart.

In five anesthetized patients with a Jarvik-7 artificial heart, pulmonary volume displacements generated by cardiogenic oscillations were measured using an indirect spirometric method. Consequences on gas exchange were also evaluated during a 15-min period of apnea by use of a tracheal insufflation of pure O2 at a constant flow rate of 20 l/min. The Jarvik-7 artificial heart generated a mean pulmonary volume displacement of 105 +/- 29 (SD) ml/heart beat. After 15 min of apnea, arterial PCO2 (PaCO2) significantly increased from 29 +/- 5 to 47 +/- 6 (SD) Torr. PaCO2 increased by 0.8 Torr/min from the 5th to the 15th min of apnea. Mean arterial PO2, mean pulmonary shunt, mean O2 consumption, and mean metabolic production of CO2 did not change significantly during the apnea period. Because cardiac output was kept constant during the study, O2 transport was adequately maintained throughout the apnea period. In patient 1, where the period of apnea was continued for 60 min, PaCO2 progressively increased until the 45th min and then remained stable at 61 Torr during the last 15 min of apnea. This "plateau" corresponded to an alveolar ventilation of 3,907 ml/min, representing 69% of the alveolar ventilation calculated during conventional mechanical ventilation. In conclusion, the Jarvik-7 artificial heart provides a potent respiratory support through the cardiogenic oscillations it generates.

Central venous pressure and pulmonary wedge pressure. A comparative study in anesthetized surgical patients.

To determine the reliability of central venous pressure (CVP) as a guide to fluid therapy during an operation, repeated and simultaneous CVP and pulmonary wedge pressure (PWP) measurements were made with a Swan-Ganz catheter in 13 relatively elderly patients without obvious cardiac or respiratory disease- Overall correlation between CVP and PWP was highly significant (P less than .001); there was, however, an important variation of the correlation for each patient. For values of CVP greater than or equal to 8 mm Hg, the correlation was not significant. The disparity between right and left ventricular filling pressures was confirmed by the relationship between serial changes in CVP and PWP. These data strongly suggest that in relatively elderly patients undergoing surgery without evidence of cardiac or respiratory disease, CVP may be misleading index for appreciating PWP.