Roberta C. Kahn

Clinical experience with high frequency jet ventilation.

: High frequency jet ventilation (HFJV) has been used in recent years in some forms of respiratory failure, where the presence of barotrauma limited the application of high peak inspiratory pressure. In the present report, the authors describe the clinical experience with 17 patients, who could not be supported with conventional mechanical support and were placed on HFJV. Rates of 100 breath/min, inspiratory/expiratory ratio of 1:2 and cannula size of 1.06--1.62 mm (18--14) gauge were used. Driving pressure required to maintain a PaCO2 of 40--45 torr was 14--45 psig; however, except in 2 patients who developed hemorrhagic tracheitis with subtotal obstruction of both mainstem bronchi, a driving pressure higher than 27 psig was never required, even when PEEP up to 32 cm H2O was used. Of 17 patients treated, 8 survived. In all cases, alveolar ventilation could be maintained within the desired range with high frequency ventilation, even in those patients who eventually died; mechanical support never provided better oxygenation or alveolar ventilation than high frequency ventilation. Hemodynamic function was essentially unchanged with high frequency ventilation; indeed, in three cases, inotropic support with dopamine could be discontinued after initiation of high frequency ventilation.

Dopamine administration in oliguria and oliguric renal failure.

Oliguric renal failure significantly worsens the prognosis of many critical illnesses, particularly in patients with respiratory failure. In 52 patients, a continuous infusion of dopamine, 1.5–2.5 μg/kgμmin, was administered when creatinine clearance (Cer) fell below 40 ml/ min and urinary output was less than 1 ml/kgμh despite normal intravascular volume. In 18 patients, a continuous infusion of furosemide (3–5 mg/kgμday) was also administered. Daily, two 3-h collections of urine and blood specimens were obtained to determine Ccr, osmolar clearance (Cosm), free water clearance (CHO2) and excreted fraction of filtered sodium (FENa); one collection was made during dopamine infusion and one while the infusion was suspended. Cardiac output and pulmonary venous admixture were also measured. The authors obtained 199 urine collections in 52 patients; considering the aggregate patient population, urinary output increased by 42.3% (30.2 ± 3.45 (SEM) ml/h), on dopamine infusion. Cosm, FENa, and Ccr were also higher on dopamine. CH2O and hemodynamic variables were not altered by dopamine infusion.When patients were stratified on the basis of mechanical veritilatory support, Ccr and furosemide administration, dopamine infusion essentially caused the same changes in the variables studied as described for the aggregate patient population. Diuresis and sodium excretion increased significantly on dopamine even in those patients receiving furosemide infusion.The authors conclude that fluid and osmolar load can be eliminated more effectively in critically ill patients with continuous infusion of 1.5–2.5 μg/kgμmin of dopamine.

Hemodynamic oxygen transport and 2,3-diphosphoglycerate changes after transfusion of patients in acute respiratory failure

The goals of management of patients with respiratory failure include improving arterial oxygenation with PEEP and red cell transfusion to maintain oxygen carrying capacity, both of which contribute to improving tissue oxygen delivery. However, standard CPD-stored blood is rapidly depleted of 2,3 diphosphoglycerate (2,3 DPG) and ATP, with resultant inadequacy of the red cell oxygen transport function. In 15 patients requiring mechanical ventilation with PEEP whose initial Hct≤35%, we studied the effect of transfusion of 7 ml/kg of CPD-stored packed red blood cells on hemodynamic and oxygen delivery variables, pulmonary venous admixture (QA/QT), and erythrocytic P50, 2,3 DPG and ATP concentrations. Hemodynamics were not significantly altered by transfusion. 2,3 DPG decreased significantly from 14.5±1.1 to 13.1±1.5 mcmol/g Hb (mean±SD, p<0.05). There was no significant change in P50 or ATP. QA/QT rose significantly, from 20.1±7.8 to 28.9±12.3% (mean±SD, p<0.02). In our patients, an increase in arterial oxygen content obtained by transfusion was not followed by any associated decrease in cardiac work, as implied by solution of equations for oxygen delivery and oxygen consumption. The rise in QA/QT is undesirable in patients requiring PEEP, since it complicates management of their mechanical ventilatory support.

Massive Blood Replacement: Correlation of Ionized Calcium, Citrate, and Hydrogen Ion Concentration

Fifty-three patients were studied intraoperatively during massive transfusion of CPD-preserved blood and fresh frozen plasma (FFP). Baseline concentrations of total calcium (Ca), ionized calcium (Ca2+), albumin, total protein, and hydrogen ion concentration [H+] were measured prior to transfusion, at intervals during transfusion of 2500 ml of blood, and at the end of transfusion. Systemic arterial pressure (BPI, central venous pressure (CVP) and/or pulmonary artery wedge pressure (PAW), and corrected Q-T intervals on electrocardiographic tracings were measured at the time blood samples were obtained. Ca2+ decreased from 2.07 ± 0.03 mEq/L at baseline to 1.52 ± 0.05 mEq/L (p < 0.01) during transfusion at peak rates of 33 ± 3.2 ml/kg/hr. Following completion of transfusion, Ca2+ was significantly higher than at peak rates of transfusion, but still below baseline. Serum citrate levels rose from a baseline value of 1.87 ± 0.17 mg/dl to 6.30 ± 0.49 mg/dl (p < 0.01) at peak rate of transfusion and fell to 4.76 ± 0.48 immediately upon completion of transfusion (p < 0.011. The changes in Ca2+ and serum citrate levels showed a strong statistical correlation with each other. [H+] increased, but not significantly, at peak rates of infusion; after completion of transfusion, [H+] was significantly lower than during peak rates of transfusion. Ca levels were 4.10 ± 0.05 mEq/L at baseline, 3.90 ± 0.05 mEq/L at peak rates of infusion, and 3.89 ± 0.06 mEq/L after transfusion was completed. Albumin levels at the same sampling intervals were 3.60 ± 0.07, 3.71 ± 0.06, 3.87 ± 0.07 g/dl, respectively. Total protein levels were 5.95 ± 0.07, 5.67 ± 0.07, and 5.88 ± 0.09 g/dl, respectively. Corrected Q-T intervals were significantly prolonged at peak rates of transfusion and upon completion of transfusion. Correlation between changes in Ca2+ and corrected Q-T intervals was statistically significant. However, hemodynamic variables remained stable throughout the period of observation.Massive transfusions depressed Ca2+ due to administration of citrate, but this was only transient. Ca2+ rapidly returned to normal levels as citrate was redistributed and metabolized. The changes in Ca2+ were without hemodynamic significance. Clinically significant metabolic acidosis due to transfusion was not observed. We conclude, therefore, that as long as circulating volume is maintaines, as determined by measurement of CVP or PAW, calcium salts need to be administered during blood replacement, either empirically on the basis of rate or volume or transfusion, or on the basis of changes in samples indicate the development of metabolic acidosis.

Technical aspects and clinical implications of high frequency jet ventilation with a solenoid valve

High frequency jet ventilation (HFJV) is an incompletely studied technique of mechanical respiratory support. The authors have built a ventilator based on a solenoid valve, that allows independent selection of respiratory rate and inspiratory/expiratory ratio. The ventilator can be synchronized to the heart rate. Humidification is provided by warm saline dripped in front of the injector nozzle, so that the jet stream itself acts as a nebulizer. Tube diameter, length, and deformability are fundamental determinants of inspiratory flow rate and wave form. Cannula kinking and inadequate humidification were the most significant sources of complications.

Calcium chloride administration in normocalcemic critically ill patients.

Ten normocalcemic critically ill patients who had experienced a decrease in cardiac index ≥0.5 liter/min/m2 after incremental changes of PEEP received 7 mg/kg of CaCl2 as a slow iv bolus, followed by an infusion of 20 mg/kg CaCl2 over 60 min. Hemodynamic pressures and flow, oxygen uptake and transport, and blood chemistry variables were determined over a 120-min period. The results indicated that: (1) hemodynamic variables were not affected except for left ventricular stroke work index and mean blood pressure, which increased slightly; (2) both serum calcium and ionized calcium concentrations increased significantly, sometimes to dangerous levels; (3) colloid osmotic pressure and hemoglobin levels decreased slightly but consistently. In conclusion, CaCl2 administration failed to improve hemodynamic function depressed by PEEP. If CaCl2 can play a relevant role in the management of cardiovascular depression, further identification of appropriate doses and patients is necessary.

Long-term infusion of sodium thiopental: hemodynamic and respiratory effects.

To establish the possible advantages of ultrashort acting barbiturates administered in continuous infusion as the only sedative agent for mechanically ventilated patients, sodium thiopental was given to 30 subjects for periods ranging from 2–14 days. Plasma levels were maintained at approximately 15 μg/ml, using both laboratory determinations and clinical judgment. This technique proved effective for patients requiring either controlled ventilation or intermittent mandatory ventilation. None of the hemodynamic and respiratory variables studied was significantly altered during the infusion, with the exception of decreased heart rates. In view of these results, the technique is considered both expedient and safe for prolonged sedation of patients requiring ventilatory support.

Insertion of difficult nasogastric tubes through a nasoesophageally placed endotracheal tube

A technique is described to facilitate the insertion of NG tubes with the aid of nasoesophageal insertion of an endotracheal tube. This technique is particularly useful in comatose and anesthetized patients. The equipment utilized is easily assembled and readily available. We have found this method to be easier and more successful than those previously described.

Unusual complications during pulmonary artery catheterization

Two unusual complications, encountered during pulmonary artery catheterization, are described. In both cases the catheter had been introduced percuta-neously with the Seldinger technique. Inadvertent entry of the right pleural space occurred in one case in which the catheter had been inserted into the internal jugular vein through a low cervical approach. The second complication was separation of the shaft of the introducer from the hub, with consequent risk of embolization. Possible means of preventing and treating these complications are discussed.

Rapid volume expansion in patients with interstitial lung diseases.

Rapid administration of intravascular volume expanders is often necessary during anesthesia. Significant controversy still exists on the relative values of different volume expanders. Fifteen hypoxemic patients (Pa02 <70 torr on room air) were studied preoperatively. They were randomized into three groups. One group received 1.5 ml/kg of 25% salt-poor human albumin, a second group, 7 ml/kg of fresh frozen plasma; a third group, 7 ml/kg of 0.9% NaCI in water (normal saline). The infusions were given intravenously and completed in 20 minutes. Changes in hemodynamic pressures and flows, blood chemistries, and oxygen uptake and transport variables were studied. It was concluded that fresh frozen plasma afforded the greatest increase in cardiac output and oxygen availability with the least increase in left ventricular stroke work. Colloid osmotic pressure was more significantly increased by fresh frozen plasma than by salt-poor human albumin. Normal saline caused both a decrease in oxygen availability and colloid osmotic pressure. Pulmonary venous admixture increased to some extent in all patients receiving fresh frozen plasma or normal saline. In three patients, this increase was very marked and accompanied by severe arterial hypoxemia.