Richard C. Dennis

Myocardial depression during sepsis

The cardiac response to volume loading was evaluated in fifty severely septic patients. After a rapid infusion of albumin or whole blood the cardiac index (CI) and left ventricular stroke work index (LVSWI) were recorded as the pulmonary arterial wedge pressure (PAWP) increased. Initial values of PAWP, CI, and LVSWI were similar in both the nineteen surviving and thirty-one nonsurviving patients. Surviving patients, however, demonstrated greater increases in CI and LVSWI as PAWP rose. Nearly half of both patient groups developed decreases in CI and LVSWI as the PAWP continued to increase. These downslopes occurred at relatively low PAWP and are taken as evidence of an abnormality of myocardial function in both survivors and nonsurvivors. The lower upslope of the performance curves in nonsurvivors indicates myocardial depression or a negative inotropic effect. Cardiac ischemia, acute respiratory failure, and high affinity red cells were found to diminish the cardiac response to volume loading, whereas hepatic and renal failure were associated with a good CI and LVSWI response.

Guidelines on admission and discharge for adult intermediate care units

OBJECTIVE To present guidelines for writing admission and discharge policies for adult intermediate care units. DATA SOURCES Opinion of practitioners with experience and expertise in managing critical and intermediate care units. DATA SYNTHESIS Consensus was reached regarding the characteristics of patients best suited for management in an intermediate care unit, as supported by a literature review. CONCLUSION Criteria were developed that define patients who are optimal candidates for management in an intermediate care unit.

The safety and therapeutic effectiveness of human red cells stored at — 80°C for as long as 21 years

Human red cells frozen by various methods have been stored in the frozen state at —80°C for as long as 21 years. This report discusses: red cells frozen with 42 percent weight per volume (wt/vol) glycerol in an ionic medium in a polyvinylchloride (PVC) plastic bag using the Cohn method; red cells frozen with 45 percent wt/vol glycerol in a low ionic medium in a PVC plastic bag using the Huggins method; red cells frozen with 40 percent wt/vol glycerol in an ionic medium in a polyolefin plastic bag using the Meryman‐Hornblower method; and red cells frozen with 40 percent wt/vol glycerol in an ionic medium in a standard 600‐ml or an elongated 800‐ml PVC plastic primary collection bag with an adapter port using the Naval Blood Research Laboratory (NBRL) method. After frozen storage for as long as 21 years by the four methods described above, the thawed red cells were deglycerolized with 50 to 150 ml of 12 percent sodium chloride and 1.5 to 2.0 l of sodium chloride‐glucose or sodium chloride‐glucose‐phosphate solution. After washing and storage at 4°C for 24 hours, the red cells had a mean freeze‐thaw‐wash recovery value of 90 percent, a mean 24‐hour posttransfusion survival value of 85 percent, a mean index of therapeutic effectiveness of 75 percent, normal or slightly impaired oxygen transport function, and minimal hemolysis. When red cells frozen by the NBRL method in the standard 600‐ml or the elongated 800‐ml primary collection bag for as long as 5.7 years were stored after washing at 4°C for up to 3 days, these units had a mean freeze‐thaw‐wash recovery value of 90 percent, a mean 24‐hour posttransfusion survival value of 85 percent, a mean index of therapeutic effectiveness of 75 percent, normal or slightly impaired oxygen transport function, and minimal hemolysis. Cultures done after storage at 4°C for 1 week showed that the red cells remained sterile. The incidence of container breakage for red cells frozen in the standard 600‐ml or elongated 800‐ml primary collection bag was about 3 percent for units subjected to shipment and less than 1 percent for units that were not transported.

Freezing in the Primary Polyvinylchloride Plastic Collection Bag: A New System for Preparing and Freezing Nonrejuvenated and Rejuvenated Red Blood Cells

Red blood cells were stored at 4 C in the primary bag with an integrally attached empty transfer pack so that the red blood cells could be rejuvenated or not, as desired before glycerolization and freezing. The rejuvenation and glycerol solutions were added through ports in the system. After glycerolization, the red blood cells were concentrated by centrifugation to remove the supernatant glycerol before freezing with 40% w/v glycerol in the primary polyvinylchloride (PVC) plastic container at −80 C.

The efficacy of sequential compression devices in multiple trauma patients with severe head injury

Thirty-two multiple trauma patients with severe head injury and a Glasgow Coma Scale (GCS) score of 8 or less were prospectively studied to assess the occurrence of deep venous thrombosis (DVT) and pulmonary embolism (PE). All patients required mechanical ventilation. A sequential compression device (SCD) was used in 14 patients and 18 patients received no prophylaxis for thromboembolism. Bilateral lower extremity technetium venoscans and ventilation/perfusion (V/Q) lung scans were performed within 6 days of admission and every week for 1 month or until the patient developed DVT or PE or was discharged from the SICU. Deep venous thrombosis occurred in two patients (6%) at 16 and 28 days following trauma. Twenty-five patients had normal or low probability V/Q scans. Six had high probability V/Q scans confirmed by pulmonary arteriograms (PAGs) at 12.5 +/- 4 days. Clinical signs of PE were absent in all patients with a positive PAG. There were no differences in age, Injury Severity Score (ISS), GCS Score, APACHE II Score, or Trauma Score between the patients who developed DVT or PE and those who did not. A SCD was used in four of the eight patients with DVT or PE. All but one patient with DVT or PE underwent placement of a vena caval filter. Multiple trauma patients with severe head injury (GCS score < or = 8) are at high risk for thromboembolism. The available means of prevention and diagnosis of DVT or PE in multiple trauma patients with severe head injury are not entirely effective.

Limitations of the hematocrit level to assess the need for red blood cell transfusion in hypovolemic anemic patients

BACKGROUND:  The transfusion trigger that physicians use to determine whether a patient requires a red blood cell (RBC) transfusion is the peripheral venous hematocrit (Hct) value. Although this measurement is an indicator of the concentration of RBCs in the blood, it does not reveal the RBC volume, plasma volume, or total blood volume, nor does it give any indication of whether the patient is hypovolemic, normovolemic, or hypervolemic.

Transfusion of 2,3 DPG-Enriched Red Blood Cells to Improve Cardiac Function

Attempts were made to enhance oxygen availability in patients undergoing coronary artery bypass operations by transfusing red blood cells enriched in 2,3 diphosphoglycerate (2,3 DPG) to 150% of normal. In this study of 22 patients, 11 received red blood cells with high 2,3 DPG levels and 11 received red blood cells with 70% of normal 2,3 DPG levels (control). Immediately following cardiopulmonary bypass the 11 patients who received high 2,3 DPG red blood cells had a P50 value of 31.6 mm Hg; the value in control patients was 28.3 mm Hg (p less than 0.05). Oxygen consumption values were 135 and 106 ml/min/m2, respectively (p less than 0.05). Mixed venous oxygen tensions were similar in the two groups, but the arteriovenous content difference was higher in the high 2,3 DPG group (p less than 0.05). Cardiac indices increased significantly in response to a fluid load in the high 2,3 DPG group compared with controls at comparable filling pressures. We believe the improved myocardial performance in response to a fluid challenge is a result of increased oxygen availability.

Improved Oxygen Delivery to the Myocardium during Hypothermia by Perfusion with 2,3 DPG–Enriched Red Blood Cells

The oxygen affinity of red cells increases stepwise with temperature reductions below 37 degrees C. In vitro studies demonstrated that biochemically modified red cells with increased 2,3 diphosphoglycerate (2,3 DPG) (150% and 250% of normal) exhibited significantly less oxygen affinity at 24 degrees C than did unmodified cells. At 15 degrees C, significant attenuation of affinity was observed with 250%, but not 150%, of normal 2,3 DPG cells. Measurements made of isolated fibrillating dog hearts during perfusion at 24 degrees C alternately with unmodified (80% of normal 2,3 DPG) and modified (300% of normal 2,3 DPG) red cells demonstrated significantly greater oxygen consumption, higher coronary sinus partial pressures of oxygen and carbon dioxide, higher in vitro P50 values, and lower arterial and coronary sinus lactate levels during perfusion with modified as compared with unmodified cells. This evidence, indicating improved oxygen delivery to hypothermic dog hearts by red cells with 300% of normal 2,3 DPG activity, suggests that high 2,3 DPG cells might protect myocardial tissue in patients undergoing hypothermic cardiac operation.

Clinical applications of thermodilution cardiac output determinations

The pulmonary arterial catheter was shown to be safe and easily positioned in a group of 200 patients. Thermodilution cardiac output measurement was shown to be simple, rapid, and safe. The technic was as accurate as the simultaneously measured indocyanine green cardiac output, and more reproducible, particularly at high and low flows. The construction of myocardial performance curves during a fluid challenge is described. The value of these curves is guiding fluid, drug, and respirator therapy is illustrated by case presentations.

Effect of sample dilutions on arterial blood gas determinations

A study was undertaken to determine the blood gas effects of incompletely purging heparinized saline flush solution from an indwelling arterial catheter and pressure tubing. Hematocrit and blood gases were measured after withdrawing 0, 2, 4, 6, 8, and 10 ml of flush-blood solutions before sampling from a 20-ga radial artery catheter and 7-ft pressure tubing and stopcock. The pH and hematocrit were nearly unchanged between purging volumes of 8 and 10 ml. The PaO2 had a 2.4% error, while the PaCO2 had a 4.4% error. Because there is no standard arterial line setup, it is recommended that each ICU undertake a similar study to determine the optimal volume of aspirated flush-blood solution before blood gas sampling, in order to achieve accurate blood gas results and minimize blood waste.