Mechanical work on the lungs and work of breathing with positive end-expiratory pressure and continuous positive airway pressure.

The mechanical work on the lung required during spontaneous breathing with positive end-expiratory pressure (PEEP) was compared with different methods of continuous positive airway pressure (CPAP) in nine young healthy athletes (surfers) at levels of 5, 10, 15, and 20 cm H2O. At the level of 20 cm H2O, PEEP increased the mean total work per minute by 116 percent and the total work per liter by 121 percent. The percent increase rose linearly with the level of PEEP. In contrast, with methods of CPAP that maintained the airway pressure (Paw) constant, the total work per minute decreased by 45 per cent at a PEEP of 10 cm H2O and remained at this level with PEEP of 15 and 20 cm H2O. Use of PEEP did not increase the functional residual capacity (FRC) in these spontaneously breathing subjects. In contrast, CPAP resulted in a rise in FRC proportional to the level of CPAP. This suggests that CPAP must be applied in a manner that maintains Paw constant to provide optimal assistance to ventilation.

Selective use of ventilator therapy in flail chest injury.

We have prospectively treated 36 patients with flail chest using a treatment protocol for limited use of mechanical ventilation. Age of the patients ranged from 6 months to 83 years. Patients were divided into three groups dependent upon their clinical presentation and need for respiratory support: Group I patients had severe pulmonary dysfunction-tachypnea, dyspnea, arterial PO2 less than or equal to 60 torr, arterial PCO2 greater than or equal to 50 torr or shunt fraction greater than or equal to 25%. Group II patients had no pulmonary dysfunction but did require temporary respirator support for an associated injury. Group III patients had no pulmonary dysfunction. Thirteen patients were assigned to Group I. They required respiratory support for an average of 10.5 days; 11 of the 13 had complications, and there were two deaths in this group resulting from a combination of respiratory failure and myocardial infarction. Seven patients were assigned to Group II. six patients were extubated immediately postoperatively; one patient with a head injury was hyperventilated for 48 hours to reduce intracranial pressure and then extubated. Sixteen patients were assigned to Group III. Fifteen required no ventilatory support. One 83-year-old man developed pneumonia and was mechanically ventilated for 31 days. Early effective pain control and chest physiotherapy were critical to success and were used in all patients. Increase in respiratory rate, fall in tidal volume or vital capacity, and increased pain were used as criteria for administration of analgesia. Nonventilatory therapy of flail chest reduces morbidity, mortality, and hospital cost.

Crystalloid vs. colloid resuscitation: is one better? A randomized clinical study.

The effects of hemodynamic resuscitation with protein-containing or balanced salt solution were studied prospectively in 29 patients undergoing abdominal aortic surgery. Blood loss was replaced with packed red cells and extracellular volume with either Ringer's Lactate (RL) or 5% albumin in Ringer's lactate (ALB). Fluids were given to maintain the pulmonary capillary wedge pressure (PCWP) equal to or within 5 torr above preoperative (PO) levels, the cardiac output (CO) equal to or greater than preoperative values, and the urine output at least 50 ml/hr. Serum colloid osmotic pressure (COP), CO, PCWP, the gradient between COP and PCWP (COP-PCWP), and intrapulmonary shunt (Qs/Qt) were measured PO, intraoperatively (IO), and daily for 3 days. The measured variables were similar PO in both groups. Operation time, estimated blood loss, and transfusions were similar. Total fluids received for resuscitation (day of operation) was 11.3 +/- 0.8 liters (RL) and 6.2 +/- 0.4 liters (ALB). Fluid balance at the end of resuscitation was 8.4 +/- 0.8 liters (RL) and 3.4 +/- 0.5 liters (ALB). Maximum decrease in COP was 40% (P less than 0.001) in the RL group and was insignificant in the ALB group. The COP-PCWP decreased from 11 +/- 1 to 2 +/- 1 in RL (P less than 0.001) and insignificantly in ALB. Qs/Qt increased slightly in both groups following operation but was not different between groups. Fluid balance, total fluid infused, sodium balance, total sodium infused, COP, or COP-PCWP did not significantly correlate with Qs/Qt. Two patients in the ALB group experienced pulmonary edema associated with normal COPs and elevated PCWPs. There were no cases of pulmonary edema associated with low COPs and normal PCWPs in the crystalloid group. These data seriously question the necessity to maintain COP by using protein-containing solutions during acute hemodynamic resuscitation. When titrated to physiological end points, even large volumes of balanced salt solutions are tolerated well.

Hypertonic sodium lactate versus lactated ringer's solution for intravenous fluid therapy in operations on the abdominal aorta.

Fifty-eight patients who were to undergo aortic reconstruction were prospectively randomized into two groups to compare the effects of perioperative fluid replacement with isotonic and hypertonic crystalloid solutions. Blood loss was replaced with packed red blood cells, and additional fluid was given as either Ringer's lactate solution (RL, 130 mEq sodium/L, 274 mOsm/L) or a hypertonic balanced salt solution (HSL, 250 mEq sodium/L, 514 mOsm/L). Fluid was administered to maintain the cardiac filling pressure within 3 torr of the preoperative level and the cardiac output (CO) at or above the preoperative level. The groups were similar with respect to age, preexisting disease, duration of operation, and operative blood loss. During the operation, the RL group required 9.5 +/- 0.8 L of fluid, whereas the HSL group required 4.5 +/- 0.3 L (P less than 0.001). Pulmonary, cardiac, and renal functions were adequately maintained in both groups. There were no significant differences between the groups with regard to CO, urine output, or creatinine clearance during the operation and early postoperative period. Postoperatively, the intrapulmonary shunt was 20 +/- 1% in the RL group and it was 16 +/- 1% in the HSL group (P less than 0.05). The amount of sodium infused and the cumulative sodium balance at the completion of the study period were similar in both groups. Serum sodium and osmolarity were significantly greater in the HSL group (P less than 0.001), reaching a maximum of 151 +/- 1 mEq/L and 305 +/- 2 mOsm/L, respectively. Two patients in the HSL group had a persistent elevation in serum osmolarity (greater than 320 mOsm/L) during operation, for which they received RL for the balance of the resuscitation. There were no complications that could be attributed to the hypertonicity of the solution. HSL is effective for resuscitation of patients with extracellular fluid deficit and is safe provided that the serum sodium and osmolarity are monitored during periods of large volume administration.

Central venous pressure or pulmonary capillary wedge pressure as the determinant of fluid replacement in aortic surgery.

Both central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) have been used as guides to fluid replacement in patients undergoing abdominal aortic surgery. To test the hypothesis that changes in PCWP (deltaPCWP) may be reliably estimated from changes in CVP (deltaCVP), 55 patients had simultaneous measurements (302 paired observations) of CVP and PCWP, as well as of cardiac output, before and during operation. The correlation between deltaCVP and deltaPCWP was high (r = 0.716, P less than 0.001). The estimated slope for the linear regression was 0.88. The standard error of the estimate was +/- 3.75 torr, making the prediction of deltaPCWP from deltaCVP accurate only to within 7.5 torr. There were five patients who each had a low and failing CVP accompanied by a stable cardiac output and a rising PCWP; for them, a decision to administer fluid based on the CVP might have resulted in pulmonary edema. Although deltaCVP accurately predicted direction and magnitude of deltaPCWP in the majority of patients (90%), there was a small group in whom there was no substitute for direct measurement of PCWP.

Impact of a trauma system on outcome of severely injured patients.

We examined the impact of a trauma system on the survival of patients with a Trauma Score of 8 or less. We compared the observed survival with that predicted using a method that calculates the probability of survival (Ps) based on age, physiologic score, and anatomic severity of injury. Of 3394 patients triaged to trauma centers in a 12-month period, 283 (8.3%) had a Trauma Score of 8 or less. Sufficient data were available in 189 patients with blunt trauma to make the survival comparison. The Ps was 18%; the observed survival was 29%. Of 60 patients with penetrating trauma and complete data, the Ps was 8%; the observed survival was 20%. We attribute the improved survival to the integration of prehospital and hospital care and expeditious surgery.

Mechanics of ventilation with positive end-expiratory pressure.

The effect of graded increments in positive end-expiratory pressure (PEEP) on arterial oxygen partial pressure (PaO2) and shunt fraction (Qs/QT), oxygen delivery, and respiratory mechanics and work required to ventilate 8 critically ill patients is reported. The work required to ventilate the patients increases markedly with the application and progressive increase in the level of PEEP. However, improvement in lung mechanics lowers the net work of ventilating the lungs. At 20 cm H2O PEEP, the mean value for the work of ventilation in this group of patients is twice the mean value without PEEP. The increase in work of ventilation with PEEP is critical in the use of PEEP when patients are breathing spontaneously with or without intermittent mandatory ventilation.

The management of flail chest. A comparison of ventilatory and nonventilatory treatment.

Retrospective analysis of forty-two consecutive patients with flail chest injuries admitted to the Trauma Research Unit of the Naval Regional Medical Center, San Deigo from June 1972 to July 1975 compared ventilatory and nonventilatory management. The actual need for ventilatory support in these patients was determined by analyzing their records for evidence of significant pulmonary dysfunction. This allowed division of patients into three groups: "appropriately" ventilated; "inappropriately" ventilated; and nonventilated. Admission PO2 in the "appropriately" ventilated patients was significantly lower than in the other two groups because the former were admitted with respiratory distress and hypoxemia. Significantly more complications occurred in the ventilated groups than in the nonventilated. Treatment-associated complications were more frequent in the ventilated groups. Because of these findings, we belive that mechanical ventilation should be used in the treatment of flail chest injuries only for significant pulmonary dysfunction and not for the purpose of stabilizing the chest wall. If respiratory support is required, it should be discontinued when normal gas exchange has been restored.

Peritoneal lavage in children with blunt abdominal trauma.

Quantitative peritoneal lavage was performed in 52 children with blunt abdominal trauma to determine the presence of intraabdominal injuries. A strongly positive lavage was 100% accurate in diagnosing an intraabdominal injury requiring operation. A negative lavage demonstrated absence of a significant intraperitoneal injury with 100% accuracy. A weakly positive lavage was not diagnostic and required additional evaluation including intravenous pyelography echography, and arteriography. Diagnosis and treatment was prompt, and in 20 of 21 cases, operation was performed within 4 hr. Peritoneal lavage was found to be safe and much more accurate than physical examination in diagnosing significant intraabdominal injury.

Interpretation of alveolar-arterial oxygen tension difference.

In this study, an assessment is given of errors resulting from the use of the alveolar-arterial oxygen difference determined on both room air and 100% oxygen in estimating changes in total shunt fraction of 41 patients hospitalized with long bone fractures. In 113 studies, changes in alveolar-arterial oxygen difference in 29 patients were in the opposite direction to changes in shunt fraction. Based upon these studies, changes of less than 45 millimeters in the arterial oxygen tension determined with a patient breathing 100% oxygen are not reliable indicators of direction of change in shunt fraction. In 126 studies, the shunt fraction determined from arterial and mixed venous oxygen contents in 71 patients was greater when determined on 100% oxygen than when determined on room air, a possible indication of the induction of alveolar or small airway collapse. The errors in estimation of shunt fraction due to assuming a value for arteriovenous oxygen content difference become larger as total shunt fraction increases; in particular, use of the alveolar-arterial oxygen difference as a guide to serial changes in pulmonary dysfunction can be particularly misleading when the alveolar-arterial oxygen tension difference is so large that the arterial hemoglobin is less than fully saturated on 100% oxygen. Use of mixed venous samples was found necessary, in these instances, to avoid large errors in estimation of total shunt fraction.

Whole blood versus packed-cell transfusions: a physiologic comparison.

Twenty-eight patients undergoing major aortic reconstructions were prospectively randomized into two groups to compare blood replacement with either whole blood (WB) or packed cells (PRBC). Cardiac index (CI), pulmonary capillary wedge pressure (PCWP), intrapulmonary shunt (Qs/Qt), serum colloid osmotic pressure (COP), platelets, prothrombin time (PT), partial thromboplastin time (PTT), and fibrinogen were measured before operation, during operation, and for three days after operation. The postoperative CI increased significantly in both groups from preoperative value, but was not significantly different between the groups. In the PRBC group, there was a significant decrease in postoperative COP and COP-PCWP gradient from preoperative value. This did not occur in the WB group. There was no significant difference between groups in postoperative Qs/Qt, nor was there any evidence of clinical or radiographic pulmonary dysfunction. Both groups manifested a prolongation of the PT and PTT immediately after operation, but these returned to normal without intervention by the first day after operation. It is felt that blood replacement with reconstituted packed red cells can provide effective volume replacement without producing coagulopathy. The decreases observed in COP and COP-PCWP gradient do not result in physiologic or clinical evidence of significant pulmonary dysfunction.

Early extubation versus prophylactic ventilation in the high risk patient: a comparison of postoperative management in the prevention of respiratory complications.

To evaluate whether prophylactic ventilation during the early postoperative period diminishes pulmonary complications, 35 high risk, elderly patients undergoing major, elective abdominal aortic reconstruction were prospectively randomized into either an early extubation group or a prophylactic ventilation group. The 17 patients assigned to the prophylactic ventilation group received mechanical ventilation by assist/control mode until 8 a.m. of the first postoperative day. The 17 patients assigned to the early extubation group were extubated after the operation as soon as they could maintain a pH of 7.35, with a spontaneous respiratory rate of less than 30. Preoperative measurements of functional residual capacity, intrapulmonary shunt, and oxygen delivery were compared to similar measurements during the initial two postoperative days. There were no significant differences between the groups with respect to age, length of operation, duration of anesthesia, operative blood loss, intraoperative fluid administration, or number of intraoperative transfusions. Patients in the prophylactic ventilation group were ventilated for an average of 18.3 +/- 0.5 hours. Patients in the early extubation group were ventilated for an average of 3.3 +/- 0.5 hours (p < 0.0005). No patient in either group required reintubation. Intrapulmonary shunt and oxygen delivery were not significantly different between the groups at any time during the study period. There was no mortality or significant morbidity in either group. These findings suggest that in high risk surgical patients, prophylactic ventilation, per se, may not diminish respiratory complications or improve gas exchange.

The effect of prehospital fluids on survival in trauma patients.

The effect of prehospital intravenous fluids upon survival was studied in 6,855 trauma patients. Mean prehospital time was 36 minutes in both the group of patients who received fluids and the group that did not. The volume of fluid administered was not significantly different in the group who survived compared to those who died. Eighty-five per cent of the patients had an Injury Severity Score (ISS) less than 25 and the mortality rate in the 56% of patients in this group who received fluids was similar to that of the patients who did not receive fluids (0.7% vs. 0.5%). Twelve per cent of the patients had an ISS between 25 and 50. Sixty per cent of these patients received fluids and the mortality rates were similar to the patients who received fluids compared to those who did not (23% vs. 22%). Three per cent of patients had an ISS of greater than 50 and the mortality rate was highest in this group but was not influenced by the administration of fluids (90% vs. 86%). Comparison of groups with similar probability of survival according to the TRISS methodology also failed to show an influence of fluid administration on survival. The mortality rate in patients with an initial systolic blood pressure (BP) of 90 torr or greater was compared to the rate in patients with an admission BP less than 90 torr. Although hypotension was associated with a significantly higher mortality rate, the administration of fluids had no influence on this rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Bilateral scapular fractures from accidental electric shock.

This report presents a patient with bilateral scapular fractures resulting from an accidental electric shock (440 volt, 60 cps current). This appears to be a previously unreported injury. A postulated mechanism of injury is discussed.

Effectiveness of peritoneal lavage in blunt abdominal trauma.

To analyze the effectiveness of peritoneal lavage and to define its limitations in the evaluation of patients who have sustained blunt abdominal trauma, a prospective study of 500 such patients was undertaken by the Trauma Service at the Naval Hospital, San Diego. Utilizing a qualitative colorometric method to evaluate the degree of hemoperitoneum, patients could rapidly be divided into three clinical groups: strongly positive, weakly positive, and negative. Using this method, patients with a strongly positive peritoneal lavage had a 94% incidence of significant intra-abdominal injuries. In 333 patients with a negative lavage, there was no documented incidence of significant intra-abdominal injuries. Visceral angiography and abdominal echography were utilized in this group of patients to identify those with significant intra-abdominal injuries. By utilizing this approach, there were only eight unnecessary celiotomies in the total group of 500 patients. It is concluded, therefore, that peritoneal lavage is a safe, rapid, and effective means of evaluating patients who have sustained blunt abdominal trauma.

Evaluation of splenorrhaphy: a grading system for splenic trauma.

Since April 1977, we have used splenorrhaphy as the procedure of choice for splenic trauma. To evaluate the efficacy of this procedure, we graded splenic injury based upon the extent of splenic repair in 77 patients with blunt abdominal trauma. This grading system is as follows: Grade 1-capsular treatment (five patients); Grade 2-capsular or parenchymal injuries requiring topical hemostatic agents (13 patients); Grade 3-parenchymal injuries requiring suture repair (nine patients); Grade 4-parenchymal injuries requiring partial splenic resection (seven patients); Grade 5-total splenic devascularization or uncontrollable bleeding from the splenic pedicle requiring splenectomy (43 patients). Twenty-nine patients had associated orthopedic injuries, and 42 patients had associated intra-abdominal or thoracic injuries. Mean operative time was 130 +/- 10 minutes. Operative time increased with severity of associated intra-abdominal injuries. Mean operative transfusion requirement was 500 +/- 100 cc of packed red blood cells. Transfusion requirements were not related to the severity of splenic injury. Twenty-three patients developed complications. Pancreatitis occurred in three patients, atelectasis of pneumonitis in eight patients, ten developed wound infections, and two patients required reoperation for small-bowel obstruction. Complication rates were not related to the degree of splenic injury. The grading system described herein provides a framework for sound clinical judgment and comparison of results in the management of splenic injuries.

Serum oncotic pressure and oncotic-hydrostatic pressure differences in critically ill patients.

The possible influence of serum colloid oncotic pressure (COP) and the gradient between COP and pulmonary capillary wedge pressure (COP-PCWP) on respiratory insufficiency and survival was studied prospectively in 77 critically ill surgical patients by daily simultaneous measurements of COP, PCWP, and intrapulmonary shunt (Qs/Qt). Mean ages of survivors (N = 51) and nonsurvivors (n = 26) were 46 +/- 3 years (survivors) and 58 +/- 4 years (nonsurvivors), respectively (p less than 0.01). Lowest value of COP was similar in survivors (15 +/- 1 torr) and in nonsurvivors (14 +/- 1 torr). Lowest value of COP-PCWP in survivors was 3 +/- 1 torr and -1 +/- 2 torr in nonsurvivors (p less than 0.05). The difference in COP-PCWP was secondary to a significantly greater PCWP in nonsurvivors (16 +/- 1 torr) than in survivors (12 +/- 1 torr) (p less than 0.01). For each patient, Qs/Qt measured at the time of lowest measured COP was not significantly different between survivors and nonsurvivors (0.18 +/- 0.01) in survivors and 0.20 +/- 0.01 in nonsurvivors) and measured at lowest COP-PCWP (0.18 +/- 0.01 in survivors, and 0.21 +/- 0.01 in nonsurvivors). No correlation was found between either lowest COP or lowest COP-PCWP and Qs/Qt. Progressive respiratory insufficiency was not a dominant factor in determining respiratory insufficiency was not a dominant factor in determining mortality. These data suggest that COP alone is not a critical factor in determining either survival or respiratory insufficiency as measured by Qs/Qt in critically ill surgical patients.

Crystalloid versus colloid in fluid resuscitation of patients with severe pulmonary insufficiency.

Forty-six patients with severe pulmonary insufficiency were prospectively studied to compare the effects of resuscitation with either crystalloid or colloid. By random number, 26 patients received RL and 20 patients received 5 per cent ALB to maintain hemodynamic stability. Groups were comparable with respect to the cause of pulmonary insufficiency, age and sex. For the duration of the study and at 48 hours, there was no statistically significant difference between groups with respect to the following: cardiac index, colloid osmotic pressure (COP), pulmonary capillary wedge pressure (PCWP), COP-PCWP gradient, right and left ventricular stroke work indices, and amount of constant positive airway pressure required for treatment. Both groups had a significant improvement in intrapulmonary shunt (Qs/Qt) after 24 hours of treatment. The Qs/Qt in the ALB group was significantly lower than the RL group at the termination of the study, but this did not affect outcome. The RL group required more fluid than the ALB group, but the difference was not statistically significant. No clinical advantage was found for either solution in this study.