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Biomedical subjects

R M Peters

Publications and source records attributed to R M Peters.

At least 73 records · Page 4Linked to original sources
PubMed1983

Maximal exercise at extreme altitudes on Mount Everest.

Maximal exercise at extreme altitudes was studied during the course of the American Medical Research Expedition to Everest. Measurements were carried out at sea level [inspired O2 partial pressure (PO2) 147 Torr], 6,300 m during air breathing (inspired PO2 64 Torr), 6,300 m during 16% O2 breathing (inspired PO2 49 Torr), and 6,300 m during 14% O2 breathing (inspired PO2 43 Torr). The last PO2 is equivalent to that on the summit of Mt. Everest. All the 6,300 m studies were carried out in a warm well-equipped laboratory on well-acclimatized subjects. Maximal O2 uptake fell dramatically as the inspired PO2 was reduced to very low levels. However, two subjects were able to reach an O2 uptake of 1 l/min at the lowest inspired PO2. Arterial O2 saturations fell markedly and alveolar-arterial PO2 differences increased as the work rate was raised at high altitude, indicating diffusion limitation of O2 transfer. Maximal exercise ventilations exceeded 200 l/min at 6,300 m during air breathing but fell considerably at the lowest values of inspired PO2. Alveolar CO2 partial pressure was reduced to 7-8 Torr in one subject at the lowest inspired PO2, and the same value was obtained from alveolar gas samples taken by him at rest on the summit. The results help to explain how man can reach the highest point on earth while breathing ambient air.

Adult↗
PubMed1983

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.

Aorta, Abdominal↗
PubMed1982

Management of the patient with emphysema, coronary artery disease, and lung cancer.

Coronary artery disease, emphysema, and lung cancer often occur together and have cigarette smoking as a common etiologic contributor. The management of the patient with lung cancer, coronary artery disease, and emphysema is complex. The patient with significant coronary artery disease should undergo coronary artery bypass before or concurrently with pulmonary resection. Only proven carcinomas should be resected at the time of coronary artery bypass grafting because immunosuppression secondary to cardiopulmonary bypass can result in the life-threatening spread of fungal or other infections if biopsy is performed at the time of cardiopulmonary bypass. The risk of pulmonary resection is increased in the patient with emphysema because of decreased efficiency of the lungs and chest wall. Likewise, emphysema results in greater risk in the patient with coronary artery disease because of increased demands on the heart.

Coronary Disease↗
PubMed1982

The role of limited resection in carcinoma of the lung.

Thirty years ago lobectomy was considered inadequate excision for carcinoma of the lung. In 1982 we are at the same point in comparing lobectomy with lesser resections. Limited pulmonary reserve and second carcinomas, as well as evidence of control by wedge and segmental resection, indicate that the need for lobectomy should be reappraised in carcinomas limited to smaller portions of the lungs.

Carcinoma↗
PubMed1982

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.

Adult↗
PubMed1981

Protein vs electrolytes and all of the Starling forces.

Hemodilution-induced reductions of the intravascular protein concentration in patients and experimental animals with intact capillaries do not lead to pulmonary edema, despite significant increases in the amount of extravascular water in the systemic interstitial space. The protective factors are a drop in the extravascular concentration of protein, a rise in interstitial tissue pressure, and an increase in lymph flow. If the capillary endothelium is damaged, protein leaks into the extravascular space, and protein infusion has a diminished effect on fluid exchange across the capillary. Whether capillaries are intact or injured, prevention of increases in capillary hydrostatic pressure is the most important factor in preventing pulmonary edema. Administration of hypertonic fluids may provide a useful method of limiting total fluid infusion and reducing cell swelling after blood loss.

Animals↗
PubMed1981

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.

Blood Coagulation↗
PubMed1981

Complications of the flow-directed pulmonary artery catheter: A prospective analysis in 219 patients.

In order to determine and analyze the complication rate of the insertion and maintenance of the balloon-tipped, flow-directed pulmonary artery catheter (PAC), the authors prospectively studied the use of 320 catheters in 219 critically ill patients. Mean patient age was 53 +/- 1 years, and 36% had a history of cardiovascular disease. Mean duration of catheterization averaged 76 +/- 3 h. Major complications occurred in 3% of catheterizations. These included six pneumothoraces; three arrhythmias requiring treatment, one of which was fatal; and one subclavian vein thrombosis. Site complications occurred more frequently in catheters maintained longer than 72 h. These findings suggest that, when indicated in the care of critically ill patients, the properly placed and maintained PAC has an acceptably low morbidity and mortality rate, particularly when used for 72 h or less.

Arrhythmias, Cardiac↗
PubMed1981

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.

Adolescent↗
PubMed1981

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.

Aged↗
PubMed1981

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.

Abdominal Injuries↗
PubMed1980

Interstitial fluid pressure changes during cardiopulmonary bypass.

The effects of cardiopulmonary bypass using hemodilution on interstitial fluid pressure were measured using the Scholander wick technique. In 10 mongrel dogs, interstitial fluid pressure was measured in subcutaneous tissue, skeletal muscle, stomach, and left ventricle before and during 2 hours of cardiopulmonary bypass. Changes in interstitial fluid pressure were correlated with plasma colloidal osmotic pressure and duration of bypass. In subcutaneous tissue and skeletal muscle, interstitial fluid pressure increased during bypass; it did not change in the stomach. End-diastolic interstitial fluid pressure in the left ventricle increased significantly. These increases in pressure were presumably due to an increase in interstitial water. The rise in interstitial fluid pressure acts to partially neutralize the fall in plasma colloidal osmotic pressure.

Animals↗
PubMed1980

Sickle-cell hemoglobin: fall in osmotic pressure upon deoxygenation.

Macromolecules such as hemoglobin exert both kinetic and matrix effects on osmotic pressure. The kinetic osmotic pressure of sickle-cell hemoglobin is lost upon deoxygenation at physiological erythrocyte concentrations. The non-kinetic or matrix component of osmotic pressure remains relatively unchanged. Loss of thermal-osmotic activity during deoxygenation occurs throughout a hemoglobin concentration range between 2.5 and 35 g/100 ml. Deoxygenation of sickle-cell hemoglobin causes aggregation such that the matrix effect is unchanged but the kinetic (van't Hoff) effect nearly vanishes. A loss of intracellular osmotic pressure during deoxygenation could dehydrate the erythrocyte sufficiently to promote more rapid sickle-cell hemoglobin aggregation. Subsequently, complete gelation of these aggregates could cause additional water loss and thrust the sickled cell into an irreversible cycle. The osmotic pressure of normal hemoglobin does not change appreciably during deoxygenation and is essentially the same as the osmotic pressure of oxygenated sickle-cell hemoglobin.

Erythrocytes, Abnormal↗
PubMed1980

Mechanism of death in massive fluid infusion.

To determine the effects of infusion of large volumes of crystalloid, a series of dogs was subjected to intravenous injection of oleic acid and moderate hypovolemic shock for 1 hour. They were then resuscitated with 50 cc/kg of Ringer's lactate over 1 hour in one group and 2 hours in the other. Eight of nine receiving the fast infusion died during the first 2 days, and seven of eight receiving the slow infusion lived for the full 3 days of the study. The dogs that died all had large intrapulmonary shunts and gross pulmonary edema at autopsy. Both groups received the same total amount of fluid. No differences in vascular pressure or cardiac function large enough to explain the differences were found. The critical difference was the rate of fluid infusion. The high-permeability pulmonary edema appears to have been aggravated by a transitent pulmonary overperfusion induced by fast infusion of fluid.

Animals↗
PubMed1980

Interstitial hydrostatic pressures in patients undergoing CABG and valve replacement.

Using the Scholander-Hargens wick technique to measure interstitial fluid hydrostatic pressure (IFP) in thigh muscle (MIP) and subcutaneous tissue (SQIP), we have studied 12 patients undergoing cardiopulmonary bypass (CPB). Simultaneous measurements were made of serum total proteins (TP) and colloid osmotic pressure (COP). Bypass was carried out with a nonblood, noncolloid prime. In the postoperative period, colloid and blood were given which raised COP above prebypass levels (see Table II). MIP rises more with hemodilution than does SQIP and is less negative throughout. MIP rises faster when COP drops than does SQIP. These findings suggest that subcutaneous tissue interstitial space is loose and has a high compliance, whereas muscular tissue interstitial space is tight and has a low compliance. The increased pressure represents increase in fluid which is then removed promptly as COP is restored in the postoperative period. Experimental studies in animals show a response similar to MIP in the myocardium.

Aged↗