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Biomedical subjects

W C Shoemaker

Publications and source records attributed to W C Shoemaker.

At least 199 records · Page 11Linked to original sources
PubMed1982

Transcutaneous O2 and CO2 monitoring of high risk surgical patients during the perioperative period.

The usefulness of noninvasive transcutaneous oxygen (PtcO2) and carbon dioxide (PtcCO2) sensors as well as invasive monitoring of flow and oxygen transport were evaluated in the perioperative period of a small series of high risk surgical patients. We used the pattern of physiological events preceding intraoperative death as the criteria for evaluation of the relative usefulness of these variables. Cardiac output (CO), oxygen delivery (DO2), and O2 consumption (VO2) provided the earliest warning of impending circulatory deterioration and were most useful during critical nonlethal circulatory episodes; these were closely paralleled by the PtcO2 index (PtcO2/PaO2); the PtcCO2 was less sensitive. Heart rate (HR) and mean arterial pressure (MAP) were highly variable with frequent changes unrelated to change in flow and O2 transport.

Carbon Dioxide↗
PubMed1982

Evaluation of colloids, crystalloids, whole blood, and red cell therapy in the critically ill patient.

Experimental and clinical aspects of fluid management problems are reviewed; clinical and physiological criteria for efficacy of various plasma expanders are evaluated. Reduced extracellular water is considered the primary defect of shock by those favoring the use of crystalloids, but hypovolemia is regarded as primary by those favoring the use of colloids. The immediate direct effects of various agents in critically ill patients are evaluated using physiologic criteria associated with survival from life-threatening postoperative illness. In general, colloids improved hemodynamic and oxygen transport, while sodium-rich crystalloids increased arterial pressure and peripheral resistance, but not flow and oxygen transport. Indications for various agents and protocols (clinical algorithms) for resuscitation and critical illness are proposed.

Blood Transfusion↗
PubMed1981

Comparison of the relative effectiveness of colloids and crystalloids in emergency resuscitation.

Over a 2.5 year period, the fluid management of 600 hypotensive patients entering our surgical emergency department was evaluated during a prospective clinical trial of a resuscitation algorithm. The major clinical determinants (low mean arterial pressure, age, severity of illness, primary illness or injury, amount of blood loss, volume of fluids given, use of a protocol or clinical algorithm and satisfactory compliance with the algorithm) were controlled by grouping the patients into specific strata; the resuscitation times were almost always shorter with a regimen of about one-fourth colloids than with crystalloids only. This is consistent with the observations of greater increases in hemodynamic and oxygen transport variables after albumin than after lactated Ringer's solution when the latter was given in either 2 or 4 times the volume.

Adult↗
PubMed1981

Use of transcutaneous oxygen sensors to titrate PEEP.

The relationship of transcutaneous oxygen tension (PtcO2) to arterial oxygen tension (PaO2), pulmonary shunt (Qsp/Qt), mixed venous oxygen tension (PVO2), and O2 delivery was determined in patients with respiratory failure in order to explore the possible usefulness of PtcO2 to titrate the level of positive end expiratory pressure (PEEP). Transcutaneous oxygen sensors were applied to the chest of surgical ICU adult patients who were in acute postoperative respiratory failure. The patients had mechanical ventilation with volume ventilators and an intermittent mandatory ventilation (IMV) rate, which allowed normal pH and arterial CO2 tension ventilation (PacO2). Swan-Ganz and arterial catheters were inserted. The blood volume was measured by iodinated I-125-serum albumin and brought into the normal range, before the study began, with appropriate volume therapy. Serial cardiorespiratory data were taken before and after PEEP was increased from zero to 20 cm H2O, in 5 cm increments. PtcO2 correlated well with PaO2 and PV-O2; it was inversely correlated with Qsp/Qt. PtcO2 correlated with O2 delivery in only seven severely ill patients mean alveolar-arterial oxygen tension difference [A-aDO2] was 380 mmHg and the pulmonary shunt was 37%). For the eight other patients, variations in the greatly elevated cardiac output associated with hypoxemia led to poor correlations between PtcO2 and O2 delivery. There was no significant depression of cardiac output in any of the studies. We conclude that the continuous noninvasive nature of PtcO2 monitoring greatly increased the safety and simplicity of PEEP optimization and respiratory management of adult patients with respiratory failure.

Blood Pressure↗
PubMed1981

Transcutaneous oxygen monitoring of critically ill adults, with and without low flow shock.

One hundred and six critically ill adult patients were monitored continuously with a transcutaneous oxygen sensor (PtcO2); they also were intermittently monitored with conventional invasive hemodynamic and oxygen transport variables. A total of 1073 data sets were taken on 41 patients in the ICU and 65 patients in the operating room. The patients were divided into three groups by cardiac index (CI): relatively normal flow, CI greater than 2.2 L/min x M2; moderate low flow shock, 2.2 greater than CI greater than 1.5 L/min x M2; and severe low flow shock, CI less than 1.5 L/min x M2 x PtcO2 and arterial oxygen tension (PaO2) were compared in two ways: first by linear regression and second by a more simple clinical guide by indexing each transcutaneous value by its respective arterial value (PtcO2 index = PtcO2/PaO2). For 934 data sets taken on 92 patients not in shock, there was a correlation coefficient (r) of 0.89 and a PtcO2 index 0.79 +/- 0.12 (SD). In 5 patients with moderate shock, the r was 0.78 and the PtcO2 index was 0.48 +/- 0.07. In 9 patients with severe shock, there was no correlation between PtcO2 and PaO2 and the PtcO2 index was 0.12 +/- 0.12. In all cases of severe shock, the PtcO2 value responded quickly to changes in blood flow with an approximate 1 min response time (95%). The patients not in shock responded to changes in inspired oxygen concentration (FIO2) with changes in PaO2 and PtcO2 values; the 95% response time was approximately 2 min. The authors conclude that the normal value for PtcO2 for adult surgical patients who are hemodynamically stable is 79 +/- 12% of the PaO2 and that PtcO2 values were reliable, continuous, noninvasive trend monitors of PaO2 in these patients. During circulatory problems when PtcO2 values were compared to PaO2 values (PtcO2 index), the changes reflected trends in the severity of low flow shock.

Adult↗
PubMed1981

Emergency PaO2 estimates in one minute with a transcutaneous oxygen sensor.

Blood was applied directly to the electrode surface of a transcutaneous oxygen sensor (PtcO2) and the oxygen tension value obtained was compared to oxygen tension value from a conventional blood gas machine. Three hundred and seventeen blood samples were analyzed at four PtcO2 electrode temperatures: 37, 40, 42, and 45 degrees C. A linear regression of PO2 vs. PtcO2 blood drop (PbdO2) produced correlation coefficients (r) from 0.99 to 0.93 and standard errors from 3.2 to 4.7 torr at these temperatures. The mean time for stabilization was 51 sec. The PO2 ranged from 4--150 torr. The authors conclude that an accurate PO2 of blood can be obtained within 1 min by placing a drop of blood on the surface of a PtcO2 electrode.

Blood Gas Analysis↗
PubMed1981

Transcutaneous PCO2 monitoring on adult patients in the ICU and the operating room.

Studies were performed on 44 patients who were monitored continuously with transcutaneous carbon dioxide (PtcCO2) sensors. The patients were monitored intermittently with arterial and mixed venous blood gases and full hemodynamic and oxygen transport data. Twenty of the studies were performed intraoperatively. A total of 411 data sets revealed a correlation coefficient, r, between arterial and transcutaneous PCO2 of 0.80 when the patients were not in low flow shock, i.e., cardiac index (CI) greater than 1.5 L/min x M2. On the basis of these data, the authors have found the normal arterial-transcutaneous carbon dioxide gradient, delta CO2, (delta CO2 = PtcCO2 -- PaCO2) to be 23 +/- 11 torr. The PtcCO2 monitor was found to be a valuable trend monitor of arterial CO2 tensions of adults during adequate cardiac function in the ICU and the operating room. Twenty-four data sets were collected while 3 patients were monitored during severe shock (CI less than 1.5 L/min x M2). PtcCO2 trended inversely with changes in CI during shock and did not follow PaCO2 (r = --0.85). During shock, delta CO2 = 61 %/- 25 torr. The severity of shock could be roughly determined by comparing the PtcCO2 values with arterial CO2 tensions.

Adult↗
PubMed1981

Sequential hemodynamic and oxygen transport responses in hypovolemia, anemia, and hypoxia.

Sequential cardiorespiratory measurements were made in 30 mongrel dogs during controlled hypovolemia, normovolemic anemia, and hypoxia. The responses to each of these three types of O2 deprivation were studied both as a function of time and of the rate of O2 delivery (normalized cardiac output x arterial O2 content). With progressively decreasing O2 delivery, compensations appeared, reached a maximum, and fell before the final circulatory deterioration. O2 extraction increased in each experiment, but there was differences in the hemodynamic responses to the three types of O2 deprivation; e.g., cardiac output increased in the anemic dogs, and there were greater increases in systemic and pulmonary resistances after hemorrhage. The striking finding was that O2 consumption (VO2) remained relatively constant until the preterminal stage. At this time O2 delivery had fallen from about 27 to less than 10 ml . min-1 . kg-1, blood volume was less than 50%, hematocrit was less than 8%, and arterial O2 tension was less than 30 Torr at an average fractional inspired O2 concentration of 8%, for the hypovolemic, anemic, and hypoxic groups, respectively. Then VO2 dropped precipitously and death rapidly occurred. These results suggest that VO2 represents a physiological marker of impending death in the face of progressively diminishing O2 delivery.

Anemia↗
PubMed1981

Physiologic responses to operation in high risk surgical patients.

Fifty-three high risk surgical patients were studied using invasive cardiorespiratory monitoring to gain physiologic perspective of the perioperative period. Multiple hemodynamic and oxygen transport variables were tracked through the preoperative, intraoperative and postoperative periods using frequent sequential measurements. Impairment of cardiac and pulmonary function was measured intraoperatively, but this was compensated by therapy, so that oxygen delivery was maintained. Nonetheless, there was a decrease in oxygen consumption intraoperatively due to decreased oxygen extraction. Postoperatively, there was an increase in cardiac output, oxygen delivery and oxygen consumption. It is postulated that the fall in oxygen consumption intraoperatively may result in a metabolic debt and that a hyperdynamic postoperative state represents the physiologic response necessary to repair the damage caused intraoperatively by relative cellular hypoxia.

Cardiac Output↗
PubMed1980

Treatment of surgical emergencies with and without an algorithm.

A patient care algorithm was developed for resuscitation of patients entering the surgical emergency department with hypotension. The diagnostic workup, monitoring, and therapy were progressively excalated according to admission blood pressure and responses to therapeutic interventions. The branching-chain logic is ideally suited for rapid decision making in emergency conditions where the need is most urgent, the time constraints are most severe, and the potential improvements in terms of patient salvage are greatest. Preliminary results from these ongoing clinical trials indicate that (1) physicians can and will use an algorithm for emergency medical service resuscitation; (2) in a university hospital with a large emergency service and a commitment to emergency care, the physicians using the aigorithm performed as well as and in some instances better than those not using the algorithm; and (3) the use of the algorithm may prevent delays in resuscitation and lead to less morbidity and mortality. Thus, we conclude that the algorithm helps to organize emergency care, establish standards, and improve care.

Adult↗
PubMed1980

Determinants of morbidity and mortality in blunt abdominal trauma.

We reviewed retrospectively 260 consecutive patients operated upon for blunt abdominal trauma in a 7-year period; there were 318 injured organs and 40 deaths, giving a mortality of 15%. The injuries with the highest mortality were duodenal, vascular, hepatic, pancreatic, and gastrointestinal perforations; splenic, small bowel and gallbladder trauma had the lowest mortality. Almost half of the fatal cases but less than a quarter of the survivors had two or more non-abdominal injuries and 72% of the survivors but only 32% of the non-survivors had two or more injured abdominal organs. Diagnostic procedures were obtained preoperatively in 98% of the patients; about half of these were positive but only 12% were specifically diagnostic of a particular organ injury. Using the correct organ and the correct injury as the criteria, half of the cases were correctly diagnosed preoperatively, although all of the patients were judged to have some form of significant abdominal trauma. Delays from attempts to establish a precise preoperative diagnosis contributed to increased morbidity and mortality, particularly in patients who were haemodynamically unstable. After a Trauma Unit was established, the time from admission of patients to hospital until operation and the overall mortality were significantly reduced, particularly for those with hypotension.

Abdominal Injuries↗
PubMed1980

Use of volume loading to obtain preferred levels of PEEP. A preliminary study.

Hemodynamic and oxygen transport measurements were made with successive increments of positive end-expiratory pressure (PEEP) in 14 episodes of ARDS in 11 patients who had normal or slightly increased blood volumes. "Preferred" or optimal PEEP was defined as the PEEP value associated with the greatest VO2 that did not compromise pulmonary function as determined by shunting (Qs/Qt). The preferred PEEP averaged 10.7 +/- 2.7 (SD) cm H2O in the patients who had appreciable reduction in cardiac index (CI) by the time this level of PEEP was reached. In 6 patients, the CI fell approximately 15%; then albumin, 25 g, was given. This restored CI, improved oxygen transport, and permitted us to give additional 10-15 cm H2O of PEEP, i.e., until 20--25 cm H2O was reached; this was achieved without hemodynamic impairment. The final preferred PEEP in these patients averaged 14.1 +/- 3.6 (SD) cm H2O. The authors conclude that the titration of PEEP as well as fluid therapy may be used to maximize VO2 in patients with early shock lung.

Adult↗