Attenuated vascular reactivity in dogs with anteroventral third ventricle lesions.

Lesion of the anteroventral portion of the third cerebral ventricle causes hypernatremia, adipsia, and attenuation of the pressor response to intravenous administration of angiotensin II and norepinephrine. In addition, these lesions prevent the development of several experimental models of hypertension. In this study, a lesion of the third cerebral ventricle region was made in 14 dogs. In seven dogs in which hypernatremia developed the lesions included the organum vasculosum of the lamina terminalis; seven animals in which the circumventricular organ was spared by the lesion remained normonatremic. Vascular responsiveness of isolated right carotid artery rings to angiotensin II and phenylephrine was assessed 3 days after lesioning the anteroventral portion of the third cerebral ventricle. In endothelium-denuded ring vessels, vasoconstrictor responses to phenylephrine were significantly decreased in animals both with and without inclusion of the organum vasculosum of the lamina terminalis. A similar effect was observed in intact vessels of dogs in which the circumventricular organ was spared but not in those with lesions that included this area. In contrast, angiotensin II-induced vasoconstriction was significantly decreased in the arteries with intact endothelium of both groups of lesioned animals. These data show that lesion of the anteroventral third ventricle area alters alpha 1-adrenergic and angiotensin II vascular responsiveness in isolated carotid artery rings with the possible participation of the endothelium.

Systemic arterial hypertension associated with cardiac surgery.

Significant hypertension can develop in 15 to 40 percent of patients undergoing various types of cardiac surgery. These hypertensive episodes can occur at almost any time before, during or after open or closed chest operations. The various hypertensions encountered in this context do not form a homogeneous entity; they are nt due to the same causes and do not necessarily develop by the same mechanisms. Their frequency and seriousness have been demonstrated by reports from many centers: hence, the urgent need for accurate definition of their various types to allow correct identification and therapy. A classification based on well defined clinical events is therefore proposed and possible mechanisms for the more common types of hypertension are reviewed. Prophylactic measures nclude reassurance, attention to details of anesthesia and maintenance of preoperative antihypertensive therapy when indicated; for patients with coronary artery disease, preventive nitrate therapy as well as prompt attention to chest pain is essential. Both general and specific antihypertensive measures to control the more common types of hypertension complicating cardiac surgery are outlined.

Hemodynamics of postmyocardial revascularization hypertension.

The evolution of hemodynamic variables during the development of postcoronary bypass hypertension was investigated with use of serial cardiac output determination (indocyanine green dye) in 17 patients. Seven of the 17 patients remained normotensive (Group I) during the follow-up period of 4 to 6 hours after operation, whereas 10 (Group II) had a steady increase in blood pressure (173/101 mm Hg +/- 5.9/2.4 [mean +/- standard error] from 132/78 +/- 4.0/2.5 mm Hg immediately postoperatively, P less than 0.001) during the same time interval. Patients in Group I had no significant change in cardiac output, total peripheral resistance or heart rate. In contrast, patients who became hypertensive had a significant increase in total peripheral resistance (47 +/- 2.9 units/m2 from an initial level of 38 +/- 2.5 units/m2, P less than 0.001) with no significant change in cardiac index (2.73 +/- 0.17 versus 2.66 +/- 0.25 liters/min per m2, P greater than 0.10). Their heart rate, which was rapid initially (102 +/- 3.7 beats/min), remained unchanged during the hypertensive episode (103 +/- 3.0 beats/min). The mean rate of left ventricular ejection was not reduced by the increase in pressure and even tended to increase further in all but one patient. Central venous pressure (measured in all patients) and left atrial pressure (measured in eight patients) remained constant throughout the study in both Groups I and II. The results suggest that the mechanism underlying this type of hypertension is a generalized hemodynamic disturbance possibly related to overall sympathetic overdrive rather than the result of improved cardiac performance induced by myocardial revascularization.

Unilateral stellate block in the treatment of hypertension after coronary bypass surgery. Implications of a new therapeutic approach.

Unilateral stellate ganglion block (right or left) was achieved by local injection of 15 ml of lidocaine in 27 patients with hypertension after coronary bypass surgery. The stellate block led to rapid and sustained control of blood pressure in 18 patients (9 of 15 with right stellate block and 9 of 12 with left stellate block). The reduction in arterial pressure was associated with significant (P less than 0.01) reductions in total peripheral resistance and heart rate but no significant changes in cardiac output or central venous or left atrial pressures. This hemodynamic pattern as well as effectiveness of a unilateral approach suggests that the stellate block reduced arterial pressure by interrupting the afferent limb of a pressor reflex from the heart or great vessels, or both. The procedure was free from side effects and helped avoid prolonged parenteral administration of potent antihypertensive drugs.

Acute hypertension immediately after coronary artery surgery.

Hypertension immediately after coronary surgery is a problem in about one third of the patients so treated. This report discusses the possible causes of postoperative hypertension and describes several means of controlling the complication.

Myocardial protection during cardiac operations. Decreased morbidity and lower cost with blood cardioplegia and coronary sinus perfusion.

The efficacy of myocardial protection with a single aortic crossclamp and blood cardioplegia was evaluated in 819 consecutive patients stratified for preoperative condition by means of a new clinical risk scoring system. A protocol using either antegrade or antegrade/retrograde blood cardioplegia was compared with antegrade crystalloid cardioplegia in 2582 similar, consecutive, and concurrent patients. In the blood cardioplegia cohort, 97 (11.8%) patients had 129 complications compared with 407 (15.8%) patients and 675 complications in the crystalloid cardioplegia group (p = 0.006). In high-risk patients, combined antegrade/retrograde cardioplegia significantly reduced myocardial infarction, stroke, and respiratory and wound complications. Despite the significantly longer aortic crossclamp time required for blood cardioplegia, patients undergoing crystalloid cardioplegia were 1.7 (95% confidence interval 1.3, 2.1) times more likely to have a morbid event. Time in the intensive care unit, length of hospitalization, and length-of-stay outlier status were significantly decreased in the blood cardioplegia compared with the crystalloid cardioplegia group. The net savings in hospital cost amounted to $2196 per case. When compared separately with crystalloid cardioplegia, combined antegrade/retrograde blood cardioplegia accounted for most of the morbidity reduction by significantly reducing perioperative myocardial infarction, wound complications, and length of stay in patients having reoperations. Antegrade/retrograde blood cardioplegia did not influence 1-year survival or event-free survival, even when risk was considered.

Pattern of hemodynamic alterations during coronary artery operations.

Twenty-four patients were studied to determine the relative importance of cardiac and peripheral factors in the hemodynamic changes associated with coronary artery operations. None had preoperative evidence of ventricular impairment. Anesthetic management was standardized for all. Sequential hemodynamic measurements revealed the following: (1) Five minutes following induction of anesthesia, all hemodynamic indices were stable except for an increase in heart rate (p less than 0.001). Sternotomy and pericardiectomy were followed by a drop in cardiac index (p less than 0.01) and systolic blood pressure (p less than 0.01). (2) Late during bypass, there was a significant, parallel reduction in both hematocrit and systemic vascular resistance (SVR) (p less than 0.001 and 0.01, respectively). (3) Five minutes after termination of bypass, cardiac output was markedly elevated (p less than 0.001) in association with a decrease in SVR (p less than 0.001), marked hemodilution (p less than 0.001), and tachycardia (p less than 0.001). (4) Following sternal closure, and despite the fact that the hematocrit was still reduced (p less than 0.001), there developed a trend of increased mean arterial pressure (MAP) and SVR with a reduction in cardiac index. These changes were further accentuated 1 hour postoperatively. The SVR was 33% higher than in the previous stage (p less than 0.01), whereas the high cardiac index recorded with initiation of bypass declined significantly to preoperative values. Throughout the studies, there was a strong correlation between alterations in hematocrit and changes in cardiac index and SVR. Blood pressure variations showed no correlation with changes in cardiac output but were significantly related to alterations of peripheral resistance. Sequential determinations of plasma renin activity and catecholamine levels showed no significant alterations in either. The alterations reported describe not only group averages but also the behavior of every patient investigated. The results suggest that in patients with normal or only mild left ventricular impairment, the major factor influencing arterial pressure variations during coronary artery operations and in the postoperative period was the change in peripheral resistance rather than alterations in cardiac output. In the treatment of hypotension under these conditions, one should take into account variations in peripheral vascular resistance and not depend solely on assumed changes in myocardial performance.

Low factor XIIIA levels are associated with increased blood loss after coronary artery bypass grafting.

Current hematologic approaches to minimize postoperative bleeding have focused principally on antifibrinolytic agents. To explore whether a need might exist to promote clot stabilization independent of steps that might be taken to prevent lysis, we followed levels of the functional A-chain of factor XIII (fibrin stabilizing factor) immunologically in 19 patients undergoing coronary artery bypass grafting. The levels of factor XIIIA together with alterations in fibrinogen were followed at five stages of operation: (1) initial catheter placement (control), (2) heparinization, (3) initiation of cardiopulmonary bypass, (4) discontinuation of cardiopulmonary bypass, and (5) heparin neutralization with protamine sulfate. Significant (p < 0.05) inverse correlations were observed between postoperative chest-tube drainage volumes and levels of XIIIA at stages 1 through 3, and borderline associations (p < 0.1) were observed for stages 4 and 5. Pronounced losses of factor XIIIA accompanied initiation of cardiopulmonary bypass, when levels fell to 43% +/- 12% (standard deviation) of the control value, significantly below the 59% +/- 9% of the control value expected from hemodilution. By comparison, fibrinogen concentrations fell only to the extent attributable to hemodilution, unaccompanied by substantial degradation as indicated by electrophoretic, functional, and immunologic assays. There was a reversible heparin-induced precipitation of fibrin complexes and fibrinogen dimers from the blood on initiation of hypothermia, but these components returned to the circulation on restoration of normothermia. This precipitation was unrelated to losses of factor XIIIA. The findings warrant inference that XIIIA supplementation in deficient states should be considered as an adjunct to other therapies for postoperative bleeding.

Failure of positive end-expiratory pressure to decrease postoperative bleeding after cardiac surgery.

To determine whether the application of positive end-expiratory pressure (PEEP) in the postoperative period after cardiac operation would reduce postoperative blood loss, the number of transfusions required, or the rate of reoperation for bleeding, we conducted a prospective study of 83 patients who underwent elective coronary revascularization. These patients were randomly assigned to receive either PEEP (10 cm H2O) or no PEEP (zero end-expiratory pressure). All other aspects of their care were identical. There was no statistically significant reduction in the amount of bleeding in patients treated with PEEP at 8 or 24 hours postoperatively. There was no significant difference in hematocrit between the groups preoperatively or postoperatively. There was no statistically significant difference in the number of reexplorations for bleeding. Finally, there was no significant difference between the groups in the amount of blood administered. On the basis of our results, we conclude that the application of PEEP in the postoperative period of cardiac operation did not reduce the amount of blood loss, the need for reexploration for bleeding, or the blood requirements in this group of patients.

Mechanism and frequency of brachial plexus injury in open-heart surgery: a prospective analysis.

A computer-assisted prospective analysis of 531 patients undergoing open-heart operations revealed that 26 patients (5%) sustained brachial plexus injury. In 22 of the 26 patients (85%), the lesion involved the lower trunk or C8-T1 nerve roots. Electromyograms confirmed the clinical impression in 13 patients. In 19 of the 26 patients (73%), the side on which the plexus lesion was found correlated with the side of internal jugular vein cannulation. Because of the anatomical proximity of the lower trunk to the internal jugular vein and the preponderance of lower trunk lesions, we postulate that traumatic cannulation may be a major mechanism of plexus injury. Thus, the resulting syndrome of pain, dysesthesias, and hand weakness may sometimes be preventable.

ICU admission score for predicting morbidity and mortality risk after coronary artery bypass grafting.

BACKGROUND: This study was performed to develop an intensive care unit (ICU) admission risk score based on preoperative condition and intraoperative events. This score provides a tool with which to judge the effects of ICU quality of care on outcome. METHODS: Data were collected prospectively on 4,918 patients (study group n = 2,793 and a validation data set n = 2,125) undergoing coronary artery bypass grafting alone or combined with a valve or carotid procedure between January 1, 1993, and March 31, 1995. Data were analyzed by univariate and multiple logistic regression with the end points of hospital mortality and serious ICU morbidity (stroke, low cardiac output, myocardial infarction, prolonged ventilation, serious infection, renal failure, or death). RESULTS: Eight risk factors predicted hospital mortality at ICU admission, and these factors and five others predicted morbidity. A clinical score, weighted equally for morbidity and mortality, was developed. All models fit according to the Hosmer-Lemeshow goodness-of-fit test. This score applies equally well to patients undergoing isolated coronary artery bypass grafting. CONCLUSIONS: This model is complementary to our previously reported preoperative model, allowing the process of ICU care to be measured independent of the operative care. Sequential scoring also allows updated prognoses at different points in the continuum of care.

Increased risk and decreased morbidity of coronary artery bypass grafting between 1986 and 1994.

BACKGROUND: The collective impact of advances in medical, surgical, and anesthetic care on the characteristics and outcomes of patients who undergo coronary artery bypass grafting was assessed. METHODS: We compared the demographic and clinical characteristics, preoperative risk factors, morbidity, and mortality of two groups of patients who underwent coronary artery bypass grafting in isolation or in combination with other procedures between July 1, 1986, and June 30,1988 (group 1, n = 5,051), and between January 1, 1993, and March 31, 1994 (group 2, n = 2,793). The patients were stratified according to their preoperative risk level. Outcome measures consisted of changes in preoperative risk categories; hospital mortality rates; overall and risk-adjusted major cardiac, neurologic, pulmonary, renal, and septic morbidity rates; and intensive care unit length of stay. RESULTS: Changes in the distribution of risk categories, from a median of 2 to 4 on a 9-point scale (p < 0.001), indicated that patients in group 2 were at significantly higher risk than those in group 1. The risk-adjusted mortality rate did not change (2.8% to 2.9%; p = 0.15), but the risk-adjusted morbidity rate decreased significantly (14.5% to 8.8%; p < 0.001). CONCLUSIONS: At our institution, patients who undergo coronary artery bypass grafting are now at greater preoperative risk at the time of hospital admission. However, their morbidity rate is significantly lower and their mortality rate is unchanged, results that we attribute to the collective impact of changes in our medical and surgical procedures.

Respiratory care following open heart surgery.

Respiratory care of patients undergoing open heart surgery should begin in the preoperative period. Patients must stop smoking, and if obese they are encouraged to lose weight. Pulmonary infection is treated and secretions must be eliminated. Postoperative hypoxemia, which is an expected event following anesthesia and surgery, is aggravated by circulatory instability and pulmonary complications. Following open heart surgery pulmonary complications such as atelectasis, congestion, edema, postperfusion lung, pneumothorax, pleural effusion, and hemothorax are common. Respiratory care should be planned to avoid these complications and to treat them promptly should they occur. Routinely every patient is mechanically ventilated for at least 12 to 18 hours following surgery. The type of ventilator used and its parameters are adjusted according to the clinical condition of the patient to maintain adequate oxygenation and to prevent any respiratory acidosis. When indicated, PEEP is applied to improve arterial oxygenation. Respiratory care is extended for at least 5 days after termination of artificial ventilation. Oxygen therapy is given with either a nasal catheter or a mask, according to the patient's need. IPPB and physiotherapy are continued until the patient shows no signs of pulmonary infection and is capable of effectively eliminating secretions. This routine management and extended postoperative respiratory care definitely contribute to the successful outcome of open heart surgery.

Enhanced cardiac performance following cardiopulmonary bypass.

Changes in cardiac performance during coronary revascularization surgery were followed in 22 selected patients with normal or mildly impaired left ventricles; vasoactive or inotropic drugs were generally avoided. Arterial pressure, filling pressures, and cardiac output were measured; stroke volume and work were calculated before induction of anesthesia, following sternotomy, soon after discontinuation of extracorporeal circulation, and one hour postoperatively. Induction and sternotomy were associated with a depressant effect on cardiac performance. After extracorporeal circulation, however, cardiac performance recovered, cardiac output increased to 7 +/- 0.5 l/min from a preoperative control of 4.9 +/- 0.3 L/min (p less than 0.002) without an elevation of atrial pressures. This increase in cardiac output after bypass resulted from decreased afterload and increased preload secondary to hemodilution. Cardiac performance approached control values early in the postoperative period.

The use of APACHE III to evaluate ICU length of stay, resource use, and mortality after coronary artery by-pass surgery.

OBJECTIVE: To identify patient characteristics that are associated with increased ICU length of stay, resource use, and hospital mortality after coronary artery bypass surgery. DESIGN: Prospective, multicenter study. SETTING: Six tertiary care hospitals. PARTICIPANTS: A consecutive sample of 2,435 unselected ICU admissions following coronary artery by-pass surgery. MATERIALS AND METHODS: Demographic, operative characteristics and APACHE III score were collected during the first postoperative day; and APACHE III scores and therapeutic interventions during the first three postoperative days. Hospital survival and ICU length of stay were also recorded. Multivariate equations were derived and cross-validated to predict hospital mortality, ICU length of stay, and ICU resource use. RESULTS: Unadjusted hospital mortality rate was 3.9% (range 1.0% to 6.0%), mean ICU length of stay was 3.7 days (range 3.2 to 4.7 days), and first 3-day ICU resource use (TISS points) was 99 (range 68 to 116). The range of actual to predicted ICU length of stay varied from 0.86 to 1.26; and resource use from 0.71 to 1.16. CONCLUSIONS: A limited number of operative characteristics, the post-operative acute physiology score (APS) of APACHE III and patient demographic data can predict hospital death rate, ICU length of stay, and resource use immediately following coronary by-pass surgery. These estimates may compliment assessments based on pre-operative risk factors in order to more precisely evaluate and improve the efficacy and efficiency of cardiovascular surgery.

The economic and clinical efficiency of point-of-care testing for critically ill patients: a decision-analysis model.

Our study objective was to assess economic and clinical outcomes of use of a point-of-care (POC) blood analysis device for postoperative coronary artery bypass graft (CABG) patients. A decision analytic model was developed for patients with high expected use of blood analysis, high potential benefit from rapid turn around time of results, a large annual volume of patients, and substantial expense associated with surgery. Published literature and clinical experts provided incidence, outcome, and cost estimates associated with four clinical scenarios potentially influenced by POC testing (ventricular arrhythmias, cardiac arrest, severe postoperative bleeding, and iatrogenic anemia). We found that changes in clinical outcomes were predominantly dependent on comparative turn around time or CABG patient volume. The positive clinical impact of using POC testing was consistently associated with a positive economic impact. POC blood gas analysis may be associated with decreased incidence of adverse clinical events or earlier detection of such events, resulting in significant cost savings. This study also supports previous findings that the costs of STAT blood analysis are more personnel-related than equipment-related.

Hypertension in the surgical patient: management of blood pressure and anesthesia.

Although hypertension has always been a high risk factor during anesthesia and surgery, risk can be reduced by preoperative control of blood pressure, evaluation of the patient to determine risk factors that can exacerbate blood pressure rises, and continuation of preoperative antihypertensive therapy. Patient hemodynamics must be monitored to manage blood pressure fluctuations and signs of ischemia as early as possible. Selection of anesthetic and adjuvant agents must be tailored to the patients, the agents must be administered carefully and in a timely fashion, and the anesthesiologist must be aware of the relevant variables. Increased knowledge of the pathophysiology of hypertension, antihypertensive therapy, and the development of new anesthetics and muscle relaxants with minimum hemodynamic effects has helped minimize complications related to perioperative hypertension.

Severity of illness: APACHE II analysis of an ICU population.

We reviewed the population of a surgical intensive care unit from July 1, 1987 to June 30, 1988, adjusting for severity of illness using the APACHE II system. Nineteen different departments admitted a total of 613 patients to the surgical intensive care unit. Predicted mortality was 22.9%; actual mortality was 15.7%. APACHE II generated reports which included analysis by age, mortality risk, department, primary physician, and diagnosis. We recommend reporting intensive care unit outcome by APACHE criteria to allow more meaningful comparisons of data and standardization of quality assurance programs. Finally, we present a critical review of the current APACHE II system and describe developments to be included in APACHE III.