Preoperative cardiac assessment of the thoracic surgical patient.

The preoperative cardiac assessment of the thoracic patient differs very little from the assessment of any patient for noncardiac surgery, aside from a few special issues. Therefore, rather than reviewing the general issue of evaluation for noncardiac surgery, which is a topic that has been reviewed many times in the recent past, this article focuses on the purposes, methods, and limitations of risk assessment in the noncardiac surgical patient with suspected coronary artery disease (CAD), including thoracic surgical patients. Because risk assessment is imprecise and the main indications for invasive coronary procedures prior to noncardiac surgery are the same for any person for whom life-expectancy is expected to be prolonged, meticulous preoperative evaluation for CAD is not usually warranted, even for patients undergoing high-risk surgery or with multiple risk factors for CAD. To help understand this point of view and to utilize cardiology consultants appropriately, implications of basic pathophysiology as well as statistical principles are also discussed.

Detection of pooled secretions above endotracheal-tube cuffs: value of plain radiographs in sheep cadavers and patients.

OBJECTIVE: Mechanical ventilation is thought to increase the risk of nosocomial pneumonia by permitting leakage of bacteria-laden gastro-oropharyngeal secretions into the upper airways. The goal of this study was (a) to validate radiographic signs of pooled secretions above endotracheal-tube cuffs (supracuff liquid) in an animal model and (b) to determine whether suctionable pooled supracuff liquid can be identified on bedside radiographs of intubated patients. MATERIALS AND METHODS: Diagnostic criteria for supracuff liquid were initially validated by three radiologists interpreting 162 randomized radiographs made in an intubated sheep cadaver. The primary criteria included (a) replacement of the normal supracuff lucency with liquid opacity and (b) the formation of a sharp interface between the lucency of the upper edge of the cuff below and the liquid above. Graded infusions of 0, 3, 8, 13, and 23 ml of saline were made in triplicate into the space above the cuff, and radiographs were evaluated for the presence or absence of saline. The validated diagnostic criteria were used by two radiologists to estimate the frequency with which pooled liquid was seen on portable chest radiographs of 47 patients undergoing elective short-term postanesthetic mechanical ventilation. RESULTS: In the sheep-cadaver model, the diagnostic criteria for supracuff liquid allowed successful differentiation between no liquid, a small amount of liquid (3-8 ml), and a large amount of liquid (13-23 ml; c2, p < .0001). In a clinical study, radiographic signs of supracuff liquid were identified in 57% of 47 patients. In a small subset of patients (n = 18), the estimated liquid volume (mean +/- SEM) was calculated to be 7.8 +/- 1.1 ml (range = 2.1-18.4 ml). CONCLUSIONS: Radiography is a sensitive means of identifying small volumes of supracuff liquid above the inflated cuffs of endotracheal tubes. Potentially contaminating liquid pooled above the cuff of an endotracheal tube can be identified in about half of patients undergoing short-term mechanical ventilation. Our results suggest the suction of the supracuff space may be a reasonable prophylactic maneuver against nosocomial pneumonia. A much larger study is suggested to investigate the actual relation between pooled supracuff liquid and the development of nosocomial pneumonia.

Warm and cold blood cardioplegia. Comparison of myocardial function and metabolism using 31p magnetic resonance spectroscopy.

BACKGROUND: Standard myocardial protection during cardiac surgery uses hypothermic arrest, but warm heart surgery, recently introduced, is now used in many centers. We hypothesized that warm continuous blood cardioplegia (WCBC) would provide better myocardial preservation than cold continuous blood cardioplegia (CCBC). METHODS AND RESULTS: In isolated cross-perfused canine hearts, left ventricular (LV) function and myocardial O2 consumption (MVO2) were measured at constant LV volume, coronary perfusion pressure, and heart rate before and after 75 minutes of arrest at 37 degrees C or 10 degrees C. Metabolism was evaluated by 31P nuclear magnetic resonance spectroscopy. LV resting tone increased transiently after arrest by CCBC but not WCBC (38 +/- 3.9 versus 2.9 +/- 0.5 mm Hg, P < .0005). Myocardial ATP changed over time differently in the groups (P < .001), declining at the outset of CCBC and returning to control levels during the recovery period after CCBC or WCBC. Intracellular pH rose from 7.17 +/- 0.03 to 7.85 +/- 0.05 during CCBC (P < .0005 versus WCBC). MVO2 declined dramatically during arrest at either temperature but to a lower value during CCBC (P < .0005). LV pressure recovered to 86.1 +/- 5.1% of its prearrest value after CCBC and to 97.2 +/- 7.8% following WCBC (P = NS). After CCBC but not WCBC, there were small but significant increases in LV end-diastolic pressure (by 1.3 mm Hg, P < .05) and in the LV relaxation constant, tau (from 37.3 +/- 1.5 to 42.3 +/- 2.4 milliseconds, P < .05). CONCLUSIONS: The increase in intracellular pH during CCBC is largely accounted for by physicochemical factors. Group differences in ATP over time may be related to rapid cooling contracture during CCBC. The data suggest that CCBC mildly impairs LV function but that WCBC preserves function and metabolism at or near prearrest levels.

Noninvasive, real-time monitoring of renal function during critical care.

The inadequacy of the current techniques to monitor renal function has been the most important limitation for determining the appropriateness of a particular form of therapy in acute renal failure. The objective of this study was to determine the advantage offered by a new method of accurate, noninvasive, and real-time monitoring of renal function during the critical care of patients. A radiation detector attached to a miniature data logger was used to monitor the clearance of the glomerular filtration agent 99mTc-diethylene triamine pentaacetic acid from the extracellular space in 20 patients admitted into an intensive care unit. The rate constant for this clearance was calculated online from 5-min epoch lengths of activity versus time. Changes in this constant were compared with changes in plasma creatinine and timed urine output. The results showed that the ambulatory renal monitor could accurately measure rapid changes in renal function during the critical care of patients who are at risk of acute renal failure with a resolution time of 5 to 10 min. The sensitivity and specificity of the technique are also superior to plasma creatinine and urine output because it can detect minimal and transient changes in renal function that otherwise may have gone undetected by these parameters. This unique approach should allow for the immediate institution and/or adjustment of the appropriate therapeutic procedure to preserve or improve the renal function.

Norepinephrine increases the economy of pressure development in isolated canine hearts.

To test for oxygen wasting by norepinephrine (NE) without relying on normalization by measures of performance such as the pressure-volume area, myocardial oxygen consumption (MVO2) was determined for isovolumic beats at five different left ventricular (LV) end-diastolic volumes (EDV) in nine isolated cross-perfused canine hearts in each of three states: a basal anesthetic state (B); after depression with halothane (H); and after adding NE to increase contractility back to the B state (H+NE). The end-diastolic and peak systolic pressure-volume lines were identical for B and H+NE. The R2 for a linear regression of MVO2 per beat for B vs. H+NE for beats originating at the same EDV and developing similar (within 10%) peak isovolumic pressures for all hearts was 0.85. The slope and intercept were 0.83 and 0.01, which are significantly less than one (P less than 0.001) and greater than zero (P less than 0.001), respectively. These data suggest that NE increases both the economy of pressure development as well as activation energy of an isovolumically contracting LV.

Transperitoneal versus retroperitoneal approach for aortic reconstruction: a randomized prospective study.

A prospective, randomized study was conducted to compare the retroperitoneal versus transperitoneal approach for elective aortic reconstruction. One hundred thirteen patients (transperitoneal = 59, retroperitoneal = 54) were randomized between March 1987 and October 1988. In addition, to assess the changing course of patients undergoing aortic reconstruction similar data were gathered retrospectively on a group of 56 patients undergoing aortic reconstruction by the same surgeons performed via a transperitoneal approach in 1984 to 1985. Randomized patients were identical in age, male to female ratio, smoking history, incidence and severity of cardiopulmonary disease, indication for operation, and use of epidural anesthetics. Details of operation including operative and aortic cross-clamp times, crystalloid and transfusion requirements, degree of hypothermia on arrival at the intensive care unit, and perioperative fluid and blood requirements did not differ significantly for patients undergoing transperitoneal versus retroperitoneal reconstruction. Respiratory morbidity, as assessed by percent of patients requiring postoperative ventilation, deterioration in pulmonary function tests, and the incidence of respiratory complications, was identical in randomized patients. Other aspects of postoperative recovery including recovery of gastrointestinal function, the requirement for narcotics, metabolic parameters of operative stress, the incidence of major and minor complications, and the duration of hospital stay were similar for randomized patients undergoing transperitoneal and retroperitoneal reconstruction. When compared to retrospectively reviewed patients having aortic reconstruction, randomized patients undergoing transperitoneal and retroperitoneal operations had highly significant (p less than 0.001) reductions in postoperative ventilation, transfusion requirements, and length of hospital stay. Such trends were all independent of transperitoneal versus retroperitoneal approach.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular, pulmonary, and renal effects of massively increased intra-abdominal pressure in critically ill patients.

Massive elevation of intra-abdominal pressure (IAP) causes cardiovascular, respiratory, and renal dysfunction. We managed eight patients with high IAP (mean 51 +/- 7 cm H2O), six of whom had hemodynamic measurements; a clinical syndrome, characterized by hemodynamic, respiratory, and renal dysfunction, then became apparent. We report a) a baseline cardiopulmonary profile and response to an acute vascular volume challenge in six patients and b) surgical decompression of the abdomen in four patients. The clinical impression of hypovolemia was confused by small to normal left ventricular end-diastolic volume (64 +/- 14 ml) and normal ejection fraction (55 +/- 6%) despite very high right and left atrial filling pressures. Complete ventilatory support was necessary to maintain oxygenation and ventilation; oliguria (urine output less than 10 ml/h) was present. Pericardial effusion was absent. After fluid challenge (10 ml/kg of colloid or crystalloid infused iv over 10 min), filling pressures, cardiac output, and stroke volume all increased significantly (p less than .025) while heart rate decreased. Surgical decompression of the abdomen improved oxygenation, ventilation, cardiac output, atrial filling pressures, and urine output within 15 min. The cardiovascular effects of massively elevated IAP compounded by the requisite supportive care may require surgical relief.

Effect of labetalol or lidocaine on the hemodynamic response to intubation: a controlled randomized double-blind study.

Labetalol, a combined alpha 1- and nonselective beta-adrenergic blocking drug, was compared to lidocaine or saline to minimize the hypertensive and tachycardic response to intubation in a controlled randomized double-blind study in patients undergoing surgical procedures under general anesthesia. Forty adult patients were divided into four groups of 10 each: placebo (saline), lidocaine 100 mg, labetalol 5 mg, or labetalol 10 mg. The double-blind preparation was administered as an IV bolus just prior to induction and 2 min before the stimulus of laryngoscopy and intubation. Heart rate and blood pressure were measured at 1-min intervals for 2 min prior to induction of anesthesia and through 6 min following induction of anesthesia. Labetalol 10 mg prevented a rise in heart rate after intubation compared to patients who received placebo, lidocaine 100 mg, or labetalol 5 mg. The hypertensive response to intubation was similar in all four groups. Labetalol 10 mg IV just prior to induction of anesthesia is a safe and cost-effective means of preventing tachycardia but not hypertension in response to laryngoscopy and intubation.

Zero stability of disposable and reusable pressure transducers.

Zero stability tests were performed on contrasting, commercially available, blood pressure-transducer systems. One system was based on a brand of disposable transducer. The others employed one brand of reusable transducer with and without samples of two different brands of compatible disposable domes. Drift was measured at atmospheric pressure over 3-hr periods. Drifts with the disposable transducers and with the bare reusable transducers were small, ranging from -2 to +2 mm Hg over 3 hr. However, the drifts of the reusable transducers with domes were significantly greater, ranging from -11 mm to +5 mm Hg. The disposable transducers did not drift significantly after the first half hour, although the reusable transducers with domes continued to drift. In addition, one brand of disposable dome produced inaccurate calibrations with the reusable transducer. The methodology of drift measurement and analysis should be practical and useful in other settings and with other brands of transducers. In general, the results indicate that periodic zeroing is still a clinically important procedure, and it is a worthwhile effort prior to treatment decisions based on pressure readings.

Prediction of outcome in acute renal failure.

In an attempt to predict outcome in acute renal failure (ARF) we have utilized multiple logistic regression to analyze clinical data from 151 patients with ARF seen over a 15-month period. Recovery of renal function occurred in 60% of patients with a 58% survival. Our analysis demonstrated sepsis, respiratory failure, and oliguria to be the major predictors of nonrecovery of renal function. A logistic equation was generated for prediction of outcome and was validated in a second independent group of patients with ARF. Prediction of outcome could be achieved with a sensitivity of 75% and a specificity of 80%. Maximum sensitivity (100%) was associated with a 17% specificity, while maximum specificity (98%) yielded a sensitivity of 20%.

Time dependence of the oxygen cost of force development during systole in the canine left ventricle.

To determine whether the oxygen cost of force development in the canine left ventricle is constant throughout systole, we inserted fluid-filled Latex balloons into eight isolated canine left ventricles perfused via support dogs. Balloon volumes were varied by a hydraulic servoactuator designed to withdraw preset volumes rapidly (0.5 ml/msec) beginning at a specified ejection pressure. Oxygen consumption was related to force-time integrals for 9-12 different ejections patterns formed by ejecting three or four different volumes from the same end-diastolic volume, each ejection beginning at three different pressures, isovolumic beats with four or five different end-diastolic volumes, including those used for the ejections. The force-time integral vs. oxygen consumption data are nonlinear for ejections that began at low pressures, with oxygen consumption exceeding that predicted from regression lines fitted to the isovolumic data. This difference appeared to peak at relatively low force-time integrals and then curve back to converge with the isovolumic line. This pattern was not evident for ejections that began late in systole. Although these results suggest that the energy required for force development is greater than expected early in systole, they also are consistent with the hypothesis that oxygen consumption is a function only of instantaneous ventricular volume.

Effect of preload on ischaemic and non-ischaemic left ventricular regional function.

The response to preload of ischaemic and non-ischaemic regions of the left ventricle was studied in 14 dogs undergoing right heart bypass with mean aortic pressure and heart rate held constant. Regional function was measured by sonomicrometry before and after coronary artery occlusion. In the ischaemic region, as expected, there was paradoxical systolic lengthening (that is, systolic shortening was negative) but as stroke volume was progressively increased end diastolic length increased, whereas end systolic length changed little; thus systolic lengthening decreased (systolic shortening increased). Ischaemic regions that were dyskinetic at low stroke volumes were virtually akinetic at high stroke volumes. Additional studies showed that this response was not attributable to increased regional blood flow at high preloads and occurred over a wide range of heart rates and mean aortic pressures. Plots of systolic shortening against end diastolic length, expressing the regional Frank-Starling relation, were well described by linear regression in both ischaemic and non-ischaemic regions, although a few of these relations were better described by higher order polynomials. The slopes of these relations in the ischaemic region were 0.86(0.05) before and 0.83(0.06) after ligation, reflecting a small effect of preload on end systolic length. The data suggest that when contractility and afterload are constant preload determines the magnitude and in certain instances the sign of systolic shortening. In any ischaemic regions incapable of developing force the positive slope of the Frank-Starling relation is attributable to myocardial passive elastic properties. Paradoxical lengthening does not, however, necessarily indicate the absence of active force development; positive and negative values of systolic shortening describe a continuous spectrum of regional contractility. Thus the effects of preload and contractility on systolic shortening in ischaemic as well as non-ischaemic myocardium require differentiation.

Myocardial recovery after hypothermic arrest: a comparison of oxygenated crystalloid to blood cardioplegia. The role of calcium.

We compared multidose crystalloid hyperkalemic cardioplegic solutions with and without added red cells in 24 canine hearts subjected to 5 hr of arrest at 10 degrees C. All cardioplegic solutions were fully oxygenated at 4 degrees C before delivery. Since blood cardioplegia contained Ca++ carried over with the red cells, Ca++ was added to the crystalloid solution in one group. The table below shows the hematocrit (HCT) and ionized Ca++ concentrations of the cardioplegic solutions, and coronary arteriovenous oxygen difference during infusion of cardioplegic solution (AVO2) (ml O2/100 ml). Recovery during reperfusion is shown as percent of prearrest left ventricular function (LVF) and prearrest myocardial ATP concentration.

Reduction of postischemic myocardial dysfunction by substrate repletion during reperfusion.

We studied the effect of selected metabolic substrates on recovery of myocardial function and ATP concentration when added to the reperfusate after normothermic ischemia. The hearts of 30 anesthetized, open-chest mongrel dogs were subjected to 45 min of global ischemia at 37 degrees C followed by 90 min of reperfusion. Left ventricular function curves were generated on right heart bypass before and at 30 min intervals after the ischemic period. ATP concentration was measured before, at the end of, and 90 min after the ischemic period. Experiments were randomized into five groups distinguished by the content of the myocardial reperfusate during the first 10 min of the reperfusion period. Hearts received either unmodified oxygenated pump blood (control; group I), normothermic oxygenated 28 mmol/liter potassium-blood cardioplegic solution (KBC; group II), 25 mmol/liter glutamate in KBC (group III), 250 mumol/liter adenosine with 1 mg erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride (EHNA) and glutamate in KBC (group IV), or 2 mmol/liter ribose and glutamate (group V) in KBC. Hearts reperfused with KBC showed improvement early (group II vs group I; p less than .02) but not late recovery of left ventricular function over control. Glutamate, which replenishes Krebs cycle intermediates lost during ischemia, increased functional recovery (group III vs group II; p less than .002). Ribose, which is important in purine salvage and resynthesis, added to glutamate-KBC further improved functional recovery (group V vs group III; p less than .01). Adenosine, a precursor of ATP, with EHNA, an inhibitor of rapid adenosine catabolism, added to glutamate-KBC depressed early recovery (group IV vs group III; p less than .01); however, recovery improved with time. Both glutamate and ribose with glutamate in KBC improved ATP recovery (groups III and V vs group II; p less than .002). Thus selective substrate repletion during initial reperfusion after severe normothermic ischemia can improve recovery of myocardial function and ATP concentration.

Diazepam-fentanyl interaction--hemodynamic and hormonal effects in coronary artery surgery.

Diazepam has been reported to produce hypotension when administered with anesthetic doses of fentanyl. Twenty patients undergoing coronary bypass surgery were randomly assigned to one of four treatment groups: group 1, no diazepam; groups 2, 3, and 4, 0.125, 0.25, and 0.5 mg X kg -1 of diazepam, respectively. All patients then received 50 micrograms X kg -1 fentanyl at 400 micrograms X min -1 and 0.4 mg X kg -1 metocurine at 2 mg X min -1. Hemodynamic parameters were recorded and blood was sampled for measurement of plasma catecholamine and histamine concentrations. Heart rate, cardiac index, stroke volume index, central venous pressure, pulmonary arterial and wedge pressures, and pulmonary vascular resistance did not change significantly in any group. Patients in groups 2-4 had significant decreases in mean arterial pressure and systemic vascular resistance during fentanyl infusion. These hemodynamic changes were accompanied by decreases in plasma epinephrine and norepinephrine levels. These hemodynamic and hormonal changes did not occur in patients given fentanyl only. Plasma histamine levels did not change significantly in any group. Caution should be used when diazepam in doses as small as 0.125 mg X kg -1 are combined with high-dose fentanyl anesthesia.

Benefit of elective intensive care admission after certain operations.

To determine if patients who have undergone uneventful vascular surgery (VS), nonvascular intracranial surgery (ICS), or anterior cervical laminectomies (ACL) have enough serious postoperative problems to justify routine overnight observation in an intensive care unit (ICU), we recorded every problem and associated therapy administered to 263 such patients within 36 h of ICU admission. The severity of each treated problem was graded from 1 (safe to delay treatment for at least 2 h) to 4 (life-threatening, immediate treatment required). Defining patient benefit from the ICU as treatment for one grade 4 problem or more than one grade 3 problem, 44% of VS patients (N = 177), 14% of ICS patients (N = 73), and none of the ACL patients (N = 13) benefited. We conclude that these percentages justify an overnight ICU stay for all VS patients, especially as the occurrence of serious problems was unpredictable and most serious problems were still being treated 4 h postoperatively. Furthermore, routine ICU admission of all patients in the groups studied would reduce patient costs if only 13 of the 88 patients who benefited were prevented from becoming critically ill.