Bruce Kleinman

Angina and other risk factors in patients with cardiac diseases undergoing noncardiac operations.

Six hundred eighty-eight consecutive patients with cardiac diseases or who wer, ′older than 70 yr of age, all of whom were undergoing noncardiac operations, were studied. Twenty-four preopeiative risk factors were analyzed for the outcome of perioperative myocardial infarction (PMI) or cardiac death using stepwise logistic regression. Old age, emergency operation, angina, previous myocardial infarction, electrocardiographic signs of ischemia, type of surgical procedure, and hypokalemia were identified as individual factors useful in predicting outcome. Thirty-two patients (4.65%) developed PMI. Seven of these 32 patients (21.9%) and eight more patients without PMI—a total of 15 patients (2.2%)—died a cardiac death. Nonfatal but serious complications occurred in 23% of the patients. Patients undergoing emergency operations and patients with chronic stable angina, previous myocardial infarction, and electrocardio- graphic signs of ischemia were found to be at increased risk for PMI and cardiac death.

Reevaluation of perioperative myocardial infarction in patients with prior myocardial infarction undergoing noncardiac operations

We studied 275 patients with prior myocardial infarctions undergoing noncardiac operations to determine the incidence and outcome of perioperative myocardial reinfarction. Perioperative myocardial reinfarction developed in 13 patients (4.7%) of whom 3 (23%) died of cardiac causes. When time between prior myocardial infarction and the date of anesthesia was analyzed, the incidence of perioperative myocardial reinfarction was 4.3% at 0–3 mo, 0 at 4–6 mo, 5.7% at >6 mo, and 3.3% at an indeterminate exact interval. None of the variables analyzed showed any significant correlation with the rate of reinfarction. The urgency of operation and aortic or vascular procedures were the only variables that approached, but failed to achieve, statistical significance.

Effect of Prone Positioning Systems on Hemodynamic and Cardiac Function During Lumbar Spine Surgery: An Echocardiographic Study

Study Design. Prospective randomized study of patients undergoing spine surgery. Objective. To compare changes in hemodynamic and cardiac function after prone positioning using different prone positioners. Summary of Background Data. Prone positioning decreases blood pressure and cardiac function. Several studies have evaluated changes in cardiac function after prone positioning, and linked them to reduced venous return and ventricular compliance. This study compares different prone positioners using transesophageal echocardiography, and determines their effect on cardiac function and hemodynamics. Methods. After correction of fluid deficits with the patient under stable anesthesia, hemodynamic and cardiac performance was measured using transesophageal echocardiography. After prone positioning, repeat measurements were performed, and comparisons were made between prone and supine positions. Results. No intergroup differences in demographics, fluid deficit, baseline hemodynamics, or differences from supine to prone position were noted. Cardiac output decreased with the Wilson (Union City, CA) and Siemens AG (Munich, Germany) frames, while cardiac index and stroke volume decreased with the Andrews (Hollywood, CA), Wilson, and Siemens systems. Cardiac preload decreased using the Andrews frame. The Jackson spine table (Hollywood, CA) and bolsters had the least effect on cardiac performance. Conclusion. Adequate fluid replacement reduced hypotension and hemodynamic instability after prone positioning. The Jackson spine table and longitudinal bolsters had minimal effects on cardiac function, and should be considered in patients with limited cardiac reserve.

The fast flush test measures the dynamic response of the entire blood pressure monitoring system

The fast flush test (FT) is the only test that allows clinicians to determine in vivo the natural frequency (fn) and damping coefficient (zeta) of an invasive blood pressure monitoring system. The underlying assumption to the validity of the FT is that it activates the whole system including the distal catheter. We devised an in vitro model of a typical invasive blood pressure monitoring system to determine whether this assumption was true. The model consisted of a conventional transducer with a flush device attached to various lengths of connecting tubing (91.4, 182.9, and 274.3 cm) terminated by four different diameter catheters (5.1 cm 14 G, 16 G, 18 G, and 20 G). A microtipped transducer catheter was inserted into the distal catheter tubing system. A FT was performed and the fn and zeta were recorded from the conventional transducer and simultaneously from the microtipped transducer catheter. Similar studies were conducted using the ROSE damping device as well as with systems including 0.1 ml of air near the conventional transducer. These studies utilized 18- and 20-G catheters with each of the three lengths of connecting tubing. All measurements of fn and zeta at the proximal conventional transducer were identical to those measurements as recorded by the distal microtipped transducer catheter. We conclude that the FT activates the whole monitoring system and that fn and zeta are the same throughout the system including the distal catheter.

The relative increase in skin temperature after stellate ganglion block is predictive of a complete sympathectomy of the hand

Background and Objectives. Although an increase in skin temperature of the hand implies sympathetic block after stellate ganglion block (SGB), it does not indicate complete sympathetic block unless accompanied by an absence of sweating because skin temperature may increase even with a partial sympathetic block. This study examined the efficacy of the SGB to block sweating in the hand and to determine if the magnitude of temperature change in the hand is predictive of a negative sweat test. Methods. Fifty‐nine SGBs were performed in 30 patients (15 women and 15 men) for diagnostic or therapeutic indications. Stellate ganglion block was performed via an anterior paratracheal approach at C6 using 15 mL 0.25% bupivacaine. Skin temperature was measured bilaterally on the index finger. A cobalt blue sweat test was performed bilaterally preand post‐SGB on the middle finger. Successful sympathetic block after SGB was considered present when: (a) (change in ipsilateral temperature (postblock‐preblock)] (Di)‐ [change in contralateral temperature] (Dc) ≥ 1.5°C; (b) Horners syndrome present; and (c) sweat test changed from positive to negative. Logistical regression was applied to determine what value of Di ‐ Dc could be used to predict a negative sweat test. Results. Thirty‐six percent (21/59) of blocks met all three criteria. Of the blocks where Di ‐ Dc ≥ 1.5°C, 72% (21/29) had a negative sweat test post‐SGB. Of the blocks where Di ‐ Dc < 1.5°C, 37% (11/30) had a negative sweat test postblock. If Di ‐ Dc ≥ 2.0°C, a negative sweat test could be predicted with 69 ± 12% sensitivity and 85 ± 10% specificity. Conclusions. Stellate ganglion block often fails to increase skin temperature in the ipsilateral more than the contralateral hand. A value of Di ‐ Dc ≥ 2.0°C was a good predictor of a sympathetic block, but was not sufficient to guarantee a complete sympathetic block of the hand after SGB in all cases. An apparently successful SGB as measured by “usual” clinical criteria may not result in a complete sympathectomy of the hand as is often assumed. Therefore, if obtaining a sympathectomy is important for diagnostic or therapeutic purposes, performing a sweat test provides important confirmatory evidence of the genuine success of the sympathetic block.

Motion of the Diaphragm in Patients with Chronic Obstructive Pulmonary Disease while Spontaneously Breathing versus during Positive Pressure Breathing after Anesthesia and Neuromuscular Blockade

Background Diaphragmatic excursion during spontaneous ventilation (SV) in normal supine volunteers is greatest in the dependent regions (bottom). During positive pressure ventilation (PPV) after anesthesia and neuromuscular blockade and depending on tidal volume, the nondependent region (top) undergoes the greatest excursion, or the diaphragm moves uniformly. The purpose of this study was to compare diaphragmatic excursion (during SV and PPV) in patients with chronic obstructive pulmonary disease (COPD) with patients having normal pulmonary function. Methods Twelve COPD patients and 12 normal control subjects were compared. Cross-table diaphragmatic fluoroscopy was performed while patients breathed spontaneously. After anesthetic induction and pharmacologic paralysis and during PPV, diaphragmatic fluoroscopy was repeated. For analytic purposes, the diaphragm was divided into three segments: top, middle, and bottom. Percentage of excursion of each segment during SV and PPV in normal subjects was compared with the percentage of excursion of each segment in patients with COPD. Results There was no significant difference in the pattern of regional diaphragmatic excursion (as a percentage of total excursion)—top, middle, bottom—when comparing COPD patients with control subjects during SV and PPV. In the control subjects, regional diaphragmatic excursion was 16 ± (5), 33 ± (5), 51 ± (4) during SV and 49 ± (13), 32 ± (6), 19 ± (9) during PPV. In COPD patients, regional diaphragmatic excursion was 18 ± (7), 34 ± (5), 49 ± (7) during SV and 47 ± (10), 32 ± (6), 21 ± (9) during PPV. Conclusion Regional diaphragmatic excursion in patients with COPD during SV and PPV is similar to that in persons with normal pulmonary function.

Myocardial metabolism and adaptation during extreme hemodilution in humans after coronary revascularization

ObjectiveThis study was designed to evaluate the oxygen transport adjustments and myocardial metabolic adaptation that occurs with different levels of hemodilution during normothermia after cardiopulmonary bypass. DesignProspective, nonrandomized study. SettingOperating room in a university hospital. PatientsEight patients with ejection fractions (>40%) undergoing elective coronary artery bypass grafting. MethodsBefore the institution of cardiopulmonary bypass, blood was withdrawn from patients to a target hematocrit of 15%. After coronary artery bypass grafting, a catheter was inserted directly into the coronary sinus. After the patients were rewarmed to 37°C, they were weaned from cardiopulmonary bypass. Hemodynamic indices were measured, as well as measurements of myocardial oxygen consumption (Vo2) and myocardial metabolism (lactate extraction and coronary sinus hypoxanthine). Measurements were made at three different hematocrit values: 15%, 20%, and 25%. Hematocrit was increased by autologous blood transfusion. Measurements and Main ResultsThe three levels of hemodilution (hematocrit: 17.4 ±PT 3.4%; 23.0 ±PT 3.7%; 27.8 ±PT 4.8%) were significantly different from baseline (hematocrit 37 ±PT 2.6%; p <.05). Oxygen delivery, which increased with autologous transfusion, exceeded 350 mL/min/m2 at each level of dilution. The myocardial Vo2 increased significantly after autologous transfusion compared with the most dilute condition (7.0 ±PT 3.7 mL/min at hematocrit 17.4% vs. 11.2 ±PT 4.8 mL/min at hematocrit 23.0% and 12.4 ±PT 4.0 mL/min at hematocrit 27.8%). This transfusion-induced increase was also true of myocardial oxygen extraction. Lactate extraction and hypoxanthine release were normal and unchanged at each level of hemodilution. Systemic oxygen extraction ratio increased with hemodilution and decreased with autologous transfusion. ConclusionsHemodilution to a hematocrit of approximately 15% is tolerated in anesthetized humans after coronary artery bypass surgery. There was no evidence of myocardial ischemia, as demonstrated by absence of S-T depression on the electrocardiogram, lactate extraction, or hypoxanthine release. In selected patients, postoperative transfusion may be based on systemic physiologic end-points, such as oxygen extraction ratio, rather than set hematocrit values.

Understanding natural frequency and damping and how they relate to the measurement of blood pressure

The model that describes the physical behavior of a fluid-filled catheter-transducer blood pressure monitoring system is a simple mass-spring system. When the mass is displaced and then released, there results a characteristic motion calledsimple harmonic motion. The full description of this motion requires defining the concepts of undamped and damped natural frequency, as well as of damping itself. Once these concepts are defined and the mass-spring system clearly understood, their relevance to recording blood pressure measurement by fluid-filled catheters is explained. The apparent paradox of how damping can affect undamped natural frequency is clarified. Finally, impedance matching is explained in the context of how some damping devices work. Detailed mathematical proofs are relegated to an appendix.

Qualitative evaluation of coronary flow during anesthetic induction using thallium-201 perfusion scans.

Qualitative distribution of coronary flow using thallium-201 perfusion scans immediately postintubation was studied in 22 patients scheduled for elective coronary artery bypass surgery. Ten patients received a thiopental (4 mg/kg) and halothane induction. Twelve patients received a fentanyl (100 μg/kg) induction. Baseline thallium-201 perfusion scans were performed 24 h prior to surgery. These scans were compared with the scans performed postintubation. A thallium-positive scan was accepted as evidence of relative hypo-perfusion. Baseline hemodynamic and ECG data were obtained prior to induction of anesthesia. These data were compared with the data obtained postintubation. Ten patients developed postintubation thallium-perfusion scan defects (thallium-positive scan), even though there was no statistical difference between their baseline hemodynamics and hemodynamics at the time of intubation. There was no difference in the incidence of thallium-positive scans between those patients anesthetized by fentanyl and those patients anesthetized with thiopental-halothane. The authors conclude that relative hypoperfusion, and possibly ischemia, occurred in 45% of patients studied, despite stable hemodynamics, and that the incidence of these events was the same with two different anesthetic techniques.

Radiographic pulmonary abnormalities after different types of cardiac surgery

One aim of this study was to determine the incidence of new radiographic pulmonary abnormalities during hospitalization after cardiac surgery. Another aim was to determine if such abnormalities are more common among patients who had left internal mammary artery (LIMA) grafting. The predictive value of radiographic abnormalities for clinically important pulmonary morbidity was also determined. The anteroposterior chest radiographs of 152 patients obtained by portable equipment were evaluated to determine the incidence of new postoperative radiographic pulmonary abnormalities such as atelectasis, consolidation, infiltrate, and pleural effusion. Clinically important pulmonary morbidity was defined as a delay in tracheal extubation or discharge from the hospital because of a pulmonary reason. Among the 89 patients who had LIMA grafting and left pleurotomy, there was an 88% incidence of left-sided pulmonary abnormalities; a 73% incidence of left-sided atelectasis; and a 55% incidence of left-sided effusion. Among the 63 patients who had saphenous vein grafting only and/or valvular surgery, the respective incidences were 68%, 54%, and 35%, which were lower (P less than or equal to 0.05) than those in the patients who had LIMA grafting. There was no significant difference in abnormalities between the saphenous vein grafting and the valvular surgery groups. The 35% incidence of left-sided pleural effusion when LIMA grafting and pleurotomy were not performed was unexpectedly high. There was no association between radiographic abnormalities and age, the duration of cardiopulmonary bypass, and the duration of aortic occlusion, indicating that cardiopulmonary bypass was not a primary etiology of these radiographic abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)