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Biomedical subjects

B Kleinman

Publications and source records attributed to B Kleinman.

At least 19 recordsLinked to original sources
PubMed1999

A collaborative regional ocular anesthesia training program: successes and failures.

STUDY OBJECTIVE: To describe a collaborative effort of the departments of ophthalmology and anesthesiology to teach anesthesiology residents regional ocular anesthesia; to detect any differences in positive or negative outcomes after blocks performed by anesthesiology residents versus blocks performed by ophthalmology residents. DESIGN: Prospective descriptive, study. SETTING: Outpatient surgery in a university-affiliated veterans affairs hospital. PATIENTS: 614 patients requiring elective ocular surgery. INTERVENTIONS: Outcomes from patients who underwent regional anesthesia performed by ophthalmology residents were compared to outcomes from patients who received anesthesia from anesthesiology residents. MEASUREMENTS AND MAIN RESULTS: A detailed description of the collaborative teaching program in ocular anesthesia is presented. Ophthalmology residents performed the majority of regional ocular blocks (87% vs. 13%). There was no statistical difference in the incidence of negative outcomes, such as retrobulbar hemorrhage, between ophthalmology residents and anesthesiology residents (3/534 vs. 1/80) or in the incidence of successful blocks (90% for ophthalmology residents vs. 88% for anesthesiology residents). CONCLUSIONS: Regional ocular anesthetic techniques can be safely and successfully taught to residents in anesthesiology.

Ambulatory Surgical Procedures↗
PubMed1998

Does the choice of anesthetic technique affect the recovery of bowel function after radical prostatectomy?

OBJECTIVES: Return of bowel function after radical prostatectomy surgery may be the limiting factor in discharging these patients from the hospital. Recent studies have shown that postoperative epidural infusion of bupivacaine decreases time to return of bowel function compared with intravenous and epidural morphine in patients after abdominal surgery. This study focuses on the role of the intraoperative anesthetic technique on recovery of bowel function, intraoperative blood loss, and the incidence of postoperative deep venous thrombosis (DVT) in patients undergoing radical retropubic prostatectomy and pelvic lymphadenectomy. METHODS: Forty patients undergoing prostatectomy were randomized to either group A (general endotracheal anesthesia, including muscle relaxation and mechanical ventilation, followed by postoperative intravenous morphine patient-controlled analgesia) or group B (thoracic epidural anesthesia using bupivacaine, combined with "light" general anesthesia using a laryngeal mask airway and spontaneous ventilation, followed by epidural morphine analgesia). Intra- and postoperative data were collected on blood loss, volumes of crystalloid and colloid infused, blood transfused, duration of anesthesia and surgery, anesthetic and surgical complications, time to recovery of bowel function, quality of postoperative pain control, and time to discharge from hospital. Each patient underwent lower extremity venous ultrasonography to detect DVT. RESULTS: Twenty-one patients received general anesthesia and 19 received combined epidural and general anesthesia. Intraoperative blood loss was significantly lower in the epidural group, and times to first flatus and first bowel movement were also shorter in this group. There were no significant differences in duration of anesthesia or surgery, quality of postoperative analgesia, side effects of analgesia, or time to discharge from hospital. There was no DVT detected in any patient. CONCLUSIONS: The combined anesthetic technique of thoracic epidural anesthesia and "light" general anesthesia with spontaneous ventilation decreased intraoperative blood loss and shortened the time to return of bowel function. However, this earlier return of bowel function was not great enough to realize a difference in time to hospital discharge. There was no evidence of increased complications secondary to epidural anesthesia or of prolonged anesthetic time necessary to place epidural catheters.

Adenocarcinoma↗
PubMed1998

Artifact mistaken for electrical interference recorded from a pulmonary artery catheter.

Artifactual signals superimposed on the electrocardiogram have been well documented [1-5]. These signals can originate from infusion pumps [1, 2], occlusion heads from cardiopulmonary bypass machines [3,4], and dialysis apparatus [5]. Artifacts on a pulmonary artery tracing, such as those produced by "catheter whip," are well described [6], and rarely if ever confuse the clinician. Extraneous electrical signals are of major concern because they pose a hazard to susceptible patients. We report a case in which the blood pressure tracing from the pulmonary artery revealed an artifact that looked at first glance like 60 cycle alternating current (AC) electrical interference. The investigation as to its origin revealed important lessons in the analysis of human error.

Artifacts↗
PubMed1998

The fast flush test--is the clinical comparison equivalent to its in vitro simulation?

OBJECTIVE: An in vitro simulation of the fast flush (FL) test has previously been used to prove that the FL test-measures the dynamic response of entire the blood pressure monitoring system. This simulation has also been used to confirm that the FL test is equivalent to the "gold standard" test for determining dynamic response, namely the square wave (SW) test. The conditions of the in vitro simulation can be reproduced in vivo during cardiopulmonary bypass (CPB) and circulatory arrest. Therefore the present objective was to verify that the previous conclusions about the validity of the FL test, obtained from an in vitro model, are equally valid when applied to in vivo clinical conditions. A secondary objective was to determine whether the patient's arterial tree has any affect on the dynamic characteristics of fluid-filled manometers. METHODS: Fourteen patients were studied during surgery that required CPB. We measured the dynamic response of the fluid filled arterial manometer during pulsatile conditions prior to the initiation of CPB, and then repeated the measurements during non-pulsatile CPB. In four of the fourteen patients we measured the dynamic response during circulatory arrest. A manometer, consisting of a fluid-filled tubing component, measured the patient's arterial blood pressure as well as the damped sinusoidal wave form created by the fast flush tests. The fluid-filled tubing was connected to a transducer (Utah Medical Products, Inc., Midvale, UT). The arterial pressures and the results of flush testing were recorded and displayed by a monitor (Marquette 7010, Marquette Electronics Inc., Milwaukee, WI). In an additional three patients we measured the dynamic response of the manometer in vitro and then in vivo. RESULTS: The dynamic response of the arterial pressure measuring system was the same during normal pulsatile flow, CPB and circulatory arrest. In addition, the dynamic response of the fluid-filled manometer was the same in vivo as in vitro. CONCLUSIONS: The clinical conditions during CPB and particularly during circulatory arrest duplicate the in vitro FL test simulation model. These results confirm the validity of the FL test in vivo as well as proving that the dynamic characteristics of a fluid-filled manometer are independent of the patient's vasculature.

Blood Pressure↗
PubMed1996

Equivalence of fast flush and square wave testing of blood pressure monitoring systems.

BACKGROUND: The accurate recording of intraarterial pressure depends upon an appropriate dynamic response of the monitoring system. Generation of a square wave (SW) at the catheter tip is the engineering and in vitro laboratory gold standard. Fast flush (FF) testing is the clinical test of choice. Results from these two test methods have been assumed equal but have not been empirically confirmed. METHODS: We studied three different 5.1 cm catheter sizes (16 G, 18 G, 20 G Becton Dickinson, Sandy, UT) attached to three different lengths of arterial pressure tubing (36 in, 91.4 cm; 72 in, 182.9 cm; 108 in, 274.3 cm). An arterial recording system was assembled in the standard fashion by attaching a catheter to arterial pressure tubing, which was attached to a transducer (TXX-R, Ohmeda, formerly Viggo-Spectramed, Oxnard, CA) whose signal was recorded by a strip chart recorder (Gould 2400, Rolling Meadows, IL). The system was attached to a pressurized saline flush. The catheter tip was inserted into one port of a pressure generator. With the other port of the pressure generator open to atmosphere, FF tests were performed by activating the flush device of the transducer. Subsequent step response signals from the FF tests were then recorded from which natural frequency (fn) and damping coefficient (zeta) were calculated. Next, square waves were generated by closing the port that was open to atmosphere and attaching a signal generator to a pressure generator. Square waves so generated were recorded as described above and natural frequency and damping coefficients calculated. These procedures were repeated after 0.05 cc of air was introduced in the transducer and repeated again in a system containing a damping device (R.O.S.E., Resonant OverShoot Eliminator, Viggo-Spectramed, Oxnard, CA). RESULTS: There was no significant difference between fn and zeta as calculated from the step response generated from the FF test versus fn and zeta as calculated from the square wave (SW) test in systems without air. However, in systems containing air, fn by FF testing was always less than fn by SW testing for all catheter sizes and extension tubing lengths (p < 0.05). Damping was also always greater by FF testing than by SW testing in systems with air for all catheter sizes and extension tubing lengths (p < 0.05). The R.O.S.E device created marked qualitative differences, although exact fn and zeta could not be quantified. CONCLUSIONS: For the characterization of dynamic response of invasive blood pressure monitoring systems, the FF test and SW test yield identical results. However, under certain conditions-air, R.O.S.E device-dynamic response as measured by FF testing was not equivalent to dynamic response as measured by the gold standard-the SW test. Specifically, small amounts of air in fluid-filled invasive blood pressure monitoring systems cause a slightly worse dynamic response as measured by FF testing versus the laboratory gold standard-the SW test.

Blood Pressure Monitors↗
PubMed1992

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.

Blood Pressure Monitors↗
PubMed1992

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

OBJECTIVE: This 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. DESIGN: Prospective, nonrandomized study. SETTING: Operating room in a university hospital. PATIENTS: Eight patients with ejection fractions (> 40%) undergoing elective coronary artery bypass grafting. METHODS: Before 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 degrees 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 RESULTS: The three levels of hemodilution (hematocrit: 17.4 +/- 3.4%; 23.0 +/- 3.7%; 27.8 +/- 4.8%) were significantly different from baseline (hematocrit 37 +/- 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 +/- 3.7 mL/min at hematocrit 17.4% vs. 11.2 +/- 4.8 mL/min at hematocrit 23.0% and 12.4 +/- 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. CONCLUSIONS: Hemodilution 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.

Blood Transfusion, Autologous↗
PubMed1991

Cardiovascular adjustments and gas exchange during extreme hemodilution in humans.

OBJECTIVE: To examine the cardiovascular adjustments and pattern of gas exchange that occur during hemodilution. DESIGN: Nonrandomized prospective study. SETTING: Operating room in a university hospital. PATIENTS: Seven patients undergoing elective aortocoronary artery bypass surgery. INTERVENTIONS: Before initiating cardiopulmonary bypass, the patients' hematocrit levels were decreased to approximately 15%. This hemodilution was done by removing a sufficient amount of autologous blood from the aortic cannula and replacing it with a sufficient amount of crystalloid solution. After the discontinuation of cardiopulmonary bypass, measurements were made at a hematocrit of approximately 15%. Then, after autologous blood infusion, measurements were made at a hematocrit of 20%, followed by more blood infusion to approximately 25% with repeat measurements. MEASUREMENTS AND MAIN RESULTS: The following measurements were made before hemodilution and then at all three levels of hemodilution: heart rate, mean arterial pressure (MAP), right atrial pressure, mean pulmonary artery pressure, pulmonary artery occlusion pressure, and cardiac output. From these measurements, the following derived variables were calculated: cardiac index, systemic vascular resistance, and pulmonary vascular resistance. From measurements of arterial oxygen content, mixed venous oxygen content, and cardiac output, intrapulmonary shunt (Qsp/Qt), oxygen uptake (VO2), oxygen extraction ratio, and oxygen delivery (DO2) were derived. The MAP was lowest (57 +/- 3 [SD] vs. 92 +/- 3 mm Hg) at the lowest hematocrit. The cardiac index was highest (4.0 +/- 0.3 vs. 2.3 +/- 0.6 L/min.m2) at the lowest hematocrit. DO2 was lowest at the lowest hematocrit but VO2 remained constant at all levels of hematocrit. The oxygen extraction ratio increased as hematocrit decreased. With progressive increases in hematocrit, DO2 increased and Qsp/Qt decreased. CONCLUSIONS: The data suggest that, during hemodilution, tissue autoregulation of VO2 and utilization are not impaired, but gas exchange function (Qsp/Qt) is impaired.

Blood Pressure↗