Paul G. Barash

Measurement of ejection fraction by thermal dilution techniques

The reproducibility, accuracy, and clinical applicability of ventricular ejection fraction derived by a thermal dilution technique were assessed in 22 dogs and 18 patients. Results obtained by the thermal technique were compared to simultaneous results obtained by radionuclide angiography. Right ventricular ejection fraction, measured in 9 dogs (1014 determinations) and 8 patients (744 determinations) was reproducible +/- 5%. Left ventricular ejection fraction, measured in 10 patients, was reproducible +/- 5%. Correlation between thermal and radionuclear measurements varied from 0.86 to 0.93 (all P less than 0.02). We conclude that, because of its low cost, ease of use, and accuracy, thermally derived ejection fraction determinations can be helpful in hemodynamic monitoring of critically ill patients.

Complications occurring in the postanesthesia care unit: a survey.

To identify and quantitate complications occurring in the postanesthesia care unit (PACU), a prospective study evaluated 18,473 consecutive patients entering a PACU at a university teaching hospital. Using a standardized collection form, the incidence of intra-operative and PACU complications was determined. The combined PACU and intraoperative complication rate was 26.7%. Data showed a PACU complication rate of 23.7%, with an overall intraoperative complication rate of 5.1%. Nausea and vomiting (9.8%), the need for upper airway support (6.9%), and hypotension requiring treatment (2.7%) were the most frequently encountered PACU complications. Patients in whom PACU complications developed were analyzed by ASA physical status. Of all patients experiencing nausea and vomiting (n = 1571), the highest percentage were ASA physical status II patients (n = 831). Likewise, in the group of 1450 patients who demonstrated a need for upper airway support, 792 were ASA physical status II. In patients experiencing a major cardiovascular complication, for example, variables associated with a greater risk of developing any PACU complications were ASA physical status (status II), duration of anesthesia (2–4 h), anesthetic technique, emergency procedures, and certain types of surgical procedures (orthopedic or abdominal). For patients admitted with a temperature of < 35°C the duration of the PACU stay was 152 ± 46 min compared with 116 ± 65 min for patients with a temperature ≥36°C (P < 0.01). In conclusion, events occurring during the PACU period continue to be a source of patient morbidity.

Intranasal and oral cocaine kinetics

Plasma cocaine levels were determined in 7 subjects after intranasal and oral cocaine. Intranasal doses of 0.19, 0.38, 0.75, 1.5, and 2.0 mg/kg were given as a 10% aqueous solution; 0.38 mg/kg was given as crystalline cocaine HCl. Oral cocaine was administered in doses of 2.0 and 3.0 mg/kg. Intranasal cocaine kinetics were described by a 1‐compartment open model with 2 consecutive first‐order input steps and first‐order elimination. Oral cocaine disposition was described by a 1‐compartment open model with a lag time followed by a single first‐order input phase and first‐order elimination. The mean elimination half‐life (t½) for cocaine by the intranasal route to 7 subjects was 75 ± 5 min (mean±SE). The mean t½ after oral administration to 4 subjects was 48 ± 3 min. The relative bioavailability [as determined by the area under the concentration‐time curve (AUC)] for the 2.0‐mg/kg dose by the intranasal and oral routes was not different. There was a linear increase in AUC with increasing intranasal dose.

Scientific principles and clinical implications of perioperative glucose regulation and control.

Development of hyperglycemia after major operations is very common and is modulated by many factors. These factors include perioperative metabolic state, intraoperative management of the patient, and neuroendocrine stress response to surgery. Acute insulin resistance also develops perioperatively and contributes significantly to hyperglycemia. Hyperglycemia is associated with poor outcomes in critically ill and postsurgical patients. A majority of the investigations use the term “hyperglycemia” very loosely and use varying thresholds for initiating treatment. Initial studies demonstrated improved outcomes in critically ill, postsurgical patients who received intensive glycemic control (IGC) (target serum glucose <110 mg/dL). These results were quickly extrapolated to other clinical areas, and IGC was enthusiastically recommended in the perioperative period. However, there are few studies investigating the value of intraoperative glycemic control. Moreover, recent prospective trials have not been able to show the benefit of IGC; neither an appropriate therapeutic glycemic target nor the true efficacy of perioperative glycemic control has been fully determined. Practitioners should also appreciate technical nuances of various glucose measurement techniques. IGC increases the risk of hypoglycemia significantly, which is not inconsequential in critically ill patients. Until further specific data are accumulated, it is prudent to maintain glucose levels <180 mg/dL in the perioperative period, and glycemic control should always be accompanied by close glucose monitoring.

Ultrasound-Guided Internal Jugular Vein Cannulation

overview Traditionally, internal jugular vein cannulation has been performed with the use of external anatomical landmarks and palpation to guide insertion of the needle into the vessel. However, depending on the operator’s experience and the patient’s anatomy, this procedure may be difficult or unsuccessful. Over the past decade, the increased use of ultrasonography to guide internal jugular vein cannulation has improved success rates, reduced the time required to perform the procedure, and reduced complications. 1-3 Indications Ultrasound-guided internal jugular vein cannulation is performed when direct access to the central circulation is needed. Access may be required for a variety of purposes, including monitoring central venous pressure, inserting pulmonaryartery catheters, administering intravenous therapeutic agents and nutrition, performing hemodialysis, and placing cardiac pacemakers. Contraindications General contraindications to internal jugular vein cannulation include infection of the placement site and suspected pathologic conditions affecting the internal jugular vein or the superior vena cava (such as occlusion caused by coagulopathy). Caution should be used when the landmarks have been distorted by trauma or when other anatomical anomalies are present. Be careful when using this procedure in patients who have prior injury to the internal jugular vein, have very small internal jugular veins, or are morbidly obese. In these circumstances, alternative sites should be considered; however, use of the femoral vein is associated with a higher incidence of infection and therefore should be avoided. Ultrasonography is a noninvasive, nonionizing form of imaging that is safe for use in patients of all ages and in women who are pregnant. There are no contraindications specific to the use of ultrasound guidance during internal jugular vein cannulation. Equipment Central venous catheters vary in size, length, and number of infusion ports. The choice of catheter depends on the clinical circumstance. Packaged central venous catheterization kits are commercially available. Kits may include drapes, disinfectant sponges, gauze pads, sutures with needles, a guidewire, a scalpel, a vein dilator, a penetration syringe, a guide syringe, an anesthetic syringe, and 1% or 2% lidocaine anesthetic solution. Sterile gloves, eye protection, a gown, a surgical cap, a mask, and a full-size sterile drape are also required.

Lack of Effectiveness of the Pulmonary Artery Catheter in Cardiac Surgery

BACKGROUND: The pulmonary artery catheter (PAC) continues to be used for monitoring of hemodynamics in patients undergoing coronary artery bypass graft (CABG) surgery despite concerns raised in other settings regarding both effectiveness and safety. Given the relative paucity of data regarding its use in CABG patients, and given entrenched practice patterns, we assessed the impact of PAC use on fatal and nonfatal CABG outcomes as practiced at a diverse set of medical centers. METHODS: Using a formal prospective observational study design, 5065 CABG patients from 70 centers were enrolled between November 1996 and June 2000 using a systemic sampling protocol. Propensity score matched-pair analysis was used to adjust for differences in likelihood of PAC insertion. The predefined composite endpoint was the occurrence of any of the following: death (any cause), cardiac dysfunction (myocardial infarction or congestive heart failure), cerebral dysfunction (stroke or encephalopathy), renal dysfunction (dysfunction or failure), or pulmonary dysfunction (acute respiratory distress syndrome). Secondary variables included treatment indices (inotrope use, fluid administration), duration of postoperative intubation, and intensive care unit length of stay. After categorization based on PAC and transesophageal echocardiography use (both, neither, PAC only, transesophageal echocardiography only), we performed the primary analysis contrasting PAC only and neither (total, 3321 patients), from which propensity paring yielded 1273 matched pairs. RESULTS: The primary endpoint occurred in 271 PAC patients versus 196 without PAC (21.3% vs.15.4%; adjusted odds ratio [AOR], 1.68; 95% confidence interval [CI], 1.24 to 2.26; P < 0.001). The PAC group had an increased risk of all-cause mortality, 3.5% vs 1.7% (AOR, 2.08; 95% CI, 1.11 to 3.88; P = 0.02) and an increased risk of cardiac (AOR, 1.58; 95% CI, 1.14 to 2.20; P = 0.007), cerebral (AOR, 2.02; 95% CI, 1.08 to 3.77; P = 0.03) and renal (AOR, 2.47; 95% CI, 1.68 to 3.62; P < 0.001) morbid outcomes. PAC patients received inotropic drugs more frequently (57.8% vs 50.0%; P < 0.001), had a larger positive IV fluid balance after surgery (3220 mL vs 3022 mL; P = 0.003), and experienced longer time to tracheal extubation (15.40 hours [11.28/20.80] versus 13.18 hours [9.58/19.33], median plus Q1/Q3 interquartile range; P < 0.0001). Use of PAC was also associated with prolonged intensive care unit stay (14.5% vs 10.1%; AOR, 1.55; 95% CI, 1.06 to 2.27; P = 0.02). CONCLUSIONS: Use of a PAC during CABG surgery was associated with increased mortality and a higher risk of severe end-organ complications in this propensity-matched observational study. A randomized controlled trial with defined hemodynamic goals would be ideal to either confirm or refute our findings.

Early Extubation Following Pediatric Cardiothoracic Operation: A Viable Alternative

A protocol is presented that facilitates early extubation following pediatric cardiothoracic operations. A total of 197 consecutive patients were managed according to this protocol. Fifty percent of the patients were less than 3 years old. Cardiopulmonary bypass was required in 113 (57%) of the surgical procedures. Extubation immediately following the surgical procedure was accomplished in 142 (72%) of the patients. Pulmonary complications occurred in 8 of these 142 patients (6%) and in 10 (18%) of the 55 patients requiring postoperative mechanical ventilation. Of the patients having early extubation, 5 (4%) required reintubation. One death in this group was unrelated to pulmonary function. There were 16 deaths among the 55 patients managed with mechanical ventilation. Carefully conducted early extubation provided specific advantages over routine postoperative mechanical ventilation. Modern techniques of anesthesia and surgical repair of congenital heart disease can decrease the requirement for postoperative mechanical ventilation and the potential for related complications.

Ventricular function in children during halothane anesthesia: an echocardiographic evaluation.

The effect of halothane on ventricular function in normal children was studied with the aid of echocardiography, which offers a noninvasive method to obtain these measurements safely. Thirteen healthy children ranging in age from 19 months to 12 years (mean=6 years), undergoing elective non-cardiac surgical procedures, were studied. Secobarbital, 4 mg/kg, and morphine, 0.1 mg/ kg, were administered intramuscularly an hour prior to induction of general anesthesia. Echocardiographic measurements were obtained while the patients breathed room air (control) and following nitrous oxide, 60 per cent, and concentrations of halothane ranging from 0.5 to 2 per cent. Increasing inspired concentrations of halothane significantly altered ventricular function in a dosedependent fashion. At halothane, 2 per cent, systolic blood pressure, pulse rate, and cardiac output decreased to 82, 94, and 72 per cent of control values, respectively. Measurements of ventricular performance, ejection fraction (EF), left ventricular enddiaslolic volume (LVEDV), and mean normalized rate of circumferential fiber shortening (Vuf) showed parallel decreases. Following atropine, 0.02 mg/kg, intravenously, improvement in cardiac output and all rate-dependent variables was observed. Although V,.r improved by 18 per cent, other indices of myocardial performance (EF, LVEDV, PEP/LVET) still showed depression. It is concluded that halothane can significantly decrease ventricular function in children undergoing surgical procedures. The accompanying decrease in cardiac output was completely offset by the administration of atropine.

Preoperative cardiac evaluation for noncardiac surgery: a functional approach.

The preoperative assessment of the high risk patient undergoing noncardiac surgery has traditionally been based on history, physical examination, and preoperative testing. We propose a method of assessing preoperative risk based on the presentation of coronary artery disease, exercise tolerance, and extent of the surgical procedure. Since this is an evolving field, as new information and perioperative management techniques become available, the preoperative evaluation of the high risk patient will change. We have presented one approach based on our interpretation of data from the current anesthesiology and cardiology literature. In the patient with a recent MI, the predischarge symptom-limited stress test and the electrocardiographic classification can be used to better stratify risk. In the patient with angina, testing should be reserved for those patients who are candidates for coronary revascularization or alternative surgical procedures. In the patient at risk of but without overt symptoms of coronary artery disease, the number of clinical risk factors can determine the probability of coronary artery disease in the individual patient. The decision to perform preoperative revascularization should be based on its anticipated improvement of both the short- and long-term prognosis of the patient considering the risk of such procedures. The objective assessment of LVEF should be performed in patients with a poor exercise tolerance with either a high risk of perioperative ischemia or a suspicion of cardiomyopathy.

Onset of altered interventricular septal motion during cardiac surgery. Assessment by continuous intraoperative transesophageal echocardiography.

Abnormal motion of the interventricular septum is frequently observed after uncomplicated cardiac surgery. We sought to elucidate the mechanism underlying this phenomenon by using continuous echocardiographic imaging of the heart from a constant transesophageal location in 21 patients undergoing their first cardiac operation. Quantitative global and regional functional analyses were performed in each patient at baseline (stage 1), after median sternotomy (stage 2), after sternal retraction (stage 3), after pericardiotomy (stage 4), after completion of cardiopulmonary bypass (stage 5), and after chest closure (stage 6). During the first four surgical stages, mean left ventricular fractional shortening varied little among regions with a fixed reference system (maximum range, 31.6-39.2%; p = NS) but changed dramatically after the discontinuation of cardiopulmonary bypass (stage 5). The apparent medial hypokinesis that was observed (4.9 +/- 4.7% [SD]) was accompanied by lateral hyperkinesis (65.2 +/- 4.1%, p less than 0.0001). These regional differences were completely eliminated with a floating reference system (33.6 +/- 2.7% for medial, and 34.8 +/- 1.7% for lateral; p = NS), suggesting cardiac translation. Quantitative curvature analysis supported this conclusion, with preservation of baseline regional curvature seen throughout the procedure. The mean length of individual translational vectors (reflecting systolic movement of the endocardial centroid) remained minimal (less than or equal to 1.0 mm) through stage 4 but increased more than fourfold at stage 5, continuing in a medial direction after chest closure (5.2 +/- 3.0 mm and 271 +/- 6 degrees from anterior). Thus, abnormal postoperative septal motion is not caused by removal of restraining forces of the pericardium or anterior mediastinum but rather appears to be directly related to events occurring during cardiopulmonary bypass.