Andrew B. Leibowitz

Low sensitivity of the anion gap as a screen to detect hyperlactatemia in critically ill patients.

The anion gap is commonly used as a screening test for the presence of lactic acidosis. Analysis of the distribution of anion gaps for 56 adult surgical ICU patients with peak blood lactate levels greater than or equal to 2.5 mmol/L showed the anion gap to be an insensitive screen for elevated lactate in a critically ill, hospitalized population. All patients (11/11) with a peak lactate greater than or equal to 10 mmol/L had an anion gap greater than or equal to 16 mmol/L; however, 50% (6/12) of patients with lactates between 5.0 and 9.9 mmol/L and 79% (26/33) of those with lactates between 2.5 and 4.9 mmol/L had anion gaps less than 16 mmol/L. Hyperlactatemia was associated with considerable mortality at all levels: 100% among patients with lactate levels greater than or equal to 10 mmol/L, 75% between 5.0 and 9.9 mmol/L, and 36.4% between 2.5 and 4.9 mmol/L. Acidosis (pH less than 7.30) did not significantly alter mortality by lactate level. The observation that, for 57% of patients in this study, an elevated lactate level was not accompanied by an elevated anion gap suggests that hyperlactatemia should be included in the differential diagnosis of nonanion gap acidosis.

Left-sided superior vena cava: a not-so-unusual vascular anomaly discovered during central venous and pulmonary artery catheterization.

ObjectiveTo report our ICU experience with patients noted to have a left-sided superior vena cava after central venous and pulmonary artery catheterization. DesignRetrospective review. SettingSurgical ICUs in a University and Veterans Administration Medical Center. PatientsFive patients who had insertion of central venous or pulmonary artery catheters were noted to have abnormal placement. ResultsFive patients were noted to have a left-sided superior vena cava that was not appreciated on preinsertion radiography after central venous (two patients) or pulmonary artery catheterization (three patients). The finding of left-sided superior vena cava was confirmed by computed tomography scan (one patient), transesophageal echocardiography (one patient), bolus contrast injection (two patients), and intraoperative inspection (one patient). ConclusionsLeft-sided superior vena cava occurs infrequently, most often in association with a right-sided superior vena cava. It is often associated with cardiac septal defects. The intensivist should be aware of its occurrence in order to not mistake catheters placed in it as being present in the arterial circulation or malpositioned outside of the venous circulation. (Crit Care Med 1992; 20:1119–1122)

Transesophageal echocardiography utilization in high-volume liver transplantation centers in the United States.

OBJECTIVE Transesophageal echocardiography (TEE) during liver transplantation (LT) has been shown to be helpful in managing fluid therapy, monitoring myocardial function, and identifying intraoperative LT complications. The present study sought to investigate the current utilization of TEE by anesthesiologists during LT as well as issues of training and credentialing in this monitoring modality. DESIGN A survey distributed by electronic mail. SETTING LT centers in the United States in which more than 50 liver transplantation procedures were performed annually. PARTICIPANTS Survey respondents were contact persons in the LT divisions of the anesthesiology department of selected centers. INTERVENTIONS Data collection only. MEASUREMENT AND MAIN RESULTS A total of 40 high-volume LT centers were identified, and survey responses were received from 30 of those. Among 217 anesthesiologists, 86% performed TEE in some or all LT cases. Most users performed a limited-scope examination, although some performed a comprehensive TEE examination during LT. Most users acquired their TEE skills informally. Only 12% of users were board certified to perform TEE, and only 1 center reported having a policy related to credentialing requirements for TEE. CONCLUSIONS There is high utilization of intraoperative TEE by anesthesiologists to perform limited-scope examinations during LT cases. Training to perform such examinations is mostly informal, and credentialing processes are lacking. An opportunity exists to establish guidelines, training programs, and standards for quality assurance in the use of this valuable monitoring modality.

Invasive and Concomitant Noninvasive Intraoperative Blood Pressure Monitoring Observed Differences in Measurements and Associated Therapeutic Interventions

Background: Noninvasive (NIBP) and intraarterial (ABP) blood pressure monitoring are used under different circumstances and may yield different values. The authors endeavored to characterize these differences and hypothesized that there could be differences in interventions associated with the use of ABP alone ([ABP]) versus ABP in combination with NIBP ([ABP+NIBP]). Methods: Simultaneous measurements of ABP and NIBP made during noncardiac cases were extracted from electronic anesthesia records; the differences were subjected to regression analysis. Records of blood products, vasopressors, and antihypertensives administered were also extracted, and associations between the use of these therapies and monitoring strategy ([ABP] vs. [ABP+NIBP]) were tested using univariate, multivariate, and propensity score matched analyses. Results: Among 24,225 cases, 63% and 37% used [ABP+NIBP] and [ABP], respectively. Systolic NIBP was likely to be higher than ABP when ABP was less than 111 mmHg and lower than ABP otherwise. Among patients with hypotension, transfusion occurred in 27% versus 43% of patients in the [ABP+NIBP] versus [ABP] group, respectively (odds ratio = 0.4; 95% CI 0.35–0.46), and 7% versus 18% of patients in the [ABP+NIBP] versus [ABP] group received vasopressor infusions, respectively (P < 0.01). Among hypertensive patients, 12% versus 44% of those in the [ABP+NIBP] versus [ABP] group received antihypertensive agents, respectively (P < 0.01). Conclusions: NIBP was generally higher than ABP during periods of hypotension and lower than ABP during periods of hypertension. The use of NIBP measurements to supplement ABP measurements was associated with decreased use of blood transfusions, vasopressor infusions, and antihypertensive medications compared with the use of ABP alone.

Radiologic assessment of potential sites for needle decompression of a tension pneumothorax

BACKGROUND:The recommended treatment of suspected tension pneumothorax is immediate needle decompression. Recommended sites and needle sizes for this procedure vary, and there are published reports of failed decompression as well as iatrogenic hemothorax. We investigated the optimal needle length and relative safety of three potential needle decompression sites. METHODS:Using thoracic computed tomography scans of 100 adults, we measured the distance from skin surface to pleura and to intrathoracic structures at the level of the sternal angle at the midhemithoracic line (MHL), and at the level of the xiphoid process at the anterior axillary and midaxillary lines, as well as the distance from the sternal midline to internal mammary vessels. RESULTS:Median distances from the midline to the MHL and internal mammary vessels were 6.1 and 3.0 cm, respectively. Median (range) depth-to-pleura below the skin surface at the MHL, midaxillary lines, and anterior axillary line sites was 3.1 (1.4–6.9), 3.5 (1.7–9.3+), and 2.6 (1.0–7.7+) cm, respectively. Overall, there was a lower margin of safety on the left side compared with the right side, and the MHL site was safest on both sides. CONCLUSIONS:Needle decompression of suspected tension pneumothorax should be attempted in the MHL at the level of the sternal angle using a needle at least 7 cm long inserted perpendicular to the horizontal plane. This approach should yield the highest success rate and margin of safety compared with other sites.

Effects of the stable prostacyclin analogue iloprost on mesenteric blood flow in porcine endotoxic shock.

OBJECTIVE To determine the effects of the stable prostacyclin analog, iloprost, in a porcine model of endotoxin-induced mesenteric ischemia. DESIGN Prospective, experimental, randomized, controlled study. SETTING Animal research laboratory at a university medical center. INTERVENTIONS Pigs were randomized to receive a constant infusion of iloprost (0.18 microg/kg/min) or an equivalent amount of carrier solution (normal saline) 30 mins before being infused with endotoxin (100 microg/kg over 1 hr). The infusion with iloprost or carrier solution was continued for the duration of the experiment. MEASUREMENTS AND MAIN RESULTS Twelve pigs (six per group), weighing between 20 and 22 kg, underwent laparotomy during which a magnetic flowprobe was placed around the superior mesenteric artery and an ileal tonometer was inserted. Thirty minutes before they were infused with endotoxin, the animals were randomized to receive intravenous iloprost or normal saline. Endotoxin was infused centrally over a 60-min period. Animals received normal saline at a rate of 1.2 mL/kg/min which was begun at the start of the endotoxin infusion. Data were measured at the end of the endotoxin infusion (E60) and 1 hr later (E120). Mean arterial pressure was not affected by the dosage of iloprost used in this experiment. After resuscitation, the cardiac output returned to baseline in the iloprost-treated group but remained decreased in the control group (2.6 +/- 0.5 vs. 1.6 +/- 0.4 L/min). Superior mesenteric blood flow increased 34% above baseline levels in animals pretreated with iloprost (from 363 +/- 85 to 485 +/- 81 mL/min). The superior mesenteric PCO2 was significantly higher (53 +/- 9 vs. 40 +/- 5 torr; 7.1 +/- 1.2 vs. 5.3 +/- 0.7 kPa) and the ileal intramucosal pH was significantly lower (7.07 +/- .28 vs. 7.44 +/- .23) in the control group than in the iloprost-treated group. CONCLUSIONS Pretreatment with intravenous iloprost effectively increased intestinal blood flow in this model of endotoxin-induced mesenteric ischemia. This action of the drug resulted in an attenuation of ileal intracellular acidosis. Since low-dose iloprost had no effect on mean arterial pressure, it may be a useful adjunct in the treatment of sepsis and septic shock.

The pulmonary artery catheter in anesthesia practice in 2007: an historical overview with emphasis on the past 6 years.

The pulmonary artery catheter has been widely used in anesthesiology and critical care medicine. Until recently, only retrospective or relatively weak prospective studies examining its effect on outcome had been performed. Over the past 6 years, however, a number of well-designed prospective trials and statistically sound retrospective studies have been completed. All of these show no benefit and some even reveal a potential for increased morbidity. Reasons for this devices inability to improve outcome are numerous, including wrong patient selection and misinterpretation, but the most impressive and convincing evidence is that filling pressures measured from the catheter, particularly the pulmonary artery “wedge” pressure, have no physiologic value. The wedge pressure has been shown to not correlate with other accepted methods of determining left ventricular filling or volume or intravascular volume and also does not help to generate cardiac function curves. Therefore, knowledge of it may actually lead to incorrect management more frequently than not.

Immobilization Hypercalcemia in Critical Illness Following Bariatric Surgery

Background: Immobilization hypercalcemia has been previously reported in a number of entities but not as a complication of bariatric surgery.We recognized this complication in two consecutive bariatric patients requiring intensive care unit (ICU) admission. Methods:These two patients are reported in detail, and a review of our ICU database is also reported. Results: Treatment of immobilization hypercalcemia in these two patients with pamidronate was successful. Conclusion: Immobilization hypercalcemia complicating the course of bariatric patients requiring ICU admission is a newly recognized and treatable entity.

Flexible Bronchoscopy Still the Definitive Standard for Airway Management

To the Editor: We read with great interest, but equal concern, the recent article by Rosenstock et al.1 and the accompanying editorial by Fiadjoe and Litman.2 Both publications confirm that flexible bronchoscopy “will still be required” and that anesthesiologists in “large number(s)... lack the commitment and desire to master fiberoptic intubation” and concluding that using a rigid videoscope represents a paradigm shift in anticipated difficult airway management is misguided. Indeed, in expert hands, not only was flexible bronchoscopy a reliable and efficient technique, equivalent in success rate and time to intubation to the McGrath video laryngoscope, but 7 of the 48 patients randomized to the McGrath video laryngoscope could not undergo the awake technique! The exclusion criteria (limited mouth opening and neck pathology prohibiting recurrent laryngeal nerve block via the transtracheal method) were also so restrictive that it is no surprise that the success rates of the two methods were equivalent. Head and neck pathology has already been associated with a high failure rate using video laryngoscopy.3 Perhaps any device chosen, including traditional Macintosh and Miller laryngoscopes, when this patient population was eliminated for investigation, would result in equivalent success. Given the fact that the success and time to perform an awake intubation was equivalent “in expert” hands, perhaps the recommendations should be that anesthesiologists and anesthesia trainees use flexible bronchoscopy more frequently to develop and maintain skills that require more practice and expertise rather than seek alternative and potentially limited devices that subjugate one’s required skillset. If we continue to compromise the development and maintenance of flexible bronchoscopic skills, future studies will inevitably demonstrate the superiority of the rigid devices in limited patient populations because of a lack of anesthesiologists who are skilled flexible bronchoscopists. As clinicians and educators, we must squelch the desire to further encourage the steady erosion of advanced airway skills. Although we thank the authors for further demonstrating that video laryngoscopic methods have their role in managing patients with anticipated difficult airways, the need to perform awake flexible fiberoptic intubation is still an absolute vital skill that requires a renewed educational emphasis so that anesthesiologists can and will use this technique when indicated. Residency programs and airway workshops need to spend more time teaching the more difficult to master fiberoptic technique and less time teaching video laryngoscopy, which is easier to learn and maintain mastery of in the first place. (Accepted for publication October 10, 2012.) Adam I. Levine, M.D.,* Andrew B. Leibowitz, M.D. *The Icahn School of Medicine at Mount Sinai, New York. adam. levine@mssm.edu

Effect of lower limb compression devices on thermodilution cardiac output measurement.

Objective:The aim of this study was to determine whether lower limb (calf) sequential compression devices (SCDs) have a significant effect on thermodilution cardiac output measurements using a pulmonary artery catheter. Design:Prospective clinical investigation. Setting:Surgical and neurosurgical intensive care units in a university hospital. Patients:A total of 43 patients with pulmonary artery catheters and bilateral lower limb SCDs. Measurements and Main Results:Cardiac output was measured (average of three) when the SCDs were off (T1), during the first 2–4 secs of the inflation cycle (T2), during seconds 4–8 of the inflation cycle (T3), and when the SCDs were off again (T4). Cardiac output measurements were consistently lower when measured during the SCD inflation cycle. The decrease in cardiac output ranged from 7.58% to 49.5%, with a mean reduction of 24.51% in the first 2–4 seconds and 20.61% during seconds 4–8 (p < .001). Two patients displayed an increase in cardiac output during the inflation cycle; one patient had an increase of 2.78% and the other an increase of 13.5%. In 11 patients, measurements were also made using a pulse contour–analysis cardiac output device, but no changes in pulse contour–analysis cardiac output were observed during the same time period. Conclusions:Thermodilution cardiac output measurements via a pulmonary artery catheter should not be done during the inflation cycle of lower limb SCDs because they produce a falsely low cardiac output.