Emilio B. Lobato

cerebral Microembolism Diagnosed by Transcranial Doppler during Total Knee Arthroplasty : Correlation with Transesophageal Echocardiography

BACKGROUND Tourniquet deflation following total knee arthroplasty (TKA) frequently results in release of emboli into the pulmonary circulation. Small emboli may gain access to the systemic circulation via a transpulmonary route or through a patent foramen ovale. This study examined the incidence of cerebral microembolism after tourniquet release by transcranial Doppler (TCD) ultrasonography and its correlation with echogenic material detected in the left atrium. METHODS Twenty-two adult patients (9 men, 13 women) undergoing TKA were studied with simultaneous TCD ultrasonography and transesophageal echocardiography. Data were recorded after anesthesia induction and tourniquet inflation and during tourniquet deflation. Emboli counts were performed manually off-line. Echogenic material in the left atrium was qualitatively assessed and correlated with TCD data. Patients were examined postoperatively for focal neurologic deficits. RESULTS Fifteen patients had unilateral TKA (six left, nine right) and seven had bilateral TKA. Cerebral emboli were detected in 9 of 15 patients (60%) with unilateral TKA and in 4 of 7 patients (57%) with bilateral TKA. Echogenic material was identified in the left atrium in eight patients (two through a patent foramen ovale and six from the pulmonary veins). Emboli counts were significantly higher in patients with bilateral TKA compared with those with unilateral TKA (P<0.05). Duration of tourniquet time in patients with emboli was longer only during bilateral TKA (P<0.05). All patients with echogenic material in the left atrium detected by transesophageal echocardiography had emboli as assessed by TCD ultrasonography. No focal neurologic deficits were identified. CONCLUSIONS Cerebral microembolism occurs frequently during tourniquet release, even in the absence of a patient foramen ovale. This passage most likely occurs through the pulmonary capillaries or the opening of recruitable pulmonary vessels.

Cross-sectional area of the right and left internal jugular veins.

OBJECTIVE To compare the cross-sectional area (CSA) of the right internal jugular vein (RIJV) with the left internal jugular vein (LIJV) using two-dimensional ultrasound and to measure the response to the Valsalva maneuver in both the supine and Trendelenburg positions. DESIGN Prospective and randomized. SETTING University-affiliated hospital. PARTICIPANTS Fifty healthy adult volunteers. INTERVENTIONS The CSA of both the RIJV and LIJV was measured with a 5-MHz, two-dimensional surface transducer before and during a 10-second Valsalva maneuver with the subjects in the supine position, and then with the subjects in a 10 degree Trendelenburg tilt. MEASUREMENTS AND MAIN RESULTS After the baseline measurements were performed, the subjects were divided into two groups based on the CSA of the RIJV and LIJV. Group 1 had an LIJV CSA equal to or greater than that of the RIJV (n = 10) and group 2 had an LIJV CSA less than that of the RIJV (n = 40). Of the latter 40 patients, 17 (34%) had an LIJV CSA less than 50% of that of the RIJV. In both groups, the CSA of both veins increased significantly with the Valsalva maneuver, Trendelenburg tilt, and both maneuvers combined. CONCLUSION The findings suggest that in one third of adults (34%), the LIJV is significantly smaller compared with the RIJV and, combined with operator inexperience, may influence the success rate and risk for complications. Thus, the use of ultrasound and maneuvers that increase CSA is suggested during LIJV cannulation.

A randomized study of left versus right internal jugular vein cannulation in adults

STUDY OBJECTIVE To compare the success rate and incidence of complications of right internal jugular vein (RIJV) versus left internal jugular vein (LIJV) cannulation using external landmarks or surface ultrasound guidance. DESIGN Prospective randomized study. SETTING Operating room of a university-affiliated hospital. PATIENTS 120 adult patients scheduled for elective abdominal, vascular, or cardiothoracic procedures with general anesthesia and mechanical ventilation in whom central venous cannulation was clinically indicated. INTERVENTIONS Patients were randomized to four groups for RIJV cannulation using the landmark approach (Group 1) or surface ultrasound (Group 2) versus LIJV cannulation with the landmark approach (Group 3) or ultrasound (Group 4). MEASUREMENTS AND MAIN RESULTS The data collected included time from first puncture to guidewire insertion, number of attempts, and associated complications. If conversion to the ultrasound technique was required, the number of crossover patients and reasons for failure were recorded. Cannulation of the LIJV was more time consuming; it required more attempts; and it was associated with a greater number of complications when compared to the right side (p < 0.05). CONCLUSIONS Left IJV cannulation is more time consuming than RIJV cannulation and is associated with a higher incidence of complications. The use of ultrasound improves success rate and decreases the number of complications during IJV cannulation.

Cross-sectional area and intravascular pressure of the right internal jugular vein during anesthesia: Effects of trendelenburg position, positive intrathoracic pressure, and hepatic compression

STUDY OBJECTIVE To determine changes in the cross-sectional area of the right internal jugular vein (RIJV) in response to positive intrathoracic pressure and hepatic compression in mechanically ventilated patients during general anesthesia. DESIGN Prospective, nonrandomized study. SETTING A university medical center. PATIENTS 15 ASA physical status II and III adult patients undergoing RIJV cannulation after anesthetic induction and endotracheal intubation. INTERVENTIONS Patients were studied first supine and then at a 10 degrees and 20 degrees Trendelenburg tilt. The cross-sectional area of the RIJV was determined by two-dimensional ultrasound before and during 1) an end-inspiratory hold of 20 cm H2O; 2) hepatic compression for 10 seconds; and 3) both maneuvers applied simultaneously. Subsequently, the RIJV was cannulated and the intravascular pressure was measured during the same sequence of maneuvers. MEASUREMENTS AND MAIN RESULTS In supine patients, the cross-sectional area of the RIJV significantly increased during the end-inspiratory hold, during hepatic compression, and with both maneuvers performed simultaneously (p < 0.05). With a 10 degrees Trendelenburg tilt, only both maneuvers applied simultaneously increased the cross-sectional area of the RIJV significantly, and with the 20 degrees Trendelenburg tilt, no further increase was seen. Intravascular pressure of the RIJV consistently increased with each maneuver in all positions. CONCLUSION Hepatic compression and positive inspiratory hold effectively dilate the RIJV in supine patients and can be used when the Trendelenburg position is not advisable or possible. Performing these maneuvers with patients in the Trendelenburg position may facilitate cannulation, possibly by making the vein less collapsible due to increased intravascular pressure.

Endotracheal Tube Location Verified Reliably by Cuff Palpation

To verify a safe location of the endotracheal tube (ETT), palpation of the ETT at the sternal notch is a time-honored technique: After anesthetic induction and confirmation of orotracheal intubation, the patients head is placed in a neutral position. The ETT is withdrawn or advanced while gentle, repetitive pressure is applied with the fingers at the level of the suprasternal notch. Simultaneously, the pilot balloon is held in the other hand. When the balloon distends from the pressure applied at the notch, the ETT is secured. We tested the efficacy of this technique in men and women who underwent general anesthesia. After the ETT was secured, the distance (in cm) from its tip to the upper incisors, that is, the length of ETT inserted, was measured to confirm its location relative to the carina. The study population consisted of 44 women and 38 men (n = 82) who ranged in age from 16 to 85 yr and in ASA physical status from I to IV. The size of the ETT tube for women ranged from 7.0 to 8.0 and for men, 7.0 to 8.5. Average distance from the tip of the ETT to teeth in women was 20.2 cm (range, 17-23) and in men 21.9 cm (range, 19-25). Average distance to the carina in women was 3 cm (range, 2-5) and in men 3.4 cm (range, 2-6). In this study, palpation of the ETT cuff effectively confirmed ETT location. The technique, which should not be used to verify endotracheal rather than bronchial intubation, should decrease the risk of bronchial intubation or impingement on the carina. (Anesth Analg 1995;81:135-8)

Effects of trendelenburg position and positive intrathoracic pressure on internal jugular vein cross-sectional area in anesthetized children

STUDY OBJECTIVE To compare the cross-sectional area (in cm(2)) of the left internal jugular vein (LIJV) and right internal jugular vein (RIJV) in anesthetized children, and measure the response to the Trendelenburg tilt position (TBRG) and a positive inspiratory pressure hold. DESIGN Prospective, nonrandomized study. SETTING University medical center. PATIENTS 45 ASA physical status I and II children, ages 6 months to 8 years, undergoing general anesthesia and mechanical ventilation. INTERVENTIONS The cross-sectional area of both internal jugular veins was measured with a 5-MHz, two-dimensional surface transducer, at the level of the cricoid cartilage. Three measurements were obtained: 1) with the patient supine, 2) during a 10-second breath-hold with a positive inspiratory pressure (PIP) of 20 cm H(2)O, and 3) with the patient at 20 degrees TBRG. Data were analyzed with two-way analysis of variance (ANOVA) and Student-Newman-Keuls test, with a p < 0.05 considered significant. MEASUREMENTS AND MAIN RESULTS In supine patients, the cross-sectional area of the RIJV was larger than the LIJV in 31 patients (69%), and equal or smaller in 14 patients (31%) (0.80 +/- 0.38 vs. 0.59 +/- 0.22; p = 0.002). A PIP hold, but not TBRG, significantly dilated the RIJV (0.8 +/- 0.38 at baseline vs. 0.93 +/- 0.42 with TBRG; p = not significant vs. 1.1 +/- 0.46 with PIP; p < 0.05), whereas neither maneuver was effective with the LIJV. CONCLUSION The cross-sectional area of the RIJV is often greater than the LIJV; the TBRG was not effective to increase the cross-sectional area of the internal jugular veins, and only a PIP hold increased significantly the cross-sectional area of the RIJV. In this study, the LIJV appeared of smaller size and less compliant compared with the RIJV.

Bacitracin irrigation: a cause of anaphylaxis in the operating room.

Implications We report a unique case of acute anaphylaxis after mediastinal irrigation with a dilute bacitracin solution.

Pneumoperitoneum as a Risk Factor for Endobronchial Intubation During Laparoscopic Gynecologic Surgery

Patients undergoing gynecological surgery under laparoscopic guidance usually receive general anesthesia with endotracheal intubation and mechanical ventilation.The creation of a pneumoperitoneum and the Trendelenburg position, both of which are used to improve visualization, are associated with cephalad movement of the diaphragm. This may increase the risk of endobronchial intubation. We studied the change in the distance from the tip of the endotracheal tube (ETT) to the carina with a fiberoptic bronchoscope in 30 patients aged 21-40 yr who were undergoing laparoscopic tubal ligation (n = 28) or hysterectomy (n = 2). Measurements were taken in the supine and Trendelenburg positions before and after pneumoperitoneum. The average distance from the ETT to the carina in the supine position was 2.1 +/- 0.8 cm and in the Trendelenburg position was 1.8 +/- 0.8 cm (P = not significant). After insufflation of the abdominal cavity, the mean distance decreased to 0.7 +/- 1.4 cm in the supine position (P < 0.05) and was associated with endobronchial intubation in eight patients. The addition of the Trendelenburg position to an established pneumoperitoneum resulted in minimal displacement (0.54 +/- 1.4 cm, P < 0.05) and one additional endobronchial intubation. We conclude that the insufflation of gas in the abdominal cavity, and not the change in patient position, is the main risk factor for endobronchial intubation in patients undergoing laparoscopic gynecologic surgery. Implications: This study demonstrated that in anesthetized women, the insufflation of gas into the abdomen during laparoscopy for gynecologic surgery is the main risk factor for migration of the endotracheal tube into a bronchus. (Anesth Analg 1998;86:301-3)

Effects of Milrinone Versus Epinephrine on Grafted Internal Mammary Artery Flow After Cardiopulmonary Bypass

OBJECTIVE To compare changes on grafted internal mammary artery (IMA) flow after cardiopulmonary bypass in response to the administration of milrinone or epinephrine. DESIGN Prospective and randomized. SETTING University-affiliated hospital. PARTICIPANTS Twenty consenting, adult patients undergoing CABG. INTERVENTIONS Patients were randomized to receive either milrinone, 50 microg/kg, or epinephrine, 0.03 microg/kg/min, immediately after cardiopulmonary bypass. IMA flow was measured with a laser Doppler flow probe before and after the administration of either drug. MEASUREMENTS AND MAIN RESULTS Baseline grafted IMA flow was similar for both groups (milrinone, 38+/-14 mL/min; epinephrine, 33+/-10 mL/min). In patients who received milrinone, flow increased by 24% to 50+/-17 mL/min, p<0.05; whereas with epinephrine, it remained essentially unchanged (33+/-10 v. 31+/-11 mL/min). CONCLUSIONS This study confirms that the vasodilatory effect of milrinone on the IMA is also present after its anastomosis, whereas low-dose epinephrine exhibits neither beneficial nor adverse effects. It is suggested that in the absence of excessive vasodilation, milrinone should be considered as a first-line inotrope after coronary artery bypass graft surgery, to achieve an increase in contractility and IMA artery flow.

Intraoperative management of distal tracheal rupture with selective bronchial intubation

Patients with tracheal rupture present a considerable challenge to the anesthesiologist. The most important aspect in anesthesiology in such cases is to maintain oxygenation and ventilation without compromising surgical repair. We report a case of a woman who suffered a chemical perforation of the carina and left bronchus after ingesting hydrochloric acid during a suicide attempt. We describe the intraoperative management strategies, with emphasis on the use of bilateral bronchial intubation to provide selective lung ventilation. Alternative modes of ventilation and the use of cardiopulmonary bypass are discussed.