R. David Warters

Difficult airway management practice patterns among anesthesiologists practicing in the United States: have we made any progress?

STUDY OBJECTIVE To determine the extent instruction and practice in the use of airway devices and techniques varies among anesthesiologists practicing in the United States. DESIGN Survey questionnaire. SETTING University medical center. MEASUREMENTS Questionnaires were completed by American-trained anesthesiologists who attended the 1999 American Society of Anesthesiologists (ASA) Annual Meeting. Data collected included demographics, education, skills with airway devices/techniques, management of clinical difficult airway scenarios, and the use of the ASA Difficult Airway Algorithm. MAIN RESULTS 1) DEMOGRAPHICS: 452 questionnaires were correctly completed; 62% attending anesthesiologists, 70% <50 years, 81% males, 44% from academic institutions, 63% >10 years of practice, 81% night duty, 77% board certified. 2) Education: 71% had at least one educational modality: difficult airway rotation, workshops, conferences, books, and simulators. 3) Skills: Miller blade 61%, Bullard laryngoscope 32%, LMA 86%, Combitube 43%, bougie 43%, exchangers 47%, cuffed oropharyngeal airway (COPA) 34%, retrograde 41%, transtracheal needle jet ventilation 34%, cricothyrotomy 21%, fiberoptics 59%, and blind nasal intubation 78%. The average reported use of special airway devices/techniques was 47.5%. 4) Management choices: failed intubation/ventilation: LMA (81%) and for all other situations: fiberoptic intubation. Use of ASA Difficult Airway Algorithm in clinical practice (86%). CONCLUSION Fiberoptic intubation and the LMA are most popular in management of the difficult airway.

Impact of cardiopulmonary bypass management on postcardiac surgery renal function.

Objective: Cardiac surgery on cardiopulmonary bypass (CPB) is associated with postoperative renal dysfunction and up to 4% of patients with normal preoperative renal function develop acute renal failure (ARF) requiring dialysis. According to recent investigations, CPB management is not evidence-based and, thus, current clinical CPB practice may favor renal dysfunction. The purpose of our study was to investigate if postcardiac surgery renal dysfunction is influenced by CPB management. Methods: We selected three groups of patients with normal preoperative renal function who had been subjected to cardiac surgical procedures on CPB: 44 patients with postoperative ARF requiring hemofiltration/dialysis (ARF group), 51 patients with postoperative renal dysfunction not requiring hemofiltration/dialysis (serum creatinine increase > 0.5 mg/dl within 48 h postsurgery: CREAgroup), and 48 patients with normal postoperative renal function (Control group). The patients’ on-line CPB records were analyzed for CPB duration, CPB perfusion pressure, CPB flow, and periods on CPB at a perfusion pressure < 60 mmHg. On-CPB diuretic and vasoconstrictor medication was recorded. Results: Patient demographics were similar for the three groups. In the ARF group, CPB duration was longer (166± 77 [standard deviation, SD] min) compared to CREA (115± 41 min; p < 0.001) and to Control groups (107± 40 min; p < 0.001), and mean CPB flow was lower (2.35± 0.36 l/min/m2) compared to CREA (2.61± 0.35 l/min/m2; p=0.0015) and to Control groups (2.51± 0.33 l/min/m2; p = 0.09). Mean arterial pressure on CPB (ARF: 61± 10; CREA: 60± 7; Control: 63± 9 mmHg; p = 0.19) as well as furosemide and norepinephrine medication on CPB were similar for the groups. Compared to Control (46± 26 min), CPB duration at arterial pressures < 60 mmHg was longer in ARF (78± 60 min; p = 0.034) and in CREA (62± 36 min; p=0.048). Conclusions: Our data suggest that current clinical CPB management impacts postoperative renal function. We found that patients with normal preoperative renal function who developed postoperative ARF had longer CPB duration, lower CPB perfusion flow, and longer periods on CPB at pressures < 60 mmHg compared to patients with no post CPB ARF. However, our data do not allow us to separate these CPB-related factors from the potential influence of perioperative low cardiac output syndrome as a cause for postoperative ARF. Thus, future clinical studies are required to elucidate CPB-induced ARF and to optimize CPB management for ARF prevention.

The Incidence of Class “zero” Airway and the Impact of Mallampati Score, Age, Sex, and Body Mass Index on Prediction of Laryngoscopy Grade

IMPLICATIONS In an earlier study we proposed the addition of a new airway class, zero (visualization of the epiglottis), to the four classes of the modified Mallampati classification. In this prospective study, 764 surgical patients were assessed with regard to their airway class (including class zero), laryngoscopy grade, and the effect of the airway class and other predictors on the laryngoscopy grade.

Cardiac surgical conditions induced by β-blockade : Effect on myocardial fluid balance

BACKGROUND Both crystalloid and blood cardioplegia result in cardiac dysfunction associated with myocardial edema. This edema is partially due to the lack of myocardial contraction during cardioplegia, which stops myocardial lymph flow. As an alternative, acceptable surgical conditions have been created in patients undergoing coronary artery bypass operations with esmolol-induced minimal myocardial contraction. We hypothesized that minimal myocardial contraction during circulatory support using either standard cardiopulmonary bypass (CPB) or a biventricular assist device would prevent myocardial edema by maintaining cardiac lymphatic function and thus prevent cardiac dysfunction. METHODS We placed 6 dogs on CPB and 6 dogs on a biventricular assist device and serially measured myocardial lymph flow rate and myocardial water content in both groups and preload recruitable stroke work only in the CPB dogs. In all dogs we minimized heart rate with esmolol for 1 hour during total circulatory support. RESULTS Although myocardial lymph flow remained at baseline level during CPB and increased during biventricular assistance, myocardial water accumulation still occurred during circulatory support. However, as edema resolved rapidly after separation from circulatory support, myocardial water content was only slightly increased after CPB and biventricular assistance, and preload recruitable stroke work was normal. CONCLUSIONS Our data suggest that minimal myocardial contraction during both CPB and biventricular assistance supports myocardial lymphatic function, resulting in minimal myocardial edema formation associated with normal left ventricular performance after circulatory support. The concept of minimal myocardial contraction may be a useful alternative for myocardial protection, especially in high-risk patients with compromised left ventricular function.

Combined spinal-epidural anesthesia for Cesarean section in a patient with peripartum dilated cardiomyopathy.

A combined spinal epidural anesthesia was performed and 6 mg of bupivacaine were injected into the subarachnoid space. This was supplemented after 60 min with 25 mg of bupivacaine injected epidurally. The patient’s hemodynamic status was monitored with direct intra-arterial blood pressure and central venous pressure measurements. The patient’s perioperative course was uneventful. Conclusion: In patients suffering from peripartum cardiomyopathy, undergoing Cesarean section, combined spinal-epidural anesthesia may be an acceptable anesthetic alternative.PurposeTo report a case of peripartum dilated cardiomyopathy associated with morbid obesity and possible difficult airway presenting for elective Cesarean section, which was successfully managed with combined spinal-epidural anesthesia.Clinical featuresA morbidly obese parturient with a potentially difficult airway, suffering from idiopathic peripartum cardiomyopathy (ejection fraction 20%), was scheduled for an elective Cesarean section.RésuméObjectifPrésenter un cas de cardiomyopathie du péripartum associée à de ïobésité morbide et à des difficuités d’intubation possibles chez une patiente qui a subi une césarienne réalisée avec succès sous anesthésie rachidienne et périduraie combinée.Eléments cliniquesUne parturiente, présentant une obésité morbide et des difficuités d’intubation possibies, souffrait de cardiomyopathie idiopathique du péripartum (fraction d’éjection de 20%) au moment de subir ia césarienne prévue.L’anesthésie rachidienne et périduraie combinée a été réaiisée avec l’injection de 6 mg de bupivacaine dans l’espace sousarachnoïdien, complétée après 60 min, par l’injection périduraie de 25 mg de bupivacaïne. L’état hémodynamique de ia patiente a été surveiiié par des mesures directes de ia tension intraartérielle et de ia pression veineuse centraie. Aucun incident périopératoire n’a été observé.ConclusionL’anesthésie rachidienne et périduraie combinée peut être un choix acceptable à envisager dans le cas de patientes atteintes de cardiomyopathie du péripartum qui subissent une césarienne.

Augmenting cardiac contractility hastens myocardial edema resolution after cardiopulmonary bypass and cardioplegic arrest

Although myocardial edema is associated with cardio-pulmonary bypass (CPB) and cardioplegic arrest (CPA), interventions to expedite edema removal have not been investigated. The primary mechanism for the removal of excess interstitial fluid in the heart is myocardial lymphatic drainage, but lymphatic function can be impaired by decreased contractility because of edema. The purpose of this study was to determine whether enhancing cardiac contractility would increase myocardial lymphatic function and hasten edema resolution after CPB. Sixteen dogs were subjected to CPB and 1 h of hypothermic CPA. After weaning from CPB, 10 dogs received an intravenous dobutamine infusion and 6 dogs received no inotropic support. We determined myocardial lymph driving pressure from the major cardiac lymphatic, myocardial water content by using microgravimetry, and the peak rate of left ventricular pressure increase (dP/dtmax) by using micromanometry. Measurements were taken at baseline, during CPA, and 60 min after CPB. Compared with controls, dobutamine-treated dogs had an increased dP/dtmax (P < 0.05), which was associated with higher lymph driving pressures (P < 0.05), resulting in lower myocardial water gain 1 h after CPB (P < 0.05). We conclude that the resolution of myocardial edema after CPB was hastened by dobutamine. Organized ventricular contraction and myocardial contractility seem to be important determinants of myocardial lymphatic function and myocardial edema removal. These findings suggest that the administration of inotropic drugs after CPB may hasten cardiac recovery. Implications: Myocardial edema, which develops during cardiopulmonary bypass and cardioplegic arrest, contributes to cardiac dysfunction after heart surgery. This study demonstrated that enhancement of cardiac contractility by the administration of dobutamine after cardiopulmonary bypass and cardioplegic arrest was associated with increased myocardial lymphatic function and hastened edema resolution in dogs. (Anesth Analg 1997;85:987-92)

Myocardial protection with high-dose β-blockade in acute myocardial ischemia

Objective: The risk of postoperative cardiac dysfunction is markedly increased by emergency coronary artery bypass grafting in the presence of acute myocardial ischemia. High dose b-blockade during continuous coronary perfusion has been suggested as an alternative to conventional cardioplegia and this technique has been applied successfully in high risk patients for coronary artery bypass grafting (CABG) surgery. This study compared high dose b-blockade with esmolol to continuous warm blood cardioplegia in a clinically oriented model of acute left ventricular (LV) ischemia and reperfusion. Methods: Twelve dogs were subjected to 60 min of regional LV ischemia by left anterior descending branch (LAD) ligation. Cardiopulmonary bypass (CPB) and aortic crossclamp were applied after 45 min of ischemia. Thereafter, high dose b-blockade during continuous coronary perfusion (ESMO, na 6) or antegrade continuous warm blood cardioplegia (WBC, na 6) were maintained for 60 min. Myocardial water content (measured from endomyocardial biopsies using a microgravimetric technique), global LV function (preload recruitable stroke work: PRSW), and regional LV function (echocardiographic wall motion score) were determined at baseline and after weaning from CPB. Results: During aortic crossclamp interstitial edema formation was significantly higher in the WBC group with an average water gain of 2.2 ^ 0.49 vs. 0.76 ^ 0.12% in the ESMO group. Thereafter, edema resolved in both groups, but myocardial water gain remained significantly higher in the WBC group at 60 and 120 min post CPB (0.98 ^ 0.19 and 1.13 ^ 0.32% vs. 0.07 ^ 0.25 and 0.04 ^ 0.08%). Global LV function was significantly higher in the ESMO group at 60 and 120 min post CPB (PRSW 103 ^ 6 and 94.7 ^ 4.6% of baseline vs. 85.3 ^ 4.9 and 74.7 ^ 7.6% of baseline). However, regional LV function showed no significant difference between groups. Conclusions: High-dose b-blockade during continuous coronary perfusion may allow the surgeon to utilize the advantages of warm heart surgery, while avoiding the interstitial edema formation and temporary cardiac dysfunction associated with continuous warm blood cardioplegia. In high risk patients such as patients with unstable angina or after failed PTCA, high-dose bblockade may be an applicable alternative to cardioplegic arrest. q 2000 Elsevier Science B.V. All rights reserved.

Endotracheal intubation with a gum-elastic bougie in unanticipated difficult direct laryngoscopy: comparison of a blind technique versus indirect laryngoscopy with a laryngeal mirror.

We evaluated the efficacy of intubation over a gum-elastic bougie by using either a blind technique or indirect laryngoscopy with a laryngeal mirror in patients with unexpected difficult direct laryngoscopy. In a prospective study, 60 consecutive patients with an unexpected Grade III or IV direct laryngoscopy were randomly allocated for intubation with a gum-elastic bougie either blindly (Group 1) or by indirect laryngoscopy with a laryngeal mirror (Group 2). We evaluated the failure rate of each method of intubation, complications related to either method, and the time required for intubation. Out of 725 patients evaluated over a 2-mo period, 60 patients (8.3%) had a Grade III laryngoscopy, and 30 of these were randomized into each group. There were 8 failed intubations in Group 1 compared with 1 failed intubation in Group 2 (P < 0.05). All eight failures in the blind intubation group ended with esophageal intubation. No additional complications were noted in either group. The time required for endotracheal intubation with each group was not significantly different (45 ± 10 s versus 44 ± 11 s). We conclude that intubation with a gum-elastic bougie had a lower failure rate using indirect laryngoscopy with a laryngeal mirror than a traditional blind technique.

Use of CobraPLA™ for airway management in a neonate with Desbuquois syndrome. Case report and anesthetic implications

We present the anesthetic management of an infant with Desbuquois syndrome (a rare form of micromelic dwarfism) with a possible difficult airway. The anesthetic implications of this syndrome are presented. The airway was managed with a new supraglottic device – the CobraPLA. Although intubation through this device was not possible in this instance, CobraPLA provided a satisfactory supraglottic airway. It was easy to insert and provided satisfactory conditions for positive pressure ventilation. The CobraPLA provides another option for airway management.

β-blockade as an alternative to cardioplegic arrest during cardiopulmonary bypass

Abstract Background . As an alternative to cardioplegic arrest, cardiac surgical conditions have been produced using β-blocker–induced minimal myocardial contraction (MMC) during cardiopulmonary bypass. The technique of MMC involves the use of high-dose intravenous esmolol to suppress myocardial chronotropy and inotropy sufficiently to produce cardiac surgical conditions. The purpose of this study was to compare conventional crystalloid cardioplegic arrest with MMC in terms of ischemia avoidance, myocardial edema formation, and cardiac function. Methods . Twelve dogs were placed on cardiopulmonary bypass. Six dogs were subjected to crystalloid cardioplegic arrest for 2 hours. Surgical conditions were produced in the other 6 dogs for 2 hours using intravenous esmolol without aortic clamping or cardioplegia. Arterial and coronary sinus lactate concentrations were determined as a gauge of myocardial ischemia. Myocardial water content was determined using microgravimetry and preload recruitable stroke work was determined using sonomicrometry and micromanometry. Results . Significant lactate washout was demonstrated after cardioplegic arrest but not after MMC. Myocardial water content was significantly less during and after MMC compared with cardioplegic arrest ( p p Conclusions . In contrast to a previous study that involved 1 hour of MMC, in this study, ventricular function was decreased to the same extent as with cardioplegic arrest after 2 hours of MMC. This was attributed to the accumulation of ASL-8123, the primary metabolite of esmolol, which possesses β-antagonist properties. Although postbypass ventricular function is similar in both groups, MMC appears to be superior in terms of ischemia avoidance and myocardial edema formation.