Myocardial infarction after vascular surgery: the role of prolonged stress-induced, ST depression-type ischemia.

OBJECTIVES: The goal of this study was to investigate the nature of the association between silent ischemia and postoperative myocardial infarction (PMI). BACKGROUND: Silent ischemia predicts cardiac morbidity and mortality in both ambulatory and postoperative patients. Whether silent stress-induced ischemia is merely a marker of extensive coronary artery disease or has a closer association with infarction has not been determined. METHODS: In 185 consecutive patients undergoing vascular surgery, we correlated ischemia duration, as detected on a continuous 12-lead ST-trend monitoring during the period 48 h to 72 h after surgery, with cardiac troponin-I (cTn-I) measured in the first three postoperative days and with postoperative cardiac outcome. Postoperative myocardial infarction was defined as cTn-I >3.1 ng/ml accompanied by either typical symptoms or new ischemic electrocardiogram (ECG) findings. RESULTS: During 11,132 patient-hours of monitoring, 38 patients (20.5%) had 66 transient ischemic events, all but one denoted by ST-segment depression. Twelve patients (6.5%) sustained PMI; one of those patients died. All infarctions were non-Q-wave and were detected by a rise in cTn-I during or immediately after prolonged, ST depression-type ischemia. The average duration ofischemia in patients with PMI was 226+/-164 min (range: 29 to 625), compared with 38+/-26 min (p = 0.0000) in 26 patients with ischemia but not infarction. Peak cTn-I strongly correlated with the longest, as well as cumulative, ischemia duration (r = 0.83 and r = 0.78, respectively). Ischemic ECG changes were completely reversible in all but one patient who had persistent new T wave inversion. All ischemic events culminating in PMI were preceded by an increase in heart rate (delta heart rate = 32+/-15 beats/min), and most (67%) of them began at the end of surgery and emergence from anesthesia. CONCLUSIONS: Prolonged, ST depression-type ischemia progresses to MI and is strongly associated with the majority of cardiac complications after vascular surgery.

Myocardial ischemia in sedated patients undergoing fiberoptic bronchoscopy.

STUDY OBJECTIVE: To study the incidence of myocardial ischemia and related hemodynamic alterations in sedated patients undergoing fiberoptic bronchoscopy (FOB). DESIGN: Prospective study. SETTING: Tertiary care, university hospital. PATIENTS: Twenty-nine patients, age 50 years or older, undergoing elective FOB. INTERVENTIONS: Myocardial ischemia was assessed by continuous ECG monitoring beginning 30 min before, and until 2 h after FOB. MEASUREMENTS AND RESULTS: During FOB, there was a significant rise in heart rate (89+/-3 [mean+/-SE] to 120+/-4 beats/min) and fall in oxygen saturation (95+/-1 to 90+/-1%). There was no significant rise in systolic or diastolic BP. Five patients (17%) had myocardial ischemia during FOB that lasted 20+/-8 min. Their demographic and pre-FOB characteristics were not different from the other patients. Compared to baseline values, a significant rise in heart rate, a fall in oxygen saturation, and no significant change in BP were observed during FOB in patients, both with or without ischemia. Although not statistically significant, ischemia was associated with more protracted procedures. CONCLUSIONS: Myocardial ischemia may develop in elderly patients undergoing FOB. This observation encourages the routine use of ECG and oximetry during FOB, allowing for early intervention to prevent the dangerous combination of hypoxia, tachycardia, and myocardial ischemia. Moreover, this study suggests that methods to ensure oxygenation during FOB should be adhered to, and that the routine administration of atropine should be reconsidered.

Coronary spasm during outpatient fiberoptic laser bronchoscopy.

A 63-year-old woman with metastatic breast cancer was referred to our bronchoscopy unit for outpatient laser resection of an endobronchial mass through fiberoptic bronchoscopy. The patient had no history of ischemic heart disease. During the procedure, the patient developed an ST-segment elevation and a complete atrioventricular block. IV nitroglycerin and morphine were effective in treating this episode. In this patient, we were able to demonstrate a focal spasm by postbronchoscopy coronary angiography.

Epidural methadone for analgesic management of patients with conservatively treated proximal femoral fractures.

Epidural methadone analgesia was initiated soon after admission to emergency room in elderly patients who sustained osteoporotic proximal femoral fracture and who were considered to be high surgical risks. The severe pain was significantly reduced, enabling early mobilization of the patients. The analgesia was discontinued only when nonnarcotic analgesia sufficed. The treatment lasted for about 3.5 weeks. One minor complication was observed during the treatment period. We concluded that patients who have femoral neck fracture who are at high risk for operation and have to be observed and stabilized before operation can be managed by continuous epidural methadone analgesia.

Echocardiographic evaluation of the coronary sinus.

The purpose of this study was to compare transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) in the evaluation of the coronary sinus and its blood flow. Forty patients were studied by TTE and TEE. The distal coronary sinus and its right atrial communication could be identified in 21 of 40 by TTE, and in all patients by TEE. Coronary sinus diameter measurement at the right atrial communication was possible by TTE in 16 of 40, and in all patients by TEE (maximal diameter 6 to 14 mm, mean 9 +/- 2). Flow velocity measurement by pulsed Doppler was possible in 25 of 40 patients (63%) by TEE, and in none by TTE. The flow velocity pattern was similar to central vein flow velocity, with systolic and diastolic antegrade waves, and a small retrograde end diastolic wave. The coronary sinus cross-sectional area was measured in 5 patients by intravascular ultrasound. It varied in size and shape during the cardiac cycle, reaching a maximum (0.3 to 1.5 cm2) at end diastole, and decreasing by 40% to 70% at end systole. TEE is superior to TTE in the evaluation of the coronary sinus and its blood flow velocity. However, because of the variability in cross-sectional area size and shape, measurement of coronary sinus blood flow may be inaccurate.

Monitoring of spinal cord stimulation evoked potentials during thoracoabdominal aneurysm surgery.

Repair of a thoracoabdominal aneurysm involves a significant risk of ischemic injury to the spinal cord. Standard monitoring of somatosensory evoked potentials, which relies upon peripheral nerve stimulation, becomes nonspecific and insensitive during this surgery when aortic cross-clamping produces lower extremity ischemia causing a peripheral conduction block. Techniques for the insertion of percutaneous epidural electrodes, developed originally for pain management, have been adapted to this setting to permit direct stimulation of the spinal cord for intraoperative monitoring of evoked potentials. The clinical outcome in patients monitored by this technique has been consistent with evoked potential findings.

Attenuation of ocular and systemic responses to tracheal intubation by intravenous lignocaine.

This study was undertaken to determine whether intravenous lignocaine could mitigate or prevent the ocular reactions and especially the acute increase in intraocular pressure associated with laryngoscopy and tracheal intubation. Two groups of children undergoing minor eye surgery under nitrous oxide-oxygen-halothane anaesthesia were examined. The experimental group (n = 17) received 2 mg/kg lignocaine and the controls (n = 18) an equivalent volume of saline. The incidence of local laryngeal and ocular reflexes was much lower in the lignocaine group. Pulse acceleration was significantly lower in the lignocaine group (p less than 0.025), and the maximal mean intraocular pressure was significantly less than in the control group (p less than 0.005). Other ocular reactions were recorded, and all were attenuated after lignocaine administration. The beneficial effects of lignocaine, a suppressant of autonomic reflexes, suggest that intraocular pressure, like the heart rate, rises after intubation as a result of autonomic stimulation. The use of intravenous lignocaine is thus recommended for children at risk, such as those needing an urgent operation because of lacerated eye injury under rapid sequence induction of anaesthesia.

Ruptured inflammatory abdominal aortic aneurysm due to acute myelomonoblastic leukemia.

The extremely rare case of ruptured abdominal aortic aneurysm of inflammatory nature in patient with discovered acute myelomonoblastic leukemia is presented. The difficult problems arising from these, frequently terminal diseases, are discussed.

Luke warm blood cardioplegia for CAB surgery in patients with severely impaired LV function. Improved results.

Ward blood cardioplegia (WBC) has recently been reported to improve myocardial protection in adult open heart surgery, especially in high risk cases. However, WBC has been reported to have some disadvantages including narrow safety margins concerning brain and kidney perfusion. We therefore modified our technique to utilize luke-warm blood cardioplegia (LWBC). We carried out 470 open heart procedures using luke-warm cardioplegia (anterograde + retrograde perfusion) from 1/2/1991 - 30/9/1992; 94 had LVEF < 30% and form the basis of this study. Other major risk factors in this group included: > 70 yrs - 26 patients, L main > 50% - 14 patients, emergencies - 11 patients, redo's - 3 patients. Eightyone patients underwent CAB only; 3 had additional MVR, 3 additional closure acute VSD of whom one underwent additional LV aneurysmectomy, one additional AVR; 4 patients underwent AVR only, and 2 MVR. Average number of grafts/patient for the 81 isolated CAB's was 4.5. IABP was necessary postbypass in 4 patients (9 emergencies were on IABP support at time of operation). Thirty day mortality was 3 patients (3.2%). Late mortality was 5 cases. These results are superior to those achieved using cold protection and warm blood cardioplegia. LWBC is a safe method for myocardial protection in patients undergoing CAB, particularly when LV function is severely compromised.

Intraocular pressure variation during strabismus surgery.

The changes in IOP during strabismus surgery were studied in 40 patients. In most, 37 eyes, there was a marked decrease of IOP during surgery and rapid return to initial levels of IOP. In 13 out of 14 eyes that underwent bilateral surgery, the IOP in the first operated eye returned to about baseline levels by the end of surgery on the second eye. No correlation was found between the changes in IOP and: the type of surgery, the operated muscles, the duration of surgery and anesthesia, or the patients' age. We surmise that the decrease of IOP is probably associated with the intensity of the massage of the globe during the surgery.

Systolic pressure variation predicts the response to acute blood loss.

STUDY OBJECTIVE: To evaluate systolic pressure variation (SPV), defined as the difference between the maximum and minimum systolic blood pressure measured during a controlled mechanical respiratory cycle, as a predictor of the cardiac output (CO) response to an acute decrease in ventricular preload. DESIGN: Prospective study with each subject serving as his or her own control. SETTING: Cardiac surgery operating rooms of a university medical center. PATIENTS: 15 adults with good ventricular function undergoing coronary artery bypass grafting. INTERVENTION: During stable anesthetic conditions and before surgical stimulation, 500 ml of blood was removed from each patient over 10 minutes. MEASUREMENTS AND MAIN RESULTS: CO, central venous pressure (CVP), pulmonary artery diastolic pressure, and pulmonary artery occlusion pressure (PAOP), and SPV before and after phlebotomy were recorded. Phlebotomy was associated with significant decreases in CVP, PAOP, and CO, and an increase in SPV. Of these variables, SPV was the best predictor of the percent decrease in CO resulting from blood loss. CONCLUSION: SPV is a dynamic measurement, which, by revealing the response to small cyclical changes in left ventricular preload that occur during the controlled mechanical respiratory cycle, is a better predictor than central filling pressures of the response of CO to acute decreases in preload that occur as a result of acute blood loss.

ST segment changes following retinal surgery.

STUDY OBJECTIVE: To describe the perioperative cardiac morbidity in adult patients undergoing retinal surgery using continuous Holter monitoring. DESIGN: Prospective study. SETTING: University hospital. PATIENTS: 56 patients scheduled for elective retinal surgery with local anesthesia. INTERVENTIONS: Patients were monitored continuously for 24 hours using a Holter recorder. Blood samples for creatine phosphokinase (CPK) and serum myocardial creatine phosphokinase (CPK-MB) were taken preoperatively and 24 hours postoperatively. The characteristics of myocardial ischemia were compared according to the number of risk factors for ischemic heart disease. MEASUREMENTS AND MAIN RESULTS: The overall incidence of perioperative myocardial ischemia was high: 26.7% (n = 15). These patients exhibited 41 episodes of ischemia with mean ST segment change from baseline of 2.2+/-0.7 mm. However, almost all (93.3%) ischemic episodes were silent. Patients with two risk factors or more had 77% more episodes of ischemia than patients with one risk factor (p < 0.005), and the duration of ischemia was 47+/-22.5 minutes compared with 34.8+/-27.5 minutes (p = NS). The first episode of ischemia occurred an average of 10 hours after surgery. No patient had intraoperative evidence of ischemia. Half of the ischemic episodes were associated with an increase in heart rate. No patient had evidence of acute myocardial infarction. CONCLUSION: Retinal surgery with local anesthesia is accompanied by a high incidence of postoperative myocardial ischemia. No negative outcome was correlated to the occurrence of postoperative myocardial ischemia. The significance of these findings has yet to be evaluated.

Effect of halothane on sarcolemmal calcium channels during myocardial ischemia and reperfusion.

The present results provide indirect support for other studies which showed that halothane inhibited the Ca2+ accumulation associated with myocardial ischemia in isolated guinea pig hearts (6), demonstrating a potentially beneficial effect of the anesthetic on the ischemic heart. The role of halothane in preventing ischemia-induced dysrhythmias and attenuation of free radical generation on reperfusion offers a new potential use during open heart surgery. The method of continuous perfusion of oxygenated blood cardioplegia, retrogradely, through the coronary sinus, enables a concomitant administration of the VA before and during the ischemic period of the cardiopulmonary bypass. Further studies may promote the use of the volatile anesthetic when myocardial ischemia and reperfusion are present during open heart surgery.

[A severe obstruction of the upper airways in a child: procedure to follow]. / Obstruction sévère des voies aériennes supérieures chez un enfant: conduite à tenir.

We report the case of a tracheal stenosis in a young child as a result of prolonged intubation. The anesthetic management of the airway laser surgery is discussed. A multidisciplinary cooperation allowed good results.

Prevention of perioperative venous thromboembolism and coronary events: differential responsiveness to an intervention program to improve guidelines adherence.

INTRODUCTION: Prevention of venous thromboembolism and coronary events (with beta-blockers) during and after surgery is at the top of a list of safety practices for hospitalized patients, recommended by the Agency for Health Care Research and Quality (AHRQ). We wished to determine and improve adherence to clinical guidelines for these topics in our institution. PATIENTS, MATERIAL, AND METHODS: A prospective survey was conducted over several weeks on operated patients in a 1200-beds medical center (a teaching, community and referral hospital in Jerusalem, Israel). Eligibility for and actual administration of prophylactic treatment with anticoagulant and beta-blockers were determined. Following an intervention program, which included staff meetings, development of local protocols, and academic detailing by a nurse, the survey was repeated. RESULTS: In general, adherence to recommended anticoagulation prophylaxis was low, found in only 29% [95% confidence interval (CI) = 23-36] of eligible patients. After the intervention, adequate anticoagulation increased to 50% (95% CI = 40-59) of eligible patients (P < 0.001). Initiation of beta-blockers in preventing perioperative cardiac events was very low (0%, 95% CI = 0-5%) and did not increase after intervention. CONCLUSIONS: Adherence to guidelines for prevention of surgical complications was found to be low in our institution. A multifaceted intervention significantly increased use of prophylaxis for venous thromboembolism but not for coronary events. This differential response suggests that the success of a quality improvement project strongly depends on topic content and its phase of acceptance.

Ischaemic preconditioning but not isoflurane prevents post-ischaemic production of hydroxyl radicals in a canine model of ischaemia-reperfusion.

BACKGROUND AND OBJECTIVE: Isoflurane has been shown to mimic ischaemic preconditioning (IPC). The protective effect of IPC, or applying isoflurane or perfusion with the 'push-pull' complex zinc-desferrioxamine (Zn-DFO) in the canine heart, was investigated. METHODS: Thirty minutes after salicylate administration (100 mg kg(-1)) the heart was exposed. All dogs were subjected to a 10 min left anterior descending artery occlusion followed by 2 h of reperfusion. In Group I (n = 9) isoflurane (2.5%) was administered 10 min prior to and during ischaemia. In Group II (n = 8), IPC was elicited by 5 min coronary artery occlusion, followed by 5 min of reperfusion, prior to the 10 min ischaemia. In Group III (n = 9) Zn-DFO (2.5 mg kg(-1)) was given 10 min prior to ischaemia. The effects of these interventions were compared to control (n = 10). Coronary sinus blood concentrations of salicylate, 2,3-dihydroxybenzoic acid (DHBA), lactate, pH and oxygen content were monitored. RESULTS: In the control group, 2,3-DHBA increased by 32% above the pre-ischaemic value (P < 0.05). In contrast, in the IPC hearts, a significant decrease in the production of 2,3-DHBA was observed (40% lower than baseline, P < 0.01). In the isoflurane group only a 13% (and non-significant) decrease was noticed. In the Zn-DFO group a 33% decrease was found (P < 0.01). The increase in lactate concentrations in the IPC and Zn-DFO groups was significantly smaller than that of control and isoflurane groups. CONCLUSIONS: IPC protected the heart against the deleterious effects of reperfusion, possibly by amelioration of the level of oxygen-derived reactive species, and the complete inhibition of reactive hydroxyl radical production. Isoflurane did not prove to be as effective in reducing the free radical damage.

Isoflurane does not mimic ischaemic preconditioning in decreasing hydroxyl radical production in the rabbit.

BACKGROUND: Reactive oxygen species are an important mediator in isoflurane-induced myocardial preconditioning. However, hydroxyl radicals are also released during reperfusion after regional ischaemia. The purpose of the present study was to test whether ischaemic preconditioning and isoflurane would influence the production of hydroxyl radicals during reperfusion. METHODS: After i.v. administration of salicylate 100 mg kg(-1) and a 30 min stabilization period, New Zealand White rabbits were subjected to 40 min of regional myocardial ischaemia and 2 h of reperfusion. Ischaemic preconditioning was elicited by 5 min ischaemia followed by 10 min reperfusion (before the 40 min ischaemia). In another group, isoflurane (2.1%) was administered for 30 min, followed by 15 min washout, before the long ischaemia. Area at risk and infarct size were assessed by blue dye injection and tetrazolium chloride staining. We quantified the level of OH-mediated conversion of salicylate to its dihydrobenzoate derivatives (2,3- and 2,5-DHBAs). Normalized values of the DHBAs (ng DHBA per mg salicylate) were calculated. RESULTS: Mean (se) infarct size was 57 (6)% of the risk area in the untreated controls. This was significantly smaller in the ischaemic preconditioning and isoflurane groups: 22 (5) and 23 (6)% respectively. At 10 min of reperfusion, ischaemic preconditioning limited the mean increase in 2,3-DHBA to 24% from baseline, compared with 81% in control and 74% in the isoflurane group. Normalized 2,5-DHBA was maximally increased by 75% in the untreated group, 4 min after reperfusion. Ischaemic preconditioning significantly inhibited this increase (24% increase from baseline, P<0.01). However, the increase observed in the isoflurane group was not different from control (71%). CONCLUSIONS: As already known, ischaemic preconditioning and isoflurane markedly reduced infarct size. However, only ischaemic preconditioning decreased postischaemic production of hydroxyl radicals. These different effects suggest different protective mechanisms at the cellular level.