Electrocardiographic changes during cesarean section under regional anesthesia.

To determine electrocardiographic changes and whether myocardial ischemia occurs during cesarean section, electrocardiograms were recorded continuously using Holter monitoring in 25 patients undergoing elective cesarean section under either spinal or epidural anesthesia. In addition, in 13 of the patients, two-dimensional precordial echocardiography was carried out before and during cesarean section. ST segment depression suggestive of myocardial ischemia occurred in 16 patients including 8 of the 13 with echocardiograms. Wall motion remained entirely normal during episodes of ST segment depression. Patients in whom ST depression developed had significantly more rapid heart rates at delivery than those who did not experience ST depression. We conclude that ST segment depression is a common feature of the electrocardiogram during cesarean section under regional anesthesia and is not the result of myocardial ischemia.     

ST-segment depression and myocardial contractility during Cesarean section under spinal anesthesia

PURPOSE: To evaluate myocardial contractility during ST segment depression in healthy parturients during Cesarean section (CS). METHODS: Forty-seven consecutive term parturients undergoing elective CS under spinal anesthesia were studied. The ST segment was recorded continuously on leads II and V5 using a Holter monitor. Myocardial performance was evaluated by measuring cardiac index (CI), heart rate (HR), pre-ejection period (PEP), ventricular ejection time (VET), systolic time ratio (STR, PEP/VET), and ejection fraction (EF) with an impedance cardiograph. RESULTS: Fourteen patients (30%) developed ST segment depression within 15 min after delivery and the remaining 33 (70%) did not (controls). Seven patients developed a 1 mm change, five patients a 2 mm change and the remaining two a 3 mm change in the ST segment. Compared with pre-anesthesia values, the mean HR increased from 103 +/- 10 to 116 +/- 10 (ISD) bpm (P = 0.001), CI from 4.7 +/- 0.7 to 5.6 +/- 1.7 L.min-1 (P = 0.01), EF from 0.58 +/- 0.08 to 0.66 +/- 0.05 (P = 0.01) and STR decreased from 0.26 +/- 0.06 to 0.2 +/- 0.04 (P = 0.01) during ST segment depression. At this time, CI, HR and EF were greater and STR smaller than values obtained 15 min after delivery in the control subjects. CONCLUSION: ST-segment depression occurring during CS is associated with a hyperkinetic myocardial contractile state.     

Electrocardiographic changes during cesarean section: a review

Recently, various authors have noticed and studied the phenomenon of ST segment depression during cesarean section. We have undertaken a review of the various postulated etiologies including venous air emboli, hormonal influences, autonomic nervous system influences tachycardia, postural influences, hypokalemia, hyperventilation, and myocardial ischemia. It appears that ST segment depression during cesarean section is almost certainly a multifactorial phenomenon. There is evidence that some myocardial dysfunction occurs during these episodes. Additionally, the hormonal milieu, tachycardia, and the postural component probably contribute to the phenomenon. Venous air emboli, hypokalemia, and hyperventilation probably have a minimal role. The sympatholysis produced by regional anesthesia is of unclear significance. It is important to note the apparent lack of morbidity associated with these changes.     

Perioperative ST-segment depression and troponin T release. Identification of patients with highest risk for myocardial damage

BACKGROUND: Patients undergoing major vascular surgery are at constant risk of developing perioperative myocardial complications, especially myocardial infarction. The following study was performed to answer the question whether ST segment changes, analysed by Holter monitoring and ST segment analysis, are accompanied by release of cardiac troponin T, a highly specific marker of myocardial damage. METHODS: Twenty patients undergoing elective aortic resection were studied by performing Holter ECG, including ST segment analysis, beginning on the evening before surgery until the third postoperative day. Within this period serum levels of cardiac troponin T were determined at 8 timepoints. RESULTS: A total of 8/20 of the patients (40%) showed significant ST depressions (range -0.17/-0.68 mV), without any clinical symptom, with a median of 9 episodes (range 2-24). In 3 of the 8 patients, each with repetitive periods of ST depression, elevated troponin T levels were found (0.45/0.52/1.69 micrograms/l). No troponin T release nor cardiac events were noticed in the remaining patients. No dependency could be found between troponin T release and the magnitude of ST depression or the number of ST depression episodes. CONCLUSION: Haemodynamic changes, oxygen imbalance and stress during major vascular surgery frequently lead to an ischaemic burden, which is indicated by ST segment changes during ECG ST analysis. Longlasting ST depression reaching an individual critical cut-off limit followed by structural myocardial damage may be verified by elevated levels of cardiac troponin T. Prolonged periods of ST depression should be followed by determination of cardiac troponin T.     

Left Ventricular Dysfunction after Non-Cardiac Surgical Procedures in Patients with Ischemic Heart Disease

In order to demonstrate the presence of postischemic ventricular dysfunction after non-cardiac surgical procedures, myocardial perfusion scintigraphy with thallium 201 and radionuclide ventriculography were performed before and 24 h after intervention in 20 patients suffering from angina pectoris. A long-term ECG recording was used in all patients to detect peroperative myocardial ischemia. In 14 of the 20 patients studied, both ventriculography and thallium scintigraphy were unchanged at the postoperative study. Comparison of pre- and postoperative radionuclide data revealed an increased deficit in one patient, both increased deficit and decreased ejection fraction in four others and a decreased ejection fraction in one other. In these five last patients, continuous ECG recording demonstrated the occurrence of peroperative ST segment depression. These results underline the part played by prolonged peroperative episodes of myocardial ischemia in the occurrence of postoperative left ventricular dysfunction.     

Does perioperative myocardial ischemia lead to postoperative myocardial infarction?

To determine if a relationship exists between perioperative myocardial ischemia (ST segment depression greater than or equal to 0.1 mV) and postoperative myocardial infarction (PMI), nonparticipating observers recorded all ECG, hemodynamic, and other events between arrival of patients in the operating room and onset of cardiopulmonary bypass during 1,023 elective coronary artery bypass operations (CABG). The roles of preoperative patient characteristics, quality of the operation limited by disease as rated by the surgeon and duration of ischemic cardiac arrest as risk factors for PMI also were quantified. ECG ischemia occurred in 36.9% of all patients, with almost half the episodes occurring before induction of anesthesia. PMI was almost three times as frequent in patients with ischemia (6.9% vs. 2.5%) and was independent of when ischemia occurred. Ischemia was related significantly to tachycardia but not hypertension nor hypotension and was frequent in the absence of any hemodynamic abnormalities. The anesthesiologist whose patients had the highest rate of tachycardia and ischemia had the highest rate of PMI. Although neither single nor multiple preoperative patient characteristics related to PMI, suboptimal quality of operation and prolonged ischemic cardiac arrest increased the likelihood of PMI independent of the occurrence of myocardial ischemia. The authors conclude that perioperative myocardial ischemia is common in patients undergoing CABG, occurs randomly as well as in response to hemodynamic abnormalities, and is one of three independent risk factors the authors identified as related to PMI. PMI is unrelated to preoperative patient characteristics such as ejection fraction and left main coronary artery disease, and its frequency will relate primarily to perioperative management rather than patient selection.     

Frequency of electrocardiographic changes indicating myocardial ischemia during elective cesarean delivery with regional and general anesthesia: detection based on continuous Holter monitoring and serum markers of ischemia

STUDY OBJECTIVE: To determine the frequency of electrocardiographic (ECG) changes and to assess the occurrence of myocardial ischemia during elective cesarean delivery with either regional or general anesthesia. DESIGN: Randomized, prospective, single-blinded clinical trial. SETTING: Large referral hospital. PATIENTS: 40 ASA physical status I and II term parturients. INTERVENTIONS: Patients were divided randomly into two groups as follows: the regional anesthesia group (group 1, n = 20) and the general anesthesia group (group 2, n = 20). MEASUREMENTS: In each case, continuous ECG was done using a 7-lead Holter monitor in the operating room, continuing for 24 hours after surgery. All Holter traces were analyzed by a study-blinded cardiologist. Blood samples were collected preoperatively (baseline) and at one, 5, and 24 hours postoperatively. Serum troponin T, creatinine kinase-MB, and myoglobin levels were measured. MAIN RESULTS: Two patients in group 1 (10%) and one patient in group 2 (5%) showed one mm ST-segment depression for two to 5 minutes. In all 40 cases, troponin T levels were in the normal range at all time points studied. In both groups, mean serum creatinine kinase-MB and myoglobin levels at one and 5 hours postoperatively were significantly higher than at baseline (P < 0.05). These high CK-MB and myoglobin levels were returned to normal ranges at the end of the study period; none of these women showed ST-segment changes. CONCLUSION: The ST-segment changes are not frequent in healthy women undergoing elective cesarean delivery during either regional or general anesthesia, and we found no evidence of myocardial injury.     

Intraoperative myocardial ischemia: localization by continuous 12-lead electrocardiography

Based primarily on results obtained during exercise treadmill testing, electrocardiographic (ECG) leads II and V5 are the suggested optimal leads for detecting intraoperative myocardial ischemia. However, these recommendations have not been validated in this setting using all 12 ECG leads. Accordingly, the authors studied 105 patients with known or suspected coronary artery disease (CAD) undergoing noncardiac surgery with general anesthesia by continuously recording the 12-lead ECG intraoperatively in all patients. The average duration of monitoring was 8.2 +/- 2.7 h (mean +/- SD). Ischemic episodes (i.e., greater than or equal to 1-mm horizontal or downsloping ST depression, greater than or equal to 1.5-mm slowly upsloping ST depression or greater than or equal to 1.5-mm ST elevation in a non-Q wave lead) occurred in 25 patients (24%). Out of 51 ischemic episodes, 45 involved ST depression alone, and the remaining six involved both ST depression and elevation. ST segment changes occurred in a single lead only in 14 episodes, while multiple leads were involved in 37 episodes. Lead sensitivity was estimated assuming that all ST segment changes were true positive responses. Sensitivity using a single lead was greatest in V5 (75%) and V4 (61%), and intermediate in II, V3, and V6 (33%, 24%, and 37%, respectively). The remaining seven leads demonstrated very low sensitivity (2-14%) or exhibited no ischemic changes (I and a VL). Combining leads V4 and V5 increased sensitivity to 90%, while the standard clinical combination, II and V5, was only 80% sensitive. Sensitivity increased to 96% by combining II, V4, and V5. The further addition of V2 and V3 (five leads) increased sensitivity to 100%. This study confirms previous recommendations for the routine use of a V5 lead (either uni- or bipolar) in all patients at risk for ischemia. V4 is more sensitive than lead II, and should be considered as a second choice. However, lead II, superior for detection of atrial dysrhythmias, is more easily obtained with conventional monitors. The use of all three would appear to be the optimal arrangement for most clinical needs, and is recommended if the clinician has the capability.     

Haemodynamic and EKG changes in patients undergoing minimally invasive direct coronary artery bypass

BACKGROUND AND OBJECTIVES: The objective of the report is to monitor, in patients undergoing minimally invasive direct coronary artery bypass surgery (MIDCAB), the haemodynamic parameters, ST segment changes and the incidence of arrhythmias during clamping of the coronary artery and following reperfusion. METHODS: Twelve patients scheduled for elective MIDCAB surgery during isoflurane anesthesia were enrolled in the study. Patients were monitored by a pulmonary artery thermodilution catheter, an arterial line and 5 leads ECG. The different haemodynamic parameters, the ST segment changes, as well as the occurrence of arrhythmias during coronary clamping and ten minutes following reperfusion were compared to the control values. RESULTS: No significant changes in the cardiac index followed clamping of the coronary artery. However, the ST segment was significantly elevated. Following coronary reperfusion, the ST segment recovered to the baseline values, and the cardiac index significantly increased more than the baseline value (3.5 +/- 1.1 l/min/m2 vs 2.6 +/- 0.7 l/min/m2). However, reperfusion was associated with multiple ventricular extrasystoles in four patients. The elevation of the ST segments during coronary clamping was higher in the four patients who developed reperfusion arrhythmias (0.9 +/- 0.4 mm); one of the patients had preoperative frequent VPBs, two patients had history of unstable angina, while the fourth patient had 70% proximal stenosis of the LAD and recent myocardial infarction. CONCLUSIONS: Coronary occlusion in patients undergoing MIDCAB can result in ST segment elevation, followed by reperfusion ventricular extrasystoles. The reperfusion arrhythmias were observed in patients showing a significant elevation of the ST segment during coronary occlusion; risk factors included a preoperative history of arrhythmia, unstable angina, recent MI, and/or 70% LAD stenosis. The rapid restoration of the control ST segment level and the significant increase of cardiac output following coronary reperfusion suggest that isoflurane anesthesia may have provided a degree of myocardial protection during coronary clamping and reperfusion.     

Early postoperative myocardial morbidity in patients with coronary artery disease undergoing major non-cardiac surgery: correlation with perioperative ischaemia

As a part of a study assessing early postoperative myocardial morbidity in 50 patients with active coronary artery disease undergoing major non-cardiac surgery, the ECG was monitored continuously for 24 hr after the onset of anaesthesia, using a frequency modulated (FM) Holter monitor. Concurrent automated blood pressure and pulse were measured non-invasively at three-minute intervals during anaesthesia and subsequently at five-minute intervals. Thirty patients were monitored with two-site ECG recordings, from modified V1 and V5 (Group A). Twenty patients had seventeen-site ECG monitoring, multiplexing a four by four array of precordial electrodes onto one channel of the frequency modulated recorder (Group B). Tapes were analyzed for noise, supraventricular and ventricular dysrythmias, runs of tachy- and bradycardia, and ST segment changes. These data were correlated with serial standard 12-lead ECGs and CK-MB assay in the 72 hr after surgery. Seven tapes from Group A could not be analyzed. Change (greater than 1 mm) on ST monitoring from both Groups A (14/23), B (14/20), correlated with serial 12-lead ECG and/or CK-MB changes. The majority of first ST change 19/28 (70%) occurred after anaesthesia. In 14/28 (50%) ST change occurred during episodes of tachycardia and elevated blood pressure (greater than 20% above baseline). Nine patients (9/23) in Group A had no ST change; however, six had serial 12-lead ECG and/or CK-MB changes. Six patients (6/20) in Group B had no ST changes, and none of these patients had any change of serial 12-lead ECGs or CK-MB assay. No patient complained of chest pain during the Holter monitoring period. Continual monitoring of heart rate and blood pressure and accurate ST monitoring are essential to detect and treat perioperative myocardial ischemia. A multiple-lead precordial system is substantially more sensitive than traditional two-lead ECG holter monitoring in detecting myocardial ischaemia.     

Pre-bypass myocardial ischaemia in patients undergoing coronary artery surgery

One hundred patients undergoing elective coronary artery surgery were studied to determine the incidence of pre-bypass myocardial ischaemia. Leads II, aVF and V5 of the electrocardiogram (ECG) were recorded at five-minute intervals from arrival in the anaesthetic room until onset of cardiopulmonary bypass. Thirteen patients developed sixteen episodes of significant ST depression on the ECG during the study period. Three patients were diagnosed as having postoperative myocardial infarction by ECG criteria and creatine phosphokinase-MB rise above 80 units. None of these patients had pre-bypass ST depression. Comparisons of these results with similar studies are presented.     

Perioperative myocardial ischemia in patients with peripheral arterial occlusive diseases

Patients with peripheral vascular disease (PVD) often have coronary artery disease (CAD) which means an increased risk during anesthesia. The prevalence of CAD is nearly 50% among such patients. Owing to claudication, diagnostic stress tests can rarely be performed in PVD patients. In order to evaluate the frequency of transient perioperative myocardial ischemia, Holter monitoring was performed in 30 consecutive PVD patients with ASA II-III and AVK scale (Fontaine) II-IV who were undergoing femoropopliteal bypass surgery. Patients who had left bundle branch block and left ventricular hypertrophy or were taking digitalis medication were excluded from Holter monitoring. The ST-segment analysis of the frequency modulated recordings (n = 19) revealed episodes of myocardial ischemia in 26% of the patients. Most (75%) of the episodes occurred preoperatively, and 25%, during or after the anesthesia or during preparation for it. Risk factors for CAD were more often found in patients with ST segment alterations than in patients without ST segment deviations, even though the preoperative antianginal medication administered was comparable in the two subgroups. It is concluded that in a considerable subset of PVD patients silent myocardial ischemia occurs, which can be related to the different perioperative intervals by means of ST segment analyses of Holter recordings. The ST segment may allow a better insight into the cardiac state of PVD patients. Further studies are necessary in larger populations to test our suspicion.     

Performance of non-invasive stroke volume variation during passive leg raising as a predictor of hypotension following induction of spinal anesthesia for elective cesarean delivery: a single cohort study

BackgroundSpinal anesthesia for cesarean delivery is accompanied by hypotension in up to 70% of cases. To date, there is no gold standard for predicting hypotension after spinal anesthesia for cesarean delivery. The Clearsight™ device is a non-invasive system that uses a digital cuff to calculate stroke volume. We hypothesized that stroke volume variation induced with passive leg raising before spinal anesthesia for elective cesarean delivery could predict the occurrence of hypotension.MethodsWe conducted a prospective observational study, including third trimester parturients undergoing elective cesarean delivery with spinal anesthesia. We analyzed the stroke volume variation performance for predicting hypotension. Stroke volume was collected in the semi-recumbent position (baseline) and during passive leg raising before spinal anesthesia. Systolic arterial blood pressure measurement was followed for 15 min after spinal anesthesia. Hypotension was defined as a ≥20% decrease from the baseline measurement. All parturients received appropriate hypotension prophylaxis.ResultsData from 42 parturients were analyzed. Hypotension occurred in 45%. The area-under-the curve for predicting hypotension using the stroke volume variation was 0.83 (95% CI 0.68 to 0.98; P=0.001). The best cut-off value for predicting hypotension was 7%, having a sensitivity of 87% (95% CI 0.70 to 0.99) and a specificity of 83% (95% CI 0.69 to 0.97).ConclusionIn our study of third trimester parturients undergoing cesarean delivery and receiving appropriate hypotension prophylaxis, a digital non-invasive monitoring device of stroke volume variation analysis was useful for predicting the occurrence of hypotension after spinal anesthesia.     

Comparison of hemodynamic, electrocardiographic, mechanical, and metabolic indicators of intraoperative myocardial ischemia in vascular surgical patients with coronary artery disease

To compare mechanical, electrocardiographic, and metabolic indices of myocardial ischemia, the cardiokymogram (CKG), the V5 ECG, left anterior descending coronary artery territory lactate extraction, and pulmonary capillary wedge pressure (PCWP) were measured in 53 vascular surgical patients with coronary artery disease. Measurements were performed preoperatively and at four specific intraanesthetic intervals: after tracheal intubation, before surgery, and 10 and 30 min after incision. Measurements and sampling sequence took 5-7 min, and therapy for the probable cause of ischemia was instituted following completion of this sequence. Myocardial ischemia was defined as type II or III CKG, 0.1 mV or greater horizontal or downsloping depression of V5 ECG ST segment, 0.2 mV or greater elevation of V5 ECG ST segment, or myocardial lactate production. Thirty-nine patients (74%) had a total of 89 episodes of myocardial ischemia. Seventy-four episodes (83%) were detected by the CKG, 31 (44%) were evident on the ECG, and 13 (15%) by evidence of lactate production. The concordance among the indices of myocardial ischemia was poor. Patients with an abnormal preoperative ECG experienced a greater number of ischemic episodes (P less than 0.001). Elevation of PCWP or the presence of A-C or V-waves greater than 5 mmHg above the mean did not individually reflect ischemia reliably. Intraoperative myocardial ischemia is common in vascular surgical patients and is most sensitively detected by ventricular wall motion abnormality.     

剖宫产术病人硬膜外左旋布比卡因的胎盘转移

目的 评价剖宫产术病人硬膜外左旋布比卡因的胎盘转移情况.方法 择期硬膜外麻醉下剖宫产术病人60例.于L1,2或L2,3间隙进行硬膜外穿刺,穿刺成功后注射0.5%左旋布比卡因5ml(含1:20万肾上腺素)试验剂量,5 min后无脊麻征象后,追加9～12 ml,5 min后再追加1次.娩出时抽取脐动脉血样,进行血气分析;于娩出后l、5min行Apgar评分.选择30例病人,娩出时抽取母体静脉血样和脐静脉血样,采用高效液相色谱法测定血浆左旋布比卡因浓度.结果 在硬膜外注药结束后10～22 min60例胎儿娩出,新生儿Apgar评分均≥7分,脐动脉血Ph值均≥7.25.娩出时母体静脉血与脐静脉血血浆左旋布比卡因浓度分别为0.35 ±0.24、(0.24±0.21)μg/ml,脐静脉血与母体静脉血血浆左旋布比卡因浓度的比值为0.7 ±0.3.结论 宫产术病人硬膜外左旋布比卡因可通过胎盘,脐静脉血与母体静脉血左旋布比卡因浓度的比值为0.7.     

Anesthetic management of parturients with Marfan syndrome

Ten pregnancies and 7 deliveries in 5 patients of Marfan syndrome were managed at our institution. Three patients were delivered with a cesarean section under general anesthesia, and one was delivered under epidural anesthesia. Three underwent vaginal delivery with epidural anesthesia. Two patients selected induced abortion, and one had a spontaneous abortion. Six of 7 neonates and all 5 mothers survived without any sequela. One had intrauterine fetal death due to dissection of aortic aneurysm. Simultaneous cesarean section and cardiovascular operation under cardiopulmonary bypass were performed in one case. In the parturient without progress of cardiovascular complication during pregnancy, painless labor under epidural anesthesia is our first choice to minimize hemodynamic derangement. Invasive arterial blood pressure and central venous pressure were monitored in all cases of vaginal delivery for tight hemodynamic control. Epidural anesthesia is also preferred in cases of elective cesarean section for obstetric indication. Emergency cesarean sections are performed in the cases of progressive dissection and urgent obstetric indication. General anesthesia was induced with fentanyl and midazolam to minimize cardiovascular response to tracheal intubation. We emphasize that evaluation of cardiovascular status and multidisciplinary approach are the key in the anesthetic management of parturients with Marfan syndrome.     

不同麻醉下老年高血压患者围术期心肌损伤的比较

目的 比较不同麻醉下老年高血压患者围术期心肌损伤的程度,为老年高血压患者选择适宜的麻醉方法.方法 择期行胸外科手术的老年高血压患者36例,年龄64岁,ASA Ⅱ或Ⅲ级,高血压Ⅱ级,高血压危险程度为中、高危险组,随机分为七氟醚组(S组)、异氟醚组(Ⅰ组)和异丙酚组(P组),每组12例.插管成功后至术毕,S组和I组呼气末吸入麻醉药浓度分别为1.7%、1.2%;P组静脉靶控输注异丙酚,血浆靶浓度2～3μg/ml.分别于麻醉前、气管插管后、手术探查后、拔除气管导管后即刻记录心电图ST段水平.于麻醉前、手术开始1 h、术毕、术后3、6、12、24 h抽取上肢静脉血,采用ELISA法测定血浆心肌肌酸激酶同工酶(CK-MB)活性和心肌肌钙蛋白I(cTnI)、白细胞介素-6(IL-6)、C反应蛋白(CRP)、可溶性细胞间粘附分子-1(sICAM-1)的浓度.结果 拔除气管导管后即刻P组ST段水平明显低于S组和I组(P<0.05);与麻醉前比较,手术开始至术毕24 h各组血浆CK-MB活性、cTnI、IL-6、CRP和slCAM-1浓度明显升高(P<0.05);S组和I组术后24 h血浆cTnI,IL-6、CRP和sICAM浓度明显低于P组(P<0.05).结论 采用七氟醚或异氟醚复合麻醉时较采用异丙酚复合麻醉时老年高血压患者心肌损伤程度轻,围术期的炎性反应减轻;老年高血压患者宜采用吸人麻醉.     

Detection of intraoperatiye myocardial ischaemia — a comparison among electrocardiographic,myocardial metabolic,and haemodynamic measurements in patients with reduced ventricular function

This study determined the sensitivity and specificity of haemodynamic and ECG monitors to detect the development of intraoperative myocardial ischaemia utilizing myocardial lactate production as the standard. In 29 patients with reduced ejection fraction (0.27–0.50) undergoing coronary artery revascularization, measurements were made at the awake, post-induction, post-intubation, first skin incision, post-sternotomy, preprotamine, immediately post-cardiopulmonary bypass, and skin suture intervals. At each interval, measurement of a haemo-dynamic profile (including pulmonary artery occlusion (PAOP) and central venous (CVF) pressures, heart rate, and pressure rate quotient); myocardial lactate extraction and flux; changes in ST segments in ECG leads, V₅ and II utilizing a Siemens 1280® intraoperative monitor, and a Marquette 8500® Hotter monitor utilizing leads V₅, V₂, and AVF were made. “Ischaemia” was considered to be present when myocardial lactate production (MLP) occurred, PAOP or CVP increased by 5 mmHg above the baseline value, the pressure rate quotient was <1, or ST segment deviation (>1 mm) occurred in any lead for >1 min. Variables positive when MLP was positive were the pressure rate quotient (sensitivity 32.8%, specificity 71.9%), CVP (sensitivity 10.9%, specificity 92.6%), and PAOP (sensitivity 1.6%, specificity 99.2%). Holter monitoring had a 100% positive predictive value but poor sensitivity (1.6%). The ECG (Lead V₅ + II) measures of ischaemia were insensitive (17.5%) and relatively non-specific (87.7%). We conclude that, in this patient group and using myocardial lactate production as the standard, the pressure rate quotient, elevations in CVP or PAOP, or ST segment changes are insensitive measures of intraoperative myocardial ischaemia.     

II: Perioperative Holter monitoring: clinical relevance and practice

Perioperative, mostly silent ischaemia in patients with coronary heart disease is difficult to detect by clinical examinations. Methods. During the clinical evaluation (part I of this study) we monitored patients with prior myocardial infarction (MI) by continuous electrocardiographic (ECG) recording from the evening before until the first 24?h after operation. Excluded from Holter ECG studies were patients with a bundle branch block, pacemaker, valvular heart disease, cardiomyopathy, severe hypokalaemia, and digitalis treatment. Data were recorded with a Holter 8500 recorder (Marquette Electronics) using modified V2, V4, and V5 leads (Fig. 1). Holter tapes were analysed twice with a Holter computing system (Software 5.8, Marquette Electronics), first by a blinded technician and then by the authors themselves. We defined the following criteria as pathological ST segment changes and as ischaemic episodes [7]: horizontal or downsloping ST depression of at least 1?mm or elevation of 2?mm of at least 1?min duration measured at the J-point plus 60?ms. To quantify individual levels of ischaemia we used the definition “ischaemic load” [3]: ischaemic min/h monitored per patient. The statistic evaluation did not differ from that used in part I. Results. Out of 160 patients, 100 could be examined by Holter monitoring. Because of technical problems we could not record a Holter ECG in 2 of 6 patients with reinfarction. We found one or more perioperative episodes of ST-segment depression in 25 patients (25%). Ischaemic episodes were detected in 15 patients preoperatively, in 12 intraoperatively, and in 10 postoperatively. Three patients had ischaemic episodes during all periods. Patients with pathological ST segments suffered significantly more reinfarctions (3 of 25 vs. 1 of 75 patients) and were older (mean age difference 7 years, P<0.05). Patients with ischaemic episodes and a clinical diagnosis of reinfarction (n=3) demonstrated a dramatic postoperative increase in ischaemic load. Preoperative use of beta-blocking agents did not influence the incidence of ischaemic events. The sensitivity of postoperative Holter ECG monitoring in the diagnosis of reinfarction was 50%, the specificity 92%. Conclusions. Perioperative Holter ECG monitoring is time-consuming, expensive, not very sensitive, and therefore not generally applicable for all patients with prior MI.