Impact of loss of high-molecular-weight von Willebrand factor multimers on blood loss after aortic valve replacement

BACKGROUND

Severe aortic stenosis is associated with loss of the largest von Willebrand factor (vWF) multimers, which could affect primary haemostasis. We hypothesized that the altered multimer structure with the loss of the largest multimers increases postoperative bleeding in patients undergoing aortic valve replacement.

METHODS

We prospectively included 60 subjects with severe aortic stenosis. Before and after aortic valve replacement, vWF antigen, activity, and multimer structure were determined and platelet function was measured by impedance aggregometry. Blood loss from mediastinal drainage and the use of blood and haemostatic products were evaluated perioperatively.

RESULTS

Before operation, the altered multimer structure was present in 48 subjects (80%). Baseline characteristics and laboratory data were similar in all subjects. The median blood loss after 6 h was 250 (105-400) and 145 (85-240) ml in the groups with the altered and normal multimer structures, respectively (P=0.182). After 24 h, the cumulative loss was 495 (270-650) and 375 (310-600) ml in the groups with the altered and normal multimer structures, respectively (P=0.713). Multivariable analysis revealed no significant influence of multimer structure and platelet function on bleeding volumes after 6 and 24 h. After 24 h, there was no obvious difference in vWF antigen, activity, and multimer structure in subjects with and without the altered multimer structure before operation or in subjects with and without perioperative plasma transfusion.

CONCLUSIONS

The altered vWF multimer structure before operation was not associated with increased bleeding after aortic valve replacement. Our findings might be explained by perioperative release of vWF and rapid recovery of the largest vWF multimers.

Bupivacaine concentrations in the lumbar cerebrospinal fluid of patients during spinal anaesthesia

BACKGROUND

Data on bupivacaine concentrations in the cerebral spinal fluid (CSF) during spinal anaesthesia are scarce. The purpose of this study was to determine the concentration of bupivacaine in the lumbar CSF of patients with an adequate level of spinal anaesthesia after injection of plain bupivacaine 0.5%.

METHODS

Sixty patients with an adequate level of spinal block after standardized administration of plain bupivacaine 20 mg in men and of 17.5 mg in women were studied. To measure the CSF bupivacaine concentration, we performed a second lumbar spinal puncture and obtained a CSF sample at a randomized time point 5-45 min after the bupivacaine injection. In addition, we calculated the half-life of bupivacaine in the CSF and tested the hypothesis that the level of spinal block is related to the lumbar CSF bupivacaine concentration.

RESULTS

Men and women had CSF bupivacaine concentrations ranging from 95.4 to 773.0 microg ml(-1) (median 242.4 microg ml(-1)) and from 25.9 to 781.0 microg ml(-1) (median 187.6 microg ml(-1)), respectively. The large variability of bupivacaine concentrations obtained at similar times after subarachnoid administration made calculation of a meaningful half-life of bupivacaine in CSF impossible. There was no association between CSF bupivacaine concentration and spinal block level, and CSF bupivacaine concentrations for the same spinal block level differed between patients by six-fold.

CONCLUSIONS

There is a large variability of CSF bupivacaine concentrations in patients with an adequate level of spinal anaesthesia.

Randomized clinical trial of moxonidine in patients undergoing major vascular surgery

Background

Myocardial ischaemia is the leading cause of perioperative morbidity and mortality after surgery in patients with coronary artery disease. The aim of this study was to evaluate the effects of moxonidine, a centrally acting sympatholytic agent, on perioperative myocardial ischaemia and 1-year mortality in patients undergoing major vascular surgery.

Methods

In this double-blind, placebo-controlled two-centre trial, 141 patients were randomly assigned to receive moxonidine or placebo on the morning before surgery and on the following 4 days. Levels of cardiac troponin I (cTnI) were analysed before surgery and on days 1, 2, 3 and 7 thereafter. Holter electrocardiograms were recorded for 48 h starting before the administration of the study drug. Patients were followed daily during admission and by telephone interview 12 months after surgery.

Results

The incidence of raised perioperative cTnI levels or alteration in the ST segment in the Holter electrocardiogram or both was 40 per cent in the moxonidine group and 37 per cent in the placebo group (P = 0·694). All-cause mortality rates within 12 months were 10 per cent in the moxonidine group and 11 per cent in the placebo group (P = 0·870).

Conclusion

Small oral doses of moxonidine did not reduce the incidence of perioperative myocardial ischaemia and had no effect on mortality in patients undergoing vascular surgery. Registration number: NCT00244504 (http://www.clinicaltrials.gov).

Intra-operative myocardial ischaemia cannot be detected by analysis of transmitral inflow patterns in patients undergoing off-pump coronary surgery

BACKGROUND AND OBJECTIVE

Transmitral inflow patterns have been used for detection of myocardial ischaemia. However, its diagnostic value has not been tested in anaesthetized and mechanically ventilated patients undergoing coronary artery bypass graft surgery.

METHODS

Transmitral inflow patterns were studied by transoesophageal Doppler echocardiography in 43 patients undergoing coronary artery bypass graft surgery without cardiopulmonary bypass after opening of the sternum (baseline) and during grafting of the left anterior descending artery. Peak early (E) and peak late (A) transmitral velocities and their ratio (E/A) were recorded. Myocardial ischaemia was defined by standard criteria using two-dimensional echocardiography and seven-lead electrocardiogram.

RESULTS

Thirty-one patients (64 +/- 8 yr, 9 women) fulfilled the predefined inclusion criteria for analysis. During distal revascularization, 16 patients showed myocardial ischaemia and 15 did not. The use of vasoactive drugs, haemodynamic findings and transmitral inflow patterns were similar in both groups at baseline and during grafting. In the ischaemic group, E was 67.1 +/- 13.9 cm s-1 at baseline and 69.5 +/- 23.2 cm s-1 during grafting, and the E/A ratios were 1.3 +/- 0.3 and 1.4 +/- 0.9, respectively. In the non-ischaemic group, E was 64.0 +/- 17.1 cm s-1 at baseline and 60.9 +/- 14.8 cm s-1 during grafting, and the E/A ratios were 1.4 +/- 0.7 and 1.2 +/- 0.3, respectively.

CONCLUSIONS

Analysis of Doppler findings of transmitral inflow patterns did not allow for detection of myocardial ischaemia during surgical revascularization of the myocardium.

The accuracy of non-invasive carbon dioxide monitoring: a clinical evaluation of two transcutaneous systems

We determined the accuracy of two transcutaneous carbon dioxide monitoring systems (SenTec Digital Monitor with V-Sign Sensor and TOSCA 500 with TOSCA Sensor 92) for the measurement of single values and trends in the arterial partial pressure of carbon dioxide in 122 adult patients during major surgery and in 50 adult patients in the intensive care unit. One or several paired measurements were performed in each patient. The first measurement was used to determine the accuracy of a single value of transcutaneous carbon dioxide; the difference between the first and the last measurements was used to analyse the accuracy and to track trends. We defined a 95% limit of agreement of <or=1 kPa as being clinically useful. There was insufficient agreement between transcutaneous carbon dioxide partial pressure values derived from the two systems and arterial carbon dioxide values for both single values and trends as defined by our suggested limit of agreement. We conclude that these systems cannot replace conventional blood gas analysis in the clinical setting studied.

Predictors of long-term mortality and cardiac events in patients with known or suspected coronary artery disease who survive major non-cardiac surgery

The aim of this prospective study was to assess predictors of long-term outcome in patients with documented or suspected coronary artery disease who survive major non-cardiac surgery. The impact of patients' comorbidities, pre-operative heart rate variability and postoperative increase in cardiac troponin I on all-cause mortality and major cardiac events within 2 years was explored using multivariable logistic regression. Six of 173 patients died within the first month after surgery and were excluded from the study. Thirty-four of 167 patients (20%) died 1-24 months after surgery. Independent predictors of all-cause mortality were history of congestive heart failure (odds ratio 6.4 [95%, confidence interval 1.7-24]), pre-operatively depressed heart rate variability (odds ratio 6.4 [95%, confidence interval 1.9-21]), and age > 70 years (odds ratio 4.5 [95%, confidence interval 1.2-16]). In contrast, postoperative elevation of cardiac troponin I did not independently predict all-cause mortality or major cardiac events.

Effects of halothane, sevoflurane and propofol on left ventricular diastolic function in humans during spontaneous and mechanical ventilation

BACKGROUND

There is limited knowledge of the effects of anaesthetics on left ventricular (LV) diastolic function in humans. Our aim was to evaluate these effects in humans free from cardiovascular disease.

METHODS

Sixty patients (aged 18-47 yr) who had no history or signs of cardiovascular disease were randomized to receive general anaesthesia with halothane, sevoflurane or propofol. Echocardiography was performed at baseline and during spontaneous respiration at 1 minimum alveolar concentration (MAC) of the inhalational agents or propofol 4 microg ml(-1) (step 1), and repeated during positive-pressure ventilation with 1 and 1.5 MAC of the inhalational agents or with propofol 4 and 6 microg ml(-1) (steps 2a and 2b). Analysis of echocardiographic measurements focused on heart rate corrected isovolumic relaxation time (IVRT(c)) and early diastolic peak velocity of the lateral mitral annulus (E(a)).

RESULTS

IVRT(c) decreased from baseline to step 1 in the halothane group (82 [95% CI, 76-88] ms and 74 [95% CI, 68-80] ms respectively; P=0.02), remained stable in the sevoflurane group (78 [95% CI, 72-83] ms and 73 [95% CI, 67-81] ms; n.s.) and increased in the propofol group (80 [95% CI, 74-86] ms and 92 [95% CI, 84-102] ms; P=0.02). E(a) decreased in the propofol group only (18.8 [95% CI, 16.5-19.9] cm s(-1) and 16.0 [95% CI, 14.9-17.9] cm s(-1); P=0.003). From step 2a to step 2b, IVRT(c) increased further in the propofol group (109 [95% CI, 99-121] ms and 119 [95% CI, 99-135] ms; P=0.04) but remained stable in the other two groups. E(a) did not change from step 2a to step 2b.

CONCLUSIONS

Halothane and sevoflurane did not impair LV relaxation, whereas propofol caused a mild impairment. However, the impairment by propofol was of a magnitude that is unlikely to cause clinical diastolic dysfunction.

Doppler indices of diastolic transmitral flow velocity are invalid indicators of myocardial ischaemia during high-dose dobutamine infusion in anaesthetized patients

BACKGROUND AND OBJECTIVE

Doppler echocardiography of diastolic transmitral flow velocity is more sensitive for the detection of myocardial ischaemia in awake patients than echocardiographic analysis of systolic wall motion. However, its diagnostic value in anaesthetized patients is unknown.

METHODS

Doppler indices of diastolic transmitral flow velocity previously found to be highly sensitive for detecting ischaemia in awake patients were studied in 72 anaesthetized patients with documented coronary artery disease undergoing dobutamine stress echocardiography. These Doppler indices were compared with standard echocardiographic and electrocardiographic criteria for ischaemia.

RESULTS

Sixty-five patients showed evidence of ischaemia by standard echocardiographic and/or electrocardiographic criteria, and seven patients did not. Regardless of evidence of ischaemia by standard criteria, the Doppler indices changed similarly in both groups. Accordingly, only a minority of anaesthetized patients displayed the changes in Doppler indices of diastolic transmitral flow previously suggested to be sensitive for detecting ischaemia.

CONCLUSIONS

The results do not confirm the diagnostic value of Doppler echocardiography of diastolic transmitral flow velocity for detecting ischaemia in anaesthetized patients undergoing dobutamine stress echocardiography during positive-pressure ventilation of the lungs.

The diagnostic value of Doppler echocardiographic indexes of diastolic filling for detecting demand ischemia in anesthetized patients

In awake patients, Doppler indexes of transmitral flow velocities have been shown to be more sensitive for detection of myocardial ischemia than echocardiographic evaluation of systolic wall-motion. The diagnostic value of these indexes in anesthetized patients is unknown. It might differ from that in awake patients because anesthetics and sympathomimetic drugs, which are commonly used in surgical patients with coronary artery disease (CAD), independently affect transmitral flow velocities.

METHODS

Several previously published transmitral Doppler echocardiographic indicators of ischemia (marked decreases in the ratio of peak early [E] to peak atrial [A] filling velocity [E/A], in the ratio of early to atrial time-velocity integral [E(I)/A(I)], in E, in E acceleration, and in total diastolic time-velocity integral) were compared with standard wall-motion analysis and ST-segment analysis during dobutamine stress echocardiography (DSE) in 17 anesthetized patients with CAD and 7 age-matched control patients at low risk of CAD.

RESULTS

All patients with CAD but no control patients showed new systolic wall-motion abnormalities and/or ST-segment changes. Decreases of >10% in E/A and E(I)/A(I) were found in 88% and 71% of the patients with CAD and in 71% and 100% of the control patients, respectively. These decreases were found during dobutamine infusion at as low as 10 mcg/kg/min in several control patients. None of the other studied Doppler indexes were found useful to detect ischemia.

CONCLUSIONS

Doppler echocardiography of diastolic transmitral flow velocities is of no appreciable diagnostic value for detecting ischemia in anesthetized patients who receive dobutamine at 10-40 mcg/kg/min.

Competence of the internal jugular vein valve is damaged by cannulation and catheterization of the internal jugular vein

BACKGROUND

Experimental results suggest that the competence of the internal jugular vein (IJV) valve may be damaged when the IJV is cannulated for insertion of a central venous catheter. It has further been hypothesized that the risk of causing incompetence of the proximally located valve might be reduced by using a more distal site for venous cannulation. The present study evaluated these hypotheses in surgical patients.

METHODS

Ninety-one patients without preexisting incompetence of the IJV valve were randomly assigned to undergo distal or proximal IJV cannulation (> or = 1 cm above or below the cricoid level, respectively). Color Doppler ultrasound was used to study whether new valvular incompetence was present during Valsalva maneuvers after insertion of a central venous catheter, immediately after removal of the catheter, and, in a subset of patients, several months after catheter removal, when compared with baseline findings before cannulation of the IJV.

RESULTS

Incompetence of the IJV valve was frequently induced both by proximal and distal cannulation and catheterization of the IJV. Its incidence was higher after proximal than after distal cannulation (76% vs. 41%; P < 0.01) and tended to be so after removal of the catheter (47% vs. 28%; P = 0.07). Valvular incompetence persisting immediately after removal of the catheter did not recover within 8-27 months in most cases.

CONCLUSIONS

Cannulation and catheterization of the IJV may cause persistent incompetence of the IJV valve. Choosing a more distal site for venous cannulation may slightly lower the risk of causing valvular incompetence but does not reliably avoid it.

Transthoracic echocardiography for perioperative haemodynamic monitoring

Transoesophageal echocardiography (TOE) is valuable for perioperative monitoring in patients at risk from haemodynamic disturbance. However, its use is not practicable in patients undergoing surgical procedures under regional anaesthesia. We describe two cases showing that transthoracic echocardiography (TTE) has the same advantages as TOE and thus may be valuable for monitoring awake patients. TTE should be considered when extended perioperative haemodynamic monitoring is needed but TOE is not possible.

High incidence of intravenous thrombi after short-term central venous catheterization of the internal jugular vein

STUDY OBJECTIVE

To assess incidence and characteristics of intravenous (i.v.) thrombi associated with short-term central venous catheterization through the internal jugular vein.

DESIGN

Prospective clinical study.

SETTING

University hospital.

PATIENTS

81 patients undergoing cardiac surgery.

INTERVENTIONS

A triple-lumen central venous catheter was inserted into the right internal jugular vein immediately before surgery and removed 3 to 4 days later. Heparin at an i.v. dose of 15,000 IU/24 hours was started 6 hours after surgery and continued until the first postoperative morning, followed by subcutaneous low molecular weight heparin 5,000 IU/day in combination with oral aspirin 100 mg/day.

MEASUREMENTS AND MAIN RESULTS

Anatomy of the internal jugular vein and i.v. blood flow were studied using two-dimensional and color Doppler ultrasonography before insertion of the catheter and after its removal. Thrombi were found in 45 patients (56%). Twenty-five of these thrombi (56%) had the shape of a sleeve, and 20 thrombi (44%) were compact. Length of the thrombi was 1.4 +/- 0.8 cm (mean +/- SD). Half of the thrombi floated with venous blood flow and half were stable. Neither impaired venous blood flow nor clinical signs of embolism or sepsis was found. Follow-up studies in eight patients revealed that the thrombi had not disappeared 5 days after removal of the catheter but had become smaller.

CONCLUSION

The incidence of i.v. thrombi associated with short-term catheterization of the internal jugular vein was high despite prophylactic anticoagulation. This finding reaffirms the importance of removing central venous catheters as soon as clinically possible. Additional studies using specific outcome tests are needed to thoroughly assess the clinical importance of this finding.

Epidural abscess complicating epidural anesthesia and analgesia. An analysis of the literature

BACKGROUND

Epidural abscess is a serious complication of epidural block. Because of its low incidence, the risk factors and the symptoms and cause of epidural abscess related to epidural anesthesia and analgesia are not well known by anesthesiologists.

METHODS

A computer-assisted search of the literature on epidural catheter-related abscess was performed to describe the clinical course and bacteriology of this complication, to determine possible risk factors, and to assess the index of suspicion among physicians.

RESULTS

Forty-two patients with a catheter-related epidural abscess were identified. Only in 15 patients was the correct diagnosis considered initially. The time from insertion of the epidural catheter to symptoms varied between 1 and 60 d. Initial symptoms included back pain, fever, and leukocytosis. The time from symptoms to treatment was a few hours to 108 d. Interval from first symptoms to treatment was significantly longer in patients with persistent neurologic deficits compared with patients who completely recovered. Staphylococcus aureus was the most common etiologic agent. Outcome was reported in 39 patients, but only 19 made a full recovery.

CONCLUSION

The index of suspicion among anesthesiologists, other physicians and nurses taking care of patients with epidural catheters must be increased for this complication; this should shorten the interval from symptoms to treatment and lower the incidence of neurological sequelae.

Dobutamine stress echocardiography to detect inducible demand ischemia in anesthetized patients with coronary artery disease

BACKGROUND

A cardiac risk stratification test that can be performed during operation would be expected to give valuable information for the therapeutic management of patients who need urgent noncardiac surgery. This study was designed to evaluate the feasibility and safety of a dobutamine-atropine stress protocol to detect inducible demand ischemia in anesthetized patients.

METHODS

A standard dobutamine-atropine stress protocol was performed in 80 patients with severe coronary artery disease during fentanyl-isoflurane anesthesia. Biplane transesophageal echocardiography and 12-lead electrocardiography were used to detect induced ischemia. After dobutamine testing, esmolol, nitroglycerin, or both were used to revert ischemia and any hemodynamic changes, as appropriate.

RESULTS

The protocol detected inducible ischemia or achieved the target heart rate in 75 of the 80 (94%) patients. None of the prospectively defined adverse outcomes, such as cardiovascular collapse, severe ventricular arrhythmia, persistent (> or =5 min) ischemia, or hemodynamic instability, occurred in any of the patients. Ischemia was induced and detected in 73 of the 80 (91%) patients.

CONCLUSION

Dobutamine stress echocardiography is feasible in anesthetized patients with severe coronary artery disease. The lack of serious complications and the high sensitivity to detect inducible ischemia in this patient population provide the basis for further evaluation of the safety and diagnostic value of dobutamine stress echocardiography during general anesthesia in larger studies of patients at risk for coronary artery disease undergoing noncardiac surgery.

Efficacy of specific aseptic precautions for preventing propofol-related infections: analysis by a quality-assurance programme using the explicit outcome method

Specific aseptic precautions have been recommended for preventing infectious complications of propofol because its lipid base can support bacterial growth if contaminated. To study whether the precautions used at our institution prevent propofol-related infections, we retrospectively analysed the data covering 1 January, 1995 until 30 June, 1996 held in our quality-assurance database. The database contains prospectively collected, detailed and standardized information of each patient's risk factors, anaesthetic and surgical data, and postoperative outcome. Surgical patients who had received propofol for anaesthesia did not have a higher incidence of postoperative infection, thus demonstrating the efficacy of our aseptic precautions.

Acute hypovolemia may cause segmental wall motion abnormalities in the absence of myocardial ischemia

New segmental wall motion abnormalities (SWMA) detected by echocardiography are considered sensitive and specific markers of myocardial ischemia. However, we have observed new SWMA during pacing-induced reductions in left ventricular filling, which resolved immediately with cessation of the atrial pacing and simultaneous restoration of filling. Therefore, we designed this study to determine whether acute reduction in filling can induce new SWMA in the absence of ischemia. Institution of cardiopulmonary bypass was used as a clinical model of acute reduction in filling, and a beat-by-beat analysis of left ventricular contraction, filling, blood pressures, and electrocardiogram was performed when the drainage of blood to the cardiopulmonary bypass machine rapidly emptied the heart. Acute reduction in filling induced new SWMA in 4 of 38 study patients. All 4 patients had preexisting abnormalities of left ventricular contraction, but translocation of these preexisting SWMA did not explain the new SWMA, nor did myocardial ischemia. We conclude that acute reduction in left ventricular filling can cause new SWMA in the absence of ischemia. This finding limits the usefulness of new SWMA as a marker of ischemia in the presence of acute reduction in filling, such as that secondary to severe hypovolemia.

IMPLICATIONS

This study documented that acute reduction in cardiac filling can be associated with new systolic wall motion abnormalities detected by transesophageal echocardiography in the absence of documented myocardial ischemia. These findings indicate that segmental wall motion may not be a valid marker for ischemia in the setting of acute hypovolemia.

The inverse Nehb J lead increases the sensitivity of Holter electrocardiographic monitoring for detecting myocardial ischemia

A major reason for the relatively low sensitivity of Holter electrocardiography (ECG) for detecting ischemia is that the sensitivity of bipolar leads used for Holter ischemia monitoring has not been systematically evaluated, making lead selection difficult. Therefore, this study evaluated the sensitivity of 6 bipolar Holter leads for detecting ischemia during percutaneous transluminal coronary angioplasty. Seventy-five patients, each of whom had > 1 mm ST-segment elevation on an intracoronary electrocardiogram from the myocardium distal to the stenosis during balloon occlusion, were studied for the occurrence of > or = 1 mm ST-segment elevation or depression on the simultaneously recorded Holter leads II, III, aVF, CM5, CR4, and inverse Nehb J. The study found that the inverse lead Nehb J provided a significantly higher overall sensitivity for detecting myocardial ischemia than Holter leads II, III, aVF, CM5, and CR4. Also, the use of inverse lead Nehb J significantly increased the sensitivity of 2- and 3-lead Holter ischemia monitoring. These findings were based on a significantly higher sensitivity of inverse lead Nehb J for detecting ischemia induced by transient occlusion of the left anterior descending coronary artery and a slightly higher sensitivity for detecting ischemia induced by occlusion of the left circumflex coronary artery. None of the bipolar leads studied provided a very high sensitivity for detecting ischemia induced by occlusion of the right coronary artery. These findings show that adequate lead selection can increase the sensitivity of Holter ischemia monitoring. Furthermore, the lack of a highly sensitive lead for detection of inferior ischemia indicates that further evaluation of bipolar leads is warranted.

Rapid atrial pacing for detecting provokable demand ischemia in anesthetized patients

A stress test that can be performed intraoperatively might be valuable for cardiac risk stratification in patients needing urgent noncardiac surgery and for early evaluation of coronary reserve in patients undergoing aortocoronary bypass surgery. Therefore, we evaluated the sensitivity and safety of rapid atrial pacing combined with electrocardiography and transesophageal echocardiography for inducing and detecting provokable demand ischemia in 20 anesthetized patients with multivessel coronary artery disease. Rapid atrial pacing induced ST segment changes or new segmental wall motion abnormalities (SWMA), which were defined as evidence of induced ischemia in 15 of the 20 patients. Unexpectedly, the new SWMA normalized during the first beat after abrupt cessation of pacing in three patients who did not show any ST segment changes. Simultaneously, left ventricular preload was severely decreased during pacing and recovered to baseline immediately when pacing was abruptly discontinued. Rapid atrial pacing was safe in all patients, but the target heart rate could not be achieved because of heart block or arterial hypotension in 4 of the 20 patients. These findings raise the question of whether rapid atrial pacing is the most appropriate approach for inducing provokable demand ischemia in anesthetized patients. However, its potential usefulness for predicting adverse cardiac outcomes has not been evaluated and would require larger studies. In addition, the immediate normalization of new SWMA after abrupt cessation of pacing in some patients calls into question the validity of new SWMA as evidence of myocardial ischemia when left ventricular preload is severely decreased.

[Long-term electrocardiography. Detection of low-grade myocardial infarction: sensitivity of 9 bipolar leads]

The sensitivity of ambulatory electrocardiography (Holter ECG) for detecting ischaemia is relatively low. A case report of an inferior infarction missed by three-lead Holter monitoring that included a modified lead aVF especially places its sensitivity for detecting inferior ischaemia and infarction in question. Therefore, the present study evaluated the sensitivity of nine bipolar Holter leads for detecting isolated inferior Q-wave infarctions, and compared the sensitivity of the modified leads II, III, and aVF of the Holter ECG with the sensitivity of the "corresponding" leads of the standard ECG.

METHODS

Sixteen patients, each of whom had a pathological Q-wave (> 0.04 s and > 0.1 mV) in at least two of the three standard ECG leads II, III, and aVF but in none of the other standard leads, were studied for the presence of a pathological Q-wave on the modified Holter leads II, III, aVF, CM2, CM5, CR4, Frank Z, Nehb D, and inverse Nehb J.

RESULTS

Of the nine Holter leads, modified lead III provided the highest sensitivity for detecting inferior Q-wave infarctions, followed by lead Frank Z; leads CR 4 and inverse Nehb J were only slightly less sensitive. In contrast, modified leads II and aVF were significantly less sensitive than modified lead III. Modified bipolar lead aVF of the Holter ECG was significantly less sensitive than the "corresponding" lead aVF of the standard ECG, whereas modified leads II and III provided similar sensitivities for detecting inferior Q-wave infarctions as the "corresponding" leads of the standard ECG.

CONCLUSIONS

The significantly lower sensitivity of modified lead aVF for detecting inferior Q-wave infarctions compared with standard lead aVF shows that the sensitivity of a Holter ECG lead cannot be deduced from that of the "corresponding" standard ECG lead. Moreover, the significantly higher sensitivity of modified lead III compared with modified leads II and aVF shows that lead selection is important for Holter monitoring.

Repeated dural punctures increase the incidence of postdural puncture headache

Previous studies have failed to find a significant correlation between the number of dural punctures and the incidence of postdural puncture headache (PDPH), questioning the hypothesis that leakage of cerebrospinal fluid (CSF) through the dural tear is the cause of PDPH. We hypothesized that insufficient statistical power of these studies was the cause for this unexpected finding, and re-examined whether repeated dural punctures increase the incidence of PDPH by analyzing prospectively collected data on 8034 spinal anesthetics. Uneventful spinal anesthetics, including a single subarachnoid injection of local anesthetics, occurred in 7865 (97.9%) cases, whereas failed spinal anesthetics requiring repeated dural puncture for a second subarachnoid injection of local anesthetics occurred in 165 (2.1%) cases. The two groups were similar with regard to age, sex, and ASA physical status. We found that repeated dural punctures significantly increased the incidence of PDPH. We conclude that increased risk of PDPH is a disadvantage of performing a second subarachnoid injection of local anesthetics after a failed spinal anesthetic. Moreover, this result suggests that leakage of CSF through the dural tear is the most plausible cause of PDPH.

Paravascular lumbar plexus block: block extension after femoral nerve stimulation and injection of 20 vs. 40 ml mepivacaine 10 mg/ml

The goal of this prospective randomized study was to assess the extension of the "three-in-one" paravascular lumbar plexus block after femoral nerve stimulation and injection of 20 vs. 40 ml mepivacaine 10 mg/ml. Three-in-one blocks were achieved in 12 of 39 (31%) patients given 20 ml of 1% mepivacine (group 1), and 17 of 41 (41%) patients given 40 ml (Group 2) of the same solution (n.s.). The level of successful blockade at each nerve did not differ between groups. The femoral nerve was blocked in 92% vs. 93% of patients in groups 1 and 2, respectively; the obturator nerve in 62% vs. 78%; and the lateral cutaneous femoral nerve in 41% vs. 44%. We conclude that femoral nerve stimulation is effective in faciliating blockade in the femoral nerve but not the obturator or lateral cutaneous femoral nerve with the tested solution and volumes, and therefore not particularly effective for achieving complete 3-in-1 blockade. Within the clinically relevant range of 20-40 ml, the volume of mepivacaine 10 mg/ml does not appear to influence the extent of blockade.

Comparison of spinal and epidural anesthesia for patients younger than 50 years of age

To evaluate the respective clinical value of spinal anesthesia with 24-gauge Sprotte needles and epidural anesthesia for younger subjects, 202 patients younger than 50 yr were assigned randomly to undergo one of these two techniques for orthopedic, vascular, urologic, or plastic surgery. Failed blocks occurred in 5% in each group. Spinal anesthesia resulted in significantly less time to achieve sufficient spread of block; a significantly lower incidence of incomplete sensory block at level L5/S1, incomplete motor block, and pain during surgery; and a significantly lower incidence of postlumbar puncture backache (11% vs 30% after epidural anesthesia). The incidence of postdural puncture headache (PDPH) in the spinal and epidural groups was 7% and 4%, respectively (P = not significant), and patient satisfaction was 97% and 93% (P = not significant). Our results demonstrate the effectiveness of both techniques in younger patients, but show that the spinal technique is associated with fewer limitations, suggesting that factors other than PDPH should be considered when choosing between these two techniques.

In vitro effect of ephedrine, adrenaline, noradrenaline and isoprenaline on halothane-induced contractures in skeletal muscle from patients potentially susceptible to malignant hyperthermia

We have measured the effects of ephedrine, adrenaline, noradrenaline and isoprenaline on halothane-induced contractures in muscle biopsies from patients potentially susceptible to malignant hyperthermia (MH). At concentrations of 4-24 mmol litre-1, ephedrine induced in vitro contractures in halothane 0.44 mmol litre-1-prechallenged muscle, whilst adrenaline, noradrenaline and isoprenaline had no effect. There was a shift of the ephedrine concentration-response curve to the left and an increased maximum muscle contracture in the MH susceptible group compared with the MH negative group (P < 0.001). We conclude that ephedrine increased halothane-induced muscle contractures in vitro either by an unknown pharmacological mechanism or by an adrenergic stimulation which was different from those of the other investigated adrenoceptor agonists.

Lumbovertebral syndrome after extradural blood patch

We describe a patient who developed an immobilizing lumbovertebral syndrome after an extradural blood patch and who was hospitalized with a suspected extradural abscess. An infectious aetiology of the persistent backache could be excluded and the patient recovered with analgesics and physiotherapy. The probable aetiology is discussed.

[Diagnosis of susceptibility for malignant hyperthermia using in-vitro muscle contraction testing in Switzerland]

Malignant hyperthermia is a potentially fatal pharmacogenetic disorder triggered by volatile anesthetics (halothane, enflurane, isoflurane) and/or succinylcholine. The inheritance of malignant hyperthermia susceptibility is thought to be autosomal dominant and the incidence could be as high as 1:10,000. The only generally accepted diagnostic method at present involves a muscle biopsy followed by in-vitro halothane and caffeine contracture tests. 100 individuals from 45 families who were considered to be potentially malignant hyperthermia-susceptible were investigated from 1986 to 1990 by in-vitro muscle contracture tests using the protocol of the European Malignant Hyperthermia Group. Of 45 families analyzed, 28 had at least one person who was susceptible to malignant hyperthermia with a total of 64 malignant hyperthermia-susceptible individuals. 36 subjects in the 45 families were normal. In addition, our study shows that a femoral nerve block can be used in outpatients as a reliable anesthetic technique to perform biopsies from the vastus medialis muscle for malignant hyperthermia screening.