Bootstrap methods for statistical inference from stereological estimates of volume fraction

We suggest the use of bootstrap methods for inference from stereological estimates of volume fraction. An informal introduction to stereological estimation of volume fraction and to principles of bootstrap techniques is given. The bootstrap method is a robust computer-intensive resampling technique, based on independent random sampling from a data set with replacement. Bootstrap methods were used to estimate confidence intervals for volume fractions, and to test for a significant difference between estimated volume fractions from two samples. Two sampling designs are considered: independent replicated samples (visual fields) from a single object, and estimates of volume fraction from multiple independent objects. The methods are presented as worked examples on real data sets obtained from tumour pathology (mammary cancer, pancreatic cancer). The volume fraction of glandular lumina per total volume of the epithelial phase was chosen as target parameter. It indicates the degree of glandular differentiation in adenocarcinomas and is estimated as a ratio-of-means statistic with variable denominator within cases. The confidence intervals of the volume fraction estimated by the bootstrap method were slightly narrower than the parametrically calculated confidence intervals for all data sets. The outcomes of significance tests based on the bootstrap technique were unchanged as compared with classical tests based on the assumptions of normality and homoscedasticity of the data. Special attention was paid to the reproducibility of the bootstrap technique in replicated trials on the same data.

Statistical analysis of the three-dimensional structure of centromeric heterochromatin in interphase nuclei

Translocation of genes into the pericentromeric heterochromatin occurs during cellular differentiation and leads to a long-term silencing of these genes. Consequently, a structural remodelling of this heterochromatin compartment is observed during differentiation but this remains to be defined from a topological point of view. In a previous study, we analysed the three-dimensional (3D) distribution patterns of centromere clusters (chromocentres) by confocal scanning laser microscopy and found that differentiation of the promyelocytic leukaemia cell line NB4 along the neutrophil lineage is associated with a progressive clustering of centromeres. This clustering was reflected by a decreased number of detectable chromocentres, i.e. groups of centromeres with a distance below the diffraction-limited resolution of optical microscopy. The purpose of this study was to perform a statistical analysis of the 3D distribution of chromocentres in NB4 cells. Several point field characteristics (Ripley's K-function, L-function, pair correlation function, nearest-neighbour distribution function) were investigated to describe the topology of chromocentres during differentiation of NB4 cells. The pair correlation function revealed a higher frequency of chromocentre distances between 350 nm and 800 nm in undifferentiated NB4 cells as compared with differentiated cells. The L-function and the nearest-neighbour distribution function confirmed these results. These data imply the existence of intranuclear heterochromatin zones formed by functionally related centromeric regions. In view of the observed decrease in the number of detectable chromocentres during differentiation, we hypothesize that these zones with a diameter of 350-800 nm in undifferentiated NB4 cells contract into zones with a diameter below 350 nm in differentiated cells.

Pulse contour analysis versus thermodilution in cardiac surgery patients

BACKGROUND

Previous studies have demonstrated that there is a lack of agreement between intermittent cold bolus thermodilution (ICO) and a semicontinuous method with dilution of heat (CCO) in cardiac surgical patients following hypothermic extracorporeal circulation (HCPB). Therefore, the aim of the present study was to compare both ICO and CCO with continuous pulse contour analysis (PCCO): a method based on a fundamentally different principle of determining cardiac output (CO).

METHODS

A prospective criterion standard study of 25 cardiac surgery patients undergoing HCPB. Cardiac output was determined using the three methods (ICO, CCO, and PCCO) before and after HCPB up to 12 h after arrival on the ICU. Bias and precision were evaluated.

RESULTS

A total of 380 triple determinations of CO could be analyzed. During the entire study period bias PCCO-ICO was -0.14 l*/min (precision 1.16 l*/min) and bias CCO-ICO was -0.40 l*/min (precision 1.25 l*/min). Up to 45 min after bypass PCCO agreed with ICO (bias -0.21 l*/min, precision 1.37 l*/min), while bias CCO-ICO was -1.30 l*/min (precision 1.45 l*/min).

CONCLUSION

The agreement between PCCO and ICO in contrast to CCO in the first 45 min after HCPB indicates that CCO underestimates CO during this period.

Stress kinase inhibition modulates acute experimental pancreatitis

AIM: To examine the role of p38 during acute experimental cerulein pancreatitis.

METHODS: Rats were treated with cerulein with or without a specific JNK inhibitor (CEP1347) and/or a specific p38 inhbitor (SB203580) and pancreatic stress kinase activity was determined. Parameters to assess pancreatitis included trypsin, amylase, lipase, pancreatic weight and histology.

RESULTS: JNK inhibition with CEP1347 ameliorated pancreatitis, reducing pancreatic edema. In contrast, p38 inhibition with SB203580 aggravated pancreatitis with higher trypsin levels and, with induction of acinar necrosis not normally found after cerulein hyperstimulation. Simultaneous treatment with both CEP1347 and SB203580 mutually abolished the effects of either compound on cerulein pancreatitis.

CONCLUSION: Stress kinases modulate pancreatitis differentially. JNK seems to promote pancreatitis development, possibly by supporting inflammatory reactions such as edema formation while its inhibition ameliorates pancreatitis. In contrast, p38 may help reduce organ destruction while inhibition of p38 during induction of cerulein pancreatitis leads to the occurrence of acinar necrosis.

[Cisatracurium in coronary bypass operations--a comparison with pancuronium. Hemodynamic and neuromuscular effects in patients under chronic beta blocker treatment]

OBJECTIVE

The aim of the study was to compare haemodynamic and neuromuscular effects of cisatracurium and pancuronium in patients undergoing coronary artery bypass grafting (ASA III, good or moderately impaired LV function) who were chronically medicated with beta-adrenergic blocking agents.

METHODS

60 Patients were randomly assigned in a double-blind fashion to receive sufentanil/midazolam/etomidate and either pancuronium (2xED95, group P) or cisatracurium (2xED95, group C2 and 4xED95, group C4). Haemodynamic variables were measured using arterial and pulmonary arterial catheters, neuromuscular transmission was measured using electromyography.

RESULTS

The heart rate was significantly lower in group C2 (50.2 +/- 6.8 bpm) and in group C4 (54.3 +/- 11 bpm) than in the pancuronium group (62.4 +/- 13.2 bpm) 3 min after induction of anaesthesia and until 60 min after induction. None of the other haemodynamic parameters showed any difference between groups. Onset time was 5.22 +/- 3.43 min in group P, 6.42 +/- 2.1 min in group C2 and 2.92 +/- 1.2 min in group C4.

CONCLUSION

Under high-dose opioid induction, bradycardia must be considered if cisatracurium is administered to cardiac surgery patients.

Map kinase phosphatases (MKP's) are early responsive genes during induction of cerulein hyperstimulation pancreatitis

Mitogen-activated protein kinase (MAPK) family members such as c-jun N-terminal kinase (JNK) may act as signal transducers early during pancreatitis development and evidence indicates that MAPK phosphatases (MKP) downregulate MAPK. We therefore investigated expression and regulation of pancreatic MKP in vivo. Pancreatic MKP mRNA levels were near or below the detection threshold in unstimulated animals. Cerulein hyperstimulation strongly induced MKP-1, MKP-3, and MKP-5 expression, peaking 30 to 60 min after treatment. Thus, MKP's clearly are early responsive genes during pancreatitis induction. Interestingly, inhibition of MKP-1 expression by Ro-31-8220 maximally induced activation of JNK but not of p38 and ERK in acutely isolated acini. These effects indicate that JNK may indeed be a preferred MKP-1 substrate in vivo.

Vascular tracheobronchial compression syndromes-- experience in surgical treatment and literature review

Between January 1988 and December 1997 a total of 22 patients (age: 8 days-46 years) were operated for vascular airway compression syndromes with respiratory insufficiency. Vascular anomalies in tracheal compression were double aortic arch in 7 patients, (2 previously operated elsewhere), right aortic arch + left ligamentum arteriosum in 1, and pulmonary artery sling in 3. Three of these patients had secondary long-segment tracheomalacia. Compression of trachea and a main bronchus existed in 2 patients with right aortic arch + left ligamentum. Isolated main bronchus obstruction was present in 9 patients (abnormal insertion of ligamentum arteriosum in 1, status post (s.p.) previous operation for PDA in 4, s. p. surgery for coarctation in 1, right aortic arch + left ligamentum arteriosum in 2, and right lung aplasia + left ligamentum in 1). 3 of these cases had secondary long-segment bronchomalacia. All patients had a complex respiratory anamnesis [long-term intubation in 7, s.p. tracheostomy in 2 (over 3 months - 3 years), and progressive respiratory insufficiency in 13). In tracheal compression, surgical correction included transsection of the underlying ring or sling components (with additional anterior aortic arch translocation in 5 patients resection-reimplantation of left pulmonary artery in 3, segmental tracheal resection in 1, and external tracheal suspension in 2). In the 2 cases with compression of the trachea and a main bronchus, aortic "extension" by a prosthetic tube was necessary. In isolated main bronchus obstruction, surgical decompression basically consisted of transsection of the ligamentum arteriosum or resection of its scarry remnant forming the "corner point" of a compression between aorta and pulmonary artery. In 3 patients with secondary long-segment malacia, additional external bronchus suspension was performed. Effective decompression and re-expansion of the airway segment concerned was achieved, and was demonstrated by intraoperative endoscopy in all patients. There were 3 postoperative deaths (sepsis 2; massive, irreversible edema of the tracheal mucosa 1). Of the 19 surviving patients 16 could be extubated between the 1st and 17th (mean = 7.5) postoperative day. In 1 case the preoperative long-term tracheostomy had to be left in place for inoperable additional laryngeal stricture. 2 patients had to be reoperated (segmental cervical tracheal resection after 5 months for primary long-term intubation-related subglottic stenosis in 1, esophageal decompression for residual dysphagia after 57 months related to a traction phenomenon at the right descending aorta in the other), both with gratifying results. In all other patients clinical, endoscopic, and radiographic examinations (follow-up = 2 months - 6 years) demonstrate good results.

External stabilization of long-segment tracheobronchomalacia guided by intraoperative bronchoscopy

BACKGROUND

Symptomatic obstruction of long-segment tracheal or bronchial portions either related to congenital instability or secondary to vascular compression are rare malformations, which remain difficult to manage. A method of external tracheal or bronchial stabilization is described.

METHODS

From July 1992 to April 1995, 7 children (age range, 4 months to 4 years; mean age, 19 months) and 1 adult (age, 46 years) were operated on for severe respiratory insufficiency. In 4 cases of congenital tracheal instability, 2 children had associated type IIIb esophageal atresia. Both children with esophageal atresia had previous operations (two and three times, respectively): 1 child had aortopexy and division of a patent ductus arteriosus and another child had distal tracheal resection elsewhere, both without relief of malacia. All children were intubated and ventilated since birth for 11 to 15 months. Secondary tracheobronchomalacia due to vascular compression was seen in 4 patients caused by double aortic arch (n = 2) and persisting ligamentum arteriosum after previous ligation of a patent ductus arteriosus (n = 2), with 1 child ventilated thereafter for 5 months. Operation was performed with the aid of extracorporeal circulation in all patients but 1, and consisted of transection of vascular rings and persistent ligamentum Botalli (n = 5), closure of multiple ventricular septal defects (n = 1) and extensive mobilization of the tracheobronchial tree as well as the great arteries. External stabilization of the severely dysplastic distal trachea (n = 6) or left main bronchus (n = 2) was achieved by suspending the malacic segment within an oversized and longitudinally opened ring-reinforced polytetrafluoroethylene prosthesis. Multiple plegeted sutures were placed extramucosally to the dysplastic tracheal wall and the dyskinetic pars membranacea, as well as to the polytetrafluoroethylene prosthesis in a radial orientation. Guided by simultaneous video-assisted bronchoscopy, reexpansion of the collapsed segments was achieved by gentle traction on the sutures while tying.

RESULTS

Stenosis-free tracheobronchial reexpansion was achieved in all patients, as seen on repeated bronchoscopies during hospitalization and thereafter. All patients were extubated within 1 to 12 days after the operation. There was one late death, unrelated to the procedure, in a 31-month-old child 20 months after the operation. All other patients are free of stridor and in excellent clinical condition 21 to 54 months (mean, 38 months) thereafter.

CONCLUSIONS

The presented method of bronchoscopically guided external tracheobronchial suspension within a ring-reinforced polytetrafluoroethylene prosthesis immediately relieves severe malacia of the trachea or main bronchi in infants as well as adults without necessitating resection. Midterm preliminary data suggest that growth potential of the affected segment exists within the oversized polytetrafluoroethylene prosthesis.

Successful revascularisation for unstable angina of a patient with asymptomatic bilateral internal carotid occlusion, 70% stenoses of the external carotid arteries, and other circulation disturbances

Nowadays, advanced surgical and anaesthesiological techniques of coronary artery bypass grafting minimize the risk of severe complications in patients with advanced arteriosclerotic cerebrovascular disease. Nevertheless, in case of highly compromised cerebrovascular status, the decision whether to undertake coronary artery bypass grafting or not requires special patient-related consideration. A severe, unstable angina made it necessary to perform coronary bypass grafting in a patient with bilateral internal carotid occlusion, a bilateral mid-stage stenosis of both external carotid arteries, a diminished flow within the right vertebral artery, and a subsequently impaired intracranial blood flow. Intraoperatively, besides the usual hemodynamic measurements, laser-Doppler flow probes were placed on the left and right upper temple to monitor relative changes of the cerebral blood supply. Using an individual perioperative management, the patient experienced a normal postoperative course and was discharged in good condition.

[Premedication of coronary risk patients--results of a survey]

AIM

The perioperative risk in patients undergoing coronary artery bypass grafting (CABG) might be influenced by premedication procedures. This study was undertaken to evaluate present premedication regimens in CABG patients in Germany.

METHODS

Using a detailed written questionnaire, each of the 58 German centres of cardioanaesthesia were asked to complete it.

RESULTS

37 (64%) of all questionnaires were returned and analysed. All centres used orally administered drugs for premedication in the evening before the operation. Flunitrazepam is the most often administered drug (54%), followed by dipotassium clorazepat (8%), and diazepam (8%). Premedication in the morning on the day of surgery is performed orally in 29 centres (78%), of which 18 centres (49%) prefer flunitrazepam and 6 centres (16%) midazolam as first choice. In contrast, 7 centres (19%) used intramuscularly administered regimens. 5 centres (14%) combined intramuscularly opioids with sedatives for that indication. If anaesthesia was induced late in the morning or in the afternoon, respectively, 11 centres (30%) administered additional benzodiazepines early in the morning. 68% of all centres maintained the administration of chronic treatment with ss-blockers until the morning of the operating day. Chronic treatment with nitrates is continued in 65%, treatment with calcium-channel blockers in 62%. Angiotensin converting enzyme inhibitors are continued in 30%, alpha 2-agonists in 27%, other antihypertensive drugs in 19%, and inotropic glycosids in 11%. 31 of 37 centres (84%) discontinued the administration of acetylsalicylic acid 5 or more days prior to surgery, but 68% tolerate individual exceptions from this principle.

CONCLUSIONS

The results of our survey indicate that most of the German cardioanaesthesia centres use oral premedication regimens in patients undergoing coronary revascularisation. Anti-anginal medications, with the exception of anti-platelet agents, were continued until the day of surgery in most of the centres.

[Anesthesiologic management in cardiomyoplasty]

Dynamic cardiomyoplasty is a therapeutic possibility in irreversible cardiac insufficiency. With this operation, the latissimus dorsi muscle is mobilised and drawn into the thorax where it is placed around the heart. Lateral and supine positioning as well as thoracotomy and direct manipulation of the heart are associated with particular risks during surgery. Eight patients with the diagnosis of cardiomyopathy underwent cardiomyoplasty. The patients were classified as NYHA III-IV. Continuous dobutamine infusions were routinely started after induction of anaesthesia. All patients were intubated with single-lumen tubes. After sternotomy, lidocaine was administered. Monitoring included Swan-Ganz catheterisation and invasive blood pressure measurement. With early use of inotropic and vasodilatator agents the cardiac index and peripheral vascular resistance were adequately maintained. Double-lumen intubation seems to be unnecessary during cardiomyoplasty and only increases patient risk. Prophylactic lidocaine infusions are effective in preventing ventricular tachycardia and fibrillation. We conclude that adequate intraoperative management can improve the haemodynamic status of these patients so that cardiomyoplasty may be performed without significant morbidity.

Treatment of dilated cardiomyopathy with dynamic cardiomyoplasty: the Heidelberg experience

BACKGROUND

Data concerning the efficacy of dynamic cardiomyoplasty are still inconsistent, especially in terms of improvement of left ventricular function.

METHODS

Between August 1990 and February 1994, eight isolated cardiomyoplasty procedures were performed in patients with cardiomyopathy (ejection fraction, 0.14 to 0.32; New York Heart Association class III) and contraindications to heart transplantation.

RESULTS

Follow-up was 41.1 +/- 14.1 months. One patient died 2 months and another 3 years after operation. Considerable symptomatic improvement was found in 6 of 7 patients, 3 of whom went back to work. One patient with severe pulmonary hypertension exhibited no improvement. Mean New York Heart Association-class decreased from 3.0 to 1.9 (p < 0.001). Echocardiography showed an increase in fractional shortening and in peak aortic flow velocity in all patients. Left ventricular ejection fraction increased from 0.21 +/- 0.05 to 0.38 +/- 0.16 (n = 7, p < 0.015) at 1 year, to 0.37 +/- 0.18 (n = 6, p < 0.05) at 2 years, and to 0.36 +/- 0.19 (n = 5, not significant) at 3 years. Pulmonary artery pressure tended to decrease over time. No significant change in exercise level or maximal oxygen consumption during treadmill testing was observed.

CONCLUSIONS

Our preliminary results show that patients may exhibit an impressive clinical improvement after cardiomyoplasty, with only moderate changes in objective hemodynamic indices. We do not consider cardiomyoplasty an alternative to heart transplantation, but reserve it for patients with contraindications to heart transplantation.

Dynamic cardiomyoplasty: indication, surgical technique, and results

The efficacy of dynamic cardiomyoplasty is still controversial. To date more than 400 patients have been operated worldwide. In recent years the indication and the surgical technique have become more uniform, which makes results from different centers eligible for comparison. We performed cardiomyoplasty exclusively in patients with contraindications for heart transplantation, such as chronic and recurrent infections or severe, irreversible sequelae of diabetes. Between August 1990 and October 1994, 8 isolated cardiomyoplasty procedures were performed in patients with cardiomyopathy (EF 14-32%, all in NYHA III). One patient died 2 months after surgery. Reported are the results of 7 patients after a mean follow-up of 41.1 +/- 14.1 months. Considerable symptomatic improvement was found in 6 or 7 patients, 3 of whom went back to work. One patient with severe pulmonary hypertension exhibited no improvement. In the others NYHA class improved by at least one. Echocardiography showed an increase in fractional shortening in all patients. LVEF increased from 21.2 +/- 5.2% to 38.1 +/- 15.9% (n = 7, p < 0.015) at 1 year, to 36.6 +/- 17.6% (n = 6, p < 0.05) at two years, and to 36.4 +/- 18.9% (n = 5, NS) at three years. Pulmonary artery pressure tended to decrease at rest over time. Resting lung function showed no change of vital capacity and FEV1. No significant change in exercise level and maximal O2-consumption during treadmill testing was observed. One patient died 34 months after the operation from sudden death. Our preliminary results show that patients after cardiomyoplasty may exhibit an impressive clinical improvement with less striking changes of objective hemodynamic parameters. This data is in agreement with the results of all other investigators. Some possible mechanisms of action are discussed and a risk profile suggested. According to the current state of experience with cardiomyoplasty, we do not consider this method an alternative to heart transplantation, but reserve it for patients with contraindications for heart transplantation.

Continuous versus intermittent cardiac output measurement in cardiac surgical patients undergoing hypothermic cardiopulmonary bypass

OBJECTIVE

Continuous thermodilution cardiac output (CCO) measurement was clinically evaluated in patients who underwent coronary revascularization using hypothermic low-flow, low-pressure cardiopulmonary bypass (CPB).

DESIGN

Prospective study.

SETTING

University hospital setting.

PARTICIPANTS

30 cardiac surgical patients.

INTERVENTIONS

CCO was correlated to standard bolus thermodilution cardiac output (ICO) obtained at end-expiration.

MEASUREMENTS AND MAIN RESULTS

Measurements were taken at selected time points (n = 18) before anesthesia induction, before CPB, and 5 minutes to 12 hours after CPB. A total of 540 data pairs were thus obtained. ICO ranged from 1.9 to 9.9 L/min, CCO from 1.5 to 9.9 L/min. Correlation between ICO and CCO was highly significant (r = 0.872; p < 0.01), accompanied by an excellent accuracy (bias -0.0213 L) and precision (0.59 L) before CPB and more than 45 minutes after CPB. However, during the first 45 minutes after CPB, there was no correlation (r = 0.273) between ICO and CCO, and ICO tended to be relatively high, whereas CCO measurements showed relatively low values. During the first 45 minutes after hypothermic CPB, but not during the ensuing time period, central blood temperature decreased, which may be interpreted as a lack of thermal equilibration between central and peripheral compartments. It is hypothesized that thermal instability in combination with increased respiratory variations in pulmonary artery blood temperature caused inhomogenous rewarming of different body sites and might be the main reason for the lack of correlation between ICO and CCO.

CONCLUSIONS

Despite an excellent correlation, accuracy, and precision between CCO and ICO before CPB and more than 45 minutes after hypothermic CPB, a lack of correlation in the early phase after CPB has been found. Further investigation is needed to elucidate the underlying cause of these findings and to clarify whether ICO or CCO or both fail to represent the real cardiac output up to 45 minutes after weaning from hypothermic CPB.

Safety and effectiveness of an oral premedication regimen before cardiac surgery

Thirty-five adult cardiac surgical patients received 20 mg dipotassium clorazepate orally the evening before surgery and 2 mg flunitrazepam 60 min before induction of anaesthesia. If anaesthesia was to be induced after 08.30 hours patients received an additional 20 mg dipotassium clorazepate at 06.15 hours. The following measurements were made: peripheral arterial oxygen saturation (Spo2) breathing room air; anxiety by visual analogue scale; degree of sedation; and haemodynamic variables. Mean (Spo2) was 95.9% (SD 1.8%) on the day before surgery and 95.4% (SD 1.5%) on arrival at the operating room. When the operation started after 08.30 hours, mean (Spo2) at 09.00 hours was 96.0% (SD 1.4%). There were no detected episodes of hypoxaemia after premedication. Mean anxiety score decreased significantly from 3.9 (SD 2.6) on the day before surgery to 3.3 (SD 2.1) on arrival at the operating room (patients' score; P < 0.002) and from 4.6 (SD 2.4) to 3.3 (SD 2.0) (anaesthesiologists' score; P < 0.001). Nearly all patients were considered well sedated, which was reflected by normal haemodynamic variables on arrival at the operating room. The combination of clorazepate and flunitrazepam is effective oral premedication for adult cardiac surgery, causing no obvious desaturation even when supplemental oxygen is not given.

[Successful use of a heparinoid (danaparoid sodium) for heparin-induced thrombocytopenia type II in aortic valve reoperation]

The 29-year-old, heroin-addicted patient received an aortic valve prosthesis (SJM) 10 years ago because of aortic valve stenosis III. One year after surgical treatment he refused to take Phenprocoumon and thus received no anticoagulation for 9 years. The patient was hospitalized due to cardial decompensation and thrombosis of the aortic valve prosthesis was diagnosed. Under heparinization, he developed heparin-induced thrombocytopenia type II, which disappeared after changing the medication to Danaparoid-Sodium. In order to avoid any further heparin exposure, we also carried out the surgical replacement of the aortic valve prosthesis under anticoagulation with Danaparoid-Sodium.

[Medical therapy for coronary heart disease. Perioperative relevance]

OBJECTIVE

The aim of our review is to summarize relevant data on the perioperative use of anti-ischaemic drugs in patients at risk for or with proven coronary heart disease.

DATA SOURCES

The accessible medical literature according to current electronic information sources was explored.

RESULTS

One in every eight general anaesthetics is administered to a patient at risk for or with proven coronary heart disease. Of these patients, it is estimated that 20%-40% have perioperative myocardial ischaemia (PMI), the majority being non-symptomatic. This figure correlates with the occurrence of postoperative cardiac complications and myocardial infarction. The anaesthetist therefore has an important role to play in reducing the rate of perioperative cardiac sequelae. This can be achieved with good control of haemodynamic stability and the timely and appropriate use of antiischaemic drugs. Nitrocompounds (nitrates, molsidomine) serve as the gold standard in current angina pectoris treatment. Acting as coronary and systemic vasodilators, they effect an immediate reduction in preload and have been shown to be the drugs of first choice for intraoperative myocardial ischaemia. Beta-blockers reduce the rate of PMI to a greater extent than nitrates. They are also effective in myocardial ischaemia not accompanied by an increased heart rate. Single pre-operative administration of beta-blockers has also been shown to be beneficial in reducing the incidence of perioperative tachycardia, hypertension, and PMI. Consequently, such one-time medication can be considered for previously untreated high-risk patients presenting for surgery. The continuation of oral calcium channel blockers to the morning of surgery also reduces the rate of PMI and myocardial infarction in coronary-bypass patients, and combination with beta-blockers enhances this effect. Intra-operative diltiazem infusions are similarly advantageous in this patient group. In addition to nitrates, calcium antagonists are the drug of choice for coronary vasospasm. Drugs inhibiting platelet aggregation have a particular role in patients with coronary heart disease, however, they also cause increased perioperative bleeding. Consequently, it is recommended that these medications be discontinued 5-10 days prior to major surgery, with the exception of high-risk patients. Pilot studies using alpha 2-agonists have shown reduced anaesthetic requirements and a reduction in PMI. The perioperative relevance of these drugs is currently being investigated.

CONCLUSIONS

Beta-blockers, calcium channel blockers, nitrates, and possibly alpha 2-agonists lead to reduced rates of PMI and other cardiac complications in risk patients. Current anti-anginal medications, with the exception of anti-platelet agents, should be maintained to the day of surgery and continued as soon as possible thereafter. All of these drugs except anti-platelet agents may also be used intra-operatively, however, possible interactions with anaesthetic agents should be carefully considered.

Evoked potential monitoring during repeatedly induced ventricular fibrillation for internal defibrillator implantation

Repeated induction of ventricular fibrillation (VF) with circulatory compromise during implantable cardioverter defibrillator (ICD) testing may cause cerebral injury. To test this hypothesis, somatosensory evoked potentials (SEP), a more sensitive marker of injury, were recorded in patients (N = 10) undergoing ICD implantation. SEP were recorded before induction of anesthesia, after induction of anesthesia, before and at several times following induction of VF. Possible modifying factors of the SEP measurements such as anesthetic application, blood pressure, body temperature, and hematocrit remained constant throughout the operations. Central conduction time was unaffected by ICD defibrillation testing. Amplitude of SEP primary complexes was transiently reduced at 34.9% (P < 0.01) by defibrillation testing, but returned to control within 10 minutes after testing. It is concluded that while ICD defibrillation testing may produce transient changes in SEP, there is no evidence of residual cerebral injury.

Effects of thiopentone/suxamethonium on intraocular pressure after pretreatment with alfentanil

The effects of pretreatment with alfentanil on intraocular pressure (IOP) were investigated in 40 patients undergoing ophthalmic surgery. Patients were randomly allocated to two study groups. Group 1 patients (n = 20) received alfentanil 15 micrograms.kg-1, vecuronium 0.01 mg.kg-1, thiopentone 3-4 mg.kg-1, and suxamethonium 1 mg.kg-1 for anaesthetic induction, whereas patients in group 2 (n = 20) received vecuronium 0.01 mg.kg-1, thiopentone 3-4 mg.kg-1, and suxamethonium 1 mg.kg-1. A total of seven measurements of intraocular pressure were taken in each patient, starting before premedication and ending after extubation of the trachea. In group 2 patients, there was an increase in IOP after endotracheal intubation. In group 1 patients, a decrease in IOP occurred which was related to the decrease in arterial blood pressure. We conclude that alfentanil pretreatment can prevent the increase in IOP following suxamethonium administration.

[Suture fixation of a Swan Ganz catheter to the left brachiocephalic vein during re-thoracotomy]

This case report describes the intraoperative fixation of a Swan-Ganz catheter at the left brachiocephalic vein by a suture during rethoracotomy in a cardiac surgical patient. In case of a rethoracotomy by median sternotomy the right-sided veins should be preferred for the insertion of a Swan-Ganz-catheter. Furthermore the free mobility of the catheter should be controlled before closure of the thorax.

Adverse haemodynamic effects of high-dose aprotinin in a paediatric cardiac surgical patient

High-dose aprotinin for reduction of intra- and postoperative blood loss was associated with profound hypotension and flushing in a 3.5-year-old child who underwent cardiac surgery. Treatment with noradrenaline and intravenous fluid was required. Cardiovascular stability was restored after 10 minutes.

Tussive effect of a fentanyl bolus administered through a central venous catheter

One hundred and ten male patients scheduled for coronary artery bypass grafting were allocated randomly into one of three groups. Patients in group A received fentanyl 7 micrograms/kg via a central venous catheter, those in group B were given fentanyl 7 micrograms/kg through a peripheral venous cannula, and patients in group C received sterile water via a central venous catheter. In group A, 45.9% of patients coughed after injection of fentanyl; the mean onset time from the end of fentanyl administration to the beginning of coughing was 10.6 seconds. Only one patient in group B and no patient in the control group exhibited a cough response (p less than 0.0001). We hypothesise that fentanyl can evoke the pulmonary chemoreflex.