An anaesthetic protocol in the young domestic pig allowing neuromuscular blockade for studies of cardiac function following cardioplegic arrest and cardiopulmonary bypass.

BACKGROUND: Neuromuscular blockade should, for ethical reasons, not be allowed in animal experiments unless the use is strongly motivated. Beforehand, the anaesthetic protocol must be documented without muscle relaxation in the species studied. Documentation is difficult to obtain from the scientific literature. When focusing on cardiac function over time, in particular, the ideal anaesthetic protocol should cause no or minor alterations in cardiac variables. METHODS: We intended to document an anaesthetic protocol involving ventilation with N(2)O combined with loading doses and continuous infusions of pentobarbital, fentanyl and midazolam in seven pigs by applying potentially painful stimuli every 15 min for 7 h. Subsequently, left ventricular global and regional function was studied with conductance catheter and strain rate imaging by echocardiography in eight pigs with pancuronium included. RESULTS: Pigs without pancuronium were completely immobilized and unresponsive to potentially painful stimuli and sternotomy, with no accumulation or degradation of anaesthetic agents. With pancuronium included, left ventricular preload gradually decreased together with reduction of cardiac index from 3.52 +/- 0.14 at 2 h to 2.84 +/- 0.11 L min(-1). m(-2) (+/-SEM) after 7 h of observation. Preload recruitable stroke work decreased after 7 h, whereas peak systolic strain in the anterior left ventricular wall and load-independent indices of diastolic function were not significantly altered. CONCLUSION: In specific experimental protocols, the anaesthetic protocol described could allow the use of muscular paralysis in young domestic pigs, for instance when involving hypothermic cardiopulmonary bypass, cardioplegic arrest and reperfusion.

Immediate control of life-threatening digoxin intoxication in a child by use of digoxin-specific antibody fragments (Fab).

Digoxin-immune antibody fragments (Fab) for treatment of digitalis intoxication was introduced in 1976. Many reports have been published concerning this therapy for children, but few have focused on its immediate reversal of cardiac as well as extracardiac life-threatening manifestations of digoxin toxicity. We present a case of life-threatening digitalis intoxication in a child with postoperative renal insufficiency, after a Sennings procedure for transposition of the great arteries. Digoxin administration according to the nationally recommended dosage and intervals unexpectedly resulted in serum levels in the toxic range. Severe cardiac arrhythmias, haemodynamic instability and a rapid-increasing serum potassium level resulted. This report demonstrates how administration of Fab according to the manufacturer's dosage recommendation reversed the tachyarrhythmia immediately and re-established a normal level of serum potassium within minutes.

Rewarming from accidental hypothermia by extracorporeal circulation. A retrospective study.

OBJECTIVE: Twenty-six patients with accidental hypothermia combined with circulatory arrest or severe circulatory failure were rewarmed to normothermia by use of extracorporeal circulation (ECC). The aim of the present study was to evaluate our results. PATIENTS AND METHODS: The treatment of six female and 20 male patients (median age: 26.7 years; range 1.9--76.3 years) rewarmed in the period 1987--2000 was evaluated retrospectively. Hypothermia was related to immersion/submersion in cold water (n=17), avalanche (n=1) or prolonged exposure to cold surroundings (n=8). Prior to admission, the trachea was intubated and cardiopulmonary resuscitation (CPR) initiated in all patients with cardiorespiratory arrest (n=22), whereas in those with respiration/circulation (n=4) only oxygen therapy via a face mask was given. RESULTS: Nineteen of the 26 patients were weaned off ECC whereas seven died because of refractory respiratory and/or cardiac failure. Eight of the 19 successfully weaned patients were discharged from hospital after a median of 10 days. One patient died 3 days after circulatory arrest (complete atrioventricular block) resulting in severe cerebral injury. The remaining ten patients died following 1--2 days due to severe hypoxic brain injury (n=5), cerebral bleeding (n=1) or irreversible cardiopulmonary insufficiency (n=4). Based on the reports from the site of accident, two groups of patients were identified: the asphyxia group (n=15) (submersions (n=14); avalanche accident (n=1)) and the non-asphyxia group (n=11) (patients immersed or exposed to cold environment). Seven intact survivors discharged from hospital belonged to the non-asphyxia group whereas one with a severe neurological deficit was identified within the asphyxia group. CONCLUSION: Patients with non-asphyxiated deep accidental hypothermia have a reasonable prognosis and should be rewarmed before further therapeutic decisions are made. In contrast, drowned patients with secondary hypothermia have a very poor prognosis. The treatment protocol under such conditions should be the subject for further discussion.

Velocity distribution in the ascending aorta in pigs during chronotropic and inotropic stimulation.

The influence of heart rate, stroke volume and myocardial contractility on temporal and spatial velocity distribution in the ascending aorta was investigated in 10 pigs. A pulsed Doppler ultrasound technique with intraluminal probe and a single crystal connected to a position-sensitive device was used to measure blood velocity. After baseline registration, the heart rate was increased in two discrete steps of 20 beats/min by right atrial pacing. Isoproterenol infusion was given to increase contractility. Finally, without isoproterenol, the heart rate was again raised to the values found during inotropic stimulation. The first three measuring situations did not differ haemodynamically, apart from increased heart rate and reduced stroke volume. Increased heart rates were not associated with significant change in the parameters for skewness of velocity distribution (peak systolic slope and ratio, maximum skewness slope and ratio). During inotropic stimulation the peak left ventricular dP/dt, aortic systolic pressure, cardiac output and stroke volume were greater than at comparable paced heart rate, and the peak systolic slope of velocity distribution was significantly increased. Velocity distribution in the ascending aorta thus was not altered by increased heart rate alone, whereas skewness of distribution was enhanced by increased inotropic drive of the myocardium and the concomitant central and peripheral vascular changes.

[Patients surgically treated for aortic coarctation]. / Pasienter operert for koarktasjon av aorta.

The aim of this study was to evaluate the results of surgical treatment of coarctation of the aorta. All patient files on patients operated at Haukeland Hospital, Bergen, Norway, in the period 1975-95 (n = 102) were surveyed. We sent a questionnaire to all patients alive in 1996 (n = 84), and 82 (98%) responded. Six patients (6%) died within 30 days of surgery, and 12 (12%) died later. These mortality numbers were smaller among patients operated in the period 1988-95. Among patients with associated heart defects (n = 28) the numbers were 14% and 25%, respectively. Four patients required reoperation and three patients balloon dilatation. Six of these patients were operated in the period 1975-87. Among the 82 patients that responded to the questionnaire, clinical follow-up by a cardiologist had been discontinued in 35 cases. 31 patients (38%) were not satisfied with the follow-up. Many patients reported muscle fatigue in the legs (30%), reduced exercise performance (29%), headache (26%), general fatigue (22%), and leg pain (17%). 38% did not report any symptoms. Our results are in accordance with previously reported studies, and the mortality numbers were reduced in the second period. The number of recurrences was also reduced in this period. The symptoms reported by many patients may be caused by recoarctation or an abnormal blood pressure. This group of patients should, therefore, be monitored systematically for abnormal blood pressure, recoarctation and aortic valve disease.

Cardiac arrest due to massive pulmonary embolism following caesarean section. Successful resuscitation and pulmonary embolectomy.

A woman developed pulmonary embolism with cardiac arrest after caesarean section. Cardiopulmonary resuscitation was performed for 45 min during which echocardiography showed right ventricular dilatation. After stabilization, but still in a critical condition, the patient was transferred by airambulance to a hospital with facilities for extracorporeal circulation. A massive embolus was removed. Some hours after extubation the patient developed respiratory insufficiency and hypovolaemia. Re-intubation was followed by severe hypotension requiring external cardiac compression for about 15 min. An emergency explorative laparotomy revealed a ruptured liver with a subcapsular haematoma. A critical illness polyneuropathy made prolonged ventilatory support necessary. She recovered without cerebral sequelae.

Three-dimensional cross-sectional velocity distribution in the ascending aorta in cardiac patients.

Knowledge of the distribution of velocities across the ascending aorta is important for measurements of cardiac output; for understanding the function of normal and diseased valves and for the evaluation of prosthetic valves. The aim of this study was to investigate, in detail, the spatial distribution of axial velocities in the human ascending aorta, covering a nearly complete cross-section of the lumen in a time continuous modus. During open-heart surgery, blood velocities in the ascending aorta were mapped in 10 patients. All patients had aortic valves with no significant clinical evidence of disease. Pulsed Doppler ultrasound technique was used to measure blood velocity using an intraluminal probe with a 1 mm, 10 MHz crystal connected to a position-sensitive device. The distribution of blood velocity in the aorta 6-8 cm above the valve was characterized by a skewed and irregular peak systolic flow, with maximum velocity posteriorly. There was a positive correlation (r=0.854, P<0.002) between the maximum skewness slope and the stroke volume. Significant retrograde flow was recorded in all patients in the left posterior part of aorta in late systole and early diastole. The rotation of the point of maximal velocity was anticlockwise in six patients, clockwise in three and alternating in one. The present study shows that there is a considerable individual variation in the velocity distribution in the ascending aorta, with no plane symmetric features, and that large sampling volumes are required for reliable estimates of mean velocity.

Haemodynamic effects of high-dose vecuronium compared with pancuronium in beta-blocked patients with coronary artery disease during fentanyl-diazepam-nitrous oxide anaesthesia.

BACKGROUND: Different combinations of neuromuscular blockers and opioids have been used in patients with angina pectoris to provide cardiovascular stability and reduce risk of myocardial ischaemia during anaesthesia. METHODS: We have compared the haemodynamic effects of high-dose vecuronium (0.3 mg kg-1) with those of a standard dose of pancuronium (0.1 mg kg-1) in patients scheduled for coronary artery bypass grafting during fentanyl-diazepam-nitrous oxide anaesthesia. All patients were receiving beta-adrenergic blocking agents. The given doses of vecuronium and pancuronium are equieffective with respect to duration of neuromuscular blockade. RESULTS: During a 25-min experimental period following the administration of the randomly selected drug, no significant changes in the haemodynamic parameters were observed in the vecuronium group. The administration of pancuronium, however, resulted in a significant mean increase in heart rate (20%), rate-pressure product (23%) and cardiac index (21%). Following endotracheal intubation in the pancuronium group, we observed an additional significant increase in mean arterial pressure and rate-pressure product. CONCLUSION: High-dose administration of vecuronium has minimal haemodynamic effects and may thus offer a better alternative than pancuronium for long-lasting neuromuscular blockade in patients with coronary artery disease during fentanyl-diazepam-nitrous oxide anaesthesia.

New temporary atrial and ventricular pacing leads for patients after cardiac operations.

We have studied two new temporary pacing leads (Medtronic 6491 and 6492) intended for pacing after cardiac operations. The conductor has stainless steel strands coated with polyethylene connected to a 4' mm2 surface area, stainless steel, smooth, tapered electrode. A soft 4-0 coiled polypropylene fiber served as as fixation mechanism in the heart. The study included 15 children (aged 3 months to 7 years, body weight 4.4 to 20 kg) with a variety of congenital heart defects and 15 adults (aged 45 to 78 years) with coronary artery disease (n = 13) and aortic valve disease (n = 2). A pair of leads each was placed in a bipolar fashion in the right atrial wall and nonsystemic ventricle in the children (median implant duration 12 days) and in the right atrial wall only in the adults (median implant duration 9 days). The atrial current threshold values in children increased from 0.61 +/- 0.34 mA immediately after implant to 2.08 +/- 1.86 mA at explant (p < 0.002). In the adults the threshold values increased from 0.95 +/- 1.44 mA immediately after implant to 2.76 +/- 2.76 mA at explant (p < 0.002). In the ventricle the threshold values increased from 0.38 +/- 0.13 mA immediately after implant to 2.22 +/- 1.63 mA at explant (p < 0.002). Tissue resistance immediately after implant measured 809 +/- 182 omega at explant (children, p = not significant). Corresponding values in adults were 778 +/- 190 omega and 599 +/- 91 omega (p < 0.004). In the ventricle resistances changed from 1019 +/- 143 omega to 876 +/- 137 omega (p < 0.05). P wave amplitudes measured 1.8 +/- 1.5 mV immediately after implant and decreased to 1.6 +/- 1.2 mV at explant (p = not significant, children) and 2.0 +/- 1.3 mV to 1.8 mV (p = not significant, adults). R wave amplitude were 13.1 +/- 3.0 mV immediately after implant and fell to 8.7 +/- 4.5 mV at explant (p < 0.005). Thus, threshold values, tissue resistances, and electrogram and pliable amplitudes assured a safe pacemaker function. The small diameter and pliable texture of these leads provided a smooth surgical handling. They were found particularly suitable in children.

[Adult patients with atrial septal defect]. / Voksne pasienter med atrieseptumdefekt.

Our material included patients older than 30 years who were diagnosed as having atrial septal defect during the period 1980-1993. A questionnaire was used during follow-up. 39 of a total of 42 patients were operated on. The mean follow-up time was 5.5 years. There was no operative mortality. Five patients had died by the time of follow-up. The three patients who had not been operated on had all died. The available literature gives no conclusive answer to the question of whether all patients with an atrial septal defect should be offered surgery or not.

Intraluminal recording of cross-sectional blood velocity distribution of human ascending aorta by ultrasound Doppler technique.

A pulsed Doppler ultrasound technique was used for mapping two-dimensional blood velocity profiles in the human ascending aorta during open-heart surgery. An electronic position-sensitive device was constructed and linked to an intraluminal 10 MHz Doppler ultrasound probe. From a plane perpendicular to the central direction of blood flow, velocity mapping was performed covering the entire cross-section of the ascending aorta 6-7 cm above the valve. This method is based on a sequential sampling of velocity from continuously changing locations during a stable haemodynamic period; typically velocity points are recorded from 150-300 beats. Further processing transformed data to suit a previously developed velocity distribution model for normal blood flow in the human ascending aorta, based on multi-regression analyses. In this model, the time series of data from consecutive beats were computed into an average two-dimensional profile described through one cardiac cycle. This method allows high spatial resolution (1.5 mm), in addition to the high-frequency response (200 Hz) of the modified ultrasound Doppler meter. Together with the advantage of velocity directionality and minimal time interventions, this makes the method well suited for studies on normal flow conditions as well as flow velocity distribution distal to different heart valve prostheses.

Comparison of transit-time and Doppler ultrasound methods for measurement of flow in aortocoronary bypass grafts during cardiac surgery.

To evaluate the accuracy of flow measurements in aortocoronary bypass grafts with the ultrasound transit-time method, an in vitro and in vivo comparison was carried out. The in vitro comparison with evaluation against both true flow and the ultrasound Doppler method, was carried out with a fresh saphenous vein mounted in a pulsatile flow rig. The two flow probes were placed on the graft 4-5 cm apart to avoid acoustic interference, and blood was pumped through the system at different flow rates. The comparison between the methods showed excellent agreement with a linear correlation coefficient of 0.996, and a mean error of -2.9 ml/min with limits of agreement +/- 13.1 ml/min (+/- 2 SD = 95% of measured differences between these limits). However, against true flow, both methods overestimated flow slightly with mean error 4.4 and 7.3 ml/min for the transit-time and Doppler, respectively. Both methods showed excellent correlation with true flow (correlation coefficient 0.998 for the transit-time and 0.997 for the Doppler method). The in vivo accuracy was evaluated by comparison of the two methods in 9 patients. The two probes were placed on the same saphenous vein grafts 4-5 cm apart, and a total of 34 measurements in 17 grafts were carried out including measurements at baseline and after papaverine injection. The correlation coefficient was 0.990 and linear regression analysis gave the equation: Transit-time flow = 1.00 x Doppler flow + 1.3. In terms of flow, the mean error was 1.5 ml with limits of agreement +/- 17.2 ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic status in repaired tetralogy of Fallot assessed by Doppler echocardiography and cardiac catheterization. Comparisons with healthy subjects and elucidation of factors associated with cardiorespiratory function.

Thirty-four patients were studied after corrective surgery for tetralogy of Fallot (mean follow-up 10 years) and compared with healthy matched controls. All underwent Doppler echocardiography, spirometry and treadmill exercise test. Post-operative cardiac catheterization had been performed on 26 (76%) of the patients and showed poor hemodynamic results in four (15%). Significant correlations of pressure gradients obtained from catheterization and estimated by Doppler echocardiography were right ventricular to right atrial (r = 0.77), pulmonary outflow (r = 0.75), pure valvular pulmonary outflow (r = 0.94) and diastolic pulmonary pressure gradients (r = 0.53). Pulmonary outflow gradients and right ventricular to right atrial pressure gradients estimated from tricuspid regurgitation jets were significantly increased in the patients. Diastolic pulmonary artery pressure, vital capacity and ventilatory anaerobic threshold were independent factors of maximal oxygen consumption. It is suggested that Doppler-derived diastolic pulmonary artery pressure, lung function studies and exercise testing with assessment of the ventilatory anaerobic threshold should be included in follow-up after repair of Fallot's tetralogy.

Estimation of total body fluid shifts between plasma and interstitium in man during extracorporeal circulation.

Fluid transport between plasma and interstitium during extracorporeal circulation was studied in seven patients undergoing aortocoronary bypass grafting. The absolute shifts in plasma volume during hypothermia were determined as the difference between input and loss of fluid and the changes in blood volume. The change in haemoglobin concentration due to acute haemodilution when starting extracorporeal circulation was used to calculate the absolute blood and plasma volume. The Starling equation for exchange across the capillary wall was used to describe fluid shifts. The total fluid filtered during the 60- to 90-min period of extracorporeal circulation averaged 34.1 +/- 11.1 (s.d.) ml/min. The total body filtration coefficient from the Starling relationship averaged 0.046 +/- 0.012 ml/kg.mmHg.min (0.354 +/- 0.092 ml/kg.kPa.min). Haemodilution, reducing colloid osmotic pressure in plasma (COPP) by approximately 10 mmHg (1.3 kPa) will result in a loss of plasma fluid of around 2 1 per hour. When corrected for lower fluid viscosity due to hypothermia during extracorporeal circulation, CFC would be about 40% higher, and a filtered volume of nearly 3 1 in a normothermic 70-kg person would be expected. Crystalloid haemodilution for shorter periods of time does not produce excessive oedema and thus may be well tolerated.

Velocity distribution model for normal blood flow in the human ascending aorta.

During the study of velocities in the human ascending aorta it became necessary to establish a method for two-dimensional velocity profiles from discrete velocity data obtained from different heartbeats and with different techniques. A descriptive geometrical model was therefore developed and expanded to 16 elements each containing 16 constants by a serial optimising technique using a least-squares method. Published data from two different studies on velocity distribution in the ascending aorta comprising six subjects with normal aortic valves were used. Three-dimensional graphic displays of velocity profile at different time intervals of the heart cycle clearly show common features of distribution of velocity at a point 6 cm above the aortic valve. There was a pronounced skewness with clockwise rotation of the skewness direction during systole, reversed flow directed towards the left coronary sinus of Valsalva in late systole and early diastole concomitant with secondary flow augmentation along the opposite wall of the aorta. Consistent plane-symmetric features during the heart cycle could not be demonstrated.

[Prevention of scars. A controlled long-term study of the effect of hydrocolloid occlusive bandages after thoracic surgery in children]. / Profylaktisk arrbehandling. En kontrollert langtidsstudie av effekten av hydrokolloid okklusiv bandasje etter thoraxkirurgi hos barn.

We examined the development of hypertrophic scarring in 38 children undergoing thoracic surgery. The patients were observed for average 14 months. A treatment group receiving hydrocolloid occlusive bandage (DuoDERM ConvaTec, Squibb) was compared with a control group. Although the difference between the groups did not reach statistical significance there was a clear tendency towards better prevention of hypertrophic scarring in the group treated with hydrocolloid occlusive bandage.

Instantaneous cross-sectional flow velocity profiles: a comparative study of two ultrasound Doppler methods applied to an in vitro pulsatile flow model.

Two methods based on different techniques for construction of cross-sectional flow velocity profiles from Doppler ultrasound signals were compared: an intraluminal method using pulsed-wave Doppler echocardiography and an extraluminal method using two-dimensional (color) Doppler ultrasound. The methods were applied to an in vitro pulsatile flow model. With the intraluminal method, pulsed Doppler recordings obtained throughout several flow pulses at different positions across a tube were digitized, and cross-sectional flow velocity profiles were obtained by matching the onset of flow velocity at the various positions. With the extraluminal method, cross-sectional flow velocity profiles were obtained by time interpolation between the digital flow velocity data obtained from several flow velocity maps. The first flow velocity map was recorded at onset of flow and the following maps were incrementally delayed with 20 msec from one flow pulse to the next. The time lag caused by the time needed to update each of the flow velocity maps was compensated for by time interpolation between the sequentially recorded flow velocity maps. The cross-sectional flow velocity profiles obtained with the two methods were compared at identical positions within the tube model at equal flow settings and throughout the pulsatile flow periods. At three different flow settings with peak flow velocity of 0.3, 0.5, and 0.7 m/sec, the difference (mean +/- SD) between the obtained velocities were 0.01 +/- 0.04, -0.01 +/- 0.05, and -0.03 +/- 0.07 m/sec, respectively. The findings suggest that cross-sectional flow velocity profiles from pulsatile flow velocity recordings can be obtained equally well with both methods.

Simultaneous measurement of velocity, diameter, flow and pressure in the ascending aorta of cats. Evaluation of an extractable Doppler ultrasound probe for continuous monitoring of aortic blood flow.

To evaluate an extractable Doppler ultrasound probe designed for monitoring postoperative aortic flow in infants, simultaneous measurements of velocity, diameter, electromagnetic flow estimates, and pressure in the ascending aorta were recorded in cats. Doppler flow calculators were designed to provide flow estimates based on preset constant or measured instantaneous aortic diameter. Doppler sample volume was extended to about 1.2 X 1.6 X 4.0 mm. By pharmacological interventions, a wide range of flow rates and pressures were obtained, some of which were outside physiological values. The prototype probe described here was well suited for implantation in aortas with outer diameter 8-12 mm. Correlation coefficients between Doppler and electromagnetic estimated flow for 140 samples were 0.908 and 0.959 for constant and instantaneous diameter, respectively. Mean difference between the two methods was calculated, as well as the 95% confidence limits (2SD) of the differences. Limits of agreement, in stable haemodynamic situations without drugs, were -20.0 and 22.4% of mean average flow for constant diameter Doppler flow estimates, and -14.5 and 15.1% of electromagnetic flow values for instantaneous diameter estimates. These limits increased when all samples were taken into account, but the limits for instantaneous diameter estimates were reduced from -33.1 and 32.4 to -23.9 and 19.3% after removal of data obtained during isoprenaline infusion, which introduced extreme high flow/low pressure situations. This Doppler method seems well suited for postoperative monitoring of aortic flow in infants. Errors observed in larger aortas with an asymmetric flow profile do not seem to be present in smaller vessels within normal values of flow and pressure.(ABSTRACT TRUNCATED AT 250 WORDS)