Large bolus dose vs. continuous infusion of cisatracurium during hypothermic cardiopulmonary bypass surgery

BACKGROUND AND OBJECTIVE

We investigated whether a high bolus dose of cisatracurium (8x ED95) given at induction can provide muscle relaxation for the major part of a cardiac procedure with hypothermic cardiopulmonary bypass, avoid important postoperative residual curarization and cause no waste of product.

METHODS

Twenty patients were randomly assigned either to Group 1 (n = 10) or Group 2 (n = 10). Those in Group 1 were given cisatracurium in a high bolus dose (0.4 mg kg(-1)). Those in Group 2 received cisatracurium 0.1 mg kg(-1) at induction followed after 30 min by a continuous infusion of cisatracurium. As an escape medication in case of patient movement, a bolus dose of cisatracurium 0.03 mg kg(-1) was given.

RESULTS

In Group 1 (large cisatracurium bolus dose), the clinical duration of effect (until T1/T0 = 25%) was 110 min. Six of 10 patients in Group 1 required additional boluses of cisatracurium intraoperatively. Four of these six had received an additional bolus near the end of surgery and had a train-of-four (TOF) ratio = 0 at the end. The other four patients in Group 1 had a final TOF ratio >0.9. In Group 2 (continuous cisatracurium infusion), only two patients had a TOF ratio >0.9 at the end of surgery, no patient moved and none received additional boluses. The total amount of cisatracurium used in the bolus and infusion Groups was 34.5 +/- 7.8 and 21.3 +/- 5.7 mg, respectively (P = 0.0004).

CONCLUSIONS

For continued neuromuscular block during hypothermic cardiac surgery, a high bolus dose of cisatracurium appears to be safe, although it is not an alternative to a continuous infusion, as its neuromuscular blockade does not cover the intraoperative period and a high incidence of movements occurs. In the patients who received a high bolus dose of cisatracurium, postoperative residual curarization appeared after additional boluses had been given. The consumption of cisatracurium by high bolus was significantly greater than with continuous infusion.

Superior vena cava syndrome caused by a pseudoaneurysm of the ascending aorta

Pseudoaneurysm of the ascending aorta is a well known complication after aortic root surgery. A case of a large pseudoaneurysm is reported, seen as a superior vena cava syndrome, a very rare clinical presentation. Perioperative transoesophageal echocardiography showed the presence of a large pseudoaneurysm starting from the left coronary ostium implantation.

Implications of the use of neuromuscular transmission monitoring on immediate postoperative extubation in off-pump coronary artery bypass surgery

BACKGROUND AND OBJECTIVE

When continuous infusions of neuromuscular blocking drugs are administered during lengthy interventions and no routine antagonism of their effects is applied, there is a dramatic incidence of residual curarization. We have examined whether the use of neuromuscular transmission monitoring results in differences in the incidence of postoperative residual curarization, the use of antagonist agents, and the endotracheal extubation rate and outcome after continuous infusion of rocuronium in patients undergoing off-pump coronary artery bypass surgery.

METHODS

Twenty patients were assigned to group 1 (n = 10, non-blinded neuromuscular transmission monitoring) or group 2 (n = 10, blinded neuromuscular transmission monitoring). In group 1, patients were given rocuronium at an infusion rate of 6 microg kg(-1) min(-1). The rate was manually adjusted in order to maintain T1/T0 at 10%. In group 2, a rocuronium infusion was started 30 min after induction of anaesthesia, at a rate of 6 microg kg(-1) min(-1); this rate was left unchanged during surgery. The rocuronium infusion was discontinued on completion of all vascular anastomoses; propofol was stopped at the beginning of closure of the subcutis and pirinitramide (piritramide) 15 mg was administered intravenously. Remifentanil was discontinued at the beginning of skin closure and neostigmine (50 microg kg(-1)) administered at the end of surgery when the train-of-four ratio was < 0.9 in group 1, and routinely in group 2. A 20 min test period for spontaneous ventilation was allowed once surgery had been accomplished. When the train-of-four ratio was > or = 0.9 (group 1), patients were extubated if also breathing spontaneously, fully awake and able to follow commands. When they met the clinical criteria for normal neuromuscular function after induced blockade, patients in group 2 were extubated when fully awake and able to follow commands.

RESULTS

In group 1, the rate of rocuronium infusion required to keep T1/T0 at 10% was 5 +/- 1.9 microg kg(-1) min(-1); this was not significantly different from the fixed rate in group 2 (P = 0.15). One patient in group 2 was excluded. Eight out of 10 and eight out of nine patients in groups 1 and 2, respectively, reached the extubation criteria. Three out of eight, and five out of eight, patients from groups 1 and 2, respectively, were extubated in the operating room. At that time of endotracheal extubation, all three patients from group 1, but only four of the five patients from group 2 had a train-of-four ratio > or = 0.9. In group 2, one patient was reintubated in the intensive care unit. The incidence of pharmacological reversal was high in group 1.

CONCLUSIONS

Although we found no additional benefit of using neuromuscular transmission monitoring, it seems an absolute necessity for safety reasons. Pharmacological antagonism was mandatory. However, in our opinion, it is not wise routinely to perform immediate postoperative extubation in off-pump coronary artery bypass surgery.

Air-oxygen mixtures in circle systems

STUDY OBJECTIVE

To determine the effect of different air-O(2) mixtures and fresh gas flows (FGF) on the relationship between the delivered (F(Del)O(2)) and inspired O(2) fraction (FIO(2)) in a circle system.

STUDY DESIGN

Randomized clinical study.

SETTING

Large teaching hospital.

PATIENTS

160 ASA physical status I, II, and III patients undergoing a variety of cardiovascular procedures with general endotracheal anesthesia.

INTERVENTIONS

160 patients were randomly assigned to one of 20 groups (n = 8 each), depending on the combination of total FGF (0.5, 1, 2, 4, or 8 L/min) and air-O(2) mixture used (ratios of 4/1, 3/2, 2/3, or 1/4), corresponding to a F(Del)O(2) of 0.37, 0.53, 0.68, and 0.84. For each combination of FGF and air-O(2) mixture, FIO(2) after equilibration was compared with F(Del)O(2).

MEASUREMENTS AND MAIN RESULTS

With any air-O(2) mixture with a FGF < or = 2 L/min, FIO(2) became lower than F(Del)O(2). Because FIO(2) decreased below 0.25 after 13 and 26 minutes in the first two patients of the 4/1 0.5 L/min air-O(2) group, this study limb was terminated.

CONCLUSIONS

When using air-O(2) mixtures in a circle system, FIO(2) becomes lower than the F(Del)O(2) with FGF < or = 2 L/min. The relative proportion of O(2) in the FGF has to be increased accordingly.

Endovascular treatment of an acute type B dissection: a case report

The case of a young man with acute type B dissection is reported. Inserting an endovascular stentgraft was the treatment of choice, with a good short-term result. We do believe that this is a promising strategy in the management of this serious pathology in which the classical surgical treatment is still associated with an important mortality and morbidity.

The ADU vaporizing unit: a new vaporizer

We determined the performance of the vaporizer of the ADU machine (Anesthesia Delivery Unit; Datex-Ohmeda, Helsinki, Finland). The effects of carrier gas composition (oxygen, oxygen/N(2)O mixture, and air) and fresh gas flow (0.2 to 10 L/min) on vaporizer performance were examined with variable concentrations of isoflurane, sevoflurane, and desflurane across the whole range of each vaporizer's output. In addition, the effects of sudden changes in fresh gas flow and carrier gas composition, back pressure, flushing, and tipping were assessed. Vaporizer output depended on fresh gas flow, carrier gas composition, dial settings, and the drug used. Vaporizer output remained within 10% of dial setting with fresh gas flows of 0.3-10 L/min for isoflurane, within 10% of dial setting with fresh gas flows of 0.5-5 L/min for sevoflurane, and within 13% of dial setting with fresh gas flows of 0.5 to 1 L/min for desflurane. Outside these fresh gas flow ranges, output deviated more. The effect of sudden changes in fresh gas flow or carrier gas composition, back pressure, flushing, and tipping was minimal. We conclude that the ADU vaporizer performs well under most clinical conditions. Despite a different design and the use of complex algorithms to improve accuracy, the same physical factors affecting the performance of conventional vaporizers also affect the ADU vaporizer.

IMPLICATIONS

The ADU vaporizer performs well under most clinical conditions. Despite a different design and the use of complex algorithms to improve accuracy, the same physical factors affecting the performance of conventional vaporizers also affect the ADU vaporizer.

Dose requirements of infusions of cisatracurium or rocuronium during hypothermic cardiopulmonary bypass

We investigated the influence of mild hypothermic cardiopulmonary bypass (CPB) on the dose requirements of cisatracurium or rocuronium used as a continuous infusion. We studied eight patients given cisatracurium and nine given rocuronium. They were ASA class III and IV and scheduled for elective coronary artery bypass grafting. Neuromuscular transmission was monitored electromyographically. After recovery of T1/T0 to 10%, a cisatracurium infusion or a rocuronium infusion was started at a rate of 1.5 or 10 micrograms kg-1 min-1, respectively, and adjusted to maintain T1/T0 at 15%. Infusion rate and duration were recorded before, during and after CPB in each patient and the mean infusion rates were calculated. One-way ANOVA showed a statistically significant difference between the cisatracurium infusion rates before, during and after CPB: A T1/T0 of 15% could be achieved with a mean infusion rate of 1.1, 0.75 and 0.98 micrograms kg-1 min-1 before, during and after CPB, respectively. There was no significant difference between the rocuronium infusion rates before, during and after CPB. The mean rocuronium infusion rate required to maintain T1/T0 at 15% throughout the procedure was 4.1 micrograms kg-1 min-1. Cisatracurium infusion rates should be halved during CPB. Even after CPB, requirements are reduced. The same tendency occurs with rocuronium, but the changes in infusion rate were not statistically significant.

Catheter entrapment by atrial suture during minimally invasive port-access cardiac surgery

PURPOSE

The port-access approach allows surgeons to perform heart operations through small intercostal openings, or "ports". This technique requires new skills for anesthesiologists. A pulmonary artery venting (PAV) catheter and, in some cases, a coronary sinus catheter (for administration of retrograde cardioplegia) are positioned with the aid of fluoroscopy and transesophageal echography (TEE). Both catheters have a wider diameter than the more commonly used conventional PA catheter and present distinctive features. We report a case in which a pulmonary artery venting catheter was entrapped by a suture during a port-access procedure.

CLINICAL FEATURES

A 35-yr-old man with severe mitral valve insufficiency was scheduled for valve repair. After a successful bypass procedure, resistance was felt while attempting to withdraw the PAV catheter. On fluoroscopy, fixation of the catheter at the heart level was established and perforation by suture was confirmed after injection of a contrast agent. Because of the risk of cardiac wall rupture and tamponade, the thorax was reopened. After release of some atrial sutures, the catheter could be withdrawn easily. Transfixion by a suture was confirmed by visual examination.

CONCLUSION

The more frequent use of a PAV catheter in minimally invasive cardiac surgery with the port-access technique should remind the anesthesiologist of the higher risk of entrapment by surgical sutures. Surgeons should be aware of the risk of accidentally transfixing this catheter during closure of the atriotomy via the port.

Use of ketanserin in the treatment of hypertension following coronary artery surgery

Ketanserin, a selective S2-serotonin receptor blocker with alpha 1-adrenergic blocking effects, may be a suitable antihypertensive medication after coronary artery surgery and lacks side effects seen with other vasodilators. Fifty patients with systolic blood pressures greater than 150 mmHg after coronary artery surgery were given, in a randomized double-blind fashion, either ketanserin (K) or saline (S). Each patient received six successive boluses of 1 mL of S or 1 mL of K (5 mg) at 2-minute intervals. After the last injection, sodium nitroprusside was started whenever the systolic blood pressure exceeded 150 mmHg. In the K group, the following significant (P < 0.05) changes occurred: systolic and diastolic arterial pressure -12% and -11%, respectively; heart rate -3%; systolic and diastolic pulmonary artery pressure -5% and -6%; central venous pressure -5%; pulmonary capillary wedge pressure -5%; systemic vascular resistance -16%; pulmonary vascular resistance -8%; stroke index +6%. None of these parameters changed significantly in the S group. There was no change in pulmonary shunt fraction in either group. In the K group, five patients did not require any further antihypertensive therapy during the 120 minutes following the last bolus injection. Twenty patients needed sodium nitroprusside during this period. This occurred 37 minutes (+/- 17 min) after the last bolus. In conclusion, after coronary artery bypass surgery, K is an effective antihypertensive medication, which does not cause reflex tachycardia or an increase in pulmonary shunt fraction. Exceeding the recommended dose of 10 (or 20) mg, as done in this study, does not seem to improve effectiveness or prolong the duration of action.

Effects of dobutamine and/or nitroprusside on the pulmonary circulation in patients with pulmonary hypertension secondary to end-stage heart failure

Nine NYHA class III-IV patients awaiting heart transplantation (HTx) were studied with a right ventricular ejection fraction (RVEF) catheter. The first aim of the study was to explore the pulmonary and systemic circulatory effects of dobutamine (D) and/or nitroprusside (N) in these patients. The second aim was to search for the parameter(s) among those usually measured that best predicted RVEF. Baseline data were recorded after 30 minutes of stabilization. Then, three drug regimens were administered in a randomized order for 30 minutes each: D, 4 micrograms/kg/min; N, 0.25 to 1.0 micrograms/kg/min; and their combination. Significant changes in RV loading and function were observed with all three therapies. The combination of both drugs was superior to either drug alone. The best predictor of RVEF was pulmonary arterial elastance. The second best was pulmonary capillary wedge pressure (PCWP). Pulmonary artery pressures, pulmonary vascular resistances, and transpulmonary gradient (TPG) were of less predictive value, as shown by a multiple regression analysis. None of the drugs showed any selectivity for the pulmonary vasculature, because the ratio PVRI/SVRI was never changed significantly. Selective pulmonary arterial vascular smooth muscle relaxation is probably not the most important mechanism to explain the unloading and improvement in function of the RV with D and/or N. Improved myocardial pump function appears to be the major factor in unloading the RV via reduction of PCWP and mean pulmonary artery pressure with essentially no change in TPG. The RVEF catheter provides valuable additional information in the screening of HTx candidates for pulmonary hypertension.

Reliability of auscultation in positioning of double-lumen endobronchial tubes

Auscultation is a well-established technique to confirm the position of double-lumen endobronchial tubes (DLTs). However, some authors have recommended that fibreoptic bronchoscopy (FOB) is also indicated. The aims of this study were to determine first if bronchoscopy after blind placement of DLTs improved positioning; and second if preoperative bronchoscopy could detect difficult intubation. Twenty-four patients undergoing aortic or lung surgery were studied. After intubation with a single-lumen tube, an initial FOB was performed by an independent observer to check the airway anatomy. Then, the single-lumen tube was replaced by a DLT using a classical "blind" intubation method. Subsequent FOB was performed first by the independent observer to record the DLT position and next by the investigators for improvement or correction of their positioning under visual control. Fibreoptic bronchoscopy after blind placement of DLTs resulted in repositioning 78% left-sided DLTs and 83% right-sided DLTs. Preoperative bronchoscopy did not always detect an airway abnormality which might lead to difficult positioning of the DLTs. In conclusion, auscultation is an unreliable method of confirming the position of DLTs and should be followed by fibreoptic bronchoscopy.

Heart transplantation

From September 1988 until March 1990, 22 orthotopic heart transplantations (HTX) were performed in 20 patients (18 male and 2 female). Median age was 56.5 years (23-66). The indication for HTX was an end-stage ischemic disease in 7 pts. a dilated cardiomyopathy in 13 pts, and a retransplantation in 2 pts. The mean waiting time was 58 days. Immunosuppressive therapy included OKT3, prednisone and azathioprine. Cyclosporine was introduced at day 10. Donor hearts were obtained from our institution in 5 cases, from other hospitals in Belgium in 9 cases, and from other European countries in 8 cases. The mean ischemic time was 129 +/- 28 min. No patient died in the operating room. During the first postoperative month, weekly endomyocardial biopsies were performed to detect early rejection. Five patients died in the early postoperative period, mainly from rejection. After a mean hospital stay of 23 days, 15 patients (75%) were discharged. During the late follow-up, 3 patients died: 1 from chronic mediasdinitis, 1 from hypoglycemia, and 1 from cardiac arrest following non-compliance with the medical treatment. In conclusion, early acute rejection after HTX still remains a major cause of death.