Anesth Analg 2004;99:1330-1333
© 2004 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000132984.56312.FF
CARDIOVASCULAR ANESTHESIA
Is Muscle Relaxant Necessary for Cardiac Surgery?
G. Gueret, MD,
B. Rossignol, MD,
G. Kiss, MD,
J. P. Wargnier, MD,
A. Miossec, MD,
S. Spielman, MD, and
C. C. Arvieux, MD PhD
Département d’Anesthésie Réanimation, Centre Hospitalier la Cavale Blanche, Brest, France
Address correspondence and reprint requests to G. Gueret, MD, Département d’Anesthésie Réanimation, CHU la Cavale Blanche, 29609 Brest, France. Address e-mail to gildas.gueret{at}chu-brest.fr
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Abstract
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The need for continuous and complete paralysis during the entire cardiac surgery has not yet been investigated and is still controversial. In a series of 87 patients undergoing cardiac surgery with normothermic cardiopulmonary bypass, we studied the delay of recovery, incidence of residual paralysis, unwanted patient movement, and difficult surgical conditions after a single dose of atracurium (0.5 mg/kg) or cisatracurium (0.15 mg/kg). Anesthesia was induced with etomidate and remifentanil followed by tracheal intubation. The delay to obtain a train-of-four ratio of >0.9 was longer with cisatracurium than with atracurium (86 ± 18 versus 97 ± 19 min). However, at the end of surgery, this ratio was >0.9 for all patients. The presence of unwanted patient movement, diaphragmatic contractions, and difficult surgical conditions were observed. Delay of extubation of the trachea was similar in both groups. We conclude that there is no need for continuous neuromuscular blockade during cardiac surgery. A single dose of either atracurium or cisatracurium is sufficient to provide efficient paralysis from the start of induction leading to quicker recovery from paralysis in fast-track cardiac surgery.
IMPLICATIONS: Residual paralysis as a result of repetitive doses or continuous administration of muscle relaxants is counterproductive for fast-track cardiac surgery which aims for early postoperative extubation and quick recovery. Perioperative patient movement, unwanted diaphragmatic contractions, difficult surgical conditions, and residual paralysis were prevented in 87 patients undergoing cardiac surgery by injecting a single dose of either atracurium or cisatracurium during induction of anesthesia. This practice has no negative impact on surgery and allows early and safe extubation of the trachea.
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Introduction
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Residual paralysis after cardiac surgery is often the result of continuous perioperative neuromuscular blockade (1–6). It is common when pancuronium is used (1,3–6) but is less frequent with the use of an intermediate-acting nondepolarizing neuromuscular blocking drug such as rocuronium (1,4–6). The incidence of residual postoperative paralysis is still significant with repetitive or continuous perioperative muscle relaxation, despite the use of intermediate-acting neuromuscular blocking drugs (1,3–5). Administration of repetitive doses or continuous infusion of neuromuscular blocking drugs is guided by monitoring of neuromuscular blockade, thereby preventing patient movement during cardiac surgery. The need for continuous paralysis during cardiac surgery has not yet been investigated. Likewise, the postoperative incidence of residual paralysis is unknown after a single-dose injection of atracurium or cisatracurium. The aim of this prospective study was to investigate how a single-dose injection of atracurium or cisatracurium at induction of on-pump cardiac surgery would influence the delay of neuromuscular recovery, the incidence of residual paralysis, and whether there may be any negative impact on surgery such as unwanted diaphragmatic contractions or patient movement.
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Methods
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After approval of our institutional ethics committee, 87 patients gave preoperative informed consent. They underwent cardiac surgery at the University Hospital of Brest (France) and were prospectively included in our study. Patients were randomly assigned into two groups receiving either a single dose of atracurium or cisatracurium during induction of anesthesia. Because the intention of this study was not to change our standard practice of cardiac surgery, the sole exclusion criteria was off-pump cardiac surgery. Surgeons were blinded for the study.
Patients received oral premedication of 0.1 mg/kg midazolam 1 h before anesthetic induction. Anesthesia was induced with etomidate (0.2 mg/kg) and remifentanil at an infusion rate of 0.25 µg · kg–1 · min–1 and maintained with a target-controlled infusion of propofol (plasma concentration 0.7–2 µg/mL) and a continuous infusion of remifentanil (0.1–0.5 µg · kg–1 · min–1). Bispectral analysis of the electroencephalogram was used as a guide for anesthetic depth and bispectral index levels were maintained between 40 and 55. During normothermic cardiopulmonary bypass (CPB) assisted with retrograde blood cardioplegia, the average arterial blood pressure was maintained between 50 to 80 mm Hg using a slow infusion rate of norepinephrine if necessary. The hematocrit was maintained at >20% during CPB. Aprotinine was added to the CPB priming (2.10–6 international units [IU]) and during induction at an initial dose of 2.10–6 IU followed by an infusion rate of 0.5.10–6 IU/h. After surgery, the patient was transferred to the cardiothoracic intensive care unit (CICU) where sedation was continued with propofol and remifentanil until core temperature was >36.5°C. The patient was tracheally extubated when the following criteria were met: a fraction of inspired oxygen of <0.5 resulting in a PaO2 of >70 mm Hg, hemodynamic stability, blood loss of <50 mL/h, a core temperature of >36.5°C, and a consciousness level of >2 on the Ramsay sedation score. Neuromuscular blockade was measured with a train-of-four (TOF) using an accelerator device. The stimulation electrodes were on the wrist at the level of the ulnar nerve and the accelerometer was attached at the distal interphalangeal joint of the thumb. After induction, as soon as the patient lost consciousness, the TOF watch was calibrated. Atracurium (0.5 mg/kg) or cisatracurium (0.15 mg/kg) was administered and the ulnar nerve was stimulated every 15 s using a TOF supramaximal stimulation of 50 mA. The patient was tracheally intubated once the motor response of the adductor pollicis muscle had disappeared. Perioperatively, the following data were collected: the delay to obtain a TOF ratio of >0.7–0.9; the incidence of residual paralysis, defined as a T4/T1 ratio of <0.9 at the end of surgery; any patient movement during the entire surgery; diaphragmatic contractions observed either as cough or respiratory attempts or subjectively/objectively experienced by surgeons; and the impact of anesthesia on surgical conditions.
2 test was applied to compare discontinuous variables, and Student’s t-test was used to compare unpaired series of continuous variables. The Mann-Whitney’s test analyzed non-normal distributions. A P value < 0.5 was considered as significant.
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Results
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Forty-two patients receiving atracurium and 45 receiving cisatracurium were included in the study. Preoperative data were similar in both groups (Table 1). Duration of surgery was not different between groups (Table 2). The delay in obtaining a T4/T1 ratio of >0.7–0.9 was longer with cisatracurium. However, at the end of surgery, all patients had a T4/T1 ratio of >0.9. The delay for extubation of the trachea was similar in both groups (Table 3). The absence of continuous paralysis did not have any negative impact on surgery and there were neither diaphragmatic contractions nor patient movement. Surgeons were not concerned by the absence of neuromuscular blockade. All patients but one left the CICU within 48 h after admission. The remaining patient in the cisatracurium group had surgery for a left atrial myxoma and remained intubated for 16 h. He stayed in the CICU for 4 days because of postoperative hypoxemia. None of the patients was taken back into the operating room.
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Discussion
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Despite injecting only a single dose of atracurium or cisatracurium to facilitate tracheal intubation, this prospective study demonstrates that cardiac surgery was not accompanied by unwanted patient movement or diaphragmatic contractions. Neither was any negative impact on surgery observed by surgeons, nor was any residual paralysis measured at the end of surgery. We think that if anesthetic depth is well maintained throughout surgery, there is no need for continuous neuromuscular blockade. Whether there is a single-dose administration of neuromuscular blocking drug or continuous muscle relaxation, surgical conditions remain equally good for surgeons. However, the long delay to obtain a T4/T1 ratio of >0.9 at the end of surgery confirms our opinion that there is no need to maintain neuromuscular blockade in this type of surgery. Thus, when patients left the operating room, all of them had a T4/T1 ratio of >0.9 and could have been tracheally extubated if other extubation criteria had been met. Residual paralysis, reported in studies involving fast-track cardiac surgery (1–6), requires continuous postoperative sedation until it is unmeasurable and therefore unnecessarily delays extubation. Even if given as a single-dose administration during induction of anesthesia, residual paralysis is common with pancuronium (1,3–6). There were fewer incidences of residual paralysis with rocuronium, but its occurrence was not totally suppressed (1,4,5). Prolongation of paralysis, as reported in several studies, may have partly been caused by hypothermic CPB (4–6), but the choice of neuromuscular blocking drugs (1,2,6) and its continued or repetitive administration during surgery, also have an important role. In one study only, there was no readministration of muscle relaxants (6) but the impact on the surgical procedure, such as patient movement, was not reported. Our objective in fast-track cardiac surgery was to minimize the delay of endotracheal extubation in order to limit the risk of ventilator-induced complications. By reducing such a delay from 7.2 ± 4.3 to 3.6 ± 2.4 hours, we observed a dramatic decrease of pulmonary infections in our CICU patients from 20% to <3%.
The average delay of extubation of the trachea was less than four hours in the present study. This is significantly less than those reported by McEwin et al. (1) and Ouattara et al. (2) who repeatedly administered neuromuscular blocking drugs during cardiac surgery. It should be stressed that in these studies, many of the patients were tracheally extubated while still under the effect of partial paralysis which was not the case in our study. Thomas et al. (6) administered a single dose of pancuronium during induction, but maintenance of sedation was needed after ICU admission. This was not the case for rocuronium, but the delay for extubation was not reported (6). It is evident that during cardiac surgery readministration of nondepolarizing muscle relaxants is accompanied by more frequent residual muscle paralysis (4,5) and longer ventilation time in the ICU (1,2,4,5). In the present study, the delay for endotracheal extubation was similar for both atracurium and cisatracurium. Therefore, we recommend either of them. However, cisatracurium causes less histamine release (7) which encourages its use in order to limit the hemodynamic response experienced in cardiac surgery patients.
Residual paralysis is common after cardiac surgery, particularly with long-acting neuromuscular blocking drugs or even when intermediate-acting muscle relaxants are repeatedly or continuously administered perioperatively. This residual paralysis delays endotracheal extubation which in turn increases the incidence of postoperative ventilator-induced complications. Atracurium or cisatracurium administered in a single dose to facilitate endotracheal intubation does not result in residual postoperative paralysis. The progressive decay of paralysis does not have any negative impact on surgical conditions and allows early extubation of the trachea. Therefore, in fast-track cardiac surgery, it seems unnecessary to maintain paralysis by repetitive bolus injection or continuous infusion of neuromuscular blockers which in turn will only delay extubation in patients fulfilling all other extubation criteria (1,3–5). It may even result in tracheally extubating patients still under the effect of residual paralysis.
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References
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- McEwin L, Merrick PM, Bevan DR. Residual neuromuscular blockade after cardiac surgery: pancuronium vs rocuronium. Can J Anaesth 1997; 44: 891–5.[Abstract/Free Full Text]
- Ouattara A, Richard L, Charriere JM, et al. Use of cisatracurium during fast-track cardiac surgery. Br J Anaesth 2001; 86: 130–2.[Abstract/Free Full Text]
- Van Oldenbeek C, Knowles P, Harper NJ. Residual neuromuscular block caused by pancuronium after cardiac surgery. Br J Anaesth 1999; 83: 338–9.[Abstract/Free Full Text]
- Murphy GS, Szokol JW, Marymont JH, et al. Impact of shorter-acting neuromuscular blocking agents on fast-track recovery of the cardiac surgical patient. Anesthesiology 2002; 96: 600–6.[ISI][Medline]
- Murphy GS, Szokol JW, Marymont JH, et al. Recovery of neuromuscular function after cardiac surgery: pancuronium versus rocuronium. Anesth Analg 2003; 96: 1301–7.[Abstract/Free Full Text]
- Thomas R, Smith D, Strike P. Prospective randomised double-blind comparative study of rocuronium and pancuronium in adult patients scheduled for elective ‘fast-track’ cardiac surgery involving hypothermic cardiopulmonary bypass. Anaesthesia 2003; 58: 265–71.[ISI][Medline]
- Koppert W, Blunk JA, Petersen LJ, et al. Different patterns of mast cell activation by muscle relaxants in human skin. Anesthesiology 2001; 95: 659–67.[ISI][Medline]
Accepted for publication May 5, 2004.
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Abstract
Introduction
