| Backgrounds and ObjectiveWith the aging of the population in our country, there are more and more elderly who will be underwent all kinds of operations. However, the risk of anesthesia process greatly increases due to decrease of organ function and alteration of pharmacokinetics parameter in the elderly. The old patients' anesthesia is the focus in clinical anesthesia, and anesthesiologist must find new drags and methods to improve the safety of elderly patients' anesthesia.Muscle relaxant is a very important component in general anesthesia. The traditional way of administration of muscle relaxant, intermittent intravenous injection, is still used wildly in clinical anesthesia, which can easily lead to fluctuation of intraoperative neuromuscular blockade between excessive inhibition and lack of inhibition, delay of the recovery time after surgery, high incidence of postoperative residue curarization(PORC), and even the resulting hypoxia and accident. Although the train-of-four (TOF) monitoring can overcome the above drawbacks, it is invasive and can't be accepted by conscious patients, and it has a tedious and time-consuming preparation and many influential factor, so it is hard to be used as a routine monitoring method.Target-controlled infusion (TCI) is a new type of intravenous administration technology, which is based on pharmacokinetics-pharmacodynamics (PK-PD) theory, and combine pharmacokinetic parameters of groups with computer technology. TCI could adjust and maintain the predetermained drag concentration of plasma or effective site in time by ramp infusion according to clinical request. Accordingly the fluctuation of drug concentration is reduced and controllability of anaesthesia is increased.Rocuronium is a new type midst seasoning sterid non-depolarizing muscular relaxant, it has many merits such as rapid onset and fast recovery, and has no manifest accumulation and adverse reactions. Its pharmacokinetics characteristic is consistent with three-compartment model, so it is suitable for TCI. There are individual cases reported about the application of target-controlled infusion of rocuronium for non-elderly patients, but there is not accepted argument about suitable target concentration of rocuronium on the elderly.The purpose of this study was to explore a reasonable dose regimen of target -controlled infusion of rocuronium for the elderly patients in order to implement smooth intubation condition in the period of induction, satisfactory muscle relaxation during operation, and fast reversal of neuromuscular block after surgery, even in the absence of TOF monitoring, and to enhance the safety and controllability of administration of muscular relaxant in elderly patients, accordingly.Methods60 elderly patients (ASA II, aged 65-80) scheduled for selective surgical procedure under general anesthesia were studied. The body weight was controlled in normal range by body mass index. Patients with significant heart, lung, liver, renal and neuromuscular diseases were excluded. None of them had taken preoperative drugs which can affect neuromuscular transmission function.The patients were randomly divided into four groups, A,B,C and D ,with 15 cases in each group. The target effective site concentration (Ce) of rocuronium for trachea intubation was 3μg·ml-1 in A,B,C group and 3.3μg·ml-1 in D group, and the Ce during surgery were maintained at 0.6μg·ml-1, 0.8μg·ml-1, 1.0μg·ml-1 and 0.8μg·ml-1 in A,B,C and D group, respectively.All the patients did not have premedicant. Accelerograph was settled on them for neuromuscular block monitoring after they have been brought into operating room. Anesthesia induction was performed with midazolam 0.1 mg·kg-1 and fentanil 5μg·kg-1 in order by intravenous injection. When the patients lost consciousness, accelerograph calibration was carried out by stimulation of ulnar nerve, and then target controlled infusion of rocuronium was administrated. The patients were intubated and mechanically ventilated as soon as T1/TC≤5%. After the induction dosage of rocuronium, the Ce was down regulated to predetermined maintain level during operation in each group. If the condition of T1/TC > 10% appeared during surgery, the Ce of rocuronium was up regulated by 0.2μg·ml-1 untill T1/TC≤10%. TCI of rocuronium was stopped at the end of surgery, neuromuscular block was not antagonized after operation and spontaneous recovery of muscle relaxation was recorded.The following indicatrixes were observed and recorded:1. onset time;2. intubation condition;3. perioperative neuromuscular block degree;4. values of T1/TC and skin temperature of thenar eminence at the moment of target effective site concentration of rocuronium descended to the predetermined intraoperative maintain level, and the time points of every twenty minutes interval subsequently;5. time consumption of surgery and TCI, and rocuronium dosage;6. recovery time to 25% of T1/TC, and recovery index;7. Ce of rocuronium at the moment of intubation, and the time points when T1/TC returned to 10%,20%,25%,30%,40%,50%,60%,70% 75%,80%,90% in the period of neuromuscular block recovery after surgery.Results1. General informationThere were no significant difference on age, height, weight, gender composition, time consumption of operation and TCI among four groups (P>0.05). There were no significant difference on skin temperature of thenar eminence between random consecutive two points in the period of TOF monitoring among four groups (P>0.05).2. Intubation conditionThere were no significant difference on intubation qualification and Ce of rocuronium at the moment of intubation among four groups (P>0.05), but onset time of D group was shorter than A, B and C group, and the difference was statistically significant (P <0.05).3. Perioperative neuromuscular block degreeThe satisfaction rate of neuromuscular block in A group was lower than B, C and D group, and the difference was statistically significant (P<0.05). Although there were overall satisfaction rate of neuromuscular block among B, C and D groups(P>0.05), but neuromuscular block depth in C group was greater than B and D group(P<0.05), and there was no significant difference on distribution of neuromuscular block between B and D group(P>0.05). There were no significant difference on neuromuscular blockade degree between random consecutive two points in the period of muscle relaxation maintain of every patient in B, C and D groups, respectively(P>0.05).4. Recovery condition of neuromuscular blockThere were no significant difference on rocuronium total and duration dosage, and the recovery time to 25% of T1/TC between B and D group(P>0.05), but the above-mentioned three indicatrixes in C group were greater than B and C group(P<0.05). There were no significant difference on recovery index and the Ce of rocuronium at the monment of 25% of T1/ TC in the period of neuromuscular block recovery after surgery among B, C and D groups(P>0.05).5. Relationship of Ce and T1/TC in the period of muscle relaxation recoveryThe value of T1/TC in the period of neuromuscular block recovery was regarded as independent variable (X) , and the average of propotional Ce of rocuronium was regarded as dependent variable ( Y ) . The relationship of Ce and T1/TC in B, C and D groups were studied by linear regression analysis, respectively. There was a significant negative correlation between Ce and T1/TC, and there were no significant difference in regression coefficient and intercept among three regression equations.ConclusionThe programme of D group is a reasonable dose regimen of target-controlled infusion of rocuronium for elderly patients, which could implement smooth intubation condition in the period of induction, satisfactory muscle relaxation during operation, and fast reversal of neuromuscular block after surgery without TOF monitoring. |
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