Continuous epidural analgesia: experience with mechanical injection devices

Tachyphylaxis in major depressive disorder: A review of the current state of research

BACKGROUND

Patients with major depressive disorder (MDD) often experience a re-emergence or worsening of symptoms despite ongoing treatment with previously effective antidepressant pharmacotherapy. This lost or reduced antidepressant response during maintenance, referred to as tachyphylaxis, negatively impacts treatment outcomes and quality of life for patients with MDD. This review assesses the prevalence of antidepressant tachyphylaxis as well as the evidence for interventions to manage it.

METHODS

We searched PubMed/Medline for the relevant clinical trials and meta-analyses on antidepressant tachyphylaxis up to January 2017. Search terms included "depression" paired with "treatment" (n = 186,674), "tachyphylaxis" paired with "depression" (n = 112), "tachyphylaxis" paired with "major depressive disorder" (n = 21), and "antidepressant" paired with "tachyphylaxis" (n = 68). Studies were included if they reported on a clinical trial or meta-analysis exploring tachyphylaxis in MDD and were excluded if the sample population did not have a primary DSM diagnosis of MDD.

RESULTS

Rates of tachyphylaxis varied from 9% to 57% depending on the patient population and duration of follow-up. Limited evidence suggests potentially beneficial strategies for managing tachyphylaxis, including change in antidepressant dosing, switch of class of antidepressant medication, augmentation or combination pharmacotherapy, and psychotherapy.

LIMITATIONS

Studies of antidepressant tachyphylaxis are largely heterogeneous in nature and employ strict inclusion/exclusion criteria; thus, these findings may not be generalizable to all depressed populations.

CONCLUSION

Few established treatment strategies exist to manage antidepressant tachyphylaxis. Further interventional research is needed to provide symptomatic relief for patients with tachyphylaxis in MDD.

A comparative study of continuous and intermittent epidural analgesia for labour and delivery

This study compares a continuous infusion technique with intermittent "top-up" doses using 0.25 per cent bupivacaine for epidural analgesia for labour and delivery in healthy primiparous patients. Sixty women were randomized into two groups, A (continuous) and B (intermittent). Twenty-eight patients in Group A and 29 in Group B completed the study. We compared the groups with regard to satisfaction with pain relief for both labour and delivery as measured by a Visual Analogue Scale on five occasions during and after parturition. There was no difference between groups at any of the five stages. The difference in pain scores before the epidural and after the epidural was significant for both groups (p less than 0.001). The incidence of missed segments, degrees of motor block, height of sensory block, length of labour and fetal outcome were similar in both groups. Plasma bupivacaine levels were measured in six patients in each group. Mothers in Group A received more drug than those in Group B (p less than 0.01) but plasma bupivacaine levels remained low in the mother and the umbilical cord samples in the sub-set from this group. More women in Group A required outlet forceps (p less than 0.05) whereas mid-forceps and Caesarean section rates were similar in the two groups. Fewer mothers in the infusion group had spontaneous vaginal delivery. We conclude that infusion techniques are as effective as intermittent top-up epidurals and are well received by mothers in labour.

Plasma bupivacaine concentrations during postoperative continuous epidural analgesia

Postoperative analgesia and plasma concentrations of bupivacaine were evaluated in six patients receiving intermittent epidural bupivacaine for a period of 72 hours following large bowel surgery. Repeated doses were administered every hour by a new automatic, specially designed pump. Venous plasma bupivacaine concentrations showed accumulation for up to 48-60 hours during administration and were mostly less than 2 micrograms/ml except in an elderly, frail patient in whom a peak of 3.9 micrograms/ml was observed. This convenient, low-dose, pulsed technique provided excellent analgesia although special care may be necessary in the elderly and frail patient if potentially toxic levels are to be avoided.

Continuous epidural analgesia for vaginal delivery in Sweden. Report of a nationwide inquiry

Volumetric pump infusion of bupivacaine into the epidural space for pain relief during labour was introduced in Sweden in 1976. Since then the method has gained widespread use. A questionnaire concerning the use of epidural analgesia (EDA) in 1982 was sent to anaesthetists at all Swedish maternity clinics. During the year, 84 188 vaginal deliveries were registered. EDA for pain relief was performed in 11 324 of them (13.4%). At that time, EDA was available in 56 out of 66 clinics. In almost all clinics (52/56), bupivacaine plain 2.5 mg/ml was used for the blocks. Analgesia was maintained by volumetric pump infusion of bupivacaine in 28 units, by intermittent technique in 25, and both techniques were used in three units. No clinic had abandoned the infusion technique once it had been introduced. Experience from both techniques showed the infusion technique to be more convenient as it produces stable analgesia, is easily conducted and can be supervised by midwives. No complication which could be connected with infusion technique was noted. Maternal hypotension was rare and the instrumental delivery rate was low. The technique proved to be a valuable aid to the organisation of a 24-h service for obstetric analgesia, without requiring any increase in staff.

A simple safe method for continuous infusion epidural analgesia in obstetrics

Continuous infusion epidural anaesthesia may reduce the risks of hypotension, high spinal block and intravenous injection associated with repeated bolus injections. However, controlling the rate of a simple infusion is difficult and infusion pumps are expensive and bulky. We describe a method for continuous infusion epidural anesthesia using a 6 ml/hr capillary infusion device (Intraflo CFS-06F Sorenson Research Co., Salt Lake City, Utah) and bupivicaine 0.25 per cent. In a study of 50 patients, 35 (70 per cent) had adequate pain relief with the infusion alone for a mean time until delivery of 5 hours (range 2 to 13 hours). A further 11 patients (22 per cent) required only one top-up for the second stage of labour after a mean pain-free time of 5.4 hours (range 1.5 to 9.7 hours). There were no maternal or foetal complications related to the technique of continuous infusion used. No block went higher than the ninth thoracic dermatome at any time.

Continuous epidural infusion of bupivacaine in labour: a simple method

Thirty patients were given a constant epidural infusion in labour by gravity feed drip of approximately 10 ml of 0.25% bupivacaine per hr. The infusion proved a simple and reliable method of ensuring adequate analgesia throughout labour. There were no problems of drug toxicity and the incidence of complications and side effects was comparable to a previous series using intermittent 0.5% bupivacaine.

The use of procaine hydrochloride as a continuous lumbar epidural technique in labour

A continuous technique for lumbar epidural during labour is described, using procaine hydrochloride without adrenaline. An investigation was undertaken to determine the action of procaine in labour, to determine whether this drug could facilitate a normal delivery and to study maternal and fetal blood procaine levels. The technique, although successful, offered no specific advantages.

Continuous epidural analgesia in the obstetric patient: a feasibility study using a mechanical infusion pump

Eleven patients in uncomplicated labour received a continuous infusion of 0-125 or 0-25% bupivacaine solutions into the epidural space, using a simple rotary pump. Maternal and umbilical cord venous plasma bupivacaine levels were measured and were found to be within safe limits for mother and baby. Incidence of complications were noted.

Thoracic epidural analgesia-II: prolongation in the early postoperative period by continuous injection of 1.0% bupivacaine

Sixteen patients were given thoracic epidural analgesia at the T5-T6 level with 2 ml of 1.0% bupivacaine solution plain for pain relief after upper abdominal surgery. In 13 cases the analgesia was prolonged by continuous injection of 1.0% bupivacaine for 24 or 48 h. Onset time and segmental spread of the analgesia are presented as well as segmental spread, intensity of the blockade, and peak expiratory flow rates during prolongation. Signs of tachyphylaxis were noticed, and also signs of accumulation of bupivacaine in plasma. A high incidence of urinary retention occurred. The method is not considered to be ideal for pain relief after upper abdominal surgery.

General derivation of the ideal intravenous drug input required to achieve and maintain a constant plasma drug concentration. Theoretical application to lignocaine therapy

A constant plasma drug concentration can be achieved and maintained by the intravenous administration of an initial bolus loading dose in conjunction with a constant rate and an exponential intravenous drug infusion. The drug input required to achieve a constant plasma drug concentration is derived without making any assumptions about the nature of drug distribution within the body or elimination from the body.

Thoracic epidural analgesia I-a double-blind study between bupivacaine and etidocaine

A double-blind comparison was made in 40 patients undergoing thoracic epidural analgesia with either bupivacaine 0.5% or etidocaine 1.0%, both with adrenaline 5 mug/ml. All patients were undergoing elective upper abdominal surgery. They were studied both pre- and postoperatively. The parameters measured were: onset time, segmental spread and duration of analgesia; and also systolic blood pressure, heart rate and peak expiratory flow rate. In respect of these parameters, no major differences were found between the two solutions under the conditions of the study. The overall results, however, differ in many respects to those found when these agents are used in lumbar epidural analgesia.