Testing the epidural catheter

Epidural test dose in obstetric patients: should we still use it?

PURPOSE OF REVIEW

As the application of a test dose after epidural catheter insertion in obstetrics has recurrently been associated with serious adverse events affecting both maternal and foetal outcomes, the question whether to test or not remains a controversial issue.

RECENT FINDINGS

Present guidelines do not provide clear recommendations in this regard and several recent surveys indicate a heterogeneity in clinical routine.

SUMMARY

Physiological alterations during pregnancy and labour restrict the use and also the validity of traditional test agents. Epinephrine is not appropriate to detect a vascular insertion in labour and the application of a local anaesthetic test dose may lead to dose-dependent fatal consequences should the catheter be intrathecal, due to an increased sensitivity in parturients. Given the current practice of opioid-amended-low-concentration epidurals, the waiving of a test dose results at worst in a failed epidural, a stark contrast to the potentially severe to fatal complications of a 'traditional' test dose. Hence, an originally preventive measure providing potentially more harm than the consequences of the situation aimed to prevent, should not be recommended. A simple fractionated administration of the initial analgesic dose seems reasonable though.

Epidural electrical stimulation test versus local anesthetic test dose for thoracic epidural catheter placement: a prospective observational study

PURPOSE

This study examined the concordance between epidural electrical stimulation test (EEST) and local anesthetic (LA) test dose to indicate correct thoracic epidural catheter position. The relationship between the test results and epidural postoperative analgesia was also assessed.

METHODS

This prospective observational cohort study was done in patients receiving thoracic epidural analgesia for abdominal surgery. After insertion, the epidural catheter was tested using a nerve stimulator to elicit a motor response. The LA test dose was then administered, and sensory block to ice and pinprick was assessed. The primary outcome was the presence/absence of motor response to EEST and sensory block to test dose. Concordance of responses was assessed using kappa statistics, and their predictive power of postoperative epidural analgesia was evaluated.

RESULTS

Sixty-eight thoracic epidural catheters were inserted, of which 62 were used perioperatively. The kappa agreement between EEST and LA test dose responses was moderate at 0.42 (95% confidence interval [CI], 0.18 to 0.67). Positive responses to EEST and LA test dose were observed in 62 (100%) and 50 (81%) patients, respectively, while 52 patients (84%) showed adequate analgesia postoperatively. The sensitivity (95% CI) of EEST and LA test dose to predict adequate postoperative epidural analgesia was 1 (0.93 to 1) and 0.79 (0.65 to 0.89), respectively, and the positive predictive values (95% CI) of EEST and LA test dose were 0.84 (0.75 to 0.93) and 0.82 (0.71 to 0.92), respectively.

CONCLUSION

Following thoracic epidural catheter insertion, the responses to the EEST and LA test dose showed "moderate" agreement. The EEST has a higher sensitivity than the LA test dose to predict adequate epidural analgesia following abdominal surgery, however, both tests have a comparable positive predictive value.

Accidental Dural Puncture Management: 10-Year Experience at an Academic Tertiary Care Center

BACKGROUND AND OBJECTIVES

The use of spinal catheters for extended periods after accidental dural puncture (ADP) and administration of intrathecal saline via spinal catheters have been advocated to decrease the incidence of postdural puncture headache and the subsequent need for epidural blood patch (EBP), with mixed results observed.

METHODS

We reviewed the medical records of 218 patients with ADP who either had the epidural resited or had a spinal catheter (with or without the administration of intrathecal saline). We compared the incidence of headache and the need for blood patch between these groups. We also assessed complications when a standard lidocaine epidural test dose was administered intrathecally and compared this with complications when a solution normally used for labor combined spinal epidurals was administered.

RESULTS

There was no difference in the incidence of postdural puncture headache between the resited epidural group and the spinal catheter group, 68.0% versus 55.9% (odds ratio [OR], 1.7; 95% confidence interval [95% CI], 1.0-2.9; P = 0.07). Resiting the epidural catheter was associated with a significant increase in the number of EBPs when compared with using a spinal catheter, 52.0% versus 20.3% (OR, 4.2; 95% CI, 2.4-7.6; P < 0.001) and when compared with spinal catheters with intrathecal saline, 52.0% versus 8.1% (OR, 12.3; 95% CI, 4.3-35.4; P < 0.001). There was a significant difference in the number of blood patches between normal body mass index patients and morbidly obese patients, 55.2% versus 25.0% (OR, 3.7; 95% CI, 1.2-11.2; P = 0.02). Complications (hypotension prompting pressors, high spinal, and emergency cesarean delivery because of nonreassuring fetal status) occurred more frequently when a lidocaine test dose was immediately administered after ADP versus administering a labor combined spinal epidural solution.

CONCLUSIONS

Insertion of spinal catheters after ADP and administration of intrathecal normal saline via spinal catheters reduce the need for EBP compared with resiting the epidural. Administration of the standard epidural test dose intrathecally is associated with frequent and significant complications.

Epidural chloroprocaine bolus in emergency cesarean section-lessons learned from a near mishap

Administration of a large bolus of epidural chloroprocaine to hasten the spread of anesthesia is an accepted practice during emergency cesarean section. Occasionally, this practice can result in a very high block that can compromise patient's safety. We describe a case of epidural chloroprocaine administration in a 4 point position resulting in a high dermatomal block requiring respiratory assistance. Events surrounding the case are discussed, with a view to warn the reader about the pitfalls of such a practice.

[Epidural anaesthesia: Simulated intravascular test dose with S(+) ketamine, lidocaine and adrenaline. A prospective, randomized, double blind and placebo controlled study]

OBJECTIVE

The use of a test dose in epidural anaesthesia is a safety recommendation. However specificity and sensitivity of the drugs used with this indication have been not conclusive. The main objective of this study was to compare the effectiveness and the adverse effects of a simulated intravascular test dose of adrenaline, lidocaine and S(+)-ketamine.

MATERIAL AND METHODS

A prospective, randomized, double blinded, placebo controlled study was designed. ASA I patients scheduled for elective surgery were included. These were randomized to the following study groups: S(+)-ketamine 0.5 mg.kg-1 (S+K group), 5% lidocaine 1.5 mg.kg-1 (L5% group), adrenaline 15μg (ADR group), and physiological saline 3 ml (SF group; control group). An evaluation was made during the first 15 minutes after the study drug was administered. Variables including heart rate (HR) systolic and diastolic blood pressure (sBP and dBP), mean arterial pressure (MAP), and SpO2 were recorded at 0 min (baseline) and at 2, 5, 8, 10 and 15 minutes after drug injection. An increase of at least 20 beats per minute (bpm) in relation to the baseline measurement was considered a positive result, as was an increase sBP >15 mmHg. The clinical effects described as related to iv injection of the study drugs recorded were: sedation-hypnosis, dizziness, nystagmus, metallic taste perception, perioral or facial paresthesias, tinnitus, as well as any other effect the patients mentioned. Sensitivity and specificity were calculated as was the percent increase in the parameters in order to see if these were clinically useful.

RESULTS

A total of 80 patients, 20 per group, were included. The sBP, dBP, and MAP were significantly raised at the 2, 5, 8 and 10 minutes measurements in the S(+)K group compared to the rest of the groups (P<.05), as well as HR in the 2, 5, 8, 10 and 15 minute measurements in the S(+)K compared to the rest of the groups (P<.05). Sensitivity and specificity were high, and significant in the S(+)K group from minute 2 to minute 8 compared with the placebo group, as well as percentage points differences in the same interval. There were significant differences in the incidence of sedation-hypnosis, nystagmus and dizziness, which were more frequent in the S(+)K group. There were no differences in the incidence of metallic taste, perioral and facial paresthesias or tinnitus. The effects in the S(+)K group always occurred before minute 5 after drug injection.

CONCLUSION

Both lidocaine an adrenaline at the scheduled doses showed low sensitivity and specificity as a simulated iv epidural test dose. S(+)-ketamine could be a feasible marker after accidental iv injection during epidural anaesthesia or analgesia.

Late intravascular migration of a previously well functioning labour epidural catheter

Intravascular epidural catheters may result in insufficient labour analgesia or can produce potentially lethal complications following an epidural top-up. We report a case of a previously well functioning epidural catheter positioned epidurally using a combined spinal epidural anaesthesia technique, which subsequently was found to be intravascular. The literature is reviewed.