Target-controlled infusion of remifentanil or fentanyl during extra-corporeal shock-wave lithotripsy.

BACKGROUND AND OBJECTIVE: Target-controlled infusions (TCIs) of remifentanil and fentanyl in conscious sedation regimes for extra-corporeal shock-wave lithotripsy have not been reported. We estimated the effect site concentrations of remifentanil and fentanyl needed to obtain adequate analgesia in 50% of patients (EC50) and compared both drugs in terms of intra- and post-procedure complications. METHODS: Forty-four adult patients were randomly distributed into two groups: Group R received remifentanil and Group F received fentanyl TCI with initial effect site concentrations of 1.5 and 2 ng mL(-1), respectively. Pain was assessed using a 10-point verbal analogue scale and <3 was considered adequate analgesia. Increments or decrements of 0.5 ng mL(-1) were then introduced for subsequent patients according to Dixon's up and down method. During the rest of the procedure, TCI was adjusted to maintain verbal analogue scale <3. RESULTS: Remifentanil and fentanyl EC50 were 2.8 ng mL(-1) (95% confidence interval (CI): 1.8-3.7 ng mL(-1)) and 2.9 ng mL(-1) (95% CI: 1.7-4.1 ng mL(-1)), respectively (n.s.). At EC50, the probability of having a respiratory rate <10 was 4% (95% CI: 0-57%) for remifentanil and 56% (95% CI: 13-92%) for fentanyl. Hypoxaemia, vomiting and sedation were more frequent in Group F during and after the procedure (P < 0.05). CONCLUSIONS: A similar EC50 but more respiratory depression, sedation and PONV were found with fentanyl TCI than with remifentanil TCI.

Direction of catheter insertion and incidence of paresthesias and failure rate in continuous epidural anesthesia: a comparison of cephalad and caudad catheter insertion.

BACKGROUND AND OBJECTIVES: Paresthesias and unblocked segments during continuous epidural anesthesia--sometimes leading to higher doses of local anesthetics--can increase the risk of this technique. A cephalad insertion of the epidural catheter might decrease the incidence of these problems, but this has not been evaluated before in a controlled study. METHODS: In a prospective, double-blind, randomized study, we compared the incidence of paresthesias during catheter insertion and the failure rate of continuous epidural anesthesia in two groups of obstetric patients. In group 1 (n = 52), the Tuohy needle bevel was directed cephalad during catheter insertion. In group 2 (n = 53), it was directed caudad. The catheter was introduced 4-5 cm into the epidural space, and bupivacaine 25 mg plus fentanyl 50 micrograms were administered through it. RESULTS: Twenty percent of the patients in group 1 had paresthesias versus 40% in group 2 (p = 0.0249; 95% confidence interval of the difference 1-40%); intensity of paresthesias was greater in group 2. Pain relief was complete in 75% and 80% of the patients in groups 1 and 2, respectively (NS); three patients in group 1 and one in group 2 had unblocked segments (NS). CONCLUSIONS: Our results support the contention that the catheter should be directed cephalad during insertion for continuous epidural anesthesia.

Should supraclavicular brachial plexus block be avoided in pregnancy?

Unilateral phrenic nerve block is common after supraclavicular brachial plexus block techniques, although it is rarely symptomatic in patients without respiratory disease. A 24-weeks-pregnant woman was scheduled for a carpal tunnel release because of intractable pain. After a perivascular subclavian brachial plexus block with 30 ml of 0.33% plain bupivacaine was performed, the patient developed a right phrenic nerve block manifested by acute dyspnea and cough. No deleterious consequences followed, but surgery was canceled. Respiratory changes produced by pregnancy might compromise ventilatory reserve. Thus, we suggest avoiding supraclavicular approaches to brachial plexus block in pregnant women, since they may be as prone to developing respiratory embarrassment, secondary to phrenic block, as patients with pulmonary pathology.

Benzodiazepine premedication causes hypoxemia during spinal anesthesia in geriatric patients.

BACKGROUND AND OBJECTIVES: The use of sedatives during regional anesthesia can lead to life-threatening hypoxemia. Older patients particularly are prone to enhanced effects of these drugs. We studies whether oral premedication with benzodiazepines produced hypoxemia during spinal anesthesia in elderly patients. METHODS: In a prospective, double-blind, and randomized study, we evaluated the effect of oral benzodiazepine premedication on the incidence of hypoxemia measured by pulse oximetry (arterial oxygen saturation less than 90% for 30 seconds or longer) during surgery under spinal anesthesia in 80 geriatric patients divided into four equal groups: 1, control, no premedication; 2, 1 mg flunitrazepam; 3, 1 mg lorazepam; and 4, 7.5 mg midazolam. RESULTS: The incidence of hypoxemia in the four groups was: 1, 15%; 2, 45%; 3, 20%; and 4, 60% (p = 0.0078); overall incidence was 42% in premedicated patients versus 15% in unpremedicated controls (p = 0.0304). Seventy-four percent of patients who presented drowsiness and anesthetic level above T7 had desaturation compared to only 7% of those who were awake and had lower level (p less than 0.0005). No association between hypoxemia and other factors (age, weight, ASA physical status, and position during surgery) was found. All the episodes of desaturation were easily corrected with low supplemental oxygen concentrations. CONCLUSIONS: Premedication with oral benzodiazepines may produce hypoxemia during spinal anesthesia in elderly patients. Lorazepam appeared safer than flunitrazepam and midazolam. Monitoring of arterial blood oxygen saturation and/or supplemental oxygen is mandatory in geriatric patients with high spinal anesthetic level and/or drowsiness during surgery.

Trigeminal nerve block as a complication of epidural anesthesia.

BACKGROUND AND METHODS: A healthy pregnant woman underwent labor under successful epidural analgesia with a total drug mass of 100 mg plain bupivacaine plus 100 micrograms fentanyl in three doses given over 150 minutes. RESULTS: Ninety minutes after the last dose, she developed signs and symptoms of a left trigeminal nerve block along with an ipsilateral Horner's syndrome. The cutaneous anesthesia level reached C6 on the left and T6 on the right side. Neurologic symptoms disappeared four hours later. CONCLUSION: An excessive upward epidural extension of bupivacaine block, reaching the trigeminal spinal nucleus and/or tract in the cervical spinal cord, is postulated.

Preoperative percutaneous ilioinguinal and iliohypogastric nerve block with 0.5% bupivacaine for post-herniorrhaphy pain management in adults.

The safety, effectiveness and duration of a percutaneous ilioinguinal-iliohypogastric nerve block with 10 ml 0.5% bupivacaine, as a method for postoperative analgesia, were studied prospectively in adult patients undergoing unilateral inguinal herniorrhaphy under spinal anesthesia. Group I (n = 20) blocked patients were compared with Group II (n = 25), non-blocked control patients. A blinded observer assessed pain scores and analgesic requirements after surgery. Group I patients had less pain at 3, 6, 24 and 48 hours after surgery and also required less analgesics during the first two postoperative days. This technique appears to be a simple and safe method for providing effective and long-lasting postoperative analgesia following inguinal hernia repair in adults.