Cardiomyoplasty--current status

Dynamic cardiomyoplasty is a new surgical technique that uses transformed (electrostimulated) skeletal muscle to reinforce or replace damaged myocardium. The clinical benefits of cardiomyoplasty have not been as dramatic as its evolution. However, with the limitations of cardiac transplantation and with further developments in cardiomyoplasty, this technique is likely to be established as a viable alternative in selected patients with refractory cardiac failure. Basic research and animal studies suggest that there could be a possible role of cardiomyoplasty in certain pediatric cardiac disorders.

A pharmacokinetic study of phenylcyclohexyldiethylamine. An analog of phencyclidine

The pharmacokinetics of three phencyclidine analogs--phenylcyclohexyl-diethylamine (PCDE), phenylcyclohexylethylamine (PCE), and phenylcyclohexylamine (PCA)--were determined in rats after intravenous administration of each drug. Because PCE and PCA are major metabolites of PCDE, their plasma levels were also measured after administration of PCDE. Similarly, PCA concentrations was determined after administration of PCE. The data were combined and analyzed by nonlinear regression procedures using compartmental and noncompartmental models to determine the kinetic parameters of PCDE metabolism. The object was to estimate the kinetic constants for the metabolic sequence, PCDE to PCE to PCA. A 6-compartment model (two pools for each analyte) that included saturable components for the conversion of PCDE to PCE and PCE to PCA gave the best fit to the combined data. Despite large uncertainties for some microparameters, useful estimates were obtained for clearances, distribution volumes, and fraction of PCDE or PCE converted to PCE and PCA in vivo under nonsaturating conditions. The estimated fraction of PCDE converted to PCA and the apparent Km value for the conversion of PCDE to PCE were comparable to values obtained in vitro with microsomal preparations, suggesting that metabolic studies in vitro provide reasonable predictors of the biotransformation process in vivo for this class of compounds.

A comparative study of 0.25% ropivacaine and 0.25% bupivacaine for brachial plexus block

The present study compares the effectiveness of 0.25% ropivacaine and 0.25% bupivacaine in 44 patients receiving a subclavian perivascular brachial plexus block for upper extremity surgery. The patients were assigned to two equal groups in this randomized, double-blind study; one group received ropivacaine 0.25% (112.5 mg) and the other, bupivacaine 0.25% (112.5 mg), both without epinephrine. Onset times for analgesia and anesthesia in each of the C-5 through T-1 brachial plexus dermatomes did not differ significantly between the two groups. The mean onset time for analgesia ranged from 11.2 to 20.2 min, and the mean onset time for anesthesia ranged from 23.3 to 48.2 min. The onset of motor block differed only with respect to paresis in the hand, with bupivacaine demonstrating a shorter onset time than ropivacaine. The duration of sensory and motor block also was not significantly different between the two groups. The mean duration of analgesia ranged from 9.2 to 13.0 h, and the mean duration of anesthesia ranged from 5.0 to 10.2 h. Both groups required supplementation with peripheral nerve blocks or general anesthesia in a large number of cases, with 9 of the 22 patients in the bupivacaine group and 8 of the 22 patients in the ropivacaine group requiring supplementation to allow surgery to begin. In view of the frequent need for supplementation noted with both 0.25% ropivacaine and 0.25% bupivacaine, we do not recommend using the 0.25% concentrations of these local anesthetics to provide brachial plexus block.

Intrapulmonary placement of a pleural catheter

OBJECTIVE AND CONCLUSION. A case of intrapulmonary placement of a pleural catheter is described that was likely due to the presence of focal pleural thickening at the site of catheter insertion.

Does the sympathetic block outlast sensory block: a thermographic evaluation

A study to evaluate the duration of sympathetic and sensory block in the L2 and L5 dermatome distributions using thermography and pinprick was conducted. Twenty patients received epidural block using 2% lidocaine with epinephrine. Onset and duration of the sensory and sympathetic blocks were determined and compared statistically. There was no difference between the duration of sensory and sympathetic block over the L2 dermatome, but sympathetic block was significantly longer than sensory block in the L5 dermatome. This study demonstrates that the duration of sympathetic block can be either longer or shorter than sensory block in L2 and L5 dermatomes. This has important implications for interpretation of results of differential epidural studies in that one cannot predict the duration of sympathetic block based on duration of sensory block.

A comparison of ropivacaine 0.5% and bupivacaine 0.5% for brachial plexus block

This study compared the effectiveness of 0.5% ropivacaine and 0.5% bupivacaine for brachial plexus block. Forty-eight patients received a subclavian perivascular brachial plexus block for upper-extremity surgery. One group (n = 24) received ropivacaine 0.5% (175 mg) and a second group (n = 24) received bupivacaine 0.5% (175 mg), both without epinephrine. Onset times for analgesia and anesthesia in each of the C5 through T1 brachial plexus dermatomes did not differ significantly between groups. Duration of analgesia and anesthesia was long (mean duration of analgesia, 13-14 h; mean duration of anesthesia, 9-11 h) and also did not differ significantly between groups. Motor block was profound, with shoulder paralysis as well as hand paresis developing in all of the patients in both groups. Two patients in each group required supplemental blocks before surgery. Ropivacaine 0.5% and bupivacaine 0.5% appeared equally effective in providing brachial plexus anesthesia.

Intravenous regional sympatholysis: a double-blind comparison of guanethidine, reserpine, and normal saline

This double-blind, randomized study was designed to compare the effectiveness of intravenous regional sympatholysis using guanethidine, reserpine and normal saline. Twenty-one patients with reflex sympathetic dystrophy of an upper or lower extremity were enrolled and received intravenous regional blockade (IVRB) with one of the three medications. There was significant pain relief in all three groups at 30 min. There were no significant differences among the three groups in the degree of pain relief, the number of patients obtaining pain relief in the 30 min after the block, or the number of patients reporting more than 50% pain relief for more than 24 hr. The saline group's high rate of pain relief could be partially due to a mechanism of tourniquet-induced analgesia.

Plasma concentrations of ropivacaine given with or without epinephrine for brachial plexus block

The purpose of this study was to determine the pharmacokinetic properties of the local anaesthetic ropivacaine used with or without epinephrine for brachial plexus block. Seventeen ASA physical status I or II adult patients undergoing elective orthopaedic surgery received a single injection of 33 ml ropivacaine for subclavian perivascular block and 5 ml to block the intercostobrachial nerve in the axilla. One group (n = 8) received 0.5 per cent ropivacaine without epinephrine (190 mg) and the other (n = 9) received 0.5 per cent ropivacaine with epinephrine 1:200,000 (190 mg). Plasma ropivacaine concentrations were measured from peripheral venous blood samples taken for 12 hr after drug administration. Ropivacaine base was determined in plasma using gas chromatography and a nitrogen-sensitive detector. The mean peak plasma concentration (Cmax) was 1.6 +/- 0.6 mg.L-1 and 1.3 +/- 0.4 mg.L-1 after administration of ropivacaine with and without epinephrine. The median time to peak plasma concentration (tmax) was 0.75 hr and 0.88 hr and the mean area under the plasma concentration curve AUC0-12h was 7.7 +/- 3.6 and 7.0 +/- 3.4 mg.l hr-1. The differences were not statistically significant. The terminal phase of the individual plasma concentration-time curves showed a varying and sometimes slow decline possibly indicating a sustained systemic uptake of ropivacaine from the brachial plexus. No central nervous system or cardiovascular symptoms attributed to systemic plasma concentrations of the drug were observed, with the dose (1.90-3.28 mg.kg-1) of ropivacaine used. It is concluded that the addition of epinephrine does not alter the pharmacokinetic properties of ropivacaine when used for subclavian perivascular brachial plexus block.

Brachial plexus block with a new local anaesthetic: 0.5 per cent ropivacaine

A new local anaesthetic, ropivacaine hydrochloride, was used in a concentration of 0.5 per cent in 32 patients receiving a subclavian perivascular block for upper extremity surgery. One group (n = 15) received 0.5 per cent ropivacaine without epinephrine and a second group (n = 17) received 0.5 per cent ropivacaine with epinephrine in a concentration of 1:200,000. Anaesthesia was achieved in 87 per cent of the patients in both groups in all of the C5 through T1 brachial plexus dermatomes. Motor block was profound with 100 per cent of patients in both groups developing paresis at both the shoulder and hand and 100 per cent developing paralysis at the shoulder. There was a rapid initial onset of sensory block (a mean of less than four minutes for analgesia) with a prolonged duration (a mean of greater than 13 hr of analgesia). The addition of epinephrine did not significantly affect the quality or onset of sensory or motor block. The duration of sensory block was reduced by epinephrine at T1 for analgesia and at C7, C8, and T1 for anaesthesia. The duration of sensory block in the remaining brachial plexus dermatomes as well as the duration of motor block was not effected by epinephrine. There was no evidence of cardiovascular or central nervous system toxicity in either group with a mean dose of 2.5-2.6 mg.kg-1 ropivacaine.

Iatrogenic femoral arteriovenous fistula

Twelve iatrogenic femoral arteriovenous fistulas are reported, 11 of which arose from the superficial or deep femoral arteries. All but two occurred in association with cardiac angiographic procedures. It appears that the femoral crease was used as a landmark to establish the cutaneous entry point for vascular puncture and resulted in an excessively distal puncture site. The femoral crease is an unreliable landmark in many patients. This complication may be minimized by using physical examination to identify the level of the inguinal ligament or fluoroscopy to localize the distal half of the femoral head.

Transarterial techniques are not effective for subclavian perivascular block

Although transarterial techniques have been commonly used for axillary block, results with these techniques have not been previously described for subclavian perivascular block. We studied the efficacy and complications of two types of arterial techniques for subclavian perivascular block. In Group 1 (n = 10), the subclavian perivascular injection was made after withdrawing the needle from the subclavian artery (top of artery), and in Group 2 (n = 8), the injection was made after advancing through the subclavian artery (bottom of artery). The local anesthetic used was lidocaine 1.5% with epinephrine 1:200,000 in a volume determined by the formula [ml = (height in inches divided by 2) + 5]. Both techniques were associated with a low incidence (50% or less) of anesthesia throughout the brachial plexus dermatomes. Sixty percent of patients in Group 1 and 63% of patients in Group 2 required supplemental blocks. In view of the low incidence of anesthesia and the frequent need for supplementation, additional patients were not enrolled in the study. Complications associated with the technique included hematoma (12-20%), recurrent laryngeal nerve block (10-25%), Horner's syndrome (0-20%) and phrenic nerve block (75-80%). Despite the relatively high dose of lidocaine used, serum lidocaine levels remained well below the toxic range.

Identification of the anterior psoas sheath as a landmark for lumbar sympathetic block

This clinical report demonstrates that identification of the psoas muscle via contrast media injection under fluoroscopy and the subsequent tenting and puncture of the psoas fascia with a 6-inch 22-gauge needle is a definite aid in the correct placement of the needle for lumbar sympathetic block. In ten patients in whom this technique was used, the needle position was subsequently proven to be correctly placed in all cases. The authors conclude that this method is a valuable adjunct in fluoroscopy-guided lumbar sympathetic block.

Lidocaine hydrocarbonate is not superior to lidocaine hydrochloride in interscalene brachial plexus block

To determine the effect of carbonation of lidocaine, a comparison of 1.0% lidocaine hydrochloride (HCl) and 1.1% lidocaine hydrocarbonate (CO2), both with 1:200,000 epinephrine, was made in this study of 50 patients receiving interscalene brachial plexus blocks. Sensory block was determined by the response to pinprick in the C2-T2 dermatomes, while motor block was assessed by the development of paresis and paralysis at the shoulder and hand. The percentage of patients developing analgesia (decreased sensation to pinprick) and anesthesia (total absence of sensation to pinprick) at each dermatome level as well as the percentage of patients developing motor block was not significantly different between the two forms of lidocaine. The initial onset of analgesia [lidocaine HCl, 4.0 +/- 2.4 (SD) minutes; lidocaine CO2, 4.3 +/- 3.8 (SD) minutes] and anesthesia [lidocaine HCl, 10.1 +/- 5.7 (SD) minutes; lidocaine CO2, 7.8 +/- 4.4 (SD) minutes] did not differ significantly between the two groups. At the individual dermatomes, there was no difference in the onset of analgesia except at one dermatome level, C7, which was near the level of local anesthetic injection. Anesthesia onset in each dermatome as well as the onset of motor block did not differ between the two groups. It is concluded that lidocaine CO2 does not offer any significant clinical advantage over lidocaine HCl in interscalene brachial plexus block.

A controlled trial of transcutaneous electrical nerve stimulation (TENS) and exercise for chronic low back pain

A number of treatments are widely prescribed for chronic back pain, but few have been rigorously evaluated. We examined the effectiveness of transcutaneous electrical nerve stimulation (TENS), a program of stretching exercises, or a combination of both for low back pain. Patients with chronic low back pain (median duration, 4.1 years) were randomly assigned to receive daily treatment with TENS (n = 36), sham TENS (n = 36), TENS plus a program of exercises (n = 37), or sham TENS plus exercises (n = 36). After one month no clinically or statistically significant treatment effect of TENS was found on any of 11 indicators of outcome measuring pain, function, and back flexion; there was no interactive effect of TENS with exercise. Overall improvement in pain indicators was 47 percent with TENS and 42 percent with sham TENS (P not significant). The 95 percent confidence intervals for group differences excluded a major clinical benefit of TENS for most outcomes. By contrast, after one month patients in the exercise groups had significant improvement in self-rated pain scores, reduction in the frequency of pain, and greater levels of activity as compared with patients in the groups that did not exercise. The mean reported improvement in pain scores was 52 percent in the exercise groups and 37 percent in the nonexercise groups (P = 0.02). Two months after the active intervention, however, most patients had discontinued the exercises, and the initial improvements were gone. We conclude that for patients with chronic low back pain, treatment with TENS is no more effective than treatment with a placebo, and TENS adds no apparent benefit to that of exercise alone.

Can trials of physical treatments be blinded? The example of transcutaneous electrical nerve stimulation for chronic pain

Therapeutic trials often attempt to "blind" patient and investigator to the true nature of treatments received, reducing the influences of conscious or subconscious prejudices. In drug trials, this is accomplished with placebo tablets, but blinding in trials of physical treatments is more problematic. This issue arose in a clinical trial of transcutaneous electrical nerve stimulation (TENS) for patients with chronic low back pain. Several study design features were incorporated to promote blinding: use of sham TENS units visually identical with real units, exclusion of potential subjects with previous TENS experience, avoidance of a crossover design and use of identical visit frequency, instructions and modifications in electrode placement. Subjects were asked not to discuss treatments with the clinicians who performed outcome assessments. Both patients and clinicians were asked to guess actual treatment assignments at the trial's end. Every patient in the true TENS group believed the unit was functioning properly, but the degree of certainty varied. In the sham TENS group, 84% also believed they had functioning units, but their certainty was significantly less than in the active treatment group. Differences in patient perceptions did not affect compliance, as the two groups had similar dropout rates, appointment compliance, days of TENS use and daily duration of TENS use. Clinicians guessed treatments correctly 61% of the time (as opposed to 50% expected by chance), again suggesting partial success in blinding. These efforts at blinding may partly explain the negative trial results for TENS efficacy. We conclude that complete blinding is difficult to achieve because of sensory difference in treatment and unintended communication between patient and examiner.(ABSTRACT TRUNCATED AT 250 WORDS)

Subarachnoid and epidural calcitonin in patients with pain due to metastatic cancer

Nine patients with metastatic cancer who had pain refractory to traditional treatments received a subarachnoid injection of salmon calcitonin. Eight of the nine patients reported pain relief after subarachnoid injection varying from 1 hr to 5 days. Four of the responding patients subsequently received an epidural injection of salmon calcitonin, and two of these patients reported pain relief. Although many patients experienced pain relief, nausea and vomiting appeared to be a significant side effect, occurring in seven out of nine patients.

Diagnostic epidural opioid technique

Diagnostic epidural blocks were performed on 27 chronic pain patients sequentially using saline, fentanyl, and lidocaine solution. The patients were divided into one of four groups based on their response to the epidural solutions: placebo response group--pain relief with placebo solutions; fentanyl response group--pain relief with epidural fentanyl; lidocaine response group (LRG)--pain relief with lidocaine but not fentanyl; and no response group--no pain relief with any of the solutions used. The four groups were compared on the basis of age, sex, site of pain, duration of pain, narcotic use, pain assessment index, and workmen's compensation claims. The comparisons resulted in the conclusion that LRG patients had a much longer average duration of pain than the other groups. On the basis of the information gathered, it was theorized that, despite their response to epidural lidocaine, LRG patients may actually be a group of operant pain patients. Their failure to receive analgesia from epidural fentanyl may be a learned response such that they associate any sensory input from the affected area as painful. If follow-up studies support these findings, then the diagnostic opioid technique may be a more sensitive tool in diagnosing chronic pain.

The premotor potential

A small waveform precedes the compound muscle action potential evoked from the thenar eminence with median nerve stimulation with high amplifier gains. This potential is believed to emanate from fibers destined to innervate the volar aspect of the first digit. It has been suggested recently that the source of the premotor potential is the palmar cutaneous branch of the median nerve. In this study, the palmar cutaneous branch of the median nerve was blocked at the wrist. A localized zone of anesthesia was observed over the proximal midpalm, not the thenar eminence, and the premotor response remained unchanged as did a midpalmar potential. The median nerve was then blocked at the base of the thenar eminence; only then did the premotor potential disappear. The palmar cutaneous branch of the median nerve innervates only a small portion of the medial aspect of the thenar eminence and does not produce the thenar premotor potential. Additionally, because of the close proximity of the main median nerve to its palmar cutaneous branch, volume conduction of stimuli and responses precludes an electrophysiologic technique which exclusively localizes the palmar cutaneous branch of the median nerve.