Antoun Nader

A comparison of epidural tramadol and epidural morphine for postoperative analgesia

The present study compared epidural tramadol with epidural morphine for postoperative analgesia in 20 patients undergoing major abdominal surgery. Intraoperatively, the patients were anaesthetized by a balanced technique of general anaesthesia combined with lumbar epidural lidocaine. In ten of the patients 100 mg tramadol diluted in 10 ml normal saline was also injected epidurally, while 4 mg epidural morphine was used in the other ten patients. In all patients, the visual analogue pain score, PaO2, PaCO2 and respiratory rate were monitored every hour for the first 24 hr postoperatively. In both the tramadol and morphine groups, the mean hourly pain scores ranged from 0.2 ± 0.6 to 1.4 ± 2.5 throughout the period of observations. However, the mean PaO2 was decreased postoperatively in the epidural morphine group, while no change was observed in the epidural tramadol group. The maximal decrease of PaO2 in the epidural morphine group was observed at the tenth hour postoperatively, when it decreased to 72.8 ± 10.3 mm Hg. This was not associated with any increase in PaCO2 or a decrease of respiratory rate, suggesting that hypoxaemia rather than hypercarbia or decreased respiratory rate may be an earlier indicator of respiratory depression in patients breathing room air without oxygen supplementation. The absence of clinically relevant respiratory depression following epidural tramadol compared with epidural morphine may be attributed to the different mechanisms of their analgesic action. The results suggest that epidural tramadol can be used to provide prolonged postoperative analgesia without serious side effects.RésuméCette étude compare le tramadol à la morphine donnée par voie épidurale pour l’analgésie postopératoire de 20 patients subissant une chirurgie abdominale majeure. Les patients sont anesthésiés par une technique balancée, combinée à une épidurale lombaire à la lidocaïne. Chez dix des patients, tramadol 100 mg dilué de 10 ml de liquide physiologique est également injecté par voie épidurale, tandis que morphine épidurale 4 mg est injectée aux autres patients. Chez tous les patients, une échelle visuelle analogue de la douleur, la PaO2, la PaCO2 et la fréquence respiratoire sont mesurées chaque heure pendant les 24 premières heures postopératoires. Autant dans le groupe tramadol que dans le groupe morphine, la valeur moyenne de l’évaluation de la douleur se situé de 0,2 ± 0,6 à 1,4 ± 2,5 pendant toute la période d’observation. La PaO2 moyenne est cependant diminuée en postopératoire dans le groupe épidurale à la morphine tandis qu’aucun changement n’est observé dans le groupe épidurale au tramadol. La diminution maximum de la PaO2 dans le groupe épidurale à la morphine se situe à la dixième heure postopératoire, et atteint une valeur de 72,8 ± 10,3 mm Hg. Elle n’est associée à aucune augmentation de PaCO2 ni à une diminution de fréquence respiratoire, suggérant que l’hypoxémie plutôt que l’hypercapnie vu la diminution de fréquence respiratoire peut être un indice précoce de la dépression respiratoire chez des patients respirant l’air ambiant sans supplément d’oxygène. L’absence de dépression respiratoire cliniquement significative après une épidurale au tramadol par rapport à une épidurale à la morphine peut être attribuée à un mécanisme d’action analgésique différent. Ces résultats suggèrent qu’une épidurale au tramadol peut être utilisée pour procurer une analgésie post-opératoire prolongée sans effets secondaires sérieux.

Neurologic sequelae after interscalene brachial plexus block for shoulder/upper arm surgery: The association of patient, anesthetic, and surgical factors to the incidence and clinical course

We determined the incidence, distribution, and resolution of neurologic sequelae and the association with anesthetic, surgical, and patient factors after single-injection interscalene block (ISB) using levobupivacaine 0.625% with epinephrine 1:200,000 in subjects undergoing shoulder or upper arm surgery, or both, in 693 consecutive adult patients. After a standardized ISB, assessments were made at 24 and 48 h and at 2 and 4 wk for anesthesia, hypesthesia, paresthesias, pain/dysesthesias, and motor weakness. Symptomatic patients were monitored until resolution. Subjects reporting pain or discomfort >3 of 10 and those with motor or extending sensory symptoms received diagnostic assessment. Six-hundred-sixty subjects completed 4 wk of follow-up. Fifty-eight neurologic sequelae were reported by 56 subjects. Symptoms were sensory except for two cases of motor weakness (lesions identified distant from the ISB site). Thirty-one sequelae with likely ISB association were reported by 29 subjects, including 14 at the ISB site, 9 at the distal phalanx of thumb/index finger, 7 involving the posterior auricular nerve, and 1 clinical brachial plexopathy. Sequelae not likely associated with the ISB were reported by 27 subjects with symptoms reported in the median (n = 9) and ulnar (n = 4) nerves, surgical neuropraxias (n = 12), and motor weakness (n = 2). Symptoms resolved spontaneously (median 4 wk; range, 2–16 wk) except in the two patients with motor weaknesses and the patient with clinical brachial plexopathy, who received therapeutic interventions. Variables identified as independent predictors of neurologic sequelae likely related to ISB were paresthesia at needle insertion and ISB site pain or bruising at 24 h. In contrast, surgery preformed in the sitting position, as well as ISB site bruising, was identified as a predictor of neurologic sequelae not likely related to ISB. In conclusion, neurologic sequelae after single-injection ISB using epinephrine mainly involve transient minor sensory symptoms.

Nerve stimulator-assisted evoked motor response predicts the latency and success of a single-injection sciatic block.

Variable onset latency of single-injection sciatic nerve block (SNB) may result from drug deposition insufficiently close to all components of the nerve. We hypothesized that this variability is caused by the needle tip position relative to neural components, which is objectified by the type of evoked motor response (EMR) elicited before local anesthetic injection. One-hundred ASA I–II patients undergoing reconstructive ankle surgery received infraglutealparabiceps SNB using 0.4 mL/kg (maximum 35 mL) of levobupivacaine 0.625%. The endpoint for injection was the first elicited EMR: inversion (I), plantar flexion (PF), dorsiflexion (DF), or eversion (E) at 0.2–0.4 mA. The frequencies of the EMRs were: I 40%, PF 43%, E 14%, and DF 3%. SNB was considered complete if both tibial and common peroneal nerves were blocked and failed if either analgesia to pinprick was not observed at 30 min or anesthesia at 60 min. Patients with an EMR of I demonstrated shorter mean times (±95% confidence interval [CI]) to complete the block with 8.5 (95% CI, 6.2–10.8) min compared to 27.0 (95% CI, 20.6–33.4) min after PF (P < 0.001) and 30.4 (95% CI, 24.9–35.8) min after E (P < 0.001). No rescue blocks were required in group I compared with 24% (P = 0.001) and 71% (P < 0.001) of patients in groups PF and E, respectively. We conclude that EMR type during nerve stimulator-assisted single-injection SNB predicts latency and success of complete SNB because the observed EMR is related to the positioning of the needle tip relative to the tibial and common peroneal nerves.

Nerve Block of the Infrapatellar Branch of the Saphenous Nerve in Knee Arthroscopy A Prospective, Double-Blinded, Randomized, Placebo-Controlled Trial

BACKGROUND With the rising use of outpatient knee arthroscopy over the past decade, interest in peripheral nerve blocks during arthroscopy has increased. Femoral nerve blocks are effective but are associated with an inherent risk of the patient falling postoperatively because of quadriceps weakness. We studied blocks of the infrapatellar branch of the saphenous nerve, which produce analgesia in the knee that is similar to that resulting from a femoral nerve block but without associated quadriceps weakness. METHODS Thirty-four patients were enrolled into each arm of this prospective, randomized, double-blinded trial comparing 10 mL of 0.25% bupivacaine used as a block of the infrapatellar branch of the saphenous nerve with a placebo during simple knee arthroscopy. Immediate outcome measures included Numeric Rating Scale (NRS) pain scores (0 to 10 points), mobility and discharge times, opioid usage, subjective adverse side effects, and forty-eight-hour anesthesia recovery surveys. Short-term measures included one-week and twelve-week Lysholm knee scores. RESULTS No adverse effects or increased quadriceps weakness were observed following use of the nerve block. Improvement in early NRS scores and subjective nausea (p = 0.03) were detected. Patients for whom the block was successful also had improved twelve-week Lysholm knee scores (p = 0.04). No differences in opioid usage, mobility time, forty-eight-hour anesthesia recovery scores, or one-week Lysholm knee scores were found. CONCLUSIONS No significant adverse effect or disadvantage was identified for blocks of the infrapatellar branch of the saphenous nerve used in simple knee arthroscopy. In addition to decreased early NRS scores and nausea, blocks of the infrapatellar branch of the saphenous nerve demonstrated potential benefit at twelve weeks after simple knee arthroscopy.

Factor VII levels and international normalized ratios in the early phase of warfarin therapy.

Background:Factor VII is the most affected clotting factor during the early phase of warfarin therapy. An international normalized ratio (INR) of more than 1.4 is considered unsafe for epidural catheter placement or removal, according to the American Society of Regional Anesthesia and Pain Medicine. The authors tested the hypothesis that factor VII activities would be consistent with safe removal of the epidural catheter on postoperative day (POD) 1 regardless of INR value. Methods:Data from 121 patients who took warfarin after undergoing total joint surgery and had INRs and factor VII levels determined were reviewed. Patient characteristics and factor VII activities were compared between patients with INRs of more than 1.4 and those with INRs less than or equal to 1.4 on PODs 1, 2, and 3. Results:Eleven patients had INRs of more than 1.4 on POD 1; their mean ± SD factor VII activities were 60 ± 28% (normal: 50–160%). On POD 2, 78 patients with INRs more than of 1.4 had factor VII activities of 32 ± 15%, whereas on POD 3, 84 patients with INRs of more than 1.4 had factor VII activities of 44 ± 19%. Variables included in the final multiple logistic regression model as predictors of an INR of more than 1.4 on POD 2 were warfarin dose on POD 1 and factor VII activity on POD 2. Conclusions:The range of factor VII activities in the patients with INRs of more than 1.4 within 12 h of warfarin therapy was compatible with adequate hemostasis. The authors found no evidence that epidural catheters should not be removed even with INRs up to 1.9, the highest INR on POD 1 noted in their study.

Intravascular administration of polymerized gelatin versus isotonic saline for prevention of spinal-induced hypotension.

This report tests the hypothesis that intravascular prehydration with 3% gelatin in electrolyte solution maintains arterial blood pressure after spinal anesthesia better than with an equal volume of isotonic saline solution. Thirty‐four patients undergoing elective transurethral resection of the prostate were allocated randomly to receive either 7 mL/kg of isotonic saline 0.9% (17 patients) or 7 mL/kg of 3% gelatin in electrolyte solution (17 patients) before spinal anesthesia. There was a significant increase in central venous pressure in the gelatin group without any significant change in the isotonic saline group. After spinal anesthesia, the mean systolic blood pressure significantly decreased in both groups; however, the incidence of systolic blood pressure greater than 75% of control value was higher in the gelatin group (15/17) than in the normal saline group (9/17). Also, the mean dose of phenylephrine required to maintain arterial blood pressure >75% of the baseline value was significantly larger in the normal saline group than in the gelatin group. We conclude that prophylactic administration of gelatin is more effective than saline in attenuating spinal anesthesia‐induced hypotension.

Glycine receptor antagonism: Effects of ACEA-1021 on the minimum alveolar concentration for halothane in the rat

Background Glycine and glutamate binding sites are allosterically coupled at the N-methyl-n-aspartate (NMDA) receptor complex. Previous studies have shown that antagonism of glutamate at the NMDA receptor reduces the minimum alveolar concentration (MAC) for volatile anesthetics. 5-Nitro-6, 7-dichloro-2, 3-quinoxalinedione (ACEA-1021) is a competitive antagonist at the glycine recognition site of the NMDA receptor. The purpose of this study was to determine whether glycine receptor antagonism also reduces volatile anesthetic requirements in the rat. Methods In experiment 1, Sprague-Dawley rats were anesthetized with halothane in 50% Oxygen2 -balance Nitrogen2 and their lungs mechanically ventilated. They were randomly assigned to one of three groups according to the dose of ACEA-1021 administered (0, 20, or 40 mg/kg intravenously; n = 6). The bolus dose of ACEA-1021 was followed by a continuous intravenous infusion of vehicle or ACEA-1021 at 14 mg *symbol* kg sup -1 *symbol* h sup -1. Halothane MAC was then determined by the tail-clamp method. In experiment 2, awake rats were randomly assigned to groups according to the same dosages of ACEA-1021 as in experiment 1. Arterial CO2 tension and mean arterial pressure were recorded before and 5 and 30 min after the start of the infusion. The infusion was then stopped, and the time to recovery of the righting reflex was recorded. Results In experiment 1, ACEA-1021 decreased halothane MAC (mean + SD) in a dose-dependent manner (control, 0.95 plus/minus 0.15 vol%; ACEA-1021 20 mg/kg, 0.50 plus/minus 0.14 vol%; ACEA-1021 40 mg/kg, 0.14 plus/minus 0.16 vol%; P < 0.01). In experiment 2, arterial CO2 tension was increased by ACEA-1021 (control, 38 plus/minus 3 mmHg; ACEA-1021 20 mg/kg, 43 plus/minus 3 mmHg; ACEA-1021 40 mg/kg, 48 plus/minus 2 mmHg; P < 0.01). Mean arterial pressure was not affected by any dose of ACEA-1021. The righting reflex was abolished in rats receiving ACEA-1021 40 mg/kg only and recovered 30 plus/minus 7 min after discontinuation of the infusion. Conclusions Halothane MAC reduction by glycine receptor antagonism was greater than that previously observed for antagonism of glutamate at the NMDA or AMPA receptor. In rats receiving ACEA-1021 only, minimal hemodynamic depression and moderate hypoventilation were observed. Antagonism of glycine at the NMDA receptor recognition site offers a potential mechanism of action of anesthesia.

Santayana's prophecy fulfilled

In most training programs today there is little interest in and little attention paid to the history of anesthesia, to the individuals who shaped the specialty of anesthesiology, to the techniques that allowed surgical (and obstetrical) horizons to expand, and to the agents that allowed anesthesia to become progressively less dangerous. Even such catastrophies as the deaths due to the use of pentothal in treating those injured in the bombing of Pearl Harbor1 or the paralyses of Wooley and Roe by spinal anesthesia2 tend to be forgotten as the problems causing them are resolved, despite the fact that their very occurrences provided lessons that should be remembered rather than forgotten. Such are the cases of neurotoxicity reported after the unintentional intrathecal injection of 2-chloroprocaine in the early 1980s. They represent a serious problem that arose over 20 years ago; but once resolved, the problem and its solution have already been forgotten. As a result, anesthesiologists unaware of the past “are condemned to repeat it”; but in medicine, it is the patients who will suffer from their physicians’ failure to remember. In 1952, 2-chloroprocaine, an analog of procaine, was introduced by Foldes and McNall,3 who showed that the simple substitution of a chlorine atom on the second carbon (in the ortho position) of the benzene ring of procaine results in more rapid enzymatic hydrolysis and, hence, decreased toxicity.4 Foldes and McNall3 believed that this simple change provided anesthesiologists with an agent having many of the characteristics of “the ideal local anesthetic,” namely, rapid onset of action, increased potency (21⁄2 times that of procaine), decreased neural and systemic toxicity (half that of procaine), and an adequate duration of action (twice that of procaine) that could be increased significantly by the addition of epinephrine. Because of the rapid onset, potency, and safety of this new agent, anesthesiologists quickly began to use the drug clinically, especially for epidural anesthesia. During the next decade, several large series of cases were reported attesting to the efficacy and safety of Nesacaine, as the commercial preparation became known (then manufactured by Maltbie Laboratories, a division of Wallace & Tiernan, Belleville, NJ), for both major abdominal surgery5 and obstetrics.6 Interestingly, Colavincenzo et al.7 demonstrated the usefulness of such a short-acting agent for outpatient anesthesia, an asset that would be rediscovered over 30 years later.8,9 However, while 2-chloroprocaine was used for all types of surgical procedures, the characteristics of the drug were so well suited to the anesthetic requirements of the pregnant woman and her fetus, it was for obstetrical anesthesia that the drug was most widely used, with a special preparation for epidural anesthesia (without methylparaben) designated as Nesacaine-CE (Strasenburg Laboratories, Rochester, NY). As Gissen et al.10 pointed out, “It is rapid in onset, has the lowest potential for toxicity, and is the most rapidly hydrolyzed of all the local anesthetics. The fetal circulation is exposed to the lowest concentrations of 2CP because of rapid drug hydrolysis, which minimizes the possibility of fetal drug depression. Finally, the metabolic products of 2CP hydrolysis are nontoxic both to the maternal and fetal organism.” Then, in 1980, after nearly 30 years of clinical use, two reports of persistent neurological deficit after epidural Nesacaine-CE appeared in the literature,11,12 followed by an additional report 2 years later.13 These articles reported a total of 8 patients, *Santayana G. The Life of Reason: Reason in Common Science. New York, NY: Scribner; 1903.

A dose-ranging study of 0.5% bupivacaine or ropivacaine on the success and duration of the ultrasound-guided, nerve-stimulator-assisted sciatic nerve block: a double-blind, randomized clinical trial.

Background and Objectives Before bifurcation, the sciatic nerve is composed of 2 component nerves encased in a common investing extraneural layer (CIEL). We examined the effect of various volumes injected beneath the CIEL on the success and duration of sciatic nerve block. Methods Ultrasound-guided nerve-stimulator–assisted sciatic nerve blocks were performed on 142 subjects. Subjects were randomized into 14 groups (0.5% ropivacaine or bupivacaine) with epinephrine 1:300,000 in volumes ranging from 2.5 to 30 mL. Successful block was defined as a complete sensory and motor block at 60 minutes. The minimum threshold current, time to complete block, duration of sensory and motor block, postoperative pain, and analgesic requirements were recorded. Results The mean threshold current external to the CIEL was 0.52 (0.15) mA compared to 0.19 (0.09) mA beneath the CIEL (P < 0.001). Successful block was achieved in 30 of 40 subjects that received 5 mL or less of ropivacaine or bupivacaine compared with 97 of 99 that received 10 mL or greater volume (P = 0.006). Injection volumes greater than or equal to 10 mL produced complete sensory and motor block within 30 minutes. Volumes greater than 10 mL did not extend the duration of the sensory or motor block. Injection volumes of 2.5 and 5 mL were associated with delayed onset and decreased block duration and a greater fraction of subjects experiencing pain behind the knee. Conclusions Injecting 10 mL of 0.5% bupivacaine or ropivacaine below the CIEL produces comparable onset and duration of sensory and motor blockade as volumes as large as 30 mL.

A Randomized Trial of Epidural Analgesia Followed by Continuous Femoral Analgesia Compared with Oral Opioid Analgesia on Short- and Long-Term Functional Recovery After Total Knee Replacement

OBJECTIVE The purpose of this study was to compare continuous femoral nerve analgesia to oral opioid analgesics after discontinuation of epidural analgesia following total knee replacement. DESIGN Randomized prospective controlled parallel group trial. Setting.  Large tertiary university teaching hospital in a major Midwestern city. Subjects.  Sixty-two subjects were randomized to receive neuraxial anesthesia followed by either oral analgesics (N = 31) or continuous femoral nerve analgesia (N = 31). INTERVENTIONS   After discontinuation of epidural anesthesia on the morning after surgery, continuous femoral nerve analgesia (CFA), ropivacaine 25 mg bolus and 5 mg/h infusion was initiated. Catheters were removed 24 hours later. All subjects received oral opioid analgesics as needed. OUTCOME MEASURES The primary outcome measure was knee flexion at 1 month. Physical therapy assessments, pain scores, opioid consumption, and patient satisfaction were assessed during hospitalization. Knee flexion, pain scores, and opioid consumption were collected at 1, 6, and 12 months, and health-related quality of life was collected at 6 and 12 months. RESULTS;   The median difference (95% CI) in the change in knee flexion from baseline was 7.5 (0 to 15) degrees greater after CFA (P = 0.04) at 1 month. CFA subjects had greater compliance with physical therapy, reduced pain scores, and opioid requirements during hospitalization. Thromboembolic events occurred in 0/31 CFA vs 4/31 non-CFA subjects (P = 0.04). CONCLUSIONS CFA for 24 hours following discontinuation of epidural analgesia was associated with lower pain scores, greater compliance with physical therapy, increased range of motion, reduced opioid analgesia use, and greater patient satisfaction during hospitalization. The increased flexion of the operated joint was still evident at 1 month postoperatively.