E. Amaniti

Ropivacaine myotoxicity after single intramuscular injection in rats

Background and objective: We conducted this study in order to evaluate the potential myotoxic effects of ropivacaine after single injection in rats and the time‐course of the possible damage. Methods: One hundred and twenty‐eight male Wistar rats were allocated to four different groups. The first three groups received intramuscular injections with ropivacaine 0.75%, ropivacaine 0.5% and normal saline, respectively, into the right tibialis anterior muscle. The fourth group received needle puncture without injection. Eight rats from each group were sacrificed 2, 4, 7 and 30 days after injection. Samples were blindly examined under light microscope for evidence of myotoxicity, scored as 0 = no damage to 3 = myonecrosis and statistically analysed. Samples obtained 7 days after injection were also examined under transmission electron microscope. Results: Ropivacaine 0.75% and ropivacaine 0.5% caused extensive destruction to muscles fibres, compared to saline or needle on days 2, 4 and 7. Statistically significant differences were found in muscle damage by drug injections among all groups except for saline vs. needle groups. Thirty days after injections all sample appearances had returned to normal. Conclusions: Ropivacaine after single intramuscular injection caused reversible muscle damage in a dose‐dependent manner.

Rocuronium duration of action under sevoflurane, desflurane or propofol anaesthesia.

Background and objective: We conducted a prospective randomized study to evaluate whether the duration of action of a single bolus dose of rocuronium is influenced by maintenance of anaesthesia with sevoflurane, desflurane or propofol infusion. Methods: Fifty-seven ASA I-II patients undergoing elective abdominal surgery were enrolled in this study. Anaesthesia was induced with thiopental 3-5 mg kg−1 or propofol 2.5 mg kg−1 and fentanyl 5 μg kg−1 and tracheal intubation was facilitated with rocuronium 0.9 mg kg−1. Thereafter patients were randomly allocated to three different groups to receive sevoflurane, desflurane or propofol for maintenance of anaesthesia. Recovery of neuromuscular function was monitored by single twitch stimulation of the ulnar nerve and by recording the adductor pollicis response using accelerometry. Intergroup recovery times to 5% of control value of single twitch were analysed using analysis of variance with Bonferroni correction. Results: The mean (95% confidence interval) recovery time to 5% of control value of single twitch during desflurane anaesthesia was 90.18 (86.11-94.25) min. Significantly shorter recovery times were observed during sevoflurane or propofol anaesthesia, 58.86 (54.73-62.99) min and 51.11 (45.47-56.74) min, respectively (P < 0.001). There were also significant differences in the recovery time between groups receiving desflurane vs. sevoflurane (P < 0.001) and desflurane vs. propofol (P < 0.001). Conclusions: Desflurane anaesthesia significantly prolongs the duration of action of rocuronium at 0.9 mg kg−1 single bolus dose, compared to sevoflurane or propofol anaesthesia maintenance regimens.

Correlation of central venous-arterial and mixed venous- arterial carbon dioxide tension gradient with cardiac output during neurosurgical procedures in the sitting position

Background and objective The study was conducted to evaluate the correlation of central venous–arterial and mixed venous–arterial pCO2 gradient with cardiac output in patients being operated in the sitting position. Methods Fifty-one patients, aged 41–69 years, classified as American Society of Anesthesiologists physical status II and III, scheduled to undergo elective neurosurgical procedures in the sitting position, were enrolled in this prospective cohort study. Simultaneous blood gas samples from arterial, central venous and pulmonary artery catheters were collected at four different time points during supine and sitting position. Cardiac index (CI) determination was accomplished simultaneously, with continuous cardiac output technique. The mixed venous–arterial pCO2 and central venous–arterial pCO2 gradients were calculated and related to CI at the specific time points, thus a total of 204 points of comparison were obtained. Results Changing from the supine to the sitting position induced a significant deterioration of CI, right atrial pressure, mean pulmonary arterial pressure and pulmonary wedge pressure. The mean delta pCO2 difference (bias) in the four time points ranged between −0.07 and −0.27. The upper (1.59–1.71 mmHg) and lower limits of agreement (−2.16 to −1.82 mmHg) were quite narrow, suggesting an acceptable overall agreement between the mixed and central venous pCO2 differences. The coefficient of determination (R2) between the venous–arterial pCO2 and CI for mixed and central venous circulations was 0.830 and 0.760 (P < 0.001 for both), respectively. In contrast, R2 values between mixed and central venous oxygen saturation values and CI were 0.324 and 0.286, respectively (P < 0.001 for both), illustrating a rather weak relationship. Conclusion It seems that venous–arterial pCO2 values obtained from mixed and central venous circulations can be reliably interchanged in estimating CI in patients undergoing neurosurgical procedures in the sitting position. Thus, central venous–arterial pCO2 gradient could serve as a useful and simple method for estimating cardiac performance, in which further invasive monitoring is not strongly indicated.

Baroreceptors discharge due to bilateral aortic denervation evokes acute neuronal damage in rat brain

Deep hypothermic circulatory arrest in cardiothoracic surgery evokes severe brain damages. On the other hand, blood pressure stimuli discontinuation to the brain has been found to induce alterations in neurotransmitter release, including glutamate, in numerous brain regions. Furthermore, it is well established that excessive glutamate release can induce neuronal injury, a process called excitotoxicity. Aim of the present study was the evaluation of possible acute neuronal damage after bilateral aortic denervation (bAD), imitating the baroreceptors discharge during circulatory arrest. Male, Wistar rats underwent either bAD or Sham operation under continuous hemodynamic monitoring. Two hours after completion of the procedure, rats were sacrificed and the brains were dissected and cut in specific levels corresponding to selective brain regions, based on either their participation in neuronal circuits, regulating blood pressure, or their vulnerability, after deep hypothermic circulatory arrest. Slices were stained and examined under light microscope using morphometric techniques. Increased number of necrotic neurons were found among bAD rats in amygdaloid complex (p=0.005), motor cortex (p=0.001), CA1 and CA3 (p=0.02 and 0.015) but not in posterior hypothalamic nucleus and Purkinje cell. Higher ratios of necrotic neurons were found in amygdaloid complex (p=0.002), motor layer (p=0.003 and p=0.000) and the hippocampal CA1 region (p=0.027) of bAD rats. The present study shows that baroreceptors discharge due to bAD may induce acute neuronal loss in brain regions involved in blood pressure regulation. Neuronal loss might be attributed to excitotoxic phenomena and it is following the same topographic distribution seen in deep hypothermic circulatory arrest, revealing a concurrent to hypoxia/ischemia mechanism of brain damage.

Injeção inadvertida de succinilcolina como uma dose teste epidural

BACKGROUND AND OBJECTIVES Epidural action of neuromuscular blocking agents could be explained under the light of their physicochemical characteristics and epidural space properties. In the literature there are few cases of accidental neuromuscular agents epidural administration, manifesting mainly with neuromuscular blockade institution or fasciculations. CASE REPORT We report a case of accidental succinylcholine administration as an epidural test dose, in a female patient undergoing scheduled laparotomy, under combined general and epidural anesthesia. Approximately 2min after the succinylcholine injection the patient complained for shortness of breath, while mild fasciculations appeared in her trunk and face, managed by immediate general anesthesia institution. With the exception of a relatively longer duration of neuromuscular blockade compared with intravenous administration, no neurological or cardiovascular sequelae or other symptoms of local or systemic toxicity were observed. CONCLUSIONS Oral administration of diazepam seems to lessen the adverse effects from accidental epidural administration of succinylcholine. The meticulous and discriminative labeling of syringes, as well as keeping persistent cautions during all anesthesia procedures remains of crucial importance.

Cerebral Oxygenation Impairment and S-100β Protein Release During Off-Pump Coronary Artery Revascularization

OBJECTIVE To elucidate the magnitude of global cerebral oxygenation impairment, using cerebral oxygenation indices and S-100β protein as potential markers, during off-pump coronary artery bypass grafting (OPCAB). DESIGN Prospective cohort study. SETTING Tertiary cardiac center. PARTICIPANTS Thirty-five patients undergoing OPCAB. INTERVENTIONS Jugular bulb and arterial blood samples for cerebral oxygenation indices (arterial oxygen and carbon dioxide partial pressures, jugular bulb oxygen saturation, arterial-jugular bulb oxygen content, arterial-jugular carbon dioxide partial pressure, brain oxygen extraction ratio, and estimated respiratory quotient) and S-100β protein determination were collected at anesthesia induction; anterior, inferior, and posterior wall anastomoses; after sternal closure; and 6 hours postoperatively. Concomitant hemodynamic data were obtained. The S-100β determination was extended to 12 and 24 hours postoperatively. MEASUREMENTS AND MAIN RESULTS Heart positioning for the target vessel exposure induced significant hemodynamic deterioration (p < 0.001). Although cerebral oxygenation indices were influenced adversely by a low-cardiac-output state mainly during vertical heart dislocation (p < 0.001), they remained within normal limits. Hemodynamic and cerebral oxygenation statuses reverted to baseline within 6 hours postoperatively. Similarly, S-100β jugular bulb and arterial protein levels presented a gradual increase, which peaked by the end of surgery (means, 0.54 and 0.62 μg/L, respectively; p < 0.001) and then decreased by the first postoperative day. Jugular bulb-arterial S-100β levels were maximized during posterior wall anastomosis (0.098 μg/L; p < 0.01). CONCLUSION Although exposure of the 3 main coronary arteries during OPCAB promotes derangement of the cerebral oxygen indices and S-100β release, this seems to be transient, remains within the near-normal range, and is reversible almost completely 6 hours postoperatively.

Unexpected complication of massive intraoperative pulmonary embolism following elective sigmoidectomy in the supine position

We describe a case of massive intraoperative pulmonary thromboembolism during elective sigmoidectomy in the supine position. During recovery from anesthesia, the patient developed hemodynamic compromise and severe hypoxemia. Intravenous inotropes and mechanical ventilation were instituted. The abrupt onset of symptoms and the pulmonary artery catheter, chest radiograph, and transesophageal echocardiography findings suggested massive pulmonary thromboembolism as a possible cause of the hemodynamic compromise and hypoxemia. Emergent angiography could not be carried out due to the patient’s poor clinical status. Lack of experience in performing embolectomy, along with contraindication for thrombolysis, imposed the use of intravenous heparin and hemodynamic support as the only appropriate therapeutic modality. After 2 days’ aggressive hemodynamic and ventilatory support, the patient had an uneventful course, and was discharged from the intensive care unit (ICU) 14 days later.