Changes in cerebrospinal fluid magnesium levels in patients undergoing spinal anaesthesia for hip arthroplasty: does intravenous infusion of magnesium sulphate make any difference? A prospective, randomized, controlled study

BACKGROUND

Most investigators have attributed the reduced postoperative pain or anaesthetic drug requirements in patients receiving i.v. magnesium sulphate (MgSO(4)) infusion during spinal or general anaesthesia to central N-methyl-d-aspartate (NMDA) receptor magnesium (Mg) activity. In this study, we investigated how cerebrospinal fluid (CSF) Mg concentrations change after spinal anaesthesia, and whether peripherally infusing MgSO(4) influences central Mg levels.

METHODS

Forty-five patients undergoing continuous spinal anaesthesia for hip arthroplasty were randomly assigned to receive either i.v. MgSO(4) at a dose of 50 mg kg(-1) diluted in 100 ml 0.9% saline solution followed by 15 mg kg(-1) h(-1) for 6 h or saline at the same volume [mean (sd) 64 (10) ml]. The changes in CSF and serum total and ionized Mg concentrations were assessed at six time points before and after spinal anaesthesia. Secondary outcome variables included serum and CSF electrolytes and proteins.

RESULTS

Thirty-five patients completed the study. We found that spinal anaesthesia reduced total and ionized Mg concentrations in CSF by about 10%. Increasing serum Mg concentration over 80% of the baseline value left CSF Mg levels unchanged.

CONCLUSIONS

Spinal anaesthesia unexpectedly reduced CSF total and ionized Mg concentrations in patients undergoing hip arthroplasty, although the mechanism is unclear. The dose used for peripheral MgSO(4) infusion in this study had no influence on central Mg concentrations in neurologically healthy patients undergoing spinal anaesthesia. If CSF Mg concentration is a reliable marker of Mg brain bioavailability, peripherally infused MgSO(4) during spinal anaesthesia is unlikely to influence central NMDA receptor activity.

Postoperative pain treatment SIAARTI Recommendations 2010. Short version

The aim of these recommendations is the revision of data published in 2002 in the "SIAARTI Recommendations for acute postoperative pain treatment". In this version, the SIAARTI Study Group for acute and chronic pain decided to grade evidence based on the "modified Delphi" method with 5 levels of recommendation strength. Analgesia is a fundamental right of the patient. The appropriate management of postoperative pain (POP) is known to significantly reduce perioperative morbidity, including the incidence of postoperative complications, hospital stay and costs, especially in high-risk patients (ASA III-V), those undergoing major surgery and those hospitalized in a critical unit (Level A). Therefore, the treatment of POP represents a high-priority institutional objective, as well as an integral part of the treatment plan for "perioperative disease", which includes analgesia, early mobilization, early enteral nutrition and active physiokinesitherapy (Level A). In order to improve an ACUTE PAIN SERVICE organization, we recommend: --a plan for pain management that includes adequate preoperative evaluation, pain measurement, organization of existing resources, identification and training of involved personnel in order to assure multimodal analgesia, early mobilization, early enteral nutrition and active physiokinesitherapy (Level A); --the implementation of an Acute Pain Service, a multidisciplinary structure which includes an anesthetist (team coordinator), surgeons, nurses, physiotherapists and eventually other specialists; --referring to high-quality indicators in establishing an APS and considering the following key points in its organization (Level C): --service adoption; --identifying a referring anesthetist who is on call 24 hours a day; --patient care during the night and weekend; --sharing, drafting and updating written therapeutic protocols; --continuous medical education; --systematic pain assessment; --data collection regarding the efficacy and safety of the implemented protocols; --at least one audit per year. --a preoperative evaluation, including all the necessary information for the management of postoperative analgesia (Level C); --to adequately inform the patient about the risks and benefits of drugs and procedures used to obtain the maximum efficacy from the administered treatments (Level D). We describe pharmacological and loco-regional techniques with special attention to day surgery and difficult populations. Risk management pathways must be the reference for early identification and treatment of adverse events and chronic pain development.

Tetraplegia following parathyroidectomy in two long-term haemodialysis patients

We report two cases of postoperative iatrogenic tetraparesis, which occurred in different hospitals after surgery for parathyroidectomy. Both patients were on long-term haemodialysis. The prolonged neck extension usually required by this procedure was probably the main factor involved in the genesis of the spinal cord injury. Spinal abnormalities associated with chronic renal failure may have made these patients more vulnerable. In our opinion, it is advisable to investigate thoroughly any sign of spinal stenosis in patients who undergo any procedure requiring significant neck extension, particularly if on long-term haemodialysis.

Ropivacaine and levobupivacaine for bilateral selective ankle block in patients undergoing hallux valgus repair

BACKGROUND

A selective ankle block, blocking the tibial, deep and superficial peroneal nerves, can be used successfully for great toe surgery. No comparative information is available on selective ankle block using ropivacaine and levobupivacaine.

METHODS

We compared the onset time and success rate of a selective ankle block using low volumes (12 ml) of ropivacaine 10 mg/ml and levobupivacaine 7.5 mg/ml in 40 patients undergoing elective repair of bilateral hallux valgus. Each patient received an ankle block induced in one foot with ropivacaine and in the contralateral foot with levobupivacaine.

RESULTS

The success rate was higher [90% vs. 75%, hazard ratio (95% CI) 0.39 (0.23-0.64)] and anesthesia onset time was shorter (median, 10 vs. 20 min) after ropivacaine than after levobupivacaine. In successful ankle blocks, post-operative pain was similar in the two groups.

CONCLUSION

In this study, ropivacaine 10 mg/ml had a shorter anesthesia onset time and a higher success rate than levobupivacaine 7.5 mg/ml for selective ankle block.

Effects of sternotomy on heart-lung interaction in patients undergoing cardiac surgery receiving pressure-controlled mechanical ventilation

BACKGROUND

The key concept underlying the dynamic indexes of preload dependence is the physiological heart-lung interaction. During sternotomy this interaction undergoes various changes, some of which remain unclear. Our primary aim was to investigate how the interaction changes during sternotomy by evaluating pulse pressure variations (PPV) with the chest closed and after sternotomy in patients ventilated using the pressure-controlled mode.

METHODS

We prospectively studied 25 patients undergoing coronary artery bypass grafting (CABG) receiving pressure-controlled ventilation. Standard hemodynamic data, PPV and tidal volume delivered were recorded before and after sternotomy, and, with the chest open, before and after positive end-expiratory pressure (PEEP) was applied and inspiratory pressure was increased.

RESULTS

Sternotomy left all variables statistically unchanged from values before thoracotomy although in the subgroup of patients with a PPV > 8% (56%) sternotomy significantly reduced PPV (from 14.4 +/- 5.2% to 8.9 +/- 4.5%). With the chest open, when PEEP was applied at 5 cm H(2)O, tidal volume decreased (from 643 +/- 83 to 587 +/- 104 ml) and stroke volume decreased (from 77 +/- 17 to 72 +/- 15 ml) but PPV remained unchanged. When PEEP was discontinued and inspiratory pressure was increased by 5 cm H(2)O, tidal volume increased (from 643 +/- 83 to 814 +/- 89 ml) and PPV increased (from 8.2 +/- 3.9% to 12.3 +/- 6.8%) but stroke volume remained unchanged.

CONCLUSIONS

In patients ventilated in the pressure-controlled mode, except those with a pre-sternotomy PPV > 8% (fluid responders), sternotomy leaves standard hemodynamic data and PPV unchanged. When the chest wall is open, cyclic changes (tidal volume) but not continuous changes (PEEP) in intrathoracic pressure directly influence PPV.

Combined intrathecal and epidural magnesium sulfate supplementation of spinal anesthesia to reduce post-operative analgesic requirements: a prospective, randomized, double-blind, controlled trial in patients undergoing major orthopedic surgery

BACKGROUND

New ways of decreasing post-operative analgesic drug requirements are of special interest after major surgery. Magnesium sulfate (MgSO(4)) alters pain processing and reduces the induction and maintenance of central sensitization by blocking the N-methyl-D-aspartate (NMDA) receptor in the spinal cord. We investigated whether supplementation of spinal anesthesia with combined intrathecally and epidurally infused MgSO(4) reduced patients' post-operative analgesia requirements.

METHODS

In a randomized, prospective, double-blind, placebo-controlled trial, we enrolled 120 consecutive patients undergoing orthopedic surgery during spinal anesthesia (levobupivacaine and sufentanil). Patients were randomly assigned to receive intrathecal MgSO(4) (94.5 mg, 6.3%), epidural MgSO(4) (2%, 100 mg/h), intrathecal and epidural MgSO(4) combined or spinal anesthesia alone (controls). Post-operative morphine consumption was assessed in all groups by patient-controlled analgesia (PCA).

RESULTS

Of the 120 patients enrolled, 103 (86%) completed the study. Morphine consumption at 36 h after surgery was 38% lower in patients receiving spinal anesthesia plus epidural MgSO(4) [- 14.963 mg; 95% confidence interval (CI), - 1.44 to - 28.49 mg], 49% lower in those receiving spinal anesthesia plus intrathecal MgSO(4) (- 18.963 mg; 95% CI, - 5.27 to - 32.65 mg) and 69% lower in the intrathecal-epidural combined group (- 26.963 mg; 95% CI, - 13.73 to - 40.19 mg) relative to control patients receiving spinal anesthesia alone. No complications developed during the post-operative course or at 1 month after surgery.

CONCLUSION

In patients undergoing orthopedic surgery, supplementation of spinal anesthesia with combined intrathecal and epidural MgSO(4) significantly reduces patients' post-operative analgesic requirements.

Lateral popliteal sciatic nerve block: a single injection targeting the tibial branch of the sciatic nerve is as effective as a double-injection technique

BACKGROUND

Evidence indicating that single- and double-injection techniques for inducing a sciatic nerve block via a posterior subgluteal approach yield a similar success rate prompted us to investigate whether the two anesthetic techniques yield a similar success rate via a lateral approach. We also hypothesized that, owing to the peculiar anatomic features of the sciatic nerve at the popliteal level, a single injection via the lateral approach might induce effective anesthesia by targeting the tibial nerve only.

METHODS

Ninety-six patients undergoing popliteal sciatic nerve block via a lateral popliteal approach for foot surgery were randomized to receive a single 30-ml injection of ropivacaine 7.5 mg/ml to block the tibial nerve (TN group, n= 32) or the common peroneal nerve (CPN group, n= 32), or two separate 15-ml injections (TN + CPN group, n= 32), after stimulation to evoke motor responses from the target nerves.

RESULTS

The mean time to obtain a complete sensory blockade (surgical anesthesia) was shorter in the TN group than in the CPN and TN + CPN groups (14 +/- 7 min vs. 23 +/- 17 and 21 +/- 14 min, respectively; P < 0.05). The success rate was similar in the TN and TN + CPN groups (94%) and, 25 min after the initial injection, was already better in these groups than in the CPN group (94% vs. 75%; P < 0.05).

CONCLUSIONS

A lateral popliteal sciatic nerve block obtained with a single 30-ml injection of ropivacaine 7.5 mg/ml after electrostimulation to locate the tibial nerve is as effective as multiple TN + CPN stimulation and injection, and local anesthesia has a significantly shorter onset time.

Anatomy and imaging of lumbar plexus

Sensory and motor innervation of the whole lower limb is due to lumbo-sacral-plexus that arises from the spinal roots L1-S3. The whole lower limb can be blocked from its origin to the foot for surgical procedures or for postoperative analgesia. Single or continuous lumbar plexus blockade can be an alternative to general anesthesia and central block in elective and traumatic hip or femur repair, for knee surgery and for postoperative analgesia. To understand the relative plexus depth and the relationship between the plexus and the closer structure in order to avoid complicance, the aid of imaging technique such as CT-scan, MRI and ultrasounds can be considered.

Postpartum cerebral ischaemia after accidental dural puncture and epidural blood patch

Puerperal women are reported to have a rate of cerebral infarction 13 times greater than non-pregnant females. We report a case of cerebral ischaemia in a 30-yr-old healthy parturient after epidural analgesia for labour, complicated by dural puncture treated with two epidural blood patches. Investigations showed the development of cerebral ischaemia on postpartum day 14. A transcranial Doppler ultrasonography showed vasospasm of the left middle cerebral artery still present at 3-month follow-up. At 1-yr follow-up, the patient had homonymous hemianopsia. We discuss the possible causative mechanism of the cerebral ischaemia in relation to the dural puncture and epidural blood patch.

Ambulatory anesthesia for foot surgery

Ambulatory surgery has developed extensively over the past few years in most Western countries. The absence of specific legislation in Italy creates a lack of trust in patients and interferes with the development of this discipline. The authors describe their experience in the organisation of an outpatient foot surgery centre over the past thirteen years, which is in constant expansion and currently performs about 300 operations every year. They report the criteria used to select patients, the organisation of the operating theatre, pre- and postoperative treatment and the anesthetic techniques used. Among the latter, they describe a new approach used to block the popliteal sciatic nerve. The results obtained show a high approval rate from the majority of patients treated. The authors attribute this success to a series of factors, including patient selection and surgical procedures, the maintenance of constant standards of quality similar to those in hospitals and the experience of outpatient anesthesia.

Prolonged mivacurium-induced neuromuscular block. Case report

A 38-year-old white male patient was admitted to the hospital for elective surgery. General anesthesia was performed with propofol, alfentanil, nitrous oxide and mivacurium as neuromuscular blocker. Seven months before he had the same surgery without anesthetic problems (he received: propofol, vecuronium bromide, fentanil, nitrous oxide). Neuromuscular monitoring was carried out because the patient was included in a study assessing the clinical effect of mivacurium in microlaryngoscopy surgery. After mivacurium administration the first signs of recovery from neuromuscular block were observed after 255 min. The tracheal tube was withdrawn after 410 min from mivacurium administration, at this time the T1 was 80% of the control values and 7 min later the T1 reached 98%.

High-dose aprotinin with gentamicin-vancomycin antibiotic prophylaxis increases blood concentrations of creatinine and cystatin C in patients undergoing coronary artery bypass grafting

Both aprotinin and gentamicin-vancomycin antibiotic prophylaxis have been used widely in cardiac surgery to prevent bleeding and infections, respectively. As the drugs are excreted almost entirely by glomerular filtration, we investigated their action on renal function when administered either separately or together. To increase consistency, we measured serum concentrations of creatinine and cystatin C, a new marker of glomerular filtration rate, that many recent studies have shown to be more sensitive than serum creatinine. One hundred patients undergoing coronary artery bypass surgery were allocated randomly to one of four groups: group A received antibiotic prophylaxis with cefamandole and no aprotinin; group B received cefamandole and high-dose aprotinin; group C received antibiotic prophylaxis with gentamicin and vancomycin, but no aprotinin; and group D received both high-dose aprotinin and gentamicin-vancomycin antibiotic prophylaxis. Data from 84 patients, for whom data collection was complete, were analysed. In the first week after operation, mean serum concentrations of cystatin C and creatinine either remained constant or decreased slowly in all groups, except for group D. In group D, both markers increased gradually from postoperative day 2 onwards. The increase in cystatin C was significant on postoperative day 5 (from mean 1.02 (SD 0.11) mg litre-1 before operation to 1.35 (0.32) mg litre-1; P < 0.05), reaching a peak on postoperative day 7 (1.45 (0.35) mg litre-1; P < 0.05), while the increase in creatinine concentration was significant on postoperative day 6 (from 1.05 (0.16) mg dl-1 before operation to 1.29 (0.34) mg dl-1; P < 0.05). We conclude that simultaneous administration of high-dose aprotinin and prophylactic use of gentamicin with vancomycin increased serum concentrations of cystatin C and creatinine in the first postoperative week in patients undergoing cardiac surgery.

Effects of propofol on the human heart electrical system: a transesophageal pacing electrophysiologic study

Previous studies have shown that infusion of propofol has sometimes been associated with bradyarrhythmias. To evaluate the effects of propofol on the electrical system of the heart, we carried out an electrophysiologic study with transesophageal pacing on ten healthy subjects scheduled for minor elective maxillo-facial surgery. By means of atrial pacing conducted by a progressive increase in stimulation cycles, we determined, in awake patients and during propofol anesthesia (2.5 mg kg-1 for induction, followed by 100 micrograms kg-1 min-1 for maintenance), the correct sinus recovery time and the eventual appearance of Wenckebach atrio-ventricular block. We did not notice sinoatrial node depression or pathologic increase in the atrio-ventricular conduction.

[Diazepam versus midazolam for "wakeful sedation" in oral surgery]

I.v. midazolam was compared with diazepam in 112 dental outpatients in order to obtain a control of sedation. Midazolam has shown better results in all the parameters evaluated (memory scale, pharmacokinetics and pharmacodynamics values) and in controlling sedation. The Authors consider midazolam as a preferred drug in dental outpatients and hope to get it available also in Italy.