G. Pinto

Microvascular dysfunction and skeletal muscle oxygenation assessed by phase-modulation near-infrared spectroscopy in patients with septic shock

ObjectiveSepsis is now considered a disease of the microcirculation. Little is known about the various sepsis-induced changes responsible for microvascular dysfunction. We investigated human microvascular function, regulation, oxygenation, and cellular metabolism during subacute septic shock.Design and settingProspective case-control study in a nine-bed polyvalent surgical ICU of a university hospital.Patients and participantsA prospectively enrolled group of 26 patients (13 with septic shock, 13 nonseptic postsurgical patients) and 15 healthy volunteer controls.Measurements and resultsThe absolute tissue hemoglobin concentrations (oxygenated hemoglobin and deoxyhemoglobin) were measured noninvasively in arterioles, capillaries, and venules by phase-modulation near-infrared spectroscopy in the human brachioradial muscle during a series of venous occlusions and an arterial occlusion (ischemia) induced by applying a pneumatic cuff. These measurements were used to calculate tissue blood volume, postischemic hemoglobin resaturation time, microvascular compliance, and O2 consumption. Patients with sepsis had significantly higher tissue blood volume values and lower compliance than healthy controls. They also had longer postischemic hemoglobin resaturation times than the other two groups and blunted resaturation curves. O2 consumption was lower in patients with sepsis than in healthy controls. In patients with septic shock cuff-induced ischemia left O2 consumption unchanged, whereas in healthy volunteers it reduced O2 consumption to values almost matching those of patients with septic shock.ConclusionsThese findings show that septic shock alters microvascular muscle function and regulation. Diminished local VO2 presumably reflects maldistribution and faulty autoregulation of local blood flow.

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 (MgSO4) 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 MgSO4 reduced patients’ post‐operative analgesia requirements.

Control of post anaesthetic shivering with nefopam hydrochloride in mildly hypothermic patients after neurosurgery

Postoperative shivering may be prevented by maintaining normothermia intraoperatively or it may be treated using specific drugs.

Effects of remifentanil-based general anaesthesia with propofol or sevoflurane on muscle microcirculation as assessed by near-infrared spectroscopy

BACKGROUND Although anaesthetics are known to alter microcirculation no study has, to our knowledge, documented changes in human skeletal microcirculatory function during general anaesthesia. METHODS Forty-four patients undergoing maxillofacial surgery at a university hospital were prospectively randomized to receive general anaesthesia with remifentanil combined with propofol or sevoflurane. Muscle microcirculation was investigated with near-infrared spectroscopy (NIRS) before general anaesthesia was induced and 30 min later. An NIRS device (NIMO, Nirox) was used to quantify calf deoxyhaemoglobin [HHb], oxyhaemoglobin [HbO2], and total haemoglobin [HbT] concentrations, coupled to a series of venous and arterial occlusions to measure calf blood flow, muscle oxygen consumption, calf vascular resistance, microvascular compliance, and haemoglobin resaturation rate (RR). RESULTS In both the groups, general anaesthesia induced marked changes in muscle microcirculation: the tissue blood volume increased (+33% in remifentanil-sevoflurane and +45% with remifentanil-propofol groups), microvascular resistance decreased (-31% and -38%, respectively), and the post-ischaemic haemoglobin RR decreased (-48% and -36%, respectively). In the remifentanil-propofol group, the muscle blood flow increased (P<0.001), whereas in the remifentanil-sevoflurane group microvascular compliance and muscle oxygen consumption decreased (P<0.01). CONCLUSIONS Remifentanil-based general anaesthesia with propofol or sevoflurane altered the muscle microcirculation in different ways. Quantitative NIRS, a technique that takes into account the optical tissue properties of the individual subject, can effectively measure these changes non-invasively.

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.

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.

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.

Critical pneumonia complicating early-stage pregnancy

We present a case of community-acquired methicillin-resistant Staphylococcus aureus necrotizing pneumonia, Panton-Valentine leukocidin positive, in a woman at 14 weeks of pregnancy. To our knowledge, this is the first case reporting this critical lung infection occurring during an early phase of pregnancy. This case study alerts physicians to the increasing worldwide spread of these uncommon yet virulent and potentially lethal infections. In our patient, antibiotic therapy with linezolid plus rifampin started at 14 weeks of pregnancy had a successful outcome without inducing toxicity or teratogenesis in the fetus.

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.

Cholinergic system and neuroinflammation: Implication in multiple sclerosis

BACKGROUND Multiple sclerosis (MS) is an inflammatory and neurodegenerative disease of the central nervous system (CNS) characterized by leucocytes infiltration, demyelination, axonal degeneration and neuronal death. Although the etiology of MS is still unkwon, inflammation and autoimmunity are considered to be key players of the disease. Nervous System: The severe alterations affecting the nervous system contribute to the motor and cognitive disabilities and are in large part dependent on severe inflammatory processes active in both central nervous system and immune system. Acetylcholine (ACh) appears to be involved in the modulation of central and peripheral inflammation. Immune cells as well as astrocytes and microglia respond to ACh stimuli by activation of cholinergic receptors. Muscarinic and nicotinic receptors differently contribute to the modulation of immunological and inflammatory processes stimulating pro- and anti-inflammatory cytokines respectively. The role played by ACh in MS is not yet fully understood, although some results point to its involvement in different neurological disorders such as Alzheimers disease and schizophrenia. CONCLUSION In the present review we summarize the evidence indicating the correlation between nervous system dysfunction in MS, with inflammation and cholinergic system alterations. Experiments performed in MS animal models and analyses on biological fluids from MS patients such as blood, serum and cerebrospinal fluid suggest that cholinergic alterations may contribute to the dysregulated inflammatory processes of MS. Many current therapeutic approaches in MS are based on anti-inflammatory drugs. We also discuss how the use of cholinesterase inhibitors or ACh mimetics may represent a new interesting therapeutic approach in MS.