S. Palmisani

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:u2002 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.

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

BACKGROUNDnAlthough anaesthetics are known to alter microcirculation no study has, to our knowledge, documented changes in human skeletal microcirculatory function during general anaesthesia.nnnMETHODSnForty-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).nnnRESULTSnIn 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).nnnCONCLUSIONSnRemifentanil-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:u2002 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:u2002 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.

Intrathecal granuloma formation in a patient receiving long-term spinal infusion of tramadol.

OBJECTIVEnIntrathecal granuloma associated to the tip of subarachnoid catheters implanted in patients receiving long-term spinal infusion is a rare but potentially catastrophic complication. Its development seems to be related to the intrathecal administration of opioid drugs, although not all opioids induce granuloma formation with the same frequency.nnnDESIGNnMorphine or hydromorphone-related granulomas have been reported extensively in the literature, but there are no data about any of the other opioids currently used in an off-label fashion when first-line drugs are contraindicated.nnnSETTING AND PATIENTSnIn this case, we report the first documented case of intrathecal granuloma formation in a patient receiving long-term spinal infusion of tramadol, and we put forward a hypothesis for its development.nnnRESULTS AND CONCLUSIONSnChronic intrathecal administration of high-dose tramadol could cause an inflammatory mass as it can be caused by similar, off-label infusions of morphine or hydromorphone. Additionally, tramadol stimulates the activity of natural killers and the proliferation of lymphocytes.

Low-dose buprenorphine infusion to prevent postoperative hyperalgesia in patients undergoing major lung surgery and remifentanil infusion: a double-blind, randomized, active-controlled trial

BackgroundnPostoperative secondary hyperalgesia arises from central sensitization due to pain pathways facilitation and/or acute opioid exposure. The latter is also known as opioid-induced hyperalgesia (OIH). Remifentanil, a potent μ-opioid agonist, reportedly induces postoperative hyperalgesia and increases postoperative pain scores and opioid consumption. The pathophysiology underlying secondary hyperalgesia involves N-methyl-D-aspartate (NMDA)-mediated pain pathways. In this study, we investigated whether perioperatively infusing low-dose buprenorphine, an opioid with anti-NMDA activity, in patients receiving remifentanil infusion prevents postoperative secondary hyperalgesia.nnnMethodsnSixty-four patients, undergoing remifentanil infusion during general anaesthesia and major lung surgery, were randomly assigned to receive either buprenorphine i.v. infusion (25u2009μg h-1 for 24u2009h) or morphine (equianalgesic dose) perioperatively. The presence and extent of punctuate hyperalgesia were assessed one day postoperatively. Secondary outcome variables included postoperative pain scores, opioid consumption and postoperative neuropathic pain assessed one and three months postoperatively.nnnResultsnA distinct area of hyperalgesia or allodynia around the surgical incision was found in more patients in the control group than in the treated group. Mean time from extubation to first morphine rescue dose was twice as long in the buprenorphine-treated group than in the morphine-treated group: 18 vs 9u2009min (P=0.002). At 30u2009min postoperatively, patients receiving morphine had a higher hazard ratio for the first analgesic rescue dose than those treated with buprenorphine (P=0.009). At three months, no differences between groups were noted.nnnConclusionsnLow-dose buprenorphine infusion prevents the development of secondary hyperalgesia around the surgical incision but shows no long-term efficacy at three months follow-up.