Changes in venous blood lactate, venous blood gases, and somatosensory evoked potentials after tourniquet application

Altered markers of mitochondrial function in adults with autism spectrum disorder

Previous research suggests potential mitochondrial dysfunction and changes in fatty acid metabolism in a subgroup of individuals with autism spectrum disorder (ASD), indicated by higher lactate, pyruvate levels, and mitochondrial disorder prevalence. This study aimed to further investigate potential mitochondrial dysfunction in ASD by assessing blood metabolite levels linked to mitochondrial metabolism. Blood levels of creatine kinase (CK), alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate, pyruvate, free and total carnitine, as well as acylcarnitines were obtained in 73 adults with ASD (47 males, 26 females) and compared with those of 71 neurotypical controls (NTC) (44 males, 27 females). Correlations between blood parameters and psychometric ASD symptom scores were also explored. Lower CK (pcorr  = 0.045) levels were found exclusively in males with ASD compared to NTC, with no such variation in females. ALT and AST levels did not differ significantly between both groups. After correction for antipsychotic and antidepressant medication, CK remained significant. ASD participants had lower serum lactate levels (pcorr  = 0.036) compared to NTC, but pyruvate and carnitine concentrations showed no significant difference. ASD subjects had significantly increased levels of certain acylcarnitines, with a decrease in tetradecadienoyl-carnitine (C14:2), and certain acylcarnitines correlated significantly with autistic symptom scores. We found reduced serum lactate levels in ASD, in contrast to previous studies suggesting elevated lactate or pyruvate. This difference may reflect the focus of our study on high-functioning adults with ASD, who are likely to have fewer secondary genetic conditions associated with mitochondrial dysfunction. Our findings of significantly altered acylcarnitine levels in ASD support the hypothesis of altered fatty acid metabolism in a subset of ASD patients.

The role of creatine kinase in distinguishing generalized tonic-clonic seizures from psychogenic non-epileptic seizures (PNES) and syncope: a retrospective study and meta-analysis of 1300 patients

BACKGROUND/AIM

As the clinical differentiation between epileptic seizures, psychogenic non-epileptic seizures (PNES), and syncope depends mainly on a detailed report of the event, which may not be available, an objective assessment of a potential biochemical analysis is needed. We aimed to investigate whether serum creatine kinase (CK) could be used to differentiate epileptic seizure from PNES and syncope and to assess the strength of evidence present.

METHODS

We directed a retrospective cohort study coupled with a systematic review and meta-analysis of studies that measured CK in patients with epilepsy, PNES, syncope, and healthy controls.

RESULTS

The cohort study, which traced 202 patients, showed that the CK level was significantly higher 48 h after the event in the epilepsy group versus patients with syncope (p < 0.01) Along with 1086 patients obtained through a database search for meta-analysis, CK level compared to different types of seizures from PNES was higher in epileptic seizure patients with a mean difference of 568.966 mIU/ml (95% CI 166.864, 971.067). The subgroup analysis of CK showed that it was higher in GTCS compared to syncope with a mean difference of 125.39 mIU/ml (95% CI 45.25, 205.52).

DISCUSSION

Increased serum levels of CK have been associated mainly with epileptic seizures in relation to non-epileptic events. However, further studies would try to explore the variation in measurements and any other potential diagnostic marker.

CONCLUSION

The cohort study shows that the CK level in epilepsy seizures is higher after 48 h from the event compared to syncope. Moreover, the meta-analysis results show the present diagnostic utility of CK and its importance to be used in accordance with a detailed report of the event.

Methods of ex vivo analysis of tissue status in vascularized composite allografts

Vascularized composite allotransplantation can improve quality of life and restore functionality. However, the complex tissue composition of vascularized composite allografts (VCAs) presents unique clinical challenges that increase the likelihood of transplant rejection. Under prolonged static cold storage, highly damage-susceptible tissues such as muscle and nerve undergo irreversible degradation that may render allografts non-functional. Skin-containing VCA elicits an immunogenic response that increases the risk of recipient allograft rejection. The development of quantitative metrics to evaluate VCAs prior to and following transplantation are key to mitigating allograft rejection. Correspondingly, a broad range of bioanalytical methods have emerged to assess the progression of VCA rejection and characterize transplantation outcomes. To consolidate the current range of relevant technologies and expand on potential for development, methods to evaluate ex vivo VCA status are herein reviewed and comparatively assessed. The use of implantable physiological status monitoring biochips, non-invasive bioimpedance monitoring to assess edema, and deep learning algorithms to fuse disparate inputs to stratify VCAs are identified.

Exercise Oximetry Correlates Better With Exercise-Induced Lactate Increase, than Ankle Brachial Index or Walking Time, in Vascular Claudicants

In claudication, the correlation between walking-induced biomarkers and indices of clinical severity (e.g., walking distance or ankle brachial index (ABI)), is fair. We hypothesized that a correlation would be observed between the clinical estimation of ischemia severity with exercise transcutaneous oximetry (Ex-TcpO2) and lactate increase. A prospective study was performed among 377 patients with arterial claudication. We recorded age, sex, ABI, body mass index (BMI), systolic arterial blood pressure (SBP), and glycemia. Capillary blood lactate was measured at rest and 3 min after a constant load treadmill test. We recorded maximum walking time (MWT), heart rate (HRmax), the sum of minimal decrease from oxygen values for buttocks, thighs and calves Ex-TcpO2 (DROPmin), as well as the amplitude of chest-TcpO2 decrease. A multilinear regression model was used to assess the variables associated with lactate increase. BMI, SBP, HRmax, the amplitude of decrease in chest-TcpO2 and DROPmin, but not age, sex, ABI, MWT, diabetes mellitus nor glycemia, were significantly associated to lactate increase in the model. Because it accounts for the severity and diffusion of lower-limb exercise-induced ischemia and detects exercise induced hypoxemia, TcpO2 may be preferable to ABI or MWT to estimate the metabolic consequences of walking in claudicants.

Is Spinal Dexmedetomidine Aggravating Hypotension after Tourniquet Deflation?

Background and Aims:

The addition of dexmedetomidine to spinal anesthesia decreases the incidence of tourniquet pain but may aggravate hypotension after tourniquet deflation.

Methods:

Fifty patients were included in this prospective, double-blinded, randomized study, randomly divided into two equal groups of 25 patients each. Spinal anesthesia was performed using 2.5 mL of 0.5% hyperbaric bupivacaine plus 0.5 mL of normal saline in control group (Group C) or 2.5 mL of 0.5% hyperbaric bupivacaine plus 0.5 mL (5 μg) of dexmedetomidine in (Group D). Tourniquet pain was treated by 50 mg of meperidine and repeated in a dose of 20 mg, and the total meperidine consumption was calculated. After tourniquet deflation, heart rate and mean blood pressure were measured for 15 min in the operating room and at these times: before induction of anesthesia (baseline), after inflating tourniquet (inflation), 1 min before deflating tourniquet (predeflation), after tourniquet deflation (10 min postdeflation), and maximum blood pressure and heart rate changes. Duration of time that started before the minimum blood pressure and maximum heart rate was changed until recovery was recorded.

Results:

Pain after torniquet inflation was significantly higher in the Group C compared to the Group D. The maximal change of blood pressure was lower in the dexmedetomidine than in the control group. The mean time between the maximal change in blood pressure reached and started to recover was 135 ± 14 s in the dexmedetomidine group and 80 ± 31 s in the control group (P < 0.01) and maximal heart rate change was lower in dexmedetomidine group than the control group. The time between the maximal heart rate changes until recovery was 113.2 ± 19 s in the dexmedetomidine group and 53.2 ± 11 s in the control group P < 0.01.

Conclusion:

Adding dexmedetomidine to spinal anesthesia decreases the incidence of tourniquet pain but aggravates the hemodynamic effect of tourniquet deflation.

A novel approach of using brachial plexus blockade as an experimental model for diagnosis of intraoperative nerve dysfunction with somatosensory evoked potentials: a blinded proof-of-concept study

PURPOSE

Intraoperative nerve dysfunction has been difficult to investigate because of its rarity and unpredictable occurrence. The diagnostic test attributes of nerve function monitors have not been clearly defined. This proof-of-concept study aimed to assess the feasibility of using brachial plexus blockade (BPB) in awake patients as an experimental model for nerve dysfunction to characterize the diagnostic test attributes of somatosensory evoked potentials (SSEPs).

METHODS

We obtained baseline SSEPs and neurologic function in patients and subsequently placed BPBs (experimental model) to generate progressive states of nerve dysfunction. We monitored SSEP changes (index test) and neurologic symptoms (reference standard) simultaneously during the onset of BPB to determine the temporal relationships and diagnostic test attributes of SSEPs.

RESULTS

Brachial plexus blockade produced differential motor and sensory dysfunction that allowed simultaneous clinical and neurophysiologic assessment. One hundred and fifty-seven pairs of multiple data points from 14 patients were included for final analysis. The onset of abnormal SSEP signals almost always preceded the onset of neurologic symptoms. The sensitivities and specificities of SSEP to detect the impairment of power (motor rating score ≤ 4/5), cold sensation, and two-point discrimination were 100% and 67%, 99% and 55%, and 100% and 46%, respectively.

CONCLUSION

This study found that BPB can produce sufficient differential nerve dysfunction to allow adequate evaluation of the diagnostic test attributes of SSEPs as a nerve monitor. The results of this study may stimulate further work on refining intraoperative nerve dysfunction models and diagnostic nerve function monitors.

TRIAL REGISTRATION

www.clinicaltrials.gov (NCT03409536); registered 24 January 2018.

Combined score based on arterial lactate, aspartate transaminase and prolonged capillary refill time is a useful diagnostic criterion for identifying severe dengue

BACKGROUND

Taking into consideration, the variable performance of WHO's dengue case definition and the magnitude of epidemics in India, a score based on clinical and laboratory parameters is required for the early identification of severe dengue.

METHODS

A retrospective observational study of children (aged ≤12 y) presenting with dengue, defined as per the WHO 2009 classification and NS1 antigen/IgM ELISA positivity, was conducted at a tertiary care hospital from 2013 to 2015. Clinical laboratory parameters were compared between severe/non-severe dengue using univariate and multivariate analysis. Areas under receiver operating characteristic curves (AUROCs), sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were obtained for independent and composite markers.

RESULTS

Of 135 dengue patients, 46 (34.1%) had non-severe dengue and 89 (65.9%) had severe dengue. Logistic regression determined prolonged capillary refill time (CRT), lactate ≥2.9 mmol/L and serum aspartate transaminase (AST) ≥135 IU/L as predictive for severe dengue. AUROCs of lactate, AST and combined score incorporating AST, lactate and prolonged CRT for identifying severity were 7.55, 7.23 and 8.5, respectively. The combined score cut-off ≥1 had 87.6% sensitivity, 65.2% specificity, 83% PPV and 73.2% NPV. The combined score cut-off ≥3 had 100% specificity and 100% PPV.  However, AST >135 IU/L and lactate >2.9 mmol/L together had 97.8% specificity and 97.1% PPV for identifying severity.

CONCLUSIONS

The presence of either 'prolonged capillary refill time with one deranged biochemical parameter' or 'both deranged biochemical parameters' is nearly 100% specific for severity of dengue.

Extended ex vivo normothermic perfusion for preservation of vascularized composite allografts

Ischemia and reperfusion injury remains a significant limiting factor for the successful revascularization of amputated extremities. Ex vivo normothermic perfusion is a novel approach to prolong the viability of the amputated limbs by maintaining physiologic cellular metabolism. This study aimed to evaluate the outcomes of extended ex vivo normothermic limb perfusion (EVNLP) in preserving the viability of amputated limbs for over 24 hours. A total of 10 porcine forelimbs underwent EVNLP. Limbs were perfused using an oxygenated colloid solution at 38°C containing washed RBCs. Five forelimbs (Group A) were perfused for 12 hours and the following 5 (Group B) until the vascular resistance increased. Contralateral forelimbs in each group were preserved at 4°C as a cold storage control group. Limb viability was compared between the 2 groups through assessment of muscle contractility, compartment pressure, tissue oxygen saturation, indocyanine green (ICG) angiography and thermography. EVNLP was performed for 12 hours in group A and up to 44 hours (24-44 hours) in group B. The final weight increase (-1.28 ± 8.59% vs. 7.28 ± 15.05%, P = .548) and compartment pressure (16.50 ± 8.60 vs. 24.00 ± 9.10) (P = .151) were not significantly different between the two groups. Final myoglobin and CK mean values in group A and B were: 875.0 ± 325.8 ng/mL (A) versus 1133.8 ± 537.7 ng/mL (B) (P = .056) and 53 344.0 ± 16 603.0 U/L versus 64 333.3 ± 32 481.8 U/L (P = .286). Tissue oxygen saturation was stable until the end in both groups. Infra-red thermography and ICG-angiography detected variations of peripheral limb perfusion. Our results suggest that extended normothermic preservation of amputated limbs is feasible and that the outcomes of prolonged EVNLP (>24 hours) are not significantly different from short EVNLP (12 hours).

Arterial vs venous lactate: Correlation and predictive value of mortality of patients with sepsis during early resuscitation phase

PURPOSE

To compare the lactate concentrations obtained from venous to those obtained from arterial blood in predicting hospital mortality of patients with sepsis and septic shock. To also assess lactate clearance as predictor for mortality.

METHODS

100 patients with septic shock were prospectively enrolled. Serum was sampled at baseline and after 6 h of resuscitation from arterial and venous lines. Demographic, severity indices, hemodynamic measures as well as lactate clearance levels were noted. Data were analyzed for bias and precision.

RESULTS

There was correlation between venous and arterial lactate concentrations at the baseline (R = 0.68) and at the 6-hour time point (R = 0.95). Venous concentrations were consistently higher than those obtained from an arterial access by 0.684 mg/dL. Further, arterial lactate level > 3.2 mmol/L and clearance of <20% were considered the cutoff for the mortality risk. While only 8% of the patients with no risk died, all 20 patients who had lactate level > 3.2 mmol/L and clearance of <20% died within the hospital.

CONCLUSION

Our data suggests a strong correlation between arterial and peripheral venous the lactate levels and in the initial phase of resuscitation in septic shock patients we can use venous lactate level as biomarker instead of arterial lactate level. The study also showed that combining lactate levels and its clearance is a reliable predictor of mortality in sepsis.

Clinical use of plasma lactate concentration. Part 1: Physiology, pathophysiology, and measurement

OBJECTIVE

To review the current literature with respect to the physiology, pathophysiology, and measurement of lactate.

DATA SOURCES

Data were sourced from veterinary and human clinical trials, retrospective studies, experimental studies, and review articles. Articles were retrieved without date restrictions and were sourced primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection.

HUMAN AND VETERINARY DATA SYNTHESIS

Lactate is an important energy storage molecule, the production of which preserves cellular energy production and mitigates the acidosis from ATP hydrolysis. Although the most common cause of hyperlactatemia is inadequate tissue oxygen delivery, hyperlactatemia can, and does occur in the face of apparently adequate oxygen supply. At a cellular level, the pathogenesis of hyperlactatemia varies widely depending on the underlying cause. Microcirculatory dysfunction, mitochondrial dysfunction, and epinephrine-mediated stimulation of Na⁺ -K⁺ -ATPase pumps are likely important contributors to hyperlactatemia in critically ill patients. Ultimately, hyperlactatemia is a marker of altered cellular bioenergetics.

CONCLUSION

The etiology of hyperlactatemia is complex and multifactorial. Understanding the relevant pathophysiology is helpful when characterizing hyperlactatemia in clinical patients.

Early postictal serum lactate concentrations are superior to serum creatine kinase concentrations in distinguishing generalized tonic-clonic seizures from syncopes

Concentrations of serum creatine kinase (CK) and serum lactate are frequently measured to help differentiate between generalized tonic-clonic seizures (GTCS) and syncope. The aim of this prospective cohort study was to systematically compare these two markers. The primary outcome is the measurement of serum lactate and CK in blood samples drawn within 2 h of the event in patients admitted with either a GTCS (n = 49) or a syncope (n = 36). Furthermore, the specificity and sensitivity of serum lactate and CK are determined as diagnostic markers in distinguishing between GTCS and syncope. GTCS patients have significantly higher serum lactate levels compared to syncope patients (p < 0.001). In contrast, CK does not differ between groups at admission. Regarding the first hour after the seizure, we identify a cut-off for serum lactate of 2.45 mmol/l for diagnosing GTCS as the cause of an impairment of consciousness with a sensitivity of 0.94 and a specificity of 0.93 (AUC: 0.97; 95% CI 0.94-1.0). In the second hour after the event, the ROC analysis yields similar results (AUC: 0.94; 95% CI 0.85-1.0). Serum lactate is a sensitive and specific diagnostic marker to discriminate GTCS from syncope and is superior to CK early after admission to the emergency department.

Diagnostic value of arterial blood gas lactate concentration in the different forms of mesenteric ischemia

PURPOSE

The role of serum lactate measurement in patients with intestinal ischemia still remains unclear. The aim of this study was to prospectively evaluate the diagnostic performance of arterial blood gas lactate concentrations in the patients with acute mesenteric ischemia and its different forms.

METHODS

All the patients reporting abdominal pain associated with risk factors for mesenteric ischemia underwent arterial blood gas and contrast enhanced abdominal computer tomography (CT).

RESULTS

At CT, 201 patients (70.7%) showed a nonischemic disease (group 1) and 83 patients (29.2%) showed findings of mesenteric ischemia. Out of these, 35 patients (42.1%) showed bowel ischemia secondary to non vascular causes (group 2) and 48 (57.8%) had a vascular intestinal ischemia (group 3). Out of these, 20 showed small bowel arterial occlusion (group 3a), 13 a small bowel nonocclusive ischemia (group 3b), 7 a venous small bowel occlusion (group 3c) and 8 showed isolated colonic ischemia (group 3d). The median lactate serum level was significantly higher in patients with vascular ischemia if compared with patients with nonischemic disease and secondary mesenteric ischemia (p < 0.0001; Kruskal-Wallis test). The areas under ROC curves for the lactate serum levels in the groups 2, 3, 3a, 3b, 3c and 3d were, respectively, 0.61, 0.85, 0.93, 0.93, 0.68 and 0.67.

CONCLUSIONS

Arterial blood gas lactate levels seem to show good diagnostic accuracy in diagnosing small bowel arterial and nonocclusive ischemia and poor accuracy in diagnosing secondary mesenteric ischemia, small bowel venous ischemia and ischemic colitis.

Update: Clinical Use of Plasma Lactate

Lactate is an essential, versatile metabolic fuel in cellular bioenergetics. In human emergency and critical care, lactate is used as a biomarker and therapeutic endpoint and evidence is growing in veterinary medicine supporting its clinical utility. Lactate production is a protective response providing ongoing cellular energy during tissue hypoperfusion or hypoxia and mitigating acidosis. Hence, hyperlactatemia is closely associated with disease severity but it is an epiphenomenon as the body attempts to protect itself. This article reviews lactate biochemistry, kinetics, pathophysiology, some practical aspects of measuring lactate, as well as its use in diagnosis, prognosis, and monitoring.

Less incidence of coronary artery disease in general anesthesia compared to spinal-epidural anesthesia after total knee replacement: 90-day follow-up period by a population-based dataset

Total knee replacement (TKR) is an effective and safe procedure. However, large-scale study to compare the incidence of coronary artery disease (CAD) after spinal or epidural anesthesia (SA-EA) or general anesthesia (GA) for TKR has not ever been conducted. To do so, we studied a population-based dataset from the Taiwan National Health Research Institute and hypothesized that the incidence of CAD might be different with regional than with general anesthesia. The risk of CAD-related events during a 90-day follow-up period among patients who received TKR under SA-EA or GA was evaluated in the present study. A total of 1500 patients from the Taiwan National Health Insurance claims database who underwent TKR from January 1, 2004, to December 31, 2006, were allocated into two groups. Group 1 included 1012 patients who received SA-EA during TKR procedure. Group 2 included 488 patients who received GA during this procedure. The number of patients who developed CAD during the 90-day follow-up period was 31 (3.1 %) in group 1 and 6 (1.2 %) in group 2. The Kaplan-Meier survival analysis of IHD-free cumulative survival rate during the 90-day follow-up period for patients who underwent TKR was significantly lower in group 1 than in group 2. The hazard ratio for the occurrence of CAD was 2.80 (95 % CI 1.16-6.78), and the hazard was higher for patients who received SA-EA than for patients who received GA after adjusted potential confounding factors. After the performance of TKR, patients had a potentially increased risk for CAD in SA-EA compared to GA during the 90-day follow-up period.

Bilateral passive leg raising attenuates and delays tourniquet deflation-induced hypotension and tachycardia under spinal anaesthesia: a randomised controlled trial

BACKGROUND

The pneumatic tourniquet is frequently used in total knee arthroplasty. Tourniquet deflation may result in hypotension and tachycardia caused by the rapid shift of blood volume back to the ischaemic limb and a decrease in cardiac preload. Passive leg raising (PLR) represents a 'self-volume challenge' that can result in an increase in preload. Such a PLR-induced increase in preload was hypothesised to attenuate the decrease in preload resulting from tourniquet deflation.

OBJECTIVE

To evaluate the effect of PLR on hypotension and tachycardia following tourniquet deflation.

DESIGN

A randomised controlled trial.

SETTING

Single medical centre.

PATIENTS

Seventy patients who underwent unilateral total knee arthroplasty were randomised into two groups: tourniquet deflation with PLR (n = 35) or without PLR (control group, n = 35).

INTERVENTION(S)

Patients in both groups were administered a single dose of plain bupivacaine for spinal anaesthesia. The pneumatic tourniquet was inflated on the thigh and the surgery was performed. The study composed of four steps: for the PLR group, step 1 - inflation of the tourniquet while the patient was supine; step 2 - the patient's legs were raised to a 45° angle; step 3 - the tourniquet was deflated while the patient's legs were still raised; and step 4 - the legs were returned to the supine position. In the control group, the same perioperative procedure was used, but PLR was not conducted.

MAIN OUTCOME MEASURES

The patients' blood pressure and heart rate were measured before, during and after tourniquet deflation.

RESULTS

After tourniquet deflation, the magnitude of the changes in blood pressure and heart rate was less in the PLR group than that in the control group. In addition, the blood pressure nadir also occurred later in the PLR group than in the controls.

CONCLUSION

Bilateral PLR is a simple, reversible manoeuvre that mimics rapid fluid loading. Bilateral PLR attenuates the severity of, and delays the time to, hypotension and tachycardia following deflation of a lower limb tourniquet.

TRIAL REGISTRATION

ClinicalTrials.gov number NCT01592669.

Heterotopic ischemic pain attenuates somatosensory evoked potentials induced by electrical tooth stimulation: Diffuse noxious inhibitory controls in the trigeminal nerve territory

The purpose of this study was to determine whether the late component of somatosensory evoked potentials (SEP) induced by electrical tooth stimulation and pain intensity are inhibited by heterotopic ischemic stimulation. The tourniquet pressure with 50 mmHg greater than the individual's systolic pressure was applied to the left upper arm for 10 min as ischemic conditioning stimulation. The late component of SEP and visual analogue scale (VAS) were recorded at 4 times and both were significantly decreased when ischemic conditioning stimulation was applied. The maximum reductions in SEP amplitude and the VAS value were 26.1% and 21.2%, respectively, during ischemic conditioning stimulation. After-effect was observed 5 min after removal of the conditioning stimulation. The present study revealed that heterotopic ischemic stimulation attenuated the late component of SEP induced by electrical tooth stimulation, triggering diffuse noxious inhibitory controls (DNIC) and after-effects in the trigeminal nerve territory. It was also suggested that the DNIC effect differs, depending on the intensity, kind, and quality of the test and conditioning stimuli.

Upper extremity regional anesthesia: essentials of our current understanding, 2008

Brachial plexus blockade is the cornerstone of the peripheral nerve regional anesthesia practice of most anesthesiologists. As part of the American Society of Regional Anesthesia and Pain Medicine's commitment to providing intensive evidence-based education related to regional anesthesia and analgesia, this article is a complete update of our 2002 comprehensive review of upper extremity anesthesia. The text of the review focuses on (1) pertinent anatomy, (2) approaches to the brachial plexus and techniques that optimize block quality, (4) local anesthetic and adjuvant pharmacology, (5) complications, (6) perioperative issues, and (6) challenges for future research.

Delayed recovery and late development of complex regional pain syndrome in patients with an isolated fracture of the distal radius: prediction of a regional inflammatory response by early signs

We studied prospectively the regional inflammatory response to a unilateral distal radial fracture in 114 patients at eight to nine weeks after injury and again at one year. Our aim was to identify patients at risk for a delayed recovery and particularly those likely to develop complex regional pain syndrome. In order to quantify clinically the inflammatory response, a regional inflammatory score was developed. In addition, blood samples were collected from the antecubital veins of both arms for comparative biochemical and blood-gas analysis. The severity of the inflammatory response was related to the type of treatment (Kruskal-Wallis test, p = 0.002). A highly significantly-positive correlation was found between the regional inflammatory score and the length of time to full recovery (r(2) = 0.92, p = 0.01, linear regession). A regional inflammatory score of 5 points with a sensitivity of 100% but a specificity of only 16% also identified patients at risk of complex regional pain syndrome. None of the biochemical parameters studied correlated with regional inflammatory score or predicted the development of complex regional pain syndrome. Our study suggests that patients with a distal radial fracture and a regional inflammatory score of 5 points or more at eight to nine weeks after injury should be considered for specific anti-inflammatory treatment.

Use of somatosensory evoked potentials to detect peripheral ischemia and potential injury resulting from positioning of the surgical patient: case reports and discussion

BACKGROUND

Somatosensory evoked potentials (SSEPs) have long been recognized as an excellent tool for detecting neural and vascular compromise during vascular, neurosurgical and orthopedic procedures. SSEPs have the ability to localize, central versus peripheral, the area of compromise. Many surgeons use only lower-limb SSEP monitoring when performing lumbar spinal surgery. The upper extremities are usually not monitored during such procedures, and monitoring oxygen saturation does not detect neural compromise.

PURPOSE

To report that the expanded use of SSEP monitoring during surgery can be beneficial in detecting peripheral ischemia or neural compromise resulting from positioning.

STUDY DESIGN

Three case reviews of orthopedic spine surgeries where SSEP monitoring provided early warnings of vascular and neural compression.

METHODS

The cases review three different lumbar procedures in which evidence of peripheral ischemia and nerve compression were detected by SSEP monitoring.

RESULTS

By the use of upper- and lower-extremity monitoring during lumbar procedures, early detection of ischemia and nerve compression were noted intraoperatively. These changes prompted examination of the patient and repositioning to correct the ischemia or compression. The repositioning in these cases corrected the problem, and no lasting effects were found.

CONCLUSIONS

Including SSEP monitoring of the bilateral upper extremities should be considered during lumbar spinal procedures. Such monitoring can be offered for a slightly increased expense and only minimal time delay to place the additional required electrodes by the technician. As a direct result of the early warning of the SSEP monitoring, we were able to avoid potential ischemic injuries and improve patient outcomes.

Oral Clonidine Premedication Exacerbates Hypotension Following Tourniquet Deflation by Inhibiting Noradrenaline Release

Clonidine premedication prevents tourniquet pain and reduces sympathetic nerve activity. We evaluated hemodynamic changes and catecholamine release following tourniquet deflation during spinal anesthesia in patients who received oral clonidine premedication. The final analysis included 24 otherwise healthy patients undergoing lower-limb surgery randomly assigned to two groups: those receiving approximately 5 micrograms/kg of oral clonidine 1 hr before anesthesia (clonidine group, n = 12), and those receiving no premedication (control group, n = 12). After lumbar anesthesia, a tourniquet was applied for approximately 60 minutes to each patient. Electrocardiogram, arterial blood pressure, and consumption of butorphanol for tourniquet pain were monitored. Blood samples were obtained at different times to measure serum concentration of catecholamine. In the clonidine group, mean blood pressure decreased from 87 +/- 7 mmHg at baseline to 65 +/- 10 mmHg after tourniquet deflation (P < 0.05). This peak reduction of mean blood pressure in the clonidine group was significantly lower than in the control group. After receiving clonidine premedication, the plasma noradrenaline concentrations in the clonidine group were significantly lower than those in the control group. Noradrenaline concentration increased in the control group from 162.3 +/- 89.2 pg/mL before tourniquet deflation to 199.3 +/- 95.7 pg/mL afterward (P < 0.01), but there was no significant change in noradrenaline concentration after tourniquet deflation in the clonidine group. We conclude that oral clonidine premedication exacerbated the reduction in mean blood pressure following tourniquet deflation by inhibiting noradrenaline release.

Scalp-recorded contingent negative variation (CNV) increases during experimentally induced sustained ischemic pain in humans

Contingent negative variations (CNV) after acoustic stimuli (S1) followed by optical ones (S2) were recorded using electroencephalography in 22 healthy students both under control conditions and during ischemic pain to study the effects of sustained pain on CNV. Mean negative CNV-amplitudes and integrated areas below CNV were significantly larger during periods of ischemic pain than under control conditions (16.53 versus 13.11 microV, respectively (P=0.0028) and 8.318 versus 6.357 microV*s, respectively (P=0.00071)). We conclude that deep somatic pain augments CNV. Reduced CNV amplitudes occurring during migraine attacks, however, reflect other mechanisms which may mask the effects of migraine headache on CNV.

Neurovascular complications of knee arthroscopy

During the last 3 decades, arthroscopy has revolutionized the way knee surgery is performed. The indications and the applications of arthroscopic procedures in the knee joint have enormously increased with the improvement in surgical technique and advent of new arthroscopic equipment. The use of arthroscopic techniques has led to a significant decrease in morbidity for the patient with intraarticular abnormalities, in terms of both diagnosis and surgical correction. Even though knee arthroscopy is a minimally invasive procedure with relatively low morbidity, it is not without risk of complications, of which neurovascular complications are among the most serious and devastating. The reported incidence of neurovascular complication is low, but it may be underestimated. Many neurovascular complications that occur are preventable with a thorough understanding of neurovascular anatomy, good preoperative and intraoperative planning, and attention to the details of basic techniques and the equipment used for the procedure. It is imperative that the surgeon who is performing arthroscopy be aware of these neurovascular complications, recognize them as early as possible, and initiate further evaluation and treatment as expeditiously as possible. In this article, the causes, management, prevention, and medicolegal implications of neurovascular complications of knee arthroscopy are reviewed.

Anaesthesia for procedures of the hand and elbow

The majority of upper extremity surgeries are performed on an ambulatory basis under intravenous regional anaesthesia or brachial plexus blockade. The former technique is easy to perform, has a rapid onset and a high success rate but provides limited post-operative analgesia. Brachial plexus blockade provides excellent intraoperative anaesthesia as well as post-operative analgesia, eliminates the need for post-operative opioids, resulting in a decrease in recovery time, shortened hospital stay, increased patient satisfaction and ultimately a decrease in perioperative costs when compared with general anaesthesia. This chapter reviews upper extremity surgical procedures performed below the shoulder, the anaesthetic options available, and techniques used to optimize post-operative pain control.

Femoral artery ischemia during spinal scoliosis surgery detected by posterior tibial nerve somatosensory-evoked potential monitoring

STUDY DESIGN

A case report of unilateral leg ischemia caused by femoral artery compression detected using posterior tibial nerve somatosensory-evoked potentials during spinal scoliosis instrumentation surgery.

OBJECTIVES

To report a rare cause of intraoperative unilateral loss of all posterior tibial nerve somatosensory-evoked potential waveforms.

SUMMARY OF BACKGROUND DATA

Failure to obtain adequate popliteal fossa, spinal, subcortical, and cortical potentials during posterior tibial nerve somatosensory-evoked potential spinal cord monitoring usually results from technical factors or chronic conditions affecting the peripheral nerve.

METHODS

A 16-year-old boy with thoracic scoliosis had normal posterior tibial nerve somatosensory-evoked potentials both before surgery and in the operating room immediately after anesthesia induction and prone positioning on a four-post spinal frame.

RESULTS

One hour after the start of surgery, a minimal amplitude reduction of the right popliteal fossa potentials appeared. Fifteen minutes later, the amplitudes of the popliteal fossa, subcortical, and cortical potentials evoked by right posterior tibial nerve stimulation became substantially reduced. Subsequently, all waveforms were lost. Malfunction of the right posterior tibial nerve stimulator was initially suspected, but when proper function was verified, a search for other causes of this loss led to discovery of leg ischemia. The patient was repositioned on the spinal frame, and all posterior tibial nerve somatosensory-evoked potentials waveforms began to reappear 7 minutes later. There was no postoperative clinically detectable complication.

CONCLUSIONS

Although technical malfunction should always be suspected when all intraoperative somatosensory-evoked potential waveforms are initially seen and subsequently lost, one should also consider the possibility that intraoperative ischemia due to limb positioning could be the etiology.

The effects of dilute epinephrine saline irrigation on the need for tourniquet use in routine arthroscopic knee surgery

A prospective, randomized, double-blinded study was performed to determine whether dilute epinephrine saline irrigation (1 mg/l) delivered by gravity flow would significantly reduce the need for tourniquet use during routine arthroscopic surgery. One hundred five patients requiring straightforward arthroscopic knee surgery were randomly assigned to either an epinephrine group that received dilute epinephrine irrigation by gravity flow or to a placebo group that received normal saline irrigation by gravity flow. The need for tourniquet use and the tourniquet time, total operative time, and volume of irrigation fluid used were documented and compared between the two groups. A tourniquet was required 50% less often in the epinephrine group than in the placebo group. This difference was found to be statistically significant using the Student's t-test (P < 0.008, alpha < or = 0.05). If a tourniquet was required, the presence of dilute epinephrine in the irrigation fluid did not affect the overall tourniquet time or the ratio of tourniquet time to total operative time. We believe this study proved that dilute epinephrine irrigation is effective in decreasing the need for tourniquet use during routine arthroscopic knee surgery.

Changes in oxygen consumption and carbon dioxide elimination after tourniquet release in patients breathing spontaneously under epidural anesthesia

To examine whether the degree of the changes in metabolic variables correlates with the duration of tourniquet inflation or other factors in spontaneously breathing patients undergoing unilateral lower-limb surgery under epidural anesthesia, we measured changes in metabolic variables. Metabolic variables consisted of oxygen consumption (VO2), carbon dioxide elimination (VCO2), and respiratory quotient (RQ). The patients (n = 30) received continuous epidural anesthesia with 1.5% lidocaine with epinephrine solution (5 micrograms/mL). The averaged values of VO2 and VCO2 for 10 min after tourniquet release increased significantly from 171.2 +/- 34.5 mL/min to 262.7 +/- 90.0 mL/min and from 202.0 +/- 33.1 mL/min to 250.5 +/- 64.2 mL/min, respectively. They returned to the baseline values within 10 min after deflation. Therefore, rapid response to changes in metabolic condition can be anticipated after tourniquet release in patients breathing spontaneously under epidural anesthesia. The percent increases in the averaged values of VO2 and VCO2 for 10 min after tourniquet release were correlated with body surface area but not with tourniquet inflation time. We conclude that the changes in metabolic variables after tourniquet release are dependent on body size, i.e., muscle mass, but not on the duration of tourniquet inflation.

IMPLICATIONS

We measured changes in metabolic variables, i.e., oxygen consumption and carbon dioxide elimination, after tourniquet release in patients undergoing lower-limb surgery under epidural anesthesia. We found that the extent of changes in these variables was dependent on body size but not on the duration of inflation. These results have implications as to how long a tourniquet can be inflated during surgery.

[Pneumatic tourniquets in orthopedics]

Pneumatic tourniquets, often used to provide a bloodless operating field, carry a risk of adverse effects. Limb exsanguination by gravitation is less aggressive than by mechanical means. Skin, muscles, nerves and vessels suffer maximally under tourniquet because of mechanical pressure, with both a sagittal force, responsible for compression and an axial force responsible for stretchening. All parts of the limb are therefore affected by ischaemia. The restarting of circulation will also increase lesions at the microcirculatory level, responsible for the "no reflow" phenomena. Transient reperfusion intervals are not necessarily beneficial. These effects will significantly contribute to the post tourniquet sensory motor injuries. The tourniquet increases the risk of sepsis. Tourniquet release allows metabolites from the leg to enter into the circulation, and also carries a risk of pulmonary thromboembolism. Carbon dioxide is eliminated by spontaneous hyperventilation under regional anaesthesia. If not eliminated by an increase of mechanical ventilation during general anaesthesia, it may raise intracranial pressure in head trauma patients. Various chemotactic and cytolytic agents may cause lung injury. Mobilization of blood volume at tourniquet placement and release may have detrimental haemodynamic effects in patients with coronary or cardiac insufficiency. The tourniquet increases arterial pressure after 20 to 25 minutes under general anaesthesia. Regional anaesthesia is considered as the technique of choice for the prevention of "tourniquet hypertension", closely linked to pain and relievable by local anaesthetics. Tourniquet modifies also the pharmacokinetics of anaesthetic and other agents. It generates hyperthermia, especially in children. Prospective and comparative studies did not show any advantage as far as duration of surgery and amount of blood loss are concerned. In order to minimize its side effects, the tourniquet must be used within the frame of a strict procedure, with a well adapted and regularly checked equipment. Duration of ischaemia should be as short as possible and not continue for more than two hours, with a reperfusion of 15 minutes every hour. Local hypothermia seems to be a safe means for decreasing side effects.

Venous blood gas analysis for evaluation of blood circulation of the hand during continuous axillary block

Computer analysis of blood gas measurements was used to evaluate the effect of a continuous axillary block on the circulation of the hand of a patient suffering from regional circulatory insufficiency due to ligation of the brachial artery. Venous blood samples drawn from the cephalic vein were analysed at 0, 1, 2.5 and 18 hours after the blockade. Improved circulation of the hand was indicated by decreased arterio-venous oxygen difference and increased venous oxygen partial pressure following the blockade. The advantage in using the extended blood gas analysis is the possibility of estimating the main factors influencing tissue oxygenation: oxygen capacity, oxygen partial pressure and the haemoglobin oxygen affinity.

Changes in end-tidal CO2 level following tourniquet deflation during orthopedic surgery

We studied the changes in end-tidal CO(2) (ET(CO)(2)) and systemic responses after tourniquet deflation in spontaneously breathing and ventilation-controlled patients during orthopedic surgery of both the upper and/or the lower extremities. In most patients, increases in ET(CO)(2), heart rate, and Pa(CO)(2), as well as decreases in blood pressure and pH were observed. In every spontaneously breathing patient, the respiratory rate began to increase before the ET(CO)(2) reached a maximum. Arterial blood gas analysis suggested that the increase in ET(CO)(2) closely reflected the increase in Pa(CO)(2). Our study yielded new information on the ET(CO)(2) changes as follows: 1) the time for ET(CO)(2) level to reach a peak (peak time) was almost constant despite the considerable differences in the increases in ET(CO)(2) both in spontaneous breathing and ventilation-controlled groups and the peak time in the former group was shorter than that in the latter group; and 2) it was suggested that the increase in ET(CO)(2) in the spontaneously breathing patients was smaller than that in ventilation-controlled patients when both patients were subjected to the same conditions on tourniquet time and tourniqueted area. Our data showed that the increase in ET(CO)(2) (or Pa(CO)(2)) can be large and prolonged in some situations. Thus, we recommend continuous ET(CO)(2) monitoring and the proper hyperventilation at tourniquet deflation in order to minimize any adverse effects of acidosis.

Does tourniquet use during anterior cruciate ligament surgery interfere with postsurgical recovery of function? A review of the literature

This article explores the issue of whether use of a tourniquet during arthroscopically assisted repair of the anterior cruciate ligament (ACL) slows the postoperative recovery of function. A tourniquet is customarily used to provide a bloodless field, thus enabling the surgeon to visualize the joint clearly. However, there is increasing evidence that tourniquets cause muscle and nerve damage that can have long-term consequences for the recovery of function following surgery. The two randomized trials that investigated tourniquet use during meniscectomy reached contradictory conclusions about the effects of the tourniquet. There have been no randomized trials of tourniquet use during the longer and more complex ACL surgery. This article reviews the pertinent literature and suggests some clinical implications of the available information.