Thigh Tourniquet Research Articles

Spinal 2-Chloroprocaine: The Effect of Added Dextrose

Spinal 2-chloroprocaine is being investigated as an alternative short-acting spinal anesthetic to replace lidocaine for outpatient surgery. Adding dextrose increases the baricity of solutions and alters the characteristics of spinal anesthesia. In this study, we compared 2-chloroprocaine spinal anesthesia performed with or without the addition of dextrose (1.1%). Eight volunteers underwent 2 spinal anesthetics, receiving 40 mg 2-chloroprocaine (2 mL, 2%) with 0.25 mL saline with one and 0.25 mL 10% dextrose with the other in a double-blinded, randomized, balanced crossover manner. Pinprick anesthesia, tolerance to transcutaneous electrical stimulation, and tourniquet, motor strength measurements, and time to ambulation and void were assessed. Postvoid residual bladder volume was measured via ultrasound. Spinal anesthesia was successful in all subjects and regressed within 110 (80-110) min. There was no significant difference in peak height T4 (T7-C6), time to achieve peak block height (14 +/- 6 min), time for 2-segment regression (44 +/- 9 min), regression to L1 (66 +/- 12 min), tolerance of tourniquet (43 +/- 9 min), or return of motor function (81 +/- 14 min). Mean postvoid residual volume was larger with dextrose (74 +/- 67 mL versus 16 +/- 35 mL; P = 0.02). No subject reported signs of transient neurologic symptoms (TNS). In conclusion, spinal 2-chloroprocaine provides adequate potency with reliable regression, seemingly without TNS. Adding dextrose does not significantly alter spinal block characteristics but increases residual bladder dysfunction. Therefore, the addition of glucose to 2-chloroprocaine for spinal anesthesia is not necessary. Spinal chloroprocaine provides adequate potency with reliable regression, seemingly without concerns of transient neurologic symptoms, and hence an appealing profile for outpatient surgery. The addition of dextrose does not alter peak block height or tolerance of thigh tourniquet, and increases the degree of residual bladder dysfunction.

Above ankle tourniquets in young and adolescent children foot surgery

We undertook a prospective study of 53 consecutive foot surgery under general anesthesia in young and adolescent children over a 4.5-year period to assess the safety and efficacy of above ankle tourniquet in the surgery of certain pediatric foot disorders. The average age was 8.4 (1–14) years. The tourniquet pressure used ranged from 200–225 mmHg (average 217.92 mmHg). The average duration of tourniquet ischemia was 39.7 min (6–73 min). There were no post-operative complications noted with ankle cuffs. No patient has neurological complications. The above ankle tourniquet was a safe and effective means in providing a bloodless field for foot surgery in children, and provides a suitable alternative to the routine use of a thigh tourniquet in children.

Duplex Saphenous Vein Mapping: Venous Occlusion and Dependent Position Facilitate Imaging

The purpose of this study was to develop an optimal technique for greater saphenous vein distention during preoperative duplex assessment. An Acuson 128 scanner with a 7.5-MHz sector probe was used to assess the effects of venous occlusion and dependent position on the diameter of the greater saphenous vein in 20 male volunteers. The greater saphenous vein was imaged 10 cm above and 10 cm below the knee with the subject lying horizontal, horizontal with a thigh tourniquet inflated to 40 mm Hg, inclined at 15 degrees of reversed Trendelenburg, and inclined at 15 degrees of reversed Trendelenburg combined with the tourniquet inflated to 40 mm Hg. Maximal vein diameters and circumferences were measured by a sonographer blinded to the conditions of vein measurement to avoid interpretation bias. Using a t test assuming equal variances, the increases in vein circumferences and diameters achieved by dependency and tourniquet combined were significantly greater than those achieved by dependency alone (p=0.004). The technique of dependency combined with tourniquet inflation to 40 mm Hg facilitates greater saphenous vein imaging and provides an optimal method of venous distention.

Popliteal Block as an Alternative to Labat’s Approach

Popliteal Block as an Alternative to Labat’s Approach In Response: We would like to thank Dr. Fernàndez-Guisasola for his interest in our work (1) as well as his practical comments, which remind us once more, if needed, that the sciatic nerve can be blocked at several levels along its pathway with a lot of “different” posterior and lateral approaches. Popliteal blocks undoubtedly provide a good and effective anesthesia (2,3). In our daily practice we use them frequently, not only for single shot blockades but also for postoperative pain relief, by placing a perineural catheter close to the sciatic nerve and infusing it with local anesthetic solutions after surgery (4). Nonetheless, Dr. Fernàndez-Guisasola should recognize that the aim of our study was “to describe a new posterior approach to the sciatic nerve at the level of the proximal thigh and compare…the effectiveness, performance time, and patient’s acceptance of this new approach with the classic posterior approach”(1). In fact, results of our study demonstrated that this new posterior approach is easier and less painful to the patient as compared to the classic Labat’s approach only. This allows us to suggest that the subgluteus sciatic nerve block can be considered a useful alternative to Labat’s approach, but we never stated that the sublguteus posterior block is the best alternative to the Labat’s approach, disregarding the popliteal blocks. On the other hand, we must also consider that the Dr. Fernàndez-Guisasola’s hypothesis that the posterior popliteal block is easier than other approaches in the obese patient is as much theoretical as intriguing, and it is not supported by properly conducted, randomized studies. Irrespective from discussing the distribution of adipose tissues in the obese patient, what about turning prone an obese patient to place the block and then turning it back to the supine position? Further, very often a more proximal approach than the popliteal one is required because of surgical site (e.g., surgery at the level of the knee) or surgeon’s needs (e.g., thigh tourniquet). However, this is a matter of other new studies, and we look forward to reading them to better understand the best indication for each approach to the sciatic nerve according to both patient and surgery. In conclusion, we completely agree with Dr. Fernandez-Guisasola that the physician must choose and titrate the best nerve block according to patient characteristics, the type of surgery, and the surgeon’s needs. However, personal skills and expertise also play an important role: the more techniques we know and practice, the more flexible is our practice, helping us to get all the benefits of peripheral nerve blocks in different clinical situations. In this view, the description of our new posterior approach to the sciatic nerve is only an attempt to improve the comfort of both the patient and physician when a proximal sciatic nerve block is required: just another arrow in our quiver. Andrea Casati, MD Pia di Benedetto, MD

Epidural Morphine Delays the Onset of Tourniquet Pain During Epidural Lidocaine Anesthesia

We conducted a randomized, double-blinded study to examine the onset time of tourniquet pain during epidural lidocaine anesthesia either with or without morphine in the epidural solution. Forty-five patients undergoing knee surgery with a thigh tourniquet were randomly allocated into 3 groups of 15 patients each: epidural morphine (EM; epidural administration of 17 mL of 2% lidocaine plus 2 mg of morphine, followed by IV injection of 0.2 mL of normal saline), IV morphine (IVM; 17 mL of 2% lidocaine plus 0.2 mL of normal saline, followed by IVM 2 mg IV), and control (17 mL of 2% lidocaine plus 0.2 mL of normal saline, followed by 0.2 mL of normal saline IV). The onset time of tourniquet pain was recorded. The level of sensory block was determined by the pinprick method at the occurrence of tourniquet pain. Hemodynamic changes and side effects of EM were also recorded. The onset time of tourniquet pain from both the epidural injection and the tourniquet inflation were significantly longer in the EM group (103 ± 15 min and 80 ± 15 min, respectively) compared with the IVM group (74 ± 12 min and 50 ± 12 min, respectively;P < 0.05) and the Control group (67 ± 9 min and 45 ± 9 min, respectively;P < 0.05). The level of sensory block at the onset of tourniquet pain and hemodynamic changes were not different among the three groups. Only two and three patients in the EM group complained of nausea/vomiting and pruritus, respectively. Respiratory depression was not observed in any patient. We conclude that epidural injection of the mixture of 2 mg of morphine and 2% lidocaine solution delayed the onset of tourniquet pain during epidural lidocaine anesthesia without significant morphine-related side effects.

Circulatory, respiratory and metabolic changes after thigh tourniquet release in combined epidural-propofol anaesthesia with preservation of spontaneous respiration.

Twelve elderly patients undergoing total knee arthroplasty received lumbar epidural anaesthesia and propofol infusion at 5 mg.kg(-1).h(-1) following a 1.5-2.0 mg.kg(-1) bolus dose with preservation of spontaneous respiration via a laryngeal mask airway. Circulatory, respiratory and metabolic variables were measured before and 1, 3, 5, 15 and 30 min after release of a pneumatic thigh tourniquet. The blood pressure was decreased at all time-points and the respiratory rate increased at 1 min. The P(a)CO(2) was increased only at 1 min. Arterial blood pH and base excess were decreased at 1 and 3 min and 1, 3 and 5 min, respectively. Arterial blood lactate levels were increased at all times. These characteristics were considered to be identical to those under regional anaesthesia with conscious spontaneous respiration, showing that spontaneous respiration under this anaesthetic regimen has a similar respiratory capacity to that of conscious spontaneous respiration.

Localized abdominal pain following sympathetic blockade with bretylium for the management of complex regional pain syndrome

Localized abdominal pain following sympathetic blockade with bretylium for the management of complex regional pain syndrome

Hyperbaric Spinal Levobupivacaine: A Comparison to Racemic Bupivacaine in Volunteers

Levobupivacaine is the isolated S-enantiomer of bupivacaine and may be a favorable alternative to spinal bupivacaine. However, its clinical efficacy relative to bupivacaine and its dose-response characteristics, in spinal anesthesia, must first be known. This double-blinded, randomized, cross-over study was designed to compare the clinical efficacy of hyperbaric levobupivacaine and bupivacaine for spinal anesthesia. Eighteen healthy volunteers were randomized into three equal groups to receive two spinal anesthetics, one with bupivacaine and the other with levobupivacaine, of equal-milligram doses (4, 8, or 12 mg). We assessed blockade quality and duration with pinprick, transcutaneous electrical stimulation, thigh tourniquet, abdominal and quadriceps muscle strength, modified Bromage scale, and time until achievement of discharge criteria. Sensory and motor block were similar between the same doses of levobupivacaine and bupivacaine (P > 0.56 to 0.86). For example, in the 12-mg groups of levobupivacaine versus bupivacaine, mean duration of tolerance to transcutaneous electrical stimulation at T12 was 100 min for both. The duration of motor block at the quadriceps was 71 versus 73 min, and time until achievement of discharge criteria was 164 min for both. Hyperbaric spinal levobupivacaine has equivalent clinical efficacy to racemic bupivacaine for spinal anesthesia in doses from 4 to 12 mg.

Peripheral or central nerve blocks for foot surgery: a prospective, randomized clinical comparison

The efficacy of surgical anaesthesia and postoperative analgesia after elective orthopaedic foot surgery was evaluated in 200 healthy patients, randomly allocated to receive either a bilateral spinal anaesthesia (group BSA, n = 50), a unilateral spinal anaesthesia (group USA, n = 50), or a combined sciatic-femoral nerve block performed with 2% mepivacaine (group SFM, n = 50) or 0.75% ropivacaine (group SFR, n = 50). Similar duration of surgery was reported in the four groups (median 50 min, range 20–90 min), without differences in times of thigh tourniquet. Surgeon satisfaction was 92% in group SFM and 90% in group SFR, 94% in group BSA and 94% in group USA ( P = 0.18). Tourniquet pain during surgery was reported in two SFM patients and three SFR patients, while two patients in each group required anaesthetic implementation. No urinary retention was reported in SFM and SFR groups, but seven BSA patients (14%) and one USA patient (2%) required bladder catheterization ( P = 0.005). Postoperative analgesia was longer in group SFR (13.4 h) than in the SFM (4.6 h), BSA (3.1 h), and USA (3.2 h) groups ( P = 0.0005), with reduced analgesic consumption ( P = 0.0005). When providing anaesthesia for foot and ankle procedures, the combination of sciatic and femoral nerve blocks is as effective and safe as spinal anaesthesia with less urinary retention. Longer postoperative analgesia is provided by ropivacaine than mepivacaine.

Effects of limb elevation and increased intramuscular pressure on human tibialis anterior muscle blood flow.

The effects of limb elevation and increased intramuscular pressure (IMP) on blood flow in the tibialis anterior muscle and leg neuromuscular function were studied in eight healthy subjects. Muscle blood flow (MBF) was measured by photoplethysmography using a custom-designed probe. IMP was elevated bilaterally by vein obstruction (60-65 mmHg) lasting 30 min induced by a thigh tourniquet of casted legs. Skin sensibility of the feet and the amplitude and area of the compound muscle action potentials from the extensor digitorum brevis muscle were evaluated. The subject kept one leg elevated 32 cm above heart level and the contralateral leg at heart level. All recordings were made before, during and after vein obstruction. IMP increased to 40 mmHg in the vein-obstructed casted legs. Perfusion pressure decreased from [mean (SD)] 42 (5.8) mmHg to 17 (6.4) mmHg in the elevated leg and from 65 (9.9) mmHg to 43 (8.4) mmHg in the non-elevated leg. MBF decreased by 50% in the elevated leg and by 42% in the non-elevated leg. Subjects experienced sensory dysfunction and muscular weakness in the elevated leg. In conclusion, increased IMP, induced by venous obstruction of a casted leg, reduced perfusion pressure and MBF, and resulted in a diminished amplitude and area of the compound muscle action potentials. Limb elevation above heart level combined with venous stasis of a casted leg further reduced perfusion pressure and MBF, and induced sensory dysfunction and muscular weakness.

A non-invasive measure of changes in blood flow in the human anterior tibial muscle.

We used photoplethysmography (PPG) to monitor blood flow changes in the human anterior tibial muscle during arterial occlusion and during isometric and concentric contractions. Single-fibre laser-Doppler flowmetry (LDF) was used as a reference in 12 healthy subjects (5 men, 7 women; mean age 24 years). Post-exercise hyperaemic muscle blood flow (MBF) was measured immediately after isometric dorsiflexion of the ankle joint at maximal contraction for 1 min and full range-of-motion dorsiflexion and plantar flexion of the ankle joint for 1 min. A thigh tourniquet was applied for the evaluation of post-occlusive reactive hyperaemia. The MBF (baseline = 100%) was [mean (SD)] 150 (31)% (P = 0.003) by PPG (880 nm) and 182 (66)% (P = 0.012) by LDF. After 1 min of maximal isometric contraction, MBF increased to 150 (51)% (P = 0.003) by PPG (880 nm) and to 169 (43)% (P = 0.005) by LDF. After 1 min of maximal concentric contractions, MBF increased to 158 (59)% (P = 0.003) by PPG (880 nm) and to 170 (99)% (P = 0.008) by LDF. Skin blood flow, PPG (560 nm), did not change significantly after isometric or concentric contractions. The results indicate that reactive hyperaemia after exercise and arterial occlusion can be assessed in the human anterior tibial muscle using PPG.

Tourniquet-induced wound hypoxia after total knee replacement

We have investigated whether the thigh tourniquet used during total knee replacement (TKR) influenced the development of postoperative wound hypoxia and was a cause of delayed wound healing. We allocated randomly 31 patients (31 TKRs) to one of three groups: 1) no tourniquet; 2) tourniquet inflated at low pressure (about 225 mmHg); and 3) tourniquet inflated to high pressure of about 350 mmHg. Wound oxygenation was measured using transcutaneous oxygen electrodes. In the first week after surgery, patients with a tourniquet inflated to a high pressure had greater wound hypoxia than those with a low pressure. Those without a tourniquet also had wound hypoxia, but the degree and duration were less pronounced than in either of the groups with a tourniquet. Use of a tourniquet during TKR can increase postoperative wound hypoxia, especially when inflated to high pressures. Our findings may be relevant to wound healing and the development of wound infection.

Dose-Response Effects of Spinal Neostigmine Added to Bupivacaine Spinal Anesthesia in Volunteers

Background Intrathecal adjuncts often are used to enhance small-dose spinal bupivacaine for ambulatory anesthesia. Neostigmine is a novel spinal analgesic that could be a useful adjunct, but no data exist to assess the effects of neostigmine on small-dose bupivacaine spinal anesthesia. Methods Eighteen volunteers received two bupivacaine spinal anesthetics (7.5 mg) in a randomized, double-blinded, crossover design. Dextrose, 5% (1 ml), was added to one spinal infusion and 6.25, 12.5, or 50 microg neostigmine in dextrose, 5%, was added to the other spinal. Sensory block was assessed with pinprick; by the duration of tolerance to electric stimulation equivalent to surgical incision at the pubis, knee, and ankle; and by the duration of tolerance to thigh tourniquet. Motor block at the quadriceps was assessed with surface electromyography. Side effects (nausea, vomiting, pruritus, and sedation) were noted. Hemodynamic and respiratory parameters were recorded every 5 min. Dose-response relations were assessed with analysis of variance, paired t tests, or Spearman rank correlation. Results The addition of 50 microg neostigmine significantly increased the duration of sensory and motor block and the time until discharge criteria were achieved. The addition of neostigmine produced dose-dependent nausea (33-67%) and vomiting (17-50%). Neostigmine at these doses had no effect on hemodynamic or respiratory parameters. Conclusions The addition of 50 microg neostigmine prolonged the duration of sensory and motor block. However, high incidences of side effects and delayed recovery from anesthesia with the addition of 6.25 to 50 microg neostigmine may limit the clinical use of these doses for outpatient spinal anesthesia.

Effects of tourniquet compression on neuromuscular function.

Neuromuscular function in New Zealand White rabbits was evaluated after thigh tourniquet compression in the directly compressed quadriceps muscles and the distal tibialis anterior by measuring isometric contractile function after supramaximal stimulation of the motor nerve. Tourniquet compression resulted in markedly decreased force production beneath and distal to the tourniquet. Two days after compression, maximal quadriceps force production was decreased to 46% of control values with 125 mm Hg compression and 21% of control values after 350 mm Hg compression. Maximum tibialis anterior force production declined to 70% of control values after 125 mm Hg thigh compression and 24% of control values after 350 mm Hg thigh compression. Functional deficits were greater in the directly compressed quadriceps muscles, but the quadriceps and tibialis anterior had significantly increased impairment when the tourniquet inflation pressure was increased from 125 mm Hg to 350 mm Hg. Three weeks after compression, quadriceps function had returned to 94% of control value after 125 mm Hg compression and 83% after 350 mm Hg. Tibialis anterior function returned to 88% of control values after 125 mm Hg thigh compression and 83% after 350 mm Hg. Clinically, the use of lower inflation pressures may minimize the complications of tourniquet use and enhance postoperative recovery.

A Double-Blind Comparison of Ropivacaine, Bupivacaine, and Mepivacaine During Sciatic and Femoral Nerve Blockade

A Double-Blind Comparison of Ropivacaine, Bupivacaine, and Mepivacaine During Sciatic and Femoral Nerve Blockade

The Effect of Epinephrine on Small-Dose Hyperbaric Bupivacaine Spinal Anesthesia

The effect of adding epinephrine to small doses of spinal bupivacaine on the duration of sensory motor block has not been carefully investigated.Twelve volunteers underwent hyperbaric bupivacaine spinal anesthesia (7.5 mg) with and without epinephrine (0.2 mg) in a randomized, double-blind, cross-over fashion. Sensory block was assessed with pinprick, transcutaneous electrical stimulation (TES) equivalent to surgical stimulation (at umbilicus, pubis, knee, and ankle), and tolerance of a pneumatic thigh tourniquet. Motor block was assessed with isometric force dynamometry. Discharge criteria were defined as return of pinprick sensation to dermatome S2, ability to ambulate, and ability to urinate. Extent of sensory block to pinprick over time was unaffected by the addition of epinephrine. However, epinephrine prolonged tolerance of TES at the pubis, knee, and ankle (33-48 min, P < 0.05) and of thigh tourniquet (30 min, P < 0.01). Motor block was prolonged by epinephrine at the quadriceps and gastrocnemius muscles (by 23 and 51 min, respectively, P < 0.002). Achievement of discharge criteria was prolonged by 48 min by the addition of epinephrine (P < 0.01). Thus, epinephrine may prolong surgical anesthesia for lower abdominal and lower extremity surgery and delay time until patients achieve discharge criteria. Implications: Using a cross-over study design, 12 volunteers underwent bupivacaine spinal anesthesia with and without epinephrine. This study suggests that adding epinephrine to bupivacaine may prolong surgical anesthesia and also delay patients' discharge. (Anesth Analg 1998;86:973-7)

The role of air plethysmography in the diagnosis of chronic venous insufficiency

Purpose: The role of air plethysmography (APG) in the diagnosis of venous disease is not well defined. We conducted this study to investigate the value of APG in the diagnosis of chronic venous insufficiency and to determine its correlation with the clinical severity of disease and the anatomic distribution of reflux. Methods: We studied 186 lower extremities with duplex scanning and venography and measured the venous volume, venous filling index (VFI), ejection fraction, and residual volume fraction with APG. Limbs were categorized according to the Society for Vascular Surgery and International Society for Cardiovascular Surgery classification of clinical severity of disease and according to the anatomic distribution of valvular incompetence. Results: Sixty-one limbs had no evidence of disease (class 0), 60 limbs had mild disease (classes 1, 2, and 3), and 65 limbs had severe disease (classes 4, 5, and 6). According to the results of duplex scanning and venography, there was no evidence of reflux in 56 limbs. Isolated superficial venous reflux occurred in 52 limbs, and perforator reflux, alone or in conjunction with superficial reflux, occurred in 30. Deep reflux, with or without superficial reflux, was found in 25 limbs. Deep and perforator reflux, with or without superficial reflux, was found in 19 limbs. The VFI had a sensitivity of 80% and 99% positive predictive value for any type of reflux. The VFI was significantly different between groups of limbs with different clinical severities of disease or different types of reflux. The incidence of deep or perforator reflux in limbs with a normal VFI value was 7%, and it was 82% in limbs with a VFI of more than 5. Among 86 limbs with VFI values not corrected with use of a thigh tourniquet, 28% did not have evidence of deep or perforator reflux, and among 15 limbs with VFI values corrected with the use of a tourniquet, 33% had perforator reflux, deep reflux, or both. All APG parameters had low positive predictive values for severe disease or ulceration. The ejection fraction and residual volume fraction did not influence the clinical severity of disease, did not discriminate between types of reflux, and in combination with the VFI did not improve the predictive value of APG. Conclusions: The VFI measured by APG is an excellent predictor of venous reflux, provides an estimate of the clinical severity of disease, and at high levels predicts deep reflux, perforator reflux, or both. Correction of an abnormal VFI with a thigh tourniquet is an unreliable predictor of the absence of deep or perforator incompetence. The predictive value of APG for severe disease or ulceration is poor. The ejection fraction and residual volume fraction, individually or in combination with the VFI, add little to the diagnostic value of APG, and their routine performance may not be clinically justified. (J Vasc Surg 1998;27:660-70.)

The effects of simulated Bier block IVRA on intracompartmental tissue pressure.

Intravenous regional anesthesia (IVRA) is a useful anesthetic method for closed reduction of fractures. However, IVRA has been associated with an increased incidence of compartment syndrome when treating tibial shaft fractures. The purpose of this study was to measure changes in anterior leg compartment pressures during simulated IVRA. A volunteer study was performed. An indwelling catheter placed in a consistent location between subjects was used to measure tissue pressure. A vinyl leg splint was used for exsanguination followed by thigh tourniquet inflation (300 mmHg). Normal saline (1.5 mL/kg) was injected through the greater saphenous vein (1.0 mL/s). Pressure measurements were obtained before and after tourniquet inflation, at 10 mL increments during saline injection, and intermittently after volume injection with the tourniquet inflated, then deflated. There was no significant difference in tissue pressure before (2.4 +/- 2.2 mmHg) and after (4.3 +/- 3.7 mmHg) tourniquet inflation (P = 0.11). No significant difference in tissue pressure were found as a function of injected volume (P = 0.62), as a function of time following saline injection during tourniquet inflation (P = 0.08), and after tourniquet deflation (P = 0.16). We conclude that in the normal atraumatic limb, simulated IVRA using normal saline does not increase tissue pressure within the anterior leg compartment.

Relationship of peak exercise capacity with indexes of peripheral muscle vasodilation.

Since leg muscles receive the majority of cardiac output and consume a large proportion of total oxygen consumption (VO2) during cycle exercise, maximum leg blood flow may be an important determinant of peak VO2 (VO2peak). We investigated the relationships between parameters of active hyperemia after thigh tourniquet occlusion (alone or with calf exercise) with whole body peak exercise capacity during maximum cycle exercise. Twenty-one healthy male subjects, aged 19-39 yr. performed maximum incremental cycle exercise. Calf blood flow, conductance (blood flow/mean blood pressure), vasodilatory capacity (peak/baseline conductance), and duration of vasodilation were then determined with venous occlusive plethysmography under two conditions: 1) after thigh tourniquet occlusion for 10 min; 2) after ischemic calf exercise (thigh tourniquet occlusion with calf exercise to exhaustion). Group mean VO2peak was 120 +/- 35% (standard deviation) predicted. There was a significant relationship between VO2peak/ lean body mass and peak calf conductance after maximum ischemic calf exercise (r = 0.556; P < 0.01). However, VO2peak/lean body mass was more closely correlated with the duration of vasodilation after thigh tourniquet occlusion with ischemic calf exercise (r = 0.861; P < 0.001). These results suggest that the duration of calf vasodilation after maximal ischemic calf exercise appears to be a better index of cycle exercise capacity in healthy subjects.

Fatal Paradoxical Cerebral Embolization during Bilateral Knee Arthroplasty

NEUROLOGIC complications of knee and hip arthroplasty range from mild delirium to coma and death. 1 The pathogenesis and operative events that lead to acute neurologic injury during joint arthroplasty are not completely understood but are thought to be a consequence of the fat embolism syndrome. 1-3 The syndrome often is accompanied by pulmonary, circulatory, hematologic, and neurologic derangement. According to one hypothesis, procedures that increase intramedullary pressure promote the entry of marrow fat or other debris into the central venous circulation through the medullary veins. 3,4 These emboli accumulate within the lung, causing increases in the pulmonary vascular resistance and pulmonary artery pressure. The consequent increase in right atrial and pulmonary artery pressures favor right-to-left shunt flow via a patent foramen ovale (atrial septal defect) or intrapulmonary shunt increasing the risk of paradoxical cerebral embolization. In the following report, intraoperative hemodynamic monitoring, carotid artery ultrasonography, and electroencephalography (EEG) were used to detect the sequence of operative events that led to paradoxical cerebral embolization causing fatal neurologic injury during bilateral knee arthroplasty.