Systemic responses to tourniquet release in children

The hemodynamic and metabolic effects of deflation of pneumatic tourniquets were assessed in 15 children, seven of whom had bilateral tourniquets applied. Systemic acidosis from release of lactate and PaCO2 after tourniquet deflation did not cause adverse effects in these healthy children. Larger increases in lactate were seen with longer tourniquet inflation times (greater than 75 min) or with bilateral tourniquets. The greatest decrease in pH was seen with simultaneous deflation of bilateral tourniquets. Heart rate did not change with tourniquet deflation, whereas systolic blood pressure decreased 8-10 mm Hg with deflation. Blood pressure returned to control values within 5-10 min; no arrhythmias were seen. Recommendations to minimize the systemic metabolic effects after release of tourniquets in children under general anesthesia include the following: 1) attempt to limit tourniquet inflation times to less than 75 min; 2) use controlled ventilation prior to and after tourniquet deflation to remove the respiratory component of acidosis; 3) check blood gas tensions within 5 min of tourniquet deflation in children with long tourniquet inflation times (greater than 75 min), and where bilateral tourniquets are deflated simultaneously or within 30 min of each other.     

Preoperative stellate ganglion blockade prevents tourniquet-induced hypertension during general anesthesia

BACKGROUND: Prolonged and excessive inflation of pneumatic tourniquets leads to a hyperdynamic circulatory response. Sympathomimetic activity is an important factor in tourniquet-induced hypertension. Stellate ganglion block specifically blunts sympathetic efferent nerves and prevents hypertension induced by sympathomimetic stimulation. The present study was performed to investigate the effects of stellate ganglion block (SGB) on arterial pressure and heart rate during prolonged tourniquet use under general anesthesia. METHODS: Twenty patients scheduled for knee arthroscopy were either treated with 10 ml of 1% lidocaine for SGB (SGB group; n = 10), or intramuscular injection (IM group; n = 10) before tourniquet inflation. Comparisons of systolic and diastolic arterial pressure and heart rate were made before and after the induction of anesthesia, 10 min after the lidocaine treatment, every 5 min during the first 60 min after tourniquet inflation, and immediately before and 5 min following deflation. The maximum values of the circulatory variables were compared. RESULTS: Tourniquet inflation caused increases in the circulatory variables in both groups. Systolic arterial pressure in the SGB group was significantly lower than that in the IM group after 55 min of tourniquet inflation. Diastolic arterial pressure also was significantly lower in the SGB group immediately before the deflation. The maximum values of the three hemodynamic variables were significantly lower in the SGB group. Arterial pressure significantly decreased after tourniquet deflation in the IM group. CONCLUSION: Ipsilateral SGB attenuated the hyperdynamic response mediated by prolonged tourniquet inflation during knee arthroscopy.     

Oxygen consumption and carbon dioxide elimination after release of unilateral lower limb pneumatic tourniquets.

Oxygen consumption (VO2), carbon dioxide elimination (VCO2), and respiratory exchange ratio (RQ) were continuously measured in 15 male and 15 female adults during knee surgery, with the leg exsanguinated by an inflatable tourniquet around the thigh. Arterial blood was also intermittently sampled for blood gas analysis, electrolytes, and lactate content before and after tourniquet deflation. There was a significant increase in VO2 and VCO2 after tourniquet deflation, which was more pronounced in the male (aged 29.5 +/- 14.8 yr, mean +/- SD) than the female (aged 56.9 +/- 15.6 yr) patients, both in terms of maximal increase (P less than 0.001) and percent of increase from values before deflation (P less than 0.001 and P = 0.01). The body weights and tourniquet inflation times were not significantly different between the male and female patients. Excess VO2 (O2 debt) and excess VCO2 over 12 min after deflation of the tourniquet were also significantly higher for male (593.5 +/- 222.9 mL and 714.9 +/- 463.8 mL, respectively) than for female patients (302 +/- 73.3 mL and 196 +/- 162.22 mL, respectively; P less than 0.01). There was no correlation between the duration of tourniquet inflation time and peak increase in VO2, peak increase in VCO2, and O2 debt over 12 min after deflation of the tourniquet; however, tourniquet time was weakly correlated with excess VCO2 over 12 min after tourniquet deflation (r = 0.55, P = 0.002). There was a significant decrease in pHa (P less than 0.001) from release of PaCO2 and lactate after tourniquet deflation. Plasma potassium levels also increased significantly after tourniquet release (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Failure to influence hypotension during spinal anaesthesia with a limb tourniquet

Fourty patients undergoing total hip replacement under spinal anaesthesia were allocated randomly to have a thigh tourniquet inflated after exanguination of the leg not being operated on or to act as controls. Significant hypotension (systolic arterial pressure < 70 mm Hg) was treated with i.v. ephedrine in 6 mg boluses. There was no significant difference between the two groups with respect to systolic blood pressure or requirement of ephedrine, during the hour that the tourniquet was applied or the period immediately after the removal of the tourniquet.     

Preoperative clonidine blunts hyperadrenergic and hyperdynamic responses to prolonged tourniquet pressure during general anesthesia

Although the mechanism of tourniquet-induced hypertension is still unclear, plasma norepinephrine concentrations continuously increase in parallel to arterial blood pressure during tourniquet inflation. Clonidine attenuates hyperadrenergic and hyperdynamic responses. We investigated the effects of clonidine on prolonged tourniquet inflation. Twenty-nine patients scheduled for elective orthopedic surgery were randomly assigned to receive IV clonidine (3 microg/kg; n = 14) or placebo (n = 15) before tourniquet inflation of the lower limbs under general anesthesia in a double-blinded manner. Arterial blood pressure, heart rate, epinephrine, and norepinephrine plasma concentrations were measured before tourniquet inflation, 60 min after tourniquet inflation, just before tourniquet deflation, and 20 min after tourniquet deflation. Mean arterial blood pressure and norepinephrine plasma-concentrations were significantly lower in the Clonidine group compared with Control after 60 min tourniquet inflation (P = 0.016; P = 0.006). Immediately before deflation of the tourniquet, the difference for mean arterial pressure between groups was even more pronounced (P = 0.005). Twenty minutes after deflation mean arterial blood pressure in the Control group was still increased and significantly higher compared with the Clonidine group (P = 0.002). In conclusion, preoperative IV clonidine blunts hyperadrenergic and hyperdynamic responses resulting from prolonged tourniquet inflation under general anesthesia in ASA class I--II patients. IMPLICATIONS: Tourniquet inflation is associated with a continuous increase in arterial blood pressure and sympathetic outflow. This study shows that IV clonidine effectively blunts increases of both arterial blood pressure and plasma norepinephrine concentrations.     

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

The effects of inflation of a 7-cm tourniquet applied to the upper arm of eight volunteers on venous lactate, venous blood gases, and ulnar nerve somatosensory evoked potentials (SSEPs) were investigated. The inflation pressure was 100 mmHg over the systolic pressure. Venous blood samples for lactate and blood gas determinations were withdrawn before tourniquet inflation; immediately and at 2, 5, 10, 15 min after tourniquet deflation; and additionally at 30, 45, and 60 min after deflation in the last four volunteers. SSEP stimulating surface electrodes were placed over the ulnar nerve at the wrist. Recording electrodes were placed over the ipsilateral ulnar groove of the elbow, Erb's point, and on the contralateral cortex. Averaged responses were acquired before inflation of the tourniquet, every 5-10 min during tourniquet inflation, and every 5-10 min for 45-60 min after tourniquet deflation. The tourniquet was inflated for 36 +/- 11 min. After deflation of the tourniquet, postdeflation pain and paresthesias were felt by five volunteers; these occurred at 30-120 s after deflation and lasted for 75-120 s. The postdeflation pains were characterized as burning, cramping, paresthesias, buzzing, or severe expansion of the hand. The venous blood lactate levels were significantly elevated for 10 min, and the time course of its change did not correlate with reperfusion pain. The PO2 and O2Hb saturation in venous blood were significantly elevated for 10-15 min after deflation. The elevated lactate and PO2 levels in the presence of a restored blood flow probably result from continued anaerobic muscle metabolism secondary to capillary closure from the tourniquet-induced ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

右美托咪啶抑制术中止血带所致心血管反应的临床研究

目的：探讨右美托咪啶对全麻下外科手术中肢体应用止血带辅助止血所致心血管反应的抑制作用.方法：38例患者全麻下行下肢骨科手术,随机分为右美托咪定组（DEX组,n=19）和对照组（n=19）.DEX组麻醉开始前静脉输注负荷剂量右美托咪啶1 μg/kg,10 min输注完毕后以0.5 μg·kg-1·h-1持续输至术毕;对照组以相同方法输注等量生理盐水.负荷剂量输完后两组采用相同的麻醉诱导和维持方法.于患者入手术室后（T0）,止血带充气前（T1）,充气后10 min（T2）、20 min（T3）、30 min（T4）、40 min（T5）、50 min（T6）、60 min（T7）,松开止血带后5min（T8）、10 min（T9）,记录有创收缩压（ISBP）、有创舒张压（IDBP）、心率、脑电双频谱指数（BIS）值,并记录停药至自主呼吸恢复及拔管所用时间.结果：与T0比较,T1时两组血压、心率、BIS值都明显降低（P〈0.05）,但两组间比较差异无显著性（P〉0.05）;与T1比较,对照组T3～T8时ISBP、IDBP、心率增高,T7达到峰值（P〈0.05或〈0.01）,DEX 组T1～T9时无显著变化（P〉0.05）.与DEX组比较,对照组T3～T8时ISBP、IDBP升高,T4～T9时心率增快（P〈0.05或〈0.01）.两组自主呼吸恢复时间、拔管时间差异均无显著性（P〉0.05）.结论：右美托咪啶可有效抑制全麻下应用肢体止血带所致的心血管反应,对患者苏醒时间无影响.     

Wrist tourniquet: the most patient-friendly way of bloodless hand surgery

BACKGROUND: The literature is scarce on wrist tourniquets. In this study, three well-established locations of tourniquet setting including upper arm, proximal forearm, and wrist were compared on the same limb using both clinical as well as biochemical variables in paramedical volunteers. METHODS: Twenty unmedicated, healthy, paramedical, right-hand dominant volunteers participated in the study. The left upper arms were used for monitoring. Blood pressures and heart rates were monitored and recorded before (baseline) and immediately after the application of the tourniquet, every 5 minutes, and at the time the patient requested deflation. An intravenous cannula (22 G) was placed on the right hand to obtain samples, which were taken at baseline and immediately after deflation of the tourniquet to evaluate the levels of pO2, pCO2, O2 saturation, pH, bicarbonate, blood sugar, lactate, hematocrit, and electrolytes. The tourniquets were applied to the right upper arm, forearm, and wrist of each subject with 5-day intervals between each trial. Subjective discomfort and tourniquet pain levels were recorded. For each trial, tourniquet tolerance and details of discomfort were recorded. Statistical analysis was performed as appropriate. RESULTS: Twenty volunteers aged 20 to 44 years were included. For each trial, in the first 10 minutes after inflation of the tourniquet, the heart rate and systolic blood pressure were increased compared with baseline values. Diastolic blood pressure was elevated immediately after inflation and remained so until deflation in each trial. Diastolic blood pressure values were higher in the upper-arm tourniquet group compared with wrist. Then pH, pO2, and O2 saturation values were decreased and pCO2 and lactate levels were increased compared with baseline values in each trial. Blood sugar was decreased significantly in the arm group. The decrease in pH, pO2, O2 saturation, and blood sugar in the upper arm group was significantly higher compared with wrist and forearm groups. The lactate value was higher in the upper arm group compared with wrist. Visual analog scale and numerical rating scores were lower in the wrist group compared with others at all times. The longest tourniquet tolerance was in the wrist group. In the wrist group, curling was observed in all subjects but the fingers could easily be extended. CONCLUSION: The wrist tourniquet is the most comfortable technique of bloodless surgery for procedures limited to the hand region.     

Tolerance of upper extremity pneumatic tourniquets and their effect on grip strength

This study was undertaken to evaluate tourniquet tolerance in healthy people. An arm tourniquet was inflated to 100 mmHg above systolic blood pressure for 21 minutes. We measured pain and grip strength before, during and at various times after deflation. We tested 40 subjects (20 women and 20 men) with an average age of 38 (range 22-58) years. Eight individuals did not tolerate the tourniquet for this length of time and the test was stopped. Visual analogical scale had a globally linear increase during tourniquet application. We noted a sensation of well-being just after deflation, quickly replaced by pain in the tested limb due to limb reperfusion. We also noted a significant loss of strength in the tested limb, which completely recovered by 48 hours. We also observed a significant loss of strength in the contralateral hand, which also recovered by 48 hours. The possible reasons for these temporary losses of strength in both the ipsilateral and contralateral limbs are discussed.     

The hemodynamic and metabolic effects of tourniquet application during knee surgery

We evaluated the effects of tourniquet application on the cardiovascular system and metabolism in 10 young men undergoing knee surgery with general anesthesia. The duration of inflation was from 75 to 108 min. Heart rate, mean arterial pressure, cardiac index (CI) by pulse contour method, and systemic vascular resistance were measured before, during, and after tourniquet inflation. pH, PaO(2), PaCO(2), and lactate blood concentrations were also measured. VO(2) and VCO(2) were assessed every minute from tracheal intubation up to 15 min after tourniquet deflation and VO(2) in excess of the basal value over the 15 min after deflation (VO(2)exc) was calculated. Mean arterial pressure increased 26% (P: < 0.05) during inflation and returned to basal values after deflation. CI did not change immediately after inflation; although, thereafter, it increased 18% (P: < 0.05). Five minutes after deflation, CI further increased to a value 40% higher than the basal value. Therefore, systemic vascular resistance increased 20% suddenly after inflation (P: < 0.05) and decreased 18% after deflation (P: < 0.05). VO(2) and VCO(2) remained stable during inflation and increased (P: < 0.05) after deflation. VO(2)exc depended on duration of tourniquet inflation time (Tisch) (P: < 0.05). After deflation, PaCO(2) and lactate increased (P: < 0.05) while Tisch increased. We conclude that tourniquet application induces modifications of the cardiovascular system and metabolism, which depend on tourniquet phase and on Tisch. Whether these modifications could be relevant in patients with poor physical conditions is not known. Implications: The clinical effects of tourniquet application were evaluated in 10 young men undergoing knee surgery. Our data indicate that tourniquet application causes hemodynamic and metabolic changes which may become clinically relevant after a long period of tourniquet inflation, particularly in patients with concomitant cardiovascular diseases.     

Preoperative oral dextromethorphan vs. clonidine to prevent tourniquet-induced cardiovascular responses in orthopaedic patients under general anaesthesia

BACKGROUND AND OBJECTIVE: Preoperative oral dextromethorphan and intravenous clonidine attenuate arterial pressure and heart rate increases during tourniquet inflation under general anaesthesia. The effect of preoperative oral clonidine on these variables has not been investigated. METHODS: We designed this study to compare the effect of preoperative oral dextromethorphan or clonidine on haemodynamic changes during tourniquet inflation in 75 patients undergoing lower limb surgery under general anaesthesia. Patients were randomly assigned into three groups: dextromethorphan 30 mg (n = 25), clonidine 3 microg kg(-1) (n = 25) and placebo (n = 25). Anaesthesia was maintained with isoflurane 1.2% and N2O 50% in oxygen with endotracheal intubation. Dextromethorphan, clonidine or placebo was given orally in a double-blinded fashion 90 min before induction of anaesthesia. Systolic, diastolic and mean arterial pressure and heart rate were measured at 0, 30, 45, 60 min after the start of tourniquet inflation, before tourniquet release and 20 min after tourniquet deflation. RESULTS: Systolic, diastolic and mean arterial pressure were significantly lower in the clonidine group compared with control after 45, 60 min tourniquet inflation and before tourniquet release (P < 0.05). Twenty minutes after deflation, diastolic and mean arterial pressure in the control group were still increased and significantly higher compared with the clonidine group (P < 0.05). Development of more than a 30% increase in systolic arterial pressure during tourniquet inflation was more frequent in the control group than in the other groups. CONCLUSIONS: Preoperative oral clonidine 3 microg kg(-1) significantly prevented tourniquet-induced systemic arterial pressure increase in patients under general anaesthesia better than oral dextromethorphan.     

The effects of simulated Bier block IVRA on intracompartmental tissue pressure

Background: 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.
Methods: 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.
Results: 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 differences 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).
Conclusions: We conclude that in the normal atraumatic limb, simulated IVRA using normal saline does not increase tissue pressure within the anterior leg compartment.     

Differential effects of hyperventilation on cerebral blood flow velocity after tourniquet deflation during sevoflurane, isoflurane, or propofol anesthesia

The purpose of this study was to compare the degree of increase in middle cerebral artery (MCA) blood flow velocity after tourniquet deflation when modulating hyperventilation during orthopedic surgery under sevoflurane, isoflurane, or propofol anesthesia. Twenty-four patients undergoing elective orthopedic surgery were randomly divided into sevoflurane, isoflurane, and propofol groups. Anesthesia was maintained with sevoflurane, isoflurane, or propofol administration with 33% oxygen and 67% nitrous oxide at anesthetic drug concentrations adequate to maintain bispectral values between 45 and 50. A 2.0-MHz transcranial Doppler probe was attached to the patient’s head at the temporal window, and mean blood flow velocity in the MCA (V _mca) was continuously measured. The extremity was exsanguinated with an Esmarch bandage, and the pneumatic tourniquet was inflated to a pressure of 450 mmHg. Arterial blood pressure, heart rate, V _mca and arterial blood gases were measured every minute for 10 min after release of the tourniquet in all three groups. Immediately after tourniquet release, the patients’ respiratory rates were increased to tightly maintain end-tidal carbon dioxide (PetCO₂) at 35 mmHg. No change in partial pressure of carbon dioxide in arterial blood (PaCO₂) was observed pre- and posttourniquet deflation in any of the three groups. Increase in V _mca in the isoflurane group was greater than that in the other two groups after tourniquet deflation. In addition, during the study period, no difference in V _mca after tourniquet deflation was observed between the propofol and sevoflurane groups. Hyperventilation could prevent an increase in V _mca in the propofol and sevoflurane groups after tourniquet deflation. However, hyperventilation could not prevent an increase in V _mca in the isoflurane group.     

Arterial hypertension associated with the use of a tourniquet with either general or regional anaesthesia

A hypertensive patient with left cardiac enlargement developed marked hypertension under general anaesthesia, during which time a tourniquet was applied around his thigh. When the tourniquet was released, severe hypotension ensued which responded to therapy. The patient, however, died 16 h later of a myocardial infarction. Because of this incident, the anaesthetic and haemodynamic data of 699 patients who underwent limb surgery with a pneumatic tourniquet inflated for at least an hour were retrospectively examined using multivariate analysis. A 30% increase in systolic and/or diastolic arterial blood pressure occurred in 27% of the total patient material and in 67% of those who had had a general anaesthetic. There was a higher frequency of the occurrence of "tourniquet hypertension" with older age, longer operations and the operation site being the lower rather than the upper limb. Tourniquet hypertension rarely occurred in patients with spinal anaesthesia (2.7%) and brachial plexus blockade (2.5%), while those with intravenous regional anesthesia had a higher incidence (19%) of hypertension.     

A new tourniquet system that determines pressures in synchrony with systolic blood pressure

Introduction This study reports the results of the clinical use of a new tourniquet system for surgery of the lower extremity that can determine tourniquet pressure in synchrony with systolic blood pressure. Materials and methods We prospectively applied additional pressure of 100 mmHg during 100 surgical procedures (54 knees, 2 legs, 44 feet and ankles). Results A bloodless surgical field was obtained in almost all patients. The average durations of surgery and tourniquet time were 50 and 51 min, respectively. The average initial blood pressures were 112 mmHg systolic and 60 mmHg diastolic. The average maximum pressure changes during surgery were 33 mmHg systolic and 21 mmHg diastolic. No complications associated with this system arose either during or after surgery. Conclusion The conventional tourniquet pressure in the lower extremity is 300 or 350 mmHg, whereas this synchronized system required less pressure, making it a safe, useful device for controlling a bloodless surgical field in lower extremity surgery.     

Hemodynamic changes with sufentanil-oxygen anesthesia for open heart surgery--a comparison of patients with beta-blocking medication or without it

We investigated hemodynamic changes in patients undergoing coronary artery bypass grafting (CABG) and valve replacement. The former had been medicated with beta-blocking agent until the morning of operative day. On the other hand, the latter received no medication. We measured systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP), heart rate, and rate pressure product (RPP) at the following five points; before induction of anesthesia, immediately before intubation, immediately after intubation, one minute after skin incision and one minute after sternotomy. In both groups, SAP and DAP decreased significantly after induction; heart rate did not change during our study; and RPP decreased significantly after skin incision. There were no significant differences between the group with beta-blocking agent and the group without it. These results suggest that beta-blocking agents exert no influence in our study, and sufentanil-oxygen anesthesia produce hemodynamic stability for open heart surgery.     

The anesthetic management of triplet cesarean delivery: a retrospective case series of maternal outcomes

Spinal anesthesia for the cesarean delivery of triplets is associated with an increased incidence of maternal hypotension and placental hypoperfusion. We performed a retrospective case series analysis between January 1992 and June 2000 to evaluate the effects of regional anesthetic techniques for cesarean delivery in triplet pregnancies on maternal and neonatal outcome. Spinal and epidural anesthesia were compared with respect to intraoperative hemodynamics and neonatal outcomes. Ninety-six triplet pregnancies were delivered by cesarean section, of which 91 received regional anesthesia. A statistically significant decrease in systolic blood pressure was demonstrated immediately after the induction of spinal as compared with epidural anesthesia. The total volume of IV crystalloid used was significantly larger in the Spinal Anesthesia group. The number of patients receiving more than 15 mg of ephedrine and the cumulative dose of ephedrine was significantly larger in the Spinal group compared with the Epidural group. There were no differences in the rate of perioperative complications between the Spinal and Epidural Anesthesia groups. Neonatal Apgar scores were similar in both groups. The data suggest that both epidural and spinal anesthesia for triplet cesarean delivery are safe techniques, but the latter is associated with a larger initial decrease in systolic blood pressure. This decreasing of systolic blood pressure, however, remained within the physiological range and did not seem to be clinically significant. The need for more crystalloid fluids and ephedrine should be anticipated when spinal anesthesia is used for these cases. IMPLICATIONS: A large retrospective case series of the effects of spinal and epidural anesthesia on maternal hemodynamic profile during cesarean delivery for triplet gestation was performed. Our findings suggest that spinal anesthesia results in outcomes comparable to epidural anesthesia for both mother and newborns.     

Effect of tourniquet use on activation of coagulation in total knee replacement

Total knee replacement often is performed with tourniquet application. The advantages of a dry field, including fixation, are well known, but it still is debatable if tourniquet application increases deep vein thrombosis. Measurement of coagulation markers is a well accepted method of studying thrombogenesis activation intraoperatively and postoperatively. Twenty patients undergoing total knee replacement with subarachnoid anesthesia were assigned randomly to two groups: either with tourniquet application (Group I) or without tourniquet application (Group II). There were no differences between patients in the two groups in terms of age, gender, diagnosis (all had osteoarthritis), operative time, and total (intraoperative and postoperative) blood loss. Markers for thrombin generation and fibrinolysis were measured. Blood samples were drawn at four times: baseline before the operation; after bone cuts; after cement fixation (Group II) or 2 minutes after tourniquet deflation (Group I); and 1 hour after surgery. Markers of thrombin generation and fibrinolysis showed a significant increase from baseline in all the patients. In Group II these markers started to increase during surgery, whereas in Group I the increase occurred at the end of the procedure when the tourniquet was deflated. The total amount of thrombin generation was significantly higher in Group II (without tourniquet), whereas fibrinolysis was significantly greater in Group I. Total knee replacement is accompanied by a hypercoagulative state with or without the use of a tourniquet, but it seems to be higher when the tourniquet is not used. In addition, tourniquet application may increase fibrinolysis.     

A randomized comparison between midazolam and thiopental for elective cesarean section anesthesia. I. Mothers

In a randomized blind trial midazolam (0.3 mg kg-1) was compared with thiopental (4 mg kg-1), both combined with meperidine-nitrous oxide, for elective cesarean section anesthesia in 40 women. We found no statistically significant differences between thiopental and midazolam at induction, during operation or recovery with regard to maintenance doses, change in maternal neurologic status based on a modified Glasgow Coma Scale, systolic blood pressure, and heart rate. Induction time was 120 seconds with midazolam and 111 seconds with thiopental. There were significant differences with regard to diastolic blood pressure. Side effects occurred with approximately equal frequencies, but vomiting was significantly more frequent after thiopental. Perivenous tenderness and erythema occurred in four patients, all after thiopental. Midazolam appears to be a suitable alternative to thiopental for the induction and maintenance of anesthesia for elective cesarean section.     

Effects of transient ischemia on nutrient flow and arteriovenous shunting in canine hindlimb.

A canine model was developed to simulate use of a pneumatic tourniquet in the clinical setting in order to study the acute and delayed effects of transient ischemia on limb and tissue blood flow, using radioactive microspheres and electromagnetic flow probes. Experimental femoral artery flow rose markedly after tourniquet ischemia, and remained significantly elevated for 24 hours (p less than 0.01). Blood flow to the rectus femoris and anterior tibial muscles rose significantly (p less than 0.05) immediately after tourniquet ischemia, and the latter remained significantly elevated at 24 hours (p less than 0.05). Blood flow to the skin of the experimental limbs was elevated significantly (p less than 0.05), immediately ater tourniquet ischemia, and at no other time. Blood flow to the nerves did not increase to its maximum until 15 minutes after tourniquet deflation, and by 24 hours was normal. Tibial and femoral marrow blood flow remained significantly lower in the experimental limb throughout the 24-hour period. Ater tourniquet ischemia (300 mmhg; 2 hours), greatly increased femoral artery flow was related to reactive hyperemia in skin, muscle, and nerve. Twenty-four hours after tourniquet deflation, there was a significant increase in femoral artery and anterior tibial muscle blood flow, and significant arteriovenous shunting from the experimental limb. These data suggest that the hemodynamic response to a transient ischemic injury is more prolonged and of greater magnitude than previously believed.