Tourniquet pain in a volunteer study: effect of changes in cuff width and pressure

This study examines the relationship between pneumatic tourniquet cuff size, occlusion pressure and the resulting pain. Two tourniquet cuff widths were used, a wide (14 cm) and a narrow cuff (7 cm). Twenty volunteers were divided into two groups for tourniquet application: a pressure group in which the tourniquet was inflated to a pressure equal to the systolic pressure + 100 mmHg, and a saturation group in which the tourniquet was inflated to 10 mmHg above the loss of arterial pulse, as indicated by cessation of pulse waveform on an oximeter. According to a randomised cross-over protocol, subjects were studied using wide and narrow cuffs simultaneously and/or successively on both arms. Pain was assessed by subjects by means of a visual analogue score (0-10 cm). Occlusion pressures were similar for all volunteers in the pressure group and significantly higher than those in the saturation group with both the wide and narrow tourniquets. The wide cuff data turned out to be significantly lower than the narrow cuff results. Subjects in the pressure group could tolerate pain with the narrow cuff for significantly longer than with the wide cuff. However, in the saturation group, volunteers tolerated the wide cuff for longer. Pain intensity increased more rapidly in those in the pressure group with the wide cuff than with the narrow cuff. In contrast, volunteers in the saturation group found the narrow cuff to be more painful than the wide cuff. In conclusion, this study has shown that a wide tourniquet cuff is less painful than a narrow cuff if inflated at lower pressures and at these lower pressures it is still effective at occluding blood flow.     

A new method for estimating arterial occlusion pressure in optimizing pneumatic tourniquet inflation pressure

To reduce pressure-related injuries resulting from pneumatic tourniquet use, the lowest possible inflation pressure is recommended. Arterial occlusion pressure (AOP) is a measure of the cuff pressure required to maintain a bloodless surgical field. However, its determination method is time consuming, requires operator skill, and is therefore seldom used in current practice. An AOP estimation can be made by knowing the pressure transmitted to the underlying soft tissues. We measured upper and lower extremity tissue pressures under the tourniquet cuff at 100, 200, and 300 mm Hg of tourniquet inflation pressures in 30 anesthetized living adult patients. All patients received general anesthesia with neuromuscular relaxation. A Stryker intra-compartmental pressure monitor was used to measure tissue pressures under the tourniquet cuff. In all patients, the soft tissue pressures were consistently lower than the applied tourniquet inflation pressures. Our results revealed tissue padding coefficients for extremities 20 to 75 cm in circumferences. An estimation method of AOP was developed [AOP = (systolic blood pressure + 10)/Tissue padding coefficient]. The new AOP estimation method may be a simple, rapid, and clinically practical alternative to the AOP determination method.     

Effects of reperfusion intervals on skeletal muscle injury beneath and distal to a pneumatic tourniquet.

To date there have been no experimental studies specifically directed at effects of reperfusion intervals on skeletal muscle injury beneath the tourniquet. 99mTechnetium pyrophosphate (Tc 99) incorporation and correlative histology were used to assess injury 2 days after tourniquet application in muscles beneath (thigh) and distal (leg) to the cuff. Tourniquets were applied to rabbit hindlimbs for a total of either 2 or 4 hours. In the 4-hour series, tourniquet compression (either 125 mm Hg or 350 mm Hg cuff inflation pressure) was either continuous or interrupted by 10-minute reperfusion intervals after 2 hours or after every hour of cuff inflation. In the 2-hour series, tourniquet compression (350 mm Hg) was either continuous or interrupted by 10-minute reperfusion intervals after 2 hours or after every hour of cuff inflation. In the 2-hour series, tourniquet compression (350 mm Hg) was either continuous or interrupted by a 10-minute reperfusion interval after 1 hour. Pyrophosphate incorporation (Tc 99 uptake) was significantly greater in the thigh region than in the leg region in all of the 4-hour tourniquet groups. Tc 99 uptake was significantly reduced by reperfusion after each hour of cuff inflation. With 350 mm Hg tourniquet pressure, a reperfusion interval after 2 hours of cuff inflation tended to exacerbate tourniquet compression injury. Reperfusion intervals did not significantly affect Tc 99 uptake in the leg region of these groups. With a 2-hour tourniquet time, Tc 99 uptake in the thigh was significantly decreased by reperfusion after 1 hour of cuff inflation. Previous clinical recommendations, based on serum creatine phosphokinase abnormalities after experimental tourniquet ischemia, probably reflected tourniquet compression injury. Hourly reperfusion limits skeletal muscle injury during extended periods of tourniquet use.     

Tourniquet at 50 mm Hg followed by intravenous lidocaine diminishes hand pain associated with propofol injection.

We evaluated the efficacy of intravenous lidocaine, with and without a tourniquet, to decrease the intensity of pain during intravenous propofol injection in 82 patients undergoing general anesthesia. Patients in group A (n = 20) received propofol (2 mg/kg IV); patients in group B (n = 22) received 2% lidocaine (100 mg IV) followed 1 min later by propofol (2 mg/kg). Patients in group C (n = 21, saline placebo) and D (n = 19, 2% lidocaine) had an arm tourniquet inflated to 50 mm Hg applied for 1 min after gravity drainage of venous blood. The intensity of pain along the forearm was marked on a 0-100-mm visual analogue scale. Pain intensity was less in group B (21 +/- 19 mm) than in group A (75 +/- 28 mm; P less than 0.05). Pain intensity was significantly less in group D (1 +/- 2 mm) compared with group B (21 +/- 19 mm; P less than 0.001). We conclude that intravenous lidocaine before propofol injection attenuates the painful response; whereas, lidocaine administered after a tourniquet inflated to 50 mm Hg for 1 min virtually abolishes the pain associated with intravenous propofol.     

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.     

Local compression patterns beneath pneumatic tourniquets applied to arms and thighs of human cadavera

Distributions of tissue fluid pressure were examined beneath a standard pneumatic tourniquet in six upper extremities and six lower extremities of fresh human cadavera, disarticulated at the shoulder and hip, respectively. A standard 8-cm-wide tourniquet cuff was applied at mid-humerus or mid-femur position. Tissue fluid pressures were measured by 100-cm-long slit catheters inserted parallel to the bone at four tissue depths: subcutaneous, subfascial, mid-muscle, and adjacent to bone. All arms and thighs were studied at the following cuff pressures: 100, 150, 200, 250, 300, 400, and 500 mm Hg. Tissue fluid pressure was always maximal in subcutaneous tissue at mid-cuff. Transmission of cuff pressures to deeper tissues was significantly less (p less than 0.01) in the thighs with a girth of 40-52 cm than in the arms with a girth of 22-33 cm. At the four tissue depths studied, tissue fluid pressures fell steeply in a longitudinal direction near the cuff edge to levels near zero at points 1-2 cm outside each cuff edge. Our results suggest that wider cuffs are required on thighs than on arms to provide a bloodless field during limb surgery and to minimize underlying tissue injury associated with high cuff pressures. Our recommendation for wider tourniquet cuffs than those presently used during orthopaedic surgery is contrary to recent prevailing knowledge.     

Muscle injury induced beneath and distal to a pneumatic tourniquet: a quantitative animal study of effects of tourniquet pressure and duration.

Previous recommendations regarding the "safe" period of tourniquet hemostasis were based largely on studies of ischemia distal to the tourniquet. This study quantitatively analyzed skeletal muscle injury induced beneath and distal to a pneumatic tourniquet applied to the hindlimbs of rabbits for 1, 2, or 4 hours with a cuff inflation pressure of 125, 200, or 350 mm Hg. Technetium Tc 99m pyrophosphate incorporation after systemic injection (Tc 99 uptake) and correlative histology were used to evaluate tissue damage 2 days after tourniquet application. Compared with the contralateral control limbs, compression and ischemia induced statistically significant increases in Tc 99 uptake in the thigh and leg regions of all groups. Pyrophosphate incorporation was significantly greater in the thigh region than in the leg region after 2 hours of compression in the 200 and 350 mm Hg pressure groups and following 4 hours of compression in all pressure groups. Focal and regional fiber necrosis and degeneration were observed in thigh muscles after 2 hours of tourniquet compression. Two hours of continuous tourniquet application at clinically relevant cuff inflation pressures induced significant skeletal muscle necrosis beneath the tourniquet. Use of the lowest possible inflation pressure for a limited duration should minimize the degree of tissue injury caused by tourniquet application.     

Skeletal muscle injury induced by a pneumatic tourniquet: an enzyme- and immunohistochemical study in rabbits.

The pathophysiology of skeletal muscle injury induced by compression beneath pneumatic tourniquets is poorly understood. Tourniquet hemostasis was induced in rabbit hindlimbs for 2 hr with a cuff inflation pressure of either 125 mm Hg (n = 5) or 350 mm Hg (n = 5). Skeletal muscle biopsies, taken 2 days later from tissue beneath and distal to the tourniquet, were frozen and analyzed using enzyme- and immunohistochemical techniques. In the 350 mm Hg tourniquet group, four of 10 thigh muscle samples demonstrated significant regional necrosis (mean 37.3% of the total cross-sectional area). Regional necrosis was not observed in thigh muscles of the 125 mm Hg tourniquet group or in any of the ischemic leg muscles. A topographic pattern of necrosis consistent with the arterial distribution of skeletal muscle suggested pathogenic events during the reperfusion period, such as granulocyte-mediated superoxide radical formation. Extremely large and rounded fibers (histochemically identified as Type IIB fibers) were observed in compressed thigh muscles, indicating differential fiber sensitivity to tourniquet compression and ischemia. The present study demonstrated significant skeletal muscle necrosis after a 2 hr tourniquet applied at a clinically relevant cuff inflation pressure. Recent studies of systemic changes associated with limb "ischemia" should be reassessed in consideration of the confounding effects of tissue compression induced beneath pneumatic tourniquets.     

The significance of the pneumatic tourniquet technique for an innovative varicose vein surgery--methods,advantages, risks,danger

AIM: The systemic effects of the pneumatic tourniquet technique in varicose vein surgery were studied in order to evaluate possible risks and threats. METHODS: 155 patients were included to look at intraoperative changes of cardiovascular parameters and capillary blood and respiratory gases. RESULTS: Whereas the pulse rate showed only an insignificant rise of 3/min, the systolic and diastolic blood pressure increased significantly by 12 and 6 mm Hg resp., after inducing ischemia by roller cuff. After removal of the roller cuff blood pressure decreased by 14 and 9 mm Hg, resp., again. At releasing of the ischemia, pH values drop by 0.02, and the base excess by 0.3 mval/L with operation on one side and 0.5 mval/L in both sides operation. In comparison, the capillary pCO 2 rose by 3 mm Hg and the pCO 2 of the respiratory air by 1 mm Hg in one side operation and 3 mm Hg, resp. in operation of both sides. The pressure in the roller cuff was in the middle only 55 mm Hg above systemic pressure values. CONCLUSIONS: The systemic effects of the tourniquet technique have no clinical relevance. The use of the pneumatic tourniquet (Loefqvist method) is unrestrictedly recommended due to its advantages, such as no intraoperative blood loss, avoidance of post-op haematoma and pain and good immediate cosmetic results.     

Wide contoured thigh cuffs and automated limb occlusion measurement allow lower tourniquet pressures

We examined the amount of thigh tourniquet pressure that can be reduced from the typical 300 to 350 mm Hg by using a new automated plethysmographic limb occlusion pressure measurement technique. We also examined how much pressure could be reduced by using a wide contoured cuff compared with a standard cuff and if limb occlusion and systolic blood pressures were well correlated. Patients having surgery with a thigh tourniquet were randomized into two groups, one group having surgery with a standard cuff and the other with a wide cuff. Pressure was set at the automatically measured limb occlusion pressure plus a safety margin. Systolic blood pressure and quality of the bloodless field were recorded. The standard cuff maintained an acceptable bloodless field for 18 of 20 patients at an average pressure of 242 mm Hg, and the wide cuff was acceptable for 19 of 20 patients at an average of 202 mm Hg. One patient in each group had a poor bloodless surgical field at the initial pressure, and one patient in each group had a poor bloodless surgical field after a sharp rise in blood pressure during surgery. Systolic blood pressure was not correlated well enough to limb occlusion pressure to be used alone to set the optimum cuff pressure. The automated limb occlusion pressure technique and the wide contoured cuff reduced average pressure by 33-42% from typical pressures.     

Tourniquet pressure settings based on limb occlusion pressure determination or arterial occlusion pressure estimation in total knee arthroplasty? A prospective,randomized, double blind trial

Objective

The aim of this study was to compare the limb occlusion pressure (LOP) determination and arterial occlusion pressure (AOP) estimation methods for tourniquet pressure setting in adult patients undergoing knee arthroplasty under combined spinal-epidural anesthesia.

Use of Tourniquet During Knee Arthroplasty in Patients With Radiographic Arterial Calcifications

BackgroundUse of tourniquet during total knee arthroplasty (TKA) in patients with radiographic arterial calcifications is controversial. Intimal arterial calcifications are feared to be associated with ischemic complications such as delayed wound healing and arterial thrombosis, whereas medial calcifications stiffen the arterial wall, possibly leading to tourniquet failure and increased blood loss.MethodsWe conducted a prospective cohort study to determine the incidence of tourniquet failure (inflated up to 300 mm Hg), blood transfusions, wound healing, and ischemic complications in thighs with and without arterial calcifications on preoperative radiographs, in 2548 consecutive primary TKAs conducted in our unit over a 5-year period. Eighty-six thighs showed vascular calcifications: 58 medial and 28 intimal.ResultsThighs with vascular calcifications had higher risk of tourniquet failure as compared to those without calcifications (P < .001), but with no significant increase in incidence of blood transfusions. All cases of tourniquet failure in the calcification group occurred in thighs with medial calcifications, whereas all cases of tourniquet failure in the control group occurred in obese patients. There was no difference in wound healing and ischemic complications in limbs with and without arterial calcifications.ConclusionThe presence of arterial calcifications on preoperative radiographs increases the risk of tourniquet failure at 300 mm Hg in patients undergoing TKA, with no significant increase in rate of blood transfusions, wound healing or ischemic complications.     

Effect of Different Tourniquet Pressure on Postoperative Pain and Complications After Total Knee Arthroplasty: A Prospective,Randomized Controlled Trial

BackgroundTourniquet pressure inflation is commonly selected between 100 and 150 mm Hg above the systolic blood pressure (SBP). Given the lack of evidence to support a given inflation pressure, our study aimed to ascertain the lowest tourniquet pressure that facilitated total knee arthroplasty (TKA) and resulted in the least postoperative pain and complications.MethodsIn a double-blind, randomized controlled trial of patients scheduled for unilateral primary TKA, 150 were assigned to use tourniquet pressures of SBP + 75 mm Hg (group I), SBP + 100 mm Hg (group II), and SBP + 150 mm Hg (group III). The quality of the bloodless field, total blood loss, and limb swelling were determined perioperatively. Clinical outcomes were evaluated by visual analog scale for pain at thigh and surgical site, serum creatinine phosphokinase levels, wound complications, range of motion, and Knee Society Score.ResultsVisual analog scale for pain at thigh and surgical site were lowest in group I (P < .01) and highest in group III (P < .01). However, the quality of bloodless field at the tibial cutting surface was significantly better in group III compared to group I/II but not at the femoral cutting surface. The total blood loss and limb swelling showed no difference among 3 groups. Postoperative serum creatinine phosphokinase levels at 24 and 48 hours and wound complications in group III were significantly higher than group I (P < .01) and group II (P < .01). Nevertheless, postoperative knee range of motion and Knee Society Score were not significantly different among 3 groups.ConclusionPost TKA, the lowest tourniquet pressure was associated with significantly less postoperative tourniquet and surgical site pain, muscle damage, and wound complications.     

Tourniquet pain: a volunteer study

The effect of inflation pressure (300 and 400 mm Hg) and method of exsanguination (gravity and Esmarch bandage) on the time of onset and the severity of tourniquet-induced pain in the lower extremity was investigated in 11 unmedicated adult volunteers. Each volunteer underwent eight experiments in a random order. A visual analog scale was used to assess pain and discomfort. Blood pressure and pulse rate were measured continuously. Experiments were concluded when the pain rose to a prefixed level. All experiments were performed using a standard orthopedic tourniquet (7 cm wide). Ten additional experiments were carried out using a Bier blockade tourniquet (5 cm wide). There were no differences in duration of tourniquet inflation between inflation pressures nor between methods of exsanguination. There was a small and transient but nevertheless statistically significant increase in blood pressure caused by inflation and a significantly larger increase just before deflation. The 5-cm tourniquet experiments, otherwise identical to the 7-cm tourniquet experiments, were tolerated significantly longer due to a longer time of onset and less severe pain. The 5-cm tourniquet also needed significantly higher inflation pressures to fully occlude the arterial supply (240-450 mm Hg). In all instances, 260 mm Hg was adequate to fully occlude the arterial supply when a 7-cm tourniquet was used. Only half of the experiments were concluded due to intolerable pain at the site of the tourniquet. Most of the others were concluded due to pain mainly in the calf or pain throughout the leg.(ABSTRACT TRUNCATED AT 250 WORDS)     

Survey of tourniquet use in podiatric surgery

Tourniquet use in foot and ankle surgery is common practice; however, the technique varies among foot and ankle surgeons and there are no standard guidelines. To analyze trends in foot and ankle tourniquet use, the authors conducted an e-mail survey. One thousand six hundred sixty-five foot and ankle surgeons were sent a tourniquet-use survey via e-mail, across Canada and the United States. Nineteen percent of the recipients completed and returned the surveys. Eleven (3.4%) rarely or never use a tourniquet and 8 (2.5%) use an Esmarch bandage tourniquet at the ankle. Most use pneumatic ankle cuffs (92% use, 27% use exclusively); many also use thigh cuffs (69%) and some also use calf cuffs (15%). Most thigh-cuff users (62%) experience problems with cuff fit sometimes or often. All but 3 respondents exsanguinate the limb before tourniquet inflation. Specific devices used for exsanguination varied among surgeons. Most commonly used tourniquet pressures range from /=351 mm Hg for the thigh (64% use pressures between 301 and 350 mm Hg). Only 7% of respondents consider limb occlusion pressure when selecting tourniquet cuff pressure. Based on published studies of limb occlusion pressures, these ranges suggest that some of the more common pressure settings may be higher than necessary for many patients. Vascular disease or previous bypass (91%) and deep vein thrombosis (83%) were the most commonly listed contraindications to tourniquet use. Approximately 10% of respondents have either experienced or learned of skin and nerve injuries secondary to lower extremity tourniquet use at any level. The varied responses show a lack of overall consensus on tourniquet pressure settings. Guidelines for optimizing cuff pressure and technique should be established to minimize the risk of complications.     

An investigation of the neurophysiologic mechanisms of tourniquet-related pain: changes in spontaneous activity and receptive field size in spinal dorsal horn neurons

BACKGROUND AND OBJECTIVES: Several theories have been proposed for the pain resulting from the nerve compression and ischemia associated with maintaining the inflation of a pneumatic tourniquet on an extremity. This investigation observes changes in the spontaneous activity and receptive field (RF) size of spinal dorsal horn neurons during tourniquet-related nerve compression and ischemia. METHODS: Forty-eight pentobarbital-anesthetized rats were prepared for single-unit spinal dorsal horn cell recording utilizing an in vivo extracellular technique. Cells were characterized as either low threshold mechanoreceptor (LTM) neurons, wide dynamic range (WDR) neurons, or high threshold nociresponsive (NR) neurons based on their response to light touch (brush), non-noxious pressure, or noxious pinch. Receptive fields were carefully mapped. A 1 x 9 cm pneumatic tourniquet (Hokanson, Inc., Seattle, WA) was then applied to the animals' hind limb thigh and inflated to 300 mm Hg for 60 minutes. Throughout the 60-minute tourniquet inflation period, spontaneous activity, cell firing rate response characteristics, and RF size were carefully monitored. RESULTS: Twenty-three cells in 20 animals were characterized and monitored: 8 LTM, 6 WDR, and 9 NR neurons. Receptive fields were distal to the tourniquet cuff for 16 cells and proximal for 7 cells. Low threshold mechanoreceptor neurons demonstrated little spontaneous activity prior to tourniquet inflation in the absence of RF stimulation. The RF size for all LTM neurons decreased or became silent during the tourniquet inflation period. The RF size increased in two of six WDR neurons with two cells demonstrating a progressive increase in intermittent spontaneous firing during the tourniquet inflation period. Receptive field size increased in five of five NR neurons with RF located proximal to the tourniquet cuff from 29 +/- 10 mm2 to 54 +/- 30 mm2 (RF area 1.9 +/- 0.7; t = 2.7, P = .03). All five of these NR neurons also demonstrated an increase in spontaneous activity at 37 +/- 14 minutes of tourniquet inflation which continued throughout the remainder of the tourniquet inflation period (P < .05). CONCLUSIONS: The results of this study indicate that nerve compression and ischemia results in block of input to LTM neurons having RFs distal to the tourniquet cuff and an increase in spontaneous activity and expansion of the RFs of NRs, especially those with RFs located proximal to the tourniquet. Increases in spontaneous firing activity and expansion of the RFs of nociresponsive dorsal horn neurons receiving input from primary afferent nociceptors proximal to the tourniquet may explain, in part, the neurophysiologic mechanism of tourniquet-related pain.     

Clonidine versus ketamine to prevent tourniquet pain during intravenous regional anesthesia with lidocaine

BACKGROUND AND OBJECTIVES: Both clonidine and ketamine have been found to prolong the action of local anesthetics through a peripheral mechanism. Our study compares the efficacy of a low dose of clonidine or ketamine separately added to intravenous regional anesthesia (IVRA) with lidocaine to prevent tourniquet pain. METHODS: We conducted a prospective randomized double-blinded study in 45 patients undergoing hand or forearm surgery, with anticipated duration exceeding 1 hour under IVRA. Proximal cuff inflation of a double tourniquet was followed by administration of 40 mL of lidocaine 0.5% and either saline, 1 microg/kg clonidine, or 0.1 mg/kg ketamine. When anesthesia was established, the inflation of the proximal and distal cuff was interchanged. Thereafter, tourniquet pain was rated on a visual analog scale (VAS) every 10 minutes. Intraoperatively, boluses of 25 microg fentanyl were provided for tourniquet pain treatment when required, and total fentanyl consumption was recorded. RESULTS: Patients receiving plain lidocaine persistently reported the highest pain scores among groups (P <.001) 20 minutes after distal cuff inflation. Differences between the groups with additional treatment were noted 50 minutes after distal cuff inflation and until the end of the observation, with significantly lower VAS ratings (P <.001 to P <.01) in ketamine-treated patients. Total fentanyl consumption was significantly decreased by ketamine (70.00 +/- 25.35 microg) or clonidine (136.67 +/- 39.94 microg) compared with the plain lidocaine group (215.33 +/- 52.33 microg) (P <.001 between all groups). CONCLUSIONS: The addition of clonidine 1 microg/kg or ketamine 0.1 mg/kg to lidocaine for IVRA delays the onset of unbearable tourniquet pain and decreases analgesic consumption for tourniquet pain relief, although ketamine has a more potent effect.     

Impact of neoadjuvant chemoradiation on anal sphincter function in patients with carcinoma of the midrectum and low rectum

HYPOTHESIS: Preoperative chemoradiation for patients with stage II and III midrectal and low rectal cancer may improve survival and decrease local recurrence rate. We evaluated the long-term impact of neoadjuvant chemoradiation on anal sphincter function. DESIGN: Prospective analysis. SETTING: Tertiary referral center. PATIENTS: From March 1, 1996, to January 31, 2002, 50 patients with midrectal and low rectal cancer who underwent total mesorectal excision were prospectively enrolled. INTERVENTIONS: Patients received either surgical therapy alone (group 1, n = 22) or preoperative, combined chemoradiation (group 2, n = 28). Group 2 was divided into patients with midrectal (group 2A, n = 14) and low rectal (group 2B, n = 14) cancer. Anorectal manometry was performed preoperatively and a median of 384 days postoperatively. MAIN OUTCOME MEASURES: Anal resting pressure, squeeze pressure, anal sphincter vector volumes, length of the high-pressure zone, sensory threshold of the pouch, and rectal capacity. RESULTS: Preoperative manometric values were comparable between the groups. No statistically significant manometric differences occurred in group 1 postoperatively. Mean resting pressure (preoperative and postoperative, respectively: 89 +/- 35 mm Hg, 53 +/- 17 mm Hg), resting vector volume (605 +/- 324 cm( 3), 142 +/- 88 cm(3)), and maximal tolerable volume (144 +/- 29 mL, 82 +/- 44 mL) decreased significantly in chemoradiated patients postoperatively (P<.05). Manometric values of group 2B patients remained stable postoperatively, while mean resting pressure (73 +/- 22 mm Hg vs 52 +/- 14 mm Hg) and resting vector volume (631 +/- 288 cm(3) vs 145 +/- 78 cm(3)) decreased significantly in group 2A patients (P<.001). CONCLUSIONS: Total mesorectal excision does not influence anal sphincter function during long-term follow-up. Neoadjuvant chemoradiation results in disordered anal sphincter function in patients with midrectal cancer. Low and rectoanal anastomosis seems to obtain better anal sphincter function than higher anastomosis in chemoradiated patients.     

Noninvasive measurements of intramuscular pressure using pulsed phase-locked loop ultrasound for detecting compartment syndromes: a preliminary report

OBJECTIVES: To develop a human model for compartment tamponade and test the efficacy of ultrasonic pulsed phase-locked loop (PPLL) fascial displacement waveform analysis for noninvasive measurement of intramuscular pressure (IMP). DESIGN: Human subject experiment. SETTING: University Level 1 trauma center. PARTICIPANTS: Nine male and 1 female volunteers (age 20 to 59),3 male acute compartment syndrome (ACS) patients (age 31 to 38). INTERVENTION: Thigh tourniquet was inflated in a stepwise fashion from 40 to 100 mm Hg to increase IMP transiently in volunteers. MAIN OUTCOME MEASUREMENTS: Invasive IMP by slit catheter and PPLL fascial displacement waveform in volunteers with model ACS and patients with ACS. RESULTS: In the model compartment tamponade group, thigh cuff occlusion increased IMP in the anterior compartment from a mean of 12.1 mm Hg (SE = 1.5) to a mean of 27.4 mm Hg (SE = 2.4, N = 8, P < 0.0001). By fast Fourier transform, the ratio of the amplitude of the fundamental frequency to the amplitude of the second harmonic frequency of the fascial displacement waveform as measured by PPLL increased from a resting mean of 1.12 (SE = 0.07) to a mean of 1.85 (SE = 0.18) under the same protocol (N = 6, P = 0.001). Combined data with compartment syndrome patients revealed linear correlation between IMP and PPLL with an R value of 0.8887. CONCLUSIONS: Subarterial thigh cuff pressure causes a significant and transient increase in IMP, serving as a model for anterior compartment tamponade. PPLL is able to detect fascial displacement waveforms corresponding to arterial pulsation and furthermore distinguishes between normal and elevated IMP. There is a linear correlation between PPLL measurements and invasive IMP. The PPLL shows potential utility as a device for noninvasive measurement of IMP for detecting compartment syndromes.     

Tracheal tube cuff pressure

The effect of nitrous oxide on the cuff pressure was studied from the following points of view. One was the size of tubes and the type of cuff. The other was the effects of different gas mixture in the cuff. The changes of the cuff pressure were investigated using four types of tubes such as the largest standard cuffed tube which could be passed through the glottis, the 1.0 mm less in I.D. standard cuffed tube, the largest profile cuffed tube, and the 1.0 mm less in I.D. profile cuffed tube. There was no difference between the profile cuffed tube groups but in the standard cuffed tube groups, the cuff pressure increased from the beginning in 1.0 mm less I.D. tube group. Air, inhalation anesthetic gas (nitrous oxide:oxygen = 3:2) and mixtured gas (inhalation anesthetic gas and air = 4:3) were used to inflate the cuff. The cuff pressure was measured at the same patients. In the group of anesthetic gas, the cuff pressure decreased and in some cases, there occurred a leakage of gas. In the group of air, the cuff pressure increased as well as experiment I. However in the group of mixtured gas, there were almost no changes in the cuff pressure. This means that if the cuff is inflated with a mixtured gas in which nitrous oxide is under the equivalent condition, the cuff pressure would not change.