Is atrial function affected by conventional cardioplegic arrest?

Conventional cardioplegic arrest results in persistent atrial electrical and mechanical activity. This activity has been postulated to result in atrial ischemia which can induce postoperative arrhythmias and impair the transport function of the atrium. In this study, the effects of simple cardiopulmonary bypass (CPB) (seven pigs) and conventional cardioplegic arrest (CCA) (seven pigs) on right atrial function were evaluated. Function was assessed in an isolated right atrial preparation with a compliant balloon inserted via the superior vena cava. CCA for 1 hr produced significant deterioration in right atrial function (developed pressure 14.1 +/- 0.7 vs 18.9 +/- 0.8 mm Hg, P less than 0.05, diastolic pressure 10.0 +/- 1 vs 4.5 +/- 1.4 mm Hg, P less than 0.05, dP/dt 134 +/- 25 vs 187 +/- 19 mm Hg/sec, P less than 0.05 at a balloon volume of 20 ml after 1 hr of reperfusion). CPB alone caused no alteration in pressures in the right atrium but was associated with a late decrease in dP/dt (developed pressure 19.3 +/- 1.8 vs 18.9 +/- 0.8 mm Hg, diastolic pressure 4.0 +/- 1.2 vs 4.5 +/- 1.4 mm Hg, dP/dt 148 +/- 18 vs 187 +/- 19, P less than 0.05 at a balloon volume of 20 ml at a time corresponding to 1 hr of reperfusion in the CCA group). These results are consistent with the postulate that conventional techniques of cardioplegic arrest are associated with ischemic dysfunction of the right atrium.     

Treatment of endolymphatic hydrops with cochleosacculotomy. Clinical results and experimental findings

Cochleosacculotomy was performed on 25 patients with Meniere's syndrome. Long-term relief of vertigo was obtained in 19 out of 23 (82%). Postoperatively dead ears occurred in three cases. The same operation was performed on 12 guinea pigs in which hydrops had been surgically induced by blockage of the endolymphatic duct and sac. All fistulas were healed and cochleosacculotomy did not decrease or prevent the induced endolymphatic hydrops in these animals. Although histologic confirmation of persistent fistulas in human ears is lacking, the relief of vertigo in patients may not be caused by "drainage" but, rather, by a nonspecific effect on the inner ear. Cochleosacculotomy gives results comparable with other nondestructive surgical procedures performed to suppress vertigo in Meniere's syndrome.     

Relationship between right and left-sided filling pressures in 1000 patients with advanced heart failure.

BACKGROUND: Elevated left ventricular filling pressures present a major target of therapy for symptomatic heart failure but are difficult to assess directly. Because the relationship of left- and right-sided pressures remains ill defined in chronic heart failure, this study compared 3 right-sided measurements (right atrial [RA] pressure, pulmonary artery systolic [PAS] pressure, and severity of tricuspid regurgitation [TR]) to the pulmonary capillary wedge (PCW) pressure. METHODS: Hemodynamic measurements and echocardiography were available from 1000 patients undergoing transplant evaluation. Right atrial and PAS pressure, and TR severity were compared to PCW pressure. For 754 patients undergoing repeat measurements, changes in RA and PAS pressures were compared to PCW changes. RESULTS: Right atrial pressure correlated with PCW pressure (r = 0.64), regardless of etiology or TR severity. Right atrial pressure changes correlated with PCW changes (r = 0.62). Discordance was defined as either RA > or = 10 mm Hg despite PCW < 22 mm Hg (6%) or RA < 10 mm Hg despite PCW > or = 22 mm Hg (15%). For detection of PCW > or = 22 mm Hg, positive predictive values were 88% for RA > or = 10 mm Hg, 95% for PAS > or = 60 mm Hg, and 79% for > or = moderate TR. Pulmonary artery systolic pressure correlated very closely with PCW (r = 0.79), and could be estimated as 2 x PCW. Reduction in PAS pressure during therapy was strongly determined by PCW pressure reduction (r = 0.67). CONCLUSIONS: Accurate estimation of RA pressure can potentially guide therapy of left ventricular filling pressures in approximately 80% of chronic heart failure patients without obvious non-cardiac disease. In this population, elevated PAS pressures are largely determined by elevated left-sided filling pressures.     

Relationship of right and left ventricular negative diastolic pressures, hypercontractility, and relief of outflow tract obstructions

Continuous postoperative right and left ventricular diastolic pressures were measured in 12 consecutive patients undergoing pulmonic valvotomy and in 13 consecutive patients undergoing membranectomy and myectomy for discrete subaortic stenosis. All 25 patients had positive preoperative diastolic ventricular pressures. Negative ventricular diastolic pressure was detected immediately postoperatively in all 25. The lowest left ventricular negative diastolic pressure was -38 mm Hg, and the lowest right ventricular negative diastolic pressure was -28 mm Hg. Intravenous administration of volume (blood) reduced the right ventricular negative diastolic pressure significantly (from -14.8 +/- 9.2 to -6.4 +/- 6.8 mm Hg, p less than 0.001) and decreased right ventricular rate of pressure rise from 1100 +/- 320 to 380 +/- 180. Left ventricular negative diastolic pressure was not significantly affected (from -17 +/- 11 to -14.7 +/- 11 mm Hg). Left ventricular negative diastolic pressure disappeared spontaneously 6 to 9 hours postoperatively in association with a spontaneous decrease of left ventricular rate of pressure rise (from 3450 +/- 610 to 2100 +/- 660 mm Hg/sec). We conclude that negative right and left ventricular pressures are common findings immediately after surgical relief of outflow obstructions. Hypercontractility is the main reason for these phenomena. Volume load reduces the right ventricular negative diastolic pressure, but has insignificant effect on left ventricular negative diastolic pressure. The pathogenesis of the hypercontractility is discussed.     

Endoscopic endocrine neck surgery with carbon dioxide insufflation: the effect on intracranial pressure in a large animal model

BACKGROUND: Endoscopic endocrine neck surgery requires insufflation with carbon dioxide (CO(2)) at 10 to 15 mm Hg, which may decrease the cerebral venous return and increase intracranial pressure. This study evaluated the effect of CO(2) neck insufflation on intracranial pressure (ICP) and hemodynamic parameters. METHODS: Fifteen pigs underwent endoscopic thyroid dissection. Insufflation was performed with CO(2) at 0 (sham), 10, 15, and 20 mm Hg and with helium at 20 mm Hg with 3 pigs in each group. ICP, mean arterial pressure, central venous pressure (CVP), cardiac output, and blood gas were measured at baseline, 30, 60, and 120 minutes. RESULTS: There were no differences in mean ICP between the sham group and CO(2) insufflation at 10 mm Hg. Mean ICP increased significantly with CO(2) at 15 and 20 mm Hg and with helium at 20 mm Hg. A significant increase in CVP occurred in pigs operated with CO(2) at 20 mm Hg. We observed jugular vein collapse under all insufflation pressures; however, pigs operated at 10 mm Hg were able to maintain an intermittent blood flow. CONCLUSIONS: A severe increase in ICP occurs with insufflation pressures higher than 15 mm Hg, possibly as a result of decreased cervical venous blood flow. Carbon dioxide insufflation up to 10 mm Hg does not alter ICP and is recommended for clinical application in endoscopic neck surgery.     

Vasotrac arterial blood pressure and direct arterial blood pressure monitoring during liver transplantation

During liver transplantation two arterial catheters are often placed. The Vasotrac is a noninvasive monitor that provides radial arterial blood pressures by a tonometric method. We investigated whether the Vasotrac would be an accurate substitute for an arterial catheter by comparing Vasotrac blood pressures with simultaneous direct radial blood pressures recorded from the contralateral arm in 14 patients undergoing liver transplantation. Correlation between the two methods was calculated and a Bland-Altman analysis performed to assess agreement. A total of 6468 simultaneous measurements were made over a duration of 1.5-7.5 h per case. For mean arterial blood pressure 57% of Vasotrac measurements were within 10% of direct arterial measurement. Correlation (r) was 0.82. Vasotrac bias was +5.4 mm Hg and limits of agreement were +/-18.6 mm Hg. For systolic arterial blood pressure 65% of Vasotrac measurements were within 10% of direct arterial measurement. Correlation was 0.78. Vasotrac bias was +7.6 mm Hg and limits of agreement +/-25 mm Hg. For diastolic arterial blood pressure 57% of Vasotrac measurements were within 10% of direct arterial measurement. Correlation was 0.82. Vasotrac bias was +3.3 mm Hg and limits of agreement +/-15 mm Hg. We conclude that the Vasotrac is not adequately accurate to substitute for direct arterial blood pressure monitoring in liver transplantation.     

Effect of an upper-arm constricting device on arm blood pressure measurements

Thousands of blood pressure measurements are done daily without the patients' disrobing. This study was therefore undertaken to determine the validity of such measurements, especially those taken when the patient's armsleeve has been rolled up onto the proximal aspect of the arm. An inflatable constricting device was applied to the proximal aspect of the arm and a standard sphygmomanometer was applied distal to the inflatable cuff. The constricting cuff was inflated to 0, 20, 40, 60, 80, and 100 mm Hg in random sequence, and the blood pressure was recorded at each level. Statistically significant elevations in the mean systolic blood pressure were detected at proximal constricting pressures of 80 mm Hg (P less than .01) and 100 mm Hg (P less than .001), and in the mean diastolic blood pressure at 20 mm Hg (P less than .005). However, the magnitude of the elevations was small: 3.9, 4.4, and 2.5 mm Hg, respectively. We conclude that though a proximal constricting device may induce statistically significant alterations in blood pressure measurements these alterations are small and not likely to affect treatment decisions.     

Right heart function during prosthetic left ventricular assistance in a porcine model of congestive heart failure.

A left ventricular assist device was used to produce a 90% reduction in peak systolic left ventricular pressure in pigs with congestive heart failure, and the resultant effects on right ventricular function were determined. Initially, eight farm pigs underwent rapid ventricular pacing at 230 beats/min for 7 days to produce congestive heart failure. When compared with an independent series of normal pigs, cardiac output in the paced animals was 33.3% less (2.2 +/- 0.2 versus 3.3 +/- 0.5 L/min; p less than 0.05), left ventricular end-diastolic pressure was elevated (13.8 +/- 3.5 versus 6.6 +/- 1.8 mm Hg; p less than 0.05), and the slope of the right ventricular global stroke work curve was significantly depressed (0.004 +/- 0.001 versus 0.033 +/- 0.003 joules/mm Hg; p less than 0.05). Next, the left ventricular assist device was connected between left ventricular apex and ascending aorta and left ventricular pressure was reduced from 92.0 +/- 3.8 to 10.5 +/- 2.2 mm Hg, while systemic arterial pressure was maintained constant. This led to a further impairment in cardiac output (-14%), mean arterial pressure (-15%), and the slope of the right ventricular global stroke work curve (-50%). Under each condition, right ventricular preload recruitable stroke work and end-systolic pressure-dimension relationships were studied in three different regions on the right ventricle during both steady-state and transient inferior vena caval occlusion. In the right ventricular septal-free wall dimension, left ventricular pressure unloading resulted in a 47.5% +/- 5.4% (p less than 0.05) reduction in the slope and 20.1% +/- 4.8% (p less than 0.05) increase in the dimension intercept of the preload recruitable stroke work relationship. There was also a 44.6% +/- 4.8% (p less than 0.05) reduction in the slope and 15.6% +/- 2.8% (p less than 0.05) increase in the dimension intercept of the end-systolic pressure-dimension relation. These slope changes plus reductions in cardiac output and in global stroke work, which are indicative of impaired right ventricular function during left ventricular pressure unloading in the congestive heart failure pigs, are not seen in normal hearts, whereas the intercept changes associated with leftward septal shift are present in both. These results suggest that anatomic ventricular interactions have a more significant role in heart failure than in the normal heart in determining overall right ventricular function during left ventricular assist device support.     

Usefulness of right ventricular indices in early diagnosis of cardiac tamponade.

Early diagnosis of postoperative cardiac tamponade is impeded by its clinical similarity to left ventricular failure. Moreover, the hemodynamic changes necessary to diagnose cardiac tamponade are detected by conventional monitoring technique only after clinical compromise. Early signs of cardiac tamponade and left ventricular failure were studied with emphasis on right ventricular function in anesthetized dogs. One group (n = 20) had cardiac tamponade produced by incrementally increasing pericardial pressure (2 to 20 mm Hg), and another group (n = 20) had acute left ventricular failure produced by successive ligation of the anterior descending coronary artery at the lower, middle, and upper thirds. Besides standard hemodynamic measurements, right ventricular function was examined with a rapid-response thermodilution catheter. During cardiac tamponade, cardiac output, right ventricular ejection fraction, right ventricular stroke volume, and right ventricular end-diastolic volume were significantly decreased from baseline values after a pericardial pressure of 8 mm Hg or more (p less than 0.05). Right atrial and pulmonary arterial pressures were not significantly elevated until 14 and 20 mm Hg of pericardial pressure, respectively. Although cardiac function in the left ventricular failure group was reduced after each ligation, right ventricular ejection fraction remained unchanged. This study suggests that right ventricular indices may facilitate earlier diagnosis of cardiac tamponade with greater accuracy.     

Comparison of femoral and carotid blood pressure during laparoscopy in piglets

PurposeThe impact of a capnoperitoneum on the known blood pressure (BP) difference of the upper and lower limb was studied in piglets.MethodsEleven German Landrace piglets (body weight, 4.3-7.4 kg; mean body weight, 6.2 kg) were studied. Arterial lines were placed in the right carotid and right femoral artery for pressure monitoring. Intraabdominal pressure levels were increased in steps of 6 mm Hg up to 24 mm Hg.ResultsWe found that elevated intraabdominal pressures up to 24 mm Hg did not change the preexisting systolic BP difference between the carotid and femoral arteries. Systolic femoral artery pressure constantly remained 5% higher than its carotid counterpart. In addition, mean and diastolic values were not affected.ConclusionsArterial BP measurements recorded at the legs of piglets when abdominal pressure is increased by up to 24 mm Hg can be used for intraoperative assessment of systemic arterial BP.     

Effectiveness of the ultrasonic coagulating shears, LigaSure vessel sealer, and surgical clip application in biliary surgery: a comparative analysis

Advancements in laparoscopic surgery are often dictated by the limitations of technical instrumentation. Energy sources other than electrosurgery have become popular with the promise of quick and effective vascular control. With their success surgeons have begun using these on structures other than blood vessels with little or no data establishing their efficacy or safety. This study evaluates alternative energy sources in sealing ductal structures for possible use in liver or gallbladder surgery. After elective cholecystectomy cystic ducts (n = 45) were resealed ex vivo with surgical clips (n = 14), ultrasonic coagulating shears (n = 16), or electrothermal bipolar vessel sealer (n = 15), and bursting pressures were measured. Nineteen additional human cystic ducts were randomized to seal by ultrasonic coagulating shears (n = 9) or electrothermal bipolar vessel sealer (n = 10) and fixed in 10 per cent buffered formalin for histologic evaluation of thermal spread (mm). After this nine adult pigs were randomized to laparoscopic ligation and transection of the common bile duct using surgical clips (n = 3), ultrasonic coagulating shears (n = 3), or electrothermal bipolar vessel sealer (n = 3). The animals underwent necropsy for assessment of seal integrity on the sixth postoperative day. In the ex vivo study the mean cystic duct bursting pressure was 621 mm Hg with surgical clips and 482 mm Hg with the electrothermal bipolar vessel sealer (P = 0.39). The mean cystic duct bursting pressure after ultrasonic coagulating shears was 278 mm Hg, which was statistically less than surgical clips (P = 0.007) and electrothermal bipolar vessel sealer (P = 0.02). The mean thermal spread was 3.5 mm for ultrasonic coagulating shears and 13.4 mm for electrothermal bipolar vessel sealer (P = 0.0002). All animals undergoing ligation and transection of the common bile duct with ultrasonic coagulating shears and electrothermal bipolar vessel sealer developed bile peritonitis by postoperative day 6 as a result of seal leak. All animals undergoing surgical clip ligation and transection of the common bile duct maintained seal integrity. The mean common bile duct pressure above the surgical clip was 12 mm Hg (range 10-14). In conclusion the acute ex vivo study demonstrated a significant difference in the cystic duct bursting pressure between surgical clips and ultrasonic coagulating shears and between electrothermal bipolar vessel sealer and ultrasonic coagulating shears. The ultrasonic coagulating shears and electrothermal bipolar vessel sealer failed to maintain seal integrity in the in vivo animal study. Given the failure of the ultrasonic coagulating shears and electrothermal bipolar vessel sealer in the animal model these energy sources should not be used for transection of the cystic duct or major hepatic ducts during hepatobiliary surgery.     

体外模拟二氧化碳气腹对人胃癌细胞迁移运动的影响

目的探讨通过体外模拟气腹环境，观察不同压力二氧化碳（CO2）和氦气（He）对胃癌细胞MKN-45迁移运动的影响。方法将MKN-45细胞置于充满CO2或He的密闭培养箱中，按模拟气腹种类不同分为对照组、CO2气腹组和He气腹组，模拟气腹压力分别12mm Hg和15mm Hg，作用时间均为4h。于处理后用血气分析仪检测培养液pH值；用Transwell法观察细胞迁移运动变化。结果处理结束后即刻检测，CO2组细胞培养液呈酸性，He组细胞培养液呈碱性。CO2组和He组在12mm Hg压力下MKN-45细胞穿过滤膜的数量较对照组差异无明显统计学（P〉0．05），CO2 15mm Hg组细胞穿过滤膜的数量较对照组明显减少（P〈0．01）；He 15mm Hg组与对照组差异无明显统计学（P〉0．05）。结论在临床常用气腹压力下（12mm Hg）CO2对胃癌细胞迁移运动无明显影响。     

Effects of endolymphatic-perilymphatic fistula on endolymphatic hydrops in guinea pig.

The endolymphatic-perilymphatic shunt operation between the scala media and scala tympani was performed in 22 guinea pigs with endolymphatic hydrops induced by the silver nitrate injection method 2 months before the operation. Two (n = 10), 7 (n = 6), and 28 (n = 6) days after the operation, the condition of the fistula and the inner ear pathology were studied histopathologically. In half of the animals, the fistula was open, whereas in the other half, the fistula was closed. In the group examined after 2 postoperative days, the animals with open fistulas showed a slight collapse of Reissner's membrane, which might indicate that excess endolymph escaped through the fistula into the scala tympani. In the groups examined later, especially in the group examined after 28 postoperative days, the animals showed distention of hydrops despite preservation of the fistula. Moderate-to-severe degenerative changes of the organ of Corti, macula sacculi, and stria vascularis were observed in the vicinity of the fistula. We conclude from this study that the endolymphatic-perilymphatic fistula created inside the cochlea apparently was not sufficient to reduce the hydrops. Rather, it caused degenerative changes of the inner ear structure. This type of surgery is not suitable for Meniere's disease.     

Assessment of arterial obstruction in vessels supplying the fingers by measurement of local blood pressures and the skin temperature response test--correlation with angiographic evidence.

The systolic blood pressure measured in the fingers and wrists by the spectroscopic method and in the arm by auscultation were correlated with angiographic evidence of organic arterial obstruction in 29 patients. The pressures also were measured in 14 normal people. Results in the normal people suggest that a difference of more than 15 mm. Hg between the pressure measured simultaneously in corresponding fingers (or any two or more fingers), an absolute digital pressure less than 70 mm. Hg, or wrist-to-digit gradient of more than 30 mm. Hg, all in the warm subject and warmed hand, indicated the presence of organic obstruction. These criteria indicated the presence of organic arterial obstructive disease in 25 of 26 hands with definite angiographic evidence of it. The pressures were "normal" in five hands with no angiographic evidence of organic arterial obstruction. The digital skin temperature response to indirect heating was much less successful than were pressure measurements in identifying fingers with organic arterial obstructive disease.     

U-74,500A inhibition of burn-induced cardiac dysfunction.

Our previous studies suggest that oxygen-derived free radicals, particularly the hydroxyl radical, play a major role in cardiac dysfunction which is characteristic of burn injury. In this present study, we examined the effects of U-74,500A (U7), a 21-aminosteroid, nonglucocorticoid on ventricular contraction and relaxation recovery from burn injury. Parameters measured included left ventricular pressure (LVP) and the maximal rate of LVP rise (+dP/dt max) and fall (-dP/dt max). Full-thickness burns comprising 45% of the total body surface area (burn groups, N = 69) or 0% for controls (Group 1, N = 8) were produced in guinea pigs. In Group 2, 20 burned guinea pigs were not fluid resuscitated (vehicle only) and served as untreated burns; in Group 3, 11 burned guinea pigs received U7 alone (2.5 mg/kg in 0.01 N HCl iv). Eleven burned guinea pigs were resuscitated with vehicle plus 4 ml lactated Ringer's (LR)/kg/% burn for 24 hr (Group 4); in Group 5, 14 guinea pigs were treated with U7 as described for Group 3 followed immediately by LR for 24 hr as described for Group 4. In Group 6, U7 was administered immediately postburn as described for Group 3; and LR resuscitation, begun 1 hr postburn, was continued for 24 hr (N = 14). Compared to controls, untreated burn injury significantly impaired cardiac function as indicated by a fall in LVP (74 +/- 3 vs 60 +/- 4 mm Hg, P less than 0.05) and +/- dP/dt max (1126 +/- 51 vs 1011 +/- 39 and 1159 +/- 53 vs 993 +/- 59 mm Hg/sec, P less than 0.05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Retroperitoneoscopy versus laparoscopy in piglets: ventilatory and thermic repercussions.

BACKGROUND/PURPOSE: Endoscopic surgery of the retroperitoneal space in children is developing. During preliminary clinical experience, the authors were surprised by the differences observed in comparison with laparoscopic pneumpoeritoneum (PNOP); retropneumpoeritoneum (RPNOP) seemed to have less ventilatory repercussions. METHODS: The authors therefore undertook a study on animal models. Six suckling pigs, newly weaned, each weighing 10 kg successively underwent, at 8-day intervals and in random sequence, a right RPNOP with kidney and vena cava dissection, with insufflation of CO2 at 10 mm Hg of pressure and a PNOP with the same pressure of 10 mm Hg. RESULTS: P(ET)CO2 increased during PNOP, and it remained stable during during RPNOP (P = .035). The ventilatory peak airway pressures (PawP) increased during PNOP, but were not modified during RPNOP (P = .0001). Temperature decreased with time (P = .0001) without difference between the two procedures (P = .34). CONCLUSIONS: RPNOP was not associated with any adverse effects on the ventilation despite the insufflation pressure of 10 mm Hg, which allowed a satisfactory working area to be created. Operations by RPNOP could be developed in children with fewer respiratory repercussions than those observed during laparoscopy at an equivalent level of pressure.     

Saphenous vein rupture pressure, rupture stress, and carotid endarterectomy vein patch reconstruction

Early postoperative patch rupture is a catastrophic complication of carotid endarterectomy reconstruction with greater saphenous vein. Mechanical determinants of saphenous vein rupture were identified by structural measurements and the results applied to carotid endarterectomy patch geometry. Diameter and rupture pressure was measured in fresh saphenous vein segments from the ankle, knee, or thigh in 157 patients undergoing bypass operations. Circumferential hoop rupture stress was calculated and the results were applied to 157 carotid endarterectomy reconstructions. All vein ruptures were in the cylindric axis. The mean vein diameter was 4.58 mm. The mean vein rupture pressure was 2873 mm Hg (3.78 atm). Vein diameter was larger in the thigh than in the ankle or knee (p less than 0.01), but there was no significant difference in rupture pressure between veins from the three locations. Women had a smaller vein diameter than had men at all locations (p less than 0.01). There was a positive linear correlation between vein diameter and rupture pressure. The mean maximum diameter of curvature of 157 carotid endarterectomy reconstructions with a vein patch was 13.3 mm. Multiple random applications of the 157 veins to 157 carotid diameters predicted a mean patch rupture pressure of 1087 mm Hg (1.43 atm), 1163 mm Hg (1.53 atm) for men, and 866 mm Hg (1.14 atm) for women. Predicted vein patch rupture pressures less than 300 mm Hg were found in 5.7% of cases (8.8% women and 1.2% men). Only 0.6% of patients (1.8% women and 0% men) had a predicted rupture pressure less than 200 mm Hg. No veins with a diameter greater than or equal to 4.0 mm had a predicted patch rupture pressure less than 300 mm Hg. These results suggest that small-diameter saphenous veins have a higher risk of rupture when used as a carotid patch.     

Arterial PCO2 and cardiovascular function during endoscopic neck surgery with carbon dioxide insufflation.

BACKGROUND: Endoscopic parathyroidectomy and thyroidectomy were introduced into clinical practice in 1995. Concerns about the use of carbon dioxide insufflation in the neck exist owing to reports of potential adverse metabolic and hemodynamic changes. HYPOTHESIS: Carbon dioxide insufflation in the neck may cause adverse effects on hemodynamic and blood gas levels. These adverse effects may reflect the level of pressure and duration of insufflation. METHODS: Fifteen pigs, 5 per group, underwent endoscopic thyroidectomy at 10, 15, and 20 mm Hg. Partial pressure of carbon dioxide (arterial), pH, cardiac output, central venous pressure, heart rate, and mean arterial pressure (MAP) were measured at baseline, 1 and 2 hours after carbon dioxide insufflation, and 30 minutes after desufflation. RESULTS: At 10 mm Hg, PaCO2 increased slightly but not significantly, and neither acidosis nor adverse hemodynamic changes were observed. Hypercarbia, moderate acidosis, and a slight increase in MAP occurred in pigs undergoing surgery at 15 mm Hg (MAP increased to 88 +/- 2.4 mm Hg from a baseline value of 78 +/- 3.53 mm Hg; P<.05). Pigs undergoing surgery at 20 mm Hg experienced severe hypercarbia and acidosis, as well as a significant decrease in MAP (P<.05). Central venous pressure decreased at 1 hour (P<.05) and increased at 2 hours (P<.05) in pigs undergoing surgery at 15 and 20 mm Hg. After desufflation, PaCO2 and pH levels were normal for the 10 and 15 mm Hg groups, while pigs undergoing surgery at 20 mm Hg developed a higher degree of hypercarbia and acidosis (P =.001). CONCLUSIONS: Carbon dioxide neck insufflation is safe at 10 mm Hg. The use of insufflation pressures higher than 15 mm Hg should be avoided due to the potential risk for metabolic and hemodynamic complications.     

Overinflation of pneumatic antishock garments in the elderly

The hemodynamic effects of pneumatic antishock garment application in high-risk elderly patients were examined in 10 preoperative patients (mean age 66.5 +/- 6.4 years) with the pneumatic antishock garments uninflated, after 15 minutes of inflation to 50 mm Hg, and after 15 minutes of inflation to 75 mm Hg. After inflation, significant increases in right atrial pressure (89 percent), pulmonary capillary wedge pressure (34 percent), and mean pulmonary artery pressure (21 percent) were noted. Mean peripheral arterial pressure increased 11.2 percent. Depression of the cardiac index (18 percent), left ventricular stroke work (20 percent), and right ventricular stroke work (16.4 percent) with associated increases in total peripheral resistance (26 percent) and pulmonary vascular resistance (18 percent) occurred in 5 of 10 patients. Left ventricular function curves revealed a progressive decrease in ventricular function at 50 mm Hg and 75 mm Hg. We have concluded that the effect of the pneumatic antishock garment on myocardial function is variable and unpredictably dangerous in the elderly patient with diminished myocardial reserve. As no significant benefit was derived from inflation pressures greater than 50 mm Hg in these patients, the lowest combination of pressures producing the most efficacious results should be used.     

Release of the transverse carpal ligament alone is associated with elevated pressure beneath the distal volar forearm fascia in a cadaver model of carpal tunnel syndrome

PURPOSE: The purpose of this study is to determine whether release of the distal volar forearm fascia (DVFF) is necessary at the time of median nerve decompression for carpal tunnel syndrome. METHODS: Five fresh-frozen cadaver specimens were mounted vertically with the hand dependent and a 2.27-kg weight suspended from the fingers. A pressure sensor wire was used to measure pressures starting just distal to the transverse carpal ligament (TCL). The wire was withdrawn proximally in 5-mm increments and into the forearm until pressure was below 10 mm Hg. An incision in the forearm was extended distally until the pressure sensor was found. The distance from this point to the distal volar wrist crease was measured. The TCL was released, keeping the DVFF intact, and the experiment was repeated. Paired t-tests determined whether there were statistically significant differences between measurements before and after TCL release. RESULTS: Average peak pressure under the intact TCL was 57.8 +/- 10.1 mm Hg. Average peak pressure under the DVFF with the TCL intact was 61.2 +/- 43.6 mm Hg. Following release of the TCL, average peak pressure beneath the TCL significantly decreased to 14.0 +/- 9.0 mm Hg, whereas average peak pressure at the intact DVFF increased to 64.8 +/- 48.7 mm Hg. Average locations where DVFF pressure became less than 10 mm Hg with an intact TCL and with released TCL were 4.30 +/- 1.8 cm and 4.00 +/- 1.8 cm proximal to the distal volar wrist crease, respectively. There was no significant difference between DVFF pressures before or after TCL release. CONCLUSIONS: In a cadaver model of carpal tunnel syndrome, release of the TCL alone is associated with persistent pressures >30 mm Hg in the region of the DVFF. Release of the TCL did not significantly change the location of the pressure drop-off under the DVFF.