Endoscopic pelvic osteotomy for the treatment of hip dysplasia.

Adolescent and adult hip dysplasia can be surgically treated by rotating the acetabulum into a better weight-supporting position; however, open pelvic osteotomies are among the most invasive of all pediatric orthopaedic procedures. Endoscopic pelvic osteotomy offers the theoretical advantages of magnified visualization of the bone cuts, minimized surgical dissection, and rapid postoperative recovery. The technique of endoscopically assisted triple innominate osteotomy requires the combination of endoscopic skills and facility with more standard surgical approaches.

Quantitative changes in spinal canal dimensions using interbody distraction for spondylolisthesis.

STUDY DESIGN: An experimental study was performed using cadaveric lumbar spines to evaluate the effect of anteriorly or laterally placed interbody distraction implants on the alteration of spinal canal and neuroforaminal dimensions. OBJECTIVES: To quantify changes in the spinal canal and neuroforaminal dimensions using interbody fusion devices inserted at various configurations in cadaveric lumbar spines exhibiting degenerative spondylolisthesis. SUMMARY OF BACKGROUND DATA: Although several clinical studies have demonstrated successful treatment of degenerative spondylolisthesis with anterior interbody fusion, no study has shown the role of interbody distraction in improving lumbar spinal canal and foraminal stenosis. METHODS: Five fresh cadaver lumbar spines exhibiting a degenerative spondylolisthesis or retrospondylolisthesis were used for the study. Computed tomography scans of each specimen and a silicon mold of the left intervertebral foramens were repeated in a consistent manner after pure compressive load (150 lb) was applied to simulate physiologic load (intact case), after two BAK (Sulzer SpineTech Inc., Minneapolis, MN) distraction plugs were anteriorly inserted into the intervertebral disc space (anterior distraction cases), and after one long BAK cage was laterally inserted from the left side (lateral distraction case). The cross-sectional area of the spinal canal was measured from computed tomography images using National Institutes of Health image software (Bethesda, MD). The spinal canal volume was calculated using the cross-sectional area and total scan thickness. Left intervertebral foraminal volumes were calculated from the weight of the silicon mold injected into the foramen. Descriptive statistics and a Student's t test were used to detect statistical differences in the spinal canal and neuroforaminal volumes before and after interbody distraction. RESULTS: The cross-sectional canal area was significantly increased after anterior distraction (35.11%) and lateral distraction (33.14%). The spinal canal volume was markedly increased with anterior distraction (19.92%) and lateral distraction (21.96%). Left foraminal volume was also enhanced by 40.25% for anterior distraction and 41.03% for lateral distraction. CONCLUSIONS: Interbody distraction either by anteriorly inserted plugs or laterally inserted threaded cagescan immediately improve the narrowed canal area and increase spinal canal, as well as foraminal volume for lumbar degenerative spondylolisthesis or retro- spondylolisthesis.

Comparison of wounds created by non-bladed trocars and pyramidal tip trocars in the pig.

Wounds made by the Endopath nonbladed obturator, the Step trocar, and conventional pyramidal tip trocars were compared. The endopath nonbladed obturator and the Step trocar made wounds by separating tissue fibers, whereas the pyramidal tip trocar cut tissue fibers. The wounds of the Endopath nonbladed obturator and the Step trocar were similar in length but were narrower than wounds made by the pyramidal tip trocar. Further studies are needed to determine whether the wounds made by the Endopath nonbladed obturator and the Step trocar will have fewer complications than conventional pyramidal tip trocars.

Video-assisted thoracic diskectomy and anterior release: a biomechanical analysis of an endoscopic technique.

This study evaluates the residual biomechanical stability of the spine following multilevel anterior diskectomies and anterior longitudinal ligament release using video-assisted thoracoscopic surgery (VATS). Eighteen domestic pigs were randomly divided into three groups of six pigs. Group 1 underwent thoracic anterior release from T4-T9 using a left-sided VATS approach, group 2 underwent thoracic anterior release from T4-T9 via a traditional left thoracotomy (open), and group 3 did not undergo surgery and served as a control. After surgery, the animals were euthanized, and the thoracic spinal columns were harvested for biomechanical testing. Nondestructive testing was performed on all specimens in pure compression, flexion, extension, right lateral bending, and torsion. Specimens from group 1 had significantly lower stiffness values (P<.05) than the control group for all five test modes. These data demonstrate that adequate anterior release of the thoracic spine can be obtained with the VATS technique. Further prospective clinical studies on VATS are required before the widespread application of this technique.

Bradycardia induced by intravascular versus direct stimulation of the vagus nerve.

BACKGROUND: Electrical stimulation of the parasympathetic nervous system results in slowing of the heart. We sought to determine whether cardiac vagal efferent axons can be stimulated adequately to induce bradycardia without disturbing the integrity of the thorax. METHODS: Cardiodepressor effects elicited by direct stimulation of a vagus nerve in anesthetized dogs and pigs were compared with those generated when the same nerve was stimulated indirectly through bipolar electrodes placed in the adjacent superior vena cava. RESULTS: The heart rate of dogs decreased by about 80% when electrical stimuli were delivered to the right thoracic vagus at the level of the thoracic outlet through bipolar electrodes placed either in the adjacent superior vena cava (intravascular method) or directly on the nerve (direct method). Maximal responses were achieved with 10-V, 5-ms, and 20-Hz stimuli. In anesthetized pigs, similar bradycardia occurred when the right cervical vagus or the right cranial thoracic vagus was stimulated either directly or indirectly through the intravascular method. Atrial dysrhythmias occurred when the stimulating electrodes were placed by either method within 1 cm of the right atrium in both animal models. CONCLUSIONS: Controlled bradycardia can be induced during operation without the risk of generating cardiac dysrhythmias using electrical stimuli (10 V, 5 ms, and 10 to 20 Hz) delivered to the right cervical vagus nerve or the right cranial thoracic vagus nerve through adjacent intravascular electrodes.

Endoscopic discectomy increases thoracic spine flexibility as effectively as open discectomy. A mechanical study in a porcine model.

STUDY DESIGN: Two surgical techniques for anterior discectomy were compared biomechanically. The surgical procedures were performed in live, anesthetized, skeletally immature pigs. Spine flexibility was measured in vitro. OBJECTIVE: To determine whether endoscopic techniques for discectomy are as effective as open procedures in increasing spine flexibility. SUMMARY OF BACKGROUND DATA: Although studies have verified that discectomy increases spine flexibility, no study has confirmed whether endoscopic techniques increase flexibility as effectively as standard thoracotomy, which is a substantially different procedure. METHODS: The intervertebral disc between vertebrae T8 and T9 was resected from 30 live, anesthetized, adolescent pigs. In 15 pigs, the chest was opened via thoracotomy of the eighth rib, and the disc was excised. In the other 15 pigs, the disc was removed endoscopically. These motion segments and six intact controls were tested mechanically in side bending, flexion-extension, and axial rotation. RESULTS: No statistically significant differences in flexibility were found between open and endoscopic groups in any loading direction. The statistical power to detect a 20% difference between surgical groups was > or = 95%. CONCLUSIONS: Endoscopic and open techniques were equally effective in increasing spine flexibility. Because endoscopy may reduce surgical morbidity compared with open discectomy, these results support the use of endoscopy for the surgical correction of scoliosis before instrumentation.

Endoscopic ovariohysterectomy in two lions (Panthera leo).

Endoscopic techniques were used to ovariohysterectomize two hybrid Asian lions (Panthera leo) in order to reduce the risk of postoperative wound complications associated with standard surgical techniques. One of the lions was aged, overweight, and considered an anesthetic risk. The animals were anesthetized, intubated, catheterized intravenously, and placed in dorsal recumbency with the head lower (Trendelenburg position). Ventilation was assisted mechanically. Following abdominal insufflation, a surgical trocar was placed in the abdominal cavity. Two additional 12-mm surgical trocars were placed under direct visualization using a videoscope. The ovaries and uterus were removed endoscopically, and the abdominal cavity was inspected for hemorrhage under decreased insufflation pressure before closure. The surgery was complicated by obesity, by uterine enlargement from cystic endometrial hyperplasia and endometrial polyps, and by ovarian enlargement and fragility because of bilateral cystic rete ovarii. The procedure and anesthetic recovery were uneventful. Postsurgical recovery time and convalescence lasted less than 3 days, and the animals were reintroduced to an exhibit mate and placed on exhibit within 8 days. The technique is appropriate for use in lions, even those with pathologic reproductive changes, in zoos.

An animal model for teaching subfacial ligation of perforator veins to treat venous stasis ulcers.

Endoscopic subfacial ligation of perforator veins in the lower limb has been described in the treatment of venous stasis ulcer. An animal model to enable surgeons to become familiar with the surgical technique is presented. The model uses the porcine abdominal wall and allows practice in endoscopic dissection and ligation using appropriate instrumentation in an environment that is a reasonable surrogate for the human calf.

Video-assisted thoracic corpectomy and spinal reconstruction: a biomechanical analysis of open versus endoscopic technique.

The purpose of this study is to evaluate the technique of video-assisted thoracic surgery (VATS) to perform corpectomy and spinal reconstruction with the Harrington rod and polymethylmethacrylate construct, and to compare the biomechanical stability of the constructs created with both open thoracotomy and VATS technique. Fourteen farm-raised pigs were divided into two groups. Group I underwent thoracic corpectomy using a VATS approach and group II had the same procedure performed through a traditional thoracotomy. The stiffness (newtons per millimeter) for the non-destructive tests for each loading mode are flexion-compression (open 124.4 +/- 124.9; VAT 75.8 + 29.9); extension-compression (open 165.8 + 41.8: VATS 96.5 + 31.2); pure compression (open 231.4 + 126.4; VATS 264.6 + 184.3). The difference between group I (VATS) and group II (open) in extension compression is statistically significant. Although not statistically significant, the results also show the group II (open) specimens to be stiffer in flexion-compression and the group I (VATS) specimens to be stiffer in pure compression. Although corpectomy and spinal reconstruction can be performed with the VATS technique, the constructs obtained endoscopically may not have the same strength as those constructs obtained via an open procedure.

A comparison of the hemodynamic and ventilatory effects of abdominal insufflation with helium and carbon dioxide in young swine.

Abdominal CO2 insufflation has been shown to cause hypercarbia, acidemia, and decreased oxygenation in a pediatric animal model. Such metabolic derangements have prompted a search for alternative insufflation gases. This study compares the hemodynamic and ventilatory changes that occur during pneumoperitoneum with CO2 and helium. Four juvenile swine were intubated and given general anesthesia. Minute ventilation was adjusted to obtain a baseline Pco2 of between 32 and 36 mm Hg, and was kept constant for the duration of the experiment. The subjects initially were insufflated with CO2 or helium at a pressure of 10 mm Hg. Peak ventilatory pressure, end-tidal CO2 (ETCO2) arterial pH, Pco2, Po2, and right atrial and inferior vena caval pressures were measured before and during a 1-hour insufflation period. After desufflation, Pco2 and pH were restabilized. The same parameters were then measured during reinsufflation with the alternate gas. CO2 insufflation caused significant decreases in pH, from 7.51 +/- 0.03 to 7.32 +/- 0.06, and Po2 increased from 261 +/- 49 to 189 +/- 33 mm Hg. Pco2 increased from 35.0 +/- 1.4 to 57.9 +/- 6.3 mm Hg. ETCO2 also increased, from 29.0 +/- 2.2 to 47.2 +/- 5.0 mm Hg. Helium insufflation caused pH to decrease from 7.51 +/- 0.01 to 7.42 +/- 0.04. Pco2 increased from 32.8 +/- 0.8 to 43.5 +/- 3.9 mm Hg, and ETCO2 increased from 27.8 +/- 0.5 to 36.8 +/- 3.1 mm Hg. These alterations were significantly less than those with CO2 pneumoperitoneum. Po2 decreased as well-from 266 +/- 30 to 212 +/- 21 mm Hg. During insufflation with both gases, peak ventilatory pressure and right atrial pressure increased significantly. Abdominal insufflation with CO2 or helium causes hypercarbia, acidemia, and increased ETCO2 in this juvenile animal model. These derangements are significantly less with helium. This gas may prove to be the more suitable insufflation agent for pediatric patients.

A perfluorochemical emulsion for prehospital resuscitation of experimental hemorrhagic shock: a prospective, randomized, controlled study.

OBJECTIVE: To evaluate the efficacy of a novel, oxygen-transporting perfluorochemical emulsion as a prehospital therapy, using a canine hemorrhagic shock model based on compromised tissue oxygenation. DESIGN: Prospective, randomized, controlled study. SETTING: HemaGen animal laboratory. SUBJECTS: Sixteen healthy, adult male grade beagles (weight 8 to 14 kg). INTERVENTIONS: Administration of lactated Ringer's solution (n = 8), 15 mL/kg and perfluorochemical emulsion admixed with physiologic salts (n = 8), 15 mL/kg. MEASUREMENTS AND MAIN RESULTS: PaO2 increased significantly (p < .01) in the perfluorochemical-treated animals for 2 hrs after resuscitation. Mixed venous PO2 returned to preshock values in the perfluorochemical-treated dogs for 60 mins after fluid administration (p < .01). Normalization of hemodynamic variables was not observed in either group. Although not statistically significant, survival of the lactated Ringer's solution-treated animals was 63% compared with 100% for the perfluorochemical-treated dogs at 3 hrs after resuscitation. CONCLUSIONS: Resuscitation with a perfluorochemical emulsion augmented oxygen transport and restored global tissue oxygenation after massive hemorrhage, which translated into improved survival when compared with the group receiving an equal volume of lactated Ringer's solution.

Improved myocardial preservation by control of the oxidation-reduction potential.

Simple cold storage remains the current method of preservation of human heart allografts between removal and transplantation, but this technique is not adequate for prolonged periods of preservation. An alternative to cold storage is machine perfusion of the isolated organ. Although this technique has yielded promising results in kidney preservation, there is limited experience with the heart. One factor limiting the effectiveness of perfusion preservation is the toxicity of oxygen free radicals generated during the perfusion. The generation and reduction of these radicals results in an electron transfer, producing an electrochemical potential known as the redox potential. This study examines the role of machine perfusion in heart preservation with and without the use of a new electrochemical cell that is able to control the redox potential during the perfusion. Hearts were preserved for twenty-four hours by either simple cold storage (Group I), or by machine perfusion with redox monitoring (Group II), or redox control (Group III). Control of the oxidation-reduction potential of the perfusate during machine perfusion of isolated hearts resulted in significantly improved systolic and diastolic function after perfusion compared to hearts that underwent machine perfusion without redox control or simple cold storage.

Emergency treatment of urethral obstruction in male cats.

Cats with mild urethral obstruction are anesthetized, the obstruction removed and the bladder lavaged. Moderately affected cats are sedated and given IV fluids, and usually return to normal soon after the obstruction is removed. Severely affected cats are given IV fluids, NaHCO3 and Ca gluconate, sedated or anesthetized and unblocked. Fluid administration is continued to avoid renal failure. The bladder can be expressed 3-4 times daily or bethanechol given to aid recovery of detrusor muscle function. Halothane, 1% thiopental or thiamylal, or ketamine-acepromazine can be used to anesthetize blocked cats. An 18- or 20-ga, 2 1/2-inch over-the-needle catheter or a lacrimal needle is used to relieve the obstruction, after which a 3 1/2-Fr Silastic or vinyl catheter is used for catheterization and bladder lavage with sterile saline. Cystotomy allows recuperation before definitive corrective surgery.

Cold blood potassium diltiazem cardioplegia.

Despite the use of cold blood potassium (CBK) cardioplegia, the severely impaired myocardium and/or long ischemia time continue to be a challenge. Because of the association of Ca++ with cell injury and death, the use of Ca++ entry blockers is logical. Investigation of cold blood diltiazem (CBD) revealed no advantages over CBK cardioplegia. The combination of potassium and diltiazem is appropriate because of their different mechanisms of action. Ten dogs had 1 hour of myocardial ischemia with topical ice (temperature 7 degrees +/- 2 degrees C) after coronary perfusion with 200 ml of cold blood (5 degrees +/- 1 degree C) containing potassium (30 mEq/L) and diltiazem (400 micrograms/kg). Eight dogs had 2 hours of ischemia after perfusion with 200 ml of cold blood containing potassium (30 mEq/L) and diltiazem (200 micrograms/kg) and reperfusion every 30 minutes with 100 ml of cold blood containing KCl (30 mEq/L) and diltiazem (100 micrograms/kg). Six dogs received the same treatment as the previous group except that diltiazem was increased to 1,600 micrograms/kg for all four perfusions. Baseline studies were repeated after 60 minutes of reperfusion without the use of Ca++ or inotropic agents. Heart rate, peak systolic pressure, velocity of the contractile element (Vce), maximum velocity of contractile element (Vmax), peak +dp/dt, peak -dp/dt, dp/dt over common peak isovolumic pressure, left ventricular compliance, stiffness and elasticity, and heart water were unchanged from control. Coronary vascular resistance was unchanged in Groups 1 and 2 but declined in Group 3. Creatine phosphate was preserved during ischemia; adenosine triphosphate (ATP) declined. With reperfusion there was continued fall in ATP, ADP, and the adenosine pool. Ultrastructure was well preserved. In 16 of 24 dogs defibrillation was not required, whereas all 48 dogs with CBK and all 13 with CBD required defibrillation. These data suggest that the addition of diltiazem to CBK provides more effective cardioplegia (preservation of creatine phosphate), although ATP and the adenosine pool continued to decline with reperfusion.

Diagnostic peritoneal lavage before and after abdominal surgery in dogs.

Complete blood cell counts and peritoneal lavage (PL) were done 2 days before and 2 days after abdominal surgery. Abdominal surgery consisted of intestinal resection/anastomosis and cystotomy in 18 dogs in group 1 and gastrotomy, pyloromyotomy, and repair of diaphragmatic laceration in 20 dogs in group 2. Insertion of the dialysis catheter for PL preoperatively in a right paramedian location resulted in more PL samples contaminated with blood than when the catheter was inserted on the abdominal midline. The number of nucleated cells found in PL fluid when the catheter was inserted in a right paramedian location was not significantly different (P less than 0.05) from that observed in PL fluid collected after insertion of the catheter through the abdominal midline. The predominant cell type in preoperative PL fluid was the segmented neutrophil. In groups 1 and 2, WBC counts and nucleated cell counts in PL fluid were significantly increased (P less than 0.05) postoperatively. Segmented neutrophils and macrophages were most frequently present in postoperative PL fluid. Degenerative neutrophils in postoperative PL fluid were associated with the appearance of immature neutrophils in the blood and increased rectal temperature. Dogs with these findings appeared to have more peritoneal inflammation at necropsy than did others in their groups. Concentrations of alkaline phosphatase, alanine aminotransferase, amylase, and creatinine in preoperative PL fluid were extremely low. Except for creatinine in group 2, all of these were significantly increased (P less than 0.05) postoperatively. The complication rate associated with the performance of PL on dogs postoperatively was not greater than that which was observed preoperatively.

Canine septic peritonitis: treatment with flunixin meglumine.

The efficacy of treating acute lethal peritonitis with flunixin meglumine was investigated in dogs. Following intraperitoneal administration of Escherichia coli organisms in a sterile fecal suspension, eight dogs were left untreated and eight dogs were treated with flunixin meglumine (2.2 mg/kg) at 15 min and 12 hr. Another eight dogs were treated with flunixin meglumine (2.2 mg/kg) at 15 minutes and 12 hours, and with gentamicin sulfate (2.2 mg/kg) at 15 min, 6 hr, 12 hr, and 18 hr postsepsis. Untreated dogs lived 5-12 hr and rapidly developed fever, hypoglycemia, metabolic acidosis, hypotension, and cardiac dysfunction. Dogs treated with flunixin meglumine had longer survival times (9-24 hr), lower body temperatures, higher stroke indexes, higher mean arterial pressures, and higher blood pH values than untreated dogs. Six of the eight dogs treated with flunixin meglumine and gentamicin sulfate lived 24 hr. Compared to untreated controls, dogs in this group had slower development of hypoglycemia, lower body temperatures, higher stroke volumes, higher mean arterial pressures, and only temporary development of metabolic acidosis.

Cardiopulmonary effects of thiopental/lidocaine combination during anesthetic induction in the dog.

The cardiopulmonary effects and tendencies to produce ventricular arrhythmias were evaluated in 13 dogs given a surgical plane of anesthesia by thiopental (IV) or a combination of thiopental and lidocaine (IV). Thiopental (22 mg/kg of body weight) was compared with a combination of thiopental (11 mg/kg) and lidocaine (8.8 mg/kg). Preanesthetic agents were not given. Both methods for IV anesthesia provided a smooth induction suitable for easy intubation. The thiopental/lidocaine combination had a shorter duration, produced no arrhythmias, and resulted in less cardiopulmonary depression than did thiopental alone. Bigeminy developed after intubation during 19 of 20 thiopental inductions as compared with that in 0 of 22 thiopental/lidocaine inductions. The bigeminies were preceded by systemic hypertension and tachycardia which developed as the trachea was being intubated. The increase in aortic pressure and heart rate was minimal after intubation during the thiopental/lidocaine inductions. Five minutes after administration of thiopental alone, increases in heart rate, aortic pressure, total peripheral vascular resistance, and left ventricular systolic and end-diastolic pressures were observed. When these increases in rate, preload, and afterload were considered in relation to a stabile maximum positive first derivative of left ventricular pressure, left ventricular contractility was considered to be decreased. Mild respiratory acidosis and hypoxemia were present at 5 and 10 minutes after thiopental induction. Because the combination of thiopental/lidocaine had less cardiopulmonary depressive effects and protected against arrhythmias, it would appear to be a good method for anesthetic induction of the patient with cardiopulmonary disease. In the patient with normal cardiopulmonary function, thiopental produces only a moderate and reversible depression.

Cardiopulmonary effects of intravenous xylazine, ketamine, and atropine in the dog.

Atropine (0.04 mg/kg of body weight) and the combination of xylazine (1.1 mg/kg) and ketamine (11 mg/kg) were administered IV to dogs, and cardiopulmonary variables were measured. The drug combination caused hypoventilation, as reflected by increased PaCO2 and a 30% decrease in cardiac index, whereas arterial pressure, left atrial pressure, and peripheral resistance were increased. These variables began returning toward base-line values during anesthesia and were not different from base-line values by 30 minutes.

Congenital portacaval shunts in two cats: diagnosis and surgical correction.

Congenital portacaval shunts causing signs of hepatic encephalopathy were diagnosed and surgically corrected in 2 cats. A tentative diagnosis of portacaval shunt in each case was based on history, results of physical examination, and a high venous ammonia concentration. A definitive diagnosis was established by mesenteric portography and by direct visualization of the shunt vessel during surgery.