Forced-air warming and ultra-clean ventilation do not mix: an investigation of theatre ventilation, patient warming and joint replacement infection in orthopaedics.

We investigated the capacity of patient warming devices to disrupt the ultra-clean airflow system. We compared the effects of two patient warming technologies, forced-air and conductive fabric, on operating theatre ventilation during simulated hip replacement and lumbar spinal procedures using a mannequin as a patient. Infection data were reviewed to determine whether joint infection rates were associated with the type of patient warming device that was used. Neutral-buoyancy detergent bubbles were released adjacent to the mannequin's head and at floor level to assess the movement of non-sterile air into the clean airflow over the surgical site. During simulated hip replacement, bubble counts over the surgical site were greater for forced-air than for conductive fabric warming when the anaesthesia/surgery drape was laid down (p = 0.010) and at half-height (p < 0.001). For lumbar surgery, forced-air warming generated convection currents that mobilised floor air into the surgical site area. Conductive fabric warming had no such effect. A significant increase in deep joint infection, as demonstrated by an elevated infection odds ratio (3.8, p = 0.024), was identified during a period when forced-air warming was used compared to a period when conductive fabric warming was used. Air-free warming is, therefore, recommended over forced-air warming for orthopaedic procedures.

Intraoperative small-dose ketamine does not reduce pain or analgesic consumption during perioperative opioid analgesia in children after tonsillectomy.

OBJECTIVE: Ketamine inhibits the NMDA receptors via non-competitive antagonism, resulting in an antihyperalgesic effect achieved by doses of ketamine much smaller than are required for analgesia. The aim of this study was to determine the extent to which small-dose ketamine, when used in conjunction with remifentanil, has a morphine-sparing effect in the perioperative period. MATERIALS AND METHODS: In this randomized, double-blind, placebo-controlled prospective study, we enrolled 40 children undergoing tonsillectomy. Anesthetic care was standardized. Intraoperative analgesia was provided with remifentanil 0.5 microg x kg(-1) followed by an infusion of 0.25 microg x kg(-1) x min(-1). Group I (ketamine, n = 20) received a bolus dose of ketamine 0.5 mg x kg(-1) followed by a continuous infusion of 2 microg x kg(-1) x min(-1) before start of surgery. The infusion was stopped when surgery ended. Group II (placebo, n=20) received normal saline in the same manner. Pain was assessed postoperatively using the Children's Hospital Eastern Ontario Pain Scale (CHEOPS; range of scores 4 13), and total morphine consumption was recorded in the postanesthesia care unit (PACU). Patients were transferred to the ward and morphine was administered via a patient-controlled analgesia (PCA) device and analgesia was recorded using a visual analogue scale (VAS) (0 - 10). RESULTS: Intraoperative remifentanil consumption was not different between the ketamine group (0.29+/-0.09 microg x kg x min(-1) ) and the control group (0.24+/-0.07 microg x kg x min(-1)). There were no significant differences between CHEOPS scores and VAS score between the two groups. The total mean morphine consumption in the ward was not significantly different between the two groups: 376.5 +/-91.6 microg x kg(-1) with ketamine and 384.4+/-97.3 microg x kg(-1) with placebo. The time-to-first analgesic requirement was also similar in both groups. CONCLUSIONS: Small-dose ketamine did not decrease postoperative pain after tonsillectomy in children when added to a continuous intraoperative remifentanil infusion.

A delayed cardiopulmonary reaction to an intravenous immunosuppressant thymoglobulin after pancreas transplant.

IMPLICATIONS: Adverse cardiopulmonary reaction to an intravenous immunosuppressant after solid organ transplantation might not be evident immediately in the postoperative period and might result in serious cardiopulmonary compromise.

Living related liver transplantation in infants and children: report of anesthetic care and early postoperative morbidity and mortality.

STUDY OBJECTIVE: To determine those infants at high risk for perioperative complications and mortality following living, related liver transplantation. DESIGN: Retrospective chart review. SETTING: Large metropolitan teaching hospital. MEASUREMENTS AND MAIN RESULTS: The charts and anesthetic records of the 12 infants and children who received the left lateral hepatic segment from a living relative the past 2 years at our institution were reviewed. The records were examined to determine the causes of perioperative morbidity and to identify patients at high risk for serious complications and mortality. All infants and children (mean +/- SD age, 29+/-30 months; weight, 13.6 +/-6.8 kg) survived the operation (8.3+/-1.7 hours) without intraoperative complications. The average blood loss, including 500 mL of recipient blood used to flush the liver before reperfusion, was 1483 +/-873 mL (119+/-70 mL/kg). Three infants developed portal vein thrombosis, and one of these infants also had hepatic artery thrombosis. The risk of vessel thrombosis was significantly higher (3/3 vs. 0/9; p<0.0045) in infants less than 9 kg body weight, as was the risk of death (2/3 vs. 0/9; p<0.045). Both children who died had vascular thrombosis. Other serious complications were bleeding, 6; infection, 7; acute rejection, 3; and bile leak, 2. CONCLUSIONS: Infants and children can successfully undergo living, related liver transplantation. However, the risks of vascular complications and death are greater in infants less than 9 kg body weight.

Living liver donor surgery: report of initial anesthesia experience.

The charts and anesthetic records of 12 patients who donated the left lateral segment of their liver to a related infant or child to treat liver failure were retrospectively reviewed. Blood loss, need for transfusion, fluids administered, surgical length, and perioperative complications were investigated. The records also were examined to determine the hemodynamic stability of patients undergoing donor hepatectomy to assess their need for invasive monitoring. There were no episodes of hypotension or hemodynamic instability. The average operating time was 9.6 +/- 1.1 hours. The blood loss was 562 +/- 244 mL (range 300 to 1100 mL). Four patients received their own cell saver blood (200 mL, 220 mL, 300 mL, 475 mL), and one patient received 1 U (350 mL) of predonated autologous blood. The average hemoglobin decreased significantly (p = 0.001) from a preoperative value of 14.1 +/- 1.2 to 12.3 +/- 1.8 g/dL in the recovery room. All patients were extubated in the operating room or recovery room. Patients were discharged home in 6.9 +/- 1.3 days (range 5 to 9 days). Living-related liver resection can be performed with noninvasive monitoring and without the need for heterologous blood products.

Trained nurses can provide safe and effective sedation for MRI in pediatric patients.

PURPOSE: To determine the success rate, safety and complications using a standard protocol and trained nurses to provide sedation for MRI under the supervision of a radiologist. MATERIALS AND METHODS: Nurses were trained to provide sedation via a standard protocol for pediatric patients undergoing diagnostic MRI. Oral chloral hydrate (80-100 mg x kg(-1)) was used for children less than 18 mo of age. Older children received either 1-6 mg x kg(-1) pentobarbital i.v., with or without 1-2 microg x kg x hr(-1) fentanyl, or 25 mg x kg(-1) thiopental pr. Sedation was defined as successful if it allowed completion of the MRI without image distorting patient movement. The records of 572 MRIs performed on 488 pediatric patients (mean age 5+/-4 yr; age 2 mo-14 yr) from 1991 to July 1995 were reviewed to determine the success rate and complications using the sedation program. RESULTS: Most, 91.8% (525/572), of the MRIs were successfully completed in 445 patients. The reasons for failure were inadequate sedation (45, 95.7%) and coughing (2, 4.2%). The failure rate was much higher before 1994 (38/272, 14%) than after (9/300, 3%; P<0.0001). Failure was more common if rectal thiopental was used (23/172, 14%) than intravenous pentobarbital (19/256, 7.4%; P<0.05). The failure rate was also high in patients with a history of a behavioural disorder (10/59, 17%). There were no deaths or unexpected admissions as a result of the sedation program. CONCLUSION: A high success rate can be achieved as experience is gained using a standard protocol and trained nurses to sedate children for MRI.

Perioperative anesthetic management of the kidney-pancreas transplant recipient.

Patients undergoing simultaneous pancreas-kidney transplantation are at risk for a variety of serious perioperative complications. These are related to the chronic and acute problems associated with end-stage renal disease and insulin-dependent diabetes mellitus and the prolonged, vascular and ductal surgery required to implant the two allografts. A number of strategies need to be integrated and diligently implemented to minimize the physiologic perturbations and complications related to the recipient's comorbid conditions and revascularization of the allografts. A major objective of the perioperative anesthetic management of simultaneous pancreas-kidney transplantation is to maximize cardiovascular performance in a way that provides optimum graft perfusion and recovery, while avoiding myocardial ischemia. Adherence to this objective, along with very effective immunosuppressants, surgical refinements, meticulous anesthetic preparation, extensive and frequent physiologic and metabolic monitoring, and quick response to abnormal findings has resulted in remarkably low recipient morbidity and mortality, and very high graft survival rates.

Hemodynamic and metabolic manifestations of acute endotoxin infusion in pigs with and without the malignant hyperthermia mutation.

BACKGROUND: The hypermetabolic state induced by acute endotoxemia and malignant hyperthermia (MH) may be indistinguishable. The aims of this study were (1) to investigate the differences between MH and sepsis, (2) to determine whether acute endotoxemia can trigger MH, and (3) to establish the effects of dantrolene in these two disorders. METHODS: Three groups of swine were studied. All pigs were invasively monitored and initially anesthetized with nontriggering agents. A placebo MH-susceptible group (n = 5) received normal saline whereas the endotoxin groups (MH-susceptible, n = 6; MH-negative, n = 4) received intravenous endotoxin (250 microg/kg total) during 2.5 h. Halothane (1.5%) and succinylcholine (2-4 mg/kg) were then administered, followed by two doses of dantrolene (4 mg/kg total). RESULTS: Endotoxin infusion resulted in pulmonary hypertension and systemic hypotension in pigs with and without the MH mutation, but did not trigger MH. Halothane and succinylcholine triggered MH, evidenced by a markedly higher oxygen consumption in the MH-susceptible pigs that received endotoxin (325+/-196 ml/min) and those that did not (374+/-110 ml/min) compared to the MH-negative pigs (69+/-15 ml/min, P<0.0009), as well as muscular rigidity in the susceptible animals. Dantrolene reversed these changes. Three of the six MH-susceptible pigs that received endotoxin died; two died soon after triggering and one after dantrolene administration. In contrast, none of the MH-negative pigs or the MH-susceptible pigs that did not receive endotoxin died (0 of 9 vs. 3 of 6, P = 0.044). CONCLUSION: Endotoxemia does not trigger MH, but may worsen outcome if it occurs.

Carbon dioxide embolism during laparoscopy: effect of insufflation pressure in pigs.

Carbon dioxide embolism is a rare but potentially devastating complication of laparoscopy. To determine the effects of insufflation pressure on the mortality from carbon dioxide embolism, six swine had intravascular insufflation with carbon dioxide for 30 seconds using a Karl Storz insufflator at a flow rate of 35 mL/kg/min. The initial insufflation pressure was 15 mm Hg. Following recovery from the first embolism, intravascular insufflation using a pressure of 20 mm Hg at the same flow rate was performed in the surviving animals. Significantly less carbon dioxide (8.3 +/- 2.7 versus 16.7 +/- 3.9 mL/kg; p < 0.02) was insufflated intravascularly at 15 mm Hg than at 20 mm Hg pressure. All of the pigs insufflated at 15 mm Hg pressure with a flow rate of 35 mL/kg/min survived. In contrast, 4 of the 5 pigs insufflated at 20 mm Hg pressure died. The surviving pig died when insufflated with 25 mm Hg pressure following an embolism of 15.7 mL/kg. Intravascular injection was often associated with an initial rise in end-tidal carbon dioxide tension, followed by a rapid fall in all cases where the embolism proved fatal. Insufflation should be begun with a low pressure and a slow flow rate to limit the volume of gas embolized in the event of inadvertent venous cannulation. Insufflation should immediately be stopped if a sudden change in end-tidal carbon dioxide tension occurs.

Accuracy of radial artery blood pressure determination with the Vasotrac.

PURPOSE: To evaluate the accuracy of a new non-invasive method (Vasotrac) to measure blood pressure (BP) with accompanying arterial wave-form and pulse-rate display when compared with BP and waveform measured invasively. METHODS: Healthy volunteers (n=53) served as subjects for the study. Blood pressures and waveforms obtained via a radial artery catheter (IABP) were compared with non-invasive measurements obtained every 12-15 beats by the new system (Vasotrac BP) from the opposite radial artery. In a sub-group of volunteers (n=11), BP was acutely increased and decreased with isoproterenol, phenylephrine and sodium nitroprusside. Data were analyzed by determining correlation and agreement between the two systems of measurement. Waveforms obtained by the two systems were qualitatively examined. RESULTS: Non-invasive BP measured every 12-15 beats by the Vasotrac correlated with IABP (systolic r2 = 0.89; diastolic r2 = 0.88; mean r2 = 0.94). The actual values obtained by the two methods agreed closely with > 90% of readings being within 2SDs when plotted by the Bland Altman method. This was also true during vasoactive drug infusion when BP changed acutely and swiftly. During this dynamic period, Vasotrac BP accurately tracked the changes in IABP with correlations (systolic r2 = 0.82; diastolic r2 = 0.89; mean r2 = 0.95) and close agreement (> 90% of readings were within 2 SDs in the Bland Altman plot). Waveforms displayed by the two systems were qualitatively very similar. Pulse rates measured by the two systems were identical. CONCLUSIONS: The Vasotrac system displayed an arterial waveform which was similar to that obtained directly and measured BP and pulse rate accurately. It should be a convenient device to measure BP continually in a non-invasive fashion.

Differential diagnosis of thyroid crisis and malignant hyperthermia in an anesthetized porcine model.

The intra-operative differential diagnosis between thyroid crisis and malignant hyperthermia can be difficult. Also stress alone can trigger MH. The purposes of this study were: 1) to investigate the metabolic and hemodynamic differences between thyroid crisis and MH, 2) determine how thyroid crisis affects the development of MH, and 3) determine if the stress of thyroid crisis can trigger MH in susceptible individuals. We studied MH susceptible and normal swine. Two groups of animals (MH susceptible and normal) were induced into thyroid crisis (critical core hyperthermia, sustained tachycardia and increase in oxygen consumption) by pretreatment with intraperitoneal triiodothyronine (T3) followed by large hourly intravenous injections of T3. Two similar groups were given intravenous T3 but no pretreatment. These animals did not develop thyroid crisis and served as controls. Thyroid crisis did not result in metabolic changes or rigidity characteristic of an acute episode of MH. When the animals were subsequently challenged with MH triggering agents (halothane plus succinylcholine) dramatic manifestations of fulminant MH episodes (acute serious elevation in exhaled carbon dioxide, arterial CO2, rigidity and acidemia) were noted only in the MH susceptible animals. Although thyroid crisis did not trigger MH in the susceptible animals it did decrease the time to trigger MH (14.1 +/- 7.2 minutes versus 47.2 +/- 17.7 minutes, p < 0.01) in susceptible animals. Hormone induced elevations in temperature and possibly other unidentified factors during thyroid crisis may facilitate the triggering of MH following halothane and succinylcholine challenge.

Total pancreatectomy with islet cell autotransplantation: anesthetic implications.

STUDY OBJECTIVE: To make recommendations for the perioperative management of patients undergoing total pancreatectomy with islet cell autotransplantation. DESIGN: Retrospective review. SETTING: University hospital. PATIENTS: 41 patients undergoing total pancreatectomy with autologous islet cell transplantation for chronic pancreatitis from 1977 to 1996. INTERVENTIONS: The charts and anesthetic records were reviewed, specifically investigating the changes in portal venous pressure, blood pressure (BP), and central venous pressure with islet cell injection. The records also were examined for blood glucose levels, type of fluids administered, blood loss, and postoperative complications. MEASUREMENTS AND MAIN RESULTS: Injection of islet cells into the portal vein caused a significant increase in portal venous pressures (8.5 +/- 4.8 to 27 +/- 16 cm/H2O; p < 0.001), which remained elevated at the end of injection (23 +/- 12 cm/H2O; p < 0.001). Central venous pressures also increased a small amount (9.3 +/- 4.3 to 10.6 +/- 5.8 mmHg; p < 0.05). In contrast, systolic blood pressures (SBPs) fell with administration of the islet cells (110 +/- 15 to 103 +/- 17 mmHg; p < 0.01), but SBP recovered in most patients at the end of injection (106 +/- 16 mmHg; p = NS). However, 6 patients (14.6%) required vasopressors to maintain adequate BPs. Blood glucose levels were significantly higher immediately prior to islet cell infusion in patients who had received dextrose-containing solutions than those who did not (246 +/- 80 vs. 176 +/- 43 gm/dl; p = 0.002). Median blood loss was 2000 ml (range 350 to 12,000 ml), and most patients (95.1%) required blood transfusions. CONCLUSION: Although total pancreatectomy with islet cell autotransplantation is a difficult operation, with significant blood loss, most patients tolerate surgery and injection of islet cells into their portal system without hemodynamic instability. Glucose-containing solutions should not be administered to patients prior to islet cell infusion because hyperglycemia, which can damage islet cells, may result.

Double volume exchange transfusion for ABO incompatible liver transplantation in paediatric patients: intraoperative and preoperative approach.

Double volume blood exchange transfusions (DBVET) were used to reduce the serum antibody levels in six paediatric patients receiving ABO incompatible hepatic allografts. In four patients, the exchange transfusions took place on the ward prior to surgery. In three of these four patients who had titres measured, the anti-A IgM titres fell from 1024 to 64, 64 to 8, and 128 to 16, respectively. The anti-A IgG titres fell from 32 to 16 and 512 to 64 in two patients, but rose from 16 to 32 in the third. In two patients DBVET were performed intraoperatively using a rapid infusion device. The IgM titres fell from 256 to 32 and 64 to 1, respectively, and the IgG titres fell from 16 to 4 and 2 to 0. Intraoperative DBVET can acutely and effectively reduce blood group antibodies. Intraoperative DBVET may reduce graft ischaemia time and allow red blood cell salvage.

Combined liver-total bowel transplantation has no immunologic advantage over total bowel transplantation alone. A prospective study in a porcine model.

BACKGROUND: Rejection remains a major obstacle to successful bowel transplantation in humans. It has been suggested that a simultaneous liver transplant would shield the bowel graft from immunologic attack, but the liver shortage would be aggravated. In a preclinical model, we studied the influence of simultaneous liver grafting by comparing the incidence of early bowel rejection after combined liver-total (small- and large-) bowel transplants vs total bowel transplants alone. METHODS: We assessed the incidence of early post-transplant rejection, graft-vs-host disease, and infection after combined liver-total bowel transplants (group 1, n = 10) and total bowel transplants alone (group 2, n = 9) in outbred Yorkshire Landrace pigs. Liver and bowel grafts were transplanted orthotopically with portal vein drainage after recipient hepatectomy (group 1) and total enterectomy (groups 1 and 2). Posttransplant immunosuppression was performed with intravenous tacrolimus (whole blood levels, 15 to 30 ng/mL) and prednisolone. In groups 1 and 2, bowel biopsy specimens from the ileostomy were obtained daily. In group 1, liver biopsy specimens were obtained weekly. Rejection was graded according to a 4-point scoring system (none, mild, moderate, and severe). RESULTS: Overall graft survival at days 7, 14, and 21 was 89%, 44%, and 11%, respectively, in group 1 vs 100%, 100%, and 86%, respectively, in group 2 (P < .001). Death rates owing to (irreversible) rejection at days 7, 14, and 21 were 0% in groups 1 and 2 (P = .48). Grading of bowel rejection episodes, based on the results of daily biopsy specimens, was not significantly different between the groups whether on individual days or overall. In group 1, the incidence of liver rejection episodes was as high as 66% (day 14 and at autopsy). At autopsy, generalized graft-vs-host disease (skin, native intestine, and native liver) was noted in 55% of group 1 and 43% of group 2 pigs (P = .55). Graft-vs-host disease was noted concurrently with rejection episodes of the liver or bowel grafts. CONCLUSIONS: Simultaneous liver grafting did not further reduce the incidence of early bowel rejection or graft-vs-host disease when compared with total bowel transplants alone. Based on the results of this preclinical study, simultaneous liver grafting is not indicated for patients with short-bowel syndrome and normal liver function.

Thermal response in acute porcine malignant hyperthermia.

This study was designed to evaluate how vital organ and skin-surface temperatures correlate with other clinical signs of a malignant hyperthermia (MH) episode. Six susceptible swine were anesthetized with thiopental and nitrous oxide and kept normothermic (approximately equal to 38 degrees C). After a 30-min control period, halothane (1 minimum alveolar anesthetic concentration) was administered, followed in 5 min by a bolus of succinylcholine (2 mg/kg intravenously). Monitoring included: 1) ETCO2; 2)PaO2, PaCO2, pHa; 3) cardiovascular function; 4) core temperatures (esophagus, pulmonary artery, and rectum); 5) organ temperatures (brain, kidney, liver, and four skeletal muscles); and 6) skin temperatures (forehead, neck, and axilla). Within 10 min after exposure to halothane and succinylcholine, all animals developed fulminant MH. Kidney, liver, and brain temperatures increased more rapidly than pulmonary artery temperature with the onset of MH. Temperatures significantly increased in the visceral organs prior to the detection of contractures within skeletal muscles. The masseter, longissimus dorsi, quadriceps, deltoid, and extensor digiti II intramuscular temperatures were 1-2 degrees C less than pulmonary artery and esophageal temperatures during the episodes, whereas those of the kidney, liver, and brain were the same or slightly greater. When it occurs, core hyperthermia during acute MH results largely from heat produced in central organs, not in skeletal muscle per se. In these swine, changes in axilla skin surface temperatures correlated well with core temperature trends, whereas those of the neck and forehead did not. Unless a skin-surface probe can be placed in close proximity to a major vessel, cutaneous temperatures should not be substituted for measurements at an appropriate core site.

Prior hypothermia attenuates malignant hyperthermia in susceptible swine.

This study was designed to determine the extent by which mild or moderate hyperthermia attenuates the triggering of malignant hypothermia (MH) induced by the combined administration of halothane and succinylcholine. Sixteen susceptible swine were initially anesthetized with nontriggering drugs and then either kept normothermic (approximately equal to 38 degrees C, n = 6) or cooled to induce mild (approximately equal to 35 degrees C, n = 6), or moderate (approximately equal to 33 degrees C, n = 4) hypothermia. Next, after a 30-min control period, the normothermic and mildly hypothermic animals were administered 1 minimum alveolar anesthetic concentration (MAC) halothane followed by a bolus dose of succinylcholine (2 mg/kg). Within 10 min all normothermic animals developed fulminant MH, whereas the onset of MH was slowed or was absent in the mildly hypothermic group. To test whether moderate hypothermia could more effectively minimize the signs of a MH episode, this group of animals was exposed to 1.5 MAC halothane followed 10 min later by a 3-mg/kg bolus of succinylcholine. MH was not induced and anesthesia was then changed to nontriggering drugs (ketamine and pancuronium). The animals were then aggressively rewarmed to 38 degrees C: a slight increase in the ETCO2 was detected, but MH episodes did not spontaneously occur. Subsequently, the readministration of halothane and succinylcholine rapidly provoked fulminant MH. We concluded that the induction of mild hypothermia impairs triggering and reduces the progression of MH induced by the combined administration of halothane and succinylcholine, whereas moderate hypothermia was completely protective and thus could be considered for prophylaxis.