A novel thermoregulatory system maintains perioperative normothermia in children undergoing elective surgery.

BACKGROUND: Body heat loss during anaesthesia may result in increased morbidity, particularly in high-risk populations such as children. To avoid hypothermia, a novel thermoregulatory system (Allon) was devised. We tested the safety and efficacy of this system in maintaining normothermia in children undergoing routine surgical procedures. METHODS: The system consists of a computerized body, which receives continuous afferent data, i.e. core (rectal) temperature. These data are then compared with a preset temperature (37 degrees C) and a microprocessor heating/cooling unit warms/cools the temperature of circulating water in a garment that is specially designed to allow maximal coverage of body surface area, without impingement on the surgical field. Water temperature to the garment was limited to a maximum of 39.5 degrees C. Continuous perioperative monitoring of skin and rectal temperature, heart rate and blood pressure was performed. Postoperative shivering and adverse effects were also assessed. RESULTS: The Allon system was used in 38 patients aged 3 months to 14 years undergoing surgery under general anaesthesia lasting more than 30 min. Fifty to 80% body surface area was covered by the garment. Mean operative and postoperative core temperatures were 36.9 +/- 0.5 degrees C and 36.7 +/- 0.5 degrees C, respectively. Intraoperative skin temperatures were maintained at 34.4 +/- 2.7 degrees C. The average core- to-periphery intraoperative gradient was 2.9 +/- 4.9 degrees C. Postoperative shivering was absent in 36 cases and mild in two cases. No device-related adverse effects were observed. CONCLUSIONS: Perioperative thermoregulation using the Allon system is safe and effective in maintaining body temperature within a narrow range in children undergoing brief surgical procedures.

The effect of helium on ventilator performance: study of five ventilators and a bedside Pitot tube spirometer.

OBJECTIVE: To assess in vitro the performance of five mechanical ventilators-Siemens 300 and 900C (Siemens-Elma; Solna, Sweden), Puritan Bennett 7200 (Nellcor Puritan Bennett; Pleasanton, CA), Evita 4 (Dragerwerk; Lubeck, Germany), and Bear 1000 (Bear Medical Systems; Riverside CA)-and a bedside sidestream spirometer (Datex CS3 Respiratory Module; Datex-Ohmeda; Helsinki, Finland) during ventilation with helium-oxygen mixtures. DESIGN: In vitro study. SETTING: ICUs of two university-affiliated hospitals. METHODS AND MEASUREMENTS: Each ventilator was connected to 100% helium through compressed air inlets and then tested at three to six different tidal volume (VT) settings using various helium-oxygen concentrations (fraction of inspired oxygen [FIO(2)] of 0.2 to 1.0). FIO(2) and VT were measured with the Datex CS3 spirometer, and VT was validated with a water-displacement spirometer. MAIN RESULTS: The Puritan Bennett 7200 ventilator did not function with helium. With the other four ventilators, delivered FIO(2) was lower than the set FIO(2). For the Siemens 300 and 900C ventilators, this difference could be explained by the lack of 21% oxygen when helium was connected to the air supply port, while for the other two ventilators, a nonlinear relation was found. The VT of the Siemens 300 ventilator was independent of helium concentration, while for the other three ventilators, delivered VT was greater than the set VT and was dependent on helium concentration. During ventilation with 80% helium and 20% oxygen, VT increased to 125% of set VT for the Siemens 900C ventilator, and more than doubled for the Evita 4 and Bear 1000 ventilators. Under the same conditions, the Datex CS3 spirometer underestimated the delivered VT by about 33%. CONCLUSIONS: At present, no mechanical ventilator is calibrated for use with helium. This investigation offers correction factors for four ventilators for ventilation with helium.

High rate of candidemia in patients sustaining injuries in a bomb blast at a marketplace: a possible environmental source.

In this study, a cluster of candidemia among patients sustaining injuries in a bomb blast at a marketplace was investigated by means of a multivariate analysis, a case-control study, and quantitative air sampling. Candidemia occurred in 7 (30%) of 21 patients (58% of those admitted to the intensive care unit [ICU]) between 4 and 16 days (mean, 12 days) after the injury and was the single most frequent cause of bloodstream infections. Inhalation injury was the strongest predictor for candidemia by multivariate analysis. Candidemia among the case patients occurred at a significantly higher rate than among comparable trauma patients injured in different urban settings, including a pedestrian mall (2 of 29; P=. 02), and among contemporary ICU control patients (1 of 40; P=.001). Air sampling revealed exclusive detection of Candida species and increased mold concentration in the market in comparison with the mall environment. These findings suggest a role for an exogenous, environmental source in the development of candidemia in some trauma patients.

Postcardiopulmonary bypass hypoxemia: a prospective study on incidence, risk factors, and clinical significance.

OBJECTIVE: To evaluate the clinical significance of low arterial oxygen tension-inspired oxygen concentration (PaO2-FIO2) ratio, as a measure of hypoxemia, in the early period after cardiac surgery with cardiopulmonary bypass (CPB); and to evaluate the preoperative, intraoperative, and postoperative factors contributing to the development of hypoxemia within the first 24 hours after cardiac surgery with CPB. DESIGN: Prospective observational study. SETTING: University hospital. PARTICIPANTS: Patients who underwent elective or emergency cardiac surgery with CPB (n = 466). INTERVENTIONS: Preoperative clinical and laboratory data were recorded, as were intraoperative and postoperative data regarding the PaO2-FIO2 ratio, fluid and drug therapy, and chest radiograph. Data analysis evaluated hypoxemia as depicted by the PaO2-FIO2 ratios at 1, 6, and 12 hours after surgery. Thereafter, the effect of the PaO2-FIO2 ratios on time to extubation, lung injury, and length of hospital stay was evaluated. The risk factors were analyzed in 3 separate periods: preoperative, intraoperative, and postoperative. Univariate and multivariate analyses were performed on each period separately. All data were analyzed in 2 consecutive steps: univariate analysis and multivariate analysis. MEASUREMENTS AND MAIN RESULTS: PaO2-FIO2 ratios after CPB were significantly lower compared with baseline values. Six patients (1.32%) met the clinical criteria compatible with acute lung injury. All 6 patients had prompt recovery. Significant risk factors for hypoxemia were age, obesity, reduced cardiac function, previous myocardial infarction, emergency surgery, baseline chest radiograph with alveolar edema, high creatinine level, prolonged CPB time, decreased baseline PaO2-FIO2, use of dopamine after discontinuation of CPB, coronary artery bypass grafting, use of left internal mammary artery, higher pump flow requirement during CPB, increased level of hemoglobin or total protein content, persistent hypothermia 2 and 6 hours after surgery, requirement for reexploration, event requiring reintubation, and chest radiograph with alveolar edema 1 hour after surgery. Six hours after surgery, a lower PaO2-FIO2 ratio correlated significantly with time to extubation and lung injury. CONCLUSIONS: This study shows that despite improvements in the technique of CPB, hypoxemia depicted by low PaO2-FIO2 ratios is common in patients after CPB. It is short lived, however, and has minimal effect on the postoperative clinical course of these patients.

High oxygen concentration exacerbates cardiopulmonary bypass-induced lung injury.

OBJECTIVE: To investigate the effect of ventilation with 100% oxygen on lung injury associated with surgery involving cardiopulmonary bypass (CPB). DESIGN: A prospective randomized study. SETTING: University hospital. PARTICIPANTS: Thirty patients undergoing coronary artery bypass graft surgery with CPB. INTERVENTIONS: Patients were randomized to receive 100% oxygen (Oxygen group) or 50% oxygen (Air group) throughout surgery. During CPB, patients' lungs in the Air group were flushed with air and in the Oxygen group with 100% oxygen. MEASUREMENTS AND MAIN RESULTS: Lung injury was evaluated by arterial oxygen tension-inspired oxygen concentration (PaO2-FIO2) ratio and cytokine levels (tumor necrosis factor-alpha and interleukin-8) in blood and bronchoalveolar lavage fluid measured before and after CPB. The lowest PaO2-FIO2 value was observed after 40 minutes following the completion of CPB in both groups. PaO2-FIO2 values 6 hours after CPB were not different from baseline in the Air group but remained lower (359+/-63 mmHg and 298+/-78 mmHg; p = 0.013) in the Oxygen group. Blood cytokine levels rose during surgery in both groups. Bronchoalveolar lavage levels of interleukin-8 did not change, whereas tumor necrosis factor-alpha increased only in the Oxygen group (p = 0.035). CONCLUSIONS: A significant decrease of oxygenation was observed in the early post-CPB period in both groups of patients, with delay in recovery in patients treated with 100% oxygen. A larger increase of the proinflammatory cytokines was found in patients treated with 100% oxygen. High oxygen concentrations during surgery with CPB should be used only when specifically required.

Recovery from blast lung injury: one-year follow-up.

BACKGROUND: Blast injury to the lung is one of the devastating threats facing victims of an explosion. Although the pathogenesis of blast injury has been studied, little is known about the long-term effects on lung function in survivors. OBJECTIVE: To examine the pulmonary function of survivors 1 year after sustaining a blast injury. DESIGN: Prospective study. SETTING: Pulmonary function test laboratory at Hadassah Medical Center, Jerusalem. PARTICIPANTS: Eleven surviving victims of a blast injury sustained during a bus terrorist explosion. MEASUREMENTS: Twelve months after the injury, physical examinations, lung function tests, and progressive cardiopulmonary exercise examinations were conducted, and chest radiographs were obtained. RESULTS: The average age was 28 +/- 9.8 years. Most of the victims had multiple injuries in addition to the lung injury. Ten patients received mechanical ventilation, and 6 patients required chest drainage. All patients were treated in the ICU, with an average stay of 11.8 +/- 9 days. The patients were discharged to their homes or to a rehabilitation center 32.4 +/- 27. 3 days after the explosion. One year later, none had any pulmonary-related complaints. Physical examination of the lungs was normal. Most of the patients demonstrated normal lung function tests and complete resolution of the chest radiograph findings. CONCLUSION: Most patients who survive lung blast injury will regain good lung function within a year.

Systolic pressure variation in hemodynamic monitoring after severe blast injury.

Fluid management in patients following blast injury is a major challenge. Fluid overload can exacerbate pulmonary dysfunction, whereas suboptimal resuscitation may exacerbate tissue damage. In three patients, we compared three methods of assessing volume status: central venous (CVP) and pulmonary artery occlusion (PAOP) pressures, left ventricular end-diastolic area (LVEDA) as measured by transesophageal echocardiography, and systolic pressure variation (SPV) of arterial blood pressure. All three patients were mechanically ventilated with high airway pressures (positive end-expiratory pressure 13 to 15 cm H2O, pressure control ventilation of 25 to 34 cm H2O, and I:E 2:1). Central venous pressure and PAOP were elevated in two of the patients (CVP 14 and 18 mmHg, PAOP 25 and 17 mmHg), and were within normal limits in the third (CVP 5 mmHg, PAOP 6 mmHg). Transesophageal echocardiography was performed in two patients and suggested a diagnosis of hypovolemia (LVEDA 2.3 and 2.7 cm2, shortening fraction 52% and 40%). Systolic pressure variation was elevated in all three patients (15 mmHg, 15 mmHg, and 20 mmHg), with very prominent dDown (23, 40, and 30 mmHg) and negative dUp components, thus corroborating the diagnosis of hypovolemia. Thus, in patients who are mechanically ventilated with high airway pressures, SPV may be a helpful tool in the diagnosis of hypovolemia.

Spontaneous intracerebral hemorrhage in critically ill patients: incidence over six years and associated factors.

OBJECTIVE: Intracerebral hemorrhage (ICH) is associated with a high mortality. The present study sought to determine the incidence of spontaneous ICH in an intensive care unit (ICU) and associated factors. DESIGN: A 6 year retrospective study. SETTING: A general ICU in a university hospital. PATIENTS: All ICU patients developing ICH were included in the study. All trauma and neurosurgical patients were excluded, as well as patients who were admitted to the ICU because of ICH. MEASUREMENTS AND RESULTS: During the study period 3032 patients were hospitalized in the ICU, and 834 were excluded. The remaining 2198 patients comprised the study population. Computed tomography of the head was performed in a total of 227 patients, and the 9 patients found to have new onset ICH comprise the group of interest. None of these patients were hypertensive. Seven of the patients had either a primary hematologic malignancy or bone marrow transplantation. Eight had thrombocytopenia of <100x10(9)/l (median 10x10(9)/l, range 3-150x10(9)/l), and in 6 it preceded ICH by 5 days or more. Only in one patient were both PTT and PT prolonged. All were mechanically ventilated with high peak inspiratory pressure (PIP) (median 37 cm H2O, range 20-43 cm H2O). Arterial carbon dioxide tension (PaCO2) was considerably elevated (median 65 mm Hg, range 41-87 mm Hg). All of the patients had impaired renal and hepatic function (urea: median 14 mmol/l, range 9.9-52 mmol/l; bilirubin: median 94 micromol/l, range 20-360 micromol/l), and five had septicemia. Eight of the patients bled to other sites before they developed ICH. All patients died shortly after the diagnosis of ICH. CONCLUSIONS: Spontaneous nonhypertensive ICH is a rare, fatal event in the ICU. Associated factors include thrombocytopenia, the need for mechanical ventilation, elevated PIP and PaCO2, sepsis, and impaired hepatic and renal function.

Blast lung injury from an explosion on a civilian bus.

OBJECTIVE: To assess clinical signs and management of primary blast lung injury (BLI) from explosions in an enclosed space and to propose a BLI severity scoring system. DESIGN: Retrospective analysis. PATIENTS: Fifteen patients with primary BLI resulting from explosions on two civilian buses in 1996. RESULTS: Ten patients were extremely hypoxemic on admission (PaO2 < 65 mm Hg with oxygen supplementation). Four patients remained severely hypoxemic (PaO2/fraction of inspired oxygen (FIO2) ratio of < 60 mm Hg) after mechanical ventilation was established and pneumothoraces were drained. Initial chest radiographs revealed bilateral lung opacities of various sizes in 12 patients (80%). Seven patients (47%) had bilateral pneumothoraces and two patients had a unilateral pneumothorax. Five (33%) had clinically significant bronchopleural fistulae. After clinical and laboratory data were collected, a BLI severity score was defined based on hypoxemia (PaO2/FIO2 ratio), chest radiographic abnormalities, and barotrauma. Severe BLI was defined as a PaO2/FIO2 ratio of < 60 mm Hg, bilateral lung infiltrates, and bronchopleural fistula; moderate BLI as a PaO2/FIO2 ratio of 60 to 200 mm Hg and diffuse (bilateral/unilateral) lung infiltrates with or without pneumothorax; and mild BLI as a PaO2/FIO2 ratio of > 200, localized lung infiltrates, and no pneumothorax. Five patients developed ARDS with Murray scores > 2.5. Respiratory management included positive pressure ventilation in the majority of the patients and unconventional methods (ie, high-frequency jet ventilation, independent lung ventilation, nitric oxide, and extracorporeal membrane oxygenation) in patients with severe BLI. Of the four patients who had severe BLI, three died. All six patients with moderate BLI survived, and four of five with mild BLI survived (one with head injury died). CONCLUSIONS: BLI can cause severe hypoxemia, which can be improved significantly with aggressive treatment. The lung damage may be accurately estimated in the early hours after injury. The BLI severity score may be helpful in determining patient management and prediction of final outcome.