Lawrence J. Caruso

Inspiratory muscle strength training improves weaning outcome in failure to wean patients: a randomized trial

IntroductionMost patients are readily liberated from mechanical ventilation (MV) support, however, 10% - 15% of patients experience failure to wean (FTW). FTW patients account for approximately 40% of all MV days and have significantly worse clinical outcomes. MV induced inspiratory muscle weakness has been implicated as a contributor to FTW and recent work has documented inspiratory muscle weakness in humans supported with MV.MethodsWe conducted a single center, single-blind, randomized controlled trial to test whether inspiratory muscle strength training (IMST) would improve weaning outcome in FTW patients. Of 129 patients evaluated for participation, 69 were enrolled and studied. 35 subjects were randomly assigned to the IMST condition and 34 to the SHAM treatment. IMST was performed with a threshold inspiratory device, set at the highest pressure tolerated and progressed daily. SHAM training provided a constant, low inspiratory pressure load. Subjects completed 4 sets of 6-10 training breaths, 5 days per week. Subjects also performed progressively longer breathing trials daily per protocol. The weaning criterion was 72 consecutive hours without MV support. Subjects were blinded to group assignment, and were treated until weaned or 28 days.ResultsGroups were comparable on demographic and clinical variables at baseline. The IMST and SHAM groups respectively received 41.9 ± 25.5 vs. 47.3 ± 33.0 days of MV support prior to starting intervention, P = 0.36. The IMST and SHAM groups participated in 9.7 ± 4.0 and 11.0 ± 4.8 training sessions, respectively, P = 0.09. The SHAM groups pre to post-training maximal inspiratory pressure (MIP) change was not significant (-43.5 ± 17.8 vs. -45.1 ± 19.5 cm H2O, P = 0.39), while the IMST groups MIP increased (-44.4 ± 18.4 vs. -54.1 ± 17.8 cm H2O, P < 0.0001). There were no adverse events observed during IMST or SHAM treatments. Twenty-five of 35 IMST subjects weaned (71%, 95% confidence interval (CI) = 55% to 84%), while 16 of 34 (47%, 95% CI = 31% to 63%) SHAM subjects weaned, P = .039. The number of patients needed to be treated for effect was 4 (95% CI = 2 to 80).ConclusionsAn IMST program can lead to increased MIP and improved weaning outcome in FTW patients compared to SHAM treatment.Trial RegistrationClinicalTrials.gov: NCT00419458

A better landmark for positioning a central venous catheter.

Background.Improper positioning of central venous catheters (CVCs) can lead to erosion through the superior vena cava (SVC) or right atrium (RA) and pericardial tamponade. It is widely recommended that the tip of CVCs be placed above the heart or the pericardial reflection. The purpose of this study was to identify an easily recognized landmark to allow identification of the proximal extent of the pericardial reflection on a routine chest radiograph (CXR). Methods.We analyzed the computerized tomograms of the chest from 97 adults to evaluate the relationship between the pericardial reflection, SVC, carina, and right mainstem bronchus. Correlations between demographic data and length of SVC or pericardial reflection were sought. Results.The mean length of the SVC was 6.5 cm. The pericardial reflection covered an average of 3.6 cm of the distal SVC. The carina was a mean of 1.3 cm below the mid-point of the SVC and 0.7 cm below the pericardial reflection. There was no significant correlation between SVC or pericardial length and either age, height, or weight. Conclusions.The distal half of the SVC lies within the pericardial reflection, and the upper limit of the pericardial reflection is slightly above the level of the carina. These landmarks are useful for determining proper position of the tip of a CVC on CXR.

Oxidant injury occurs rapidly after cardiac arrest, cardiopulmonary resuscitation, and reperfusion.

Objective:Investigations conducted in cellular models show that reperfusion of ischemic tissue is associated with a burst of reactive oxidant species within minutes after reperfusion. Oxidant injury may play a role in the poor outcome typical of people resuscitated from cardiac arrest. The objective of the present study was to determine the presence and timing of oxidant injury in an in vivo model of cardiac arrest. Design:Randomized controlled. Setting:University medical center laboratory. Subjects:Domestic swine. Interventions:We evaluated oxidant injury during and after 8 mins of cardiac arrest using a gas chromatography/mass spectrometry F2-isoprostane assay and compared these results with a matched control group. Measurements and Main Results:Baseline mean arterial, venous, and brain tissue F2-isoprostane levels were not significantly different when the cardiac arrest group was compared with the control group. However, in the group subjected to cardiac arrest and cardiopulmonary resuscitation we found significant (p < .0006) two- to three-fold increases in venous and arterial F2-isoprostane levels, which peaked between 15 and 30 mins after reperfusion and returned to baseline within 90 mins (p < .0006). Overall mean (± se) brain tissue F2-isoprostane levels increased significantly to 370 ± 60 vs. 140 ± 60 ng/g tissue in the cardiac arrest group compared with the control group (p = .026). Conclusion:This study shows that F2-isoprostane measurement could be used to assess oxidant injury in an animal model of cardiac arrest and that oxidant injury occurs rapidly after cardiac arrest and reperfusion.

Effects of elevating the head of bed on interface pressure in volunteers.

Objective:Intensive care unit patients are at particular risk for pressure ulcers and ventilator-associated pneumonia. Current guidelines recommend that mechanically ventilated patients be kept in a semirecumbent position with the head of bed elevated 30°–45° to prevent aspiration and ventilator-associated pneumonia. We tested the effects of elevating the head of bed on the interface pressure between the skin of the sacral area and the bed with healthy volunteers. Interventions:Interface pressure profiles of the sacral area were obtained for the 0°, 10°, 20°, 30°, 45°, 60°, and 75° head of bed elevated positions from 15 subjects (14 men, one woman). Measurements and Main Results:Peak sacral interface pressures increased with large increases in head of bed elevation. The 30°, 45°, 60°, and 75° head of bed positions all had peak interface pressures that were significantly (p < 0.02) greater than the supine measurement and also were different from all other head of bed positions. Affected areas, defined as areas over which an interface pressure ≥32 mm Hg was obtained, increased with large elevation of the head of bed. The affected areas of the 45°, 60°, and 75° head of bed positions were significantly greater than the supine position and were also significantly different from all other head of bed positions. Conclusions:Raising the head of bed to 30° or higher on a intensive care unit bed increases the peak interface pressure between the skin at the sacral area and support surface in healthy volunteers. At 45° head of bed elevation or higher, the affected area attributed to a skin–intensive care unit bed interface pressure ≥32 mm Hg increased as well. Further study is needed to determine whether the increased peak interface pressures and affected areas that result from raising the head of bed actually increase the incidence of pressure ulcer formation.

Utilization of Intensive Care Resources in Bariatric Surgery

Background: Obese patients occasionally require either elective or emergency critical care services following bariatric surgery. We describe this subgroup of patients. Methods: From July 1, 1991 to July 31, 2004, we performed 1,279 bariatric operations; 241 (19%) required admission to the surgical critical care service. We retrospectively reviewed medical records for gender, body mass index (BMI), age, whether the operation was initial or revisional, and whether critical care admission was elective or emergent. 3 complication clusters (thromboembolic, pulmonary, and anastomotic) were identified using discharge ICD-9 codes. The costs and length of stay of these subpopulations was calculated. Results: Patients were on average 46 ± 10 years old, with BMI 59 ± 13. Critical care admission was emergent in 52.7% (n=127) of cases. Revisional cases did not differ from the initial cases in BMI (56.4 vs 59.2, P=0.42) and they were no more likely to require emergent critical care admission than initial cases (P=0.16). Revisional cases were hospitalized longer (27.2 ± 25.6 vs 12.5 ± 18.7 days, P =0.003); had higher total hospital costs (US

Patient repositioning and pressure ulcer risk—Monitoring interface pressures of at-risk patients

60,631 ± 78,337 vs 27,697 ± 52,351, P=0.025); and were more likely to die from their complications (revisional surgery mortality 6.5% vs 1.9% for initial surgery [P=0.002]). Conclusions: An increasing number of surgical revisions will likely accompany the recent increase in popularity of bariatric surgery. In our experience, these patients require significant critical care services, and have longer, complicated, and more costly hospitalizations.

Postoperative Acute Renal Failure Secondary to Rhabdomyolysis from Exaggerated Lithotomy Position

Repositioning patients regularly to prevent pressure ulcers and reduce interface pressures is the standard of care, yet prior work has found that standard repositioning does not relieve all areas of at-risk tissue in nondisabled subjects. To determine whether this holds true for high-risk patients, we assessed the effectiveness of routine repositioning in relieving at-risk tissue of the perisacral area using interface pressure mapping. Bedridden patients at risk for pressure ulcer formation (n = 23, Braden score <18) had their perisacral skin-bed interface pressures recorded every 30 s while they received routine repositioning care for 4-6 h. All participants had specific skin areas (206 +/- 182 cm(2)) that exceeded elevated pressure thresholds for >95% of the observation period. Thirteen participants were observed in three distinct positions (supine, turned left, turned right), and all had specific skin areas (166 +/- 184 cm(2)) that exceeded pressure thresholds for >95% of the observation period. At-risk patients have skin areas that are likely always at risk throughout their hospital stay despite repositioning. Healthcare providers are unaware of the actual tissue-relieving effectiveness (or lack thereof) of their repositioning interventions, which may partially explain why pressure ulcer mitigation strategies are not always successful. Relieving at-risk tissue is a necessary part of pressure ulcer prevention, but the repositioning practice itself needs improvement.

Myocardial ischemia detected by transesophageal echocardiography in a patient undergoing peripheral vascular surgery.

Perioperative renal dysfunction is a common problem following urogenital surgery. The most common causes of renal failure include ischemic or nephrotoxic acute tubular necrosis, renal vascular injury, and urinary tract obstruction. This case conference describes a patient who developed acute renal failure, secondary to rhabdomyolysis after a 7-hour urologic surgical procedure in an exaggerated lithotomy position. Early diagnosis and aggressive treatment are essential to prevent or limit the severity of acute renal failure. A review of the literature and pathophysiology of acute renal failure secondary to rhabdomyolysis is included.

Prolonged neuromuscular block in a patient undergoing renal transplantation

Prevention and early treatment of myocardial ischemia remain among the primary goals of the anesthesiologist taking care of high-risk patients, such as those undergoing vascular surgery. Guidelines have been published to assist in directing preoperative evaluation and optimization of cardiovascular status. Although perioperative monitoring allows early detection of ischemic events, all monitors have limitations that must be understood before they can be used effectively. We present a case of severe intraoperative myocardial dysfunction detected only by transesophageal echocardiography in a patient undergoing a peripheral vascular procedure. Preoperative and intraoperative management is also discussed.

Diltiazem to treat sinus tachycardia in critically ill patients: A four-year experience

Prolonged neuromuscular block is an anesthetic complication that every anesthesiologist should understand. This article presents a case of prolonged neuromuscular block in a renal transplant patient that was likely due to pseudocholinesterase deficiency. The different types of pseudocholinesterase deficiency and their clinical implications are reviewed. Also discussed are the workup and other causes for prolonged neuromuscular blockade.