Biomedical subjects
T G Monk
Publications and source records attributed to T G Monk.
Acute normovolemic hemodilution can replace preoperative autologous blood donation as a standard of care for autologous blood procurement in radical prostatectomy.
UNLABELLED: Predonation of autologous blood (PAD) is a standard of care for patients undergoing radical prostatectomy, but recent studies have shown that PAD is not cost-effective. Acute normovolemic hemodilution (ANH) is an alternative autologous blood procurement technique that is much less costly than PAD. We compared the efficacy and costs of ANH alone to ANH combined with PAD. Two hundred-fifty patients who predonated fewer than 3 units of autologous blood before radical prostatectomy underwent ANH to a target hematocrit of 28%. Perioperative hematocrit levels, transfusion outcomes and costs, and postoperative outcomes were compared for patients who predonated 0, 1, or 2 units of blood before surgery. A computer model was used to estimate the savings in red blood cells (RBC) associated with each autologous intervention. ANH alone resulted in a 21% allogeneic transfusion rate and contributed a mean net savings of 112 mL RBC in blood conservation (equivalent to 0.6 unit of blood). The addition of 1 or 2 units of PAD reduced allogeneic exposure rates to 6% or 0%, respectively. Overall, patients who predonated blood had a mean net loss of 198 mL of RBC (equivalent to 1 blood unit), due to both an absence in compensatory erythropoiesis and to the wastage of 60% of the blood units donated. Patients who underwent ANH alone had a 60% reduction in mean total transfusion costs ($103 +/- $102) compared with patients who predeposited 2 units of autologous blood in addition to ANH ($269 +/- $11, P < 0.05). We conclude that ANH can replace PAD as an autologous blood option because it is less costly and equally effective. A combination of ANH and PAD can further decrease allogeneic blood exposure, but it increases transfusion costs and wastage. IMPLICATIONS: A patient's own blood can be obtained for use in surgery by predonation or acute normovolemic hemodilution on the day of surgery. Both blood collection techniques decrease the need for blood bank transfusions, but acute normovolemic hemodilution is less expensive and more convenient for patients.
Laparoscopic pneumodissection: results in initial 20 patients.
BACKGROUND: The efficiency of laparoscopic procedures has been hindered by a lack of instrumentation for blunt tissue dissection. We evaluated here the efficacy of a new 5-mm laparoscopic dissecting instrument, a pneumodissector. This instrument allows the surgeon to use short bursts of high-pressure carbon dioxide to bluntly dissect fatty tissue. STUDY DESIGN: In 20 patients undergoing a variety of laparoscopic procedures, a 5-mm laparoscopic pneumodissector was used. Subjective assessment of the efficacy of the instrument was recorded. In addition, acid-base changes were measured by blood gas determination, and serum chemistries were obtained before, during, and after the procedure. RESULTS: The pneumodissector enhanced dissection of the kidney, ureter, and major blood vessels and shortened the operative time for laparoscopic nephrectomy. Although statistically significant changes in acidbase values occurred with use of the pneumodissector, these changes were not clinically significant and were no different than what is normally seen during carbon dioxide pneumoperitoneum. CONCLUSIONS: Laparoscopic pneumodissection is a safe and efficacious technique for rapid blunt tissue dissection.
Blood substitutes: evolution and future applications.
The development of oxygen-carrying blood substitutes has progressed significantly in the last decade with phase I and phase II clinical trials of both hemoglobin-based and perfluorocarbon-based oxygen carriers nearing completion. As these products approach clinical use it is important for the laboratory medicine community to be aware of their effects on routine laboratory testing and the settings in which they might be used. Here we review the forces driving the development of oxygen-carrying blood substitutes, the clinical settings in which they might be used, the major categories of oxygen carriers in clinical trials, and the challenges faced by these products as they approach clinical use.
Effect of hemoglobin- and Perflubron-based oxygen carriers on common clinical laboratory tests.
Polymerized hemoglobin solutions (Hb-based oxygen carriers; HBOCs) and a second-generation perfluorocarbon (PFC) emulsion (Perflubron) are in clinical trials as temporary oxygen carriers ("blood substitutes"). Plasma and serum samples from patients receiving HBOCs look markedly red, whereas those from patients receiving PFC appear to be lipemic. Because hemolysis and lipemia are well-known interferents in many assays, we examined the effects of these substances on clinical chemistry, immunoassay, therapeutic drug, and coagulation tests. HBOC concentrations up to 50 g/L caused essentially no interference for Na, K, Cl, urea, total CO2, P, uric acid, Mg, creatinine, and glucose values determined by the Hitachi 747 or Vitros 750 analyzers (or both) or for immunoassays of lidocaine, N-acetylprocainamide, procainamide, digoxin, phenytoin, quinidine, or theophylline performed on the Abbott AxSym or TDx. Gentamycin and vancomycin assays on the AxSym exhibited a significant positive and negative interference, respectively. Immunoassays for TSH on the Abbott IMx and for troponin I on the Dade Stratus were unaffected by HBOC at this concentration. Tests for total protein, albumin, LDH, AST, ALT, GGT, amylase, lipase, and cholesterol were significantly affected to various extents at different HBOC concentrations on the Hitachi 747 and Vitros 750. The CK-MB assay on the Stratus exhibited a negative interference at 5 g/L HBOC. HBOC interference in coagulation tests was method-dependent-fibrometer-based methods on the BBL Fibro System were free from interference, but optical-based methods on the MLA 1000C exhibited interferences at 20 g/L HBOC. A 1:20 dilution of the PFC-based oxygen carrier (600 g/L) caused no interference on any of these chemistry or immunoassay tests except for amylase and ammonia on the Vitros 750 and plasma iron on the Hitachi 747.
Evolving concepts in autologous blood procurement and transfusion: case reports of perisurgical anemia complicated by myocardial infarction.
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Intraoperative salvage in patients undergoing elective abdominal aortic aneurysm repair: an analysis of cost and benefit.
PURPOSE: Although autologous blood procurement has become a standard of care in elective surgery, recent studies have questioned its cost-effectiveness. We therefore reviewed our 3-year experience with intraoperative cell salvage in patients who underwent elective abdominal aortic aneurysm repair. METHODS: A 3-year retrospective chart review of elective abdominal aortic aneurysm (infrarenal and suprarenal) repair was performed. Transthoracic repairs were excluded. RESULTS: Estimated blood lost was 1748 +/- 1236 ml, or 35% of baseline blood volume (5012 +/- 689 ml). Overall, 164 (89%) received red blood cell (RBC) transfusions (3.5 +/- 2.0 U/patient). The cost per patient for cell salvage was $315 +/- $97, representing 31% of all RBC costs and 24% of total blood component costs. Mean salvage volume infused was 578 +/- 600 ml; at a mean hematocrit level of 55.7% the RBC volume infused from salvage during surgery was 313 +/- 328 ml (representing 27% of total RBC volume lost during the hospital stay). This mean RBC volume salvaged represented the equivalent of 1.6 blood bank RBC units. The mean blood bank costs saved by using cell salvage was $248, or 79% of the $315 actually spent for salvage. We found no decrease in percentage of patients undergoing transfusion until salvage volumes that were infused exceeded 750 ml, or the equivalent of two blood bank units; all of these patients who benefitted had estimated blood lost > or = 1000 ml. CONCLUSIONS: We conclude that use of intraoperative cell salvage was most beneficial for patients who had estimated blood loss greater than or equal to 1000 ml and cell salvage volumes infused greater than or equal to 750 ml. Patients who are estimated to lose less than 1000 ml receive little benefit yet incur substantial costs from intraoperative cell salvage.
Autologous blood procurement in the surgical setting: lessons learned in the last 10 years.
The percentage of blood transfused yearly that is autologous has increased substantially over the last 10 years. While autologous blood is regarded as a standard of care in many elective surgical settings, the increasing safety of allogeneic blood and the expense of autologous blood procurement have raised question regarding the appropriate roles of autologous blood in blood conservation strategies. We therefore review current activities and emerging questions that arise from this maturing arena.
The effect of prolonged pneumoperitoneum on renal function in an animal model.
BACKGROUND: Prolonged, increased intra-abdominal pressure (IAP) during laparoscopic surgery has been associated with oliguria and anuria. STUDY DESIGN: The objective of this study was to evaluate the effects of various levels of IAP on renal function. Ten groups of three adult female farm pigs were given a general anesthetic, followed by establishment of an IAP of 0, 5, 10, 15, or 20 mm Hg with CO2, 20 mm Hg with argon gas, abdominal wall lift device, renal vein occlusion (RVO), 15 mm Hg with CO2 plus dopamine administration at 2 microgram/kg/minute, or 20 mm Hg retroperitoneal CO2 insufflation. The following studies were recorded: baseline central venous pressure (CVP), pulmonary wedge pressure (PWP), cardiac output (CO), renal vein flow (RVF), renal artery pressure (RAP), selective urine output (UO), urinary osmolarity, and creatinine clearance; the parameters were repeated every 30 minutes for the four hours of the IAP study and two hours after release of the IAP. RESULTS: The results were analyzed within two main IAP groups: less than 15 mm Hg and greater than or equal to 15 mm Hg. There was no clinically significant variation in the CVP, PWP, and RAP. The CO decreased slightly and this was more significant in the greater than or equal to 15 mm Hg group. The RVF and UO decreased concomitantly and significantly in the greater than or equal to 15 mm Hg group. Even after two hours of desufflation, the RVF did not return to baseline, although the UO improved. Creatinine clearance decreased significantly in the greater than or equal to 15 mm Hg group. The RVO group exhibited similar changes in the study parameters as those seen in the greater than or equal to 15 mm Hg group, although the RVF did not improve on release of the renal vein in the RVO group. Changes were the same with an argon or CO2 IAP of 20 mm Hg. The abdominal wall lift device had an associated decrease in RVF at 15 KG force but no alteration in UO. Retroperitoneal insufflation resulted in the same decrease in RVF and UO as seen with the same IAP. Dopamine did not afford a protective effect on UO during an IAP of 15 mm Hg. CONCLUSIONS: The decreased UO during prolonged IAP greater than or equal to 15 mm Hg in the animal model is associated with a corresponding decrease in RVF, but does not appear to be associated with any permanent renal derangement nor any transient histologic changes.
Carbon dioxide and helium insufflation during laparoscopic radical nephrectomy in a patient with severe pulmonary disease.
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Blood conservation strategies to minimize allogeneic blood use in urologic surgery.
Analysis of the net costs, efficacy, and cost-effectiveness of preoperative autologous blood donation (PAD), versus acute normovolemic hemodilution (ANH), in patients undergoing radical prostatectomy is presented. Currently, PAD is a standard of care for patients undergoing radical prostatectomy. Comparison of PAD with ANH showed no differences in risks or outcome, but ANH was less expensive. Hemodilution is a simple, safe, convenient, and effective alternative to PAD. The use of recombinant human erthropoietin in conjunction with PAD and ANH has optimized perioperative hematocrits and further minimized exposure to allogeneic blood. Intraoperative blood salvage, lower transfusion triggers, and other blood conservation strategies are discussed. The most cost-effective techniques currently available for decreasing allogeneic blood transfusions appear to be avoidance of blood loss, increased tolerance for decreased HCT levels, and autologous blood procurement via ANH.
Laparoscopic pneumodissection: initial clinical experience.
OBJECTIVES: We evaluated the efficacy of a new laparoscopic dissecting instrument that fires intermittent bursts of high-pressure carbon dioxide to separate tissue along natural planes. METHODS: The pneumodissector (PD) was used in 2 patients undergoing laparoscopic procedures. Serum creatinine and bicarbonate were measured before and after the procedure, and arterial blood gases were measured before, during, and after use of the PD. Subjective assessment of the ease of dissection with the PD by the first assistant was recorded. RESULTS: Acidosis and hypercarbia were not observed with use of the PD. The PD facilitated dissection along the iliac vessels, around the kidney, and in the renal hilum. CONCLUSIONS: The PD is a feasible method for rapid, blunt dissection during laparoscopic procedures.
Acute normovolemic hemodilution is a cost-effective alternative to preoperative autologous blood donation by patients undergoing radical retropubic prostatectomy.
BACKGROUND: Preoperative autologous blood donation is accepted as a standard of care for radical prostatectomy. Acute normovolemic hemodilution (ANH) is an alternative method for obtaining autologous blood. The cost and benefits of these two autologous blood-collection techniques are compared. STUDY DESIGN AND METHODS: Thirty consecutive patients scheduled for radical prostatectomy underwent ANH to a target hematocrit level of 28 percent. Blood was transfused in the perioperative period to maintain the hematocrit level > 25 percent. Hematocrit levels, transfusion outcomes and costs, and postoperative outcomes for these patients (hemodilution group) were compared with a matched patient cohort who preoperatively donated 3 units of blood for autologous use in prostatectomy surgery (nonhemodilution group, n = 30). RESULTS: Thirty patients underwent ANH to a hematocrit level of 28.7 +/- 1.7 percent, and 1740 +/- 346 mL (3.5 +/- 0.7 units) of blood were collected. Three (10%) of the patients in each cohort had allogeneic blood exposure. Transfusion costs were 73 percent higher for the nonhemodilution group patients than for the hemodilution group patients ($330 +/- $100 vs. $191 +/- $55, p < 0.001). No differences were found in postoperative outcomes. CONCLUSION: An integrated blood conservation program utilizing hemodilution and a defined transfusion trigger can decrease the requirement for preoperative donation of blood for autologous use in radical prostatectomy. Point-of-care autologous blood procurement is more cost-effective than preadmission donation of autologous blood units.
The extraperitoneal approach and subcutaneous emphysema are associated with greater absorption of carbon dioxide during laparoscopic renal surgery.
PURPOSE: We investigated the association of carbon dioxide absorption with the approach (transperitoneal versus extraperitoneal) and other factors during laparoscopy. MATERIALS AND METHODS: Carbon dioxide elimination during laparoscopic renal surgery was retrospectively calculated in 63 patients. RESULTS: Carbon dioxide elimination increased with time. Multiple factorial analysis revealed that subcutaneous emphysema and the extraperitoneal approach were independently associated with a greater increase in carbon dioxide elimination. Pneumothorax and pneumomediastinum were more common during extraperitoneal procedures. CONCLUSIONS: Carbon dioxide absorption during laparoscopic renal surgery increases with time, and is greatest in patients treated through an extraperitoneal approach and in those with subcutaneous emphysema. Nonetheless, with attentive ventilatory management adverse sequelae of hypercapnia can be avoided.
Carbon dioxide absorption during laparoscopic pelvic operation.
BACKGROUND: Several factors may influence the degree of carbon dioxide (CO2) absorption during laparoscopy. Hypercapnia as a result of excessive CO2 absorption may have adverse clinical effects. STUDY DESIGN: To identify factors associated with increased CO2 absorption, we retrospectively calculated the CO2 elimination in 65 adult patients who underwent operative pelvic laparoscopy. Increases in CO2 elimination were assumed to be indicative of CO2 absorption. The most commonly performed procedures were bladder neck suspension and pelvic lymphadenectomy. The median insufflation time was 165 minutes. An extraperitoneal approach was taken in 32 percent of the patients. RESULTS: Of patients evaluated with postoperative roentgenograms of the chest, 35 percent had subcutaneous emphysema and 9 percent had pneumomediastinum with or without pneumothorax. Multiple factorial analysis of the variance revealed that the extraperitoneal approach, development of subcutaneous emphysema, and increased duration of insufflation were independently associated with a greater increase in peak CO2 elimination. Insufflation time and subcutaneous emphysema had stronger effects in the extraperitoneal group. CONCLUSIONS: The risk factors for hypercapnia can be identified. Careful consideration of the patient's ability to tolerate hypercapnia should be made when planning extraperitoneal laparoscopy, especially if the procedure is likely to be prolonged. The clinical development of subcutaneous emphysema should alert the surgeon to the possibility of subsequent hypercapnia.
Efficacy and cost-effectiveness of autologous blood predeposit in patients undergoing radical prostatectomy procedures.
OBJECTIVES: To assess the efficacy and cost-effectiveness of preoperative autologous blood donation (PAD) in radical prostatectomy procedures. METHODS: A retrospective 3-year review was performed of transfusion outcomes in radical prostatectomy procedures. Cost, benefits, and cost-effectiveness were established using a previously published Markov decision analysis model. RESULTS: Three hundred eighty-four (97%) of 394 patients predonated 3.5 +/- 0.6 (mean +/- SD) autologous blood units. Of these, 2.1 +/- 1.2 units (60%) were retransfused. Forty-two (11%) of 394 patients also received allogeneic blood. Autologous blood donors received only 0.2 +/- 0.6 allogeneic blood units, compared with 1.4 +/- 1.4 (p < 0.05) units transfused to patients who did not predonate. The net costs of PAD ranged from $83 to $303 per procedure. The life-expectancy benefit of PAD ranged from 0.05 to 0.07 days. The overall cost-effectiveness of PAD was estimated to be $1,813,000 per quality adjusted life-year saved. However, PAD was significantly more cost-effective for 2 unit donations ($531,000 per quality adjusted life-year saved). CONCLUSIONS: We conclude that autologous blood donation is an effective blood conservation strategy in elective radical prostatectomy. However, the cost-effectiveness of this practice compares unfavorably with that reported for other medical interventions. Alternative and more cost-effective strategies to reduce the need for allogeneic blood in this setting must be developed.
Laparoscopic pneumoperitoneum: impact of body habitus.
The purpose of this study was to determine the relationships among pneumoperitoneum pressure, CO2 insufflation volume, and patient height, weight, and body mass index. Forty-one male patients undergoing laparoscopic urologic procedures prospectively had a record made of the delivered volume of CO2 during insufflation to attain intraabdominal pressures of 5, 10, 15, 20, 25, and 30 mm Hg. The relationship of the delivered volume of CO2 insufflated and the intraabdominal pressure was compared statistically to the patient height, weight, and body mass index. In addition, six domestic female pigs underwent pneumoperitoneum, and the abdominal volume was calculated for intraabdominal pressures of 0, 5, 10, 15, 20, 25, and 30 mm Hg. Four different commercially available 10-mm trocars were tested for force required for placement at intraabdominal pressures of 15 and 30 mm Hg. There was a direct relationship between delivered volume of CO2 insufflated and the pneumoperitoneum pressure. There was no significant relationship between the delivered volume of CO2 insufflated at a given intraabdominal pressure and the patient height, weight, or body mass index. During insufflation, 94% of the abdominal volume is achieved by insufflating to 15 mm Hg. There is no significant difference in the force required for insertion of different ports at 15 mm vs 30 mm Hg pressure. Increasing the abdominal pressure to 30 mm Hg provides a 50% increase in the volume of CO2 insufflated vs a standard 15 mm Hg pneumoperitoneum. However, this additional volume does not significantly change the actual abdominal volume or diminish the pressure necessary to insert a trocar.
Comparison of transesophageal atrial pacing with anticholinergic drugs for the treatment of intraoperative bradycardia.
We compared the effectiveness of atropine, glycopyrrolate, and a transesophageal atrial pacing (TAP) stethoscope for treating intraoperative bradycardia in 64 unpremedicated patients receiving a standardized sufentanil/N2O/vecuronium anesthetic. Patients were allocated randomly to receive either atropine, 5 micrograms/kg (Group 1), glycopyrrolate, 2.5 micrograms/kg (Group 2), or transesophageal atrial pacing (Group 3) after the onset of bradycardia, defined as a heart rate of < or = 50 beats/min (or < or = 60 beats/min with concurrent hypotension). Bradycardia occurred in 15 patients of each treatment group. The time required for the heart rate to increase to > or = 70 beats/min was 270 (range 30-490), 270 (70-465), and 12 (2-30) s in Groups 1, 2, and 3, respectively. Although all patients in Group 3 responded to pacing at 150% of the threshold current, 10 patients in Group 1 and 8 patients in Group 2 required a second dose of anticholinergic medication before a heart rate response was observed. One patient in Group 2 required three doses, and another who did not respond even after four doses was treated with the TAP device. Bradycardia subsequently recurred in five patients in Group 1 and four patients in Group 2. Temporary recurrence of bradycardia occurred in seven patients in Group 3 due to outward migration of the pacing stethoscope. However, heart rates were more consistently maintained in paced patients. There were no significant differences in postoperative side effects between the three groups, or when compared with patients who did not receive treatment for bradycardia.(ABSTRACT TRUNCATED AT 250 WORDS)