Sensorineural Hearing Loss in Nasopharyngeal Carcinoma Survivors in the Modern Treatment Era - The Early and Late Effects of Radiation and Cisplatin.

AIMS: Hearing loss is a common debilitating complication in nasopharyngeal carcinoma (NPC) survivors. The aim of the present study was to investigate the impact of inner ear/cochlear radiation dose and cisplatin use on early and late sensorineural hearing loss (SNHL) in NPC patients treated with radiotherapy alone, concurrent chemoradiation (cCRT) and induction chemotherapy followed by cCRT (iCRT) in the intensity-modulated radiotherapy era. MATERIALS AND METHODS: The study included 81 NPC patients treated with intensity-modulated radiotherapy between 2014 and 2016. Pure tone audiometry was carried out at baseline and follow-up. The effects of cochlear/inner ear radiation and cisplatin doses on early (<12 months) and late (≥24 months) SNHL were analysed using multivariable regression after adjusting for important predictors. RESULTS: In total, 156 ears were examined. In early SNHL (n = 136), cisplatin use predicted the incidence of early high-frequency SHNL (HF-SNHL) (odds ratio 6.4, 95% confidence interval 1.7-23.9, P = 0.005). Ninety ears were analysed for late SNHL (median follow-up 38 months). Inner ear/cochlear radiation and cisplatin doses and better pre-treatment hearing were independent predictors of threshold change at 4 kHz. Every 10 Gy increase in inner ear/cochlear Dmean resulted in 5-dB and 6-dB threshold changes, respectively (cochlear Dmean: B = 0.005, 95% confidence interval 0.0004-0.009, P = 0.031; inner ear Dmean: B = 0.006, 95% confidence interval 0.001-0.010, P = 0.014). Cisplatin use was associated with late HF-SNHL (odds ratio 3.74, 95% confidence interval 1.1-12.3, P = 0.031). In the cCRT and iCRT subgroups, no cisplatin dose-dependent ototoxicity was observed. Severe (≥30 dB) late HF-SNHL occurred in 14% and 25% of the patients when the cochlear dose constraints were 40 Gy and 44 Gy, respectively. The radiotherapy-alone group did not develop severe late HF-SNHL. CONCLUSION: Cochlear/inner ear radiation dose and cisplatin use showed differential and independent ototoxicity in early and late SNHL. As cochlear/inner ear dose-dependent ototoxicity was demonstrated, the cochlear dose constraint should be as low as reasonably achievable, especially when cisplatin is also administered.

Use of face masks in a primary care outpatient setting in Hong Kong: Knowledge, attitudes and practices.

OBJECTIVES: To assess if a knowledge gap exists in the correct use of face masks, and to explore the correlations between knowledge, attitudes and practices regarding the use of face masks among outpatients and their caregivers in an outpatient clinic in Hong Kong. STUDY DESIGN: Cross-sectional study. METHODS: Outpatients and their caregivers who were present at an outpatient setting in Hong Kong were invited to participate in this survey. All participants were asked to complete a self-administered closed-ended questionnaire about their knowledge, attitudes and practices regarding the use of face masks. Data were described using descriptive statistics and correlation coefficients. RESULTS: Among the 399 respondents, 52% knew the correct steps in wearing a face mask, and their attitudes toward face masks were generally positive. Further analyses showed that respondents were more likely to wear a face mask at a clinic than in a public place or at home. Moreover, respondents were more likely to wear a face mask to protect others against influenza-like illness (ILI) than for self-protection. There was low to moderate correlation between attitudes and practices (correlation coefficient 0.26, P < 0.05). CONCLUSIONS: This study identified a knowledge gap in the correct use of face masks among outpatients and their caregivers; attitudes and practices regarding the use of face masks were generally positive, but correlation was not high. It is recommended that public health education campaigns should tailor efficient programmes to combat ILI transmission among outpatient clinic populations by improving knowledge about the correct use of face masks.

Robotic ultrasound-guided prostate intervention device: system description and results from phantom studies.

BACKGROUND: We introduce the first robotic ultrasound-guided prostate intervention device and evaluate its safety, accuracy and repeatability. METHODS: The robotic positioning system (RPS) determines a target's x, y and z axes. It is situated with a biplane ultrasound probe on a mobile horizontal platform. The integrated software acquires ultrasound images for three-dimensional (3D) modelling, coordinates target planning and directs the RPS. RESULTS: The egg phantom evaluates the software's safety and workflow protocol. Two random targets are planned in each quadrant and biopsy needles are inserted. All were within three separate eggs. Metal wire tips are targeted and their distances from the biopsy needle tips are measured. With 20 wires, < 1 mm accuracy is obtained. Repeatability is demonstrated when previous positions are returned to with similar accuracy. CONCLUSION: Our device demonstrates safety in a defined boundary with a repeatable accuracy of < 1 mm. It can be used for accurate prostate biopsy and treatment delivery.

A rare life-threatening complication of migrated nitinol self-expanding metallic stent (Ultraflex).

The use of self-expanding metallic stents (SEMS) as esophageal endoprosthesis represents an advancement in the palliation of dysphagia from unresectable esophageal carcinoma. However, the problem of stent migration persists. Although most migrated stents have a benign outcome, complications do occur. Rare reports of intestinal obstruction have been confined to the stiff plastic and stainless-steel stents. We report the first case of intestinal obstruction secondary to the pliable Nitinol SEMS (Ultraflex) migration.

Effects of pneumoperitoneum on intraoperative pulmonary mechanics and gas exchange during laparoscopic gastric bypass.

BACKGROUND: Hypercarbia and elevated intraabdominal pressure resulting from carbon dioxide (CO2) pneumoperitoneum can adversely affect respiratory mechanics. This study examined the changes in mechanical ventilation, CO2 homeostasis, and pulmonary gas exchange in morbidly obese patients undergoing a laparoscopic or open gastric bypass (GBP) procedure. METHODS: In this study, 58 patients with a body mass index (BMI) of 40 to 60 kg/m2 were randomly allocated to laparoscopic ( n = 31) or open ( n = 27) GBP. Minute ventilation was adjusted to maintain a low normal arterial partial pressure of CO2 (PaCO2), low normal end-tidal partial pressure of CO2 (ETCO2), and low airway pressure. Respiratory compliance, ETCO2, peak inspiratory pressure (PIP), total exhaled CO2 per minute (VCO2), and pulse oximetry (SO2) were measured at 30-min intervals. The acid-base balance was determined by arterial blood gas analysis at 1-h intervals. The pulmonary gas exchange was evaluated by calculation of the alveolar dead space-to-tidal volume ratio (V(Dalv)/V(T)) and alveolar-arterial oxygen gradient (PAO2-PaO2). RESULTS: The two groups were similar in age, gender, and BMI. As compared with open GBP, laparoscopic GBP resulted in higher ETCO2, PIP, and VCO2, and a lower respiratory compliance. Arterial blood gas analysis demonstrated higher PaCO2 and lower pH during laparoscopic GBP than during open GBP ( p < 0.05). The V(Dalv)/V(T) ratio and PAO2-PaO2 gradient did not change significantly during laparoscopic GBP. Intraoperative oxygen desaturation (SO2 < 90%) did not develop in any of the patients in either group. CONCLUSIONS: Laparoscopic GBP alters intraoperative pulmonary mechanics and acid-base balance but does not significantly affect pulmonary oxygen exchange. Changes in pulmonary mechanics are well tolerated in morbidly obese patients when proper ventilator adjustments are maintained.

Age-related differences in Na+-dependent Ca2+ accumulation in rabbit hearts exposed to hypoxia and acidification.

In this study, we test the hypothesis that in newborn hearts (as in adults) hypoxia and acidification stimulate increased Na(+) uptake, in part via pH-regulatory Na(+)/H(+) exchange. Resulting increases in intracellular Na(+) (Na(i)) alter the force driving the Na(+)/Ca(2+) exchanger and lead to increased intracellular Ca(2+). NMR spectroscopy measured Na(i) and cytosolic Ca(2+) concentration ([Ca(2+)](i)) and pH (pH(i)) in isolated, Langendorff-perfused 4- to 7-day-old rabbit hearts. After Na(+)/K(+) ATPase inhibition, hypoxic hearts gained Na(+), whereas normoxic controls did not [19 +/- 3.4 to 139 +/- 14.6 vs. 22 +/- 1.9 to 22 +/- 2.5 (SE) meq/kg dry wt, respectively]. In normoxic hearts acidified using the NH(4)Cl prepulse, pH(i) fell rapidly and recovered, whereas Na(i) rose from 31 +/- 18.2 to 117.7 +/- 20.5 meq/kg dry wt. Both protocols caused increases in [Ca](i); however, [Ca](i) increased less in newborn hearts than in adults (P < 0.05). Increases in Na(i) and [Ca](i) were inhibited by the Na(+)/H(+) exchange inhibitor methylisobutylamiloride (MIA, 40 microM; P < 0.05), as well as by increasing perfusate osmolarity (+30 mosM) immediately before and during hypoxia (P < 0.05). The data support the hypothesis that in newborn hearts, like adults, increases in Na(i) and [Ca](i) during hypoxia and after normoxic acidification are in large part the result of increased uptake via Na(+)/H(+) and Na(+)/Ca(2+) exchange, respectively. However, for similar hypoxia and acidification protocols, this increase in [Ca](i) is less in newborn than adult hearts.

Cardiac function during laparoscopic vs open gastric bypass.

BACKGROUND: Hypercarbia and increased intraabdominal pressure during prolonged pneumoperitoneum can adversely affect cardiac function. This study compared the intraoperative hemodynamics of morbidly obese patients during laparoscopic and open gastric bypass (GBP). METHODS: Fifty-one patients with a body mass index (BMI) of 40-60 kg/m2 were randomly allocated to undergo laparoscopic (n = 25) or open (n = 26) GBP. Cardiac output (CO), mean pulmonary artery pressure (MPAP), pulmonary artery wedge pressure (PAWP), central venous pressure (CVP), heart rate (HR), and mean arterial pressure (MAP) were recorded at baseline, intraoperatively at 30-min intervals, and in the recovery room. Systemic vascular resistance (SVR) and stroke volume (SV) were also calculated. RESULTS: The two groups were similar in terms of age, weight, and BMI. Operative time was longer in the laparoscopic than in the open group (p < 0.05). The HR and MAP increased significantly from baseline intraoperatively, but there was no significant difference between the two groups. In the laparoscopic group, CO was unchanged after insufflation, but it increased by 5.3% at 2.5 h compared to baseline and by 43% compared to baseline in the recovery room. In contrast, during open GBP, CO increased significantly by 25% after surgical incision and remained elevated throughout the operation. CO was higher during open GBP than during laparoscopic GBP at 0.5 h and at 1 h after surgical incision (p < 0.05). During laparoscopic GBP, CVP, MPAP, and SVR increased transiently and PAWP remained unchanged. During open GBP, CVP, MPAP, and PAWP decreased transiently and SVR remained unchanged. There was no significant difference in the amount of intraoperative fluid administered during laparoscopic (5.5 +/- 1.6 L) and open (5.6 +/- 1.7 L) GBP. CONCLUSION: Prolonged pneumoperitoneum during laparoscopic gastric bypass does not impair cardiac function and is well tolerated by morbidly obese patients.

The Frey procedure: local resection of pancreatic head combined with lateral pancreaticojejunostomy.

Management of chronic pancreatitis is mainly palliative. Most patients with chronic pancreatitis require surgical evaluation and intervention when there is suspicion of pancreatic malignancy, evidence of intractable pain, or development of pancreatitis-related local complications. The ideal operation for chronic pancreatitis, therefore, should be designed to exclude the existence of malignancy, provide long-lasting pain relief, and correct the local complications. It should be as simple and safe as possible and should preserve the remaining endocrine and exocrine functions of the pancreas.

Safety of metallic implants in magnetic resonance imaging.

Magnetic resonance (MR) imaging has become a commonly accepted medical procedure. Manufacturers of medical implant devices are submitting claims that their devices are safe and effective in a MR environment. This paper concentrates on the issue of heating of patients due to the interaction of metallic implants with the strong radiofrequency (RF) magnetic field produced by the MR scanner. The commercially available program XFDTD was used to calculate the specific absorption rate (SAR) distribution in a realistic model of the human body. The body contained a metallic implant and was exposed to RF magnetic fields at 64 MHz from a model of a MR birdcage body coil. The results of the calculation showed that the magnitude of the increased heating of tissues due to the presence of the metallic implant depended on the dimensions, orientation, shape, and location of the metallic implant in the patient. This increased heating of surrounding tissues primarily concentrates in a small volume near the tip of the metallic wire. When the whole-body SAR was normalized to 1 W/kg, a calculated value of 41 W/kg was obtained at this location if the absorption was averaged over 1 g of tissue. However, a maximum value of 310 W/kg was calculated when the absorption was averaged over 1/8 g of tissue.

Factors affecting choice of surgical residency training program.

BACKGROUND: A significant problem facing American surgery today is the lack of participation from women and minorities. In 1995 and 1996, 15.1 and 15.8% of United States general surgical residency graduates were women. Of our 71 graduates in the last 12 years, 38% were women. The aim of this study was to identify the factors influencing our residents' choice of training program and the reasons why our program has a high percentage of female graduates. METHODS: Between 1989 and 2000, 27 women and 44 men completed general surgical training at our university and 44/71 (59%) responded to our survey. The age at residency completion was 34 +/- 2.2 years for men and 33.9 +/- 2.8 years for women. Fifty-five percent of men and 30% of women went on to fellowship training; and 36% of men and 20% of women are in academia. RESULTS: Factors influencing our graduates' selection of training program are: Only 23% of men had a female faculty as their mentor, whereas 90% of women had a male faculty as their mentor during training. Only 59% of men but 80% of women (P < 0.05) agreed that female medical students need role models of successful female faculty members. Fifty-five percent of men and 45% of women would encourage a female medical student to choose surgery as a career, but 82% of men and 50% of women would encourage a male medical student to do so. Ninety-one percent of men and 85% of women would choose surgery as a career again. CONCLUSIONS: A surgical residency training program with strong leadership, good clinical experience, and high resident morale will equally attract both genders. Women may pay more attention to the program's gender mix and geographic location.

Childbearing and child care in surgery.

HYPOTHESIS: The responsibility for childbearing and child care has a major effect on general surgical residency and subsequent surgical practice. METHODS: A survey of all graduates from a university general surgical training program between 1989 and 2000. RESULTS: Twenty-seven women and 44 men completed general surgical training at our university during the period, and 42 (59%) responded to our survey. The age at completion of the residency was 34.0 +/- 2.2 years for men and 33.9 +/- 2.8 years for women. During residency, 64% (14/22) of the men and 15% (3/20) of the women had children. At the time of the survey, 21 (95%) of the men and 8 (40%) of the women had children. Most residents (24 [57%] of 42) relied on their spouse for child care. During surgical practice, 18 (43%) indicated that they rely on their spouse; 19 (45%) use day care, home care, or both; and (8%) of 26 are unsatisfied with their current child care arrangement. During training, 38% (5/13) of men and 67% (2/3) of women took time off for maternity leave, paternity leave, or child care. Two of 3 surgeons would like to have had more time off during residency; most men (70%, or 7 of 10) recommended a leave of 1 to 3 months, and all women preferred a 3-month maternity or child care leave of absence. During surgical practice, only 12% (2/17) of men but 64% (7/11) of women have taken time off for either childbearing or child care. Half of the respondents (21/42) have a formal leave of absence policy at work, 52% (11/21) of which are paid leave programs. Although the workweek of our practicing graduates is 69 +/- 16 hours for men and 64 +/- 12 hours for women, 62% (26/42) spend more than 20 hours per week parenting. More than 80% (27/32) would consider a part-time surgical practice for more parenting involvement; one third of the responders suggested that 30 hours a week constitutes a reasonable part-time practice, one third preferred fewer than 30 hours, and one third favored more than 30 hours per week. Data are presented as mean +/- SD. CONCLUSIONS: Childbearing and child care may have an enormous impact on one's decision to pursue a career in surgery. To attract and retain the best candidates for future surgeons, formal policies on the availability of child care services in the residency program and the workplace should be studied and implemented. Furthermore, national studies are needed to define appropriate, acceptable workweeks for part-time or flexible practices and the duration of leaves of absence for childbearing or child care.

Computed tomography and ultrasonography do not improve and may delay the diagnosis and treatment of acute appendicitis.

HYPOTHESIS: Computed tomography (CT) and ultrasonography (US) do not improve the overall diagnostic accuracy for acute appendicitis. DESIGN: Retrospective review. SETTING: University tertiary care center. PATIENTS: Seven hundred sixty-six consecutive patients undergoing appendectomy for suspected appendicitis from January 1, 1995, to December 31, 1999. MAIN OUTCOME MEASURES: Epidemiology of acute appendicitis and the roles of clinical assessment, CT, US, and laparoscopy. RESULTS: The negative appendectomy rate was 15.7%, and the incidence of perforated appendicitis was 14.6%. A history of migratory pain had the highest positive predictive value (91%), followed by leukocytosis greater than 12 x 10(9)/L (90.1%), CT (83.8%), and US (81.3%). The false-negative rates were 60% for CT and 76.1% for US. Emergency department evaluation took a mean +/- SD of 5.2 +/- 5.4 hours and was prolonged by US or CT (6.4 +/- 7.4 h and 7.8 +/- 10.8 h, respectively). The duration of emergency department evaluation did not affect the perforation rate, but patients with postoperative complications had longer evaluations (mean +/- SD, 8.0 +/- 12.7 h) than did those without (4.8 +/- 3.3 h) (P =.04). Morbidity was 9.1%, 6.4% for nonperforated cases and 19.8% for perforated cases. Seventy-six patients had laparoscopic appendectomy, with a negative appendectomy rate of 42.1%, compared with 15.4% for open appendectomy (P<.001). Laparoscopy, however, had minimal morbidity (1.3%) and correctly identified the abnormality in 91.6% of patients who had a normal-appearing appendix. CONCLUSIONS: Migratory pain, physical examination, and initial leukocytosis remain reliable and accurate in diagnosing acute appendicitis. Neither CT nor US improves the diagnostic accuracy or the negative appendectomy rate; in fact, they may delay surgical consultation and appendectomy. In atypical cases, one should consider the selective use of diagnostic laparoscopy instead.

A prospective evaluation of intracorporeal laparoscopic small bowel anastomosis during gastric bypass.

BACKGROUND: We evaluated the safety and feasibility of performing a laparoscopic intracorporeal end-to-side small bowel anastomosis using a stapling technique as part of a Roux-en-Y gastric bypass operation (RYGBP). METHODS: 80 consecutive patients who underwent RYGBP with laparoscopic jejunojejunostomy were evaluated. Operative time and intraoperative and postoperative complications directly related to the jejunojejunostomy anastomosis were recorded. RESULTS: All 80 laparoscopic jejunojejunostomy procedures were successfully performed without conversion to laparotomy. Mean operative time was longer for the first 40 laparoscopic RYGBP than for the last 40 RYGBP (32+/-18 min vs 21+/-14 min, respectively, p<0.05). Intraoperative complications were staple-line bleeding (2 patients) and narrowing of the anastomosis (1 patient). Postoperative complications were four small bowel obstructions: technical narrowing at jejunojejunostomy site (2 patients), angulation of the afferent limb (1 patient), and food impaction at the jejunojejunostomy anastomosis (1 patient). These four patients underwent successful laparoscopic re-exploration and creation of another jejunojejunostomy proximal to the original anastomosis. There were no small bowel anastomotic leaks. The median time to resuming oral diet was 2 days. CONCLUSIONS: Laparoscopic jejunojejunostomy as part of the RYGBP operation is a safe and technically feasible procedure. Postoperative small bowel obstruction is a potential complication, which can be prevented by avoiding technical narrowing of the afferent limb.

An ergonomic evaluation of surgeons' axial skeletal and upper extremity movements during laparoscopic and open surgery.

BACKGROUND: Many surgeons have complained of fatigue and musculoskeletal pain after laparoscopic surgery. We evaluated differences in surgeons' axial skeletal and upper extremity movements during laparoscopic and open operations. METHODS: Five surgeons were videotaped performing 16 operations (8 laparoscopic and 8 open) to record their neck, trunk, shoulder, elbow, and wrist movements during the first hour of surgery. We also compared postprocedural complaints of pain, stiffness, or numbness between the two groups. RESULTS: Compared with surgeons performing open surgery, surgeons performing laparoscopic surgery exhibited less lateral neck flexion; less trunk flexion; more internal rotation of the shoulders; more elbow flexion; more wrist supination and wrist ulnar and radial deviation. There was a trend of more shoulder stiffness after laparoscopic operations than after open operations. CONCLUSIONS: Laparoscopic surgery involves a more static posture of the neck and trunk, but more frequent awkward movements of the upper extremities than open surgery. Ergonomic changes in the operating room environment and instrument design could ease the physical stress imposed on surgeons during laparoscopic operations.

A comparison study of laparoscopic versus open gastric bypass for morbid obesity.

BACKGROUND: Laparoscopic Roux-en-Y gastric bypass (GBP) has been previously described, but a comparative study between laparoscopic and open GBP has not been reported. The purpose of this study was to compare surgical outcomes oflaparoscopic GBP with those of open GBP for treatment of morbid obesity. STUDY DESIGN: From August 1998 to September 1999, we prospectively collected outcome data on 35 patients with body-mass indices between 40 kg/m2 and 60 kg/m2 who underwent laparoscopic GBP. Demographics, operative data, perioperative complications, and weight losses were collected and compared with those obtained from a retrospective chart review of 35 patients with body-mass indices between 40 kg/m2 and 60 kg/m2 who underwent open GBP before August 1998. RESULTS: Age, gender, preoperative body-mass index, preoperative comorbidity, and earlier abdominal surgery were similar in both groups. All laparoscopic operations were completed without conversion to laparotomy. Mean operative time, operative blood loss, length of intensive care stay, and length of hospital stay were significantly less after laparoscopic GBP than after open GBP (p<0.05). There was no 30-day mortality in either group. At 1-year followup, analysis of the percentage of excess body weight loss showed no significant difference between the two groups (p<0.05). CONCLUSIONS: Laparoscopic Roux-en-Y gastric bypass is technically feasible and safe. Laparoscopic GBP confers the clinical benefits of laparoscopy and an initial weight loss similar to that of open GBP.

Laparoscopic suturing evaluation among surgical residents.

BACKGROUND: Laparoscopic suturing is an integral part of advanced laparoscopic surgery training. The objective of this study was to evaluate the performance and preference of surgical residents performing intracorporeal and extracorporeal knot-tying techniques using conventional and Endo Stitch instruments. The residents were also evaluated on their suturing techniques using conventional instruments, the Endo Stitch, and the Suture Assistant. METHODS: Using an inanimate laparoscopic trainer model, 39 residents were evaluated as they performed laparoscopic knot tying exercises. Endpoints of the study were execution time and subjective preference of surgical residents with respect to the type of instrument used for knot tying. Forty-three residents were evaluated as they performed laparoscopic suturing exercises with three different types of suturing instruments using the same endpoints. RESULTS: The intracorporeal technique was the preferred (89%) method of knot tying among surgical residents. The time for completion of laparoscopic suturing was significantly (P < 0.05) shorter with the Endo Stitch (114 +/- 64 s) than with the conventional instrument (206 +/- 107 s) or the Suture Assistant (151 +/- 70 s). Residents preferred the use of the Endo Stitch in all three categories for suturing, knot tying, and handling. CONCLUSION: The Endo Stitch enhanced laparoscopic skills and was the preferred instrument for laparoscopic knot tying and suturing among surgical residents.

Laparoscopic umbilical herniorrhaphy.

BACKGROUND: Laparoscopic technique is an alternative approach to ventral hernia repair. This study evaluated the feasibility of performing umbilical hernia repair using a single 5-mm trocar technique. PATIENTS AND METHODS: During February 1999 to November 1999, we performed laparoscopic umbilical hernia repair in 16 consecutive patients. All operations were performed under general anesthesia. One 5-mm port was used to visualize the defect. A second 5-mm port was inserted only if there was incarcerated omentum requiring reduction. The Endo Close was inserted through a 2-mm incision made directly over the hernia to perform transabdominal closure of the defect using nonabsorbable suture. RESULTS: The mean size of the umbilical hernia defects was 1.2 cm +/- 0.4 (range 1.0-2.0 cm). All operations were completed laparoscopically with no intraoperative or postoperative complications. The mean operative time was 35 +/- 15 minutes (range 21-75 min). All cases were performed in an outpatient setting. There have been no recurrences at a mean follow-up of 5.9 months. CONCLUSIONS: Laparoscopic umbilical herniorrhaphy is safe and technically feasible. Its potential advantages, such as a lower rate of recurrence, will need to be validated with longer follow-up.

Hypertonic perfusion inhibits intracellular Na and Ca accumulation in hypoxic myocardium.

Much evidence supports the view that hypoxic/ischemic injury is largely due to increased intracellular Ca concentration ([Ca](i)) resulting from 1) decreased intracellular pH (pH(i)), 2) stimulated Na/H exchange that increases Na uptake and thus intracellular Na (Na(i)), and 3) decreased Na gradient that decreases or reverses net Ca transport via Na/Ca exchange. The Na/H exchanger (NHE) is also stimulated by hypertonic solutions; however, hypertonic media may inhibit NHE's response to changes in pH(i) (Cala PM and Maldonado HM. J Gen Physiol 103: 1035-1054, 1994). Thus we tested the hypothesis that hypertonic perfusion attenuates acid-induced increases in Na(i) in myocardium and, thereby, decreases Ca(i) accumulation during hypoxia. Rabbit hearts were Langendorff perfused with HEPES-buffered Krebs-Henseleit solution equilibrated with 100% O(2) or 100% N(2). Hypertonic perfusion began 5 min before hypoxia or normoxic acidification (NH(4)Cl washout). Na(i), [Ca](i), pH(i), and high-energy phosphates were measured by NMR. Control solutions were 295 mosM, and hypertonic solutions were adjusted to 305, 325, or 345 mosM by addition of NaCl or sucrose. During 60 min of hypoxia (295 mosM), Na(i) rose from 22+/-1 to 100+/-10 meq/kg dry wt while [Ca](i) rose from 347+/-11 to 1,306+/-89 nM. During hypertonic hypoxic perfusion (325 mosM), increases in Na(i) and [Ca](i) were reduced by 65 and 60%, respectively (P<0.05). Hypertonic perfusion also diminished Na uptake after normoxic acidification by 87% (P<0.05). The data are consistent with the hypothesis that mild hypertonic perfusion diminishes acid-induced Na accumulation and, thereby, decreases Na/Ca exchange-mediated Ca(i) accumulation during hypoxia.

Effect of intravascular volume expansion on renal function during prolonged CO2 pneumoperitoneum.

OBJECTIVE: To evaluate whether intravascular volume expansion would improve renal blood flow and function during prolonged CO2 pneumoperitoneum. SUMMARY BACKGROUND DATA: Although laparoscopic living donor nephrectomies have a considerably reduced risk of complications for the donors, significant concerns exist regarding procurement of a kidney in the altered physiologic environment of CO2 pneumoperitoneum. Recent studies have documented adverse effects of CO2 pneumoperitoneum on renal hemodynamics. METHODS: Renal and systemic hemodynamics and renal histology were studied in a porcine CO2 pneumoperitoneum model. After placement of a pulmonary artery catheter, carotid arterial line, Foley catheter, and renal artery ultrasonic flow probe, CO2 pneumoperitoneum (15 mmHg) was maintained for 4 hours. Pigs were randomized into three intravascular fluid protocol groups: euvolemic (3 mLkg/hour isotonic crystalloid), hypervolemic (15 mL/kg/hour isotonic crystalloid), or hypertonic (3 mL/kg/hour isotonic crystalloid plus 1.2 mL/kg/hour 7.5% NaCl). RESULTS: In the euvolemic group, prolonged CO2 pneumoperitoneum caused decreased renal blood flow, oliguria, and impaired creatinine clearance. Both isotonic and hypertonic volume expansions reversed the changes in renal blood flow and urine output, but impaired creatinine clearance persisted. CONCLUSIONS: Intravascular volume expansion alleviates the effects of CO2 pneumoperitoneum on renal hemodynamics in a porcine model. Hypertonic saline (7.5% NaCl) solution may maximize renal blood flow in prolonged pneumoperitoneum, but it does not completely prevent renal dysfunction in this setting. This study suggests that routine intraoperative volume expansion is important during laparoscopic live donor nephrectomy.