Fatal dysnatraemia caused by elective colonoscopy

Advances in Bowel Preparation and Antimicrobial Prophylaxis for Open and Laparoscopic Urologic Surgery

Surgical site infections (SSIs) represent a major source of postoperative complications adversely impacting morbidity and mortality indices in surgical care. The discovery of antibiotics in the mid-20th century, and their ensuing use for preoperative antimicrobial bowel preparation and prophylaxis, drastically reduced the occurrence of SSIs providing a major tool to surgeons of various specialties, including urology. Because, the appropriate use of these antimicrobials is critical for their continued safety and efficacy, an understanding of the recommendations guiding their application is essential for all surgeons. Here, we comprehensively review these recommendations with a focus on open and laparoscopic urologic surgeries.

A case of severe acute hyponatremia after colonoscopy with polyethylene glycol plus ascorbic acid bowel preparation

Previous reports have shown that bowel preparation can, in extremely rare circumstances, induce severe acute hyponatremia. Polyethylene glycol plus ascorbic acid as a bowel preparation is considered relatively safe with a smaller amount of free water load and a more pleasant taste with additives.We present the case of an 86-year-old man who developed severe acute hyponatremia presenting with tremor and impaired consciousness after colonoscopy, which is life-threatening. The severe hyponatremia in our case was not caused by free water loads from drinking large amounts of water during bowel preparation or hypovolemia due to bowel preparation-induced nausea, vomiting, and diarrhea, but might have been due to non-osmotic stimuli of antidiuretic hormone (ADH) release (i.e., pre-existing nausea, stress, anxiety, pain, stress, or the colonoscopy itself). Our study indicates that it is important to choose safer bowel preparation solutions, to be aware of ingested water volumes, to assess volume status, and also remain aware of other coexisting risk factors for acute hyponatremia, such as medical history, medication, and ADH release, especially in elderly patients.

Hyponatremia-induced generalized seizure after taking polyethylene glycol for colon preparation-A case report and brief review of the literature

Severe hyponatremia is life-threatening in hospitalized patients. We present an elderly female who developed severe hyponatremia, seizure, and loss of consciousness after taking polyethylene glycol (PEG) solution before colonoscopy. The risk of hyponatremia with PEG for colon preparation in elderly susceptible patients is high. We review the relevant literature.

Serum electrolytes, osmolality, and cleansing quality after bowel prep for colonoscopy with a PEG solution containing ascorbic acid and electrolytes

BACKGROUND

The cleansing procedure with PEG 3350 + ascorbic acid (PEG + Asc; Moviprep®) requires the additional ingestion of clear liquids. We aimed to determine the effects on serum electrolytes, osmolality and cleansing quality, and in a prospective "real world" trial.

PATIENTS AND METHODS

Patients underwent a standardized split-dose bowel preparation for colonoscopy with PEG + Asc. Serum electrolytes and osmolality were measured before and after the prep procedure. The volume of prep solution (PA) and additional clear liquid (CL) was recorded. Prep quality was assessed using the Ottawa Bowel Prep Grading Scale (OBPS). The primary outcome measures were changes of serum electrolytes and osmolality during the cleansing procedure. A secondary end point was the OPBS.

RESULTS

One hundred ninety-one of 219 patients entered the per protocol analysis. Prep quality was considered excellent in 57.6%, moderate in 20.9%, and insufficient in 21.5%. The number of patients with hyponatremia increased from 12 (6.3%) before to 25 (13.2%) after the prep procedure. Mean sodium concentration did not change significantly. The volume of CL correlated inversely with Na⁺ concentration (r =  - 0.409, p < 0.01) and a worse OBPS (r = 0.198, p < 0.01).

CONCLUSIONS

Bowel preparation with PEG-Asc in clinical routine is generally safe, but patients should be advised not to drink more than 2 l of clear liquid because of imminent electrolyte disturbances. Additionally, the quality of cleansing either remains unchanged or may even worsen.

Iso-osmolar hyponatremia from polyethylene glycol

Understanding and applying pathophysiological concepts to patient care is an important skill for physicians in the clinical setting. Here, we present a case that demonstrates how the application of common physiological concepts relating to the widely accepted hyponatremia algorithm led to an accurate diagnosis of hyponatremia. This case documents iso-osmolar hyponatremia caused by orally administered polyethylene glycol absorption in the gastrointestinal tract. Herein, we discuss the workup and differential diagnosis for iso-osmolar hyponatremia in juxtaposition with the pathophysiological mechanisms unique to this case. We discuss these pathophysiological mechanisms based on the patients’ laboratory data and responses to therapeutic interventions.

Efficacy of 1.2 L polyethylene glycol plus ascorbic acid for bowel preparations

BACKGROUND

A low-volume polyethylene glycol (PEG) solution that combines ascorbic acid with PEG-based electrolyte solution (PEG-ASC) is gaining mainstream acceptance for bowel preparation due to reduced volume and improved taste. Although several reports showed that bowel preparation with PEG-ASC volume lower than 2.0 L with laxative agents could be an alternative to traditional preparation regimen, the cleansing protocols have not been fully investigated.

AIM

To evaluate the cleansing efficacy of 1.2 L PEG-ASC solution comparing with 2.0 L PEG electrolyte (PEG-ELS) for bowel preparations.

METHODS

A randomized, single-blinded, open-label, single-center, non-inferiority study was conducted. In total, 312 Japanese adult patients (aged > 18 years) who underwent colonoscopy were enrolled. Patients were randomly allocated to bowel lavage with either 1.2 L of PEG-ASC solution with at least 0.6 L of an additional clear fluid (1.2 L PEG-ASC group) or 2.0 L of PEG-ELS (PEG-ELS group). Then, 48 mg of sennoside was administered at bedtime on the day before colonoscopy, and the designated drug solution was administered at the hospital on the day of colonoscopy. Bowel cleansing was evaluated using the Boston Bowel Preparation Scale (BBPS). The volume of fluid intake and required time for bowel preparation were evaluated. Furthermore, compliance, patient tolerance, and overall acceptability were evaluated using a patient questionnaire, which was assessed using a visual analog scale.

RESULTS

In total, 291 patients (1.2 L PEG-ASC group, 148; PEG-ELS group, 143) completed the study. There was no significant difference in successful cleansing, defined as a BBPS score ≥ 2 in each segment, between the two groups (1.2 L PEG-ASC group, 91.9%; PEG-ELS group, 90.2%; 95%CI: -0.03-0.09). The required time for bowel preparation was significantly shorter (164.95 min ± 68.95 min vs 202.16 min ± 68.69 min, P < 0.001) and the total fluid intake volume was significantly lower (2.23 L ± 0.55 L vs 2.47 L ± 0.56 L, P < 0.001) in the 1.2 L PEG-ASC group than in the PEG-ELS group. Palatability, acceptability of the volume of solution, and overall acceptability evaluated using a patient questionnaire, which was assessed by the visual analog scale, were significantly better in the 1.2 L PEG-ASC group than in the PEG-ELS group (7.70 cm ± 2.57 cm vs 5.80 cm ± 3.24 cm, P < 0.001). No severe adverse event was observed in each group.

CONCLUSION

The 1.2 L PEG-ASC solution was non-inferior to the 2.0 L PEG-ELS solution in terms of cleansing efficacy and had better acceptability among Japanese patients.

Magnesium and Drugs Commonly Used in Chronic Kidney Disease

As with other electrolytes, magnesium homeostasis depends on the balance between gastrointestinal absorption and kidney excretion. Certain drugs used commonly in patients with CKD can decrease gastrointestinal ingestion and kidney reclamation, and potentially cause hypomagnesemia. Other magnesium-containing drugs such as laxatives and cathartics can induce hypermagnesemia, particularly in those with impaired glomerular filtration and magnesium excretion. In this review, we will discuss the potential magnesium complications associated with a range of commonly encountered drugs in the care of CKD patients, discuss the potential mechanisms, and provide basic clinical recommendations.

"Bowel prep hyponatremia" - a state of acute water intoxication facilitated by low dietary solute intake: case report and literature review

Background

Symptomatic hyponatremia is considered a rare complication of oral bowel preparation for colonoscopy. The pathophysiology underlying this phenomenon has been widely regarded as a mere sequela of excessive arginine vasopressin (AVP) release.

Case presentation

This case describes a 61-year old woman who developed acute hyponatremic encephalopathy when preparing for elective outpatient lower endoscopy. She had had negligible oral solute intake for two days and ingested four liters of clear fluid within two hours. On admission, the patient was agitated and had slurred speech. Treatment with hypertonic saline lead to full recovery. A brisk aquaresis confirmed acute dilutional hyponatremia.

Conclusion

Apart from elevated AVP-levels, the amount and speed of fluid intake and concomitant low-solute intake constitute important risk factors in the development of clinically relevant hyponatremias in patients undergoing colonoscopies. Understanding that the cause of sodium imbalance in this scenario is multifactorial and complex is pivotal to recognizing and ideally preventing this complication, for which we propose the term “bowel prep hyponatremia”.

Single-day sodium picosulfate and magnesium citrate versus split-dose polyethylene glycol for bowel cleansing prior to colonoscopy: A prospective randomized endoscopist-blinded trial

BACKGROUND AND AIM

The intake of polyethylene glycol (PEG) prior colonoscopy is frequently associated with nausea and abdominal discomfort. The aim of this study was to investigate whether sodium picosulfate and magnesium citrate (PMC) is superior to a polyethylene glycol (PEG) preparation in regard to patient acceptance. Furthermore, it investigates possible differences in efficiency and patient safety.

METHODS

In a randomised, prospective, and endoscopist-blinded study patients were 1:1 randomized to either use PMC or 4-L PEG in order to prepare for colonoscopy. Cleansing regimes consisted of a split-dose administration in the PEG arm and standard administration in the PMC arm. Primary end point was proportion of patients evaluating the bowel preparation procedure as "very distressing," defined as ≥ 8 points on a 10-point numeric rating scale (NRS). Secondary end points were quality of bowel preparation and electrolyte parameters.

RESULTS

PMC bowel-cleansing procedure was better tolerated compared with PEG (PMC(NRS<8)  = 89.9% vs PEG(NRS<8)  = 79.2%, P = 0.037). Mean declines in serum sodium (ΔSodium(PEG)  = -0.76 ± 3.07 vs ΔSodium(PMC)  = -3.38 ± 3.56 mmol/L; P < 0.001), chloride (ΔChloride(PEG)  = -1.00 ± 3.22 vs ΔChloride(PMC)  = -3.49 ± 3.51 mmol/L; P < 0.001), and osmolality (ΔOsmolality(PEG)  = -4.23 ± 6.82 vs ΔOsmolality(PMC)  = -8.83 ± 7.43 mosmol/kg; P < 0.001) were higher in the PMC arm than in the PEG arm. Hyponatremia after bowel preparation occurred more often in PMC (21.2%) than in PEG (4.0%) (P < 0.001). Successful preparation was achieved more frequently in the PEG arm (42.9% vs 82.2%; P < 0.001).

CONCLUSION

Standard picosulfate/magnesium citrate is better accepted than a split-dose PEG regimen. From the perspective of successful preparation and patients' safety, PEG is superior to PMC.

A systematic review and meta-analysis of thiazide-induced hyponatraemia: time to reconsider electrolyte monitoring regimens after thiazide initiation?

AIMS

Hyponatraemia is one of the major adverse effects of thiazide and thiazide-like diuretics and the leading cause of drug-induced hyponatraemia requiring hospital admission. We sought to review and analyze all published cases of this important condition.

METHODS

Ovid Medline, Embase, Web of Science and PubMed electronic databases were searched to identify all relevant articles published before October 2013. A proportions meta-analysis was undertaken.

RESULTS

One hundred and two articles were identified of which 49 were single patient case reports. Meta-analysis showed that mean age was 75 (95% CI 73, 77) years, 79% were women (95% CI 74, 82) and mean body mass index was 25 (95% CI 20, 30) kg m(-2) . Presentation with thiazide-induced hyponatraemia occurred a mean of 19 (95% CI 8, 30) days after starting treatment, with mean trough serum sodium concentration of 116 (95% CI 113, 120) mm and serum potassium of 3.3 (95% CI 3.0, 3.5) mm. Mean urinary sodium concentration was 64 mm (95% CI 47, 81). The most frequently reported drugs were hydrochlorothiazide, indapamide and bendroflumethiazide.

CONCLUSIONS

Patients with thiazide-induced hyponatraemia were characterized by advanced age, female gender, inappropriate saliuresis and mild hypokalaemia. Low BMI was not found to be a significant risk factor, despite previous suggestions. The time from thiazide initiation to presentation with hyponatraemia suggests that the recommended practice of performing a single investigation of serum biochemistry 7-14 days after thiazide initiation may be insufficient or suboptimal. Further larger and more systematic studies of thiazide-induced hyponatraemia are required.

Randomized, controlled trial of 2 L polyethylene glycol plus ascorbate components versus sodium phosphate for bowel cleansing prior to colonoscopy for cancer screening

BACKGROUND

Colonoscopy requires effective bowel preparation for adequate mucosal visualization. Safety and acceptability of bowel preparation are key components in colorectal cancer screening (CRC) populations.

OBJECTIVE

To compare the efficacy, safety and acceptability of bowel preparation with polyethylene glycol (PEG), ascorbic acid, sodium ascorbate (ascorbate components), sodium sulfate and electrolytes (PEG+Asc) or sodium phosphate (NaP).

METHODS

Consenting adults undergoing elective out-patient colonoscopy for CRC were randomized to take 2 L PEG+Asc or 90 mL NaP (control) following manufacturer's instructions. PEG+Asc was taken the evening before and morning of the colonoscopy; NaP was taken the morning and evening before colonoscopy. Participants followed a restricted diet specific to each preparation. Primary endpoint was bowel cleansing success (100% colon mucosa visible) rated by an independent expert panel (all experienced endoscopists) unaware of treatment allocations. Subject reported outcomes about the preparations were elicited. Adverse events were recorded.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov: NCT00427089.

RESULTS

Successful bowel cleansing rate was significantly higher in the PEG+Asc (N = 242) than the NaP (N = 114) group (PEG+Asc 93.4% [95% CI 89.5-96.2] versus NaP 22.8% [15.5-31.6%], p < 0.0001). Subject reported outcomes on acceptability of the two different preparations were not significantly different (p = 0.238). However, taste ratings for PEG+Asc were significantly better versus NaP (mean VAS: 31.2 and 38.1 respectively, p = 0.0111). The proportion of patients prepared to receive the same preparation again was significantly higher in the PEG+Asc group (88.4% vs. 78.1%, p < 0.0001).

CONCLUSIONS

PEG+Asc provided superior bowel cleansing to NaP and was well tolerated. Findings for PEG+Asc are aligned with previous similar studies; however, differences observed in NaP cleansing results, especially for the proximal colon segments, may be due to factors including: differences in demographics and population types and the use of the validated Harefield Cleansing Scale as an assessment tool combined with expert reviews, which may have resulted in conservative cleansing assessments.

Randomised clinical trial: Polyethylene glycol 3350 with sports drink vs. polyethylene glycol with electrolyte solution as purgatives for colonoscopy--the incidence of hyponatraemia

BACKGROUND

Polyethylene glycol 3350 plus sports drink (PEG-SD) is a hypo-osmotic purgative commonly used for colonoscopy, though little safety data are available.

AIM

To evaluate the effect of PEG-SD on serum sodium (Na) and other electrolytes compared with PEG-electrolyte solution (PEG-ELS).

METHODS

We performed a single center, prospective, randomised, investigator-blind comparison of PEG-ELS to PEG-SD in out-patients undergoing colonoscopy. Laboratories were obtained at baseline and immediately before and after colonoscopy. The primary endpoint was development of hyponatraemia (Na <135 mmol/L) the day of colonoscopy. Changes in electrolyte levels were computed as the difference between the lowest value on the day of colonoscopy and baseline. Purgative tolerance and efficacy were assessed.

RESULTS

A total of 389 patients were randomised; 364 took purgative and had baseline and day of colonoscopy labs (180 PEG-SD, 184 PEG-ELS). The groups were well matched except for a higher fraction of women and Blacks in PEG-ELS. Seven patients (3.9%) in PEG-SD and four patients (2.2%) in PEG-ELS developed hyponatraemia (OR = 1.82, 95% CI: 0.45-8.62, P = 0.376). Changes in electrolytes from baseline were small but significantly worse with PEG-SD for sodium, potassium and chloride (P = 0.001, 0.012, 0.001, respectively). Preparation completion, adverse events, and overall colon cleansing were similar between the groups, but PEG-ELS had more excellent preparations (52% vs. 30%; P = 0.001).

CONCLUSIONS

Greater, but very modest, electrolyte changes occur with PEG-SD. Hyponatraemia is infrequent with both purgatives. A significant increase in hyponatraemia was not identified for PEG-SD vs. PEG-ELS, but the sample size may have been inadequate to identify a small, but clinically important difference. ClinicalTrials.gov identifier NCT01299779.

Colonoscopy preparation-induced disorders in renal function and electrolytes

Colonoscopy and flexible sigmoidoscopy are commonly used mainly for colon cancer screening and detection, but also in several other situations such as inflammatory bowel disease (for diagnosis and follow up) and gastrointestinal hemorrhage. Bowel cleansing preparations mainly include polyethylene glycol and oral sodium phosphate solutions, with the later being most frequently used due to better toleration from patients. Despite their favourable safety profile these agents have been associated with renal function deterioration and electrolyte disorders, some of which were serious or even fatal. The present paper discusses the complications associated with colonoscopy preparation agents.

The modern bowel preparation in colonoscopy

Adequate bowel preparation is essential for optimal colonoscopy. Suboptimal bowel preparation occurs in 25% to 40% of cases and is associated with canceled procedures, prolonged procedure time, incomplete examination, increased cost, and missed pathology. There are several effective formulations for colon cleansing with a good safety profile. Split dosing should be implemented whenever possible in an effort to enhance tolerance and adherence, and improve mucosal visibility and overall quality of the examination. In this review, modern bowel preparations are discussed including their mechanism of action, mode of use, safety, and how to optimize outcomes.

Serious events in older Ontario residents receiving bowel preparations for outpatient colonoscopy with various comorbidity profiles: a descriptive, population-based study

BACKGROUND

Polyethylene glycol-based bowel preparations (PEGBPs) and sodium picosulfate (NaPS) are commonly used for bowel cleansing before colonoscopy. Little is known about adverse events associated with these preparations, particularly in older patients or patients with medical comorbidities.

OBJECTIVE

To characterize the incidence of serious events following outpatient colonoscopy in patients using PEGBPs or NaPS.

METHODS

The present population-based retrospective cohort study examined data from Ontario health care databases between April 1, 2005 and December 31, 2007, including patients >=66 years of age who received either PEGBP or NaPS for an outpatient colonoscopy. Patients with cardiac or renal disease, long-term care residents or patients receiving concurrent diuretic therapy were identified as high risk for adverse events. The primary outcome was a serious event (SE) defined as a composite of nonelective hospitalization, emergency department visit or death within seven days of the colonoscopy.

RESULTS

Of the 50,660 outpatients >=66 years of age who underwent a colonoscopy, SEs were observed in 675 (2.4%) and 543 (2.4%) patients in the PEGBP and NaPS groups, respectively. Among high-risk patients (n=30,168), SEs occurred in 481 (2.8%) and 367 (2.8%) of patients receiving PEGBP and NaPS, respectively.

CONCLUSIONS

The SE rate within seven days of outpatient colonoscopy was 24 per 1000 procedures, and among high-risk patients was 28 per 1000 procedures. The rates were similar for PEGBP and NaPS. Clinicians should be aware of the risks associated with colonoscopy in older patients with comorbidities.

Pros and cons of colonoscopy in management of acute lower gastrointestinal bleeding

Acute lower gastrointestinal bleeding (LGIB) is a frequent gastrointestinal cause of hospitalization, particularly in the elderly, and its incidence appears to be on the rise. Endoscopic and radiographic measures are available for the evaluation and treatment of LGIB including flexible sigmoidoscopy, colonoscopy, angiography, radionuclide scintigraphy and multi-detector row computed tomography. Although no modality has emerged as the gold standard in the management of LGIB, colonoscopy is the current preferred initial test for the majority of the patients presenting with hematochezia felt to be from a colon source. Colonoscopy has the ability to diagnose all sources of bleeding from the colon and, unlike the radiologic modalities, does not require active bleeding at the time of the examination. In addition, therapeutic interventions such as cautery and endoclips can be applied to achieve hemostasis and prevent recurrent bleeding. Studies suggest that colonoscopy, particularly when performed early in the hospitalization, can decrease hospital length of stay, rebleeding and the need for surgery. However, results from available small trials are conflicting and larger, multicenter studies are needed. Compared to other management options, colonoscopy is a safe procedure with complications reported in less than 2% of patients, including those undergoing urgent examinations. The requirement of bowel preparation (typically 4 or more liters of polyethylene glycol), the logistical complexity of coordinating after-hours colonoscopy, and the low prevalence of stigmata of hemorrhage complicate the use of colonoscopy for LGIB, particularly in urgent situations. This review discusses the above advantages and disadvantages of colonoscopy in the management of acute lower gastrointestinal bleeding in further detail.

Colorectal cancer screening and surveillance in the elderly patient

Colorectal cancer (CRC) is the third leading cause of cancer-related deaths in the United States. Older age is associated with a rise in colorectal cancer and adenomas, necessitating the need for CRC screening in older patients. However, decisions about CRC screening and surveillance in older adults are often difficult and challenging. The decision requires an individualized assessment that incorporates factors unique to performing colonoscopy in older adults in order to weigh the risks and benefits for each patient according to their overall health and preferences. This review addresses the factors unique to colorectal cancer and performing colonoscopy in older adults that are relevant in weighing the risks and benefits of screening and surveillance in this population.

Mechanism of action and toxicities of purgatives used for colonoscopy preparation

IMPORTANCE OF THE FIELD

In developed countries, colonoscopy volume has increased dramatically over the past 15 years and is the principle method used to screen for colon cancer. Preparations used for colon cleaning have evolved over the past 30 years. Some preparations have been shown to be unsafe and are now used on a limited basis. There has been progress on limiting the volume required and on taste improvement.

AREAS COVERED IN THIS REVIEW

This review provides an account of preparations used from 1980 when PEG-based preparations became widely available, until the present day. The review highlights their mechanism of action and principle toxicities. The handling of solutes and solute-free fluid by the colon is also reviewed.

WHAT THE READER WILL GAIN

The reader will gain a perspective on the factors considered in developing colonic purgatives and the rationale for choosing selected preparations based on patient factors such as age, co-morbidities and concomitant medications.

TAKE HOME MESSAGE

Although generally safe and effective, colonic purgatives have both acute and permanent toxicities. The safest preparations utilize PEG combined with a balanced electrolyte solution. Limitations of this preparation center on the volume required and poor taste. Alternative formulations are now available; however, those using sodium phosphate have fallen out of favor due to a risk of renal toxicity.

Preoperative bowel preparation for patients undergoing elective colorectal surgery: a clinical practice guideline endorsed by the Canadian Society of Colon and Rectal Surgeons

BACKGROUND

Despite evidence that mechanical bowel preparation (MBP) does not reduce the rate of postoperative complications, many surgeons still use MBP before surgery. We sought to appraise and synthesize the available evidence regarding preoperative bowel preparation in patients undergoing elective colorectal surgery.

METHODS

We searched MEDLINE, EMBASE and Cochrane Databases to identify randomized controlled trials (RCTs) comparing patients who received a bowel preparation with those who did not. Two authors reviewed the abstracts to identify articles for critical appraisal. We used the methods of the United States Preventive Services Task Force to grade study quality and level of evidence, as well as formulate the final recommendations. Outcomes assessed included postoperative infectious complications, such as anastomotic dehiscence and superficial surgical site infections.

RESULTS

Our review identified 14 RCTs and 8 meta-analyses. Based on the quality and content of these original manuscripts, we formulated 6 recommendations for various aspects of bowel preparation in patients undergoing elective colorectal surgery.

CONCLUSION

Taking into account the lack of difference in postoperative infectious complication rates when MBP is omitted and the adverse effects of MBP, we believe that, based on the literature, MBP before surgery should be omitted.

Complications of colonoscopy: magnitude and management

Although complications of colonoscopy are rare, they are potentially serious and life threatening. In addition, less serious adverse events may occur frequently and may have an impact on a patient's willingness to undergo future procedures. This article reviews the magnitude of and risk factors for major and minor colonoscopy complications, discusses management of complications, and suggests ways to design quality improvement programs to reduce the risk of complications.

The safety of osmotically acting cathartics in colonic cleansing

Efficient cleansing of the colon before a colonoscopy or a radiological examination is essential. The osmotically acting cathartics (those given the Anatomical Therapeutic Chemical code A06AD) currently used for this purpose comprise products based on three main substances: sodium phosphate, combinations of polyethylene glycol and electrolyte lavage solutions (PEG-ELS), and magnesium citrate. All these preparations give adequate cleansing results and have similar profiles in terms of the frequency and type of mild to moderate adverse effects. However, serious adverse events, such as severe hyperphosphatemia and irreversible kidney damage owing to acute phosphate nephropathy, have been reported after use of sodium-phosphate-based products. The aim of this Review is to provide an update on the potential safety issues related to the use of osmotically acting cathartics, especially disturbances of renal function and water and electrolyte balance. The available evidence indicates that PEG-ELS-based products are the safest option. Magnesium-citrate-based, hypertonic products should be administered with caution to elderly individuals and patients who are prone to develop disturbances in water and electrolyte balance. Sodium-phosphate-based products can occasionally cause irreversible kidney damage and should not be routinely used in bowel-cleansing procedures.

Hypokalemia following polyethylene glycol-based bowel preparation for colonoscopy in older hospitalized patients with significant comorbidities

BACKGROUND

Polyethylene glycol-based bowel preparations (PEGBPs) are widely perceived as safe and effective alternatives to oral sodium phosphate for bowel cleansing prior to colonoscopy. Most studies supporting this belief involve young patients with few comorbidities.

OBJECTIVE

To characterize the incidence of electrolyte disturbances following PEGBPs administered prior to colonoscopy among elderly inpatients and hypothesize that PEGBP would be associated with hypokalemia in this setting.

METHODS

This retrospective chart review, conducted at 3 tertiary care teaching hospitals in Toronto, Canada, from 2005 to 2007, included 96 consecutive patients aged 65 or older who were admitted to the hospital and given PEGBP prior to their first inpatient colonoscopy. Patients were excluded if they received additional cathartics, underwent colonoscopy while admitted to a critical care unit, or were admitted for a complication arising from an outpatient colonoscopy. The primary outcome was hypokalemia (serum potassium < or =3.2 mEq/L) within 48 hours of PEGBP.

RESULTS

Of 96 patients, 73 had serum electrolytes measured at baseline and within 48 hours following PEGBP administration. Hypokalemia was identified in 4 patients (5.5%) prior to PEGBP and in 15 patients (20.5%) after PEGBP (p < 0.001). The incidence of significant hypokalemia, defined as serum potassium < or =3.0 mEq/L, in this group was 9.6% (p = 0.008). We found consistent results among patients with and without concomitant diuretic treatment.

CONCLUSIONS

Among older patients, administration of PEGBP is commonly complicated by the development of hypokalemia, which is occasionally severe. Monitoring of electrolytes may be necessary following colonoscopy, particularly in patients with cardiac or renal disease.

Bowel preparation in CT colonography: electrolyte and renal function disturbances in the frail and elderly patient

PURPOSE

Elderly patients are at increased risk of biochemical disturbances secondary to cathartic medications. This study investigates the renal function, electrolyte and clinical disturbances associated with CT colonography (CTC) with sodium picosulphate-magnesium citrate (SPS-MC) in a subgroup of frail, elderly patients.

METHODS

Patients aged over 70 years considered at risk of complication during SPS-MC administration by a physician specialised in care of the elderly were included in this retrospective study. Biochemical parameters pre- and post-CTC and the presence of co-morbidities were recorded. Imaging findings and quality of bowel preparation at CTC were graded by consensus by two radiologists.

RESULTS

Of the 72 patients 56% had co-morbidities that caution the use of SPS-MC. No significant changes in serum urea, sodium, potassium or estimated glomerular filtration rate (eGFR) occurred post-CTC (p > 0.10). Serum magnesium increased by 0.11 mmol/L in 14 patients (p = 0.03) without clinical sequelae. Good overall preparation was achieved in 88% of patients, allowing confident identification of signs of colonic neoplasia in 20 patients (27%). A mild increase in serum magnesium but no other significant biochemical disturbance was observed.

CONCLUSION

In our group CTC with SPS-MC was safe and effective; however, we advise an alternate preparation be considered in patients with decreased renal function due to decreased magnesium clearance.

The potential significance of elevated vitreous sodium levels at autopsy

Elevated levels of sodium that may be detected in the analysis of post-mortem fluid samples may arise from a wide variety of organic illnesses and environmental factors that have caused either water depletion or solute gain. When hypernatraemia is suspected at autopsy a careful history is required with particular emphasis on pre-existing medical conditions such as renal or gastrointestinal disease. In addition, detailed information is required on the circumstances of death, including any clinical symptoms and signs that the deceased may have manifested, or medical procedures such as dialysis, colonoscopy or intravenous fluid replacement. Reduced intake of fluid may be associated with cognitive or physical impairment or may result from environmental depletion (the latter may be a manifestation of inflicted injury). Both central and nephrogenic diabetes insipidus may result in the loss of excessive amounts of hypotonic fluid. This may also occur following diuretic use, or be due to gastroenteritis or burns. Hypernatraemia may be a marker of excessive salt/saline ingestion and/or administration and may occur accidentally or as a manifestation of child abuse. Given the range of possible etiologies, hypernatraemia may be a significant autopsy finding that requires explanation.

Bowel preparations for colonoscopy: a review

PURPOSE

The mechanisms of action, clinical efficacy, tolerability, and safety of two major classes of bowel purgatives, poly-ethylene glycol- electrolyte lavage solutions (PEG-ELSs) and sodium phosphate preparations, are reviewed.

SUMMARY

PEG-ELSs are osmotically balanced preparations that promote bowel cleansing through the ingestion of nonabsorbable fluid. Sodium phosphate preparations are hyperosmotic purgatives that promote bowel cleansing by osmotically drawing fluid into the bowel lumen for evacuation. Studies suggest that 2-L PEG-ELS regimens are generally as effective as and more tolerable than full-volume PEG-ELS preparations. Studies have also found that sodium phosphate tablets may provide a more tolerable alternative to PEG-ELS regimens and traditional sodium phosphate products without compromising bowel cleansing efficacy. Proper renal function plays a particularly important role in avoiding potential safety issues related to sodium phosphate-induced shifts in the fluid and electrolyte balance. Preventing dehydration in patients undergoing bowel preparation can prevent severe adverse events, regardless of the purgative administered. Optimizing the process of bowel preparation involves administering proper purgative choices in appropriate patient populations. Moreover, patient education and compliance with preparation instructions, including correct dosing and adequate hydration, may reduce the risk of adverse events and serious complications.

CONCLUSION

Although next-generation PEG-ELS and sodium phosphate products are well tolerated and preferred by patients over traditional bowel preparation regimens, safety issues remain a concern for both purgative classes. Sodium phosphate preparations are generally more effective and better tolerated than PEG-ELS formulations but should be administered with caution in patients with preexisting or at an increased risk for electrolyte disturbances.

Systematic review: adverse event reports for oral sodium phosphate and polyethylene glycol

BACKGROUND

Screening colonoscopy exposes healthy patients to the risk of serious adverse events associated with bowel preparation. Randomized controlled trials are not an effective method for evaluating this risk.

AIM

To search published literature in order to characterize the risk of adverse events associated with oral polyethylene glycol (PEG) or sodium phosphate (NaP).

METHODS

A systematic review identified case reports of any serious events associated with PEG or NaP. Reports to the Food and Drug Administration (FDA) were also examined.

RESULTS

Fifty-eight publications of significant events in 109 patients using NaP and 22 patients using PEG were identified. As the total number of prescriptions issued is unknown, rates for the two agents cannot be directly compared. Most commonly reported were electrolyte disturbances, renal failure and colonic ulceration for NaP and Mallory-Weiss tear, electrolyte disturbances and allergic reactions for PEG between January 2006 and December 2007; there were 171 cases of renal failure reported to the FDA following use of NaP and 10 following PEG.

CONCLUSIONS

Adverse events following bowel preparation are uncommon, but potentially serious. Given that many of these patients are healthy individuals undergoing screening, the benefit/risk ratio must be carefully considered when deciding which preparation to prescribe in individual patients.

Adverse renal and metabolic effects associated with oral sodium phosphate bowel preparation

Colorectal cancer can be prevented by the removal of adenomatous polyps during screening colonoscopy, but adequate bowel preparation is required. Oral sodium phosphate (OSP), an effective bowel purgative, is available over the counter and requires a substantially lower volume than polyethylene glycol-based preparative agents. Accumulating reports implicate OSP in electrolyte disturbances as well as acute kidney injury (AKI) in a syndrome termed phosphate nephropathy (a form of nephrocalcinosis). Despite published case reports and case series, the actual incidence, risk factors, and natural history of phosphate nephropathy remain largely undefined. Several recent observational studies have provided new information on these important issues while supporting a link between OSP and acute phosphate nephropathy as well as the development of chronic kidney disease in elderly patients, many of whom had a normal serum creatinine at the time of OSP ingestion. This review summarizes current knowledge about the renal complications of OSP, risk factors for its development, and the pathophysiology of acute and chronic kidney damage in nephrocalcinosis.

Key safety issues of bowel preparations for colonoscopy and importance of adequate hydration

Although screening colonoscopy is effective for early detection of colorectal cancer, screening rates remain low. Multiple factors are thought to be responsible for the low rates of screening colonoscopy, but bowel preparation appears to be a key deterrent. Tolerability issues with bowel preparations may lead to poor patient compliance, inadequate colon cleansing, and reduced detection of colonic polyps. Successful colon cleansing requires careful selection of the appropriate bowel purgative regimen, as well as patient acceptance of and compliance with the chosen regimen. The two major classes of bowel preparations include polyethylene glycol solutions and sodium phosphate preparations. Patient preference for tablet versus liquid formulations and medical history (e.g., renal impairment) should be considered when choosing the appropriate bowel preparation. Regardless of the bowel preparation administered, adequate hydration is important before, during, and after bowel preparation. Appropriate patient education regarding hydration and individualized patient instructions may increase compliance, reduce adverse events, promote successful bowel preparation for colonoscopy, and enhance the probability of a quality exam.

Review article: Bowel preparation for colonoscopy--the importance of adequate hydration

BACKGROUND

Patient compliance with screening recommendations for colorectal cancer remains low, despite a 90% survival rate achieved with early detection. Bowel preparation is a major deterrent for patients undergoing screening colonoscopy. More than half of patients taking polyethylene glycol electrolyte lavage solution and sodium phosphate preparations experience adverse events, such as nausea and abdominal pain. Many adverse events may be associated with dehydration, including rare reports of renal toxicity in patients taking sodium phosphate products. Addressing dehydration-related safety issues through patient screening and education may improve acceptance of bowel preparations, promote compliance and increase the likelihood of a successful procedure.

AIM

To evidence safety issues associated with bowel preparation are generally related to inadequate hydration.

RESULTS

Dehydration-related complications may be avoided through proper patient screening, for example, renal function and comorbid conditions should be considered when choosing an appropriate bowel preparation. In addition, patient education regarding the importance of maintaining adequate hydration before, during and after bowel preparation may promote compliance with fluid volume recommendations and reduce the risk of dehydration-related adverse events.

CONCLUSIONS

Proper patient screening and rigorous attention by patients and healthcare providers to hydration during bowel preparation may provide a safer, more effective screening colonoscopy.

Novel risk factors for hospital-acquired hyponatraemia: a matched case-control study

BACKGROUND

Hospital-acquired hyponatraemia is a common and potentially serious condition. Risk factors for hospital-acquired hyponatraemia have not been studied in a controlled fashion. Methods From 1501 patients in whom serum sodium (S(Na)) was determined, 50 cases with hospital-acquired hyponatraemia (in-hospital decrease in S(Na)>or= 7 mmol/l to < 136 mmol/l) were identified. They were matched by age, gender and department to 69 normonatraemic controls.

RESULTS

In the 50 cases, S(Na) fell from 141 +/- 2 to 130 +/- 4 mmol/l, while controls remained normonatraemic. During the development of hyponatraemia, C-reactive protein (CRP) increased in cases (median from 23 to 146 mg/l), whereas it decreased in controls (median from 31 to 24 mg/l, P = 0.008). Additional factors associated with hospital-acquired hyponatraemia included diabetes mellitus (16/50 vs. 10/69, P = 0.009) and the use of insulin (12/50 vs. 4/69, P = 0.007), antibiotics (41/50 vs. 38/69, P = 0.006) and opioids (32/50 vs. 27/69, P = 0.005). Multivariate conditional logistic regression showed that the use of insulin [odds ratio (OR) 10.5, 95% confidence interval (CI) 1.5-72.4], antibiotics (OR 4.5, 95% CI 1.4-14.6) and opioids (OR 2.9, 95% CI 1.1-7.8) was also independently associated with hospital-acquired hyponatraemia. Mortality (6/50 vs. 1/69, P = 0.04) and intensive care admission (15/50 vs. 7/69, P = 0.008) were higher in cases.

CONCLUSIONS

An increase in CRP and the use of insulin, antibiotics and opioids are novel risk factors for hospital-acquired hyponatraemia. These factors represent interesting new clues regarding the pathophysiology of hospital-acquired hyponatraemia, suggesting that the acute-phase response, pain and/or direct drug effects could be involved in the release of antidiuretic hormone.

Systematic review: oral bowel preparation for colonoscopy

BACKGROUND

There are many published trials of colon cleansing regimens for colonoscopy but no clear consensus regarding relative performance.

AIM

To identify high quality controlled trials comparing two or more bowel preparation regimens and to compare efficacy and tolerability.

METHODS

A comprehensive systematic review was carried out to identify candidate studies. Quality appraisal was carried out on all identified studies. Results were meta-analysed where possible and qualitatively compared if not.

RESULTS

Eighty-two studies qualified for analysis. Polyethylene glycol and sodium phosphate were the most frequently investigated preparations. There was no significant efficacy difference between the two, but sodium phosphate was better tolerated. Sodium picosulphate/magnesium citrate, a commonly prescribed preparation, was investigated in four studies, with no clear benefit over other regimens demonstrated. Safety was not recognized as a problem in the randomized controlled trials. Published case series demonstrate that sodium phosphate is associated with the highest risk of clinically significant electrolyte disturbances.

CONCLUSION

Shortcomings in study design limit the value of many of the studies. Based on these results, no single bowel preparation emerges as consistently superior. New preparations are required that combine better efficacy and tolerability, in addition to rigorous new validated study designs, allowing unequivocal comparisons to be made.

Commonly used preparations for colonoscopy: efficacy, tolerability, and safety--a Canadian Association of Gastroenterology position paper

INTRODUCTION

The increased demand for colonoscopy, coupled with the introduction of new bowel cleansing preparations and recent caution advisories in Canada, has prompted a review of bowel preparations by the Canadian Association of Gastroenterology.

METHODS

The present review was conducted by the Clinical Affairs group of committees including the endoscopy, hepatobiliary/transplant, liaison, pediatrics, practice affairs and regional representation committees, along with the assistance of Canadian experts in the field. An effort was made to systematically assess randomized prospective trials evaluating commonly used bowel cleansing preparations in Canada.

RESULTS

Polyethylene glycol (PEG)-; sodium phosphate (NaP)-; magnesium citrate (Mg-citrate)-; and sodium picosulphate, citric acid and magnesium oxide (PSMC)-containing preparations were reviewed. Regimens of PEG 2 L with bisacodyl (10 mg to 20 mg) or Mg-citrate (296 mL) are as effective as standard PEG 4 L regimens, but are better tolerated. NaP preparations appear more effective and better tolerated than standard PEG solutions. PSMC has good efficacy and tolerability but head-to-head trials with NaP solutions remain few, and conclusions equivocal. Adequate hydration during preparation and up to the time of colonoscopy is critical in minimizing side effects and improving bowel cleansing in patients receiving NaP and PSMC preparations. All preparations may cause adverse events, including rare, serious outcomes. NaP should not be used in patients with cardiac or renal dysfunction (PEG solution is preferable in these patients), bowel obstruction or ascites, and caution should be exercised when used in patients with pre-existing electrolyte disturbances, those taking medications that may affect electrolyte levels and elderly or debilitated patients. Health Canada's recommended NaP dosing for most patients is two 45 mL doses 24 h apart. However, both safety and efficacy data on this dosing schedule are lacking. Many members of the Canadian Association of Gastroenterology expert panel administer both doses within 24 h, as studied in clinical trials, after careful one-on-one discussion of risks and benefits in carefully selected patients. Safety data on PSMC and combination preparations in North America are limited and clinicians are encouraged to keep abreast of developments in this area.

CONCLUSIONS

All four preparations reviewed provided effective bowel cleansing for colonoscopy in the majority of patients, with varying tolerability. Adequate hydration is essential in patients receiving the preparations.

Dysnatremias: Why Are Patients Still Dying?

Dysnatremias are a common clinical entity that are often associated with poor outcomes. This review takes a case study approach to understand how dysnatremias can result in devastating neurologic consequences. Concrete guidelines are provided for prevention, early recognition and treatment along with a discussion of how urinary electrolytes and osmolality can be used to guide therapy. Case studies in hyponatremic encephalopathy include the post-operative state, thiazide diuretics, extreme exercise and DDAVP use. Reasons to avoid using hypotonic parenteral fluids, risk factors for hyponatremic encephalopathy such as age, gender, and hypoxia, and the appropriate use of 3% sodium chloride are discussed. Case studies in hypernatremia include hypernatremia in the ICU setting and the emerging condition of breastfeeding-associated hypernatremia in infants.

Biochemical and etiological characteristics of acute hyponatremia in the emergency department

Hyponatremia can be classified as acute or chronic depending on its duration, and treatment options are tailored to this classification. However, it is sometimes difficult to differentiate acute from chronic hyponatremia in the Emergency Department (ED). The objective of this study was to identify characteristics to help diagnose and manage acute hyponatremia in the ED. Patients with acute hyponatremia in the ED were enrolled from a retrospective 2-year chart review. Eleven patients (0.8%) were identified with acute hyponatremia out of a total of 1321 hyponatremic patients. There were nine women and two men. The mean age was 48.9 years. The mean sodium (Na(+)) level was 115+/-4 mmol/L. Accompanying biochemical abnormalities included hypouricemia and hypouremia with increased fractional excretions of uric acid (UA) and urea. The estimated amount of water intake ranged from 2.5 to 10 liters (mean, 5.1+/-2.3 liters) during the day before ED presentation. All patients were treated with hypertonic saline and furosemide at a correction rate of 1.6+/-0.5 mmol/L/h. No patients had neurological sequelae after treatment. The causes of acute hyponatremia included induction of abortion with oxytocin (n=1), primary polydipsia on neuroleptic agents (n=2), polyethylene glycol (PEG) preparation for colonoscopy (n=1), diuretic therapy for hypertension (n=4), ecstasy use (n=1), and weight-reducing herbal teas (n=2). We conclude that in the right clinical setting, high free water intake and low serum urea and UA favor acute hyponatremia. A detailed drug history may be helpful in the differential diagnosis of acute hyponatremia.

Measurement of serum electrolytes and phosphate after sodium phosphate colonoscopy bowel preparation: an evaluation

Our purpose was to observe the effects of sodium phosphate (NaP) colonoscopy preparation on serum electrolytes, phosphate, and calcium and to identify factors associated with any adverse effects. In an unselected group of 100 consecutive patients attending for out patient colonoscopy, 45% of patients had raised serum phosphate, which was positively correlated with creatinine and age. There was a negative association of phosphate with calcium; 16% of patients had hypocalcemia and 26% had hypokalemia. Patients taking ACE inhibitors, AT2 antagonists, or diuretics were associated with hyperphosphatemia. Significant electrolyte and metabolic disturbance from colonoscopy preparation has been shown with NaP preparation, without overt clinical effects. We recommend that elderly patients and those with significant comorbidity have their electrolytes and calcium measured, and diuretics and ACE inhibitors stopped, before NaP administration. Endoscopy units should be alert for patients who might be suffering from electrolyte disturbance postpreparation and be prepared to measure their electrolytes.

Colonoscopy in the very old: why bother?

OBJECTIVES

To evaluate the use of colonoscopy in patients aged at least 85 years. Does the ideal of an ageism free service apply?

DESIGN

A retrospective audit.

SETTING

Department of gastroenterology that carries out about 1000 colonoscopies annually in a district general hospital serving a population of about 320 000.

SUBJECTS

All patients aged at least 85 years who underwent colonoscopy over five years to 2003.

MAIN OUTCOME MEASURES

The indications for colonoscopy and its findings. The outcome of patients found to have colonic cancers.

RESULTS

Colonoscopy was completed in 219 cases (69%). The main reasons for failure were poor bowel preparation and severe diverticular disease. Normal findings occurred in 65 (30%) of the 219 cases that had had a complete examination. Colonoscopy identified a problem that explained the patient's symptoms in 116 (37%) cases. Polyps were found in 45 (14.2%) cases and malignancy in 28 (8.8%).

CONCLUSIONS

The absence of significant complications and comparatively high yield of colonic malignancies and polyps reinforces the value of colonoscopy as a diagnostic tool even after 85 years of age and despite the technical challenges of the procedure in this age group that limited completion. Increasing age alone should not preclude a patient from colonoscopy.