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Nil per os

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Bright Attah Addae
Bright Attah Addae

The document discusses preoperative fasting guidelines and the risks of pulmonary aspiration during surgery. It summarizes a study that compared gastric fluid volume and pH in patients who either fasted overnight or drank 150mL of water 2 hours before surgery. The study found that patients who drank the water had significantly lower gastric fluid volumes (5.5mL vs 17.1mL) after surgery, but similar pH levels. This suggests that allowing clear fluids like water 2 hours before surgery may be safe and help reduce patient discomfort from long fasting times.

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Nil per os From Wikipedia, the free encyclopedia Jump to: navigation, search Nil per os (alternatively nihil/non/nulla per os) (NPO) is a medical instruction meaning to withhold oral food and fluids from a patient for various reasons. It is a Latin phrase which translates as "nothing through the mouth". In the United Kingdom, it is translated as nil by mouth (NBM). Typical reasons for NPO instructions are the prevention of aspiration pneumonia, e.g. in those who will undergo general anesthetic, or those with weak swallowing musculature, or in case of gastrointestinal bleeding, gastrointestinal blockage, or acute pancreatitis. Alcohol overdoses that result in vomiting or severe external bleeding also warrants NPO instructions for a period. When patients are placed on NPO orders prior to surgical general anesthesia, physicians would usually add the exception that patients are allowed a very small drink of water to take with their usual medication. This is the only exception to a patient's pre-surgery NPO status. Otherwise, if a patient accidentally ingested some food or water, the surgery would usually be canceled or postponed for at least 8 hours. Preoperative fasting From Wikipedia, the free encyclopedia Jump to: navigation, search Preoperative fasting is the practice of a patient abstaining from oral food and fluid intake for a time before an operation is performed. This is intended to prevent pulmonary aspiration of stomach contents during general anesthesia.[1] Pulmonary aspiration The main reason for preoperative fasting is to prevent pulmonary aspiration of stomach contents while under the effects of general anesthesia. Aspiration of as little as 30-40ml can be a significant cause of suffering and death during an operation and therefore fasting is performed to reduce the volume of stomach contents as much as possible. Several factors can predispose to aspiration of stomach contents including inadequate anesthesia, pregnancy, obesity, difficult airways, emergency surgery (since fasting time is reduced), full stomach and altered gastrointestinal mobility. Increased fasting times leads to decreased injury if aspiration occurs.[1] Gastric conditions In addition to fasting, antacids are administered the night before (or in the morning of an afternoon operation) and then once again two hours prior to surgery. This is to increase the pH (make more neutral) of the acid present in the stomach, helping to reduce the damage caused by
pulmonary aspiration, should it occur. H2 receptor blockers should be used in high-risk situations and should be administered in the same timing intervals as antacids.[1] Gastroparesis (delayed gastric emptying) may occur and is due to metabolic causes (e.g. poorly controlled diabetes mellitus), decreased gastric motility (e.g. due to head injury) or pyloric obstruction (e.g. pyloric stenosis). Delayed gastric emptying usually only affects the emptying of the stomach of high-cellulose foods such as vegetables. Gastric emptying of clear fluids such as water or black coffee is only affected in highly progressed delayed gastric emptying.[1] Occasionally, gastroesophageal reflux may be associated with delayed gastric emptying of solids, but clear liquids are not affected. Raised intra-abdominal pressure (e.g. in pregnancy or obesity) predisposes to regurgitation. Certain drugs such as opiates can cause marked delays in gastric emptying, as can trauma which can be determined by certain indicators such as normal bowel sounds and patient hunger.[1] Minimum fasting times The minimum fasting times prior to surgery have long been debated. The first proposition came from British anesthetists stating that patients should be nil by mouth from midnight.[2] However, since then, the American Society of Anesthesiologists (ASA), followed by the Association of Anaesthestists of Great Britain and Ireland (AAGBI), recommended new fasting guidelines for the minimum fast prior to surgery.[1] This was based upon evidence by Canadian anesthesiologists who found that drinking clear fluids two hours prior to surgery decreased pulmonary aspiration compared to those nil by mouth since midnight.[2] The following are the recommended guidelines for nil by mouth prior to surgery:[3] Age Solids Clear liquids <6 months 4 hours 2 hours 6–36 months 6 hours 3 hours >36 months (including adults) 6 hours 2 hours When anaesthesia is required in an emergency situation, nasogastric aspiration is usually performed to reduce gastric contents and the risk of its pulmonary aspiration.[4]
See also Fasting Surgery General anesthesia References 1. ^ Jump up to: a b c d e f Allman, Keith G.; Iain H. Wilson (2006). Oxford Handbook of Anaesthesia, 2nd edition. Oxford University Press. ISBN 0-19-856609-0 Check |isbn= value (help). 2. ^ Jump up to: a b Maltby JR (April 2006). "Preoperative fasting guidelines". Can J Surg 49 (2): 138–9; author reply 139. PMID 16630428. Retrieved 2008-08-20. 3. Jump up ^ Coté CJ (July 1999). "Preoperative preparation and premedication". Br J Anaesth 83 (1): 16–28. PMID 10616330. Retrieved 2008-08-20. 4. Jump up ^ Legal review of need to place NG tube 2. Indian J Anaesth. 2010 Sep-Oct; 54(5): 445–447. 3. doi: 10.4103/0019-5049.71044 4. PMCID: PMC2991655 “Nil per oral after midnight”: Is it necessary for clear fluids? Kajal S Dalal, Dhanwanti Rajwade, and Ragini Suchak Author information ► Copyright and License information ► Go to: Abstract Fasting before general anaesthesia aims to reduce the volume and acidity of stomach contents, thus reducing the risk of regurgitation and aspiration. Recent guidelines have recommended a shift in fasting policies from the standard ‘nil per oral from midnight’ to a more relaxed policy of clear fluid intake a few hours before surgery. The effect of preoperative oral administration of 150 ml of water 2 h prior to surgery was studied prospectively in 100 ASA I and II patients, for elective surgery. Patients were randomly assigned to two groups. Group I (n = 50) was fasting overnight while Group II (n = 50) was given 150 ml of water 2 h prior to surgery. A nasogastric tube was inserted after intubation and gastric aspirate was collected for volume and pH. The gastric fluid volume was found to be lesser in Group II (5.5 ± 3.70 ml) than Group I (17.1 ± 8.2 ml) which was statistically significant. The mean pH values for both groups were similar. Hence, we conclude that patients not at risk for aspiration can be allowed to ingest 150 ml water 2 h prior to surgery.
Keywords: Clear fluids, preoperative fasting, pulmonary aspiration, stomach contents - pH, volume Go to: INTRODUCTION Long fasting hours prior to surgery is a great discomfort to the patient. Despite recent guidelines stating that it is appropriate to reduce the interval of clear fluid ingestion to 2 h prior to surgery,[1] it is common practice to follow “nothing by mouth” or Nulla per os (NPO) after midnight for both solids as well as clear fluids. Decreasing the fasting period enhances the quality and efficiency of anaesthesia care by decreasing the cost, increasing the patient satisfaction and avoiding delays and cancellations. Also there is a decrease in the risk of dehydration and hypoglycaemia and thereby decrease in the perioperative morbidity. Previous studies have shown that pH< 2 and volume of gastric aspirate > 25 ml (0.4 ml/kg) predispose a patient to pulmonary aspiration,[2] hence a strict overnight fasting regimen was instituted. However, the cochrane database has reviewed several studies showing that prolonged withholding of oral fluids does not improve gastric pH or volume, and permitting a patient to drink fluids preoperatively may even result in significantly lower gastric fluid volumes.[3] In an attempt to reduce the fasting hours of a patient preoperatively without increasing the risk of pulmonary aspiration, we decided to assess the safety of ingestion of 150 ml of water 2 h prior to surgery in patients undergoing general anaesthesia with endotracheal intubation. Go to: METHODS After Ethics Committee approval with written informed consent, 100 ASA I and II patients between 12 and 60 years of age, posted for elective orthopaedic, gynaecological, otolaryngological and general surgery were divided into two groups. Emergency surgeries, patients with history of acid peptic disease, anticipated difficult intubation, diabetes mellitus, obesity, pregnancy, hiatus hernia[4] as well as those routinely taking any medications that affected gastric motility or secretion were excluded from the study. Group I was kept fasting overnight whereas Group II was given 150 ml water 2 h prior to surgery. Patients were premedicated with midazolam and pentazocine, and general anaesthesia was induced using intravenous thiopentone sodium followed by vecuronium. An 18 G and 16 G Ryle’s tube was inserted in male and female patients, respectively after intubation and its position was confirmed by auscultation over the epigastrium for insufflated air. Gastric aspirate was obtained through a 20 ml syringe with the patient supine with an assistant massaging the upper abdomen, as well as with various other positions like Trendelenburg, left lateral and right lateral positions to facilitate maximal aspiration.
Volume of aspirate was noted and pH measured using a standardized pH strip. Sex, age, weight, type of surgery, duration of fasting and interval between ingestion of water and surgery was documented. Results were given as mean ± SD. Data collected were analysed using Student’s t-test. Differences were considered statistically significant if P values were <0.05. Go to: RESULTS There was no significant difference between the groups with regard to weight, age and sex. Patients who were kept fasting overnight (Group I) had an average fasting time of 12 h. The ingestion - surgery interval for Group II was on an average 2 h [Table 1]. Table 1 Patient demographics Patients who had 150 ml of water (Group II) had lesser volume of gastric aspirate (5.5 ± 3.70 ml) than that of Group I (17.1 ± 8.21 ml) which was statistically significant [Table 2]. The pH was found to be in the same range for both the groups (Group I: 1.7 ± 0.28, Group II: 1.6 ± 0.26) [Table 2]. Patients at high risk i.e. gastric fluid volume > 25 ml and pH <2.5 are shown in Table 3. Group I had four patients with a combination of both risk factors, while none were present in Group II. Table 2 Comparison of volume and pH of gastric fluid in both groups
Table 3 Incidence of risk factors Go to: DISCUSSION Pulmonary aspiration of gastric contents during anaesthesia though a rare event,[5] with an incidence of 1 in 7,000 to 8,000 in ASA I and II patients, and 1 in 400 ASA III to V patients,[6] is still considered a significant cause of anaesthesia-related deaths. The severity of pulmonary damage is related to both the volume and pH of the gastric fluid. A combination of volume > 25 ml and pH < 2.5 is considered lethal.[2] Hence any safety measure that reduces this hazard is preferred, so the routine preoperative practice of “nothing by mouth after midnight” is followed. But unfortunately, the ‘nil per oral’ order is blindly applied to both liquids and solids and has become engrained in our anaesthetic practice.[7] The time required for solid food to liquefy and enter the small intestine depends on the type of food ingested (being shorter for carbohydrates and proteins than for fats and cellulose) and the food particle size.[8] Complete emptying of solids from the stomach takes 3 to 6 h, but may be prolonged by fear, pain or opioids.[9] So it is appropriate that no solid food be eaten on the day of surgery. However, the gastro-oesophageal emptying of liquids is rapid wherein studies have shown that gastric emptying after intake of a carbohydrate drink is complete within 2 h of ingestion.[10] At the time of induction of anaesthesia, gastric fluid volume is quite variable in normal people. Even if the patient is fasting, the stomach is not totally empty. On an average, 25 ml to 35 ml of gastric fluid remains in the stomach.[6] Comparing this to the traditional cut-off of gastric fluid volume >25 ml and pH < 2.5, 30-60% patients would be at a risk of pulmonary aspiration, but on an average, the incidence is as low as 1 in 3000.[11] Passive regurgitation of gastric contents can occur only if intragastric pressure exceeds the protective tone of the lower oesophageal sphincter, and for pulmonary aspiration to occur, the protective airway reflexes must also be abolished.[6] Our study was undertaken to determine whether a 2 h fast with clear fluids was safe for patients. Clear fluids would include black tea, coffee, water, carbonated drinks and fruit juices without any particulate matter.[12] We chose 150 ml of water to be given 2 h prior to surgery. We used a Ryle’s tube for aspiration of gastric contents which is a well accepted method for assessment.[5,6,13,14] Our study confirmed the results of previous studies[3,5,6] that even after 11-13 h of fasting, a large number of patients had gastric pH < 2.5 and gastric fluid volume >25 ml.
Patients who received 150 ml water actually had decreased gastric fluid volume which was statistically significant as seen in another study.[3] The pH remained unaffected, thereby not increasing the risk of pulmonary complications due to aspiration. Studies have also shown that giving clear fluids increased patient comfort, decreased anxiety and thirst.[10,15] We conclude that it is safe to conduct general anaesthesia in patients who have ingested 150 ml of water 2 h prior to surgery. Prolonged withholding of oral fluid does not decrease gastric fluid volume and pH. Clinicians should appraise this evidence and adopt the recent ASA guidelines which recommend an evolution from the indiscriminate ‘NPO after midnight’ blanket fasting policy. However, the customary 8 h fasting should be followed for patients at a higher risk of aspiration like in diabetes mellitus, pregnancy, obesity, etc. as more research is necessary to determine the safety in these patients. The risk of unexpected regurgitation cannot be avoided even by overnight fasting, and anaesthesiologists must always be prepared to deal with these complications. Go to: Footnotes Source of Support: Nil Conflict of Interest: None declared. Go to: REFERENCES 1. Practice guidelines for preoperative fasting and the use of pharmacological agents to reduce the risk of pulmonary aspiration: Application to healthy patients undergoing elective procedures. Anesthesiology. 1999;90:898–905. [PubMed] 2. Mendelson CL. The aspiration of stomach contents into the lungs during obstetric anaesthesia. Am J Obstet Gynecol. 1946;52:191–205. [PubMed] 3. Brady M, Kinn S, Stuart P. Preoperative fasting for adults to prevent perioperative complications. Cochrane Database Syst Rev. 2003;4:CD004423. [PubMed] 4. Asai T. Editorial II. Who is at increased risk of pulmonary aspiration? Br J Anaesth. 2004;93:497–500. [PubMed] 5. Cook-Sather SD, Gallagher PR, Kruge LE, Beus JM, Ciampa BP, Welch KC, et al. overweight/obesity and gastric fluid characteristics in pediatric day surgery: implications for fasting guidelines and pulmonary aspiration risk. Anesth Analg. 2009;109:727–36. [PubMed] 6. Maltby JR, Pytka S, Watson NC, Cowan RA, Fick GH. Drinking 300ml of clear fluid 2 hours before surgery has no effect on gastric fluid volume and pH in fasting and non-fasting obese patients. Can J Anaesth. 2004;51:111–5. [PubMed]
7. Wachtel R, Dexter F. A Simple Method for deciding when patients should be ready on the day of surgery without procedure-specific data. Anesth Analg. 2007;105:127–40. [PubMed] 8. Pandit SK, Loberg KW, Pandit UA. Toast and tea before elective surgery? Anesth Analg. 2000;90:1348–51. [PubMed] 9. Scarr M, Maltby JR, Jani K, Sutherland L. Volume and acidity of residual gastric fluid after oral fluid ingestion for elective ambulatory surgery. CMAJ. 1989;141:1151–4. [PMC free article] [PubMed] 10. De Aguilar-Nascimento JE, Borges Dock-Nascimento D. Reducing preoperative fasting time: A trend based on evidence. World J Gastrointest Surg. 2010;2:57–60. [PMC free article] [PubMed] 11. Schreiner MS. Gastric Fluid Volume: Is it really a risk factor for pulmonary aspiration? Anesth Analg. 1998;87:754–6. [PubMed] 12. Pandit SK, Loberg KW, Pandit UA. Coffee is not a clear fluid. Anesth Analg. 2000;91:1306–13. 13. Goldstein H, Boyd JD. The saline load test- a bedside evaluation of gastric retention. Gastroenterology. 1965;49:375–80. [PubMed] 14. Hardy JF. Large volume gastro-oesophageal reflux: a rationale for risk reduction in the perioperative period. Can J Anesth. 1988;35:162–73. [PubMed] 15. Wong CA, MacCarthy RJ, Fitzgerald PC, Raikoff K, Avram MJ. Gastric emptying of water in obese pregnant women at term. Anesth Analg. 2007;105:751–5. [PubMed]

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Nil per os

  • 1. Nil per os From Wikipedia, the free encyclopedia Jump to: navigation, search Nil per os (alternatively nihil/non/nulla per os) (NPO) is a medical instruction meaning to withhold oral food and fluids from a patient for various reasons. It is a Latin phrase which translates as "nothing through the mouth". In the United Kingdom, it is translated as nil by mouth (NBM). Typical reasons for NPO instructions are the prevention of aspiration pneumonia, e.g. in those who will undergo general anesthetic, or those with weak swallowing musculature, or in case of gastrointestinal bleeding, gastrointestinal blockage, or acute pancreatitis. Alcohol overdoses that result in vomiting or severe external bleeding also warrants NPO instructions for a period. When patients are placed on NPO orders prior to surgical general anesthesia, physicians would usually add the exception that patients are allowed a very small drink of water to take with their usual medication. This is the only exception to a patient's pre-surgery NPO status. Otherwise, if a patient accidentally ingested some food or water, the surgery would usually be canceled or postponed for at least 8 hours. Preoperative fasting From Wikipedia, the free encyclopedia Jump to: navigation, search Preoperative fasting is the practice of a patient abstaining from oral food and fluid intake for a time before an operation is performed. This is intended to prevent pulmonary aspiration of stomach contents during general anesthesia.[1] Pulmonary aspiration The main reason for preoperative fasting is to prevent pulmonary aspiration of stomach contents while under the effects of general anesthesia. Aspiration of as little as 30-40ml can be a significant cause of suffering and death during an operation and therefore fasting is performed to reduce the volume of stomach contents as much as possible. Several factors can predispose to aspiration of stomach contents including inadequate anesthesia, pregnancy, obesity, difficult airways, emergency surgery (since fasting time is reduced), full stomach and altered gastrointestinal mobility. Increased fasting times leads to decreased injury if aspiration occurs.[1] Gastric conditions In addition to fasting, antacids are administered the night before (or in the morning of an afternoon operation) and then once again two hours prior to surgery. This is to increase the pH (make more neutral) of the acid present in the stomach, helping to reduce the damage caused by
  • 2. pulmonary aspiration, should it occur. H2 receptor blockers should be used in high-risk situations and should be administered in the same timing intervals as antacids.[1] Gastroparesis (delayed gastric emptying) may occur and is due to metabolic causes (e.g. poorly controlled diabetes mellitus), decreased gastric motility (e.g. due to head injury) or pyloric obstruction (e.g. pyloric stenosis). Delayed gastric emptying usually only affects the emptying of the stomach of high-cellulose foods such as vegetables. Gastric emptying of clear fluids such as water or black coffee is only affected in highly progressed delayed gastric emptying.[1] Occasionally, gastroesophageal reflux may be associated with delayed gastric emptying of solids, but clear liquids are not affected. Raised intra-abdominal pressure (e.g. in pregnancy or obesity) predisposes to regurgitation. Certain drugs such as opiates can cause marked delays in gastric emptying, as can trauma which can be determined by certain indicators such as normal bowel sounds and patient hunger.[1] Minimum fasting times The minimum fasting times prior to surgery have long been debated. The first proposition came from British anesthetists stating that patients should be nil by mouth from midnight.[2] However, since then, the American Society of Anesthesiologists (ASA), followed by the Association of Anaesthestists of Great Britain and Ireland (AAGBI), recommended new fasting guidelines for the minimum fast prior to surgery.[1] This was based upon evidence by Canadian anesthesiologists who found that drinking clear fluids two hours prior to surgery decreased pulmonary aspiration compared to those nil by mouth since midnight.[2] The following are the recommended guidelines for nil by mouth prior to surgery:[3] Age Solids Clear liquids <6 months 4 hours 2 hours 6–36 months 6 hours 3 hours >36 months (including adults) 6 hours 2 hours When anaesthesia is required in an emergency situation, nasogastric aspiration is usually performed to reduce gastric contents and the risk of its pulmonary aspiration.[4]
  • 3. See also Fasting Surgery General anesthesia References 1. ^ Jump up to: a b c d e f Allman, Keith G.; Iain H. Wilson (2006). Oxford Handbook of Anaesthesia, 2nd edition. Oxford University Press. ISBN 0-19-856609-0 Check |isbn= value (help). 2. ^ Jump up to: a b Maltby JR (April 2006). "Preoperative fasting guidelines". Can J Surg 49 (2): 138–9; author reply 139. PMID 16630428. Retrieved 2008-08-20. 3. Jump up ^ Coté CJ (July 1999). "Preoperative preparation and premedication". Br J Anaesth 83 (1): 16–28. PMID 10616330. Retrieved 2008-08-20. 4. Jump up ^ Legal review of need to place NG tube 2. Indian J Anaesth. 2010 Sep-Oct; 54(5): 445–447. 3. doi: 10.4103/0019-5049.71044 4. PMCID: PMC2991655 “Nil per oral after midnight”: Is it necessary for clear fluids? Kajal S Dalal, Dhanwanti Rajwade, and Ragini Suchak Author information ► Copyright and License information ► Go to: Abstract Fasting before general anaesthesia aims to reduce the volume and acidity of stomach contents, thus reducing the risk of regurgitation and aspiration. Recent guidelines have recommended a shift in fasting policies from the standard ‘nil per oral from midnight’ to a more relaxed policy of clear fluid intake a few hours before surgery. The effect of preoperative oral administration of 150 ml of water 2 h prior to surgery was studied prospectively in 100 ASA I and II patients, for elective surgery. Patients were randomly assigned to two groups. Group I (n = 50) was fasting overnight while Group II (n = 50) was given 150 ml of water 2 h prior to surgery. A nasogastric tube was inserted after intubation and gastric aspirate was collected for volume and pH. The gastric fluid volume was found to be lesser in Group II (5.5 ± 3.70 ml) than Group I (17.1 ± 8.2 ml) which was statistically significant. The mean pH values for both groups were similar. Hence, we conclude that patients not at risk for aspiration can be allowed to ingest 150 ml water 2 h prior to surgery.
  • 4. Keywords: Clear fluids, preoperative fasting, pulmonary aspiration, stomach contents - pH, volume Go to: INTRODUCTION Long fasting hours prior to surgery is a great discomfort to the patient. Despite recent guidelines stating that it is appropriate to reduce the interval of clear fluid ingestion to 2 h prior to surgery,[1] it is common practice to follow “nothing by mouth” or Nulla per os (NPO) after midnight for both solids as well as clear fluids. Decreasing the fasting period enhances the quality and efficiency of anaesthesia care by decreasing the cost, increasing the patient satisfaction and avoiding delays and cancellations. Also there is a decrease in the risk of dehydration and hypoglycaemia and thereby decrease in the perioperative morbidity. Previous studies have shown that pH< 2 and volume of gastric aspirate > 25 ml (0.4 ml/kg) predispose a patient to pulmonary aspiration,[2] hence a strict overnight fasting regimen was instituted. However, the cochrane database has reviewed several studies showing that prolonged withholding of oral fluids does not improve gastric pH or volume, and permitting a patient to drink fluids preoperatively may even result in significantly lower gastric fluid volumes.[3] In an attempt to reduce the fasting hours of a patient preoperatively without increasing the risk of pulmonary aspiration, we decided to assess the safety of ingestion of 150 ml of water 2 h prior to surgery in patients undergoing general anaesthesia with endotracheal intubation. Go to: METHODS After Ethics Committee approval with written informed consent, 100 ASA I and II patients between 12 and 60 years of age, posted for elective orthopaedic, gynaecological, otolaryngological and general surgery were divided into two groups. Emergency surgeries, patients with history of acid peptic disease, anticipated difficult intubation, diabetes mellitus, obesity, pregnancy, hiatus hernia[4] as well as those routinely taking any medications that affected gastric motility or secretion were excluded from the study. Group I was kept fasting overnight whereas Group II was given 150 ml water 2 h prior to surgery. Patients were premedicated with midazolam and pentazocine, and general anaesthesia was induced using intravenous thiopentone sodium followed by vecuronium. An 18 G and 16 G Ryle’s tube was inserted in male and female patients, respectively after intubation and its position was confirmed by auscultation over the epigastrium for insufflated air. Gastric aspirate was obtained through a 20 ml syringe with the patient supine with an assistant massaging the upper abdomen, as well as with various other positions like Trendelenburg, left lateral and right lateral positions to facilitate maximal aspiration.
  • 5. Volume of aspirate was noted and pH measured using a standardized pH strip. Sex, age, weight, type of surgery, duration of fasting and interval between ingestion of water and surgery was documented. Results were given as mean ± SD. Data collected were analysed using Student’s t-test. Differences were considered statistically significant if P values were <0.05. Go to: RESULTS There was no significant difference between the groups with regard to weight, age and sex. Patients who were kept fasting overnight (Group I) had an average fasting time of 12 h. The ingestion - surgery interval for Group II was on an average 2 h [Table 1]. Table 1 Patient demographics Patients who had 150 ml of water (Group II) had lesser volume of gastric aspirate (5.5 ± 3.70 ml) than that of Group I (17.1 ± 8.21 ml) which was statistically significant [Table 2]. The pH was found to be in the same range for both the groups (Group I: 1.7 ± 0.28, Group II: 1.6 ± 0.26) [Table 2]. Patients at high risk i.e. gastric fluid volume > 25 ml and pH <2.5 are shown in Table 3. Group I had four patients with a combination of both risk factors, while none were present in Group II. Table 2 Comparison of volume and pH of gastric fluid in both groups
  • 6. Table 3 Incidence of risk factors Go to: DISCUSSION Pulmonary aspiration of gastric contents during anaesthesia though a rare event,[5] with an incidence of 1 in 7,000 to 8,000 in ASA I and II patients, and 1 in 400 ASA III to V patients,[6] is still considered a significant cause of anaesthesia-related deaths. The severity of pulmonary damage is related to both the volume and pH of the gastric fluid. A combination of volume > 25 ml and pH < 2.5 is considered lethal.[2] Hence any safety measure that reduces this hazard is preferred, so the routine preoperative practice of “nothing by mouth after midnight” is followed. But unfortunately, the ‘nil per oral’ order is blindly applied to both liquids and solids and has become engrained in our anaesthetic practice.[7] The time required for solid food to liquefy and enter the small intestine depends on the type of food ingested (being shorter for carbohydrates and proteins than for fats and cellulose) and the food particle size.[8] Complete emptying of solids from the stomach takes 3 to 6 h, but may be prolonged by fear, pain or opioids.[9] So it is appropriate that no solid food be eaten on the day of surgery. However, the gastro-oesophageal emptying of liquids is rapid wherein studies have shown that gastric emptying after intake of a carbohydrate drink is complete within 2 h of ingestion.[10] At the time of induction of anaesthesia, gastric fluid volume is quite variable in normal people. Even if the patient is fasting, the stomach is not totally empty. On an average, 25 ml to 35 ml of gastric fluid remains in the stomach.[6] Comparing this to the traditional cut-off of gastric fluid volume >25 ml and pH < 2.5, 30-60% patients would be at a risk of pulmonary aspiration, but on an average, the incidence is as low as 1 in 3000.[11] Passive regurgitation of gastric contents can occur only if intragastric pressure exceeds the protective tone of the lower oesophageal sphincter, and for pulmonary aspiration to occur, the protective airway reflexes must also be abolished.[6] Our study was undertaken to determine whether a 2 h fast with clear fluids was safe for patients. Clear fluids would include black tea, coffee, water, carbonated drinks and fruit juices without any particulate matter.[12] We chose 150 ml of water to be given 2 h prior to surgery. We used a Ryle’s tube for aspiration of gastric contents which is a well accepted method for assessment.[5,6,13,14] Our study confirmed the results of previous studies[3,5,6] that even after 11-13 h of fasting, a large number of patients had gastric pH < 2.5 and gastric fluid volume >25 ml.
  • 7. Patients who received 150 ml water actually had decreased gastric fluid volume which was statistically significant as seen in another study.[3] The pH remained unaffected, thereby not increasing the risk of pulmonary complications due to aspiration. Studies have also shown that giving clear fluids increased patient comfort, decreased anxiety and thirst.[10,15] We conclude that it is safe to conduct general anaesthesia in patients who have ingested 150 ml of water 2 h prior to surgery. Prolonged withholding of oral fluid does not decrease gastric fluid volume and pH. Clinicians should appraise this evidence and adopt the recent ASA guidelines which recommend an evolution from the indiscriminate ‘NPO after midnight’ blanket fasting policy. However, the customary 8 h fasting should be followed for patients at a higher risk of aspiration like in diabetes mellitus, pregnancy, obesity, etc. as more research is necessary to determine the safety in these patients. The risk of unexpected regurgitation cannot be avoided even by overnight fasting, and anaesthesiologists must always be prepared to deal with these complications. Go to: Footnotes Source of Support: Nil Conflict of Interest: None declared. Go to: REFERENCES 1. Practice guidelines for preoperative fasting and the use of pharmacological agents to reduce the risk of pulmonary aspiration: Application to healthy patients undergoing elective procedures. Anesthesiology. 1999;90:898–905. [PubMed] 2. Mendelson CL. The aspiration of stomach contents into the lungs during obstetric anaesthesia. Am J Obstet Gynecol. 1946;52:191–205. [PubMed] 3. Brady M, Kinn S, Stuart P. Preoperative fasting for adults to prevent perioperative complications. Cochrane Database Syst Rev. 2003;4:CD004423. [PubMed] 4. Asai T. Editorial II. Who is at increased risk of pulmonary aspiration? Br J Anaesth. 2004;93:497–500. [PubMed] 5. Cook-Sather SD, Gallagher PR, Kruge LE, Beus JM, Ciampa BP, Welch KC, et al. overweight/obesity and gastric fluid characteristics in pediatric day surgery: implications for fasting guidelines and pulmonary aspiration risk. Anesth Analg. 2009;109:727–36. [PubMed] 6. Maltby JR, Pytka S, Watson NC, Cowan RA, Fick GH. Drinking 300ml of clear fluid 2 hours before surgery has no effect on gastric fluid volume and pH in fasting and non-fasting obese patients. Can J Anaesth. 2004;51:111–5. [PubMed]
  • 8. 7. Wachtel R, Dexter F. A Simple Method for deciding when patients should be ready on the day of surgery without procedure-specific data. Anesth Analg. 2007;105:127–40. [PubMed] 8. Pandit SK, Loberg KW, Pandit UA. Toast and tea before elective surgery? Anesth Analg. 2000;90:1348–51. [PubMed] 9. Scarr M, Maltby JR, Jani K, Sutherland L. Volume and acidity of residual gastric fluid after oral fluid ingestion for elective ambulatory surgery. CMAJ. 1989;141:1151–4. [PMC free article] [PubMed] 10. De Aguilar-Nascimento JE, Borges Dock-Nascimento D. Reducing preoperative fasting time: A trend based on evidence. World J Gastrointest Surg. 2010;2:57–60. [PMC free article] [PubMed] 11. Schreiner MS. Gastric Fluid Volume: Is it really a risk factor for pulmonary aspiration? Anesth Analg. 1998;87:754–6. [PubMed] 12. Pandit SK, Loberg KW, Pandit UA. Coffee is not a clear fluid. Anesth Analg. 2000;91:1306–13. 13. Goldstein H, Boyd JD. The saline load test- a bedside evaluation of gastric retention. Gastroenterology. 1965;49:375–80. [PubMed] 14. Hardy JF. Large volume gastro-oesophageal reflux: a rationale for risk reduction in the perioperative period. Can J Anesth. 1988;35:162–73. [PubMed] 15. Wong CA, MacCarthy RJ, Fitzgerald PC, Raikoff K, Avram MJ. Gastric emptying of water in obese pregnant women at term. Anesth Analg. 2007;105:751–5. [PubMed]