TLDR;
This video provides a comprehensive overview of perioperative nutrition and fluid therapy, essential for surgical patient management. It covers metabolic responses to stress and starvation, assessment techniques for nutritional status, fluid and electrolyte replacement strategies, and methods of artificial feeding (enteral and parenteral). The importance of proactive intervention, understanding metabolic changes, and preventing complications like refeeding syndrome are emphasized.
- Metabolic Response to Starvation and Trauma
- Nutritional Assessment (ABCD approach)
- Fluid and Electrolyte Management
- Enteral and Parenteral Nutrition
- Complications and Special Considerations
Introduction [0:00]
The video introduces the critical importance of perioperative nutrition and fluid therapy in surgical management. It highlights that these aspects are foundational for patient recovery and preventing complications. The discussion emphasizes the complexity beneath what might seem basic, noting that patient management is dictated by the body's metabolic response to stress and illness. The goal is to distill essential information into memorable and usable concepts for both students and practitioners of surgery.
Metabolic Response to Fasting or Starvation [3:24]
The body's metabolic response to fasting is discussed, differentiating between simple fasting and the stress response seen in surgical patients. Initially, the body uses stored glycogen through glycogenolysis, with the Cori cycle recycling lactate to glucose. As glycogen stores deplete (after 24-40 hours), the body shifts to gluconeogenesis, using amino acids from muscle protein, lactate, and glycerol from fat breakdown to create glucose. Prolonged starvation leads to lipolysis, where fatty acids are converted to ketone bodies, reducing the body's dependence on glucose and slowing muscle breakdown.
Metabolic Response to Trauma and Sepsis [6:47]
The metabolic response to trauma and sepsis is markedly different from simple starvation, characterized by an inflammatory storm and increased energy requirements. Counterregulatory hormones surge, but the body becomes insulin resistant, impairing the shift to using ketones. This results in continuous muscle protein breakdown for gluconeogenesis, even with caloric intake. Insulin resistance is caused by stressors that inhibit GLUT4 activation, preventing glucose from entering cells. Modern interventions, such as ERAS protocols, aim to dampen this severe stress response through preoperative carbohydrate loading, minimally invasive surgery, and early mobilization.
ABCD Approach [10:45]
Nutritional assessment is crucial before initiating aggressive feeding, using the ABCD approach. Anthropometry involves measuring physical body composition, including weight, BMI, mid-upper arm circumference (MUAC), and skinfold thickness (TSF). Red flags include a BMI under 18.5 with >10% unintentional weight loss or a BMI under 20 with >5% weight loss. Biochemistry involves blood tests for inflammation (CRP, white cell count) and deficiencies. Albumin is unreliable in the acute setting due to fluid balance and its role as a negative acute phase reactant. Key blood tests include hemoglobin, HbA1c, and electrolytes (potassium, magnesium, phosphate). Clinical evaluation includes assessing symptoms that prevent eating or absorption, such as nausea, vomiting, and diarrhea, along with past medical history (cancer, IBD). Dietary assessment quantifies the gap between nutritional needs and intake, estimating energy requirements at 25-35 kcal/kg of lean body weight per day.
Malnutrition Universal Screening Tool [16:13]
The Malnutrition Universal Screening Tool (MUST), developed by BAPEN, is a rapid screening tool to standardize nutritional assessment. It consists of three components: BMI, recent unintentional weight loss, and acute disease effect (reduced nutritional intake). Each component is scored, and the total score guides action: a score of 0 indicates low risk, a score of 1 indicates medium risk (requiring observation and repeat screening), and a score of 2 or more indicates high risk, necessitating immediate treatment and referral to a specialist team.
Fluid and Electrolyte Replacement [18:08]
Fluid and electrolyte replacement are critical and interwoven with nutrition in surgical patients. Normal daily fluid balance involves roughly 2.5L of intake balancing 2.5L of output, including insensible losses (900ml). Maintenance fluid requirement is about 30 ml/kg/day, with daily electrolyte needs of 0.9-1.2 mEq/kg for sodium and 1 mEq/kg for potassium, along with calcium and magnesium. Oral rehydration solutions are preferred; IV fluids are a last resort. The choice of IV fluid is critical, with consideration of its composition compared to plasma.
Intravenous Fluid Replacement Solutions [20:34]
The video compares common IV fluid solutions to plasma, noting significant differences. Normal saline (0.9% saline) has higher sodium and chloride levels than plasma, potentially leading to hyperchloremic metabolic acidosis. Hartman's solution (lactated Ringer's) is more physiological due to its lactate content, which the liver metabolizes into bicarbonate, providing a buffering capacity. Dextrose (5%) is essentially free water, used for replacing pure water deficits. The fluid choice must be tailored to the patient's specific needs and the type of fluid they are losing. Colloids are not generally recommended for routine volume resuscitation.
Assessment and Fluid Loss Composition [23:22]
Tailored fluid choice requires careful monitoring of hemodynamics, fluid balance, and serum electrolytes. The composition of fluid loss from different parts of the GI tract varies significantly. High NG tube output leads to hypochloremic metabolic alkalosis, requiring replacement with saline and potassium. Lower GI losses (pancreas, bile duct, small bowel fistula) cause dehydration and metabolic acidosis, needing a balanced salt solution like Hartman's or fluids with extra bicarbonate.
Nutritional Requirements [25:31]
Estimating the basal metabolic rate (BMR) is the starting point for planning any feed, often using the Harris-Benedict equations. For stable but unwell patients, the requirement is typically 20-30 kcal/kg of ideal body weight per day. Overfeeding is a common cause of complications, leading to increased CO2 production, hyperglycemia, and fatty liver changes. Starting slow is crucial, especially in high-risk patients, gradually increasing towards the full requirement over several days.
Macronutrients [28:04]
Carbohydrates, usually given as glucose, are the central fuel, making up 45-65% of total caloric intake. Protein needs increase sharply in illness, aiming for 1.5 g/kg of ideal body weight per day, constituting around 20% of total energy intake. Fat provides essential fatty acids and is often given as a lipid emulsion in parenteral nutrition, combined with a minimum amount of glucose for metabolic safety and reduced CO2 production.
Vitamins, Minerals, and Trace Elements [29:50]
Micronutrients, especially vitamins B and C, are vital. Vitamin C is essential for collagen synthesis and wound healing. Thiamine (B1) is critical to prevent refeeding syndrome. Patients with alcohol abuse or gastric surgery need supplementation with thiamine, B12, and folate. Conditions affecting fat absorption require monitoring and replacement of fat-soluble vitamins (A, D, E, K). Continuous losses can deplete sodium, potassium, magnesium, and phosphate. Trace elements like zinc, copper, selenium, and iron are crucial for healing and metabolism.
Effects of Intestinal Resection [31:45]
Intestinal resection presents a significant nutritional challenge. The remaining bowel can adapt, but the location of the resection matters. Ileal resections, especially of the terminal ileum, impair bile salt reabsorption, leading to osmotic diarrhea and steatorrhea. Cholestyramine can help manage diarrhea, but fat restriction is often necessary. Loss of the ileum also increases gastric emptying and intestinal transit, compounding malabsorption.
Short Bowel Syndrome [33:43]
Short bowel syndrome (SBS) is defined as typically less than 200 cm of remaining small intestine, leading to chronic malnutrition and dehydration. The acute stage involves high intestinal losses and gastric hypersecretion, requiring aggressive IV fluid and electrolyte management. The adaptation stage involves structural and functional changes in the remaining bowel, improving absorption. Some patients can wean off parenteral nutrition (PN), but many require specialized diets and medications long-term.
Fluid Management in Severe Cases [35:32]
In severe cases (less than 100 cm of small bowel), patients lose more water and salt than they can absorb. Restricting hypotonic fluids (plain water, tea, coffee, juice) is crucial to prevent osmotic gradients that worsen dehydration. Isotonic or slightly hypertonic oral rehydration solutions (ORS) containing glucose and salt promote absorption.
Indications and Preference [37:00]
Artificial feeding is considered if inadequate oral intake is anticipated for 5 days or more, sooner if already malnourished. Enteral nutrition (EN) is strongly preferred over parenteral nutrition (PN) because it maintains gut integrity, supports gut immunity, and prevents gut atrophy. EN is associated with lower infection rates, better wound healing, and shorter hospital stays. If the gut works, use it, even partially, with supplemental PN if needed.
Methods [38:51]
EN can be delivered via oral nutritional supplements (ONS) or tube feeding. Tube feeding options include pre-pyloric feeding (nasogastric or gastrostomy tubes) and post-pyloric feeding (nasojejunal or jejunostomy tubes). Post-pyloric feeding is useful for delayed gastric emptying or high aspiration risk. Starting the feed requires careful planning by a dietitian, starting slow (10-20 ml/hour) and gradually increasing the rate. Meticulous flushing prevents tube blockages. Never reinsert the guide wire to unblock a feeding tube.
Long-Term Access [42:09]
For longer-term feeding (more than 4-6 weeks), gastrostomy or jejunostomy tubes are considered. Percutaneous endoscopic gastrostomy (PEG) tubes are commonly placed by gastroenterologists. Radiologically inserted gastrostomy (RIG) tubes are used if endoscopy is difficult. Surgical gastrostomy is reserved for when PEG or RIG aren't feasible. Complications include perforation, bleeding, infection, and leakage.
Complications of Enteral Feeding [44:58]
Complications of EN include tube-related issues (malposition, blockage, leakage) and GI side effects (diarrhea, bloating, nausea, vomiting). EN is contraindicated in complete bowel obstruction or severe paralytic ileus. Diarrhea is a frequent problem, often due to feed composition, rate of infusion, medications, or infection. Systemic risks include electrolyte disturbances and refeeding syndrome.
Indications and Composition [46:33]
Parenteral nutrition (PN) is used when the gut cannot be used, delivering nutrients directly into the bloodstream. The primary indication is intestinal failure. PN is also used temporarily for intractable vomiting, severe paralytic ileus, high output fistulas, or severe acute pancreatitis. A TPN bag is a complex 3-in-1 mixture containing a lipid emulsion, amino acids, glucose, electrolytes, trace elements, and vitamins. The energy content needs to be balanced with the protein nitrogen content.
Administration of Parental Nutrition [48:57]
TPN must be infused into a large central vein due to its high osmolality. The catheter tip should sit in the lower third of the superior vena cava (SVC) or at the atrio-caval junction. Peripheral PN (PPN) is avoided due to the high risk of thrombophlebitis. Central venous access options include PICC lines, non-tunneled central venous catheters (CVCs), tunneled cuffed catheters (Hickman or Broviac lines), and implantable port devices. Femoral lines are discouraged. A chest X-ray is mandatory after insertion to confirm the line position. TPN solutions containing vitamins are light-sensitive and must be protected from UV light.
Nutrition Summary [52:17]
PN carries significant risks. Insertion complications include pneumothorax, misplacement, arterial puncture, and air embolism. Line sepsis is a major concern, requiring strict aseptic technique. Thrombosis can occur around the catheter tip. Refeeding syndrome is a critical metabolic complication, requiring slow start, gradual increase, and intense electrolyte monitoring. Long-term metabolic issues include liver dysfunction (intestinal failure-associated liver disease or IFALD) and metabolic bone disease.
Summary and Conclusion [58:17]
The core message emphasizes careful assessment, matching fluid therapy to losses, and providing timely nutritional support, considering the impact of the underlying disease and surgical intervention. Safety is paramount, especially in preventing metabolic complications like refeeding syndrome. Enteral nutrition is favored whenever possible. Managing complex patients requires a multidisciplinary nutrition support team. The ultimate goal for patients on long-term PN is weaning off and achieving gut autonomy.
