FOR GENERAL SURGERY



ANESTHETIC CONSIDERATIONS IN ABDOMINAL SURGERY


Preoperative Evaluation


•  Fluid status: Patients often hypovolemic


•  Inadequate fluid intake (fasting, anorexia)


•  Fluid loss (emesis, bowel preps, GI bleeding, fevers = insensible loss)


•  Sequestration of fluid from intravascular space (3rd spacing)



Anesthetic Management


Technique


•  Abdominal procedures usually require muscle relaxation


• Epidural analgesia may be beneficial (↓ anesthetic requirements, blunt surgical stress response, ↑ postop pain relief, ↓ postop atelectasis, ↑ postop mobility)



Fluid Management (See Chapter 9 on Fluids, Electrolytes, and Transfusion Therapy)


•  General strategies


• Body wt-based formulas: Rough guidelines for fluid replacement


• Goal-directed strategies: Aimed at optimizing stroke volume, cardiac output, & tissue perfusion. Use mechanical ventilation or fluid bolus induced variations in pulse pressure (dPP), stroke volume (SV), or cardiac output (CO) to assess fluid responsiveness


• A more than 13% change in dPP, SV, or CO predicts fluid responsiveness


• Restrictive management: 4–8 mL/kg/hr—some evidence for ↓ postop morbidity compared with “liberal” strategies (10–15 mL/kg/hr)


•  Replacement ratio: 3 mL crystalloid per 1 mL fluid loss 1 mL colloid per 1 mL fluid loss


• Only 1/3 of crystalloid remains intravascular, 2/3 goes into interstitium


• Colloids remain intravascular longer than crystalloids & exert oncotic pressure


•  Blood products—should be given based on clinical eval of blood loss (surgical suction canister, sponges) & lab values (hematocrit)


Muscle Relaxation


•  Usually required for intra-abdominal procedures & abdominal closure


• Secondary to intraop bowel edema & abdominal distention


•  Inhalational agents may potentiate effects of muscle relaxants


•  Neuraxial blockade with local anesthetics can provide good muscle relaxation


Use of Nitrous Oxide (N2O)


• N2O diffuses into bowel lumen faster than nitrogen can diffuse out


•  Degree of bowel distention is a function of


• N2O conc, blood flow to the bowel, duration of admin


•  Avoid N2O (relative contraindication) in bowel obstruction


• May have large initial volume of bowel gas and/or difficult surgical closure


•  Causes an obligatory reduction in FiO2


• However, ↑ FiO2 may reduce incidence of surgical wound infection


•  May ↑ pulmonary artery pressure (esp in pts with pulmonary HTN)


•  Possible ↑ incidence of PONV (data is mixed)


Common Intraop Problems


•  ↓ FRC, atelectasis, & hypoxemia because of


• Surgical retraction of abd viscera to improve exposure


• Insufflation of gas during laparoscopy


• Trendlenburg position
(Application of PEEP may reverse those effects)


•  Hypothermia 2° to heat loss: Radiation > convection > conduction > evaporation


• Most heat loss occurs during 1st hr of anesthesia (1–1½°C)


(treat byOR temp, apply convective warming blankets, warm IV fluids)


•  Hypotension, tachycardia, & facial flushing during bowel manipulation


• 2° to mediator release (prostaglandin F1-α, aprostanoid)


•  Opioid-induced biliary tract spasm


•  May interfere with interpretation of intraop cholangiograms


(Reversed by naloxone, nitroglycerin, & glucagon)


•  Hiccups are episodic diaphragmatic spasms relieved by


anesthetic depth,neuromuscular blockade, drainage of stomach to relieve gastric distention


ALCOHOL ABUSE


Preop Evaluation


•  Alcoholic cirrhosis characterized by AST/ALT ratio >2


Anesthetic Considerations


•  Acute intoxication: ↓ anesthetic requirements (2° to EtOH depressant effects)


•  Chronic intoxication: ↑ anesthetic requirements (2° to tolerance)


•  Head & cervical spine injury must be considered in intoxicated pts


Postop Considerations


•  Unrecognized alcohol abuse may present with delirium tremens


•  Often occurs 72 hrs after last drink (postop day 3)


•  Signs: Autonomic hyperactivity, tremors, hallucinations, seizures


•  Treatment: Benzodiazepines



ANESTHETIC MANAGEMENT: LIVER SURGERY


General Considerations


•  Liver resections often done for metastasis to liver or 1° hepatocellular carcinoma


•  Hypoxemia → 2° hepatopulmonary shunting, atelectasis, ↓ FRC from ascites


•  Prior portosystemic shunt ↑ surgical complexity & risk of surgical bleeding


Management of Portal Hypertension


•  Pharmacologic: β-blockers


•  Endoscopic: Sclerotherapy & esophageal banding for bleeding varices


•  Transjugular intrahepatic portosystemic shunt (TIPS) have replaced surgical shunts, done percutaneously under fluoroscopy


•  Surgery: ↑ risk of encephalopathy, no evidence of better outcome


Monitoring


•  A-line & CVP


Anesthetic Technique


•  General endotracheal anesthesia


•  Thoracic epidural for postop pain control (provided no coagulopathy)


•  Aspiration precautions (nonparticulate antacids, rapid-sequence induction)


•  Avoid N2O (risk of bowel expansion & potential ↑ pulm artery pressure)


•  Avoid histamine releasing muscle relaxants (atracurium, mivacurium) to avoid further ↓ blood pressure


•  Hyperdynamic circulation in pts with end-stage liver disease may require vasopressor therapy to ↑ systemic afterload


•  Concomitant pulmonary HTN in pts with ESLD → avoid hypoxemia, hypercarbia, & metabolic acidosis (worsen pulmonary HTN)


•  Careful NG tube placement (concern for coagulopathy + esophageal varices)


• Fluid replacement with isotonic fluids & colloids (pts have ↓ intravascular oncotic pressure)


•  Prolonged hepatic “inflow” occlusion (Pringle maneuver: Occlusion of portal vein & hepatic artery) → may lead to coagulopathy & metabolic acidosis


Postop Care


•  Bleeding: Surgical vs. coagulopathy


•  Small for size syndrome in extensive hepatic resections (remaining liver unable to support metabolic functions → ↑ lactate, ↑ liver enzymes, worsening metabolic acidosis)


ANESTHETIC MANAGEMENT: BARIATRIC SURGERY


General Considerations


•  Body mass index (BMI) = body weight in kg/(height in meters)2


•  Overweight = BMI > 25; Obesity = BMI > 30; Morbid obesity = BMI > 35


Types of Bariatric Surgery


•  Vertical band gastroplasty


• Creation of small pouch → restricts volume of food that can be ingested


•  Open Roux-en-Y gastric bypass


• Formation of small gastric pouch anastomosed to proximal jejunum


• Dumping synd.: Ingestion of energy-dense-food → nausea, diarrhea abd pain


• Pts at risk for Fe and B12 deficiency


•  Laparoscopic Roux-en-Y gastric bypass


• Smaller incision, ↓ postop pulm complications/pain, earlier ambulation


Preanesthetic Considerations


•  Obesity-associated comorbidities


• HTN, hyperlipidemia, obstructive sleep apnea (OSA), GERD, type II diabetes


• ↑ circulating blood volume, ↑ cardiac output → ↑ in O2 consumption


• ↓ lung compliance, ↑ ventilation/perfusion mismatch & ↓ FRC → hypoxemia


• Long-standing hypoxemia → pulmonary HTN, & rt-sided heart failure


Anesthetic Technique


•  General endotracheal anesthesia


•  Epidural analgesia for pts undergoing open Roux-en-Y bypass


• Reduces need for systemic opioids & oversedation in pts with OSA


Airway Management


•  Specific considerations


• Predictors of difficult intubation: ↑ neck circumference (>42 cm) & Mallampati score III & IV


• Obesity = risk factor for difficult mask ventilation


• Rapid desaturation following induction 2° to ↓ FRC, ↑ O2 consumption, & ↑ incidence of airway obstruction


•  Management strategies


• Preoxygenation for 3 min in a 25° head-up position


• Consider ramped position (horizontal alignment between auditory meatus & sternal notch) to improve laryngeal view


• Consider awake intubation if airway exam concerning


• Consider aspiration precautions (antacids + rapid-sequence induction)


• Consider use of insoluble gases (desflurane, sevoflurane)


• Consider short-acting narcotics & sedatives (↓ risk postop resp. depression)



Monitoring


•  Indications for A-line: Hypoxemia, ↓ systolic fx, moderate & severely ↑ pulm artery press, & inability to measure bp noninvasively


•  ECG: May show RBBB 2° to pulmonary HTN


•  DVT risk: ↓ risk with pneumatic compression devices and/or SC heparin


•  Equip: OR table must accommodate pt weight, capacities vary widely


Postop Complications


•  ↑ Incidence of atelectasis & hypoxemia (consider semirecumbent position, CPAP or BIPAP)


•  ↑ Postop. hypercarbia esp in pts with baseline retention and periop opioid use → CO2 narcosis → hypercapnic resp. failure


•  Negative-pressure pulmonary edema 2° to inspiration against closed glottis


•  Accidental stapling of NG tube to pt stomach (prevent by keeping close communication with surgical team)


•  DVT prophylaxis & early ambulation ↓ risk of thromboembolism


ANESTHESTIC MANAGEMENT: LAPAROSCOPIC SURGERY


General Considerations


•  Advantages include smaller incision, ↓ surgical trauma, ↓ postop pain, ↓ pulmonary dysfx, ↓ postop ileus, faster recovery, & ↓ hospital stay


•  3 ports typically inserted into abdomen: (subumbilical port used for CO2 insufflation to 12–15 mm Hg)



Anesthetic Technique: Laparoscopic Surgery


•  General anesthesia with endotracheal intubation and controlled ventilation


•  Muscle relaxation to avoid further increase in intrathoracic pressure


•  Rapid-sequence induction for antireflux procedures and patients with full stomach


• Persistent ↑ ETCO2 despite adequate minute volume may signal subcutaneous emphysema


•  Attenuation of hemodynamic changes to peritoneal insufflation:


• Bradycardia → glycopyrrolate or atropine


• Decreased CO & hypertension → use volume loading and/or vasopressor


• Hypertension → use vasodilators



Monitoring


•  Large-bore peripheral IV access (limited access to tucked arms during case)


•  Orogastric tube to aspirate gas from stomach prior to trocar placement


•  Acute ↑ in peak airway pressure may signal:


• Endobronchial migration of tube (esp. with bed change to Trendlenburg)


• Pneumothorax (usually accompanied by ↓ SpO2)


•  Avoid ↑ peak airway pressure: Use pressure-control ventilation and ↓ exp time (e.g., I/E ratio 1:1.5)


• Minute volume usually must be ↑ by 20% to maintain normocarbia


•  Bradycardia following CO2 insufflation likely vagally mediated


• May also be 2° to hypercarbia & respiratory acidosis


•  Avoid ↑ in insufflation pressure that can compromise venous return (max 12–15 mm Hg)


Postop Care


•  Shoulder pain (suprascapular nerve irritation)—treat with NSAIDs


•  Unrecognized intra-abdominal visceral/vascular injury → progressive hypotension, ↑ abdominal girth, ↓ hematocrit


•  ↑ incidence of PONV


•  Extensive subcutaneous emphysema may require mechanical ventilation


LARGE INTESTINAL SURGERY


Indications


•  Colon cancer, diverticulitis, ulcerative colitis, Crohn’s dz, ischemic colitis, reversal of colostomy


Preop Evaluation


•  Preop fasting + bowel prep = large fluid deficit


•  Bowel obstruction can ↑ risk for gastric aspiration during induction


•  Thoracic epidural analgesia (T8–12) ↓ atelectasis, ↑ early ambulation (may contribute to hypotension in presence of hypovolemia)


Anesthetic Management: Large Intestinal Surgery


•  Consider aspiration precautions if pt is obstructed


•  Consider stress dose steroids if pt on preop steroids


•  Fluid replacement must account for evaporative losses of exposed viscera


•  Mesenteric traction syndrome: Hypotension during bowel surgery from bowel-associated mediator release (vasoactive intestinal peptide)


→ Hypovolemia, surgical bleeding, sepsis 2° to peritoneal fecal spillage


Postop Complications


•  Prokinetic agents (metoclopramide) can cause anastomotic dehiscence after colonic surgery


•  Postop ileus caused by bowel manipulation, opioids, immobility, lack of enteral feeding, & bowel edema from fluid overload (epidural analgesia mayincidence of ileus)


•  Prolonged NG tube placement can lead to ischemic necrosis of nasal septum


SMALL INTESTINAL SURGERY


Indications


•  Small bowel obstruction, neoplasms, intussusception, intestinal bleed, resection of carcinoid tumor, Crohn’s dz


Carcinoid Tumors/Carcinoid Syndrome


•  Carcinoid tumors typically asymptomatic


→ May present with abd pain, diarrhea, & intermittent obstruction


•  Metastatic carcinoid tumors (hepatic, pulm metastases) systemic symptoms


→ Carcinoid syndrome: Cutaneous flushing, bronchoconstriction, hypotension, diarrhea, & rt-sided valvular lesions


↑ 5-hydroxy-indole-acetic acid (>30 mg in 24-hr urine)


•  Epidural analgesia may exacerbate intraop hypotension (consider use of dilute local anesthetics/narcotics + volume loading)


Monitoring


•  Consider TEE for carcinoid (eval rt-sided heart lesions & guide fluid therapy)


Anesthetic Management


•  Consider aspiration precautions/rapid-sequence induction for obstruction


•  Carcinoid tumors


• Avoid agents that release histamine (thiopental, succinylcholine, atracurium, morphine)


• Octreotide (synthetic somatostatin) effective in relieving hypotension (subcutaneous dose 50–500 mcg—half-life of 2.5 hrs)


Postop Care


•  50% of carcinoid deaths result from cardiac involvement


•  Similar considerations as in large intestine surgery


PANCREATIC SURGERY


Indications


•  Pancreatic adenocarcinoma resection (Whipple: Pancreatojejunostomy with gastrojejunostomy & choledochojejunostomy)


•  Treatment of complications of pancreatitis: Infected pancreatic necrosis, hemorrhagic pancreatitis, drainage of pancreatic pseudocyst


Monitoring


•  Pancreatic surgery can be assoc with significant blood loss & fluid shifts (consider A-line, CVP depending on pt comorbidities)


Anesthetic Management


•  Consider thoracic epidural analgesia (T6–T10) for postop pain control


•  Often feeding tube tip will be adjusted by surgeon during procedure


•  Pancreatic surgery for infection may be complicated by sepsis & ARDS
requires aggressive fluid resuscitation, vasopressor support (α-agonist, e.g., norepinephrine) & postop mechanical ventilation


Postop Care


•  Significant pancreatic resection → insulin insufficiency & new-onset diabetes


SPLENIC SURGERY


Indications


•  Splenic injury (blunt or penetrating trauma)


•  Idiopathic thrombocytopenic purpura with splenic sequestration of platelets


Preop Preparation


•  Periop platelet transfusion not warranted (unless platelet count is <50,000/μL or clinical evidence of coagulopathy)


Anesthetic Management


•  Avoid drugs that interfere with platelet function (NSAIDs)


Postop Care


•  Pts should receive pneumococcal, Haemophilus influenzae, & meningococcal vaccines


HEMORRHOIDECTOMY & DRAINAGE OF PERIRECTAL ABSCESS


Anesthetic Management


•  Procedures usually short, often in lithotomy/prone position


•  Usually general anesthesia (consider LMA for lithotomy cases)


•  Spinals may be used (hypobaric soln for prone case, hyperbaric for lithotomy)


•  Deep plane of anesthesia provides sphincter relaxation


Postop Care


•  Postop pain can be severe → consider use of narcotics & NSAIDs


INGUINAL HERNIORRHAPHY


Anesthetic Management


•  Commonly done as an outpatient procedure


•  Spermatic cord traction may initiate a vagally mediated bradycardia


• MAC + local anesthesia most common approach


• Paravertebral block (T10–L2) increasingly used


• Spinal or general anesthesia may also be used


VENTRAL HERNIORRHAPHY


Preop Considerations


•  Staged ventral hernia repair may ↓ incidence of postop respiratory failure (closure of large abd defectspulm restriction)


Monitoring


•  Obtain large-bore IV access to replace evaporative fluid losses in large cases


Anesthetic Management


•  Consider epidural analgesia (T10–T12) or transversus abdominis plane block (bilateral for midline incisions, unilateral for one-sided hernias)


•  Usually done with general endotracheal anesthesia + muscle relaxation


•  Smooth emergence impt. (no coughing/bucking) to avoid disruption of repair


APPENDECTOMY


Preop Evaluation


•  Consider preop IV hydration to replace fluid deficits (vomiting, poor intake)


Anesthetic Management


•  Performed via open or laparoscopic approach


•  Consider taking aspiration precautions (rapid-sequence induction)


Postop Care


•  IV opioids usually sufficient for postop pain management


CHOLECYSTECTOMY


Anesthetic Management


•  Performed via open or laparoscopic approach with general endotracheal anesthesia


•  Opioid-induced biliary tract spasm


• May interfere with interpretation of intraop cholangiograms


• Can be reversed by naloxone, nitroglycerin, & glucagon


•  Minimal blood loss unless abdominal vessel injury occurs


Postop Care


•  Lap cholecystectomy → less postop pain & earlier discharge (usually same day)


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Aug 28, 2016 | Posted by in ANESTHESIA | Comments Off on FOR GENERAL SURGERY

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