Medical School · Year 4 · Subinternship Medicine · includes a quiz and discussion video

Advanced Procedures and Skills

Year 4: Sub-Internship Medicine

Procedural competence represents an essential component of medicine training, with the sub-internship providing critical opportunities to develop skills that will be expected during internship. This seminar provides a comprehensive framework for procedural preparation, technique, and complication management for the procedures most commonly performed by internal medicine physicians. The emphasis is on developing not only technical skills but also the judgment to recognize appropriate indications, obtain informed consent, and manage complications when they occur.

Learning Objectives

1. Perform common ward procedures including venipuncture, peripheral IV placement, and arterial blood gas sampling with appropriate technique
2. Recognize indications, contraindications, and potential complications for lumbar puncture, paracentesis, and thoracentesis
3. Obtain informed consent for procedures by explaining risks, benefits, and alternatives in understandable terms
4. Apply sterile technique appropriately matched to the invasiveness of each procedure
5. Interpret procedure results including CSF analysis, ascitic fluid studies, and pleural fluid analysis using standard criteria
6. Manage procedure-related complications through early recognition, appropriate intervention, and honest disclosure

Procedural Preparation

Indications and consent form the foundation of safe procedural practice. Every procedure requires a clear indication that is documented in the medical record, supporting the medical necessity of the intervention. Alternatives to the procedure should be considered and discussed with the patient. Risks specific to the procedure must be explained in understandable terms, avoiding excessive medical jargon. Expected benefits should be realistic and clearly communicated. Patient questions should be encouraged and thoroughly answered. The patient's capacity to consent must be assessed, with surrogate consent obtained when the patient lacks decision-making capacity.

The pre-procedure checklist ensures safety and preparation. Correct patient identification using two identifiers prevents wrong-patient procedures. Correct procedure verification including side and site prevents wrong-site procedures. Signed and witnessed consent documentation must be present in the chart. Laboratory values including platelet count and INR should be reviewed when relevant to bleeding risk. Allergies to latex, iodine, and local anesthetics must be checked. NPO status is confirmed if sedation is planned. All equipment should be gathered and verified complete before beginning.

Sterile technique is matched to the invasiveness of the procedure. Full sterile technique with sterile gown, gloves, drape, and field is required for invasive procedures including lumbar puncture, paracentesis, and thoracentesis. Aseptic technique with clean gloves and skin antisepsis is appropriate for IV placement and blood draws. Clean technique is sufficient for non-invasive procedures. Hand hygiene before and after every procedure is mandatory regardless of the level of sterile technique employed.

Universal precautions protect both patient and provider. Gloves are worn for all procedures involving potential contact with blood or body fluids. Gowns are worn when splash risk exists. Masks protect against droplet exposure and maintain sterility of the procedural field. Eye protection is worn when splash risk is present. Sharps handling uses a one-handed technique to prevent needlestick injuries. All sharps are disposed of immediately in appropriate containers.

Venipuncture and Blood Draws

Site selection balances accessibility with patient comfort and vein preservation. The antecubital fossa provides large, accessible veins but should be preserved for IV access when possible. Forearm veins provide good backup options with somewhat smaller caliber. Hand veins are usually visible but more painful. External jugular veins provide an option when peripheral access is difficult. Avoid sites with infection, edema, fistulas, or lymphedema. Consider patient preference and prior difficult access history.

Technique follows a systematic approach to maximize success. The tourniquet is applied four to six inches above the intended site. The vein is identified by palpation, feeling for the spongy, bouncing quality of a vein. The site is cleaned with alcohol and allowed to dry completely. The skin is anchored with traction to stabilize the vein. The needle is inserted at 15 to 30 degrees with the bevel facing up. Blood flash in the chamber confirms venous access. Tubes are filled in the correct order. The tourniquet is released before needle removal. Pressure is applied for two to three minutes after withdrawal.

Order of draw prevents cross-contamination between tubes. Blood culture bottles are filled first if being collected. Light blue citrate tubes for coagulation studies are next to prevent activation. Red top or serum separator tubes for chemistry are next. Green heparin tubes for plasma studies follow. Lavender EDTA tubes for complete blood count come next. Gray oxalate tubes for glucose are filled last. This order prevents contamination of tubes by additives from prior tubes.

Troubleshooting addresses common problems. No blood flash may indicate the vein was missed or went through both walls; reposition or try a new site. Slow flow may respond to repositioning or slightly loosening the tourniquet. Hematoma formation requires releasing the tourniquet and applying pressure. Hemolyzed samples result from forceful draws; use gentle technique and avoid syringe aspiration. Clotted samples result from delayed mixing; invert tubes gently immediately after collection.

Peripheral IV Placement

Site selection for IV placement considers both immediate access needs and longer-term use. Forearm and hand veins are preferred first-line sites. Antecubital veins are reserved for larger access needs or when distal sites fail. Upper arm veins may be used but are less comfortable for patients. The dominant arm should be avoided when possible for patient convenience. Sites with infection, infiltration, or phlebitis should be avoided. Extremities with fistulas, lymph node dissection, or lymphedema should not be used.

Gauge selection matches the clinical need. Large-bore 14 or 16 gauge catheters are used for trauma and rapid resuscitation. 18 gauge catheters are appropriate for blood transfusion and surgical patients. 20 gauge catheters serve as the standard for general use. 22 gauge catheters work for difficult access and medication administration. 24 gauge catheters are reserved for pediatric patients and fragile veins. Larger gauges allow faster flow rates but are more difficult to place and more uncomfortable.

Technique follows a sequence designed for success. The tourniquet is applied and a suitable vein is identified. The site is cleaned with antiseptic. The skin is anchored to provide countertraction. The catheter is inserted at 10 to 30 degrees. Blood flash in the chamber confirms entry. The catheter is advanced slightly to ensure the plastic portion is in the vein. The needle is partially withdrawn while the catheter is threaded. The tourniquet is released. The catheter is flushed to confirm patency and secured with appropriate dressing.

Ultrasound guidance improves success in difficult access situations. Indications include failure after two to three blind attempts, obesity with non-palpable veins, and history of difficult access. Technique uses a linear probe in either short-axis (out-of-plane) or long-axis (in-plane) approach. Veins are identified by their compressibility, distinguishing them from non-compressible arteries. The advantages include higher first-attempt success rates and ability to access deeper veins not palpable on surface examination.

Arterial Blood Gas

Indications for arterial blood gas sampling span assessment of oxygenation, ventilation, and acid-base status. Respiratory failure requires assessment of oxygenation and carbon dioxide levels. Acid-base disorders are characterized by pH and bicarbonate. Shock states benefit from lactate measurement. Ventilator management relies on ABG for setting adjustments. Carbon monoxide poisoning requires direct measurement of carboxyhemoglobin. ABG provides information not available from venous sampling or pulse oximetry alone.

Site selection considers accessibility and safety. The radial artery is preferred due to its superficial location and dual blood supply to the hand through the ulnar artery. The femoral artery is large and accessible but has higher complication rates. The brachial artery is an alternative but has less collateral circulation. Allen test can be performed to assess collateral flow before radial artery puncture, though its predictive value is debated. Avoid sites with infection, previous surgery, or inadequate pulses.

Technique for radial artery puncture follows a systematic approach. The wrist is dorsiflexed over a rolled towel to optimize arterial exposure. The radial pulse is palpated two to three centimeters proximal to the wrist crease. The site is cleaned with antiseptic. The needle is inserted at 30 to 45 degrees with the bevel facing up, aiming toward the palpated pulse. Pulsatile blood flow into the syringe confirms arterial access. The heparinized syringe is filled to the required volume. The needle is removed and firm pressure is applied for a minimum of five minutes, longer if the patient is anticoagulated.

Interpretation requires systematic analysis of all values. pH indicates overall acid-base status, with normal range 7.35 to 7.45. PaCO2 indicates the respiratory component, with normal 35 to 45 mmHg. PaO2 indicates oxygenation, with normal 80 to 100 mmHg on room air. Bicarbonate indicates the metabolic component, with normal 22 to 26 mEq/L. Lactate indicates tissue perfusion, with normal less than 2 mmol/L. The A-a gradient helps distinguish pulmonary from non-pulmonary causes of hypoxemia.

Lumbar Puncture

Indications for lumbar puncture include diagnostic and therapeutic purposes. Suspected meningitis requires CSF analysis for cell count, protein, glucose, and culture. Subarachnoid hemorrhage is evaluated by CSF examination for xanthochromia and red blood cells when CT is negative. Encephalitis workup includes CSF viral studies and PCR. Guillain-Barre syndrome shows elevated protein with normal cell count (albuminocytologic dissociation). Idiopathic intracranial hypertension requires opening pressure measurement and may benefit therapeutically from fluid removal.

Contraindications must be assessed before proceeding. Evidence of mass effect on CT including midline shift or effacement of basal cisterns is an absolute contraindication. Skin infection at the puncture site prevents safe access. Hemodynamic instability should be addressed before elective procedures. Relative contraindications include coagulopathy, which may require correction depending on urgency, and thrombocytopenia, with many practitioners requiring platelets above 50,000. Patients on anticoagulation may need reversal. Spinal abnormalities may require alternative approaches or fluoroscopic guidance.

Technique requires careful positioning and landmark identification. The patient is positioned in lateral decubitus with knees pulled to chest to open intervertebral spaces, or in sitting position leaning forward for obese patients. The L3-L4 or L4-L5 interspace is identified at the level of the iliac crests. Sterile preparation includes wide skin prep and sterile draping. Local anesthesia is infiltrated from skin to periosteum. The spinal needle is inserted with stylet in place, bevel oriented toward the patient's side. The needle is advanced until a pop is felt as it passes through the ligamentum flavum and dura. Opening pressure is measured with manometer while the patient extends their legs. Four tubes of CSF are collected, typically one to two milliliters each.

Interpretation of CSF results guides diagnosis. Normal CSF has fewer than 5 white blood cells, protein less than 45 mg/dL, and glucose greater than 60 percent of serum glucose. Bacterial meningitis typically shows greater than 1000 white blood cells with neutrophil predominance, elevated protein greater than 100 mg/dL, and low glucose less than 40 mg/dL. Viral meningitis shows 10 to 500 white blood cells with lymphocyte predominance, mildly elevated protein, and normal glucose. Opening pressure is normally less than 20 cm H2O when measured in lateral decubitus with legs extended.

Paracentesis

Indications for paracentesis include diagnostic and therapeutic purposes. New-onset ascites requires diagnostic paracentesis to determine etiology. Suspected spontaneous bacterial peritonitis requires cell count and culture. Tense ascites causing discomfort or respiratory compromise benefits from large-volume therapeutic drainage. Hepatic hydrothorax may improve with reduction of ascitic volume. All patients with cirrhosis admitted to the hospital should undergo diagnostic paracentesis to evaluate for infection.

Contraindications are relatively few for this generally safe procedure. Coagulopathy is often present in patients with liver disease but is rarely a contraindication unless INR is severely elevated. Platelets above 50,000 are generally adequate. Bowel obstruction increases risk of perforation and may require ultrasound guidance. Skin infection at the planned site requires alternative access. Previous abdominal surgery creates adhesions that may alter anatomy. Pregnancy requires adjusted technique with higher entry points.

Technique emphasizes safety and ultrasound guidance. The patient is positioned supine with slight tilt toward the side of puncture. The left lower quadrant lateral to the rectus muscle is the preferred site to avoid the inferior epigastric vessels. Ultrasound identifies a pocket of fluid and confirms depth. Sterile preparation includes wide skin prep and draping. Local anesthesia is infiltrated to the peritoneum. Z-track technique offsets skin and deep entry points to prevent leakage. The needle is inserted perpendicular to the skin. Aspiration confirms fluid. For diagnostic purposes, 50 to 100 mL is collected. For therapeutic drainage, a catheter system allows larger volumes, typically limited to 5 to 8 liters to prevent circulatory dysfunction.

Analysis of ascitic fluid provides diagnostic information. Cell count with differential is the most critical test, with greater than 250 polymorphonuclear cells indicating spontaneous bacterial peritonitis. Albumin measurement allows calculation of the serum-ascites albumin gradient (SAAG), with greater than 1.1 g/dL indicating portal hypertension. Total protein helps distinguish transudative from exudative ascites. Culture in blood culture bottles improves sensitivity for bacterial detection. Cytology is sent when malignant ascites is suspected. Amylase is checked when pancreatic ascites is considered.

Thoracentesis

Indications for thoracentesis parallel those for paracentesis. New pleural effusion requires diagnostic sampling to determine etiology. Dyspnea from large effusion may improve with therapeutic drainage. Suspected empyema requires sampling for cell count, pH, and culture. Malignant effusion diagnosis requires cytologic examination. The decision to perform thoracentesis balances the diagnostic value against the procedure risk.

Contraindications require assessment before proceeding. Severe coagulopathy increases bleeding risk. Very small effusions may not be safely accessible without ultrasound guidance. Skin infection at the planned site requires alternative access. Mechanical ventilation increases pneumothorax risk but is not an absolute contraindication. Patient inability to cooperate with positioning may require procedural sedation or alternative approach.

Technique emphasizes ultrasound guidance and patient positioning. The patient sits upright leaning forward over a bedside table to maximize fluid accessibility. Ultrasound identifies the effusion, confirms the depth, and marks the optimal entry site. The entry point should be one to two rib spaces below the fluid level, above the ninth rib posteriorly to avoid abdominal organs. The needle enters above the rib to avoid the neurovascular bundle running along the lower rib margin. Sterile preparation and local anesthesia proceed as for other procedures. The needle is advanced while aspirating until fluid is obtained. For therapeutic drainage, volume is typically limited to 1.5 liters to prevent re-expansion pulmonary edema. Post-procedure chest X-ray is obtained if pneumothorax is suspected based on symptoms.

Light's criteria distinguish exudative from transudative effusions. An effusion is exudative if any of the following criteria are met: pleural fluid protein divided by serum protein greater than 0.5, pleural fluid LDH divided by serum LDH greater than 0.6, or pleural fluid LDH greater than two-thirds the upper limit of normal for serum LDH. Meeting any one criterion has sensitivity of 98 percent for exudate. Transudative effusions result from hydrostatic or oncotic pressure imbalances, such as heart failure or cirrhosis. Exudative effusions result from pleural inflammation or impaired lymphatic drainage, such as infection, malignancy, or pulmonary embolism.

Central Line Assistance

The role of the sub-intern during central line placement involves multiple support functions. Preparation includes gathering all equipment from the central line kit, ensuring ultrasound is available and functioning, and preparing the sterile field. Patient positioning optimizes access to the selected site. Sterile field assistance includes helping with draping while maintaining sterility. During the procedure, the assistant hands supplies as requested and retracts when needed. Patient monitoring observes for distress, pain, or respiratory changes. Post-procedure duties include obtaining confirmation chest X-ray and assisting with dressing and documentation.

Understanding anatomy supports safe assistance and prepares for future independent performance. The internal jugular vein lies lateral to the carotid artery within the triangle formed by the two heads of the sternocleidomastoid muscle. The subclavian vein runs below the clavicle and above the first rib. The femoral vein lies medial to the femoral artery below the inguinal ligament. Ultrasound distinguishes veins from arteries: veins compress with pressure while arteries pulsate and resist compression.

Complications of central line placement must be recognized and addressed. Pneumothorax presents with dyspnea, decreased breath sounds on the affected side, and may require chest tube placement. Arterial puncture produces pulsatile, bright red blood and requires extended pressure after needle removal. Hematoma causes visible or palpable swelling at the site. Air embolism presents with sudden dyspnea and hypotension and is prevented by maintaining the patient in Trendelenburg position. Line infection presents with fever and site erythema days after placement. Thrombosis causes extremity swelling and pain.

Post-procedure care ensures safe line use. Chest X-ray confirms appropriate position with the catheter tip at the superior vena cava-right atrial junction. The chest X-ray also rules out pneumothorax for internal jugular and subclavian lines. Sterile dressing is applied and labeled with the date. Documentation includes a complete procedure note. Daily assessment evaluates necessity for continued use and examines the site for signs of infection. Removal occurs as soon as the line is no longer needed to minimize infection risk.

Nasogastric Tube Placement

Indications for nasogastric tube placement span decompression, diagnostic, and nutritional purposes. Bowel obstruction requires gastric decompression to relieve distension and vomiting. Gastrointestinal bleeding evaluation may include gastric lavage to assess for upper source. Medication administration uses NG tubes when oral intake is not possible. Enteral nutrition is delivered via NG tube when short-term feeding is needed. Gastric lavage for certain toxin ingestions may use NG access.

Contraindications relate primarily to facial and esophageal anatomy. Severe facial trauma creates risk of intracranial placement through skull base fractures. Esophageal stricture risks perforation with blind passage. Recent esophageal surgery creates anastomotic disruption risk. Severe coagulopathy increases risk of epistaxis. Altered mental status with unprotected airway increases aspiration risk. These contraindications may be relative depending on clinical urgency.

Technique emphasizes measurement, positioning, and confirmation. Length is measured from nose to ear to xiphoid process and marked on the tube. The tube is lubricated with water-soluble lubricant. The patient is positioned upright with chin tucked to close off the trachea. The tube is inserted along the floor of the nose. As the tube reaches the oropharynx, the patient is asked to swallow while the tube is advanced. Resistance or coughing suggests tracheal placement. The tube is advanced to the premeasured length. Proper position is confirmed before use.

Confirmation of correct placement is essential before use. Chest and abdominal X-ray remains the gold standard, showing the tube crossing the diaphragm and terminating in the stomach. Air insufflation with auscultation over the stomach is unreliable and should not be used as the sole confirmation method. Aspirate pH less than 5 suggests gastric placement but is not definitive. CO2 detection can rule out tracheal placement. Visual inspection of the oropharynx identifies coiled tubes that have not advanced properly.

Procedure Documentation

The procedure note creates a permanent medical and legal record. Procedure identification includes the name and date/time of the procedure. Indication documents why the procedure was performed. Consent documentation notes that informed consent was obtained and from whom. Anesthesia records the type and amount of local anesthetic used. Technique describes the steps performed including sterile preparation, positioning, and approach. Findings document what was seen or obtained. Specimens note what was sent and to which laboratory. Complications are documented as none or with specific description. Patient tolerance notes how the patient handled the procedure.

Complication documentation requires specific attention. The time of recognition establishes when the complication was identified. Actions taken describe the interventions performed in response. Outcome documents the resolution or ongoing management. Patient communication notes that the complication and response were discussed with the patient. Follow-up plan documents ongoing monitoring or treatment. Honest and thorough documentation supports both patient care and medicolegal defense.

Billing and coding ensure appropriate reimbursement for procedures performed. The procedure code (CPT) must accurately reflect the procedure performed. The diagnosis code (ICD-10) must support the medical necessity. Documentation must support the codes submitted. Supervision status notes whether the procedure was independently performed or supervised. Incomplete documentation may result in denied claims or compliance concerns.

Learning from procedures improves future performance. Procedure logs track experience and document progress toward competency. Feedback should be sought from supervisors after each procedure. Complications should be reviewed for learning opportunities. Simulation practice develops skills in a low-risk environment. Video review, when available, allows analysis of technique.

Summary

Procedural preparation requires clear indications, informed consent, and appropriate equipment. Sterile technique must match the invasiveness of the procedure, with full sterile technique for lumbar puncture, paracentesis, and thoracentesis. Venipuncture technique includes proper tourniquet application, site selection, and order of draw to prevent tube contamination. IV placement matches gauge to clinical need, with ultrasound guidance improving success in difficult access patients.

Arterial blood gas requires radial artery access at appropriate angle with extended pressure afterward. Lumbar puncture is contraindicated with mass effect on imaging and requires positioning to open intervertebral spaces. Paracentesis uses the left lower quadrant lateral to the rectus with ultrasound guidance and Z-track technique. Thoracentesis accesses effusions above the rib to avoid neurovascular bundles with volume limits to prevent re-expansion edema.

Central line assistance prepares sub-interns for future independent placement through understanding of anatomy and complications. Complete procedure documentation supports patient care, communication, and billing. Complications require honest documentation and disclosure. Through systematic preparation, proper technique, and continuous learning, procedural skills develop progressively during the sub-internship.

Key Terms

Informed consent: The process by which a patient agrees to a procedure after understanding its risks, benefits, and alternatives, with capacity to make the decision.

Z-track technique: A method of needle insertion where skin and deeper tissue entry points are offset to prevent fluid leakage after the procedure.

SAAG: Serum-ascites albumin gradient, calculated by subtracting ascitic fluid albumin from serum albumin, with values greater than 1.1 g/dL indicating portal hypertension.

Light's criteria: The diagnostic criteria used to distinguish exudative from transudative pleural effusions based on protein and LDH ratios.

SBP: Spontaneous bacterial peritonitis, diagnosed when ascitic fluid contains greater than 250 polymorphonuclear cells per microliter.

Opening pressure: The cerebrospinal fluid pressure measured during lumbar puncture with the patient in lateral decubitus position and legs extended.

Re-expansion pulmonary edema: Pulmonary edema that can occur after rapid re-expansion of a collapsed lung, prevented by limiting thoracentesis volume.

Order of draw: The sequence in which blood collection tubes should be filled to prevent cross-contamination by tube additives.

This content is subject to the MIT License. © 2024–2026 Hibbert School of Medicine.

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