Procedures Commonly Performed by Internists

Internists perform a wide range of medical procedures, although practices vary widely among institutions and by specialty.Internists, nurses, or other ancillary health care professionals perform venipuncture for blood testing, arterial puncture for blood gases, endotracheal intubation, and flexible sigmoidoscopy, and insert IV Lines, nasogastric (NG) tubes, and urinary catheters.These procedures are not covered here but require skill and practice to minimize patient discomfort and potential complications.Here, we review more invasive diagnostic and therapeutic procedures performed by internists—thoracentesis, lumbar puncture, and paracentesis.Many additional procedures are performed by specialists and require additional training and credentialing, including the following:

• Allergy—skin testing, rhinoscopy • Cardiology—stress testing, echocardiograms, coronary catheterization, angioplasty, stent insertion, pacemakers, electrophysiology testing and ablation, implantable defibrillators, cardioversion

• Endocrinology—thyroid biopsy, dynamic hormone testing, bone densitometry

• Gastroenterology—upper and lower endoscopy, esophageal manometry, endoscopic retrograde cholangiopancreatography, stent insertion, endoscopic ultrasound, liver biopsy

• Hematology/Oncology—bone marrow biopsy, stem cell transplant, lymph node biopsy, plasmapheresis

• Pulmonary—intubation and ventilator management, bronchoscopy

• Renal—kidney biopsy, dialysis

• Rheumatology—joint aspiration Increasingly, ultrasound, CT, and MRI are being used to guide invasive procedures, and flexible fiberoptic instruments are extending the reach into the body.For most invasive medical procedures, including those reviewed below, informed consent should be obtained in writing before beginning the procedure. 

THORACENTESIS

Drainage of the pleural space can be performed at the bedside.Indications for this procedure include diagnostic evaluation of pleural fluid, removal of pleural fluid for symptomatic relief, and instillation of sclerosing agents in pts with recurrent, usually malignant pleural effusions.

PREPARATORY WORK

Familiarity with the components of a thoracentesis tray is a prerequisite to performing a thoracentesis successfully.Current PA and lateral chest radiographs with bilateral decubitus views should be obtained to document the free-flowing nature of the pleural effusion.Loculated pleural effusions should be localized by ultrasound or CT prior to drainage.

TECHNIQUE

A posterior approach is the preferred means of accessing pleural fluid.Comfortable positioning is a key to success for both pt and physician. The pt should sit on the edge of the bed, leaning forward with the arms abducted onto a pillow on a bedside stand.Pts undergoing thoracentesis frequently have severe dyspnea, and it is important to assess if they can maintain this positioning for at least 10 min.The entry site for the thoracentesis is based on the physical exam and radiographic findings.Percussion of dullness is utilized to ascertain the extent of the pleural effusion with the site of entry being the first or second highest interspace in this area.

The entry site for the thoracentesis is at the superior aspect of the rib, thus avoiding the intercostal nerve, artery, and vein, which run along the inferior aspect of the rib. The site of entry should be marked with a pen to guide the thoracentesis. The skin is then prepped and draped in a sterile fashion with the operator observing sterile technique at all times.A small-gauge needle is used to anesthetize the skin and a larger-gauge needle is used to anesthetize down to the superior aspect of the rib.The needle should then be directed over the upper margin of the rib to anesthetize down to the parietal pleura.The pleural space should be entered with the anesthetizing needle, all the while using liberal amounts of lidocaine.  A dedicated thoracentesis needle with an attached syringe should next be utilized to penetrate the skin.This needle should be advanced to the superior aspect of the rib.While maintaining gentle negative pressure, the needle should be slowly advanced into the pleural space.

If a diagnostic tap is being performed, aspiration of only 30–50 mL of fluid is necessary before termination of the procedure.If a therapeutic thoracentesis is being performed, a three-way stopcock is utilized to direct the aspirated pleural fluid into collection bottles or bags.No more than 1 L of pleural fluid should be withdrawn at any given time as quantities _1–1.5 L can result in reexpansion pulmonary edema. After all specimens have been collected, the thoracentesis needle should be withdrawn and the needle site occluded for at least 1 min.

SPECIMEN COLLECTION

The diagnostic evaluation of pleural fluid depends on the clinical situation.All pleural fluid samples should be sent for cell count and differential, Gram stain, and bacterial cultures.LDH and protein determinations should also be made to differentiate between exudative and transudative pleural effusions.The pH should be determined if empyema is a diagnostic consideration.Other studies on pleural fluid include mycobacterial and fungal cultures, glucose, triglyceride level, amylase, and cytologic determination. 

POST-PROCEDURE

A post-procedural chest radiograph should be obtained to evaluate for a pneumothorax, and the pt should be instructed to notify the physician if new shortness of breath develops. 

LUMBAR PUNCTURE

Evaluation of CSF is essential for the diagnosis of suspected meningeal infection, subarachnoid hemorrhage, leptomeningeal neoplastic disease, and noninfectious meningitis.Relative contraindications to LP include local skin infection in the lumbar area, suspected spinal cord mass lesion, and a suspected intracranial mass lesion.Any bleeding diathesis should also be corrected prior to performing LP to prevent the possible occurrence of an epidural hematoma.A functional platelet count _ 50,000/_L and an INR _ 1.5 are advisable to perform LP safely. 

PREPARATORY WORK

Familiarity with the components of a lumbar puncture tray is a prerequisite to performing LP successfully.In pts with focal  neurologic deficits or with evidence of papilledema on physical exam, a CT scan of the head should be obtained prior to performing LP. 

TECHNIQUE

Proper positioning of the pt is important to ensure a successful LP.Two different pt positions can be used: the lateral decubitus position and the sitting position.Most routine LPs should be performed using the lateral decubitus position.The sitting position may be preferable in obese pts. With either position, the pt should be instructed to flex the spine as much as possible. In the lateral decubitus position, the pt is instructed to assume the fetal position with the knees flexed toward the abdomen.In the sitting position, the pt should bend over a bedside table with the head resting on folded arms.

The entry site for a LP is below the level of the conus medullaris, which extends to L1-L2 in most adults.Thus, either the L3-L4 or L4-L5 interspace can be utilized as the entry site.The posterior superior iliac crest should be identified and the spine palpated at this level.This represents the L3-L4 interspace, with the other interspaces referenced from this landmark.The midpoint of the interspace between the spinous processes represents the entry point for the thoracentesis needle.This entry site should be marked with a pen to guide the LP.The skin is then prepped and draped in a sterile fashion with the operator observing sterile technique at all times.A small-gauge needle is then used to anesthetize the skin and subcutaneous tissue.The spinal needle should be introduced perpendicular to the skin in the midline and should be advanced slowly.The needle stylette should be withdrawn frequently as the spinal needle is advanced.As the needle enters the subarachnoid space, a “popping” sensation can sometimes be felt.If bone is encountered, the needle should be withdrawn to just below the skin and then redirected more caudally.Once CSF begins to flow, the opening pressure can be measured.This should be measured in the lateral decubitus position with the pt shifted to this position if the procedure was begun with the pt in the sitting position.After the opening pressure is measured, the CSF should be collected in a series of specimen tubes for various tests.At a minimum, a total of 10–15 mL of CSF should be collected in the different specimen tubes.  Once the required spinal fluid is collected, the stylette should be replaced and the spinal needle removed. 

SPECIMEN COLLECTION

Diagnostic evaluation of CSF is based on the clinical scenario.In general, spinal fluid should always be sent for cell count with differential, protein, glucose, and bacterial cultures.Other specialized studies that can be obtained on CSF include viral cultures, fungal and mycobacterial cultures, VDRL, cryptococcal antigen, oligoclonal bands, and cytology. 

POST-PROCEDURE

To reduce the chance of a post-LP headache, the pt should be instructed to lie prone for at least 3 h.If a headache does develop; bedrest, hydration, and oral analgesics are often helpful.If an intractable post- LP headache ensues, the pt may have a persistent CSF leak.In this case, consultation of an anesthesiologist should be considered for the placement of a blood patch. 

PARACENTESIS

Removal and analysis of peritoneal fluid is invaluable in evaluating pts with new-onset ascites or ascites of unknown etiology.It is also requisite in pts with known ascites who have a decompensation in their clinical status.Relative contraindications include bleeding diathesis, prior abdominal surgery, distended bowel, or known loculated ascites. 

PREPARATORY WORK

Prior to performing a paracentesis, any severe bleeding diathesis should be corrected.Bowel distention should also be relieved by placement of a nasogastric tube, and the bladder should also be emptied before beginning the procedure.If a large-volume paracentesis is being performed, large vacuum bottles with the appropriate connecting tubing should be obtained. 

TECHNIQUE

Proper pt positioning greatly improves the ease with which a paracentesis can be performed.The pt should be instructed to lie supine with the head of the bed elevated to 45_.This position should be maintained for _15 min to allow ascitic fluid to accumulate in the dependent portion of the abdomen. The preferred entry site for paracentesis is a midline puncture halfway between the pubic symphysis and the umbilicus; this correlates with the location of the relatively avascular linea alba.The midline puncture should be avoided if there is a previous midline surgical scar, as neovascularization may have occurred.

Alternative sites of entry include the lower quadrants, lateral to the rectus abdominus, but caution should be used to avoid collateral blood vessels that may have formed in patients with portal hypertension. The skin is prepped and draped in a sterile fashion.The skin, subcutaneous tissue, and the abdominal wall down to the peritoneum should be infiltrated with an anesthetic agent.The paracentesis needle with an attached syringe is then introduced in the midline perpendicular to the skin.To prevent leaking of ascitic fluid, “Z-tracking” can sometimes be helpful: after penetrating the skin, the needle is inserted 1–2 cm before advancing further.The needle is then advanced slowly while continuous aspiration is performed.As the peritoneum is pierced, the needle will give noticeably.Fluid should flow freely into the syringe soon thereafter.For a diagnostic paracentesis, removal of 50 mL of ascitic fluid is adequate.For a large-volume paracentesis, direct drainage into large vacuum containers using connecting tubing is a commonly utilized option. After all samples have been collected, the paracentesis needle should be removed and firm pressure applied to the puncture site. 

SPECIMEN COLLECTION

Peritoneal fluid should be sent for cell count with differential, Gram stain, and bacterial cultures.Albumin measurement of ascitic fluid is also necessary for calculating the serum–ascitic albumin gradient.Depending on the clinical scenario, other studies that can be obtained include mycobacterial cultures, amylase, adenosine deaminase, triglycerides, and cytology.  

POST-PROCEDURE The pt should be monitored carefully post-procedure and should be instructed to lie supine in bed for several hours.If persistent fluid leakage occurs, continued bedrest with pressure dressings at the puncture site can be helpful.For pts with hepatic dysfunction undergoing large-volume paracentesis, the sudden reduction in intravascular volume can precipitate hepatorenal syndrome.Administration of 25 g IV albumin following large-volume paracentesis has been shown to decrease the incidence of renal failure postprocedure.  Finally, if the ascites fluid analysis shows evidence of spontaneous bacterial peritonitis, then antibiotics (directed toward gram-negative gut bacteria) and IV albumin should be administered as soon as possible.