Icp Monitoring

Parenchymal Devices

ICP monitors can be placed early in the care of severe TBI with relatively low risk. Generally, the upper threshold for treatment of intracranial hypertension is 20-25 mmHg. Pressure transducers are commercially available in sterile packages and can be inserted to determine ICP rapidly.

With the patient supine, the head is raised to approx 30° The preferred insertion site is the right frontal cortex at Kocher's point: 1-2 cm anterior to the coronal suture, which can be palpated, and 2-3 cm off the midline (24). However, the surgeon may choose to insert on the left side or in a slightly removed site in effort to avoid areas of contusion or craniotomy flaps. The hair is shaved, and the site of insertion is marked. The skin is cleaned with a combination of alcohol and povidone-iodine. The area is draped with sterile towels and drape. After the injection of local anesthesia, a stab incision is made with a #11 scalpel. In the Camino monitoring kit (Integra NeuroSciences), a drill bit is provided that has an adjustable safety stop. A hex wrench is used to set the safety stop approx 5 mm clear from the thread on the bit. The drill bit is then fastened to a twist drill and a hole is made carefully through the skull and across the inner table (Fig. 1A). After drilling, the Camino bolt is screwed completely into the hole (Fig. 1B). A stylet is then inserted into the bolt for the purpose of piercing the dura. After this step, cerebrospinal fluid (CSF) may exit through the bolt opening (Fig. 1C).

To zero the monitor, the transducer connecter is attached to the monitor's preamp connector. Either the surgeon or the assistant, while preserving sterile boundaries, then calibrates the monitor using the provided screwdriver so that atmospheric pressure registers as zero. The pressure transducer is then inserted into the bolt to approx the 5-cm mark (Fig. 1D), which allows the tip to be 5 mm beyond the end of the bolt in the subarachnoid space. A waveform should be confirmed on the monitor with an ICP value. The transducer is then secured in place by tightening the compression cap on top of the bolt. A strain relief sheath slides down over the transducer catheter and is secured on the compression cap (Fig. 1E). Dressing for the bolt is gauze wrapped around the area of insertion and soaked with povidone-iodine solution.

External Ventricular Drainage

In the treatment of severe TBI, an intraventricular catheter (IVC) or external ventriculostomy is a treatment modality for intracranial hypertension. The advantage to this device is that it can transduce ICP readings while therapeutically lowering ICP with the external drainage of CSF. Additional risks include ventriculostomy-related CSF infection and intraparenchymal hemorrhage (25).

The standard insertion site is Kocher's point in the right frontal lobe, which is 1-2 cm anterior to the coronal suture and 2-3 cm off the midline, or the mid-pupillary line. However, the ventriculostomy can be made on the left side depending on the presence of underlying subarachnoid hemorrhage, intra-parenchymal hemorrhage, or intraventricular hemorrhage or depending on the

Integra Ventriculostomy

Fig. 1. Insertion of the Camino (Integra NeuroSciences) ICP monitor. The drill bit safety stop is adjusted and fitted to a twist drill. (A) A hole is carefully made through the skull. (B) The bolt is screwed into the hole. (C) The stylet is advanced to the first marking to pierce the dura. (D) The transducer is inserted to the 5-cm mark. (E) After screwing the compression cap, the sheath slides over the catheter and is secured.

Fig. 1. Insertion of the Camino (Integra NeuroSciences) ICP monitor. The drill bit safety stop is adjusted and fitted to a twist drill. (A) A hole is carefully made through the skull. (B) The bolt is screwed into the hole. (C) The stylet is advanced to the first marking to pierce the dura. (D) The transducer is inserted to the 5-cm mark. (E) After screwing the compression cap, the sheath slides over the catheter and is secured.

characteristics of the lateral ventricle on imaging studies. Often severe TBI results in slit ventricles from edema, which may be more severe on one side than the other.

With the patient supine, the hair is shaved, and the site of insertion is marked. The skin is cleaned with a combination of alcohol and povidone-iodine. The area is draped in sterile fashion. After the injection of local anesthetic, a 3-cm linear incision is made over the planned site of insertion. After self-retaining retraction, the periosteum is cleared with an elevator. The coronal suture should then be visible. With a twist drill, a hole is made through the skull 1-2 cm anterior to the suture (Fig. 2A). Bone at the inner table can be cleared with a curet.

The dura is then incised with a cruciate incision. The intraventricular catheter, along with the inner stylet, is inserted through this hole in a direction that is orthogonal to the plane of the skull (Fig. 2B). This angle can be approximated by aiming toward the ipsilateral medial canthus in the coronal plane and toward the ipsilateral tragus of the ear in the sagittal plane. The Ghajar guide was developed to direct the catheter in the orthogonal plane if this angle cannot be determined visually (26,27). Both CT-guided (28) and ultrasound-guided (29) techniques have been proposed to assist in tapping the ventricular system.

The target for the catheter tip is in the frontal horn of the lateral ventricle above the intraventricular foramen of Monroe. The catheter with a stylet should be inserted from 4 to 5 cm in an adult. A change in resistance should be felt when the catheter tip enters the ventricle. When CSF rises through the column of the catheter, the stylet is removed. The surgeon may advance the catheter an additional centimeter while ensuring the continual flow of CSF. A trocar is attached to the end of the catheter, and it is tunneled in the subgaleal space to an exit point about 3-5 cm away from the incision. With the trocar still under the skin, a tunnel stitch may be passed around the trocar using a curved needle (Fig. 2C). Once the trocar is pulled out of the scalp, this stitch can be tied to reduce the risk of CSF leak around the subgaleal catheter. The catheter can then be secured to the skin at the exit site using a pursestring stitch.

The catheter is connected to a three-way stopcock. One port is connected to a drainage bag, and the other is connected a pressure transducer (Fig. 2D). Either the tubing to the transducer is filled with sterile preservative-free saline, or the column is allowed to fill with CSF. Once the transducer is attached to a pressure monitor, a waveform and ICP value can be confirmed. The skin is closed and sterile dressing is applied. The stopcock can be turned so that the transducer directly reads the ICP from the catheter. If the stopcock is turned so that all three ports are open, there is continuous drainage into the bag, which is raised to a set level relative to the patient's ear. Note that an accurate ICP reading is reflected only while the stopcock is turned off to the drainage bag.

Epidural, Subarachnoid, and Subdural Devices

Intracranial pressure can also be monitored by implanting devices in the epidural space (Ladd monitor), the subdural space, or the subarachnoid region

How Level Subdural Drain

Fig. 2. Insertion of an intraventricular catheter (IVC). (A) A twist drill is used to make a burr hole. (B) While feeling for facial landmarks with one hand, the surgeon uses the other hand to pass the catheter in a direction that is orthogonal to the plane of the skull at the burr hole. (C) While the catheter trocar still lies in the subgaleal space, a suture is passed around it. This suture is then tied around the catheter to reduce the risk of CSF leakage. (D) A three-way stopcock connects the IVC (left), drainage bag (right), and fluid-filled pressure transducer (above).

Fig. 2. Insertion of an intraventricular catheter (IVC). (A) A twist drill is used to make a burr hole. (B) While feeling for facial landmarks with one hand, the surgeon uses the other hand to pass the catheter in a direction that is orthogonal to the plane of the skull at the burr hole. (C) While the catheter trocar still lies in the subgaleal space, a suture is passed around it. This suture is then tied around the catheter to reduce the risk of CSF leakage. (D) A three-way stopcock connects the IVC (left), drainage bag (right), and fluid-filled pressure transducer (above).

(Richmond screw). The main advantage of these devices is that they are less invasive and are less likely to cause postoperative infection. Epidural drains are especially worthwhile in patients with coagulopathies. These devices tend to overexpress the intracranial pressure and may drift frequently. To place the Ladd monitor one places a burr hole near the coronal suture and 3-5 cm off the midline, dissects the dura, and places the pneumatic device in the epidural space. To place the Richmond screw, a twist drill is placed in that region, the dura is opened, and the screw is fixed in the skull, producing a fluid column connecting to the subarachnoid space. This fluid column is connected to a pressure sensor followed by calibration (Fig. 3).

Fluid Filled Gauges

Fig. 3. (A) Richmond bolt fixed into the skull with opened dura in order to monitor intracranial pressure through a fluid filled tube connected to a strain gauge sensor. (B) Epidural sensor (pneumatic) placed over the dura and connected a box for calibration of a pneumatic device such as Ladd Monitor.

Fig. 3. (A) Richmond bolt fixed into the skull with opened dura in order to monitor intracranial pressure through a fluid filled tube connected to a strain gauge sensor. (B) Epidural sensor (pneumatic) placed over the dura and connected a box for calibration of a pneumatic device such as Ladd Monitor.

Blood Pressure Health

Blood Pressure Health

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