Laparoscopic surgery in a patient with ventriculoperitoneal shunt: monitoring of shunt function with transcranial Doppler

J. Ravaoherisoa1, P. Meyer*,3, R. Afriat2, Y. Meyer1, E. Sauvanet2, A. Tricot1 and P. Carli3

1 Department of Anaesthesiology and 2 Department of Surgical Gynaecology and Obstetrics, Hôpital Notre Dame de Bon Secours, Paris, France. 3 Department of Anaesthesiology, Centre Hospitalier Universitaire Necker Enfants-Malades, Université Paris 5, Paris, France

*Corresponding author. E-mail: philippe.meyer@nck.ap-hop-paris.fr

Accepted for publication: September 4, 2003


    Abstract
 Top
 Abstract
 Introduction
 Case report
 Discussion
 References
 
We describe the use of transcranial Doppler (TCD) monitoring during laparoscopic resection of an ovarian cyst in a young woman who previously underwent ventriculoperitoneal shunting for hydrocephalus. Shunt function was not altered by pneumoperitoneum, except during transient episodes of high intra-abdominal pressure. The role of TCD monitoring during laparoscopic procedures in patients with cerebrospinal fluid shunt is discussed.

Br J Anaesth 2004; 92: 434–7

Keywords: brain, intracranial pressure; measurement techniques, transcranial Doppler; surgery, laparoscopy; surgery, ventriculoperitoneal shunt


    Introduction
 Top
 Abstract
 Introduction
 Case report
 Discussion
 References
 
Because of the concomitant development of laparoscopic surgery, and the progress made in surgical treatment of hydrocephalus, surgeons can expect to encounter some patients who have previously undergone placement of a cerebrospinal fluid (CSF) shunt, and who present as candidates for laparoscopic procedures. Although CSF shunt is not formally considered a contraindication for laparoscopic surgery, pneumoperitoneum is described as a cause of raised intracranial pressure.1 2 Shunt failure has been reported in patients with CSF shunting undergoing laparoscopic surgery,3 and invasive monitoring and temporary exteriorization of shunts have been proposed in order to avoid complications.1 We describe the use of a non-invasive method, namely transcranial Doppler (TCD), to monitor shunt function during laparoscopy.


    Case report
 Top
 Abstract
 Introduction
 Case report
 Discussion
 References
 
A 36-yr-old woman was undergoing laparoscopic resection of an ovarian cyst. Her previous medical history was remarkable for myelomeningocele and Arnold–Chiari type II malformation requiring multiple surgical procedures in infancy and childhood. She had CSF shunt placement for hydrocephalus in early infancy, and needed shunt replacement with a Cordis–Hakim M shunt in 1980. She was alert and independent and experienced pelvic pain that was related to a large left ovarian cyst demonstrated on abdominal ultrasonographic examination. Baseline preoperative TCD examination was performed with a 2 mHz Doppler probe (Waki 1-TC, Atys Médical, France). TCD variations (systolic and diastolic blood flow velocities), Gösling Pulsatility index (PI=systolic – diastolic/mean velocity), and Pourcelot Resistivity index (RI=systolic – diastolic/systolic velocity) were then recorded every 3 min during the procedure and are presented in Figures 1 and 2. Preoperative examination depicted normal bilateral middle cerebral artery blood flow velocities and low pulsatility (PI) and resistivity (RI) indices indicating normal shunt function (Fig. 3). After instituting standard monitoring (ECG, automated arterial pressure monitoring, pulse oximetry), anaesthesia was induced with i.v. propofol (150 mg), sufentanil (10 µg), and atracurium (30mg). The trachea was intubated and mechanical ventilation (O2 50% in air) was instituted with end-tidal carbon dioxide maintained at 35 mm Hg. A continuous infusion of sodium chloride 0.9% solution (2 ml kg–1 h–1) was used for basal fluid maintenance. Anaesthesia induction resulted in transient mild reduction in mean arterial pressure and concomitant cerebral blood flow decrease. Mean arterial pressure, cardiac rhythm, end tidal carbon dioxide, and peripheral oxygen saturation remained constant thereafter without additional intervention. Anaesthesia was maintained with a continuous infusion of propofol (300 mg h–1) and sufentanil, and i.v. cefamandol 1.5 g was injected. The patient was placed in a 15° head-down position and a Palmer needle was introduced through a short para-umbilical incision and connected to a regulated carbon dioxide gas insufflator to create a pneumoperitoneum. The intra-abdominal pressure was monitored continuously and remained less than 12 mm Hg, except when instruments were introduced through the abdominal wall (Fig. 2). At the beginning of the surgical procedure, the distal extremity of the ventriculoperitoneal catheter was isolated and free CSF drainage was demonstrated. The surgical procedure lasted 50 min and consisted of surgical excision of a left ovarian cyst, and division of peritoneal adhesions. The blood flow velocity, PI and RI remained constant except when intra-abdominal pressure increased to 30 mm Hg during introduction of instruments through the abdominal wall (Fig. 3). A slight progressive decrease in diastolic velocity and increase in PI were noted after 30 min of pneumoperitoneum, but resolved quickly when the abdominal pressure was reduced to 10 mm Hg. During acute variations in blood flow velocities there was no associated variations in arterial pressure, airway pressure, EE'CO2 or SpO2 that could be detected. At the end of the surgical procedure, free CSF drainage through the ventriculoperitoneal shunt was verified and ropivacaine 0.75% 20 ml was injected before pneumoperitoneum exsufflation. The patient’s recovery was uneventful, and postoperative TCD examination was comparable with the preoperative examination. The patient was discharged home on the following day.



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Fig 1 Variations of arterial pressure, abdominal pressure and blood flow velocities during the procedure.

 


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Fig 2 Variations of pulsatility and resistivity indexes during laparoscopy.

 


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Fig 3 Variations of DTC during laparocopy. (Top) Baseline examination before anaesthesia. (Bottom) Maximal intra-abdominal pressure (30 mm Hg). Decreased diastolic velocity, increased IP and IR.

 

    Discussion
 Top
 Abstract
 Introduction
 Case report
 Discussion
 References
 
We used TCD as a non-invasive method to evaluate the impact of pneumoperitoneum on CSF shunt function and cerebral blood flow velocity during laparoscopy. We demonstrated that abruptly increased abdominal pressure and long lasting pneumoperitoneum could affect shunt function and intracranial pressure (ICP), but that low-pressure pneumoperitoneum did not induce deleterious effects.

There is still controversy regarding the safety of performing laparoscopic surgery in patients with ventriculoperitoneal shunt and potentially decreased cerebral compliance. In previous studies using minimal monitoring of CSF shunt function limited to clinical observation, laparoscopic procedures were reported as safe and efficient in patients with CSF shunts.47 However, animal studies have demonstrated that increased intra-abdominal pressure with gas insufflation and Trendelenburg position could induce a linear increase in ICP reaching 150% over control values with intra-abdominal pressures above 16 mm Hg.8 The main advocated mechanisms for increased ICP in the presence of pneumoperitoneum, were increased intra-thoracic pressure,2 8 and impaired venous drainage of the lumbar venous plexus,9 rather than increased arterial carbon dioxide because of systemic carbon dioxide diffusion.10 In patients with acutely increased ICP, as a result of head injury or space occupying lesions, peritoneal insufflation could induce abrupt intracranial hypertension and should probably be used with special caution and close monitoring.11

Laparoscopy has become the preferred method for surgical treatment of large symptomatic ovarian cysts in young women, because it represents a minimally invasive method with a reduced risk of secondary peritoneal adhesions. The major concerns in patients with CSF shunt, as candidates for laparoscopic procedures, are the presence of peritoneal adhesions related to previous abdominal interventions reducing vision during laparoscopy, and the risks of acute shunt dysfunction during peritoneal insufflation, shunt occlusion by soft tissue impaction, infection, and to a less extent retrograde carbon dioxide diffusion through the distal catheter. Clinical symptoms that could be related to increased ICP such as nausea and headache have been reported after laparoscopy.12 Postoperative shunt failure, related to impaction of soft tissue within the distal catheter, requiring emergency shunt revision,3 and rapid and sustained increase in ICP in children undergoing urologic laparoscopic procedures have been reported.1 Perioperative invasive ICP monitoring that carries a significant risk of complications, and transient externalization of the distal catheter have been proposed to avoid these complications.1 3

TCD has been validated as a method for evaluating the efficiency of shunt placement in children with hydrocephalus.13 14 Large proximal cerebral arteries have little variation in their diameter compared with arteries from the cerebral microcirculation that are most sensitive to arterial pressure, carbon dioxide, and oxygen variations. That is probably why the main variations of velocity in the middle cerebral artery (MCA) are first noted in the diastolic component of TCD measurements and are related to increased ICP. Although TCD is an indirect measure of cerebral blood flow (CBF=blood velocity; r2, where r is the vessel radius), it approximates it adequately, provided that r2 remains constant in the MCA. A clear correlation between raised ICP and decreased diastolic velocity and increased PI has been demonstrated, making TCD a valuable method for evaluating ICP.15 We contend that TCD could be a valuable, easy to use, and non-invasive alternative to perioperative ICP monitoring in these cases provided that external factors influencing CBF velocity could be limited. Potential factors influencing cerebral arterial diameter such as acute variations in blood viscosity and arterial oxygen content are unlikely to occur during procedures such as the one described here. Acute variations in arterial pressure induce concomitant decreases in systolic and diastolic blood flow velocity with constant pulsatility and resistivity indexes. This kind of variation was only noted at induction of anaesthesia where a mild and transient drop in arterial pressure was associated with decreased diastolic and systolic velocities without significant alteration in pulsatility index. Finally, increased abdominal pressure related to insufflation could increase central venous pressure (CVP) and result in increased CSF pressure. In these circumstances, if a pressure regulated shunt remains functional, drainage through the shunt will increase, resulting in unchanged ICP.

We think, as others, that laparoscopic procedures can be used safely in patients with CSF shunts. Patients with hydrocephalus, in whom the CSF shunt is functioning adequately, should have normal baseline ICP. Shunts with regulated opening pressure allow CSF drainage when intraventricular pressure reaches a pre-set threshold value (10 cm H2O for the Cordis–Hakim shunt) and prevent back-flow within the distal catheter. The first simple method for surgeons to avoid unexpected postoperative shunt failure is to check, at the beginning, during, and after completion of laparoscopy, free CSF drainage from the distal extremity of the catheter. As animal studies have demonstrated that increased ICP is linearly related to increased abdominal pressure, the second rule should be to use the lowest pressure for the pneumoperitoneum and the shortest duration of insufflation necessary to ensure good surgical conditions. In our patient, a 15° Trendelenburg position and initial insufflation to 10 mm Hg did not induce variations in cerebral blood flow. However, an abrupt decrease in diastolic pressure and increase in PI indicating raised ICP were noted when the abdominal pressure reached 30 mm Hg during instrument insertion. Additionally, a progressive increase in PI and decrease in diastolic velocity was noted after 30 min of pneumoperitoneum when the abdominal pressure was near 15 mm Hg, and resolved rapidly when the intra-abdominal pressure was decreased to 10 mm Hg.

Although TCD could not reflect directly ICP, this observation demonstrates that short lasting laparoscoic procedures with low-pressure insufflation, and moderate Trendelenburg do not affect shunt function. However, an abdominal pressure in excess of 15 mm Hg carries a risk of shunt dysfunction with resulting increased ICP in patients with decreased cerebral compliance. Patients with shunted hydrocephalus could be considered as candidates for laparoscopic procedures provided that low insufflation pressure could be used, and that monitoring of shunt function could be provided. Because TCD could detect minimal variations in cerebral haemodynamics, it could be a valuable monitor in these patients precluding the need for invasive ICP monitoring through direct shunt puncture.


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 Introduction
 Case report
 Discussion
 References
 
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